Queue Scheduling - 3Com 4200G 12-Port Configuration Manual

Traffic policing is widely used for policing traffic entering the network of internet service providers (ISPs).
It can classify the policed traffic and perform pre-defined policing actions based on different evaluation
results. These actions include:
Dropping the nonconforming packets.
Forwarding the conforming packets.
Traffic shaping
Traffic shaping provides measures to adjust the rate of outbound traffic actively. A typical traffic shaping
application is to limit the local traffic output rate according to the downstream traffic policing parameters.
The major difference between traffic shaping and traffic policing is that the packets to be dropped in
traffic policing are cached in a buffer or queue in traffic shaping, as shown in
enough tokens in the token bucket, the cached packets are sent out at an even rate. Traffic shaping
may introduce an additional delay while traffic policing does not.
Figure 1-7 Diagram for traffic shaping
For example, Device A sends packets to Device B. Device B performs traffic policing on packets from
Device A and drops the packets exceeding the limit.
To avoid unnecessary packet loss, you can perform traffic shaping for the packets destined for Device B
on the outgoing interface of Device A. Thus, packets exceeding the limit are cached in Device A and
sent when enough resources are available. This ensures that all traffic sent to Device B conforms to the
traffic specification defined on Device B.

Queue Scheduling

When the network is congested, the problem that many packets compete for resources must be solved,
usually through queue scheduling.
A Switch 4200G supports strict priority (SP) queuing, weighted round robin (WRR) queuing, and shaped
deficit WRR (SDWRR) queuing.
1) SP queuing
1-10
Figure 1-7. When there are