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Troubleshooting and limitations with Lync / Skype for Business and Pexip Infinity integrations

This topic describes any limitations and provides troubleshooting guidance when integrating Microsoft Lync and Skype for Business* with Pexip Infinity. It covers the following issues:

* Note that where this documentation refers to "Lync/SfB", it represents both Microsoft Lync and Skype for Business unless explicitly stated otherwise.

Lync/SfB client does not connect to Pexip Infinity conference


  • Verify that a Virtual Meeting Room with the alias being dialed exists on the Management Node.
  • Verify that the Conferencing Node receives the SIP INVITE request from the Lync/SfB client (via the FEP):
    • Management Node support log (Status > Support log)
    • Lync/SfB FEP logging tool


If the Lync/SfB client fails to connect to the conference altogether, we need to verify that the alias exists on the Management Node. After that has been verified, check if the Conferencing Node receives the SIP INVITE request from the Lync/SfB client. This can be done both on the Conferencing Node (with the support log) and on the FEP serving the Lync/SfB client (using the Lync/SfB debugging tools.

A normal SIP call flow between a Lync/SfB client and the Pexip Infinity Conferencing Node should be:

Lync/SfB client   Pexip Infinity
  INVITE (with SDP) --->  
  <--- 100 TRYING  
  <--- 180 RINGING  
  <--- 200 OK (with SDP)  
  ACK --->  

After ICE negotiation has completed between the Lync/SfB client and the Conferencing Node, the Lync/SfB client should send a second INVITE to signal the ICE negotiation completion. If this second INVITE is not seen, this is a strong indication of a media connectivity issue between the two peers.

Lync/SfB client can successfully connect to the Pexip Infinity conference, but audio and/or video is not working in one or both directions


  • Verify that the Lync/SfB client is correctly configured with an audio and video device.
  • Verify that the call from the Lync/SfB client is placed as a video call rather than a Lync/SfB (audio-only) call.
  • Verify (with SIP logs) that the SIP call setup behaves as expected:
    • INVITE from Lync/SfB client should contain m=audio and m=video lines in SDP
    • 200 OK response from Pexip Infinity should contain m=audio and m=video lines in SDP.
  • Verify that firewall configuration permits relevant media traffic.
  • Verify that Lync/SfB client receives RTP media from Pexip Infinity (using for instance Wireshark).
  • Verify that Pexip Infinity Conferencing Node receives RTP media from Lync/SfB client (using for instance tcpdump).

Collecting SIP logs using the Lync/SfB Server Logging Tool

The Microsoft Debugging Tools can be downloaded from:

The default location for installation of the logging tool is:

  • Lync 2013: C:\Program Files\Microsoft Lync Server 2013\Debugging Tools\OCSLogger.exe;
  • Lync 2010: C:\Program Files\Common Files\Microsoft Lync Server 2010\Tracing\OCSLogger.exe
  • Skype for Business Server 2015: C:\Program Files\Skype for Business Server 2015\Debugging Tools\CLSLogger.exe

Note however that a different location may have been chosen at the time of installation.

After opening the logging tool, the following selection is normally suitable for initial troubleshooting of failing calls between Lync/SfB and the Pexip Infinity Conferencing Node:

  • Components: SIPStack, InboundRouting and OutboundRouting

    (Note that the InboundRouting and OutboundRouting components are only available on a FEP)

  • Level: Information
  • Flags: All Flags

To use the Lync Server logging tool:

  1. Select Start Logging and place a new call from the Lync/SfB client towards the Pexip Infinity conference alias.
  2. After the call has failed, select Stop Logging.
  3. Select View Log Files.
  4. Select View in the dialog which appears, and save the resulting text file in a suitable location.

Conference status shows backplanes to a merged Lync/SfB meeting with no participants

After a Pexip VMR has been merged with a Lync/SfB meeting, when viewing the conference status information for the VMR you may see one or more backplanes to the Lync/SfB server where there are no participants connected to that Lync/SfB node. One way in which this can occur is if a Lync/SfB client dials into a Pexip VMR, invites other Lync/SfB contacts into the meeting and then all of those participants disconnect.

Whenever a Lync/SfB client that is dialed into a Pexip VMR adds a contact into the meeting, an adhoc Lync/SfB meeting is created and it is merged with the Pexip VMR. A backplane is established between the Lync/SfB meeting and the Pexip VMR. That backplane will continue to exist even if all of the participants in the Lync/SfB meeting disconnect. The backplane is only taken down when the Pexip VMR conference ends.

Therefore if the Lync/SfB client and any other Lync/SfB contacts that had been in the adhoc Lync/SfB meeting all disconnect, you will continue to see the merged Lync/SfB meeting as a remote media node but with no participants connected to it.

Note that the remote media node of a merged Lync/SfB meeting is identified by the address of the Lync/SfB client that initiated the Lync/SfB meeting.

Poor image quality and delays when sharing content from Lync/SfB

This can occur when the maximum inbound or outbound call bandwidth is too low.

Ensure that the Maximum inbound call bandwidth and Maximum outbound call bandwidth advanced configuration settings for the Virtual Meeting Room or Virtual Auditorium is at least 1024 kbps.

Received content can be slow to update

Updates to content being received by a Lync client via Pexip Infinity can in some cases be slow to load when viewed in "fit to window" mode. When the same content is viewed in "actual size" mode, the images are updated as expected. This occurs when content is being sent via RDP; content sent via Video-based Screen Sharing (VbSS) is not affected. To resolve this issue, ensure that VbSS is enabled on the Lync / Skype for Business server, and on Pexip Infinity (Platform configuration > Global settings > Connectivity > Enable Lync / Skype for Business Video-based Screen Sharing (VbSS).

