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The SBC Core allows relay support for MS Lync/Skype for business Desktop sharing application media streams. The application sharing media streams are relayed transparently through the SBC over TCP connections. Interactive Connectivity Establishment (ICE) is completed over this TCP connection by the peer endpoint.

When the SBC communicates with an MS Lync/Skype for business client, the SBC expects the TCP connection to be established by the peer endpoint. Hence, the SBC does not initiate the TCP connection on its own. This is an acceptable behavior as the SBC is not situated behind a Network Address Translator (NAT).

The SBC can also be configured to initiate and establish the TCP connection towards the third-party device to support interoperability when the  SBC relays an application sharing media stream. This functionality is supported only when the Lync compatible peer endpoint and the SBC are not situated behind a NAT. 

The SBC includes the following MS Lync/Skype functionality:

  • Application sharing media streams in Session Description Protocol (SDP)
  • Accept and establish TCP connection with media IP/port of the peer application stream
  • Exchange STUN messages over the TCP connection to negotiate ICE
  • Relay desktop share data transparently end-to-end once ICE is completed

If the parameter sourceAddressFiltering is enabled, the SBC filters incoming media packets, which do not match the expected source IP address and UDP port. In the Lync desktop sharing, the SBC accepts incoming TCP connection that matches any of the source addresses in the candidate lines of the ICE SDP received from the peer. When the SBC has not received an SDP from the peer, before the peer attempts to establish the TCP connection, the SBC ignores source address filtering and allows the TCP connection to be established on the application sharing stream.

The existing fields Media Stream Data (230 of STOP record) and Media Stream Stats (231 of STOP record) are updated to log TCP/LYNC/APPSHARE when the SBC accepts a media stream of media type of desktop sharing on protocol TCP/RTP/AVP or TCP/RTP/SAVP. For more information, refer to the section CDR Field Descriptions.

The MS Lync/Skype Remote Desktop Sharing feature is supported on the following platforms:

  • SBC 5000 series
  • SBC 7000
  • SWe on KVM
  • SWe on VMware