1. Overview

1.1 Topics to be covered

• Framing (delimiting start/end of frames)
• Error detection and correction (handling errors)
• Retransmissions (handling loss)
• Mulitiple Access (802.11, classic Ethernet)
• Swtiching (modern Ethernet)

2. Framing Methods

2.1 Byte Count

2.2 Byte Stuffing

2.3 BitStuffing

2.4 PPP over SONET

• SONET = solid opitcal net, used by large ISP in the middle of backbones, fat pipe, giga bits

• PPP = point-to-point protocol

  
  
  
• XOR byte with 0x20 means to toggle the 5th bit
  • eg. 0x7E -> 0x5E
  • eg. 0x7D -> 0x5D
• stuffed a byte and then XOR byte with 0x20
  • eg. 0x7E -> 0x7D5E

3 Error Overview

3.1 Approach -- Add Redundancy

key issue is to structure the code to:

• detect many errors
• with few check bits
• and modest computation