Flashcards in ITM5100-Exam2_deck_5804640 Deck (152):
What type of noise has relatively constant power over all frequencies?
White Noise. 6
What type of noise, added to a digital signal, will change its amplitude?
White Noise. Specifically AWGN (Additive White Gaussian Noise). 6
What naturally occurring noise is stronger at lower frequencies and fades as the frequency increases?
Pink Noise. Low freq noise sources like 60 Hz power will tend to create Pink Noise. 6
What noise (is approximately white noise), but increases as temperature increases?
Thermal Noise. So, when equipment runs hotter it will be noisier. External sources such as the Sun are hot and therefore they are high energy noise sources compared to a dark sky. Thermal noise is eliminated at absolute zero. (-459 deg F or -273 deg K) 6
What could cause impulse noise?
An electrical motor turning on or it may occur within a circuit as the result of the buildup and release of an electrical charge. 6
How can you reduce the effect of impulse noise?
Since it is so hard to predict, it is hard to defend against. You may just have to lower your transmission speed. Shielding is also a great technique for defending against external noise sources. 6
What is a Faraday Cage?
An enclosure made of conducting material that can block external static and non-static electrical fields. 6
What term is used to describe unwanted electromagnetic coupling between two different signal paths?
What are the three the three types of coupling?
Capacitive, Inductive,and Conductive. 6
What is echo?
The reflection of a signal moving through media when it encounters a mismatched impedance. 6
What causes echo?
A splice, physical coupling or improper termination. 6
What is the term used to describe interference from electromagnetic waves traveling through the air, and reflecting off surrounding objects, arriving out of phase at the receiver?
Multipath. Multipath may be predicted in some environments, and this type of noise can be compensated for.6
What is jitter?
The time variation of a periodic signal in relation to a reference. 6
Jitter is not a problem at high data rates
False, it is a bigger problem at high data rates. So, to reduce the effect of jitter, slow down the transmission speed. 6
When an error is detected, what are the three options?
1. Do nothing2. Return an error message to the transmitter and request a retransmission3. Fix the error with an error correcting code. 6
What is a subnet?
A logical division of a network determined by a subnet mask. 7
What is the physical or logical network layout?
What are the two types of topology?
Physical = how devices are connected.Logical = how the data flows. 7
Name 4 types of topology
Can you combine topology types?
Yes. For example, a hub is a combination star (physical) and bus (logical). ZigBee uses a combination start and mesh. 7
What device repeats incoming signals out all ports?
What type of topology does a hub look resemble?
Star (physical) and bus (logical). 7
What network device learns which client devices are connected to which ports by MAC Address and sends traffic to the correct port?
T/F Switches allow several simultaneous conversations without interference.
True. A switch allows several simultaneous full duplex conversations. 7
T/F Switches operate only in half duplex mode.
False, Switches can operate in full duplex mode. 7
T/F Hubs are good for isolating heavy users/talkers on a network.
False. Switches are capable of isolating heavy talkers. Hubs are logical buses and all conversations can be heard by all connected devices. 7
What is a logical subgroup within a LAN that is good for isolating traffic and improving security without requiring the setup of a separate physical network?
VLAN (Virtual LAN). It creates one or more separate virtual/logical networks. 7
What is the domain called that has all nodes hearing all transmissions?
Collision Domain. A bus is an example. 7
What device(s) breaks up collision domains?
Switch & Bridge. A router breaks up ARP broadcast domains. 7
What devices break up Collision domains and broadcast domains
Routers and VLANs. 7
What are the two basic categories of avoiding interference
Contention Based Protocols: CSMA/CD - Carrier sense multiple access collision detectionCSMA/CACarrier Sense multiple access Collision AvoidancePolling protocols: Token Ring. 7
What type of contention based protocol has all devices listen before talking and listen while talking to detect a collision?
CSMA/CD. Carrier sense multiple access with collision detection. 7
What type of contention based media access protocol tries to avoid collisions by pre-planning and using RTS and CTS?
