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MaxOutboundConnections limit on Client Access Server

Posted on 2011-10-07
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We have a client connection issue, where it seems that the maximum allowed connect sessions is reached on our Client Access Servers.

It seems that the MaxOutboundConnections value (default value of 1000) is applicable on the Client Access Server. I want to be able to alter that default value but cannot seem to find the appropriate configuration item, or Powershell command.

I would like to know if altering the HUB configured limit (1000); Set-TransportServer MaxOutboundConnections, will also alter the CAS configuration and subsequently adept its new value.
And/Or would like to know what parameter (or Powershell command) needs to be used to assure that the apparently current limit is altered to another value

Thanks a lot!
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Question by:Andor Oudt
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by:Radweld
ID: 36930656
I think you can probably made changes to the Throttling Policy to allow more concurrent connections

 http://technet.microsoft.com/en-us/library/dd297964.aspx
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by:Radweld
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by:Andor Oudt
ID: 36930768
Hi Radweld,

Thanks for the response.

From what I understand from Client Access Throttling, is that a custom configuration counts for a specific (set of) user(s), not for the Server configuration.

What we have here, is that the Client Access Server accepts 1000 (concurrent) connections and then stops accepting new ones, until the time-out value (I suspect) has been reached for a specific (set of) user(s).

I suspect it has more to do with the (maximum amount of) RPC connections to the specific server and/or MaxOutboundConnections, as defined within the HUB Transport configuration (Hub Transport/Configuration/Limits - Maximum concurrent outbound connections)
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by:sumit_arora
ID: 36930815
MaxOutboundConnections
=============================

This parameter specifies the maximum number of concurrent outbound connections that the Hub Transport server or Edge Transport server can have open at the same time. The outbound connections occur by using the Send connectors that exist on the server. The value that's specified by the MaxOutboundConnections parameter applies to all the Send connectors that exist on the transport server. The default value of the MaxOutboundConnections parameter is 1000. If you enter a value of unlimited, no limit is imposed on the number of outbound connections.

This value can also be configured using the EMC.


http://technet.microsoft.com/en-us/library/bb232205.aspx
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by:Radweld
ID: 36930837
MAxOutboundconnections has nothing to do with RPC client access,

"This parameter specifies the maximum number of concurrent outbound connections that the Hub Transport server or Edge Transport server can have open at the same time. The outbound connections occur by using the Send connectors that exist on the server. The value that's specified by the MaxOutboundConnections parameter applies to all the Send connectors that exist on the transport server. The default value of the MaxOutboundConnections parameter is 1000. If you enter a value of unlimited, no limit is imposed on the number of outbound connections.

This value can also be configured using the EMC."

This really relates to the send connector and dictates how many SMTP connections can be made, not RPC connections. I guess I should have asked you what type of connections are failing? is it RPC connections affecting Outlook users connecting to open their mailbox or is it SMTP related and your failing to send/receive mail?


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by:Radweld
ID: 36930887

Get-RpcClientAccess | fl

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by:Radweld
ID: 36930906
if you run Get-RpcClientAccess | FL then you should see the maximumconnection limit should be set to 65536
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by:Andor Oudt
ID: 36930930
Hi Radweld,

Thanks for the feedback.

I understand that the MaxOutboundConnections has nothing to do with the RPC client access, but the issue is that there seems to be a (default) limit set to 1000 and the only evidence I could find (so far) has to do with the MaxOutboundConnections, where there the default is set to 1000.

The issue is experienced by the end-user that tries to connect to his/her mailbox, via the Client Access Server, in order to get access to his/her mailbox. When that (apparent) limit is reached, the user gets an authentication prompt and is able to utilize the mailbox again. On the other end the 'idle user' gets 'kicked off' and is phased with the same 'issue'. This issue started to occur when the amount of connect requests was increased significantly (due to changes made on specific sets of mailboxes and the way they connect; cached exchange mode).
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by:sumit_arora
ID: 36934856
Outlook open a new session every time when to try to access any thing in outlook which creates a session.

same thing with outlook when sending an email. i am pretty sure when u increase the session limit it should work.
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by:Andor Oudt
ID: 36940755
Hi sumit_arora,

Thanks for participating!

From what I read you suggest to adjust/increase the session limits. From what I understand these relate to the store and not specifically to the CAS configuration. The issue seems to be related to the maximum allowed (IP) connections to a CAS server. Our configuration involves a (hardware)NLB, which is responsible for the connection of the client to the CAS configuration and remains responsible for the connection until the connection is dropped/closed.

Because our issue seems to evolve around our CAS configuration and the limits it seems to impose, I feel that altering the session limits will not address the issue and I think I will not explore this solution, just now.

Perhaps, having this additional information I shared, can assist you in better understanding my/our issue? Looking forward to reading your response
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by:sumit_arora
ID: 36940870
MaxOutboundConnections
=============================

This parameter specifies the maximum number of concurrent outbound connections that the Hub Transport server or Edge Transport server can have open at the same time. The outbound connections occur by using the Send connectors that exist on the server. The value that's specified by the MaxOutboundConnections parameter applies to all the Send connectors that exist on the transport server. The default value of the MaxOutboundConnections parameter is 1000. If you enter a value of unlimited, no limit is imposed on the number of outbound connections.

This value can also be configured using the EMC.


http://technet.microsoft.com/en-us/library/bb232205.aspx


I think you have not read this post of mine..

Now, in exchange 2010 every thing is controlled on the CAS server. User are getting connected through CAS server. No client application now is able to connect to Mailbox server directly in exchange 2010 which is a major change in e2k10.  Sending mail initiate a session on Hub server. If that value reaches 1000 it will stop initiating the send mail session and you will not be able to initiate any session post it. You can restart the throttling service on hub/cas server for the time being.  
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by:Radweld
ID: 36940877
Right this explains it, the problem is with the load balancer. Does your license support the number of connections your trying to make?
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by:Radweld
ID: 36940879
Right this explains it, the problem is with the load balancer. Does your license support the number of connections your trying to make?
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Radweld earned 800 total points
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Right this explains it, the problem is with the load balancer. Does your license support the number of connections your trying to make?
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by:Andor Oudt
ID: 36940950
Dear sumit_arora and Radweld,

Thank you both for responding so quickly and supporting the matter.

sumit_arora; you are right, I didn't see your initial response at first, thanks for pointing this out once more. So, in other words altering this value will affect the CAS configuration as well?

Radweld; thanks for being so complete ( although three is somewhat of an overkill ;)
Which licenses are you referring to? This will allow me to hopefully answer the question consistently
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by:Radweld
ID: 36940972
Your load balancer depending on make model license will only allow a certain number of concurrent connections. We checked the cas and it's configured to allow 65 thousand connections so it's not this, te load balancer is the only thing left. Check with the vendor and check the licence you have on the load balancer to make sure you can support 1000 connections.
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by:sumit_arora
sumit_arora earned 200 total points
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yes it will affect the CAS configuration too..
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by:Andor Oudt
ID: 36970000
We are currently investigating the issue and putting our focus on the network and hardware NLB. We haven't found any further evidence that Exchange is limited in its connection in any way.

I will post an update as soon as I have additional, technical information to share and/or questions to ask

Cheers and sorry for the delay!
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Author Closing Comment

by:Andor Oudt
ID: 36998988
After further analysis the issue seems to evolve around the configuration of the network layer, in combination with the hardware NLB. We are currently analyzing and troubleshooting all the output and charting the issues.

Even though the solution to the issue wasn't addressed here and/or fully accurate, I want to thank Radweld and sumit_arora for their support.
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