Subject: [Capwap] Issue 208: Need clarity on AC behind NAT (part deux)

From: "Pat Calhoun (pacalhou)" <[email-masked]>
Date: Wed, 24 Sep 2008 18:10:24 -0700

All,

The following was raised during the IESG review:

> Section 11., paragraph 4:
> >    In the third configuration, the AC is deployed behind a NAT.
> 
>   Because all communication originates at the WTP and is addressed to
>   the  AC, communication when the AC is behind a NAT will simply fail.
>   (Unless the NAT has been specifically configured, in which case all
>   issues can be assumed to disappear.)

Yes, this is a valid point, and the text "assumed" this, but it is much
better 
To be crystal clear. Therefore, I propose changing the paragraph to:

<modified paragraph>
   In the third configuration, the AC is deployed behind a NAT. In this
case,
   the AC is not reachable by the WTP unless a specific rule has been 
configured
   on the NAT to translate the address and redirect CAPWAP messages to
the AC.
   This deployment presents two issues. First, an AC communicates its 
interfaces
   and corresponding WTP load using the CAPWAP Control IPv4 Address and
CAPWAP
   Control IPv6 Address message elements. This message element is
mandatory, 
but
   contains IP addresses that are only valid in the private address
space used
   by the AC, which is not reachable by the WTP. The WTP MUST NOT
utilize the
   information in these message elements if it detects a NAT (as
described in 
the
   CAPWAP Transport Protocol message element in section 4.6.14). Second,
since
   the addresses cannot be used by the WTP, this effectively disables
the load
   balancing capabilities (see section 6.1) of the CAPWAP protocol.
   Alternatively, the AC could have a configured NAT'ed address, which
it would
   include in either of the two control address message elements, and
the NAT
   would need to be configured accordingly.
</modified paragraph>
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