1101 Flashcards
(415 cards)
1
Q
• The power source when unplugged
– May be easily replaced or require a tear down
– Five minutes vs. one hour
• Lithium-Ion (Li-ion) and
– Lithium-Ion polymer (LiPo) are common
– No “memory effect”
– Charging the battery diminishes capacity
• Different form factor for each laptop
– Battery types and styles can vary
– Battery technology is changing constantly
A
Laptop batteries
2
Q
• The most-used component of the laptop – Can be easy to replace – A few screws and a single ribbon cable – May not always be this simple • Or connect an external USB keyboard – Not very portable, but works in a pinch
A
Laptop keyboard
3
Q
• Some repairs might require the removal or
replacement of a key cap
– This can be a delicate procedure
• Check with the manufacturer’s instructions
– It’s very easy to accidentally break the key cap
or the components underneath
A
Laptop keys
4
Q
• Small Outline Dual In-line Memory Module (SO-DIMM)
• Memory used in laptops and mobile devices
– Often easy to install and replace
• Some laptop memory is soldered to the system board
– No upgrade available
– Requires a full system board replacement
A
Laptop memory
5
Q
• Magnetic disk
– Traditional spinning drive platters
– 2.5 form factors (3.5 inch for desktops)
A
Laptop storage
6
Q
– All memory, no moving parts
– Silent, fast access time, less latency
– 2.5 inch form factors
A
SSD (Solid-state drive)
7
Q
– Smaller form factor
– No SATA data or power cables
– Easy to install and replace
A
M.2
8
Q
• All internal – Open a cover on the back – Open the entire laptop • Can be very modular – Two screws and the drive slides out • M.2 drives are even easier – One screw - similar to RAM installation
A
Replacing laptop storage
9
Q
• An impressive upgrade – Move from spinning mechanical drive to solid state memory – It’s almost like getting a new laptop • Install an OS on the SSD – Move user documents between drives – Install any required applications – Can be time consuming • Image/clone the HDD – No OS installation required – Move everything from one to the other • Imaging software needed – Sometimes included with the SSD – Many commercial and open source options • Create an image file - One drive at a time • Drive-to-drive image – Image directly from one drive to the other
A
Migrating from HDD to SSD
10
Q
Wireless network connectivity – Connect without wires • 802.11 – Local area network (LAN) – High speed, Internet access • Bluetooth – Personal area network (PAN) - Short range – Connect peripherals and other nearby devices
A
802.11 wireless and Bluetooth
11
Q
• Sign in or unlock your laptop with a
fingerprint reader or face recognition
– Something you are
• Requires additional configuration in the OS
– Hardware required for most options
• Relatively secure
– Faces and fingerprints are quite unique
A
Biometrics
12
Q
• Short-distance networking
– 4 centimeters or less
– Data transfers or authentication
• Common on mobile phones and smart watches
– Payment method on your wrist
• Use it for authentication without typing a password
– Hospital workstations, warehouses, manufacturing
A
Near-field communication (NFC)
13
Q
• Liquid crystal display – Light shines through liquid crystals • Advantages – Lightweight – Relatively low power – Relatively inexpensive • Disadvantages – Black levels are a challenge – Requires separate backlight – Florescent, LED, etc. – Lights are difficult to replace
A
Portable LCD
14
Q
• TN (Twisted Nematic) LCD – The original LCD technology – Fast response times (gaming!) – Poor viewing angles - color shifts • IPS (In Plane Switching) LCD – Excellent color representation – More expensive to produce than TN • VA (Vertical Alignment) LCD – A good compromise between TN and IPS – Good color representation – Slower response times than TN
A
LCD technologies
15
Q
• Organic Light Emitting Diode – Organic compound emits light when receiving an electric current • Thinner and lighter – Flexible and mobile - no glass needed • No backlight – The organic compound provides the light • Tablets, phones, smart watches – Very accurate color representation – A bit higher cost than LCD
A
OLED
16
Q
• Multiple antennas
– WiFi main and aux / Bluetooth
• Antenna wires wrap around the laptop screen
– It’s up high!
A
Wi-Fi antennas
17
Q
• Video capture - Built-in camera and microphone
• Usually includes both audio and video
– Specialized drivers and software
A
Webcam
18
Q
• Built-in to the laptop display
– Useful for video calls
• Not good for non-casual use
– Analog or USB microphones can help
A
Microphone
19
Q
– Backlight is LEDs instead of florescent
– LEDs around the edge of the screen
– An array of LEDs behind the screen
– The latest laptops are LED-backlit
A
LED backlighting
20
Q
CCFL - Cold Cathode – Fluorescent Lamp – Higher voltage and power needed – Added thickness to the display – No longer a common backlight – Older laptops will use these
A
Fluorescent
21
Q
LCD displays need a backlight
– Florescent lamp/LED to LCD display to your eyes
• Some laptops have inverters - Turn DC into AC
• Verify backlight
– Look closely and use a flashlight
• May need to replace the LCD inverter or display
– Choose carefully
A
Backlight and inverter
22
Q
Use a pen-like device as input
– Stylus input - Useful for graphical input
• Used commonly on laptop / tablets
– Or hybrid devices
A
Digitizer
23
Q
• Merge laptop and tablet input
– Digitizer responds to touch - No keyboard required
• But often still available
– Many options for input - Use the best one for the job
A
Touchscreen
24
Q
• Universal Serial Bus – High-speed wired communication – Used for charging and data transfers • Micro-USB – A smaller USB connection – Common now worldwide • Older devices may use Mini-USB – Slightly larger
A
USB
25
```
• 24-pin double-sided USB connector
– Used for both hosts and devices
• Acts as a USB 2.0/3.0/3.1/4 connection
– Different signals can use the same connector
• Can transmit other signals
– DisplayPort, HDMI, Thunderbolt
```
USB-C
26
```
• Apple proprietary
– 8-pin digital signals
– iPhone and iPad devices
• Some advantages over Micro-USB
– Higher power output for phones and tablets
– Can be inserted either way
– Simpler design
```
Lightning
27
```
• DB-9 - also called DE-9
• Commonly used for RS-232 signals
– Recommended Standard 232
– An industry standard since 1969
• Serial communications standard
– Traditionally used for modem connections
• Now used as a configuration port
– Switches, routers, firewalls, etc
– Use a USB to DB-9 converter cable
```
Serial interfaces
28
```
– Send small amounts of data wirelessly
over a limited area
• Built into your phone
– Payment systems, transportation,in-person
information exchange
• Access token, identity “card”
– Short range with encryption support
```
NFC
29
```
• High speed communication over short distances
– PAN (Personal Area Network)
• Connects our mobile devices
– Smartphones
– Tethering
– Headsets and headphones
– Health monitors
– Automobile and phone integration
– Smartwatches
– External speakers
```
Bluetooth
30
```
• Turn your phone into a WiFi hotspot
– Your own personal wireless router
– Extend the cellular data network
to all of your devices
• Dependent on phone type and provider
– May require additional charges and data costs
```
Hotspot
31
• Touchscreen pen / touch screen stylus / capacitive stylus
– Activate the interface without actually touching it
• Handwriting
– Note taking, signatures
• Precise selection
– Easier to see the screen
Touch pens
32
• Digital stylus
– A more advanced writing tool
• The stylus communicates directly to the device
– Pressure sensitivity, programmable buttons, etc.
• Must be compatible with the tablet
– e.g., Apple iPad uses an Apple Pencil
Active stylus
33
• Use an active stylus with an external digitizer
| – Very precise input
Drawing pad
34
```
Replace the mouse
– Useful in tight working areas
– Common on laptops
• External options
– Battery powered
– Bluetooth connected
• Drag and tap
– Or use multiple finger input for right-clicking, zooming,
and window control
• Enable and disable
– Avoid inadvertent mouse clicks and movements
```
Trackpad
35
```
• Hands-free audio - Earphones and microphone
• Wired
– USB connections are common on laptops
– Connects to 3.5 mm
TRRS (tip-ring-ring-sleeve) connector
– Analog audio jack
– iPhone can use Lightning port
• Wireless - Bluetooth headsets
```
Headsets
36
* Mobile audio - Battery powered
* Wireless connection - Bluetooth link
* Stereo sound - Small package
Speakers
37
```
– Use external keyboard and mouse
– Extend existing laptop interfaces
– Add additional functionality
– Desktop adapter cards
– Avoid cable issues
```
Docking station
38
– Similar to a docking station
– Does not commonly have an expansion card option
– Usually connects using USB
Port replicator
39
Global System for Mobile Communications
– Mobile networking standard
1.4 - Cellular Standards
• 90% of the market
– Originally an EU standard
– Worldwide coverage
• Used by AT&T and T-Mobile in the United States
– Move your SIM card (Subscriber Identity Module) from
phone to phone
• Original GSM standard used multiplexing
– Everyone gets a little slice of time
GSM
40
• Code Division Multiple Access
– Everyone communicates at the same time
– Each call uses a different code
– The codes are used to filter each call on the receiving side
• Used by Verizon and Sprint
– Handsets are controlled by the network provider
– Not much adoption elsewhere
CDMA
41
```
• 3rd Generation
– Introduced in 1998
• Upgraded data connectivity over 2G
– Incremental 3G updates improved speeds
– Usually several megabits per second
• Bandwidth improvement allowed new functionality
– GPS
– Mobile television
– Video on demand
– Video conferencing
```
3G technology
42
• Long Term Evolution (LTE)
– A “4G” technology
– Converged standard (GSM and CDMA providers)
– Based on GSM and EDGE
(Enhanced Data Rates for GSM Evolution)
– Standard supports download rates of 150 Mbit/s
• LTE Advanced (LTE-A)
– Standard supports download rates of 300 Mbit/s
4G and LTE
43
```
• Fifth generation cellular networking
– Launched worldwide in 2020
• Significant performance improvements
– At higher frequencies
– Eventually 10 gigabits per second
– Slower speeds from 100-900 Mbit/s
• Significant IoT impact
– Bandwidth becomes less of a constraint
– Larger data transfers
– Faster monitoring and notification
– Additional cloud processing
```
5G
44
• PRL (Preferred Roaming List) updates
– CDMA networks (i.e., Verizon, Sprint)
• Allows your phone to connect to the right tower
– Can be updated over the air (OTA)
Updates
45
• Turn your phone into a WiFi hotspot
– Your own personal wireless router
– Extend the cellular data network to all of your devices
• Dependent on phone type and provider
– May require additional charges and data costs
Hotspot
46
```
• Connect a Bluetooth device
– Built-in security - Use or verify a PIN
• Pair the devices one time
– Future connections should be automatic
• Check with the manufacturer
– May prefer a specific sequence
– Discoverable mode isn’t always obvious
```
Bluetooth pairing
47
```
• Enable Bluetooth on both devices
– Android and iOS: Settings / Bluetooth
• Set devices to discoverable mode
– May require key sequence on Bluetooth device
• Select discovered device
– Many devices may appear!
• Enter or confirm PIN
– Should be the same on both devices
• Test connectivity
– Devices should now communicate
```
Bluetooth pairing process
48
Created by the U.S. Department of Defense
– Over 30 satellites currently in orbit
• Precise navigation - Need to see at least 4 satellites
• Determines location based on timing differences
– Longitude, latitude, altitude
• Mobile device location services and geotracking
– Maps, directions
– Determine physical location based on
GPS, WiFi, and cellular towers
GPS (Global Positioning System)
49
• Manage company-owned and user-owned mobile devices
– BYOD - Bring Your Own Device
• Centralized management of the mobile devices
– Specialized functionality
• Set policies on apps, data, camera, etc.
