05-17-2007 08:25 AM - edited 03-03-2019 05:01 PM
I'm looking for input on the following: My customer has 4 T-1s multilinked together. The multilink interface is showing about 500 drops/hour. We have LLQ enabled on the interface for voice and a "show policy-map interface" does NOT show drops. Therefore, I do not suspect QoS causing the drops. I would suspect the drops are from insufficient BW on the WAN and the packets being held (and eventually dropped) on the output queue, although I hadn't noticed (the short time there) where BW was approaching maximum.
Please see below:
Multilink1 is up, line protocol is up
Hardware is multilink group interface
Internet address is 1.1.1.1/30
--More-- MTU 1500 bytes, BW 6000 Kbit, DLY 100000 usec,
reliability 255/255, txload 48/255, rxload 17/255
Encapsulation PPP, LCP Open, multilink Open
Listen: CDPCP
Open: IPCP, loopback not set
Keepalive set (10 sec)
DTR is pulsed for 2 seconds on reset
Last input 00:00:00, output never, output hang never
Last clearing of "show interface" counters 2d04h
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 21466
Queueing strategy: Class-based queueing
Output queue: 0/1000/64/21466 (size/max total/threshold/drops)
Conversations 0/107/256 (active/max active/max total)
Reserved Conversations 1/1 (allocated/max allocated)
Available Bandwidth 0 kilobits/sec
30 second input rate 407000 bits/sec, 479 packets/sec
30 second output rate 1132000 bits/sec, 498 packets/sec
99009892 packets input, 3278541751 bytes, 0 no buffer
Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
98147723 packets output, 1237843171 bytes, 0 underruns
0 output errors, 0 collisions, 0 interface resets
0 output buffer failures, 0 output buffers swapped out
-------------------------------
sho policy-map int
Multilink1
Service-policy output: WanOut
Class-map: WanVoip (match-any)
55455406 packets, 3052106708 bytes
30 second offered rate 96000 bps, drop rate 0 bps
Match: ip dscp af31 (26)
8349051 packets, 354070734 bytes
30 second rate 14000 bps
Match: ip dscp ef (46)
6042361 packets, 957987596 bytes
--More-- 30 second rate 0 bps
Match: protocol mgcp
41063996 packets, 1740048622 bytes
30 second rate 81000 bps
Queueing
Strict Priority
Output Queue: Conversation 264
Bandwidth 25 (%)
Bandwidth 1500 (kbps) Burst 37500 (Bytes)
(pkts matched/bytes matched) 13731736/693294746
(total drops/bytes drops) 26/37391
QoS Set
dscp ef
Packets marked 55455408
Class-map: WanBusiness (match-any)
34926 packets, 9510480 bytes
30 second offered rate 0 bps, drop rate 0 bps
Match: access-group 100
34926 packets, 9510480 bytes
30 second rate 0 bps
Queueing
Output Queue: Conversation 265
--More-- Bandwidth 74 (%)
Bandwidth 4440 (kbps)Max Threshold 64 (packets)
(pkts matched/bytes matched) 5900/1873969
(depth/total drops/no-buffer drops) 0/0/0
QoS Set
dscp af41
Packets marked 34926
Class-map: class-default (match-any)
42785124 packets, 23141113724 bytes
30 second offered rate 1454000 bps, drop rate 0 bps
Match: any
05-17-2007 09:03 AM
The drops indeed seem to be due to QoS policy. As per the policy map output, for the class-map WanVoip, you can see the output
"(total drops/bytes drops) 26/37391 "
This indeed proves that there are drops for this class. No other class are showing up any drops. Probably, increasing the strict priority from 25% to somewhat higher (30%) can mitigate these drops. Thanks!
- Manoj
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