Lectures notes for 2010 - KTH

Forwarding module
A simplified view of forwarding using classful address without subnetting:
Packet
Forwarding
Module
Extract
destination
address
Error (slow path)
Find
class
D or E
Extract
network
address
A, B, or C
next hop address
and
interface number
Search
table
Class A
Network
Address
Next
hop address
Interface
number
… … …
Class B
Network
Address
Next
hop address
Interface
number
… … …
Class C
Network
Address
Next
hop address
Interface
number
… … …
To ARP
The bulk of the forwarding effort is searching the tables (as most of the rest of the
processing is simple logical bit operations).
Maguire Forwarding module 2: 8 of 52
maguire@kth.se 2010.03.21 Internetworking/Internetteknik