Subject: Re: [Capwap] capwap transport analysis: QoS vs multiport

From: "Pat Calhoun (pacalhou)" <[email-masked]>
Date: Tue, 13 Jun 2006 06:58:31 -0700

> [I don't agree that we should universally mistrust client 
> marking, but that is a different (and independent) 
> discussion, so we can take that up later.]

I have rarely ever had a discussion with a vendor, or customer, where
they trust the end device to mark its own packets appropriately. First,
they don't trust the device, and second, the burden of pushing
classification
policies to all of their end user devices is too onerous.

> So if the AC and WTP were to mark control packets so as to 
> make them distinguishable from data packets (using one of the 
> marking methods suggested above, and without relying on 
> client truthfulness), what problems remain? 

Well, I believe there are two issues are exist:
1. The protocol currently has no method of pushing down classification
rules, in the form of TSPECs. So the WTP doesn't actually know what 
rules to enforce.
2. When centralized 802.11i is in force, the WTP cannot actually
perform classification because all packets are encrypted, which forces
the WTP to trust the STA's marking.

I believe that both issues need to be addressed in order to allow the
WTP to perform this task, otherwise we venture into yet another area
where some functionality of the protocol is not permitted when an
optional feature is enabled.

Pat Calhoun
CTO, Wireless Networking Business Unit
Cisco Systems

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From: Scott G Kelly <[email-masked]>
Date: Tue, 13 Jun 2006 07:08:42 -0700

Hi Pat,

> optional feature is enabled.

I don't think you answered the question I asked, so maybe I didn't 
formulate it correctly. Let's defer the question of end-user devices 
marking their own traffic for now, as that is a different issue.

Instead, let's try to answer to this: if the AC/WTP (which are 
infrastructure network gear installed by the network administrator) mark 
control traffic so that it can be distinguished from data traffic, what 
problems remain with respect to control traffic QoS?

Thanks,

Scott