QOS & H.323 Trunk

[mightyking]

Hello All,

I have integrated a CCM 5.1 (Main Office) with an Avaya S8400 G3 (Branch Office)using H.323 trunk connected directly from CCM to Avaya PBX over the WAN (T1). Everything seems to work fine except the audio quality. The average round trip ping reply is btw 100-120 which is quiet acceptable. We are using Cisco 2800 series routers in both ends. There's no Voice Vlan configured in the branch office. I though QOS may help to improve the situation. How am I going to prioritize the Voice traffic over data with H.323 Trunk? Any idea/config sample would be appreciated.

Thaks,

[robertdm1973]

Hi Nick-

From your thread:

"QoS will only really be used when there is contention for the port / tx-ring. "

I need to establish a tie-line between our Sydney and San Francisco offices using CME. A 256 Kbps MPLS link fits our budget. But QOS is not available for that speed.

Do you think it's ok to do it without QOS? The bandwidth is enough based from our calculations and the latency/jitter looks ok. This tie-line will only be used for Voice traffic.

Appreciate the help.

Regards,

Robert

[Nicholas Matthews]

Hi Robert,

You should absolutely run QoS on 256 kbps. Even on a full T1 you should run it.

QoS is available for all speeds, I'm not sure what you're referring to.

Even if you're 100% sure that the only traffic on the line is going to be voice, you can still get some benefits from QoS. Largely, QoS decides which traffic to drop or forward first. If all of your traffic is of the same class it may not make sense to do QoS, like in this case.

However, implementing a shaper is still beneficial because instead of flat-out dropping packets, you may hold them around for a little longer until you can get them out.

If the delay becomes too large would want to remove the shaper, however. But it would allow you to get voice through that otherwise may not make it.

hth,

nick

[robertdm1973]

Thanks Nick, unforunately QOS is a luxury that other countries still don't have. Specially for low-speed, just when you need it most :-)

We always use hard, Layer 1 circuit in the past and it's our first time to have MPLS VPN for an inter-country tieline. When the carrier say it's a guaranteed MPLS 256 kbps, do we still expect the packets to drop from end-to-end (assuming we never exceed the bw, of course)?

[Nicholas Matthews]

QoS is applied on the router and in the cloud (they're routers too). You can always apply QoS to your router as long as it's Cisco.

Technically, 'guaranteed' should mean you're not going to drop traffic. But if the country can't do QoS, who knows what may happen. Packets drop even in sophisticated networks (sometimes because they're sophisticated), so no network is really spared packet drops.

In short - to speculate, maybe.

-nick