Address Resolution

1
Address Resolution

• The process of mapping protocol addresses to
  hardware addresses
• Only addresses on the same network as the host
  are resolved
• Remote addresses are never resolved

2
Address Resolution
3
Address Resolution Techniques

• Table Look up
• Closed-Form Computation
• Message Exchange

4
Address Resolution with Table Lookup

• IP ADDRESS HARDWARE ADDRESS
• 197.15.3.2 0A074B128236
• 197.15.3.3 0A0823324C44
• 197.15.3.4 0A0044245DEF
• 197.15.3.5 0A328623E3C1

5
Address Resolution with Closed-Form Computation

• Usually used where hardware addresses are
  configurable
• Usually a simple formula is used to compute the
  last part of the hardware address from the host
  part of the Protocol address
• ex. IP addr
• 192.168.2.44 -gt 01-02-03-04-05-44

6
Address Resolution with Message Exchange

• Distributed approach
• Host send out a message with the request and
  receives back a reply
• Two configurations server and individual

7
Address Resolution Protocol

• Table lookup is usually used to resolve WAN
  addresses
• Closed-form is used on configurable networks
• Message exchange is used on LANs with static
  addressing
• ARP is part of the TCP suite - standard
• Two type messages defined request reply

8
ARP Message Format
9
Sending an ARP Message
10
ARP Packet Exchange