– Control the remote device
– The entire device or a “partition”
• Manage access control
– Force screen locks and PINs on these single user devices
MDM (Mobile Device Management)
50
• Corporate email configuration
– User does not need to configure anything
– The MDM makes the changes on the device
– Account details, server address, communication method
• Two-factor authentication
– Require specific authentication types
– Biometrics, pseudo-random authentication app
• Corporate applications
– Allow or restrict app installation
– Prevent unauthorized app usage
MDM configurations
51
```
• Many settings are preconfigured
– Telephone / Text messaging
• Email
– Everyone handles email services differently
– Corporate email configurations can vary
• Data synchronization
– Based on data rates and speeds
– Important for backup and recovery
```
Configuring a mobile device
52
```
• Outlook, Exchange
– Microsoft’s email service
– Usually the same for Hotmail and Outlook.com
• Authenticate to Microsoft 365
– Username, password
• Select the items to synchronize
– Changes in Outlook will appear on the mobile device
• Same process for Google Workspace
– Formerly known as G Suite
```
Microsoft 365
53
• Integrated into iOS and iPadOS
– Provide an iCloud username and password
• Select synchronization options
– Extensive customization
• Synchronize to macOS
– Use your desktop, laptop, or mobile device
iCloud
54
```
• Data types
– Mail
– Pictures, music, video
– Calendar
– Contacts
• Data caps and transfer costs
– Cellular vs 802.11
– Enable or disable network connections
– Control the use of cellular downloads
```
Synchronizing data
55
Transported inside of IP
– Encapsulated by the IP protocol
• Two ways to move data from place to place
– Different features for different applications
• OSI Layer 4
– The transport layer
• Multiplexing
– Use many different applications at the same time
– TCP and UDP
TCP and UDP
56
• Connection-oriented
– A formal connection setup and close
• “Reliable” delivery
– Recovery from errors
– Can manage out-of-order messages or retransmissions
• Flow control
– The receiver can manage how much data is sent
TCP – Transmission Control Protocol
57
• Connectionless - No formal open/close to the connection
• “Unreliable” delivery
– No error recovery
– No reordering of data or retransmissions
• No flow control
– Sender determines the amount of data transmitted
UDP – User Datagram Protocol
58
• Real-time communication
– There’s no way to stop and resend the data
– Time doesn’t stop for your network
• Connectionless protocols
– DHCP (Dynamic Host Configuration Protocol)
– TFTP (Trivial File Transfer Protocol)
UDP
59
• Connection-oriented protocols prefer a “return receipt”
– HTTPS (Hypertext Transfer Protocol Secure)
– SSH (Secure Shell)
• The application doesn’t worry about out of order
frames or missing data
– TCP handles all of the communication overhead
– The application has one job
TCP
60
– Server IP address, protocol,
server application port number
– Client IP address, protocol, client port number
• IPv4 sockets
61
– Ports 0 through 1,023
| – Usually on a server or service
Non-ephemeral ports – permanent port numbers
62
– temporary port numbers
– Ports 1,024 through 65,535
– Determined in real-time by the client
Ephemeral ports
63
• Well-known port number
– Client and server need to match
• Important for firewall rules - Port-based security
• A bit of rote memorization
– Becomes second nature after a while
• Make sure you know port number, protocol,
and how the protocol is used
Port numbers
64
• tcp/20 (active mode data), tcp/21 (control)
– Transfers files between systems
• Authenticates with a username and password
– Some systems use a generic/anonymous login
• Full-featured functionality - List, add, delete, etc.
FTP - File Transfer Protocol
65
* Encrypted communication link - tcp/22
| * Looks and acts the same as Telnet
SSH - Secure Shell
66
Telnet – Telecommunication Network - tcp/23
• Login to devices remotely
– Console access
• In-the-clear communication
– Not the best choice for production systems
Telnet
67
• SMTP - Simple Mail Transfer Protocol
– Server to server email transfer - tcp/25
• Also used to send mail from a device to a mail server
– Commonly configured on mobile devices and email clients
• Other protocols are used for clients to receive email
– IMAP, POP3
SMTP - Simple Mail Transfer Protocol
68
• Converts names to IP addresses - udp/53
– www.professormesser.com = 162.159.246.164
• These are very critical resources
– Usually multiple DNS servers are in production
DNS - Domain Name System
69
• Automated configuration of IP address, subnet mask and
other options - udp/67, udp/68
– Requires a DHCP server
– Server, appliance, integrated into a SOHO router, etc.
• Dynamic / pooled
– IP addresses are assigned in real-time from a pool
– Each system is given a lease and must renew at set intervals
• DHCP reservation
– Addresses are assigned by MAC address in the DHCP server
– Manage addresses from one location
DHCP - Dynamic Host Configuration Protocol
70
```
• Hypertext Transfer Protocol
– Communication in the browser
– And by other applications
• In the clear or encrypted
– Supported by nearly all web servers and clients
```
HTTP and HTTPS
71
```
• Receive emails from an email server
– Authenticate and transfer
• POP3 - Post office Protocol version 3
– tcp/110
– Basic mail transfer functionality
• IMAP4 - Internet Message Access Protocol v4
– tcp/143
– Includes email inbox management from multiple clients
```
POP3 / IMAP
72
• Protocol used by Microsoft Windows
– File sharing, printer sharing
– Also called CIFS (Common Internet File System)
SMB - Server Message Block
73
udp/137 - NetBIOS name services (nbname)
| tcp/139 - NetBIOS session service (nbsession)
Using NetBIOS over TCP/IP
74
Direct SMB communication over TCP without
| the NetBIOS transport
Direct over tcp/445 (NetBIOS-less)
75
```
• Gather statistics from network devices
– Queries: udp/161
– Traps: udp/162
• v1 – The original
– Structured tables
– In-the-clear
• v2 – A good step ahead
– Data type enhancements
– Bulk transfers
– Still in-the-clear
• v3 – A secure standard
– Message integrity
– Authentication
– Encryption
```
SNMP - Simple Network Management Protocol
76
• LDAP (Lightweight Directory Access Protocol) - tcp/389
• Store and retrieve information in a network directory
– Commonly used in Microsoft Active Directory
LDAP
77
• Share a desktop from a remote location over tcp/3389
• Remote Desktop Services on many Windows versions
• Can connect to an entire desktop or just an application
• Clients for Windows, macOS, Linux, Unix, iPhone,
Android, and others
RDP - Remote Desktop Protocol
78
tcp/20, tcp/21 Sends and receives files between systems
FTP
79
tcp/22 Encrypted console access
SSH
80
udp/137
NetBIOS
81
NetBIOS
tcp/139
82
SMB
tcp/445
83
tcp/443
HTTPS
84
tcp/389
LDAP
85
tcp/3389
RDP
86
• Routes traffic between IP subnets
– Makes forwarding decisions based on IP address
– Routers inside of switches sometimes called
“layer 3 switches”
• Often connects diverse network types
– LAN, WAN, copper, fiber
Routers
87
```
• Bridging done in hardware
– Application-specific integrated circuit (ASIC)
– Forwards traffic based on data link address
• Many ports and features
– The core of an enterprise network
– May provide Power over Ethernet (PoE)
• Multilayer switch
– Includes routing functionality
```
Switches
88
```
• Very few configuration options
– Plug and play
• Fixed configuration
– No VLANs
• Very little integration with other devices
– No management protocols
• Low price point
– Simple is less expensive
```
Unmanaged switches
89
```
• VLAN support
– Interconnect with other switches via 802.1Q
• Traffic prioritization
– Voice traffic gets a higher priority
• Redundancy support
– Spanning Tree Protocol (STP)
• Port mirroring
– Capture packets
• External management
– Simple Network Management Protocol (SNMP)
```
Managed switches
90
• Not a wireless router
– A wireless router is a router and an access point
in a single device
• An access point is a bridge
– Extends the wired network onto the wireless network
– Makes forwarding decisions based on MAC address
Access point
91
• Combination of punch-down blocks and
RJ-45 connectors
• Runs from desks are made once
– Permanently punched down to patch panel
• Patch panel to switch can be easily changed
– No special tools
– Use existing cables
Patch Panels
92
• Filters traffic by port number
– OSI layer 4 (TCP/UDP)
– Some firewalls can filter based on the application
• Can encrypt traffic into/out of the network
– Protect your traffic between sites
• Can proxy traffic
– A common security technique
• Most firewalls can be layer 3 devices (routers)
– Usually sits on the ingress/egress of the network
Firewalls
93
• Power provided on an Ethernet cable
– One wire for both network and electricity
– Phones, cameras, wireless access points
– Useful in difficult-to-power areas
• Power provided at the switch
– Built-in power - Endspans
– In-line power injector - Midspans
Power over Ethernet (PoE)
94
• Power over Ethernet
| – Commonly marked on the switch or interfaces
PoE switch
95
• “Multi-port repeater”
– Traffic going in one port is repeated to
every other port
• Everything is half-duplex
• Becomes less efficient as network traffic increases
• 10 megabit / 100 megabit
• Difficult to find today
Hub
96
```
• Broadband
– Transmission across multiple frequencies
– Different traffic types
• Data on the “cable” network
– DOCSIS (Data Over Cable Service Interface Specification)
• High-speed networking
– Speeds up to 1 Gigabit/s are available
• Multiple services
– Data, voice, video
```
Cable modem
97
• ADSL (Asymmetric Digital Subscriber Line)
– Uses telephone lines
• Download speed is faster than the upload
speed (asymmetric)
– ~10,000 foot limitation from the central office (CO)
– 52 Mbit/s downstream / 16 Mbit/s upstream are
common
– Faster speeds may be possible if closer to the CO
DSL modem
98
• Optical network terminal
– Fiber to the premises
• Connect the ISP fiber network to the copper network
– Demarcation point (demarc) in the data center
– Terminal box on the side of the building
• Line of responsibility
– One side of the box is the ISP
– Other side of the box is your network
ONT
99
```
• The fundamental network device
– Every device on the network has a NIC
– Computers, servers, printers, routers, switches,
phones, tablets, cameras, etc.
• Specific to the network type
– Ethernet, WAN, wireless, etc.
• Often built-in to the motherboard
– Or added as an expansion card
• Many options - Single port, multi-port, copper, fiber
```
Network Interface Card (NIC)
100
```
• Networking devices have different functional
planes of operation
– Data, control, and management planes
• Split the functions into separate logical units
– Extend the functionality and management
of a single device
– Perfectly built for the cloud
• Infrastructure layer / Data plane
– Process the network frames and packets
– Forwarding, trunking, encrypting, NAT
• Control layer / Control plane
– Manages the actions of the data plane
– Routing tables, session tables, NAT tables
– Dynamic routing protocol updates
• Application layer / Management plane
– Configure and manage the device
– SSH, browser, API
```
SDN (Software Defined Networking)
101
• One of the original 802.11 wireless standards
– October 1999
• Operates in the 5 GHz range
– Or other frequencies with special licensing
• 54 megabits per second (Mbit/s)
• Smaller range than 802.11b
– Higher frequency is absorbed by objects in the way
• Not commonly seen today
802.11a
102
```
• Also an original 802.11 standard - October 1999
• Operates in the 2.4 GHz range
• 11 megabits per second (Mbit/s)
• Better range than 802.11a, less absorption problems
• More frequency conflict
– Baby monitors, cordless phones,
microwave ovens, Bluetooth
• Not commonly seen today
```
802.11b
103
* An “upgrade” to 802.11b - June 2003
* Operates in the 2.4 GHz range
* 54 megabits per second (Mbit/s) - Similar to 802.11a
* Backwards-compatible with 802.11b
* Same 2.4 GHz frequency conflict problems as 802.11b
802.11g
104
```
• The update to 802.11g, 802.11b, and 802.11a
– October 2009
• Operates at 5 GHz and/or 2.4 GHz
– 40 MHz channel widths
• 600 megabits per second (Mbit/s)
– 40 MHz mode and 4 antennas
• 802.11n uses MIMO
– Multiple-input multiple-output
– Multiple transmit and receive antennas
```
802.11n (Wi-Fi 4)
105
```
• Approved in January 2014
– Significant improvements over 802.11n
• Operates in the 5 GHz band
– Less crowded, more frequencies (up to 160 MHz
channel bandwidth)
• Increased channel bonding - Larger bandwidth usage
• Denser signaling modulation
– Faster data transfers
• Eight MU-MIMO downlink streams
– Twice as many streams as 802.11n
– Nearly 7 gigabits per second
```
802.11ac (Wi-Fi 5)
106
• Approved in February 2021
– The successor to 802.11ac/Wi-Fi 5
• Operates at 5 GHz and/or 2.4 GHz
– 20, 40, 80, and 160 MHz channel widths
• 1,201 megabits per second per channel
– A relatively small increase in throughput
– Eight bi-directional MU-MIMO streams
• Orthogonal frequency-division multiple access (OFDMA)
– Works similar to cellular communication
– Improves high-density installations
802.11ax (Wi-Fi 6)
107
• Wireless access point in a house with the stock antennas
– You might get a range of 40 to 50 meters
• Try connecting two buildings located miles from each other
– Fixed directional antennas and increased signal strength
• Outdoors
– Minimal signal absorption or bounce
• Directional antennas
– Focused, point-to-point connection
• Wireless regulations are complex
– Refer to your country’s regulatory agency
• Frequency use
– Unlicensed 2.4 GHz or 5 GHz frequencies
– Additional frequencies may be available
– Additional licensing may be required
• Signal strength
– Indoor and outdoor power is usually regulated
• Outdoor antenna installation is not trivial
– Get an expert, be safe
Long-range fixed wireless
108
```
• It’s everywhere
– Access badges
– Inventory/Assembly line tracking
– Pet/Animal identification
– Anything that needs to be tracked
• Radar technology
– Radio energy transmitted to the tag
– RF powers the tag, ID is transmitted back
– Bidirectional communication
– Some tag formats can be active/powered
```
RFID (Radio-frequency identification)
109
```
• Two-way wireless communication
– Builds on RFID, which is mostly one-way
• Payment systems
– Major credit cards, online wallets
• Bootstrap for other wireless
– NFC helps with Bluetooth pairing
• Access token, identity “card”
– Short range with encryption support
```
NFC (Near field communication)
110
```
• Frequency
– 2.4 GHz or 5 GHz
– And sometimes both
• Channels
– Groups of frequencies, numbered by the IEEE
– Non-overlapping channels would be ideal
• Regulations
– Most countries have regulations to
manage frequency use
– Spectrum use, power output,
interference requirements, etc.
```
802.11 technologies
111
```
• Remove the wires
– Headsets, speakers, keyboards / mice
• Uses the 2.4 GHz range
– Unlicensed ISM
(Industrial, Scientific and Medical) band
– Same as 802.11
• Short-range
– Most consumer devices operate
to about 10 meters
– Industrial Bluetooth devices can communicate
over 100 meters
```
Bluetooth
112
• Domain Name System
– Convert names to IP addresses
– And vice versa
• Distributed naming system
– The load is balanced across many different servers
• Usually managed by the ISP or IT department
– A critical resource
DNS server
113
```
• Dynamic Host Configuration Protocol
– Automatic IP address configuration
• Very common service
– Available on most home routers
• Enterprise DHCP will be redundant
– Usually running on central servers
```
DHCP server
114
```
• Centralized storage of documents,spreadsheets,
videos, pictures, and any other files
– A fileshare
• Standard system of file management
– SMB (Server Message Block),
Apple Filing Protocol (AFP), etc.
• The front-end hides the protocol
– Copy, delete, rename, etc.
```
File server
115
• Connect a printer to the network
– Provide printing services for all network devices
• May be software in a computer
– Computer is connected to the printer
• May be built-in to the printer
– Network adapter and software
• Uses standard printing protocols
– SMB (Server Message Block), IPP (Internet
Printing Protocol), LPD (Line Printer Daemon)
Print server
116
• Store your incoming mail
– Send your outgoing mail
• Usually managed by the ISP or the IT department
– A complex set of requirements
• Usually one of the most important services
– 24 x 7 support
Mail server
117
```
• Standard for message logging
– Diverse systems, consolidated log
• Usually a central logging receiver
– Integrated into the SIEM
• You’re going to need a lot of disk space
– No, more. More than that.
```
Syslog
118
• Respond to browser requests
– Using standard web browsing protocols - HTTP/HTTPS
– Pages are built with HTML, HTML5
• Web pages are stored on the server
– Downloaded to the browser
– Static pages or built dynamically in real-time
Web server
119
```
• Login authentication to resources
– Centralized management
• Almost always an enterprise service
– Not required on a home network
• Usually a set of redundant servers
– Always available
– Extremely important service
```
Authentication server
120
```
Unsolicited messages
– Email, forums, etc.
• Various content
– Commercial advertising
– Non-commercial proselytizing
– Phishing attempts
• Significant technology issue
– Security concerns, resource utilization,
storage costs, managing the spam
```
Spam
121
• Unsolicited email
– Stop it at the gateway before it reaches the user
– On-site or cloud-based
Spam gateways
122
```
• Next-generation firewall, Unified Threat
Management (UTM) / Web security gateway
• URL filter / Content inspection
• Malware inspection
• Spam filter
• CSU/DSU
• Router, Switch
• Firewall
• IDS/IPS
• Bandwidth shaper
• VPN endpoint
```
All-in-one security appliance
123
```
• Distribute the load
– Multiple servers
– Invisible to the end-user
• Large-scale implementations
– Web server farms, database farms
• Fault tolerance
– Server outages have no effect - Very fast convergence
```
Load balancers
124
* Configurable load - Manage across servers
* TCP offload - Protocol overhead
* SSL offload - Encryption/Decryption
* Caching - Fast response
* Prioritization - QoS
* Content switching - Application-centric balancing
Load balancer features
125
• An intermediate server
– Client makes the request to the proxy
– The proxy performs the actual request
– The proxy provides results back to the client
• Useful features
– Access control, caching, URL filtering, content scanning
Proxy server
126
• Supervisory Control and Data Acquisition System
– Large-scale, multi-site Industrial Control Systems (ICS)
• PC manages equipment
– Power generation, refining,
manufacturing equipment
– Facilities, industrial, energy, logistics
• Distributed control systems
– Real-time information
– System control
– Requires extensive segmentation
– No access from the outside
SCADA / ICS
127
```
• Legacy systems
– Another expression for “really old”
– May also be “really important”
– Learning old things can be just as important as
learning the new things
• Embedded systems
– Purpose-built device
– Not usual to have direct access to
the operating system
– Alarm system, door security, time card system
```
Legacy and embedded systems
128
```
• Appliances
– Refrigerators
• Smart devices
– Smart speakers respond to voice commands
• Air control
– Thermostats, temperature control
• Access
– Smart doorbells
• May require a segmented network
– Limit any security breaches
```
IoT (Internet of Things) devices
129
• Internet Protocol version 4
| – OSI Layer 3 address
IPv4 addresses
130
• Internet Protocol v6 - 128-bit address
– 340,282,366,920,938,463,463,374,607,431,768,211,456
addresses (340 undecillion)
– 6.8 billion people could each have
5,000,000,000,000,000,000,000,000,000 addresses
IPv6 addresses
131
IP Address, e.g., 192.168.1.165
– Every device needs a unique IP address
• Subnet mask, e.g., 255.255.255.0
– Used by the local device to determine its subnet
– The subnet mask isn’t (usually) transmitted
across the network
• Default gateway, e.g., 192.168.1.1
– The router that allows you to communicate
outside of your local subnet
– The default gateway must be an IP address
on the local subnet
Networking with IPv4
132
```
• We remember names
– professormesser.com, google.com, youtube.com
• Internet routers don’t know names
– Routers only know IP addresses
• Something has to translate between
names and IP addresses
– Domain Name Services
• You configure two DNS servers in
your IP configuration
– That’s how important it is
```
DNS servers
133
```
• Translates human-readable names
into computer-readable IP addresses
– You only need to remember
www.ProfessorMesser.com
• Hierarchical
– Follow the path
• Distributed database
– Many DNS servers
– 13 root server clusters (over 1,000 actual servers)
– Hundreds of generic top-level domains (gTLDs) -
.com, .org, .net, etc.
– Over 275 country code top-level domains (ccTLDs) -
.us, .ca, .uk, etc.
```
Domain Name System
134
• Resource Records (RR)
– The database records of domain name services
• Over 30 record types
– IP addresses, certificates, host alias names, etc.
• These are important and critical configurations
– Make sure to check your settings, backup, and test!
DNS records
135
```
• Defines the IP address of a host
– This is the most popular query
• A records are for IPv4 addresses
– Modify the A record to change the
host name to IP address resolution
• AAAA records are for IPv6 addresses
– The same DNS server, different records
```
Address records (A) (AAAA)
136
• Determines the host name for the mail server - this isn’t an IP address; it’s a name
Mail exchanger record (MX)
137
```
Human-readable text information
– Useful public information
– Was originally designed for
informal information
• Can be used for verification purposes
– If you have access to the DNS,
then you must be the administrator
of the domain name
• Commonly used for email security
– External email servers validate
information from your DNS
```
Text records (TXT)
138
• SPF protocol
– A list of all servers authorized to send emails
for this domain
– Prevent mail spoofing
– Mail servers perform a check to see if incoming mail
really did come from an authorized host
Sender Policy Framework (SPF)
139
• Digitally sign a domain’s outgoing mail
– Validated by mail servers, not usually
seen by the end user
– The public key is in the DKIM TXT record
Domain Keys Identified Mail (DKIM)
140
Domain-based Message Authentication, Reporting,
and Conformance (DMARC)
– Prevent unauthorized email use (spoofing)
– An extension of SPF and DKIM
• You decide what external email servers should do with
emails that don’t validate through SPF or DKIM
– That policy is written into a DMARC TXT record
– Accept all, send to spam, or reject the email
– Compliance reports can be sent to the email administrator
DMARC
141
```
• IP address range
– And excluded addresses
• Subnet mask
• Lease durations
• Other scope options
– DNS server
– Default gateway
– VOIP servers
```
Scope properties
142
```
• Grouping of IP addresses
– Each subnet has its own scope
– 192.168.1.0/24
– 192.168.2.0/24
– 192.168.3.0/24
• A scope is generally a single contiguous
pool of IP addresses
– DHCP exceptions can be made inside of the scope
```
DHCP pools
143
• Dynamic assignment
– DHCP server has a big pool of addresses to give out
– Addresses are reclaimed after a lease period
• Automatic assignment
– Similar to dynamic allocation
– DHCP server keeps a list of past assignments
– You’ll always get the same IP address
DHCP address assignment
144
```
• Address reservation
– Administratively configured
• Table of MAC addresses
– Each MAC address has a matching IP address
• Other names
– Static DHCP Assignment, Static DHCP,
Static Assignment, IP Reservation
```
DHCP address allocation
145
```
Leasing your address
– It’s only temporary
– But it can seem permanent
• Allocation
– Assigned a lease time by the DHCP server
– Administratively configured
• Reallocation
– Reboot your computer
– Confirms the lease
```
DHCP leases
146
```
• T1 timer
– Check in with the lending DHCP server to renew
the IP address
– 50% of the lease time (by default)
• T2 timer
– If the original DHCP server is down, try rebinding
with any DHCP server
– 87.5% of the lease time (7/8ths)
```
DHCP renewal
147
Local Area Networks
| • A group of devices in the same broadcast domain
LANs
148
* Virtual Local Area Networks
* A group of devices in the same broadcast domain
* Separated logically instead of physically
Virtual LANs
149
• Virtual Local Area Networks
– A group of devices in
the same broadcast domain
Configuring VLANs
150
```
• Virtual Private Networks
– Encrypted (private) data traversing a public network
• Concentrator
– Encryption/decryption access device
– Often integrated into a firewall
• Many deployment options
– Specialized cryptographic hardware
– Software-based options available
```
VPNs
151
• On-demand access from a remote device
– Software connects to a VPN concentrator
• Some software can be configured as always-on
Client-to-Site VPNs
152
• Communication to a satellite
– Non-terrestrial communication
• High cost relative to terrestrial networking
– 50 Mbit/s down, 3 Mbit/s up are common
– Remote sites, difficult-to-network sites
• High latency
– 250 ms up, 250 ms down
– Starlink advertises 40 ms and is working on 20 ms
• High frequencies - 2 GHz
– Line of sight, rain fade
Satellite networking
153
```
• High speed data communication
– Frequencies of light
• Higher installation cost than copper
– Equipment is more costly
– More difficult to repair
– Communicate over long distances
• Large installation in the WAN core
– Supports very high data rates
– SONET, wavelength division multiplexing
• Fiber is slowly approaching the premises
– Business and home use
```
Fiber
154
• Broadband
– Transmission across multiple frequencies
– Different traffic types
• Data on the “cable” network
– DOCSIS (Data Over Cable Service Interface
Specification)
• High-speed networking
– 50 Mbits/s through 1,000+ Mbit/s are common
• Multiple services
– Data, voice, video
Cable broadband
155
• ADSL (Asymmetric Digital Subscriber Line)
– Uses telephone lines
• Download speed is faster than the upload speed
(asymmetric)
– 200 Mbit/s downstream / 20 Mbit/s upstream
are common
– ~10,000 foot limitation from the central office (CO)
– Faster speeds may be possible if closer to the CO
DSL
156
```
• Mobile devices
– “Cell” phones
• Separate land into “cells”
– Antenna coverages a cell with certain frequencies
• Tethering
– Turn your phone into a wireless router
• Mobile hotspot
– Standalone devices
– Use your phone for other things
```
Cellular networks
157
```
• Wireless Internet Service Provider
– Terrestrial internet access using wireless
• Connect rural or remote locations
– Internet access for everyone
• Many different deployment technologies
– Meshed 802.11
– 5G home internet
– Proprietary wireless
• Need an outdoor antenna
– Speeds can range from ~ 10 to 1,000 megabits per second
```
WISP
158
```
• Local Area Network
– Local is relative
• A building or group of buildings
– High-speed connectivity
• Ethernet and 802.11 wireless
– Any slower and it isn’t “local”
```
LAN
159
```
• Wide Area Network
– Spanning the globe
• Generally connects LANs across a distance
– And generally much slower than the LAN
• Many different WAN technologies
– Point-to-point serial, MPLS, etc.
