6.2 Quality of service

r3#sh run policy-map
Building configuration…

Current configuration : 190 bytes
policy-map TELNET-policy
class TELNET-class
police cir 64000 pir 128000
conform-action set-dscp-transmit af21
exceed-action set-dscp-transmit 0
violate-action drop

this is straightforward… the above is an example configuration of a 2 rate 3 color marking policy-map (trTCM http://www.ietf.org/rfc/rfc2698.txt )

the bc (sustained burst) is an indication of how much the CIR can be exceeded, and be (excess burst) is an indication of how much the PIR (peak information rate) can be exceeded…

here is an excellent discussion by paul stewart:


the CIR and the PIR make up the tr of trTCM per rfc 2698

conform, exceed and violate

green, yellow, red

of course, green means go, etc. it’s like mister rogers neighborhood

in the above example, packets conforming will be shipped with a dscp marking of af21, packets exceeding will be shipped with the default or 0, and violators get shipped downtown…

here is some actual output:

r3#sh policy-map int

Service-policy output: TELNET-policy

Class-map: TELNET-class (match-all)
16291 packets, 23238350 bytes
5 minute offered rate 29000 bps, drop rate 6000 bps
Match: protocol icmp
cir 64000 bps, bc 2000 bytes
          pir 128000 bps, be 4000 bytes
conformed 6341 packets, 8174050 bytes; actions:
set-dscp-transmit af21
exceeded 7303 packets, 11056742 bytes; actions:
set-dscp-transmit default
violated 2647 packets, 4007558 bytes; actions:
conformed 11000 bps, exceed 15000 bps, violate 6000 bps

Class-map: class-default (match-any)
2544 packets, 263921 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Match: any

if af21 is a mystery, go here: