OCS directly to a Voip Provider RRS feed

  • Question

  • Hello,


    I've read lots of stuff about setting up OCS to connect to PBXs via media gateways, but is it possible to get OCS to connect directly to a voip provider on the internet?


    For instance, as part of my testing, i have signed up for a free account with DrayTel and have been supplied with a logon server, username and password, along with a standard PSTN telephone number for people calling in the old fashioned way. How can I (if it is, indeed, possible at all) get OCS to authenticate with the voip provider's server and route all non-internal traffic to out via that connection?


    If my company decides to go with OCS on release, this is likely the way we will want to go, as we are wanting to rip out our old PBX, bin it and route all voice traffic via our fibre connection to the net (thereby binning our ISDN30 and saving a nice packet of money!)


    Can this be done with OCS only, or do we still need some additional hardware/software as a gateway to authenticate with the voip provider? If we do require an additional gateway, are there any suggestions (preferably for software-based gateways, as I cannot purchase any hardware for a beta evaluation)


    Failing all that, has anyone managed to get OCS to communicate directly with a 3CX software IP-PBX, as that was the other option I was trying should all else fail.





    Wednesday, May 30, 2007 7:21 PM


  • Dan,


    OCS can communicate directly with telephony platforms that support CSTA over SIP.  If DrayTel provides access via this protocol then you may be able to connect directly with them.  More likely they provide standard SIP interoperability, which will only work with OCS if they can communicate SIP over TCP (as opposed to UDP).  In this case you would need a Mediation server to provide the translation between DrayTel and OCS.



    Wednesday, May 30, 2007 7:32 PM

All replies

  • Dan,


    OCS can communicate directly with telephony platforms that support CSTA over SIP.  If DrayTel provides access via this protocol then you may be able to connect directly with them.  More likely they provide standard SIP interoperability, which will only work with OCS if they can communicate SIP over TCP (as opposed to UDP).  In this case you would need a Mediation server to provide the translation between DrayTel and OCS.



    Wednesday, May 30, 2007 7:32 PM
  • Hi Z,


    Thanks for the quick response! I don't believe they handle CSTA (altohugh I'm not 100% on that. I will check with them)


    Assuming the likely outcome, however and I need to use a mediation server to communicate (which I what I was assuming I would have to do anyway) how do I get the mediation server to authenticate with the voip provider? All there seems to be is the option to add an IP address for the next hop. How do I provide a sip username and password to authenticate onto their server?


    I assume this ability must be in there somewhere, otherwise how does OCS make secure connections to other SIP platforms?





    Wednesday, May 30, 2007 7:41 PM
  • Remember that OCS is not a PBX.  To my knowledge, OCS does not and will not support a direct connection to a VoIP provider in this manner.  Typically what you would do is connect an IP PBX to the provider (for example, Asterisk, Linksys SPA9000, etc.) and then use the Mediation Server to connect to this PBX.  As long as the PBX supports SIP over Tcp you should be fine.  Asterisk requires SIP Express Router to translate from UDP to TCP and vice versa.  I'm currently in the process of finding out if the Linksys supports SIP over TCP (posted to their forum yesterday).  If so, it would make a great small biz PBX/Enterprise Voice package.


    Wednesday, May 30, 2007 8:30 PM
  • Thanks for the help, Z. Kinda what I was expecting. it's a shame, really, because it would be hugely useful if OCS could do this. I guess I'll have to wait until OCS 2010 (or whatever it will be) before we see functionality like that.


    I'll carry on trying with the 3CX IP-PBX then and see if I can get anywhere with that. If not, I'll have a look at the Linksys that you mentioned and see if I have any more luck there.



    Wednesday, May 30, 2007 9:49 PM
  • I don't have experience with 3CX products, but their forum site admin is a little off on his understanding of LCS/OCS.  Check out these two threads where he insists that the MS offerings are competitors (3CX is a PBX, neither LCS or OCS is) and that the MS products aren't standards based (when did SIP fall off the standards list?).





    For the short version, here are my favorite quotes from the site admin:


    "We dont support or plan to support any proprietary standards of Microsoft LCS or OCS. We support SIP and if Microsoft supports it then it would work."

    "We have no plans to integrate with OCS."

    "I doubt whether [OCS] will be popular, but only time will tell of course."


    He does say that CSTA is not supported, so the real question is whether or not they do SIP over TCP or UDP (both are allowed per the RFC).  If TCP is supported then theoretically you could make their PBX work with OCS using a Mediation Server, but since this company is so far in left field about the interoperability you might want to explore other options.  If I were them I'd try to be friends with the 500 lb. gorrilla rather than fight it.    They might even make some money doing that.


    I digress...


    Thursday, May 31, 2007 1:39 AM
  • Hi Dan,


    To connect you OCS to an SIP Trunk you may also want to look at products from Ingate (SMB) or Intertex (SOHO).





    I know they work a lot with ITSPs and have support for digest authentication as well as SIP over any transport method and I don't think it should be any problem to put those products between the Mediation server and the ITSP.



    Thursday, May 31, 2007 7:09 AM
  • Hi Z,


    Yeah, it looks like they don't know too much about OCS, so their forum is pretty much useless for any help! Although it does look like there are a fair few other customers of theirs who want OCS integration, so perhaps they'll wake up. Still, I guess if there only problem is that OCS doen't support SIP (and we all know it does) then hopefully I will be able to use it anyway. I'll just have to try and work it out myself.




