LAN QoS

[vctexas]

Are there any hardware/software solutions out there to provide QoS on our LAN? The VC endpoints provide great capabilities to set the QoS, but by the time the QoS markings/signals reach the edge router, much of the priority request is lost, probably in the switches. Is there some device that sits between the edge router and the WAN to handle this?

How are other enterprises setting up their LAN QoS?
How do we decide what level of QoS to give desktop videoconferencing?

Many questions!

[CamSys]

QoS is a function that needs to be enabled on yourn switch for it to acutally take priority over the other traffic on the network. As such, many of the lower-end switches do not have this capability.

What brand of switches are you running on right now?

CamSys
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[tom9933]

We don’t use QOS within the lan, but we do use packet shapers on the wan links. Check out the following link:
http://www.packeteer.com/prod-sol/products/packetshaper.cfm

[dginter001]

You can also use m0n0wall for traffic shaping:

http://www.m0n0.ch/wall/

Again - it isn't QoS but it can help out to a large degree. It's free so download it and try it out on an old box. I'm using a Pentium 90Mhz.

[Glen Sykes]

Hi vctexas,

If your VC traffic is only passing across 'dumb' layer 2 switches, then any QoS markings on your packets should be untouched as they exist in the layer 3 packet header, which are not touched by layer 2 switches.

If you are operating VLAN's, or any type of layer 3 switching / routing in the network, it is at this point that your QoS markings will be overwritten as the layer 3 packet header is removed and replaced by the router or layer 3 switch.

It is at this point in the network you need to configure QoS, as well as the edge router.

Firstly, you need to conceive a QoS policy for your network, deciding how you are going to mark your packets (i.e. Diffserv, IP Precedence) and also how you are going to categorise your different classes of traffic (voice, video, critical data, best effort). Finally you need to consider which protocol to use to enforce QoS, and this may well be determined by the switching / routing products you use. Your routers themselves ought to be able to mark packets with QoS tags and process them. It's never a good idea leave it up to the VC endpoint to mark the packet with QoS, given the freedom users have to 'promote' the QoS value, at risk of interrupting QoS stream that have a higher priority.

[trapehzoid]

You Don't need Routers/layer 3 switches to implement lan QoS. Most decent layer 2 switches will prioritize their queueing based on QoS tags as well.

Cheapo switches will not implement QoS, but good switches will implement QoS and VLAN features.

Typically QoS isn't really needed on most LANs as they are not really pushing their network to the limits.. where its more important is at the concentration points and the high-speed/low-speed boundries. Most LAN side quality issues are related to port misconfiguration or poor network designs.

The real benefit of QoS in the LAN is to have traffic marked so when it gets to the real choke points that it can be identified and handled easily. But then you get into the world of 'do you trust your edge tagging.. or do you enforce it in the network' :)

[Glen Sykes]

True a decent layer 2 switch will honour QoS tags, but I've not encountered one that will actually rewrite the tags in the packet headers, which I would say is pretty neccesary if you want to have a contiguous QoS policy in the LAN and WAN.

It's correct that QoS isn't needed in most LAN's too, and even if your endpoint sets its QoS markings at top priority, the router at the bottleneck will have the ability to rewrite the tag to the appropriate value anyway.

It's finally happened! After 12 months of posting Trapezhoid and I agree on something!! :D

[mazzarak]

***applause*** :D :D :D :D :D

[trapehzoid]

True a decent layer 2 switch will honour QoS tags, but I've not encountered one that will actually rewrite the tags in the packet headers, which I would say is pretty neccesary if you want to have a contiguous QoS policy in the LAN and WAN.

It's correct that QoS isn't needed in most LAN's too, and even if your endpoint sets its QoS markings at top priority, the router at the bottleneck will have the ability to rewrite the tag to the appropriate value anyway

ability yes.. implemented I haven't talked to many who have. with the dynamic port nature of h323, it makes it tough to tag packets.. plus.. tagging packets puts load on the router.

areas I see where real work could benefit... not stuff like HD
:silly: