#Skype4B: Call via work (Part I)


Skype for Business Server 2015 introduced Call via Work (CvW) and replaced remote call control (RCC) which was available in previous versions of Lync server. It enables integration between Skype for Business and your PBX phone system. A SfB user enabled for CvW can initiate a PSTN call from SfB client and leverages PBX phone to have a call with another user within organization or outside the organization.

How is it different from Remote Call Control?

RCC is a replacement of CvW but doesn’t work in same way, you can understand it in this way: RCC required computer-supported telecommunications application (CSTA) gateway to integrate Lync Server with PBX system while CvW uses Unified Communication Web API (UCWA) as the back-to-back user agent (B2BUA) between Skype for Business Server and PBX systems. Therefore, CvW only work in case you have direct SIP between Skype for Business Server and PBX systems.

Call via Work offers the following for PBX phone users:

  • Click-to-call experience form Skype for Business client
  • IM, App and Desktop Sharing, File Transfer
  • One-click meeting join experience

How does it work?

The end user selects another end user in their Skype for Business client, and clicks the phone icon to call him. Or, during an IM conversation, the end user clicks to call another user they are having the session with. The PBX phone of the user who placed the call starts to ring. The caller ID for this phone shows a global phone number which you have set up to show in the caller ID of all users placing Call Via Work calls. This global phone number is not an actual phone number that corresponds to any one person’s phone. Instead, it is a visual signal to let a user know that this is their own outgoing call, and not an incoming call happening at the same time. When you deploy Call Via Work, you should educate those users about this global phone number and what it means. The user who placed the call picks up their PBX phone. Skype for Business then initiates the voice call to the callee. When the callee answers, the voice call begins. If the two users already had an IM session going, it can continue. Courtesy: Microsoft TechNet

Let’s take an outbound call scenario where Users A which is enabled for Call via Work initiates a call from SfB client to external PSTN number.

  1. User A initiates a call from SfB client.
  2. Skype for Business Server places call to user’s PBX phone.
  3. PBX System routes call and user answer that call.
  4. When Sfb server perceives that call has been answered by local user then it initiates a far-end call by using user A DID.
  5. PBX system routes a call out to PSTN with user’s DID.
  6. Far-end calls answers and call is established.

Once call has been initiated, media will directly flow between both the end points.

Let’s take an another outbound call scenario where Users A which is enabled for Call via Work initiates a call from SfB client to User B within same organization. Here, User B is enabled for call via work and Simulring.

  1. User A initiates a call from SfB client.
  2. Skype for Business Server places call to user’s PBX phone.
  3. PBX System routes call and user answer that call.
  4. When Sfb server perceives that call has been answered by local user then it initiates a call to user B.
  5. Since User B is internal user and enabled for call via work and set to simulring their own desk phone, a ms-skipRnl header is used on an outbound call to force another call out to user B desk phone
  6. User B answers call from either skype client or desk phone and call is established.

Once call has been initiated, media will directly flow between both the end points.

The above examples are simple scenarios but there are many other scenarios which take place when deploy call via work. Rest of the scenarios, I’ll coven in next part of this blog series.

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One thought on “#Skype4B: Call via work (Part I)

  1. Pingback: #Skype4B: Call via work (Part I) – Inside Microsoft Technology – JC's Blog-O-Gibberish

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