– Terrestrial and non-terrestrial
```
WAN
160
```
• Personal Area Network
– Your own private network
– Bluetooth, IR, NFC
• Automobile
– Audio output
– Integrate with phone
• Mobile phone - Wireless headset
• Health
– Workout telemetry, daily reports
```
PAN
161
```
• Metropolitan Area Network
– A network in your city
– Larger than a LAN, often smaller than a WAN
• Historically MAN-specific topologies
– Metro Ethernet
• Common to see government ownership
– They “own” the right-of-way
```
MAN
162
• Storage Area Network (SAN)
– Looks and feels like a local storage device
– Block-level access
– Very efficient reading and writing
• Requires a lot of bandwidth
– May use an isolated network and high-speed
network technologies
SAN
163
```
• Wireless LAN
– 802.11 technologies
• Mobility
– Within a building
– In a limited geographical area
• Expand coverage with additional access points
– Downtown area
– Large campus
```
WLAN
164
```
• “Pinch” the connector onto a wire
– Coaxial, twisted pair, fiber
• Connect the modular connector to
the Ethernet cable
– The final step of the process
• Metal prongs are pushed through the insulation
– The plug is also permanently pressed
onto the cable sheath
```
Cable crimper
165
```
• Wireless networks are
incredibly easy to monitor
– Everyone “hears” everything
• Purpose-built hardware or
mobile device add-on
– Specializes in 802.11 analysis
• Identify errors and interference
– Validate antenna location and installation
```
WiFi analyzer
166
```
• Where does that wire go?
– Follow the tone
• Tone generator
– Puts an analog sound on the wire
• Inductive probe
– Doesn’t need to touch the copper
– Hear through a small speaker
```
Tone generator
167
```
• “Punch” a wire into a wiring block
– 66 block, 110 block, and others
• Can be tedious
– Every wire must be
individually punched
• Trims the wires during the punch
– Very efficient process
```
Punch-down tools
168
```
• Relatively simple
– Continuity test
• Can identify missing pins
– Or crossed wires
• Not usually used for frequency testing
– Crosstalk, signal loss, etc.
```
Cable testers
169
```
Useful for testing physical ports
– Or fooling your applications
• Serial / RS-232 (9 pin or 25 pin)
• Network connections
– Ethernet, T1, Fiber
```
Loopback plugs
170
• Intercept network traffic
– Send a copy to a packet capture device
• Physical taps
– Disconnect the link, put a tap in the middle
– Can be an active or passive tap
• Port mirror
– Port redirection, SPAN (Switched Port ANalyzer)
– Software-based tap
– Limited functionality, but can work well in a pinch
Taps and Port Mirrors
171
• Balanced pair operation
– Two wires with equal and opposite signals
– Transmit+, Transmit- / Receive+, Receive-
• The twist is the secret!
– Keeps a single wire constantly moving
away from the interference
– The opposite signals are compared on the other end
• Pairs in the same cable have different twist rates
Twisted pair copper cabling
172
• Two or more forms share a common axis
• RG-6 used in television/digital cable
– And high-speed Internet over cable
Coaxial cables
173
```
• Traditional cable jacket - Polyvinyl chloride (PVC)
• Fire-rated cable jacket
– Fluorinated ethylene polymer (FEP) or
low-smoke polyvinyl chloride (PVC)
• Plenum-rated cable may not be as flexible
– May not have the same bend radius
• Worst-case planning
– Important concerns for any structure
```
Plenum-rated cable
174
```
• UTP (Unshielded Twisted Pair)
– No additional shielding
– The most common twisted pair cabling
• STP (Shielded Twisted Pair)
– Additional shielding protects against interference
– Shield each pair and/or the overall cable
– Requires the cable to be grounded
• Abbreviations
– U = Unshielded
– S = Braided shielding
– F = Foil shielding
• (Overall cable) / (individual pairs)TP
– Braided shielding around the entire cable and
foil around the pairs is S/FTP
– Foil around the cable and no shielding around
the pairs is F/UTP
```
Unshielded and shielded cable
175
```
• Overhead cable isn’t always a good option
– Put the cable in the ground
• Provides protection from the elements
– Designed to be waterproof
– Often filled with gel to repel water
– Conduit may not be needed
• Shielded twisted pair
– Provides grounding, adds strength
– Protects against signal interference
```
Direct burial STP
176
```
• Transmission by light
– The visible spectrum
• No RF signal
– Very difficult to monitor or tap
• Signal slow to degrade
– Transmission over long distances
• Immune to radio interference - There’s no RF
```
Optical fiber communication
177
• Short-range communication
– Up to 2 km
• Relatively inexpensive light source
– i.e., LED
Multimode fiber
178
• Long-range communication
– Up to 100 km without processing
• Expensive light source
– Commonly uses lasers
Single-mode fiber
179
• Pin assignments from T568-B standard
– Eight conductor 100-ohm balanced twisted-pair cabling
• T568A and T568B are different pin assignments for
8P8C connectors
– Assigns the T568A pin-out to horizontal cabling
• Many organizations traditionally use 568B
– Difficult to change in mid-stream
• You can’t terminate one side of the cable with
568A and the other with 568B
– This has never been the definition of a
Gigabit Ethernet crossover cable
T568A and T568B termination
180
```
White&and&Green
Green
White&and&Orange
Blue
White&and&Blue
Orange
White&and&Brown
Brown
```
TIA/EIA&568A
181
```
White&and&Orange
Blue
White&and&Blue
Orange
White&and&Brown
Brown
```
TIA/EIA&568B
182
• Simplify connections - Printers, storage devices,
keyboard, mouse
• USB 1.1
– Low speed: 1.5 megabits per second, 3 meters
– Full speed: 12 megabits per second, 5 meters
• USB 2.0 - 480 megabits per second, 5 meters
• USB 3.0 - SuperSpeed
– 5 gigabits per second, ~3 meters
– Standard does not specify a cable length
USB (Universal Serial Bus)
183
```
• USB has a lot of different connectors
– And they have changed over time
• Can be annoying to connect USB-A
– Third time’s the charm
• USB-C replaces all of these
– One connector to rule them all
• USB-C describes the physical connector
– It doesn’t describe the signal
```
USB-C
184
```
• Released July 2013
– Doubled the throughput over USB 3.0
• USB 3.0 is USB 3.1 Gen 1
– SuperSpeed USB - 5 Gbit/sec
• USB 3.1 is USB 3.1 Gen 2 - SuperSpeed+
– Twice the rate of USB 3.0/USB 3.1 Gen 1
```
USB 3.1
185
```
• USB 3.2
– Released September 2017
– Bandwidth can double with USB-C cables
– Uses an extra “lane” of communication
associated with the flip-flop wires in USB-C
• USB 3.0 -> 3.1 Gen 1 -> USB 3.2 Gen 1
– SuperSpeed USB 5 Gbps (single lane)
• USB 3.1 -> 3.1 Gen 2 -> USB 3.2 Gen 2
– SuperSpeed USB 10 Gbps (single lane)
```
USB 3.2
186
```
• High-speed serial connector
– Data and power on the same cable
– Based on Mini DisplayPort (MDP) standard
• Thunderbolt v1
– Two channels
– 10 Gbit/s per channel, 20 Gbit/s total throughput
– Mini DisplayPort connector
• Thunderbolt v2
– 20 Gbit/s aggregated channels
– Mini DisplayPort connector
• Thunderbolt v3
– 40 Gbit/s aggregated throughput - USB-C connector
• Maximum 3 meters (copper)
– 60 meters (optical)
– Daisy-chain up to 6 devices
```
Thunderbolt
187
```
• D-subminiature or D-sub
– The letter refers to the connector size
• Commonly used for RS-232
– Recommended Standard 232
– An industry standard since 1969
• Serial communications standard
– Built for modem communication
– Used for modems, printers, mice, networking
• Now used as a configuration port
```
Serial console cables
188
```
• DB-15 connector
– More accurately called DE-15
• Blue color
– PC System Design Guide
• Analog signal
– No digital
– Image degrades after 5 to 10 meters
```
VGA (Video Graphics Array
189
```
• Video and audio stream
– All digital, no analog
– ~ 20 meter distance before losing too much signal
• 19-pin (Type A) connector
– Proprietary connector
```
HDMI (High-Definition Multimedia Interface)
190
```
• Digital information sent in packetized form
– Like Ethernet and PCI Express
– Carries both audio and video
• Compatible with HDMI and DVI
– Passive adapter
– DisplayPort -> HDMI
– DisplayPort -> DVI
```
DisplayPort
191
```
• Single and dual link
– Single link; 3.7 Gbps (HDTV at 60 fps)
– Dual link; 7.4 Gbps (HDTV at 85 fps)
– No audio support
• DVI-A
– Analog signals
• DVI-D
– Digital signals
• DVI-I
– Integrated
– Digital and analog in the same connector
```
DVI (Digital Visual Interface)
192
• One power cable and data cable per device
| – One-to-one
SATA
193
• External device connections
– Uses the SATA standard
• Similar in size to SATA
– Connectors are physically different
eSATA cable
194
• Small Computer Systems Interface
– Not really “small” any longer
• Originally designed to string many peripherals
together onto a single cable/controller
– Up to 16 devices in a SCSI “chain”
• Many different formats
– Fast SCSI, Ultra SCSI, Ultra Wide SCSI, Ultra2 SCSI,
– Ultra3 SCSI, Ultra-320 SCSI, Ultra-640 SCSI,
– iSCSI (SCSI over IP)
• Parallel and serial options
The SCSI standard
195
```
• Not just for hard drives
– Scanners, tape drives, CD-ROM drives
• Many devices on a single bus
– 8 on narrow bus, 16 on wide bus
• Very intelligent interface functionality
– Much of the difficult configuration work is done
between the SCSI devices
• Industry longevity
– Well supported in the enterprise
– A standard drive for virtual system
```
SCSI advantages
196
• Every SCSI device on a single bus is
assigned a separate ID number
– SCSI ID 0 (SCSI controller), ID 2 (hard drive), ID 3 (CD-ROM)
• Logical units (LUNs) are defined within each SCSI ID
– Separate drives in a storage array or virtual machine
• The signal at the “end” of a physical SCSI bus is terminated
– Can be internal to the device or a
separate termination device
• Serial attached SCSI (SAS) devices have no
jumpers, terminators, or settings.
SCSI ID and logical unit (LUN)
197
```
• Move from parallel to serial
– Increased throughput
– Similar to the move from PATA to SATA
• Point-to-point connection
– No more daisy chains
• No termination required
– The bus has two devices on it
• The control and management of SCSI
– The speed of a serial connection
```
Serial attached SCSI
198
```
• Parallel AT Attachment
– Remember the PC/AT?
• An evolutionary process
– Circa 1999
• Originally called Integrated
Drive Electronics (IDE)
– A Western Digital invention
– 2nd generation called EIDE (Enhanced IDE)
• The evolution
– Promised faster speeds
– From 16 MB/s through 133 MB/s
– Additional devices
• Now called Parallel ATA (PATA)
```
The PATA Standard
199
• DVI-D and HDMI are electrically compatible
– HDMI is backward-compatible with DVI-D
– No signal conversion required
– No loss of video quality
DVI to HDMI
200
• DVI-A includes analog signals
– Backward compatible with VGA
– Only 640 x 480 is officially supported
• May only need an adapter - Analog to analog
• VGA to DVI digital will need a converter
– Check your interface specifications
DVI to VGA
201
6 position, 2 conductor (6P2C)
– Some cables will wire additional conductors
– Telephone or DSL connection
RJ11 connector
202
• Registered Jack type 45
• 8 position, 8 conductor (8P8C)
– Modular connector - Ethernet
RJ45 connector
203
```
• Wire-to-wire patch panel
– No intermediate interface required
• Wires are “punched” into the block
– Connecting block is on top
• Additional wires punched into connecting block
– Patch the top to the bottom
```
Punchdown block
204
• 24-pin double-sided USB connector
– Used for both hosts and devices
• Used for USB, Thunderbolt
– Interface is the same, signal can vary
USB-C
205
• 4-pin peripheral power connector
– Molex Connector Company
– AMP MATE-N-LOK
– Provides +12 V and +5 V
Molex connector
206
```
• Apple proprietary
– 8-pin digital signals
– iPhone, iPad, iPod devices
• Some advantages over Micro-USB
– Higher power output for phones and tablets
– Can be inserted either way
```
Lightning
207
```
• D-subminiature or D-sub
– The letter refers to the connector size
• Commonly used for RS-232
– Recommended Standard 232
– An industry standard since 1969
• Serial communications standard
– Built for modem communication
– Used for modems, printers, mice, networking
• Now used as a configuration port
– Management or Console port
```
DB-9
208
DIMM - Dual inline memory module
– Electrical contacts are different on each side
• 64 bit data width
DIMM
209
Small Outline Dual In-line Memory Module
– About half the width as a DIMM
• Used in laptops and mobile devices
SO-DIMM
210
• The memory on the DIMM
• Dynamic
– Needs constant refreshing
– Without refreshing, the data in memory disappears
• Random access
– Any storage location can be accessed directly
– Unlike magnetic tape
Dynamic Random Access Memory (DRAM)
211
• Synchronous DRAM (SDRAM)
• SDRAM is synchronous with the common system clock
– Queue up one process while waiting for another
– Classic DRAM didn’t wait for a clock signal
SDRAM
212
• Twice the data rate of DDR2
– Larger chip capacities - Maximum 16 GB per DIMM
• No backwards compatibility
– Speed brings sacrifice
Double Data Rate 3 (DDR3) SDRAM
213
• Faster data transfers between the memory module and
motherboard
– Maximum of 64 GB per DIMM
• The key has moved - No backwards compatibility
Double Data Rate 5 (DDR5) SDRAM
214
• Different names - Virtual RAM, swap file, etc.
