QoS on UBR ATM PVC (DSL)? $100 paypal bounty!

I will gladly send $100 via paypal to the first person that posts (or PMs) a working config to achieve the following;

I have a Cisco 7200 with a PA-A3-T3 connected to the local ILEC's DSL network. It is running 12.2(15)T16

Each DSL subscriber connects to us, via the ILEC's DSLAM and ATM network, with an UBR PVC using RBE (Route bridged encapsulation). The ILEC provides only UBR class of service for DSL PVCs. We opted for RBE for simplicity and the ability to manage DSL modems on private IP address space while assigning a pubic static IP to the device connected to the DSL modem.

The CPE is a Cisco 678 and a Linksys VoIP ATA/Router which features outbound VoIP QoS.

We need to prioritize VoIP traffic from our SIP Proxy to the DSL user on each PVC on an outbound basis to complete the QoS loop.

The DS3 ATM interface looks like this;

interface ATM4/0 no ip address no ip mroute-cache atm scrambling cell-payload atm framing cbitplcp no atm ilmi-keepalive

each PVC for a DSL customer looks like this;

interface ATM4/0.32 point-to-point ip unnumbered Loopback0 atm route-bridged ip pvc 1/32 encapsulation aal5snap

ip route #.#.#.# 255.255.255.255 ATM4/0.32 ip route #.#.#.# 255.255.255.255 ATM4/0.32

the SIP proxy is on this interface

I have a VoIP Proxy server on the LAN connected to a FastE interface on the 7200. The VoIP Proxy uses SIP and is always in the VoIP media stream, therefore all SIP traffic passes between the Proxy and the DSL end user, making it easy to identify (all UDP from the proxy IP address is presumed to be SIP/RTP). Perhaps there is a better way to match the traffic, but it should be limited to matching traffic from a specified host or subnet, not just by application or protocol.

I would like to classify traffic as it enters the FastE interface, all traffic being of a default class of service, with UDP/RTP from the SIP Proxy IP address being a higher priority CoS.

I would then to like apply a service policy on each PVC that services the higher priority SIP/RTP from the proxy first, then the default CoS traffic.

I have spent a fair amount of time looking over docs on QoS over ATM, but do not fully understand the impact of the UBR PVCs on the options available. I imagine this as being implemented as some type of policy-map service-policy config, but I do not have enough experience to determine the best method, or if one even exists given the UBR limitation.

The 7200 is running a NPE200 and has limited memory, so features implemented after IOS 12.2 are not good options.

Since this is somewhat of a "bounty" please email me to confirm that you would be the first to reply.

I will pay the bounty after confirming that the solution provided is complete and functional (2 days max). I am good for the $100 - have faith!

I realize this approach might not be the best for this forum, but this is a time sensitive issue for me that will require a fair amount of expertise to address.

If you have the knowledge consider it lunch money for a couple of weeks!

damon at soho-systems com - email me if you need more info or would like to take he bounty! I have no issue if you would rather work offline to remain anonymous :) after all, some employers might frown on taking the money, but you deserve it if you can answer this one!

TIA

Damon

Hi Damon,

Generically speaking, what you're trying to do should work OK, provided you can isolate the other PVC's from "interfering" with each other. Here's what I'd try:

1.) Create and implement a CBWFQ/LLQ policy. You'll want LLQ for for your VoIP traffic, and the remaining traffic will be processed via WFQ. 2.) Implement per-VC queuing by applying the policy to each individual VC. You can tune the performance of your particular card via tx-ring-limit (FIFO queing) or vc-hold-queue/queue-limit (CBWFQ/LLQ). 3.) Implement appropriate traffic shaping at your 7200 to prevent issues of congestion and cell collisions. 4.) Since your using UBR, set your PCR to the appropriate line rate (e.g. 1536, 768, 512...)

Let me know if any of this is of any use, or, if you've already been there/done that. No matter how the suggestion goes, I'd like to hear the results since I'd love to work on a project like this myself! :-) If this stuff seems like something you'd like to pursue, I'd be happy to work to send you some actual configs. Didn't do it this time because I want to make sure I'm not sending you good but useless info!

Take care,

-Jason

humans will know what the deal is with the next piece of info if dashes are not present...

j-w-h-i-t-e-a-k-(at)-c-o-m-c-a-s-t-(dot)-n-e-t