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QoS and L2 link

Hi all. I have recently implemented a QoS policy on a L2 link which terminates on 2 1812 routers under my control. The link itself is 10 Mbit and I'm shaping the traffic on my routers to the size of the link.

The problem is that the users in the remote office have reported problems with slowness of the link. I have followed the situation and I have noticed that when the traffic gets around 8 Mbit that response times across the link start going into the 20 ms range and sometimes are even larger. I'm posting my QoS policy so if someone could tell me if perhaps the QoS policy is the problem.

Thanks in advance for any help.

class-map match-all voice-signaling

match access-group name voice-signaling

class-map match-all voice-traffic

match access-group name voice-traffic

policy-map VOICE

class voice-traffic

priority 1000

class voice-signaling

bandwidth 150

class class-default

fair-queue

policy-map MAIN

class class-default

shape average 10000000

service-policy VOICE

ip access-list extended voice-signaling

permit tcp any any eq 2000

permit tcp any any eq 2001

permit tcp any any eq 2002

permit tcp any eq 2000 any

permit tcp any eq 2001 any

permit tcp any eq 2002 any

ip access-list extended voice-traffic

permit udp any any range 16384 32767

1 ACCEPTED SOLUTION

Accepted Solutions
Super Bronze

Re: QoS and L2 link

If the physical setup is your router to provider's switch at 100 Mbpbs but 10 Mbps between provider switches, see if you can run 10 Mbps between your router and provider's switch. This would allow you to stop using shaper.

3 REPLIES
Super Bronze

Re: QoS and L2 link

The L2 link is between the two 1812 routers? What type of physical link is it and what's its physical bandwidth?

If the link is physically 10 Mbps, you shouldn't need to use a shaper. If it's physically faster and policed by a provider, you might need to account for what time intervals the provider uses and/or shape slower than the nomimal rate to account for L2 overhead.

What traffic starts to see 20 ms response times? If normal data traffic, as the link approaches 100%, traffic flows should start to queue. What your current policy should provide, is all flows, except the LLQ voice, should slow, more or less, equally.

QoS doesn't elminate the need for bandwidth, it just allows you to manage it. So, when the link is congested, you can insure some traffic gets the bandwidth, e.g. voice, but at the expense of less bandwidth provided to other traffic. If you had some large bulk flows running with your other "normal" data traffic, if you can identify that traffic, you could pull it out of the default class and place it into it's own class with a minimum bandwidth setting. This should improve the performance for the traffic left within the class-default FQ but at the expense of the extracted bulk traffic (usually an acceptable trade-off).

[edit]

PS:

As a rule of thumb, to avoid queuing for interactive type traffic, average bandwidth utilization below 33.3% is excellent. Up to 66.7% is good to acceptable. Above 66.7%, queuing can be become significant. So, you're issue above 80% is likely normal. As noted above, you might be able to further manage your traffic, or you'll need more bandwidth.

New Member

Re: QoS and L2 link

The providers end terminates on 2 Cisco switches on which I have connected 2 1812 routers. The bandwidth is physically 100 Mbps and I need to shape traffic to the actual link of 10 Mbps.

I'll try to further investigate which traffic is most affected.

And try to shape QoS accordingly. Perhaps they have started hitting the 10 Mbps mark more but I haven't been able to catch it at the right moment.

Super Bronze

Re: QoS and L2 link

If the physical setup is your router to provider's switch at 100 Mbpbs but 10 Mbps between provider switches, see if you can run 10 Mbps between your router and provider's switch. This would allow you to stop using shaper.

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