• Swap currently unused application data to storage
– Free up space for other applications
• Managed automatically by the operating system
– Some configuration settings are available
Virtual memory
215
• Dual-channel, triple-channel, or quad-channel
• Memory combinations should match
– Exact matches are best
• Memory module slots are often colored differently
Multi-channel memory
216
```
• Used on critical computer systems
– VM servers, database servers, any server
• Parity memory
– Adds an additional parity bit
– Won’t always detect an error
– Can’t correct an error
• Error Correcting Code (ECC)
– Detects errors and corrects on the fly
– Not all systems use ECC
– It looks the same as non-ECC memory
```
Memory that checks itself
217
• Non-volatile magnetic storage - rapidly rotating platters
• Random-access
– Retrieve data from any part of the drive at any time
• Moving parts
– Spinning platters, moving actuator arm
– Mechanical components limit the access speed
– Mechanical components can also break
Hard disk drives (HDD)
218
* Non-volatile memory - No moving parts
| * Very fast performance - No spinning drive delays
Solid-state drives (SSD)
219
```
• Shrink the SATA drive into smaller devices
– Same data, different form factor
– Great for laptops and mobile devices
• Smaller than 2.5” SATA drives
– No spinning drive
– Allows for different form factors
```
mSATA (Mini-SATA)
220
• SATA was designed for hard drives
– Uses AHCI (Advanced Host Controller Interface) to
move drive data to RAM
– SATA revision 3 throughput up to 600 MB/s
– SSDs need a faster communication method
• NVMe (Non-volatile Memory Express)
– Designed for SSD speeds
– Lower latency, supports higher throughputs
– Take advantage of NVMe with an M.2 interface
AHCI vs. NVMe
221
```
Smaller form factor - No SATA data or power cables
• Can use a PCI Express bus connection
– 4 GB/second throughput or faster
when using NVMe PCIe x4
• Different connector types
– Needs to be compatible with the slot key/spacer
– B key, M key, or B and M key
– Some M.2 drives will support both
```
M.2 interface
222
```
• M.2 doesn’t guarantee NVMe
– Your M.2 interface may be using AHCI
– Check your documentation
• Your motherboard may only support
one type of M.2 key
– Check the documentation again
```
B-key and M-key
223
• Flash memory
– EEPROM (Electrically erasable programmable
read-only memory)
– Non-volatile memory - No power required to retain data
• Limited number of writes
– Can still read the data
• Not designed for archival storage
– Easy to lose or damage - Always have a backup
– Flash memory
Flash drives
224
• Small bumps read with a laser beam
– Microscopic binary storage
• Relatively slow
– Archival media
• Many different formats - CD-ROM, DVD-ROM, Blu-ray
• Internal and external drives
– For those uncommon application installations
Optical drives
225
• Hard drives store huge amounts of important data
• Hard drives are moving components
– They will eventually break
• What happens to the data when the drive fails?
– You can prepare for that
– Use an array of drives
• RAID is not backup
Data redundancy
226
• Redundant Array of Independent Disks
– They’re also inexpensive disks.
• Different RAID levels - Some redundant, some not
• RAID 0 – Striping
• RAID 1 - Mirroring
• RAID 5 – Striping with Parity
• Nested RAID - RAID 1+0 (a.k.a. RAID 10) - A stripe of mirrors
RAID
227
```
• File blocks are split between
two or more physical drives
– High performance
– Data written quickly
• No redundancy
– A drive failure breaks the array
– Raid 0 is zero redundancy
```
RAID 0 - Striping
228
```
• File blocks are duplicated between
two or more physical drives
• High disk utilization
– Every file is duplicated
– Required disk space is doubled
• High redundancy
– Drive failure does not affect data availability
```
RAID 1 - Mirroring
229
```
• Physical size - Case sizing
• Basic layout - Room for small changes
• Power - Standard connectors
• Airflow - Increasingly important
• Wikipedia: There are 40 different motherboard
types categorized!
```
Motherboard form factors
230
```
• Advanced Technology Extended
• Standardized by Intel in 1995
– Seen many updates over the years
• Power
– 20 pin connector
– 24 pin connector, additional 4/8 pin connector
```
ATX form factor
231
```
• A series of low-power motherboards
– Developed by VIA Technologies in 2001
– Small form factor
• Mini-ITX is screw-compatible with ATX
– Fits almost any enclosure
• Small form factor uses
– Single-purpose computing, i.e., streaming media
```
ITX form factor
232
* Communication path - A city of technology
* Internal PC growth - Independent pathways
* System expansion - Additional capabilities
A computer bus
233
```
• Peripheral Component Interconnect
– Created in 1994
• Many expansion options
– 32-bit and 64-bit bus width
– Parallel communication
• A common expansion interface on previous
computer generations
– PCI Express is the newer technology
```
Conventional PCI
234
• Also known as PCIe - Replaces the older PCI standard
• Communicates serially - Unidirectional serial “lanes”
– Slower devices don’t slow down everyone
• One, two, four, eight, sixteen, or thirty-two full-duplex lanes
– x1, x2, x4, x8, x16, x32
– “x” is pronounced “by” (“by 4,” “by 16”)
PCI Express
235
• Main motherboard power
– Provides +3.3 V, +/-5 V, and +/- 12 V
• 20 pin connector was the original ATX standard
– 24 pin was added for PCI Express power
• You can connect a 24-pin connector to a 20-pin
motherboard
– Some cables are 20-pin + 4-pin
24-pin motherboard power
236
• 4-pin ATX +12 V power
| – ATX12V Advanced Technology Extended motherboards
4-pin ATX
237
• A pin header
– A simple electrical interface
– The connector is attached to the header
• Many different uses
– Power, peripheral connections, lights, and buttons
Headers
238
```
• Multisocket
– Supports multiple physical CPU packages
– Split the load
• Memory slots - Supports 4+ modules
• Expansion slots
– Many slots and different sizes
• Overall size
– Designed for a rack-mounted system
– Larger ATX-sized system
```
Server motherboards
239
• Can range from full-size motherboards to compact or
monitor-only systems
– We can do a lot with increasingly smaller systems
• Single CPU - Reduces cost and complexity
• Memory slots - Usually two or four
• Expansion slots - May have limited options
Desktop motherboards
240
```
• Laptops - Small and light
• CPUs - Limited in speed - Thermal throttling
• Limited system modification
– Memory, CPU, functionality
• Portability - Smaller devices
– Low power consumption
```
Mobile motherboards
241
• Proprietary - Built to fit
• Replacement isn’t easy
– Swap the entire board
– Most components are on the system board
System board
242
• The software used to start your computer
– The firmware - System BIOS, ROM BIOS
– ROM or flash memory
• Initializes CPU and memory - Build the workspace
• POST - Power-On Self-Test
• Look for a boot loader - Start the operating system
BIOS - Basic Input/Output System
243
• The original / traditional BIOS
– It’s been around for more than 25 years
• Older operating systems talked to hardware through the BIOS
– Instead of accessing hardware directly
• Limited hardware support
– No drivers for modern network, video, and storage devices
Legacy BIOS
244
• Unified Extensible Firmware Interface
– Based on Intel’s EFI (Extensible Firmware Interface)
• A defined standard - Implemented by the manufacturers
• Designed to replace the legacy BIOS
– Need a modern BIOS for modern computers
– Graphical and text-based
UEFI BIOS
245
```
• Windows 8, 10, and 11
– Doesn’t actually shut down all the way
– Starts up so quickly, you can’t open the BIOS
configuration
• From the Windows desktop
– Hold down shift when clicking Restart
– Settings / Update & Security / Recovery / Advanced
startup / Restart now
– System Configuration (msconfig)
• Interrupt normal boot three times
– Presents the boot option screen
```
Fast startup
246
• Not needed for today’s flash-based storage
– Maintains older BIOS configurations
– May only be used to maintain date/time
• A bad battery will require a BIOS configuration or
date/time configuration on every boot
• On older systems, can reset the BIOS configuration
by removing the battery
– Newer computers use a jumper
The “CMOS” battery
247
• A specification for cryptographic functions
– Hardware to help with encryption functions
• Cryptographic processor
– Random number generator, key generators
• Persistent memory
– Comes with unique keys burned in during production
• Versatile memory
– Storage keys, hardware configuration information
– Password protected / No dictionary attacks
Trusted Platform Module (TPM)
248
• Often used in large environments (Clusters, redundant power)
• High-end cryptographic hardware
– Plug-in card or separate hardware device
• Key backup - Secured storage for servers
– Lightweight HSMs for personal use
(Smart card, USB, flash memory)
• Cryptographic accelerators
– Offload that CPU overhead from other devices
Hardware Security Module (HSM)
249
```
• CPU architecture developed by Arm Ltd.
– They design the chip, others license and build
• Simplified instruction set
– Efficient and fast processing
– Less power
– Less heat
• Traditionally used for mobile and IoT devices
– The lines are constantly blurring
```
Advanced RISC Machine (ARM
250
• Dual-core / Quad-core / Octa-core / Multi-core
• Multiple cores
– Each core has its own cache
– The entire chip may have a shared cache
Processor cores
251
• Run other operating systems within a single
hardware platform
– Multiple operating systems share physical
hardware components
• Virtualization in software was limited
– Performance and hardware
management challenges
• Virtualization added to the processor
– Hardware is faster and easier to manage
– Intel Virtualization Technology (VT)
– AMD Virtualization (AMD-V)
Virtualization support
252
Extend the functionality of your computer
– You may need more than the motherboard
provides
• Relatively simple process
– Designed for end-user installation
• Install hardware - Add a card
• Install a driver - Software for the operating system
Expansion cards
253
```
Output
– High-end audio
– Advanced headphone amp
– Home theater, Dolby decoding
• Multiple inputs
– Music capture
– Podcasting
– Microphone
```
Sound card
254
Many CPUs include an integrated GPU
– Video functionality is built into the CPU package
• Discrete graphics
– The GPU is not part of the CPU
• Separate interface card - High performance
Video card
255
```
• Video as an input
– Video capture, live streaming, external cameras
• High performance
– Video bandwidths can be quite high
– PCI Express connection
```
Capture card
256
```
• Ethernet connection
– Motherboard may not include a NIC
– Onboard NIC may not be working
• Additional connections
– Servers, routers, security devices
```
Network Interface Card (NIC)
257
• Check the motherboard documentation
– Number and type of slots
• Check the adapter card documentation
– Minimum requirements - Hardware, software
– Knowledge base - Any “gotchas?”
– Support forums - What are other people saying?
• You may need to perform a driver installation before
installing hardware
Documentation
258
```
• Cool air is pulled through a personal computer
– Always check for good airflow
• Motherboard layout becomes important
• Component location is key
– Devices, wiring, power
• Many different sizes and styles
– And volume levels
```
Case fans
259
• Designed to cool an entire adapter card
• Can be bulky
– May take additional adapter card space
• Usually seen on high-end graphics cards
On-board fans
260
```
• Standard sizes
– 80 mm, 120 mm, 200 mm, etc.
• Different speeds
– Variable speed
• Different noise levels
– Not all fans sound the same
```
Fan specifications
261
• Dissipate heat through thermal conduction
– Copper or aluminum alloy
• Fins/grid increase surface area
– Heat is then transferred to the cooler air
• They get HOT – don’t touch them!
