User`s guide

218 XSR User’s Guide
Mechanisms to Provide QoS Chapter 10
Configuring Quality of Service
The bucket for holding tokens for normal burst is refilled first. If the
calculated Refill Token Bytes is enough to top the bucket for normal burst to the
burst value specified, the remainder of Refill Token Bytes are added to the
bucket for excess burst (refer to the formula below). Also, the number of
tokens for excess burst is also limited by the excess burst value specified in
the
police command.
The packet length is checked against the token bytes available in the two
buckets. If the number of token bytes in the bucket for normal burst is larger
than the packet length, the conform-action applies to this packet; if the token
bytes for normal burst is not enough, but the number of token bytes for excess
burst is larger than the packet length, the exceed-action applies to this packet; if
neither of the token bytes for normal burst or excess burst is enough, the
violate-action applies to this packet.
In the following example, traffic policing is configured with an average rate of
8,000 bits per second, normal burst size of 2,000 bytes, and excess burst size of
4,000 bytes. Packets entering serial interface 1/0 are analyzed as to whether
packets conform, exceed, or violate specified parameters. Packets which
conform to parameters are sent, those which exceed parameters are set to a
DSCP value of 43 and sent, and those which violate parameters are dropped.
XSR(config)#class-map the_heat
XSR(config-cmap<the_heat>)#match access-group 2
XSR(config)#policy-map turf
XSR(config-pmap<turf>)#class the_heat
XSR(config-pmap-c<the_heat>)#bandwidth percent 30
XSR(config-pmap-c<the_heat>)#police 8000 2000 4000 conform-action
transmit exceed-action set-dscp-transmit 43 violate-action drop
XSR(config)#interface serial 1/0
XSR(config-if<S1/0>)#service-policy output turf