Desktop Sharing with OCS R2

I was asked by a school to provide more detail around the new desktop sharing feature in OCS 2007 R2.


What is desktop sharing?

Desktop sharing is the ability to share your desktop from a PC directly from the Communicator client with other communicator users either with a PC communicator client or to users using Communicator Web Access.


This feature is an excellent addition for OCS R2 as you can now do even easier ad-hoc collaborations with up to 100 of your peers. I use this feature all the time now during my ad-hoc meetings. You can also give control to other participants (e.g. helpdesk), take back control, etc.


                         View from desktop sharing host (above)


                  View from someone joining a desktop session (above)


                      Communicator Web Access desktop sharing (above)


What is the desktop sharing architecture?

The Application Sharing Server role is installed as part of the Front End server architecture automatically.




What do I need to do to enable this?

•Available in Standard and Enterprise Edition by the Application Sharing Server role

•No client configuration is required for users to participate in a desktop sharing session with OC2007 R2

•Microsoft Office Communicator Web Access role for web access and anonymous access

•CWA Plug-in required to share the desktop


Inside of the OCS R2 administration console, select Global Properties, Meetings tab, locate Default Policy (under Policy Definition) and click Edit.  Check “Enable Program and Desktop Sharing” and “Allow control of shared programs and desktop”


For anonymous desktop sharing use, select “Allow users to invite anonymous participants” within the OCS global properties



What protocols are used for desktop sharing?

•C3P (Centralized Conference Control Protocol).

•Session Description Protocol (SDP)

•RDP (Remote Desktop Protocol)

•RTP (Real Time Protocol)

•AV Edge Service

–ICE (Internet Connectivity Establishment)

–TURN (Traversal Using Relay NAT)


–HTTPS: Desktop sharing requires a secure connection (HTTPS)

What type of sharing can I do with the browsers?

•From Windows browsers


    –Take Control


•Apple & Linux browsers


    –Take Control

What browser versions are supported?


Can people outside of OCS join a desktop sharing session?

Yes, you can share your desktop anonymously with people outside of your school/campus via Communicator Web Access.

Within CWA properties, select the next hop pool FQDN for anonymous CWA users.


The external user will get an invite such as below via federated IM or email. The external user will select ‘No’ when visiting CWA login page asking if you have a user account.




This is an anonymous desktop sharing session via CWA with someone who does not have an account in OCS. (above)

Comments (19)

  1. markga says:

    Connecting from what to what? PC to PC. PC to Web, Web to PC, web to web?

    It more than likely could be firewall. You should setup a network trace to be sure. Use wireshark network sniff (excellent tool):

    make sure you have the latest R2 Communicator client installed:

  2. markga says:


    It would appear that Alt-A would take back control as the ‘a’ in ‘take back control’ is underlined meaning it can be activated via keyboard but it didn’t activate for some reason. I will check.

  3. Anonymous says:

    The Three UC amigo's posted a nice article with all the details around the new desktop sharing feature

  4. markga says:


    Desktop sharing should be available in Standard Edition as well. Make sure you have 2007 R2 version.

  5. Anonymous says:

    I was asked by a school to provide more detail around the new desktop sharing feature in OCS 2007 R2

  6. markga says:


    Don’t mess with IIS 7.0 permissions. Put those back to what they were.

    To get this to work try this:

    1) Log into CWA

    2) Click ‘Meet Now’

    3) Click ‘Invite’ > ‘Using Email’

    4) Paste the guest URL that into a email

    5) Click URL externally – you will get the Y/N question

  7. markga says:


    Using Communicator Web Access from a Mac, a Mac user can view a desktop sharing session from a PC and take control if allowed. The reverse is not true currently where a Mac user can share a Mac desktop with a PC. This is functionality slated for the upcoming CS14 release.

  8. markga says:


    I have been told it has been tested with up to 100 simultaneous people. Obviously, there are other factors to consider such as bandwidth, app sharing server capacity, etc.

  9. Jenny says:

    is there a keyboard shortcut to take control back when you are sharing control of your desktop?

  10. eddieo says:

    Is there a maximum number of simultaneous people you can share your desktop with?  Thanks!

  11. Marc says:

    I’m not getting the page that asks "Do you have a user account? Y/N" Seems like I went into IIS 7 on x64 2008 server and changed Authentication. Now I only get a sign in that doesn’t always work. What admin tool controls this. I have correct settings everywhere else. Internal accounts work fine.

  12. Marc says:

    Nope, I’ve uninstalled and reinstalled the internal site, but still having the same problem (only communicator web access from control panel). I used to get a sign in with username and password fields. Now I only get a join button or sign in button and an error saying Cannot sign in due to a problem with the network or server.

  13. Marc says:

    Ok, looks like if I click the link to sign on with a different account, I get the Y/N option. Now the only thing I need to fix is desktop sharing. Not loading up for some reason.

  14. Marc says:

    This OCS is unbelieveable! Here’s the likely solution to CWA Desktop Sharing not loading (trying this now, from Experts Exchange link).

    For the CWA you have to add 2 CNAME records.

    1) as.[fqdn cwa dns record]

    2) Download.[fqdn cwa dns record]

    But when using CNAME entries, you also have to renew the certificate which must include the following Subject Alternate Names:

    1. Subject name (example:

    2. CNAME record as (example:

    3. CNAME record download (example:

    Be sure that your CA accepts requests with san’s in it.

    If not, see MS KB 931351 to enable your CA for Certificate requests with san’s.

  15. Sylvain says:

    Great Post !

    Do you know any reason why would I never land on the anonymous login page but instead I get the regular domain login page ?

  16. Deepak Thakkar says:

    While sharing desktop with another person on office Communicator I a getting message ‘Connection is not Established’.

    What can be the reason

  17. kai_luo1918 says:

    I meet same problem ‘Connection is not Established’. How to solve it?

  18. Anish says:

    Desktop Sharing between PC and MAC – Can a MAC user take control of the PC and vice-versa or is it just a view only session?

  19. Dave says:

    Is this feature only available in OCS Enterprise R2?  I do not get the sharing option in the communicator client and cannot find the configuration screen in the administrator console.  Any help is appreciated.

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