• Thermal paste creates a good contact between the
chip and the heat sink
Heat sink
262
```
• No fans, no noise - Silent operation
• Specialized functions
– Video servers, TV set top box,
satellite receiver, media server
• Functions are very controlled
– Carefully measured thermal tests
• Low-power components - Heat sinks
```
Fanless / passive cooling
263
```
• Thermal grease, conductive grease
– Thermally conductive adhesive
• Place between the heat sink and the component
– Improves thermal conductivity
– Moves the heat away from the component
• A little bit goes a long way
– Pea-sized application
```
Thermal paste
264
• Conduct heat without the mess - Cut to size and install
• Easy to use - Won’t leak and damage components
• Almost as effective as thermal paste
– But still very good
• Not reusable - Remove and replace
Thermal pad
265
```
• Coolant is circulated through a computer
– Not a new concept
– Automobiles, mainframe computers
• High-end systems
• Gaming, graphics
• Overclocking
```
Liquid cooling
266
```
• Computer uses DC voltage
– Most power sources provide AC voltage
• Convert 120 V AC or 240 V AC
– To 3.3 V DC, 5 V DC, and 12 V DC
• You’ll know when this isn’t working
– An important component
```
Computer power supply
267
• Ampere (amp, A) – The rate of electron flow
past a point in one second
– The diameter of the hose
• Voltage (volt, V)Electrical “pressure”
pushing the electrons
– How open the faucet is
Amp and volt
268
• Watt (W) – Measurement of real power use
– volts * amps = watts
– 120V * 0.5A = 60W
Power
269
```
• Different voltages
– For different components
• Positive and negative voltage
– Voltage is a difference in potential
– The electrical ground is a common reference point
– Depends on where you measure from
• At the front door of your house
– The second floor is +10 feet
– The basement is -10 feet
• +12 V
– PCIe adapters, hard drive motors, cooling fans,
most modern components
• +5 V
– Some motherboard components
– Many components are now using +3.3 V
• +3.3 V
– M.2 slots, RAM slots, motherboard logic circuits
• +5 VSB
– Standby voltage
• 12 V
– Integrated LAN
– Older serial ports
– Some PCI cards
• -5 V
– Available for ISA adapter cards
– Most cards didn’t use it
– Today’s motherboards
don’t have ISA slots
```
Power supply output
270
• Alternating current (AC)
– Direction of current constantly reverses
– Distributes electricity efficiently over long distances
– Frequency of this cycle is important
– US/Canada – 110 to 120 volts of AC (VAC), 60 hertz (Hz)
– Europe – 220-240 VAC, 50 Hz
• Direct current (DC)
– Current moves in one direction with a constant voltage
Current
271
```
• Voltage varies by country
– US/Canada – 120 volts of AC (VAC), 60 hertz (Hz)
– Europe – 230 VAC, 50 Hz
• Manually switch between 120 V and 230 V
– Get your meter!
– Or use an auto-switching power supply
• Don’t plug a 120 V power supply into
a 230 V power source!
```
Dual-voltage input options
272
```
• Main motherboard power
– Provides +3.3 V, +/-5 V, and +/- 12 V
• 20 pin connector was the original ATX standard
– 24 pin was added for PCI Express power
• You can connect a 24-pin connector to
a 20-pin motherboard
– Some cables are 20-pin + 4-pin
```
24-pin motherboard power
273
```
• Two (or more) power supplies
– Internal to the server
• Each power supply can handle 100% of the load
– Would normally run at 50% of the load
• Hot-swappable
– Replace a faulty power supply without
powering down
```
Redundant power supplies
274
```
• Fixed connectors
– Connected to the power supply
– May have too many connectors
– May not have enough
• Modular
– Add cables as needed
– Fewer leftover wires,better airflow
– A bit more expensive
```
Power supply connectors
275
```
• Multifunction devices (MFD)
– Printer
– Scanner
– Fax (yes, really)
– Network connection
– Phone line connection
– Print from web
• There are a lot of things that can go wrong
– You’re going to fix them
```
Multifunction devices
276
```
• PCL (Printer Command Language)
– Created by Hewlett-Packard
– Commonly used across the industry
• PostScript
– Created by Adobe Systems
– Popular with high end printers
• Make sure the drivers match the printer
– PCL printer, PCL driver
– PostScript printer, PostScript driver
– Wired device sharing
• USB type B
– The most common connector
– USB Type B on the printer,
USB Type A on the computer
• Ethernet - RJ45 connector
• May include more than one option
```
PCL or PostScript
277
```
• Bluetooth
– Limited range
• 802.11 Infrastructure mode
– Many devices using an access point
• 802.11 Ad hoc mode
– No access point
– Direct link between wireless devices
```
Wireless device sharing
278
```
• Printer share
– Printer is connected to a computer
– The computer shares the printer
– Computer needs to be running
• Print server
– Print directly to the printer
– Jobs are queued on the printer
– Jobs are managed on the printer
– Web-based front-end
– Client utility
```
Sharing the printer
279
```
• Duplex
– Save paper
– Print on both sides of the page without manually
flipping over the paper
– Not all printers can do this
• Orientation
– Portrait vs. Landscape
– The paper doesn’t rotate
– The printer compensates
• Tray settings
– Printers can have multiple trays
– Plain paper, letterhead, etc.
– Choose the correct tray in the print dialog
• Quality
– Resolution / Color, greyscale / Color saving
```
Configuration settings
280
• User authentication
– Everyone can print
– Set rights and permissions
– Printing vs. managing the printer
Printer security
281
– Authenticate when using the printer
– Your job doesn’t print until you use
your employee badge
– Quick and easy
Badging
282
– Cost management
– Security monitoring
– Event Viewer / System Events
– May be built into the printer or print server
• Audit logs
283
```
• Different form factors
– All-in-one multifunction device
– Standalone flatbed
• May include an ADF
– Automatic Document Feeder
– Multiple pages
```
Flatbed scanner
284
```
• Scan to email
– Scans are sent to your inbox
– Large scans can fill up your mailbox
• Scan to folder
– Using SMB (Server Message Block)
– Send to a Microsoft share
• Scan to cloud
– Cloud storage account
– Google Drive, Dropbox, etc.
```
Network scan services
285
• Combine a laser, high voltage, charged ions,
powdered ink, heat, and paper
• Very high quality
• Fast printing speeds
• Very complex, many moving parts, requires on-printer
memory and messy on the inside
Laser printer
286
• Image is drawn onto a photosensitive drum
– “Painted” with a laser
• Picks up toner - Transfers toner to the paper
• Can be separate from the toner cartridge or combined
Imaging drum
287
• Heat and pressure - Melt plastic toner powder
| – Permanently bond toner to paper
Fuser assembly
288
```
• Color laser printers
– Cyan, yellow, magenta, black
• Four separate toner cartridges
• Image is transferred from all cartridges to the single belt
– And then to a single transfer roller
```
Transfer belt and roller
289
• Pickup paper - Should be a single page at a time
– Problems if no paper is picked up
or multiple sheets are picked
• Should be periodically cleaned or replaced
Pickup rollers
290
• Pull just the top sheet from the paper tray
– Not multiple sheets
• Small and inexpensive - Easy to clean or replace
Separation pad
291
```
Printers usually print on a single side
– Not both sides simultaneously
• Printing on both sides is a two step process
– Print side one, print side two
• You need mechanisms to “flip” the page
– Automatically
• Can be built-in to the printer
• Or available as an add-on
```
Duplexing assembly
292
```
Step 1: Processing
• Build the entire page in memory
Step 2: Charging
• Prepare the drum with a
negative electrostatic charge
Step 3: Exposing
• Write the image with the laser
Step 4: Developing
• Add toner to the charged areas
of the imaging drum
Step 5: Transferring
• Move the toner from
the drum to the paper
Step 6: Fusing
• Heat and pressure
Step 7: Cleaning
• Remove excess toner
```
Laser Printer Printing Process
293
```
• Look for the messages
– Low doesn’t mean empty
• The toner can also contain the OPC drum
– Organic Photoconductor drum
– Sensitive to light; keep it in the bag
• Power down the printer
– Safety first
• Remove packing strips from the new drum
– Replace it with the old
```
Replacing the toner cartridge
294
```
• Laser printers wear out
– All those moving parts
– Heat and pressure
• Standard maintenance kits
– Replacement feed rollers, new fuser unit, etc.
• When to perform maintenance?
– Check the printer’s page counter
• Power down and replace the components
– Fuser units are HOT
• Reset the page counter when you’re done!
```
Laser printer maintenance kit
295
```
• Look for the messages
– Low doesn’t mean empty
• The toner can also contain the OPC drum
– Organic Photoconductor drum
– Sensitive to light; keep it in the bag
• Power down the printer - Safety first
• Remove packing strips from the new drum
– Replace it with the old
```
Replacing the toner cartridge
296
• Different toner cartridges print with different densities
– Some dark, some light
• Laser printer calibration can adjust the density
– Makes it looks perfect
• Can be automated or a manual process
– Every printer is different
– Check the printer manual
Laser printer calibration
297
• Laser printers are dirty - All that toner and paper dust
• Check the manufacturer’s recommendations
– Water, isopropyl alcohol (IPA)
– Don’t use harsh chemicals!
• Outside - Damp cloth
• Inside - Wipe dust away
– Don’t use a normal vacuum cleaner or compressed air
– Wash off skin with cold water
– Clean rollers with IPA
Laser printer cleaning
298
```
• Relatively inexpensive technology
• Quiet
• High-resolution
• Expensive ink
– Proprietary
• Eventually fades
• Clogs easily
```
Inkjet (ink-dispersion) printer
299
Ink cartridge
• Place drops of ink onto a page
– Pulled from a set of cartridges
• CMYK - Cyan, Magenta, Yellow, Key (black)
300
• Some consumer printers integrate the print head
into the ink cartridge
– Change the cartridge, get a new print head
• Others separate the ink cartridge from the print head
Print head
301
```
• Pick up and feed paper through the printer
– Must be clean and not worn
• Duplexing
– Print on both sides of the paper
– Included with some printers
```
Feed rollers
302
• Ink cartridges are moved over the paper
– Carriage may include its own print head
• Belt moves the carriage back and forth
– Another moving part
Carriage and belt
303
```
• Align nozzles to the paper
– Lines should be crisp
– Colors should align
• Printer includes a calibration option
– May need to make minor adjustments
```
Inkjet printer calibration
304
• Small droplets of ink - And small holes in a print head
• Clogged heads is a big issue
– Many printers automatically clean every day
– Output has streaks or sections of missing color
• Cleaning process can be started manually
– Only takes a few minutes
• Some print heads/cartridges can be removed
– Manually cleaning may help
Cleaning print heads
305
```
• Usually separate colors
– Cyan, Magenta, Yellow, and Key (CMYK)
– Some cartridges will combine these
• Takes seconds to replace
– Takes a few minutes to calibrate and
prepare the cartridge
• Recycle the empty cartridge - All plastic
```
Replacing inkjet cartridges
306
```
• Align nozzles to the paper
– Lines should be crisp
– Colors should not overlap
• Printer includes a calibration option
– May need to make minor adjustments
```
Inkjet printer calibration
307
```
• Lots of turns and twists
– A jam is inevitable
• Remove tray paper
– Any loose paper
• Remove paper from the path
– Firm pressure, don’t rip
• Check for any scraps of paper
• Remove all loose paper
```
Clearing jams
308
```
• White paper
– Turns black when heated
– No ink!
• VERY quiet
– Almost silent
• Paper is sensitive to light and heat
– And clear tape
```
Thermal printer
309
• Full-length heating element
| – No moving print head
Heating element
310
```
• Paper covered with a chemical
– Changes color when heated
• Cash registers, credit card terminals
– And quiet areas
• Looks like normal paper
– Feels a bit different
```
Thermal paper
311
```
• Relatively inexpensive
– But impossible to substitute
• Different sizes
– Not like laser printer paper - Keep a list
• Actual replacement process is easy
– Simple paper feed
– Small device
```
Thermal paper replacement
312
```
Liquid cleaner
– Isopropyl alcohol (IPA)
– Get a cleaning pen
– Check manufacturer’s recommendations
• Swab gently - Usually small areas
• Use a cleaning card
– Cleans the head and paper pathways
```
Cleaning the heating element
313
```
• Relatively small amount
– Paper bits and dust
– No toner!
