Subject: [Capwap] Issue 205: How to deal with multiple CAPWAP Control Address message elements

From: "Pat Calhoun (pacalhou)" <[email-masked]>
Date: Wed, 24 Sep 2008 18:04:18 -0700

All,

This issue was raised by the IESG during their review process:

> Section 4.6.9., paragraph 1:
> >    When multiple CAPWAP Control IPV4 Address message
> >    elements are returned, the WTP SHOULD perform load balancing
across
> >    the multiple interfaces.
> 
>   This is the first time load balancing is mentioned in this document,
>   and there are only two other mentions, neither of which explains how
>   load balancing is to be performed?

Yes, this is a good point. I am proposing including a reference to
section 6.1 
For both the CAPWAP Control IPv4 Address and CAPWAP Control IPv6 Address

Message elements, as well as new text in the first paragraph of section
6.1
To provide some guidance on load balancing. The resulting text looks
like:

<updated text>
4.6.9.  CAPWAP Control IPv4 Address

   The CAPWAP Control IPv4 Address message element is sent by the AC to
   the WTP during the discovery process and is used by the AC to provide
   the interfaces available on the AC, and the current number of WTPs
   connected.  When multiple CAPWAP Control IPV4 Address message
   elements are returned, the WTP SHOULD perform load balancing across
   the multiple interfaces (see section 6.1).

4.6.10.  CAPWAP Control IPv6 Address

   The CAPWAP Control IPv6 Address message element is sent by the AC to
   the WTP during the discovery process and is used by the AC to provide
   the interfaces available on the AC, and the current number of WTPs
   connected.  This message element is useful for the WTP to perform
   load balancing across multiple interfaces (see section 6.1).

6.1.  Join Request

   The Join Request message is used by a WTP to request service through
the
   AC.  If the WTP is performing the optional AC discovery process (see
section
   3.1), the join process occurs after the WTP has received one or more
   Discovery Response messages. During the discovery process, an AC MAY
return
   more than one CAPWAP Control IPv4 Address or CAPWAP Control IPv6
Address
   message elements. When more than one such message element is
returned, the
   WTP SHOULD perform "load balancing" by choosing the interface that is
   servicing the least number of WTPs (known through the WTP Count field
of the
   message element). Note, however, that other load balancing algorithms
are 
also
   permitted. Once the WTP has determined its preferred AC, and its
associated
   interface, to connect to, it establishes the DTLS session, and
transmits the
   Join Request over the secured control channel. When an AC receives a
Join
   Request message it responds with a Join Response message.

</updated text>
_________________________________________________________________
To unsubscribe or modify your subscription options, please visit:
http://lists.frascone.com/mailman/listinfo/capwap

Archives: http://lists.frascone.com/pipermail/capwap