CSMA/CA. CSMA with collision avoidance. This typically used with wireless systems. 7
What topology does Token Ring use?
Ring. Note: CSMA/CD and CSMA/CA are contention-based (first come - first served). Token Ring is an example of an orderly polling scheme in which parties are polled to determine whether they need to send something. 7
What two sub-layers does the Data Link Layer consist of?
The Logical Link Control (LLC) sublayer that allows multiplexing, flow control and error detection.The Media Access Control (MAC) sublayer that provides media access and framing. 7
The IEEE 802 family which includes Ethernet, Token Ring, Wi-Fi, Bluetooth, and ZigBee are all fixed size packet or variable size packet protocols?
IEEE 802 is the variable sized packet family versus ATM which uses a fixed sized packet. 7
POE stands for what?
Power over Ethernet. Unused wires (i.e. not used for data) may be used to carry power to remote devices such as VOIP phones (no separate power cable needed) or remote cameras. 7
What use are High Gain antennas?
The can extend the range of wireless communications. For example, the FCC limits the output power of ISM (Industrial, Scientific, and Medical band) devices, but High Gain antennas can extend their range of operation? 7
What is MIMO?
Multiple Input and Multiple Output. This configuration uses multiple antennas to increase the transmission range and data rate of wireless systems from the newest Wi-Fi to LTE cellular. 7
What is an operating system?
The interface between users/applications and the hardware. The OS Manages/Coordinates activites and sharing of resources. 8
What is defined as: A specialized operating system running on a LAN that allows access to networked resources?
NOS (Network Operating System). 8
What are the two models of the Network Operating System (NOS)
Peer-to-peer and Client-Server. 8
What is a Client-Server model?
One or more servers providing services to one or more clients. The clients do not provide services. 8
In peer to peer networks, what computer can serve another computer?
Any computer can provide service to any other computer. Computers are considered combination clients as well as servers. 8
What is a domain?
A group of servers, users, and resources that share account and security privilege information. Every domain has a primary domain controller that centrally manages account information and security. 8
Which software license allows you to get the source code?
Open Source. 8
What is a General Public License GPL?
An open source license that permits companies to redistribute freely or for profit; modifications must be made available free of charge to all. Ch 8
What is a BSD and MIT license?
Another type of open source license that permits incorporation of open source within proprietary software. The modified source does not have to remain open. 8
What disk configuration creates one large logical disk from several physical disk using a process called striping
RAID 0. 8
In a RAID 0 configuration, what happens if one drive fails?
The entire volume is unusable. Striping increases read/write times, but does not provide redundancy or fault tolerance. 8
What RAID configuration ensures data is mirrored between 2 logical drives allowing for continued operation if the first logical drive fails?
RAID 1. Note: The logical drive can be composed of multiple physical drives. This configuration is call RAID 10 since it is a combination of RAID 1 (mirroring) and RAID 0 (a logical disk). 8
What are the minimum number of disks required for RAID 5?
Three. RAID 5 can combine any number of 3 or more disks. The equivalent of one disk is used in the overhead that allows data reconstruction if one disk fails. 8
What RAID configuration stripes data and parity across all drives?
RAID 5. 8
What three things does RAID 5 provide?
High performance due to striping.Protection against single disk failure.Minimal cost (only one extra physical disk is required). 8
What type of network is primarily fiber optic?
Metropolitan Area Networks (MANs) use fiber because they require high speed and long range. 9
What us the largest most well known WAN
What is a leased line?
A permanent point to point connection. It is permanent in the sense that it does not need to be set up like a dial-up line. It is always ready. (examples: HDLC or SDLC.) 9
What is a circuit switched network?
Semi-permanent (dial up) point to point connection (examples: ISDN or PPP). 9
What is a packet switched network?
