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Section 3: OSI Model Flashcards

(63 cards)

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1
Q

OSI Model

A

Application (7)
Presentation (6)
Session (5)
Transport (4)
Network (3)
Data Link (2)
Physical (1)

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2
Q

data on each OSI layer:

A

layers 5, 6, 7: data
layer 4: segements
layer 3: packets
layer 2: frames
layer 1: bits

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3
Q

Physical Layer

A

transmission of data (bits) and electrical signals across the network

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4
Q

Connector Standards

A

RJ-45 - Used in Cat5/Cat6 cables

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5
Q

Wiring Standards

A

TIA/EIA-568A
TIA/EIA-568B

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6
Q

Crossover cables

A

TIA/EIA-568A on one end, TIA/EIA-568B on the other

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7
Q

Straight-through cables

A

TIA/EIA-568B on both ends

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8
Q

Asynchronous Communication

A

out of sync data transmission

includes a start and stop bit, like leaving a voicemail

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9
Q

synchronous Communication

A

real-time communication, uses a common time source or clock

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10
Q

Broadband

A

divides bandwidth into separate channels

e.g. cable TV carrying 200 channels

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11
Q

Baseband

A

Uses all available frequencies on a cable to transmit data.

e.g. a telephone, one call at a time, ethernet

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12
Q

Multiplexing

A

allows multiple usage of a baseband connection by multiple users

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13
Q

layer 1 devices

A

fiber optic cable, ethernet, coaxial, bluetooth, wi-fi, NFC

hubs, access points, media converters

devices are essentially repeaters

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14
Q

Data Link Layer

A

package data/bits into frames to transmit
controls information flow

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15
Q

Media Access Control (MAC)

A

physical addressing system using a unique 48-bit physical address in hexidec assigned to every network interface card (NIC)

D2:51:F1:3A:34:64
D2:51:F1 = vendor
3A:34:64 = unique

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16
Q

Logical Link Control (LLC)

A

provides connection services and acknowledgement of messages sent correctly

e.g. a device can request for less information or a resend

provides error control functions using checksums

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17
Q

Isochronous method

A

devices use a common reference clock and create time slots for transmission

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18
Q

Synchronous method

A

devices agree on a clocking method, has beginning and ending frames

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19
Q

asynchronous

A

network devices reference internal clocks to start and stop bits

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20
Q

layer 2 devices

A

network interface cards, bridges/switches

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21
Q

switches

A

smarter devices that send data to specific devices based on the MAC address

uses CAM tables with MAC addresses

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22
Q

Network Layer

A

concerned with routing/switching, logical addressing, route discovery

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23
Q

Internet Protocol (IP)

A

IPv4 or IPv6

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24
Q

Packet switching

A

data is divided into packets, then forwarded
most networks use this

e.g. putting a letter in an envelope and sending it off

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25
Circuit switching
dedicated communication link established between two devices e.g. a phone call makes a temporary connection
26
message switching
data is divided into messages which may be stored and then forwarded e.g. mail arriving at the destination and waiting until its forwarded
27
route discovery and selection
manually configured as a static route or dynamically (RIP, OSPF, EIGRP) both using a routing table decide how data is going to get there
28
Connection services
provides additional reliability for layer 2 connection such as flow control and packet reordering
29
packet reordering
ensures all the data that is split up reaches the destination
30
Internet Control Message Protocol (ICMP)
Sends error messages and information to an IP destination e.g. ping, tracert
31
layer 3 devices
routers/multi layer switches
32
Transport Layer
division between the upper and lower layers of the OSI model datatype: segments
33
Transmission Control Protocol (TCP)
data is referenced as segments connection-full protocol; reliable
34
Three-way handshake
Client sends SYN packet Server sends SYN-ACK Client sends ACK, then their data e.g. certified priority mail
35
User Datagram Protocol (UDP)
data is referenced as datagram connectionless; "unreliable" things may get lost
36
Windowing
allow clients to minmax adjust the amount of data in each segment to maximize throughput e.g. if you are getting too many retransmissions, so you need to slow down
37
Buffering
devices allocate memory to store segments if it's receiving too much data to go through too little bandwidth
38
layer 4 devices
TCP and UDP protocols WAN accelerators (compresses IP packets to go faster) load balancers and firewalls (filtering ports/protocols)
39
Session Layer
keeping conversations seperated to prevent intermingling of data
40
set up session
checks credentials then assigns random numbers to the session to identify them
41
maintain session
where data transfers back and forth across the network any breaks will be reestablished and acknowledgement of data as well
42
tear down session
ending of a session after the transfer is done or a disconnection
43
H.323
used to setup, maintain, teardown voice and video communications operated over Real-Time Transport Protocol (RTP)
44
NetBIOS
used to share files over a network
45
Presentation Layer
Data Formatting and Encryption
46
data formatting
data is formatted to have compatibility between different devices e.g. ASCII = text, GIF, JPG, PNG ensures data is readable, provides redundant data structures, negotiates data transfer syntax for layer 7
47
encrpytion
scrambles data in transit for security e.g. (Transport Layer Security) TLS encryption
48
layer 6 "devices"
scripting languages, html, php standard text Pictures Video files Encryption algorithms (TLS, SSL, etc.)
49
Application Layer
Where users communicate with the computer, for the computer to be transported e.g. file transfer, network transfer
50
application services
e.g. file transfer, file sharing, email protocol , remote access
51
service advertisement
sending out announcements to other devices to state a service they offer e.g. printers
52
layer 7 "things"
Email applications (POP3, IMAP, SMTP) Web browsing (HTTP, HTTPS) DNS, FTP, RDP, SSH, SNMP, etc.
53
Encapsulation
putting headers and trailers around data moving down the OSI model, encapsulation happens e.g. encapsulating a letter in an envelope
54
Decapsulation
moving up the OSI model, decapsulation happens e.g. removing an envelope to see the letter
55
Protocol Data Unit (PDU)
A single unit of information transmitted in a network called L(layer number) PDU (L7 PDU) data names: bits, frames, packets, etc.
56
how encapsulation works
each layer adds their header/trailer with metadata to the "data", and passes it down at layer 4, adds source and dest ports at layer 3, adds source and dest IP address at layer 2, adds source and dest mac address at layer 1, transmit layer 2 frames as 0s and 1s
57
TCP header
20 bytes of information in the Header: source/dest port sequence/acknowledgement number control flags
58
TCP control flags
SYN: Synchronization of connection ACK: used to acknowledge successful transport of packets FIN (Finished): tears down the virtual connection RST (Reset): an unknown packet is received to reject PSH (Push): data is given priority to be processed URG (Urgent): identifies data as urgent, processed first and immediately
59
UDP Header
8 bytes, Source/Dest Port, Length, Checksum (optional)
60
IP header
version, length, service, total length, identifier, flags, checksum, source/dest IP, etc.
61
Ethernet Header
Source/Dest MAC address EtherType (which IP protocol is encapsulated) VLAN tag (optional)
62
Frame payloads
ethernet: 42 byte min, 46 byte no VLANs
63
MTU
Default frames: 1500 bytes Default Jumbo Frames: 9000

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