From: Ivan Walker (ivan@itpro.co.nz)
Date: Sat Dec 13 2008 - 00:01:33 ARST
1. When shaping using MQC on a interface that also passes VoIP traffic
(priority queuing of voice traffic via child policy) what are the pros
and cons of using a Tc of 4ms (minimum possible as far as I understand)
compared with a Tc of 10ms (Cisco recommended value for voice in some
documents I have seen). For example the impact on CPU or possible delay.
2. If shaping is configured as follows how are packets larger than Bc
accommodated? (no interleaving configured).
CIR = 1000000bps
Bc = 4000bits (500bytes)
Be = 0
Tc = 4ms
3. Again with the above shaping configuration, if only packets of size
400bytes were sent does that mean it will never be possible to utilise
the full 1000000bps but rather only 400/500 * 1000000 = 800000bps?
4. Using IOS 12.4.13b it was possible to see the stats for delayed
packets and other values such as Tc.
router#show policy-map interface gi0/0
GigabitEthernet0/0
Service-policy output: SHAPE
Class-map: class-default (match-any)
7522946 packets, 1961480754 bytes
30 second offered rate 66000 bps, drop rate 0 bps
Match: any
Traffic Shaping
Target/Average Byte Sustain Excess Interval Increment
Rate Limit bits/int bits/int (ms) (bytes)
5000000/5000000 6250 50000 0 10 6250
Adapt Queue Packets Bytes Packets Bytes Shaping
Active Depth Delayed Delayed Active
- 0 7518711 1956530048 118002 129484844 no
I can't seem to get the same stats from 12.4.22T
router#show policy-map interface fa0/0 output
FastEthernet0/0
Service-policy output: SHAPE
Class-map: class-default (match-any)
13 packets, 2184 bytes
30 second offered rate 0 bps, drop rate 0 bps
Match: any
Queueing
queue limit 64 packets
(queue depth/total drops/no-buffer drops) 0/0/0
(pkts output/bytes output) 13/2366
shape (average) cir 3000000, bc 12000, be 12000
target shape rate 3000000
Any ideas?
Thanks
Ivan
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