    Thanks for the links. I'd looked at both those products previously and they look good, but unfortunately, I am not allowed to purchase any hardware for testing, so I'm stuck to having to use software gateways. They might be useful if we decide to go to a production deployment, but for right now it's more than I can get a hold of.



    Thursday, May 31, 2007 12:54 PM
  • Verizon offers a service called "IP Trunking" for this but they limit what solutions it will drive and OCS is not on their list /yet/. 



    Friday, June 1, 2007 9:08 PM
  • Thanks for that, Trevor.


    Do you know if Verizon operate in the UK, or are they America only?

    Monday, June 4, 2007 9:49 AM

    can you tell how to provide this function ? Which server is need and what version to use CSTA over sip and cisco gateway
    Tuesday, April 29, 2008 2:13 PM
  • Hi,

    Right now, as a few people have mentioned, OCS does not support direct SIP trunk connectivity to external VoIP providers. This is something that really should be coming, probably in future releases, and we should be getting more info about the exact support that OCS will have for this kind of thing once MS has released the roadmap for OCS.


    That being said, you can get OCS to integrate with some IP PBXs (while unsupported). In order to do this, at a minimum you need to have the OCS Standard Edition server (or EE front-end) and an OCS mediation server. The mediation server is what speaks SIP to external parties.


    And again, as others have noted, OCS only supports SIP over TCP, and not all providers / PBXs do the same.


    Lastly, you don't need CSTA to integrate OCS and an IP-PBX. CSTA is only needed when doing RCC, presence integration, or dual-forking with presence gateways (like CUPS or GETS).




    Wednesday, April 30, 2008 5:19 PM

    Has anyone successfully managed to get OCS hooked up to a SIP Trunk provider??? Even maybe used 3CX like mentioned above?


    Trying 3CX at the moment but not sure how to configure 3CX to let OCS calls through.


    Much appreciated!


    Sunday, May 11, 2008 11:51 PM
  • Hi hfourie,


    yeah Smile  


    I have written a pbxnsip Wiki page with a guide for pbxnsip-OCS2007 setup. Including helpful screenshots. Please take a look, how easy it is:



    Best Regards

    Jan Boguslawski

    ITaCS GmbH Berlin, www.itacs.de

    Thursday, May 15, 2008 2:53 AM

    Great. Thanks for that. Im going through it right now. Will let you know if I run into issues.


    Were you able to connect Exchnage 2007 UM into this aswell, ie to use Auto Attendant, OVA etc. If so, do I point the Exchange to the pbxnsip server or Mediation server?


    Again, much appreciated.

    Thursday, May 15, 2008 9:30 AM
  • Yep. Connecting pbxnsip to Exchange 2007 UM is no problem. You can use the Auto Attendant, Outlook Voice Acces, Directory Search and Call ("John Smith" - "Call the cell!" ect. Its easy to configure. Less configuration steps than with OCS. Smile


    Best regards,



    Wednesday, May 21, 2008 2:49 AM
  • If you are in Europe take a look at http://www.interouteone.com/





    Wednesday, June 4, 2008 11:06 PM
  • Hi all,


    Somewhere in this thread it is stated that OCS cannot link to external SIP providers.  This is untrue.  Interoute is offering this exact service:  natively connecting SIP to OCS.  You define the SIP server of this provider as the next hop on you mediation server.  We did tests with them that worked perfectly.  The only disadvantage is that you currently need one mediation server per SIP trunk. If you would like to use more than one SIP trunk it costs hardware and complicates routing.


    Therefore we opted for a gateway of NET (www.net.com, see VX1200) that can handle advanced routing between OCS and external SIP trunks and ISDN cards.  The VX1200 is the next hop on the Mediation Server, and handles all routing to the ISDN lines and the SIP trunks.  It can also convert UDP to TCP and vice versa on the fly.  In our case it also connects to non-OCS SIP phones registered to the gateway, analogue devices (behind small gateways using UDP) and Exchange (for incoming T.38 fax).





    Best Regards




    Thursday, June 5, 2008 7:27 PM
  • Hi all,

    Just to be clear - I mentioned in this thread that OCS doesn't support connectivity directly to SIP providers. You can definitely get it to work, but you will notice that no 3rd party SIP service is listed on the supported interoperability list. by connecting through a quintum or other supported gateway, though, you are doing it the way MS will support you.


    Along those lines, you can connect to a cisco callmanger using SIP no problem - it just isnt' supported yet either - you need to connect it through the gateway to be supported.





    Thursday, June 5, 2008 8:20 PM
  • Also, my original posts are over a year old now and a lot has changed.  As Matt mentioned the supportability remains the same but many of us have deployed fully functional telephony solutions (such as a SIP trunk connections) since that time.
    Wednesday, June 11, 2008 1:56 PM
  • Hi Mike & Matt,


    Have you been using SBC in the configurations you have done to the SP? If so what are you using?





    Wednesday, June 11, 2008 2:18 PM
  • Hey Chris - I have not yet used SBC as the provider in any of my deployments.
    Wednesday, June 11, 2008 3:56 PM
  • Hi Mike,


    I was talking about a session border controller used in either the DMZ or as the firewall to the service provider. Sorry I didnt state that clearer.




    Wednesday, June 11, 2008 4:03 PM
  • Whap was your result in connecting SPA9000 to OCS, cause I m looking for informations about this (I'm trying to do soo)
    Friday, August 28, 2009 1:28 PM