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Dallas, TX
·AT&T U-Verse
reply to nosx

Re: Low Latency Queueing Problem With PPPOE(OA?)

I'll be interested to see if you can dig any more info up on this. I thought I remember someone mentioning once that the WIC-1ADSL module was not really capable of handling queuing in hardware, although it is configurable. I never could find any hard documentation reflecting this statement though.

If you apply the service-policy to the Dialer interface instead of the ATM PVC does that resolve the issue? Is it possible that the ATM interface is slicing up the cells prior to that queuing policy which is causing it to behave inappropriately or in an unexpected manner? The config suggestions I have always seen for this module for queuing show the service-policy on the Dialer interface and not the physical interface configuration.
Ignorance is temporary...stupidity lasts forever!



Da Geek Kid,
Yes I misspoke, I was using the word discard to reference the traffic killed by the strict priority queue policer.

My understanding was that the dialer was just like a virtual template, applying something to it has no effect until a virtual-access interface is cloned from it. You can apply anything you want to it, but if the virtual access doesnt accept the configuration when it clones, it will have no useful effect. The Virtual-access interface will not accept CBWFQ/LLQ policy-maps. Furthermore virtual interfaces such as dialers, VTs, VAs, etc dont have queues, they are just FIFO with near unlimited bandwidth, and dont get congested (thus appear not to properly shape, queue, or police effectively). If i check the ATM interface after applying just a policer policy, the policer claims to be dropping traffic but the traffic is still transmitted, and the ATM interface shows that its tail dropping cells indicating the traffic sent through is far above the policer value and congesting it. Im very displeased with the WIC-1ADSL and am wondering if the WIC2-1ADSL? provides better hardware support for this sort of thing? The fact that the interface is ATM could in itself prevent the use of CBWFQ/LLQ. At work I havent seen an ATM interface with a shaping service-policy applied, just a VBR-NRT? statement. Next best solution is to stick a wic-1enet in and just shape the ethernet down to 512k. I know shapers do function on ethernet interfaces, but it would mean setting up an external DSL modem and not having reliable link failure detection, instead requiring reliance on the SLA? features (didnt Cisco renamed that?) to detect link failure.