TCP/IP KeepAlive, Session Timeout, RPC Timeout, Exchange, Outlook and you

Update June 21th, 2016 following feedback and a (true golden) blog post by the Exchange Team – Checklist for troubleshooting Outlook connectivity in Exchange 2013 and 2016 (on-premises) I’ve updated the recommended values for the timeout settings, and shortened the article overall for better reading. Do read the post in general, and in topic – check the CAS & Load Balancer configuration paragraphs.

Hi Again,

This post will spotlight networking considerations that are mostly overlooked. I’ve gathered a few of these issues that might brought you here searching for an answer:

  • Outlook is retrieving data from the Microsoft Exchange Server
  • The connection to Microsoft Exchange is unavailable. Outlook must be online or connected to complete this action
  • Sent items are stuck in Outbox or delayed
  • Outlook freezes or stuck when sending a message
  • Event ID 3033 regarding Exchange Server ActiveSync complaining about the most recent heartbeat intervals used by clients
  • Other strange / weird issues “but PING works! / telnet to the port works great!” – my personal favorite

The mentioned issues or symptoms could take place in any network environment, thus more common in complex network setups where multiple devices are protecting / route network traffic. Some typical configurations examples could be one of the following:

  • Outlook Anywhere or RPC over HTTP is being used, servers are protected or published by ISA / TMG / UAG / F5 / Juniper or any other reverse proxy / publishing solutions
  • Exchange servers are located behind a firewall, router or other network device
  • Clients / Remote clients are located behind a firewall, router or other network device (just to be clear on that…)
  • Exchange servers are being load-balanced with an external physical / virtual appliance

If you’ve read this post up until here and got disappointed because the above does not fit your issue, I’d like to suggest reviewing other RPC troubleshooting topics that might help Troubleshooting Outlook RPC dialog boxes – revisited or Outlook RPC Dialog Box Troubleshooting

Exchange Server traditionally (2000 to 2010) used MAPI over RPC to communicate “natively”, RPC is known to be “sensitive” and that’s why Exchange Server 2013 and beyond allows only Outlook Anywhere (RPC over HTTP) connections from clients which in my opinion is a great change that will simplify future deployments.

Client<>Server connections in general remains active while data “flows” , mails are sent/received etc. but when the connection is Idle, we might have a situation that it will be terminated. Here comes the term KeepAlive – a “dummy” packet that makes sure the connection remain active while no data is flowing and idle.

Here’s my “how-to” suggestion:

  • Configure the RPC timeout on Exchange servers to make sure that components which use RPC will trigger a keep alive signal within the time frame you would expect
    reg add "HKLM\Software\Policies\Microsoft\Windows NT\RPC" -v "MinimumConnectionTimeout" -t REG_DWORD -d 120
  • Consider modifying the server TCP/IP KeepAlive to reduce the chance of “IDLE” connections being terminated – (Default is Two hours – The recommended value is 30 minutes , and no less then 15 minutes) – this controls the OS TCP behavior with idle connections, could greatly improve responsiveness and scalability –
  • Make sure that you are aware of any router, firewall or any other network device that is placed between your clients and your servers. Once you do – note their session timeout, session TTL or session ageing setting for the relevant protocol and port! (this could be tricky, so do not treat this lightly)

The trick for success here is that timeout settings should be configured without overlapping one another while following the client access “path” – for example – Client > FW > Load Balancer > Server:

  • FW timeout TCP/IP timeout – 40 minutes
  • Load Balancer – TCP/IP timeout – 35 minutes
  • Server – TCP/IP timeout – 30 minutes

If additional network devices are placed between the server and your clients, make sure that session timeout settings continue to be configured accordingly.
With today’s security measures, network security has become much more complex. A typical corporate network will implement many different network appliances or software based solutions to secure data, restrict access, prevent attacks and unwanted traffic.
Bottom line – don’t think you are done with network considerations just because “ping works” or an email comes with a statement like “your port is now open”.

I hope this post will benefit others as this issue was and will probably remain common with Exchange and other client / server services.

Don’t get timed out 🙂

Additional useful links and sources of data:

Configure Static “fake” server names for RPC over HTTPS

Hi !

This came up with a request to “fake” exchange server names, which are actually old DE-commissioned servers. users are using RPC over HTTP , and the exchange profile they use had those server names as the actual mailbox server.

This issue might show up when performing cross forest migration or removing servers, while manipulating name resolving using DNS CNAME records, etc..

With Exchange 2010 and Exchange 2007 Outlook Anywhere settings are applied automatically when you enable the outlook anywhere feature on a CAS server, proxy names in the registry ( HKEY_LOCAL_MACHINESOFTWAREMicrosoftRpcRpcProxy) are automatically entered, that is all back-end  servers that were enabled for RPC over HTTP (2003) and all mailbox servers 2007 / 2010.