Data is broken into packets and each packet can take a different network path. The packets need to be ordered and reassembled at the destination. (examples: Internet of Frame relay). 9
What is a logical/virtual semi-permanent circuit technology that uses fixed length data cells?
Cell Relay (example: ATM). 9
T/F. A telephone call is an example of a packet switched network.
False. A phone call is an example of a circuit-switched network. 9
T/F. Packet switched networks take the same path for each packet?
False. Packets can be sent over multiple paths depending on congestion, delays, outages, etc. 9
T/F. TCP is connectionless.
False. TCP uses a three way hand shake.Syn, Syn-Ack, Ack. 9
T/F. UDP uses acknowledgements
False. TCP uses acknowledgements. 9
T/F. Static routes are dynamically updated.
False. Static routes must be manually entered. Dynamic routes automatically update. 9
Name a couple dynamic routing protocols.
RIP (Routing Information Protocol), OSPF (Open Shortest Path First), Interior Gateway Protocol (within a common administrative domain), Exterior Gateway Protocol (used between autonomous domains). 9
What is the administrative distance of a static route?
One. Note: the AD is a confidence rating in the routing information (a lower number is better). A one will force routers to use a static route over all other dynamically calculated routes from routing algorithms. 9
What is the maximum hop count in RIP?
What port does SMTP use?
TCP port 25. SMTP is Simple Mail Transport Protocol and is used for sending email. Ch 10
What port does Post Office Protocol v3 use?
TCP port 110. POP is used for downloading e-mail from a mail server to your local computer. IMAP leaves the mail on the mail server. Ch 10
What port does FTP use?
TCP Port 20 and 21. Data = 20, Commands = 21. FTP is File Transfer Protocol and is used for uploading and downloading files to FTP file servers. Ch 10
What are the four layers of the TCP/IP stack?
ApplicationTransportInternet Layer (or network Layer)Link Layer (or network access Layer). 10
Name three e-mail protocols.
SMTP (sends email) port 25POP3 (download/read email) port 110IMAP (read email from a mail server) port 143.Ch 10
What layer are ports associated with?
Transport Layer. 10
What protocol dynamically assigns an IP address to a device when the device joins the network?
Dynamic Host Configuration Protocol. (DHCP) 10
What does TCP use for flow control?
T/F. MAC addresses are temporary
False. MACs are a burned in address on a NIC.IP addresses are temporary. 10
What are the three IPv4 private address ranges
Class A 10.0.0.0/8Class B 172.16.0.0/12Class C 192.168.0.0 /16.Private IPs are not “routable” over the Internet. Anyone can use private IPs internally with NAT.Ch 10
Class D IPv4 address are used for ___________?
Multicast. Chapter 10
What protocol is used to map a MAC address to an destination IP address?
ARP = Address Resolution Protocol. Chapter 10
Name three things cookies can be used for.
Additional Authentication.User Preferences.Shopping cart contents.Chapter 10
What is an intranet?
An Internet-like network with web servers, mail servers, etc inside a company.Ch 10
What is an extranet?
