Learning Objectives

After successfully completing this section, you should be able to

  1. explain what routers are and why they are very important for the Internet to work.
  2. describe the structure of routers.
  3. explain how routers work.

Learning Tasks

Required

  1. Watch the slideshow for this section.
  2. Study Section 4.2, What’s Inside a Router?, in the textbook.

Suggested:

  1. Search the Internet for tutorials about routers. Choose two tutorials to study and post the links to the course forum with your comments.

Terms and Topics

Section 2 – Routers

Default router
First-hope router
Source router
Destination router
Graph
Input port
Output port
Routing processor
Routing table vs. forwarding table
Switch fabric
Routing processor
Area border routers
SDN router
Edge router
Destination-based forwarding
Generalized forwarding

Router forwarding plane
Router control plane
Switching techniques
Switching via memory
Switching via buses
Switching via interconnection networks
Packet loss at input ports
Packet loss at output ports
Packet scheduler
First-come-first-served (FCFS)
Weighted fair queuing (WFQ)
Quality of service guarantees
Drop-tail policy
Active queuing management (AQM)
Random early detection (RED)
Head-of-the-line (HOL) blocking in an input-queued switch
Routing control plane architectures and techniques

Leading Questions

  1. What is a router?
  2. What are routers used for?
  3. What is inside a router?
  4. What do the input ports do?
  5. How does the switching fabric work inside a router?
  6. What are the three different switching techniques? How does each of these techniques work?
  7. What do the output ports do?
  8. Where does queuing occur in a router? How do routing protocols deal with packet queuing?
  9. What is a gateway router?
  10. What are the fundamental differences between a router and link-layer switch?
  11. What is the intra-autonomous routing protocol?