Subject: RE: [Capwap] One issue "In order to support NAT, I recommend thatLWAPP only support one UDP port for Control tunnel and Data Tunnel"

From: "Sadot, Emek (Emek)" <[email-masked]>
Date: Tue, 28 Feb 2006 10:14:16 -0500

David,

I was under the impression that the working group already went through
the "justification" process. To refresh our memory, I believe that the
key points that were brought up discussed the possibility that a service
provider will connect their AC to their customer's WTPs across a NAT
device, or a cooperation which segments its facilities by NAT devices
and deploy the AC at the main site and the WTPs at remote sites (private
side of NAT), or perhaps a deployment scenario would be some sort of a
hosted solutions environment, where the WTPs in the different NAT'ed
customer enterprise sites are controlled by a central AC which is part
of the provider's hosted solutions equipment.

My belief is that the CAPWAP protocol should not disallow the NAT
traversal.

Regards,
Emek 

-----Original Message-----
From: David T. Perkins [mailto:[email-masked]] 
Sent: Monday, February 27, 2006 10:21 PM
To: zhaoyujin 31390
Cc: [email-masked]
Subject: Re: [Capwap] One issue "In order to support NAT, I recommend
thatLWAPP only support one UDP port for Control tunnel and Data Tunnel"

HI,

CAPWAP with NATs has come up from time to time on this list, and people
have claimed that it is a "typical" or "basic"
scenario. I'm sorry, but I don't see it. Before the WG spends time
resolving this issue, I'd really like to see STRONG justifications. That
is, why would you deploy a CAPWAP system split this way? And if CAPWAP
didn't support this NAT split, what would it cost you, or what would you
not be able to do?

On Mon, 27 Feb 2006, zhaoyujin 31390 wrote:
> Dear all:
> 
>   I recommend that LWAPP only support one UDP port for Control tunnel
and Data Tunnel. 
> 
>   LWAPP protocol uses UDP packets, so that it can directly support NAT
passthrough.
> 
>   One basic scenario is that WTP is behind NAT device and AC is in
public network. For control tunnel, there are no problem. Because it is
initiated by WTP, NAT device can create corresponding table for LWAPP
control tunnel packets. 
> 
>   The problems is:
> 
>    1. The data packets can not be firstly sent from AC to WTP.
> 
>    2. Even if WTP firstly sends pacekts, AC can get the corresponding
control tunnel with this LWAPP data tunnel based on the packets.
Because in one NAT device, there may be multiple WTP. All WTP's IP
addresses are same which is NAT device global IP address, and AC can not
know the data packets belonging to which AP.
> Best regards
> Yujin Zhao
> H3Com

Regards,
/david t. perkins

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