3Com CoreBuilder 2500 - IP Routing and the OSI Reference Model

4
ROUTING WITH IP TECHNOLOGY
This chapter reviews IP routing technology in these sections:
■ IP Routing and the OSI Reference Model
■ Elements of IP Routing
■ IP Routing Transmission Errors
■ Routing with Classical IP over ATM
■ IP Routing References
IP Routing and the
OSI Reference
Model
An IP router, unlike a bridge, operates at the network layer of the Open
Systems Interconnection (OSI) Reference Model. An IP router routes
packets by examining the network layer address (IP address). Bridges use
data link layer MAC addresses to perform forwarding. See Figure 4-1.
Figure 4-1 OSI Reference Model and IP Routing
Application layer
Presentation layer
Session layer
Transport layer
Network layer
Data link layer
Physical layer
MAC
IP
OSI Reference Model
ARP
RIP
ICMP
OSPF