Subject: Re: [Capwap] need clarification on UDP ports

From: "Abhijit Choudhury" <[email-masked]>
Date: Tue, 17 Oct 2006 14:09:26 -0700

I think for data channel security, it will have 
	to be a binary decision for an AC/WTP pair, i.e. 
	if data channel encryption is enabled, it is for all data.

	For the control channel, I think to have a clean 
	solution (with deterministic behavior) we need either 
	a separate discovery port or a type header which allows 
	one to distinguish between discovery and dtls packets.

	Scott

In a clean solution, the packet itself should have enough
information to clearly classify it as one of the four types
of packets. We should not have to depend on configuration 
lookups to check whether the packet is supposed to be DTLS
encrypted or not. 

We have used this principle already in designing the CAPWAP
header.  The T bit clearly identifies the payload as 802.3 or
native format. This could have been identified based on a 
config lookup since an AC would typically handle 802.3 payload
or native but rarely both. But we chose to include this information 
the header itself to make the design clean.

The same idea should be used for distinguishing between 
the four packet types.  Having four distinct UDP ports is one
option. I'm sure there are others.

Regards,
Abhijit
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From: NKA <[email-masked]>
Date: Thu, 19 Oct 2006 02:14:20 +0530

> lookups to check whether the packet is supposed to be DTLS

[NKA] Good point. But remember that for this flag to be affective, it
needs to appear before the DTLS header. Currently Capwap transport
header comes after DTLS. If we take your suggestion, Capwap header
will be in two part. One part will appear before DTLS header and second one
will be after DTLS header. But didn't we recently decided to not go with Mux
header approach?