200 Chapter 3: Classification and Marking
Example 3-6 CAR Marking Sample 2: VoIP, NetMeeting Audio/Video, HTTP URLs, and Everything Else (Continued)
rate-limit input 8000 20000 30000 conform-action set-dscp-transmit 0 exceed-action set-dscp-transmit 0
end
R3#show interface fastethernet 0/0 rate-limit
Fastethernet0/0 connected to SW2, where Server1 is connected Input
matches: access-group 111
params: 8000 bps, 20000 limit, 30000 extended limit
conformed 1346 packets, 341169 bytes; action: set-dscp-transmit 34 exceeded 2683 packets, 582251 bytes; action: set-dscp-transmit 34 last packet: 56ms ago, current burst: 29952 bytes
last cleared 00:07:11 ago, conformed 6000 bps, exceeded 10000 bps matches: access-group 110
params: 8000 bps, 20000 limit, 30000 extended limit
conformed 6118 packets, 452856 bytes; action: set-dscp-transmit 46 exceeded 34223 packets, 2552218 bytes; action: set-dscp-transmit 46 last packet: 12ms ago, current burst: 29989 bytes
last cleared 00:07:11 ago, conformed 8000 bps, exceeded 47000 bps matches: access-group 112
params: 8000 bps, 20000 limit, 30000 extended limit
conformed 677 packets, 169168 bytes; action: set-dscp-transmit 20 exceeded 3631 packets, 5084258 bytes; action: set-dscp-transmit 20 last packet: 8ms ago, current burst: 29638 bytes
last cleared 00:07:12 ago, conformed 3000 bps, exceeded 94000 bps matches: all traffic
params: 8000 bps, 20000 limit, 30000 extended limit
conformed 671 packets, 279572 bytes; action: set-dscp-transmit 0
The show interface Fastethernet 0/0 rate-limit command lists the pertinent statistical information about CAR’s performance. The output has one stanza correlating to each rate-limit command on the interface, as highlighted in the example. Under each stanza, the number of packets and bytes that conformed, and the number of packets and bytes that exceeded the traffic contract, are listed. Because this CAR configuration was intended only for marking traffic, the number of packets and bytes in each category does not matter; Chapter 5 takes a closer look at the two values. For comparison purposes, however, consider the bps rates of the combined conformed and exceeded values. For instance, the second rate-limit command referenced ACL 110, which matched the two VoIP calls between R1 and R4. These two values total 55 kbps, which is the amount of traffic expected from a pair of G.729a calls over an Ethernet network.
CAR Marking Summary
CAR is another tool that examines packet header information to classify and mark packets. CAR provides fewer options for classification and marking than does CB marking, but CAR is considered to be DiffServ compliant because it can classify DSCP using an ACL and mark the DSCP field directly. CAR, along with CB marking and PBR, makes classification decisions