A portion of the intranet that is shared with parties/ partners/ employees outside the corporate walls. Ch 10
Private Branch Exchange. A private telephone system within an enterprise that switches calls between enterprise users on local lines and allows all users to share a certain number of external phone lines. 11
the “last mile” telephone line from home/ business to the central office. 11
hosts the telephone switching equipment and provides a local dial tones. 11
A high bandwidth transmission line that supports or combines many lower capacity lines (like a tree “trunk” carrying sap for the many connected limbs above). 11
demarcation point or demarc
The point where an external wired network connects with the customer's on-premises wiring. The external network’s responsibility for repair and troubleshooting ends at the demarc. 11
The exchange of control information to establish a telephone call (dial tone, off-hook signal, digits dialed, etc.). 11
Digital subscriber line. Sends digital data over normal phone wiring. DSL can send more data than a dial-up phone modem because DSL uses a much greater frequency bandwidth (4kHz-4MHz) than traditional telephone (0-4kHz). 11
DSL rates are asymmetric
DSL service normally has much higher downstream than upstream speeds. This satisfies most consumers’ needs because they typically download content from the Internet rather than serving content to the Internet. 11
An “always on” point-to-point connection. Once established, the connection is always live and available for transmission and reception rather than needing to be established like a dial-up connection. 11
Frame Relay (FR)
A leased service to the shared frame relay cloud for high-speed digital data between two points that is much cheaper than a leased line. The user’s cost is determined by usage and desired level of service. Frame relay service offers reliability guarantees (called the committed information rate). 11
Network security concerns
When computers are connected to a network, they may represent a concentration of data or data processing which is an inviting target for a hacker. One badly configured computer can weaken an entire network security (weakest link principle). An attacker doesn’t need to be physically present to mount an attack since they may be able to simply access the network. 12
Confidentiality, Integrity, and Availability. The 3 primary security objectives. Confidentiality protects data from unauthorized access and viewing and reading. Integrity predicts data from corruption and/or deletion. Availability enables access to data when and as needed (i.e. no denial of service). 12
Defense in depth
Even though a complex system can be harder to defend because it is composed of many pieces, the “Defense in Depth” strategy takes advantage of a layered system of systems model by defending each layer of the system to slow down an attacker and to provide warning to the next layer. 12
self-replicating code which attaches to an existing program (i.e. modifies a file) to spread. 12
self-replicating code which does NOT need to attach itself to an existing program but which uses a computer network to send copies of itself to other nodes (with or without user help). 12
software that appears to perform a desirable function but which steals information or harms the system (even if it still performs the desired function).
software that enables privileged execution while hiding its presence from administrators, applications, and the Op Sys (OS).
a collection of compromised computers connected to a network and under centralized control
deceiving people so they reveal sensitive or privileged information against their better judgment or in violation of security policy
a form of social engineering that attempts to acquire information (usernames, passwords, and credit card details) by imitating a trustworthy entity in an electronic communication
trying to guess a password by attempting all words in a list or in the dictionary
Brute force attack
trying to guess a password by attempting all combinations of letters, numbers, special characters
Denial of Service (DoS)
bombarding a server with messages to cause congestion so the server can’t respond to valid requests. 12
In communications, spoofing is pretending to be someone or something you aren’t to trick a system (like social engineering against hardware). 12
Man in the middle attack
A MiTM attack is intercepting a message, reading it, and then sending it along on its normal path. 12
a weakness in a software package or system. 12
the software or commands designed to take advantage of a vulnerability to cause unintended or unanticipated behavior leading to privilege escalation or a denial-of-service attack. 12
the code being delivered or data being exfiltrated by the exploit. 12
a malware delivery mechanism that may install malware but does no harm. 12
unencrypted data. 12
encrypted data. 12
method of encryption/decryption. 12
unique piece of information used by algorithm to encrypt/decrypt. 12
uses a similar or identical key for encryption and decryption. 12
Public Key Cryptography (aka Asymmetric Encryption)
Encryption that uses two keys: public & private. One key encrypts the message and a second key decrypts the message. 12
Public Key Encryption
To send secure data: use the recipient’s public key (available to all) to encrypt; only the recipient can decrypt the message since the recipient is only one with private key. 12
Cryptographically or electronically signed
To sign, a sender “encrypts” a message with their private key so that anyone can decrypt with the complimentary public key (available to all). If decryption succeeds, then only the holder of the secret key could have signed. 12
PKI (public key infrastructure)
encryption, software, and services for public key generation, storage, and management Includes digital certificates & certificate authorities. 12
like an electronic passport that establishes an identity The cert contains name, expiration date, public key, and digital signature of certificate-issuing authority (CA). 12
Controls access between two networks In the simplest case, they filter communications based on the allowable IP addresses and port numbers. 12
Intrusion Detection System
Monitors network and/or system activities to detect malicious activities or policy violations. 12
Intrusion Prevention System (IPS)
Monitors AND responds to a detected threat by trying to prevent it (e.g., by reconfiguring a firewall or changing the attack’s content). 12
DMZ (demilitarized zone)
an intermediate security zone between a completely untrusted external network and the secure, trusted internal network. 12
Systems Development Life Cycle. a structured methodology for defining, analyzing, designing, implementing, testing, maintaining, and retiring a system. 13
Network connectivity maps
When updating or creating a new computer system and its network, one should document the existing system and plan the proposed system. Connectivity maps depict locations and interconnections between network locations. 13
an initial measurement that can serve as a reference when comparing later measurements from the same system. Periodic measurements compared with the baseline will help show how your network and the demand is changing and could help in projecting future trends and needs. 13
Reliability is the probability that a part or computer will be working correctly up to a time t. 13
Availability is the time a system is actually operational over the total time it could have been operational. 13
Serviceability (or maintainability) is how quickly and easily a system can be repaired. 13
Mean Time Between Failures (MTBF)
Average time a device or system will operate before it fails. 13
Mean Time To Repair (MTTR)
Average time to repair a failure. 13
Capacity planning for a network
Trying to determine future capacity needs (for the network, processing, & storage). 13
prediction based on the past/current parameters multiplied by some constant (linear slope). 13
comparing your network to some industry standard and assuming you will follow the same pattern of change as the standard. 13
A computer simulation
modeling an existing system or proposed system to predict future conditions or need. 13
Packets never or network monitor such as Wireshark captures and displays contents of packets down to the frame level. 13
A port scanner determines what server ports are open/listening. 13
Time Domain Reflectometer
To determine cable lengths and bad connections, a TDR sends out a pulse and measures time to reflections. Reflections come from impedance mismatches (splices or connectors). 13
Simple Network Management Protocol (SNMP)
SNMP is an application layer protocol used to manage/monitor network-attached devices (like switches or servers). SNMP can monitor the device temperature, memory usage, component failures, power failures, and more. 13
What skills should a network manager possess?
Technical skills (networks, computers, software), People skills (works well with others: users and management), Management skills (manages tasks & resources), Financial planning skills (plans for & justifies new infrastructure, new services, new personnel), Speaking and writing skills. 13
What is delay distortion?
Delay distortion cccurs when a signal propagates faster or slower over a propagation path (e.g. signals composed of a range of frequencies can experience distortion if some frequencies travel slower through a medium like the atmosphere). A mobile source can yield compressed or delayed wavefronts (that appear to the receiver as higher or lower frequencies). 6
Noise can cause errors.How can we prevent noise/errors?
We can do the following:–Use proper shielding or filters on cables to reduce interference–Use proper terminations to reduce echo–Replace older analog equipment with newer, quieter digital components–Use digital repeaters instead of analog amplifiers–Observe the stated capacities of the media–Slow the transmission speed–Increase signal power, reduce noise power, ensure we have enough bandwidth Ch 6
What checks are useful for detecting errors?
–Parity checks–Arithmetic checksums–Cyclic Redundancy Checksums (CRC) = a non-secure hash (not tamper resistant)–a cryptographic hash is tamper resistant6
How does a parity check work?
–For even parity, add a parity bit of 1 or 0, to ensure an even number of 1s is sent–For odd parity, add a parity bit of 1 or 0, to ensure an odd number of 1s is sent–For example, if you send 1001010 and you want even parity, add a 1 as the parity bit: 100101016
What is a weakness of parity checks?
–Simple parity only detects odd numbers of bit errors. 6
Does error checking add overhead?
Yes. You end up adding extra bits to your transmission that are not part of the core information bits that you are trying to transfer.
When does it make sense to NOT check for an error?
When the transmission needs to be real time or near real time, and there is no time to request a retransmission. Examples: real time audio and video transmissions. Ch 6