[컴퓨터 통신] L2: Data Link

I'm fine...

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L2

Data link

• To organize bit to frame
• To provide hop-to-hop delivery (physical address or MAC)
  
  
  

Addressing

• L2 addresses are called physical address or MAC addresses and are used to fine the address of the next hop.
• LAN address is 6bytes (48bits).
• WAN address is usually longer.
  

ARP (Address Resolution Protocal)

• Mapping the logical address(IP address) to physical address(MAC address) dynamically.
• Anytime a host or a router needs to find the physical address of another host or router on its network...
  → Send an ARP query packet!
• The packet includes the physical and IP addresses of the sender and the IP address of the receiver.
  →Why?
  The sender doesn't know the physical address of the receiver, this query is broadcast over the network.
  
  

Data can be corrupted during transmission... For reliable communication, errors must be prevent or detected and corrected!!

Error control

• In data communication, errors are inevitable..
• Using better equipment and more reliable transmission media may reduce the frequency of occurence..
  → But it can never eliminate errors.
• Detect and correct errors.
  
  ❗ L2 Error contorl & L4 Error control
  L2: Error Detect
  L4: Error control and Error recovery

Source of errors

• White noise
• Impulse noise
• Crosstalk
• Echo
• Jitter
• Attenuation
• Distortion
  
  

Detection methods

• VRC (Vertical Redundancy Check)
• LRC (Longitudinal Redundancy Check)
• CRC (Cyclic Redundancy Check)
  
  

Error control에 관한 내용은 Transmission Layer에서 더 자세히 다룰 예정입니다.

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