07-25-2007 04:13 AM
Hello everyone,
To practice QoS I build a trivial topology (attached image) to simulate a link bottleneck:
- A WAN connection 1.544 mbps between two LAN, both r1 and r2 are performing static NAT for the internal PC1 ,r1(inside local=172.16.1.1, inside global =10.10.10.11), r2(inside local=10.10.10.11, inside global=192.168.42.1), so PC1 appears to both PC2 and IPPBX as 192.168.42.1.
To simulate concurrent traffic in the network, PC1 is performing the following activities:
- Calling PC2 through IP PBX.
- read streaming audio from the media server rtsp traffic.
- http browsing.
- ftp downloading.
As you guess the goal is to guarantee an acceptable voice quality call between PC1 and PC2, so I applied QoS policy on router r2 as follow:
!!!!!!!!!
class-map match-all http-set
match protocol http
class-map match-all rtspplayer-set
match protocol rtspplayer
class-map match-all sip-voice-set
match protocol rtp
class-map match-all ftp-set
match protocol ftp
class-map match-all sip-voice-policy
match ip dscp ef
class-map match-all http-policy
match ip dscp af11
class-map match-all rtspplayer-policy
match ip dscp default
class-map match-all ftp-policy
match ip dscp af21
!
policy-map mypolicy
class sip-voice-policy
priority 500
class ftp-policy
bandwidth 150
random-detect dscp-based
class http-policy
bandwidth 100
random-detect dscp-based
class rtspplayer-policy
bandwidth 50
queue-limit 50
!
policy-map myset
class sip-voice-set
set ip dscp ef
class ftp-set
set ip dscp af21
class http-set
set ip dscp af11
class rtspplayer-set
set ip dscp default
!
interface Ethernet0/0
service-policy input myset
!
interface Serial0/0
service-policy output mypolicy
!!!!!!!!!
The result is a breaking voice quality (more comprehensible than without any QoS) and r2 e0/0 interface is continuously oscillating between up and down.
Even though I assigned a strict priority queue (LLQ) to the voice traffic (rtp) and allocated a bandwidth of 500kbps (theorically 2 calls need just 168kbps with overhead), the sniffer at PC1 is showing a variable jitter between (0-14ms) and a packet loss up to 43.74%, average audio throughput of 33.28kbps and an average packet delay of 13.72ms.
Any idea about this issue?
Thank you inadvance.
Abdel
07-25-2007 10:25 AM
You need to fix the flapping interface before anything else. Bad cable maybe?
A show policy-map interface s0/0 will tell you if the service policies are functioning correctly.
Please rate helpful posts.
Dave
07-26-2007 02:01 AM
Think you for you response,
The interface was not flapping before applying service policy to interfaces and it stops flapping after (no service-policy).
Here is the output of (sh policy-map interface s0/0) and voice traffic is being dropped, about 43.74% as mentioned by the sniffer before. I intentionally assigned more bandwidth than needed and with LLQ there should not be any drops.
I guess I?am missing something!
----
r2#sh policy-map int s0/0
Serial0/0
Service-policy output: mypolicy
Class-map: sip-voice-policy (match-all)
29727 packets, 6064308 bytes
5 minute offered rate 76000 bps, drop rate 0 bps
Match: ip dscp ef
Queueing
Strict Priority
Output Queue: Conversation 264
Bandwidth 500 (kbps) Burst 12500 (Bytes)
(pkts matched/bytes matched) 29689/6056556
(total drops/bytes drops) 1746/356184
Class-map: ftp-policy (match-all)
0 packets, 0 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Match: ip dscp af21
Queueing
Output Queue: Conversation 265
Bandwidth 150 (kbps)
(pkts matched/bytes matched) 0/0
(depth/total drops/no-buffer drops) 0/0/0
exponential weight: 9
mean queue depth: 0
dscp Transmitted Random drop Tail drop Minimum Maximum Mark
pkts/bytes pkts/bytes pkts/bytes thresh thresh prob
af11 0/0 0/0 0/0 32 40 1/10
Class-map: http-policy (match-all)
614 packets, 439620 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Match: ip dscp af11
Queueing
Output Queue: Conversation 266
Bandwidth 100 (kbps)
(pkts matched/bytes matched) 602/432122
(depth/total drops/no-buffer drops) 0/0/0
exponential weight: 9
mean queue depth: 0
dscp Transmitted Random drop Tail drop Minimum Maximum Mark
pkts/bytes pkts/bytes pkts/bytes thresh thresh prob
af11 614/439620 0/0 0/0 32 40 1/10
Class-map: rtspplayer-policy (match-all)
5810 packets, 6675919 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Match: ip dscp default
Queueing
Output Queue: Conversation 267
Bandwidth 50 (kbps) Max Threshold 50 (packets)
(pkts matched/bytes matched) 5541/6449694
(depth/total drops/no-buffer drops) 5/5/2
Class-map: class-default (match-any)
395 packets, 73997 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Match: any
07-26-2007 02:52 PM
Interesting, never heard of that happening. What does a show policy-map interface e0/0 look like? I assume it the service policy on e0/0 that causes the flapping.
What version code? I just saw a notice about serious QOS faults in 12.4(11)T.
07-30-2007 12:58 PM
From your QoS config, you're assigning a total of 800 Kbps of bw - Do you have this command "max-reserved bandwidth 100" under your serial interface?
There are alot of drops for your sip-voice-policy, thus causing VoIP quality issue.
Bandwidth 500 (kbps) Burst 12500 (Bytes)
(pkts matched/bytes matched) 29689/6056556
(total drops/bytes drops) 1746/356184
Also, take a look at your switch port where the PCs are connected...any dropped packets there? and try removing "service-policy input myset" from your E0/0, then made the test calls again.
HTH,
hieu
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