Line Rate On Physical Port - 3Com 3C13636 Configuration Manual

3Com Router 3000 Ethernet Family
Configuration Guide
The main difference between traffic shaping and traffic policing is: The packets to be
dropped in traffic policing will be stored during traffic shaping — generally they will be
put into buffer or queues (Also called Traffic Shaping – TS; see Figure 2-2). Once there
are enough tokens in Token Bucket, those stored packets will be evenly sent. The traffic
size fluctuates around the CIR rate within a range specified by CBS. Another difference
is that traffic shaping may intensify delay, yet traffic policing seldom does so.
incoming packets
Figure 2-2 TS diagram
As shown in the figure below, Router A sends packets to Router B. And Router B
implements TP on those packets, and directly drops exceeding traffic.
Figure 2-3 Traffic shaping application
To reduce packets dropping, GTS can be used for the packets on the egress interface
of Router A. The packets beyond the traffic features of GTS will be stored in Router A.
While sending the next set of packets, GTS will take out those packets from buffer or
queues and send them. So that all the packets sent to Router B accord with the traffic
regulation of Router B.

2.2.4 Line Rate on Physical Port

On a physical interface, you can enforce line rates below the physical line rate to limit
the overall transmitting rate (including the rate sending critical packets).
LR also uses Token Bucket for traffic control. If LR is configured on an interface of a
router, all packets to be sent via the interface will be firstly handled by Token Bucket of
LR. If there are enough tokens in Token Bucket, then those packets can be forwarded;
otherwise, those packets will be put into QoS queues for congestion management, so
that the packet traffics through the physical port can be managed.
Tokens enter bucket
at the given speed
classify
Token Bucket
Cache
Physical Line
3Com Corporation
Chapter 2 Traffic Classification, Policing, and Shaping
outgoing packets
queue
2-4