3Com Switch 8800 Configuration Guide Chapter 33 QoS Configuration
33-13
Note:
z The parameters of traffic policy must be the same if you configure the same tc-index
for different traffic; otherwise the system prompts you for the wrong configuration.
z For traffic policing configuration over the port group, all ports in the group shares the
same bandwidth, that is, the traffic parameters you define take effect on all ports in
the group.
Caution:
z Before configuring traffic policing, you must first define corresponding ACLs and
configure the DSCP+ Conform-Level —> Service parameters mapping table and
the Local-precedence + Conform-Level —> 802.1p priority mapping table.
You must first define the corresponding ACL and configure the DSCP + Conform-Level
—> Service parameters mapping table and Local-precedence + Conform-Level —>
mapping table before starting this configuration.
This configuration achieves traffic policing for the packets that match the ACL. If the
traffic rate threshold is exceeded, corresponding measures will be taken, for example,
dropping excessive packets.
system-index index here is the system index for an ACL rule. When delivering a rule,
the system assigns an index to it, for convenience of later retrieval. You can also assign
a system index for it when delivering an ACL rule with this command. However, you are
not recommended to assign a system index if not urgently necessary.
tc-index index here is traffic policing index, in the range of 0 to 12288. If you configure
the same index for different ACL rules during setting traffic policing, then the sum of
traffic shall be limited by the traffic policing-related parameters predefined. For example,
if CIR (committed information rate) of the traffic that matches ACL1 is set to 10 kbps
and that for ACL2 to 10 kbps, and their traffic policing indexes are the same, then the
average rate of the traffic that matches ACL1 and ACL2 shall be limited to 10kbps.
See the corresponding Command Manual for details of the commands.
33.3.3 Configuring Traffic Shaping
Traffic shaping controls the rate of outbound packets, to ensure they are sent at
relatively average rates. Traffic shaping measure tries to match packet transmission
rate with the capacity of downstream devices. Its major difference from traffic policing is:
Traffic shaping buffers packets at over-threshold rates to make them sent at average