[THIN] Re: Session Reliability

I agree with Rick- Session Reliability is recommended when you have a known situation of recurring short term disconnects. However it may not be a benefit to turn on “just because”. As Rick explains it does not really make sessions more reliable, it just presents a less frustrating appearance during the period of time the session is off line and is trying to re-connect.

 

 

 

Steve Greenberg

Thin Client Computing

34522 N. Scottsdale Rd D8453

Scottsdale, AZ 85266

(602) 432-8649

www.thinclient.net

steveg@thinclient.net

 

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From: thin-bounce@freelists.org [mailto:thin-bounce@freelists.org] On Behalf Of Rick Mack
Sent: Friday, January 16, 2009 11:53 PM
To: thin@freelists.org
Subject: [THIN] Re: Session Reliability

 

Hi Angela,

 

The concept behind session reliability is to hide the disconnect/reconnect event from users. It doesn't actually improve things for your users, but instead of their sessions disconnecting and reconnecting, the session just appears to hang for a bit and then starts again. Session reliability is actually a really bad name for this enhancement because it doesn't do what it implies.

 

Session reliability is functionally a wrapper for standard ICA that encapsulates the ICA protocol and allows you to handle stuff like transparent session reconnection. However it uses a different port to ICA, TCP port 2598. The session reliability listener is the Citrix XTE service which then passes the ICA traffic on to the ICA listener.

 

So far so good, but there are 2 potential problems.

 

The first is that the XTE service hasn't been totally stable in the past with recurring instances of memory leaks and instability depending on hotfix levels. If the XTE service starts playing up, session reliability just became your worst enemy.

The second problem relates to the use of a different TCP port. It's fairly common these days to set network QOS to favour ICA traffic when you use Citrix. Everyone, especially your average comms person, knows that ICA is on TCP port 1494 and that is what is used to identify ICA packets for QOS prioritization.

 

When you switch on session reliability you are no longer using port 1494. So any QOS optimization you've got for ICA suddenly disappears, and in a worst case scenario, session performance can go out the door, you start seeing a lot more disconnections and session reliability becomes "session liability".

 

However if your users are suffering a reasonable number of disconnections and that is creating annoyance and political problems for you, then by all means investigate using session reliability. But make sure that if you are using QOS, that you co-ordinate with your comms people and ISP so that when you enable session reliability nothing will break. Make absolutely certain that they know ICA can use port 1494 AND port 2598.

 

And good luck :-)

 

regards,

 

Rick

 

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Ulrich Mack
Quest Software
Provision Networks Division

On Sat, Jan 17, 2009 at 1:28 PM, Angela Smith <angela_smith9@hotmail.com> wrote:

Hi

Im looking at enabling session reliability on my CPS 4 farm.  Are there any gotchas I need to be aware of or could this cause more issues?  Im aware of the port changes but I wanted to know if most people are using this or whether session performance is slower due to the additional connection checks..

Thanks
Angela

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