[c-nsp] How can I do downstream VoIP QoS over L2TP adsl?

[Code Monkey]

(I sent the same message to adsl-qos over at sonicspike.net, but it
seems a bit more linux-centered, and my problem is near-pure Cisco)

Hi,

I've set up a network with ADSL subscribers, and some (including
myself at home ;-)) want VoIP. QoS on client side is not a big
problem, we use either linux or Cisco 837 routers on the client
premises. However, I can't find a way to do VoIP QoS on the network
side, for packets traveling downstream through the 512 Kbps L2TP
tunnel bottleneck from the QoS-enabled 100Mbps backbone to the client
premise equipment.

Can somebody here tell me what ways exist to do this?

The ADSL subscribers are on an L2TP tunnel over a fast-ethernet
full-duplex interface, configured with "vpdn-group adsl,
accept-dialin, virtual-template 1", and I've tried putting a
service-policy output on virtual-template1, but it is not taken up but
the virtual interfaces, probably because it's a strict priority (LLQ)
policy, and

http://www.cisco.com/warp/public/105/pppoe_qos_dsl.html

states:

"If the router is running the PPPoE client or server software, the
virtual-template and virtual-access interfaces do not support a
service policy that implements per-session queueing. However, a
service policy that applies QoS features other than queueing can be
applied to the interface virtual-template or interface dialer, and the
MQC features will work on per-session basis."

That's me, but how can I make a sensible VoIP policy without queueing?
Would I be able to do per-session queueing on the network side if I
changed my Ethernet-over-fiber connection to an ATM link?

Thanks for your help!