• Blow out the printer
– Take it outside
• Wipe it out
– Damp cloth
• Avoid using a vacuum
– Unless it’s designed for computers
– Resists static buildup/discharge
```
Removing debris
314
```
• Print head with a small matrix of pins
– Presses against a ribbon to make a mark on paper
• Good for carbon/multiple copies
• Low cost per page
• NOISY
• Poor graphics
• Relatively niche use cases
```
Dot-matrix (impact) printers
315
• Moves back and forth
– Pins hit ribbon and paper
• One matrix - Must move across the page to print
Dot-matrix printer head
316
• Fabric
– One long ribbon - Never ending circle
• Easy to replace - Once single unit
• Proprietary size - Specific to printer model
Printer ribbon
317
• Paper pulled through with holes on the side of the paper
– Instead of using friction
• Continuous paper feed
– Perforations between pages
• Holes have to line up perfectly
– Tractor paper can be perforated to remove holes
Tractor feed
318
• Single ribbon - Self-contained - One long circle
• Replace when ink becomes too light
– Ink is eventually consumed
• Designed to be modular - Replace in less than a minute
Printer ribbon replacement
319
• Takes a lot of abuse - Directly hits the ribbon and paper
• Gets hot - Watch your fingers
– Another modular part - Look for a release lever or bar
• Replace with the ribbon for the best effect
– The output should look perfect
Print head replacement
320
```
• Single ribbon
– Self-contained - One long circle
• Replace when ink becomes too light
– Ink is eventually consumed
• Designed to be modular - Replace in less than a minute
```
Printer ribbon replacement
321
```
• Takes a lot of abuse
– Directly hits the ribbon and paper
• Gets hot - Watch your fingers
– Another modular part
– Look for a release lever or bar
• Replace with the ribbon for the best effect
– The output should look perfect
```
Print head replacement
322
```
• Not as easy as a laser printer
– Paper must feed perfectly into holes
– Tractor feed
• Forms must be positioned correctly
– Text needs to fit a predefined space
• Paper must feed without constraint
• Make sure nothing is in the way
```
Replacing paper
323
```
“Print” in three dimensions
– Create a 3D item based on an electronic model
• Additive manufacturing
– Build in layers to create the object
– No machining process required
• Rapid prototyping
– Design and create relatively quickly and inexpensively
• Deploy designs anywhere in the world
– Or into space
```
3D printers
324
```
Fused Deposition Modeling (FDM)
– Melt filament to print 3D objects
– This is probably the printing type you’ve seen
• Print a layer, move up,print another layer
– Watch the printer create the object
• Good all-around printer
– Larger print bed than resin printers
– Easy to manage filament
– Minimum of mess
– Fewer disposal issues
```
Filament printing
325
```
• Stereolithography (SLA) 3D Printing
– Smooth and finely detailed 3D prints
• Resin is hardened using a light source
– Ultraviolet light or a laser
– Layers are added to the bottom
– Entire print hangs from the build platform
• Resin must be handled properly
– Wear protective gear
– Take unused resin to your local
hazardous materials disposal
```
Resin printing
326
```
• A flat adhesive surface
– The foundation of a 3D print
– Everything builds on that first layer
• Needs to be level and clean
– Prints “stick” to the bed
• Filament printing
– The print bed is the printing surface
– Many different print bed options
• Resin printing
– The “bed” is the location where the resin is
hardened by the UV light
```
The print bed
327
```
• More than just a server hosted elsewhere
– Extend the management of applications and services
• Deploy an infrastructure in minutes
– Create and tear down as you need
• International scope
– Deploy in specific parts of the world
• Use only the required resources
– Cost is based on the amount of use
```
Cloud computing
328
```
• Private
– Your own virtualized local data center
• Public
– Available to everyone over the Internet
• Hybrid
– A mix of public and private
• Community
– Several organizations share the same resources
```
Cloud deployment models
329
• Sometimes called Hardware as a Service (HaaS)
– Outsource your equipment
• You’re still responsible for the management
– And for the security
• Your data is out there, but more within your control
– Web server providers
Infrastructure as a service (IaaS)
330
```
• On-demand software
– No local installation
– Why manage your own email distribution?
Or payroll?
• Central management of data and applications
– Your data is out there
• A complete application offering
– No development work required
– Google Mail, Microsoft 365
```
Software as a service (SaaS)
331
• No servers, no software, no maintenance team, no HVAC
– Someone else handles the platform,
you handle the development
• You don’t have direct control of the data,
people, or infrastructure
– Trained security professionals are watching
– Choose carefully
• Put the building blocks together
– Develop your app from what’s available on the platform
– SalesForce.com
Platform as a service (PaaS)
332
```
• Internal cloud
– No resources are shared
– Build your own cloud
– Pay for everything up front
– No ongoing costs
• External cloud
– Share resources with a public cloud
– Underlying infrastructure owned by a third-party
– Cost may be metered or up-front
```
Shared resources
333
```
Metered cloud services
– You pay for what you use
– Cost to upload
– Cost to store
– Cost to download
• Non-metered
– You pay for a block of storage
– No cost to upload
– No cost to download
```
Metered and non-metered
334
```
• Rapid elasticity
– Scale up and scale down as needed
– Seamless to everyone
– The cloud enables instant resource provisioning
• High availability
– Systems are always available
– Redundancy provides availability
• File synchronization
– Information can be duplicated across cloud locations
```
Cloud computing characteristics
335
```
One computer, many operating systems
– macOS, Windows 11, Linux Ubuntu,
all at the same time!
• Separate OS, independent CPU, memory, network, etc.
– But really one computer
• Host-based virtualization
– Your normal desktop plus others
• Standalone server that hosts virtual machines
– Enterprise-level
• Been around since 1967
– IBM mainframe virtualization
```
Virtualization
336
• Need to run different application versions
on the same system
– Run each application instance in a separate VM
• Application only runs on a previous OS version
– Create a VM with the older operating system
Legacy software and operating systems
337
• Windows / macOS / Linux doesn’t do everything
– Each OS has strengths and weaknesses
• Run different operating systems at the same time
– Move between each OS seamlessly
– No rebooting
• Save time and resources
– One physical computer
Cross-platform virtualization
338
```
• Virtual Machine Manager
– Manages the virtual platform and
guest operating systems
• May require a CPU that supports virtualization
– Can improve performance
• Hardware management
– CPU, networking, security
```
The hypervisor
339
• Every guest is self-contained - Like a real computer
• Use traditional security controls
– Host-based firewall, Anti-virus, anti-spyware
• Watch out for rogue virtual machines (VMs)
– The bad guys try to install their own system
– You’re in big trouble
• Self-contained VMs provided by 3rd parties
can be dangerous
– You have no idea what’s running on there
Guest operating system security
340
• Most client-side virtual machine managers have
their own virtual (internal) networks
• Shared network address
– The virtual machine shares the same IP address
as the physical host
– Uses a private IP address internally
– Uses NAT to convert to the physical host IP
• Bridged network address
– The VM is a device on the physical network
• Private address
– The VM does not communicate outside of
the virtual network
Network requirements
341
• Change control
– A formal process for managing change
– Avoid downtime, confusion, and mistakes
– Corporate policy and procedures
• Nothing changes without the process
– Plan for a change
– Estimate the risk associated with the change
– Have a recovery plan if the change doesn’t work
– Test before making the change
– Document all of this and get approval
– Make the change
Change management
342
```
• Information gathering
– Get as many details as possible
– Duplicate the issue, if possible
• Identify symptoms
– May be more than a single symptom
• Question users
– Your best source of details
• Determine if anything has changed
– Who’s in the wiring closet?
• Approach multiple problems individually
– Break problems into smaller pieces
• Backup everything
– You’re going to make some changes
– You should always have a rollback plan
• What else has changed?
– The user may not be aware
– Environmental changes
– Infrastructure changes
• There may be some clues
– Check OS log files
– Applications may have log information
```
Identify the problem
343
```
• Start with the obvious - Occam’s razor applies
• Consider everything - Even the not-so-obvious
• Make a list of all possible causes
– Start with the easy theories
– And the least difficult to test
• Research the symptoms
– Internal knowledge base
– Google searches
```
Establish a theory
344
```
• Confirm the theory
– Determine next steps to resolve problem
• Theory didn’t work?
– Re-establish new theory or escalate
– Call an expert
• The theory worked!
– Make a plan…
```
Test the theory
345
```
• Build the plan
– Correct the issue with a minimum of impact
• Refer to vendor instructions
– Knowledge base, support articles
– Documentation and manuals
• Identify potential effects
– Every plan can go bad
– Have a plan B
– And a plan C
```
Create a plan of action
346
• Fix the issue
– Implement during the change control window
• Escalate as necessary
– You may need help from a 3rd party
Implement the solution
347
```
• It’s not fixed until it’s really fixed
– The test should be part of your plan
– Have your customer confirm the fix
• Implement preventative measures
– Let’s avoid this issue in the future
```
Verify full system functionality
348
```
• It’s not over until you build the knowledge base
– Don’t lose valuable knowledge!
• What action did you take?
– What outcome did it have?
• Consider a formal database
– Help desk case notes
– Searchable database
```
Document findings
349
• Test major system components before booting
the operating system
– Main systems (CPU, CMOS, etc.)
– Video
– Memory
• Failures are usually noted with beeps and/or codes
– BIOS versions can differ, check your documentation
• Don’t bother memorizing the beep codes
– They’re all different between manufacturers
– Know what to do when you hear them
POST (Power On Self Test)
350
```
• Blank screen on boot
– Listen for beeps
– Bad video, bad RAM, bad CPU
– BIOS configuration issue
• BIOS time and setting
– Maintained with the motherboard battery
– Replace the battery
• Attempts to boot to incorrect device
– Set boot order in BIOS configuration
– Confirm that the startup device has
a valid operating system
– Check for media in a startup device
```
POST and boot
351
• Windows Stop Error or Blue Screen of Death
• Contains important information
– Also written to event log
• Useful when tracking down problems
– Sometimes more useful for manufacturer support
Crash screens
352
• Startup and shutdown BSOD
– Bad hardware, bad drivers, bad application
• Use Last Known Good, System Restore, or Rollback Driver
– Try Safe Mode
• Reseat or remove the hardware - If possible
• Run hardware diagnostics
– Provided by the manufacturer
– BIOS may have hardware diagnostics
Bluescreens and spontaneous shutdowns
353
```
• The macOS X Spinning Wait Cursor
– Feedback that something is happening
• The spin starts, but it never stops
– You never get back control of your computer
• Many possible reasons
– Application bug
– Bad hardware
– Slow paging to disk
• Restart the computer
– There may be details in the console logs
```
The spinning ball of death
354
• Is the monitor connected?
– We wouldn’t ask if it wasn’t a common solution
– Check both power and signal cable
• Input selection on monitor - HDMI, DVI, VGA, etc.
• Image is dim - Check brightness controls
• Swap the monitor
– Try the monitor on another computer
• No video after Windows loads
– Use VGA mode (F8)
Black screen
355
```
• No power
– No power at the source
– No power from the power supply
– Get out your multimeter
• Fans spin - no power to other devices
– Where is your fan power connected?
– No POST - bad motherboard?
– Case fans have lower voltage requirements
– Check the power supply output
```
No power
356
```
• Task Manager
– Check for high CPU utilization and I/O
• Windows Update
– Latest patches and drivers
• Disk space
– Check for available space and defrag
• Laptops may be using power-saving mode
– Throttles the CPU
• Anti-virus and anti-malware
– Scan for bad guys
```
Sluggish performance
357
```
• Heat generation
– CPUs, video adapters, memory
• Cooling systems
– Fans and airflow
– Heat sinks
– Clean and clear
• Verify with monitoring software
– Built into the BIOS
– Try HWMonitor
– http://www.cpuid.com/
```
Overheating
358
```
• Electrical problems
– The smoke makes everything work
• Always disconnect power
– There should never be a burned odor
• Locate bad components
– Even after the system has cooled down
– Replace all damaged components
```
Smoke and burning smell
359
```
• No warning, black screen
– May have some details in your Event Viewer
• Heat-related issue
– High CPU or graphics, gaming
– Check all fans and heat sinks
– BIOS may show fan status and temperatures
• Failing hardware
– Has anything changed?
– Check Device Manager, run diagnostics
• Could be anything
– Eliminate what’s working
```
Intermittent shutdown
360
```
• Application stops working
– May provide an error message
– May just disappear
• Check the Event Log
– Often includes useful reconnaissance
• Check the Reliability Monitor
– A history of application problems
– Checks for resolutions
• Reinstall the application
– Contact application support
```
Application crashes
361
* Computers should hum, not grind
* Rattling - Loose components
* Scraping - Hard drive issues
* Clicking - Fan problems
* Pop - Blown capacitor
Grinding noises
362
```
• System completely stops
– Completely. Usually not much in the event log
– Similar to unexpected shutdowns
• Check for any activity
– Hard drive, status lights, try Ctrl-Alt-Del
• Update drivers and software patches
– Has this been done recently?
• Low resources - RAM, storage
• Hardware diagnostics may be helpful
```
Lockups
363
• How far does the boot go before rebooting?
– BIOS only? OS splash screen?
• Bad driver or configuration
– F8, “Boot from last known working configuration”
• Try F8, Safe Mode
– If system starts, disable automatic restarts
in System Properties
• Bad hardware
– Try removing or replacing devices
– Check connections and reseat
Continuous reboots
364
• Bad motherboard battery
– Often a “button” style battery
• A bad battery will require a BIOS configuration or
date/time configuration on every boot
• On older systems, can reset the BIOS configuration
by removing the battery
– Newer computers use a jumper
Inaccurate system date/time
365
```
• Read/write failure
– “Cannot read from the source disk”
• Slow performance
– Constant LED activity - Retry...retry...retry
• Loud clicking noise
– The click of death
– May also include grinding and scraping
```
Storage failure symptoms
366
• Get a backup - First thing - a bad drive is bad
• Check for loose or damaged cables
• Check for overheating
– Especially if problems occur after startup
• Check power supply
– Especially if new devices were added
• Run hard drive diagnostics
– From the drive or computer manufacturer
– Preferably on a known-good computer
Troubleshooting disk failures
367
```
• Drive not recognized, Boot Device Not Found
– Lights (or no lights)
– Beeps
– Error messages
• Operating system not found
– The drive is there
– Windows is not
```
Boot failure symptoms
368
```
• Check your cables
– Physical problem
• Check boot sequence in BIOS
– Check for removable disks (especially USB)
– Check for disabled storage interfaces
• For new installation, check hardware configuration
– Data and power cables
– Try different SATA interfaces
• Try the drive in a different computer
```
Troubleshooting boot failures
369
```
• Hard drives are mechanical devices
– They will eventually fail
• Repairs are difficult and expensive
– Dust-free environment
– Not always successful
• An SSD may simply stop working
– Sometimes can read but not write
• Data becomes unavailable or corrupted
– Can be impossible to recover
• ALWAYS HAVE A BACKUP
```
Data loss/corruption
370
• Missing or faulty RAID controller
RAID not found
371
• Each RAID is different
| – Don’t start pulling drives until you check the console!
