Annex C11 OSI Data Link Layer

Question 0

Examples of valid Media Access Control Addresses

Answer 0

The two layer addressing uses local addresses called the MAC address. A MAC address is a 48 bit hexadecimal address that is imprinted on every network interface card.

Commonly shown as 6 groups of 2 hex digits divided by colons.

00:05:9A:3C:78:00

Question 1

Intermediary Devices used in the datalink layer

Answer 1

Switch

Question 2

Cyclic Redundancy Check (CRC)

Answer 2

The receiving station will compare the value in the FCS field to the bits that it received from the frame. This check is called a Cyclic Redundancy Check (CRC)

Question 3

Logical Link Control (LLC)

Answer 3

Software process that provides support and services to the network layer protocols. LLC uses the datalink layer protocol to frame the PDU from the network layer and identify the network layer protocol contained within the frame. This allows multiple layer 3 protocols can use the same network interface card and media

Question 4

Purpose of the Media Access Control sub layer of the Data Link Layer of the OSI Model

Answer 4

A hardware process used to address the frame PDU utilizing hardware MAC addresses. It also controls the start and ending of each frame, and determines how the data gains access to the physical media as it is sent out on the physical layer.

Question 5

Examples of the broadcast Media Access (MAC)

Answer 5

Broadcast layer 2 address is all Fs, or FF:FF:FF:FF:FF:FF

Question 6

Carrier Sense Multiple Access with Collision Detection (CSMA/CD)

Answer 6

Carrier Sense: Each node monitors the media for the presence of a data signal. If data signals are absent, indicating taht the media is free, the device transmits the data

Collision Detection: While nodes are listening, if they detect that another device was transmitting at the same time, or that two devices were transmitted at the same time, all devices stop sending and wait and randomized amount (backoff time) of time before attempting to resend their data or to transmit for the first time

Question 7

Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA)

Answer 7

Carrier Sense: Each node monitors the media for the presence of a data signal. If data signals are absent, indicating taht the media is free, the device transmits the data

Collision Avoidance: Each node sends out a warning before transmitting IOT attempt to prevent collisions before they send actual data traffic

Question 8

Physical Topology and types

Answer 8

Bus Topology: 1 media or cable connects all of the hosts and share 1 collision domain

Ring Topology: Each computer is connected to another computer via cable and shares 1 collision domain

Star Topology: Every device in the network is connected to a central device like a switch or a hub, either multiple collision domains or a sing collision domain

P2P Topology: Two nodes are directly connected. Collision domain is the same

Question 9

Frame

Answer 9

Independent of the media on which the data will follow, when the network layer packet is encapsulated in its layer two protocol

Question 10

Logical Topology

Answer 10

Focuses not on how the devices are physically connected, but on data actually moves between nodes

Bus: 1 collision domain among devices on the network

Ring: Only topology that follows the physical topology

P2P: for a computer to talk across the switch to a server, it will act like a p2p connection and allow unimpeded full duplex comm.