Chapter 15 / 15.4 / 15.4.2

15.4.2 The Forwarding Process

Whenever a packet arrives at a router, a series of straightforward operations is performed:

1. The incoming Layer-2 frame is received.
2. The Layer-2 header and trailer are removed.
3. The destination IP address is examined.
4. The routing table is consulted to determine the next hop.
5. The packet is encapsulated within a new Layer-2 frame appropriate to the outgoing network.
6. The frame is transmitted toward the next router or destination host.

This process is repeated at every router until the packet reaches its destination network.

Although the packet may traverse many different physical media—including copper cable, fiber-optic links, microwave systems, or satellite links—the forwarding process remains essentially the same at every hop.