RAID stops working
372
• Self-Monitoring, Analysis, and Reporting Technology
– Use third-party utilities
• Avoid hardware failure - Look for warning signs
• Schedule disk checks - Built-in to most drive arrays
• Warning signs - Replace a drive
S.M.A.R.T.
373
• A lot happens when reading or writing data
– Memory access, communication across the bus,
spinning drive access, writing or reading the data to
the storage device, etc.
• Delays can occur anywhere along the way
– Need a way to measure storage device access
• Input/output operations per second (IOPS)
– A broad metric of maximum performance
• Useful for comparing storage devices
– Hard drive: 200 IOPS
– SSD: 1,000,000 IOPS
Extended read/write times
374
• OS boots normally
– Other drives not shown - Check the BIOS
• Internal drives
– Bad drive or disconnected cable
• External drives
– No power to the drive or bad cable connection
• Network shares
– Shared drives can be connected during startup
– Option to reconnect at sign-in
– Connected with login script
Missing drives in OS
375
```
Is it connected?
– We wouldn’t ask if it wasn’t a real solution
– Check both power and signal cable
• Input selection on monitor
– HDMI, DVI, VGA, etc.
• Image is dim
– Check brightness controls
• Swap the monitor
– Try the monitor on another computer
• No video after Windows loads
– Use VGA mode (F8)
```
No video image
376
```
Flickering, color patterns incorrect
– You can almost work with this
• Check the cable pins
– Especially if missing a color
• Distorted image and geometry
– Check the OS refresh rate and resolution settings
– Need to match the display specifications
– Check or replace cable
• Disable hardware acceleration
– Troubleshoot with the software drivers
```
Image quality problems
377
• An LCD display is fixed
– The number of pixels doesn’t change
• A display looks best when the video settings match
a display’s native resolution
– A mismatch can cause distortion
• If changing the display resolution,try using a multiple
of the native resolution
– 2560 x 1600 is the same ratio as 1920 x 1200
Native resolution
378
```
• A problem across all monitor types
– Some displays will pixel-shift
– You probably won’t notice it
• LCDs have “image sticking”
– Try to remove by displaying a white screen for an
extended period
```
Burn-in
379
```
• Always black
– A manufacturing defect
• This probably isn’t a problem on your side
– Not a cable or power issue
• Clean the monitor screen
– Damp cloth
• You’ll have to replace the monitor
– No other option
```
Dead pixels
380
```
• Check the video cable connections
– A loose cable will cause loss of signal
• Replace the video cable
– Usually a quick fix
• The problem could be with the monitor
– Try switching the display
• Confirm the display settings in the operating system
– May not match the monitor
```
Flashing screen
381
```
Colors may not be properly represented
– Too much red, green, blue, yellow, etc.
• Monitor settings
– Tint
– Custom color presets
– Factory Reset
• Driver configuration
– Color tint
• OS configuration - Very blue
– Night light settings
```
Incorrect color display
382
```
• Many monitors include speakers
– No sound, low volume
• Monitor may have audio controls
– Check volume levels and mute status
• Confirm audio input over HDMI, DisplayPort, or
Thunderbolt
– Check the HDMI audio output in the OS
• The monitor may support other audio input interfaces
– Check for audio jacks
```
Audio issues
383
```
• Monitor video settings
– Brightness
– Contrast
• Check the OS
– Auto-dimming
– Dim on battery power
– Driver settings
• Backlight failure
– Some or all of the light
– May only be a section of the screen
```
Dim image
384
```
• Large screen projection
– Conference rooms, large gatherings
• Not always LCD
– But common to see LCD
• Metal-halide lamp
– Very bright (very hot) light
– Relatively expensive
– (~ $35 to $350+ US)
• Always let bulbs cool
– Fan will run after shutting off
– Keep it plugged in
• Intermittent projector shutdown
– No light output
– Fans may continue to run
• Cooling issue
– Fans constantly cool the bulb
– Shuts down if temperatures are high
• Check the airflow
– Remove any blockages
– Clean dust from the air filters and external
air input/output
```
LCD projector troubleshooting
385
```
• Replace aging battery
– There’s only so many recharges
• Bad reception
– Always searching for signal
– Airplane mode on the ground
• Disable unnecessary features
– 802.11 wireless, Bluetooth, GPS
• Check application battery usage
– iOS and iPadOS: Settings/Battery
– Android: Settings/Battery
```
Poor battery health
386
```
• Buildup of gas
– Designed to self-contain
– Do NOT open the battery packet/container
– Significant fire risk
– You’ll be sorry
• Faulty battery
– Stop using immediately
– Dispose of properly
• Device can be damaged
– Better than having a fire
```
Swollen battery
387
```
• Time for a backup - Do this first!
• Replace the screen - No easy fixes
• The glass is sharp
– Screen protectors can help
– Use clear tape until repaired
```
Broken screen
388
```
• Check everything in the charging process
– Cables, interfaces
• Check the cable interface
– Remove any obstructions
• Check the cable
– Don’t use frayed or damaged cables
– Try a known-good cable
• Verify the power adapter
– Check with a multimeter
```
Improper charging
389
```
• Cellular or Wi-Fi
– Location, location, location
• Cellular
– Signal strength
– Location matters
– Outdoor connectivity may be better
• Wi-Fi
– Limited range
– Interference can limit throughput
– May need a channel/frequency configuration change
```
Poor or no connectivity
390
```
• Many phones have a Liquid Contact Indicator (LCI)
– Turns color when liquid has been present
• Power down the phone
– Don’t power it back on. Don’t do it.
• Remove the case, cards, back, and battery
– If possible
• Putting the phone in a bag of rice doesn’t
actually work very well
– Silica gel is better
• Leave it alone
– Don’t turn it on
– Do not charge the phone
– Don’t connect it to power
– Don’t press any keys
– Don’t heat the phone
– Don’t move it around
• Wait at least a day
– Or until the phone appears to be dry
– And then perhaps a few hours after that
• Once you’re sure, power it on
– Hope for the best
```
Liquid damage
391
```
• Phone will automatically shut down
– Avoid overheating damage
• Charging/discharging the battery, CPU usage,
display light
– All of these create heat
• Check app usage
– Some apps can use a lot of CPU
• Avoid direct sunlight
– Quickly overheats
```
Overheating
392
• Touchscreen completely black or
not responding to input
– Screen presses do not register
• Apple iOS reset
– Press power button, slide to power off,
press power button
– Hold down power button and Home|Volume
for 10 seconds
• Android device restart
– Remove battery, put back in, power on
– Hold down power and volume down until restart
– Some phones have different key combinations
– Some phones do not have a key-based reset
Digitizer issues
393
• External interface - Charging and data transfer
• Rough handling and accidents
– Damages the interface
• Not charging - Look closely
• Not modular - Requires a system board replacement
Physically damaged ports
394
```
• Always a concern
– Even on mobile devices
– The device type doesn’t matter
• Look for symptoms
– Unusual apps, large data transfers, pop up messages,
high CPU usage, device overheating, excessive
battery use
• Try a security app or scanner
– Identify malware infections
```
Malware
395
```
• Random input or cursor moves without
touching the device
– Common on older screens
• Use a touch calibration app
– Requires user input
– Touch certain areas of the screen
• The system will adjust to the new calibration parameters
– No more drif
```
Cursor drif
396
• Print or scan a test page
– Built into Windows, not the application
• Use diagnostic tools
– Web-based utilities built into the printer
– Vendor specific
– Generic utilities
Testing the printer
397
• Lines down the printed page
– Inkjet: Clean print heads
– Laser: Check for scratched photosensitive drum
• Faded prints, blank pages - Low toner or ink
• Double/echo images or speckling
– Laser printer optical drum not cleaned properly
– Ghost or “shadow” from previous drum rotation
Bad output
398
```
• Bad printer driver / wrong model
– Incorrect page description language
(PCL or PostScript?)
• Verify the printer functionality
– Check with a test page
• Bad application
– Check the output
– Upgrade the application
```
Garbled print
399
Laser printer output smudges everywhere
– Toner sticks to everything
• Toner not fused to the paper
– Toner should be permanently melted and pressed
– May not be hot
• Fuser problem - Replace the fuser assembly
Toner not sticking to the paper
400
Print a letter size page
– Accidentally send it to a legal size paper tray
• Printer stops and shows a message
– Gives you a chance to fix the issue
• Tray selection is provided during the printing process
– Try printing again
– Change the defaults in the printer configuration
Incorrect paper size
401
```
• Careful when removing
– Don’t rip the paper
– Don’t damage internal components
• Paper not feeding or misfeeds multiple pages
– Check the tray
– Pickup rollers are part of a laser printer maintenance kit
• Creased paper
– Problems in the paper path
– Check the paper weight
```
Paper jam
402
• Corrupted print jobs
– Print spooler will crash
– Most spooler configuration will automatically restart
• Problems are logged
– Windows Event Viewer,Windows-PrintService
• One job may be causing the issue
– Monitor the queue for details
Multiple prints pending in queue
403
• The output colors aren’t the same as the display
– Important for publishing and color printing
• Calibrate the monitor
– A third-party calibration tool will help
• Check the paper
– Bright white paper provides good color representation
• Calibrate the printer
– The proper amount of ink and toner
Incorrect color settings
404
• Never a good sound from your printer
– The ink is already manufactured
• Something is not operating properly
– Paper jam - Carriage is stalled or jammed
• Each printer has a different process
– Check the manuals for removing paper jams
– Some inkjet printers have a particular process
• May require additional maintenance
– Or replace the printer
Grinding noises
405
```
• Finishing happens after the ink or
toner has been applied
– Collate, binding, etc.
• Staple jams
– Larger printers will collate and staple groups of papers
– Each printer manufacturer has a different removal
process
• Incorrect hole punch location
– Verify with the printer driver
– May require a driver update
```
Finishing issues
406
Print a portrait page - Get a landscape print
• Check the settings when printing
– Controlled by the print driver
– May require a driver update
• The printer also has a default setting
– Check the settings on the printer console
Incorrect page orientation
407
```
• Do you have a link light?
– Is it plugged in?
• Ping loopback (127.0.0.1)
– Is the protocol stack working?
– Availability and intermittent connectivity
• Ping local IP address
– Checks local configuration, adapter, and link signal
• Ping default gateway
– Connectivity on the local network
• Ping devices on router’s other side
– 8.8.8.8 or 9.9.9.9
```
No network connectivity
408
```
• Interference
– Something else is using our frequency
• Signal strength
– Transmitting signal, transmitting antenna,
receiving antenna, etc.
• Incorrect channel
– Usually automatic; look for manual tuning
• Bounce and latency
– Multipath interference; flat surfaces
• Incorrect access point placement
– Locate close to the users
```
Intermittent wireless connectivity
409
```
• Predictable
– Fluorescent lights
– Microwave ovens
– Cordless telephones
– High-power sources
• Unpredictable
– Multi-tenant building
• Measurements
– Signal to noise ratio (SNR)
– Performance Monitor
```
Wireless interference
410
```
• Signal
– What you want
• Noise
– What you don’t want
– Interference from other networks and devices
• You want a very large ratio
– The same amount of signal to noise (1:1)
would be bad
```
Signal to noise ratio (SNR)
411
• Windows alert in the system tray
– “Limited or No connectivity”
– “No Internet Access”
• Check the local IP address
– An APIPA address will only have local connectivity
• If DHCP address is obtained,perform the ping tests
– Local gateway, remote IP address
Limited or no connectivity
412
• Most real-time media is sensitive to delay
– Data should arrive at regular intervals
– Voice communication, live video
• If you miss a packet, there’s no retransmission
– There’s no time to “rewind” your phone call
• Jitter is the time between frames
– Excessive jitter can cause you to miss information,
“choppy” voice calls
Jitter
413
```
• High speed and low latency
– Real-time applications are demanding
• Check the Internet connection
– A speed test can identify slow links
• Verify the local networking equipment
– An old router can cause significant problems
• View the network performance
– A packet capture would be useful
```
Poor VoIP quality
414
A delay between the request and the response
– Waiting time
• Some latency is expected and normal
– Laws of physics apply
• Examine the response times at every step along the way
– This may require multiple measurement tools
• Packet captures can provide detailed analysis
– Microsecond granularity
– Get captures from both sides
Latency
415
```
• Network interface goes up and down
– Over and over again
• Verify the cable
– Check the wiring
• Move between switch interfaces
– Is the flapping associated with the switch
interface or the device?
• Replace bad hardware or cables
– May require additional purchases
```
Port flapping