So by default RpcProxy will only answer for existing  mailbox servers, we want to add our own “old” , “fake” exchange server names.

Here’s how to manipulate the RpcProxy entry in the Exchange server make it stick.

Use at your own risk!

Under each CAS you will enable for Outlook Anywhere follow these steps:

  1. Configure “PeriodicPollingMinutes” to 0 , this will stop automatic settings overwrite – removing the static entries you will add later.Locate the value  PeriodicPollingMinutes, under HKEY_LOCAL_MACHINESYSTEMCurrentControlSetservicesMSExchangeServiceHostRpcHttpConfigurator

  3. Configure the “fake” names, for example “” will be the fake mailbox server we will add.
    Append “;;” to the value of “ValidPorts_AutoConfig_Exchange”
    The String Value is under : HKEY_LOCAL_MACHINESOFTWAREMicrosoftRpcRpcProxyFor example:

    EX2010.test.lab:6004;ex2k3:6001-6002;ex2k3:6004; ex2k3.test.lab:6001-6002;ex2k3.test.lab:6004;;

  5. Restart the services: MSExchangeServiceHost and MSExchangeProtectedServiceHost

  7. IISReset

Done !

Now configure outlook to use the server and configure Outlook Anywhere to verify it works.

How to publish Exchange 2003 and Exchange 2010 with ISA 2006


First Step-By-Step !

This guide will show you how to configure ISA 2006 for coexistence of Exchange 2003 with Exchange 2010 remote connectivity services, including:

  • Outlook Web Access & Outlook WebApp
  • Microsoft ActiveSync
  • RPCoverHTTP – Outlook Anywhere
  • Publishing Exchange 2010 FARM – two client access servers

This guide assumes that:

  • ISA 2006 is configured to publish OWA 2003 and all additional services
  • SSL is configured for the Exchange 2003 server
  • Windows Integrated Authentication is enabled on the ActiveSync Vdir in the Exchange 2003 Back-End server ( )
  • RPC-over-HTTP was working for for 2003 mailboxes, and the 2003 back-end is configured as an RPC-over-HTTP
  • The current configuration works 😉
  • This guide will not cover scenarios when exchange is directly exposed to the internet. which I personally do not recommend in generally….

Okay here we go:

  1. Configure redirection for Exchange 2003 OWA:
    Exchange 2010 will redirect a user that holds a mailbox in exchange 2003, this will be possible when the following cmdlet will be run on the Exchange 2010 Client Access server:
    Get-OwaVirtualDirectory -server cas01-2010 | Set-OwaVirtualDirectory -Exchange2003Url
  2. Publish Exchange 2010 client access web farm with ISA 2006, OWA first:

New OWA 2010 Publishing Rule Outlook Web Access Publishing

– Notice ISA 2006 does not provide a wizard (or the new form) for OWA 2010 – for that you need TMG

– Now we need to create the Web Farm and select it as the target for the publishing rule

– Configure the web listener and authentication delegation option

– The web listener should be already configured for Form Authentication and a valid SSL certificate

– The publishing rule for the Web Farm is now complete.

– Two additional configurations are now required:

    1. Edit the new “exchange2010” Rule:
      Remove the legacy virtual directory’s – /Exchange, /Exchweb and /Public they will continue to be published to your original 2003 rule.
      Add /ecp/* as this is the new “options” applications for users, and a powerful administration web console with Exchange 2010.
    2. Edit the original OWA 2003 publishing rule and remove Microsoft-Server-ActiveSync path, we will next create ActiveSync publishing rule for Exchange 2010.

Now we have three last steps to finish our Exchange 2010 publishing:

  1. Create a new Exchange Web Client Access rule – and select ActiveSync – Repeat most of part 1 except we select ActiveSync, publish the webfarm, enter the same info, and select the same listener.
  2. Now as same for ActiveSync, we need to move the RPCoverHTTP (Outlook Anywhere) from the 2003 publishing rule to 2010 publishing rule. Delete the existing rule. Next you we will create a new publishing rule for Outlook Anywhere based on Exchange 2010.
  3. Create a new Exchange Web Client Access rule – and select Outlook Anywhere – Repeat most of part 1 except we select Outlook Anywhere, publish the webfarm, enter the same info, and select the same listener.

That’s it 🙂

if you kept up with all the requirements, all should be fine and you are now able to migrate your 2003 users to 2010 with ease, while both systems are allowed for external connectivity.


More relevant links on the subject:

Upgrading Outlook Web App to Exchange 2010

Transitioning Client Access to Exchange Server 2010

Edit ISA / TMG login form – Easily !

Wanted to share this nice little app I’ve found.. it will allow you to easily ” Customizing HTML Forms in ISA Server 2006 ” (or TMG) , instead of editing strings.txt and customize html stuff , go GUI 🙂
A free community utility by  Kay Sellenrode – FBA Editor v1

Just visit the page, or check out this youtube video showing off this great utility.