Table of Contents
Advertisement
3Com Router 3000 Ethernet Family
Configuration Guide
Chapter 3 Congestion Management
3.1 Brief Introduction to Congestion Management
As to a network device, congestion will occur on the interface where the arrival rate of
packets is faster than the sending rate. If there is no enough buffer capacity to store
those packets and then a part of them will be lost, which may cause the packet
retransmission from the hosts or Router because of timeout, and lead to a vicious
circle.
The key to congestion management is how to define a dispatching policy for resources
to decide the forwarding order of packets when congestion occurs.
3.1.1 Congestion Management Policies
In general, congestion management adopts queuing technology. The system classifies
traffics using a kind of queuing algorithm, and then it will send out them with a certain
preference algorithm. Each queuing algorithm is used to handle a particular network
traffic problem and has great impacts on bandwidth resource assignment, delay, and
jitter.
We will introduce several common queue-scheduling mechanisms here.
I. FIFO (First In,First Out) queuing
incoming packets
Figure 3-1 FIFO queuing
As shown in above figure, FIFO designs the forwarding order of packets depending
upon their arrival time. On a router, the resources assigned for data traffic of users are
based on the arrival time of packets and the current load status of the network.
Best-Effort services use FIFO queuing policy.
If there is only one FIFO-based output/input queue on router's interface, malicious
applications may occupy all network resources and seriously affect mission-critical
data.
outgoing packets
queue
transmit
queue
3Com Corporation
3-1
Chapter 3 Congestion Management
interface
Advertisement
Chapters
Table of Contents
Troubleshooting
