Subject: [Capwap] Issue #2: Potential Firmware Download Performance Issue

From: Margaret Wasserman <[email-masked]>
Date: Wed, 18 Jul 2007 10:28:13 -0400

Hi All,

We have a new issue tracker up, and our old issues have not been  
migrated to it, so when I entered the new issues, they started at  
issue #2.  I don't think we have any issues open in that part of the  
numbering space, so I will continue to refer to these issues at #2- 
#5, since those are their numbers in the new tracker.

This is a thread for discussion of Issue #2:  Potential Firmware  
Download Performance Issue:

In e-mail to the CAPWAP list, Magnus Westerlund raised concerns about  
potential
performance issues with CAPWAP firmware download related to the lock- 
step nature
of the protocol on lossy or high-RTT links.  Magnus suggested the  
following
methodology to determine if there is a problem in this area:

I am lacking the information to make a good judgement of this. What size
are the firmware downloads that going to happen. And what RTTs are
expected. I think one can make a reasonable worst time estimate of the
download time considering a scenario where firmware has grown at least
10 times and the RTT is twice what is expected. Include 5% packet loss
(taking retransmission timers into account) and use an MTU of 512 bytes
and condiering all overhead and then calculate how long it would take to
complete. If one is fine with the time that is expected to take then I
think we are reasonably safe also a bit into the future.

I would really appreciate if someone took the time to do the calculation
and reported back to the list.

Margaret

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