mirror of
https://github.com/jackyzha0/quartz.git
synced 2025-12-27 14:54:05 -06:00
44 lines
1.3 KiB
Markdown
44 lines
1.3 KiB
Markdown
---
|
|
title: "21-data-link-layer-LAN"
|
|
aliases:
|
|
tags:
|
|
- cosc203
|
|
- lecture
|
|
---
|
|
|
|
# data link layer services
|
|
- transfer datgram from one node to **physically adjacent** node over a link
|
|
- terminology
|
|
- hosts and routers: node
|
|
- communication channels between adjacent nodes: links
|
|
- wired
|
|
- wireless
|
|
- LANs
|
|
- layer-2 packet: frame, encapsulates datagram
|
|
- 
|
|
|
|
|
|
services
|
|
- framing, link access:
|
|
- encapsulate datgram into frame, add head, trailer
|
|
- do not use IP address
|
|
- use MAC address in frame headers
|
|
- reliable delivery of data between adjacent nodes
|
|
- flow control: pacing between adjacent sending and recieving nodes
|
|
- error detection and correction
|
|
- errors from: signal attenuation, noise
|
|
- receiver detects errors and signals retransmission, or drops frame
|
|
- reciever identifies and correct bit error(s) without retransmission
|
|
|
|
implemented in network interface card: (NIC) or on a chip
|
|
- ethernet, WiFi card or chip
|
|
- implements link and physical layer
|
|
|
|
each NIC has a unique ID - MAC (medium access control)
|
|
- 48 bits: six groups of two hex digits
|
|
- also called physical address, ethernet hardware address
|
|
- manufacturer buys portion of MAC adress space (to assure uniqueness)
|
|
|
|
# parity checking and CRC
|
|
|
|
# MAC protocols |