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Author Topic: netscaler ignores advertised MSS of the back end webserver?  (Read 3308 times)

Offline danm

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netscaler ignores advertised MSS of the back end webserver?
« on: July 24, 2008, 04:36:31 PM »
Anyone else notice this?  Typically it's only going to manifest itself with a very large post. I have a capture where the netscaler is ignoring the advertised MSS of the back end webserver (1380) during the 3 way handshake and sends a packet of MSS 1460 which obviously times out then retransmits and then eventually times out.

Just to be clear this issue exists between MIP -> backend webserver and NOT client -> VIP

Is this a calculated behavior?  I'd hate to globally reduce MSS as that will affect all my customers.  PMTU unfortunately will not solve this either as I'm never seeing the ICMP come back.
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Offline TheOracle

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Re: netscaler ignores advertised MSS of the back end webserver?
« Reply #1 on: July 28, 2008, 07:19:27 AM »
PMTUD won't help on ns->server side anyway.  This would have to be considered a bug, although what service type are you using?  I would open a ticket on this though.

The Oracle
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Offline danm

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Re: netscaler ignores advertised MSS of the back end webserver?
« Reply #2 on: July 28, 2008, 07:27:55 AM »
The service is HTTP.  I've had an ongoing ticket for quite sometime now.  They seem unsure of how to classify the issue.  I sent a tcpdump from the netscaler pretty clearly illustrating it.  Just playing the waiting game now.


Quote from: TheOracle on July 28, 2008, 07:19:27 AM
PMTUD won't help on ns->server side anyway.  This would have to be considered a bug, although what service type are you using?  I would open a ticket on this though.

The Oracle
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Offline TheOracle

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Re: netscaler ignores advertised MSS of the back end webserver?
« Reply #3 on: July 28, 2008, 08:24:21 AM »
Can you send over your config to me (via messages)?  I suspect i know what is going on, but want to confirm.

The Oracle
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Offline danm

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Re: netscaler ignores advertised MSS of the back end webserver?
« Reply #4 on: July 28, 2008, 09:12:28 AM »
PM sent.  apparently my config is too large for the message board software.. LOL!
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Offline danm

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Re: netscaler ignores advertised MSS of the back end webserver?
« Reply #5 on: July 31, 2008, 02:36:53 PM »
This has been confirmed by Citrix as a misbehavior and unfortunately will not be fixed in 8.0/8.1.  Best we can hope for is a fix in 9.0 when that goes GA.


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Offline herbertsmith

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Re: netscaler ignores advertised MSS of the back end webserver?
« Reply #6 on: January 02, 2012, 11:17:46 PM »
Thanks for the great post!
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