3 L2) Layer 2 The Data Link Layer Flashcards
What is the Data Link Layer
The Data Link Layer is the 2nd Layer above the Physical Layer. It packages Data into FRAMES. The Data Link Layer take those frames and transmit them throughout the network while performing some error detection, correction, identifying unique network devices using MAC addresses, and provides some flow control. The Data Link Layer
The Data Link Layer is divided into 2 sections:
1) The MEDIA ACCESS CONTROLE
which is responsible for assigning the MAC Address from the sender.
2) LOGICAL LINK
Now logical link control is going to provide connection services and allow your recipients to acknowledge the messages have actually gotten
where they where intended to go. The Logical link can also .
What is a Mac Address?
A MAC ADDRESS is a unique 48-bit Hexadecimal physical addressing system to every network interface card they produced. These MAC addresses are always written hexadecimally, where each of the letters or numbers is considered four bits. The first 24 bits, or the 6 letters identifies the particular vendor who made that card. The second half is going to represent the exact machine it belongs to.
What is the Logical Link ?
The LOGICAL LINK
-Provides connection services:
1) Acknowledging your recipients have gotten the frames, arrived where they were intended to go, or to retransmit in the case of corrupted or missed frames.
2) Adjust the rate faster or slower depending on the receivers needs.
3) Basic Error control function using a checksum. By adding all the bits and comparing it to either an even or odd bit final bit.
What is the Hexadecimal Numbering System?
Hexadecimal is a positional numeral system that represents numbers using a radix (Base) of sixteen.
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F
A-10
B-11
C-12
D-13
E-14
F-15
Layer 2 Synchronized communications
Communication can be synchronized across layer two, according to three different schemes:
1) Isochronous mode
2) Synchronous mode
3) Asynchronous mode
What is Isochronous mode timing?
Isochronous mode is when the networks use a common reference clock, similar to synchronous, yet they also create time slots for transmissions. Less overhead than either of the other two modes because both devices know when they can communicate and for exactly how long.
What is Synchronous mode timing?
Synchronous mode is when devices use the same clock, but the reason it’s different from isochronous is that this is going to allow us to have beginning and ending frames and special control characters to tell us when we’re going to start and when we’re going to end based on those beats.
What is Asynchronous mode timing?
Asynchronous mode is when each of our network devices reference their own clock cycles and use their own start and stop bits. In this way, there’s no real control
over when the devices are allowed to communicate though, and that becomes the major drawback here.
What are some Layer 2 DEVICES?
Layer 2 Devices:
1)MAC ADDRESSES
2) Network Interface cards (MAC ADDRESS)
3) Switches— Recognize MAC ADDRESS
4) Bridges—- -Recognize MAC ADDRESS
