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Community Member

QoS for voice with LLQ on DSL lines

Hello Everybody

I want to implement LLQ on a router with DSL lines. The scenario is: two cisco routers (827-4V) with dsl line and voice ports. The VoIP is working but the QoS (with LLQ) not already. The ATM interface on the router not support apply the policy. I applied it on the Dialer interface with LFI but the policy doesn´t match all the traffic. The traffic matched on the dialer interface is lower that traffic matched on the atm interface, a lot of traffic in not matched by the policy on the dialer interface.

Have someone worked with this kind of issue?

Thanks in advance

Edgar Valdivia

Cisco Employee
Community Member

Re: QoS for voice with LLQ on DSL lines


Don't know if you found this out yet or not but here are my findings:

VoIP over DSL needs MLP (Multilink PPP). You indicated that you have LFI (Link Fragmentation & Interleaving) so I assume you have enabled PPP multilink and customsed the fragmentation delay:

ppp multilink

ppp multilink fragment-delay 10

ppp multilink interleave

Now you should be able to configure the service policy on the dialer, not the ATM interface.

Furthermore I assume you have the stated 827 routers connected to a 'provider' router. So you'll need to configure this router with the same egress policies as you did on the 827s. If you don't then please read up on QoS as it needs to be configured over P2P links for it to work.

Sorry for the basics, here is the real core router stuff:

ATM VC - Configure this normally and make sure it knows it's bandwidth, maybe you'll been to configure the VBR on the VC to do so.

PPPoATM - Configure as normally and then add the same PPP multilink (MLP) config as stated above.

MLP bundle - apply your service policy here.

You could do this by AVpairs from your Radius server.

If you execute a SH CALLER you should now see 2 users with the same ID. One PPPoATM and one 'MLP bundle'. Both are a different virtual interface.

Optionally configure a max-reservation of 100% if you have no routing (etc) across the DSL line.

Another basic thing with QoS. The first classes are matched first like access-lists. So allways state your most important traffic first and default last.


Djerk geurts

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