Is real QoS possible?

Posts: 6 · New Forum Member Joined: Feb 01, 2004 Posts: 6

My situation: New Vontage user, 384/384kbps SDSL.

Problem: When doing heavy downloads the sound quality of the call is unacceptable - very choppy, basically unusable.

What I've tried:

(1) DSL modem > Cisco PIX > Cisco Router > MTA

I configured the Cisco Router to do outbound low latency queueing and set an inbound rate-limit to give the MTA a guaranteed bandwidth of 90 kbps (limiting all other traffic to 280kbps). I tried all 3 voice quality settings on the Vontage site. Didnt matter. When I queued up Agent to download from usenet the call quality was unacceptable

Ok, I figured I'd bite the bullet and try the built-in QoS feature of the MTA and did the config I wanted to avoid:

(2) DSL Modem > MTA > Home Net

Same problem - I couldnt believe it. In reading many other QoS threads here I determined that I had the same problem that someone else noticed - QoS at the MTA only helps with outbound packets. For the majority of the folks here (myself included) its inbound packets that are the problem since the majority of the traffic is from the net (downloads).

There appears to be no way to get the MTA the dedicated low-latency bandwidth it needs to make a good quality call in my setup. Once I start a usenet download I cant stop the packets from coming by turning them away at my router - at that point the damage is already done (latency has been introduced on the Voip packets from Vontage causing the call quality to suffer)

I assume that a much higher download speed would help but I thought I could get this to work with what I had - my 384/384 SDSL is rock solid, speed-tests consistently show that I am getting the full bandwidth and it has low latency in general (good ping times to first hop).

I'm very familiar with networks, routers and switches but basically I'm at a loss at what to do next. If anyone else has any ideas on what I can do (short of never have downloads going at the same time as a phone call) please post. Otherwise it looks like I'm going to send this whole thing back to Vonage as I'm still in my 14 day trial period.

Posts: 6 · New Forum Member Joined: Feb 01, 2004 Posts: 6

For those interested in setting up a Cisco Router for Voip I found this article very useful:

http://www.voip-info.org/wiki-QoS+Cisco

Here are the settings I used for my router with the MTA on the inside (at 192.168.1.43), like I said they didnt work for me but maybe this will help someone else in the f.u.t.ure looking to do something similar:

access-list 102 permit ip host 192.168.1.43 any
access-list 102 permit udp any any eq 5061
access-list 102 permit udp any any range 10000 10011
access-list 102 permit ip any host 192.168.1.43

class-map match-all voice
match access-group 102
!
!
policy-map policy1
class voice
priority 100

interface Ethernet0
description Inside
bandwidth 384
ip address 192.168.1.1 255.255.255.0
service-policy output policy1
hold-queue 100 out
!
interface Ethernet1
description Outside
bandwidth 384
ip address 192.168.2.2 255.255.255.0
service-policy output policy1
rate-limit input access-group 102 96000 65536 65536 conform-action set-prec-transmit 5 exceed-action set-prec-continue 5
rate-limit input 200000 8000 8000 conform-action transmit exceed-action drop