DNS resolution failures

The following error messages indicate that DNS is not resolving addresses correctly:

  • Transaction failed UPDATE appears as the disconnect reason when viewing participant status
  • RFC3263 lookup failure appears in a support.dns log entry in the support log

Sending messages from a Lync/SfB client to a locked conference

If a Lync/SfB client initiates an IM session with a locked Pexip Infinity conference and attempts to send a message, it will appear to the Lync/SfB client as though the message has been successfully sent.

However, other participants in the Pexip Infinity conference will not see the message. The Lync/SfB client will temporarily appear in the conference participant list but cannot be allowed in to the locked conference (as they are not currently sending any audio or video).

Lync/SfB participants do not receive presentations / content sharing

Lync/SfB participants will not receive presentation content if Pexip Infinity is not configured to enable outbound calling to Lync/SfB clients.

You must configure Pexip Infinity to enable outbound calls to Lync/SfB clients. This includes ensuring that every Conferencing Node is configured with a TLS server certificate that is trusted by the Lync/SfB server environment, and that every node has its unique SIP TLS FQDN setting configured. See Certificate creation and requirements for Lync / Skype for Business integrations for more information.

Video calls from a Lync 2010 client for iOS only connect with audio

Outbound video calls made from the Lync 2010 client for iOS may only connect using audio rather than automatically escalating to video as expected. This is currently the expected behavior with this type of Lync client.

Lync/SfB presenter sees "Someone has joined and can't see what's being presented or shared" notification

If a Lync/SfB participant in a Lync/SfB meeting is presenting while another device joins the Lync/SfB meeting via the Pexip Distributed Gateway, the Lync/SfB presenter will see a "Someone has joined and can't see what's being presented or shared" notification.

However, the gateway participant will be able to see the presentation. The notification will disappear after approximately 15 seconds.

Lync/SfB users see low-resolution presentations in small scale

If a standards-based endpoint transmits a dual stream presentation at a very low resolution, the transcoded presentation will be sent in native resolution to any connected Lync/SfB clients.

This may create a sub-optimal experience depending on the PC screen resolution of the Lync/SfB end-user PC.

Can only make audio calls when using a Cisco VCS for call control

If a Cisco VCS is used as call control between a Conferencing Node and a Lync 2013 FEP, only audio calls are possible.

The FEP and the Conferencing Nodes should be neighbored directly and then audio and video calls will work as expected.

No video on Lync for Mac or Lync 2010 (PC) in Lync/SfB meetings

Video from Lync 2010 or Lync for Mac clients will not be seen on endpoints connected via Pexip into Lync/SfB meetings.

Pexip Infinity does not currently support sending an RTV video stream into AVMCU-hosted conferences. As a result, video from clients that only support RTV (such as Lync 2010 and Lync for Mac) will not be visible to those endpoints.

However, clients such as Lync for iPhone, Android, Lync 2013 PC, Windows phone, Skype for Business 2015 and so on, all support video when connected via Pexip into Lync/SfB meetings.

Poor sound quality

AVMCU calls support a maximum of G.722 (7 KHz audio), while Pexip Infinity supports up to AAC-LD (48 KHz audio). Under certain circumstances (for example, a meeting room with poor acoustics and many people speaking) there may be a perceptible difference in sound quality between an endpoint when using G.722 and the same endpoint when able to use a wider-band codec.

Problems connecting to Lync/SfB meetings via the Virtual Reception (IVR gateway)

The following table describes the typical problems and suggested resolutions for issues related to connecting to Lync/SfB meetings via the Virtual Reception (IVR gateway).

Symptom Possible cause Resolution
After entering the Conference ID, the call tries to connect to the user that scheduled the meeting. The relevant Call Routing Rule does not have Match against full alias URI selected. Ensure that Match against full alias URI is selected.
After entering the Conference ID, you get a "Call Failed: Conference extension not found” error. The relevant Call Routing Rule does not have a trailing .* in the Destination alias regex match field. Ensure that the Destination alias regex match field has a trailing .*

For more information, see Routing indirectly via a Virtual Reception (IVR gateway).

Audio-only calls when using a VCS for call control

If a Cisco VCS is used as call control between a Conferencing Node and a Lync 2013 FEP, only audio calls are possible.

Lync FEP and Conferencing Nodes should be neighbored directly then audio and video calls will work as expected.

Pexip VMR participants can't see shared PowerPoint files

If participants connected to the Pexip VMR in a Lync/SfB Fusion or gateway call can't see shared content when a Lync/SfB user presents PowerPoint files, the most likely reason is that SIP TLS verification mode is On (Platform configuration > Global settings) and that the Management Node does not trust the Lync/SfB Front End server / FEP or Web Conferencing Edge device (it is always the Web Conferencing Edge for federated connections). If the server is not trusted, Pexip participants will not see any content.

If this is the case you will see an "unknown CA" message similar to this in the Pexip Infinity support log:

Level="ERROR" Name="support.ms_data_conf.ms_data_conf" Message="PSOM connection attempt 1 failed" Remote-address="lync-fep.example.local" Remote-port="8057" Error="SSL Alert" Reason-code="0x230" Alert-type="fatal" Alert-description="unknown CA"

To resolve this, ensure that the trusted CA certificate of the relevant Lync Front End server / FEP or Web Conferencing Edge device is uploaded to the Management Node (Platform configuration > Trusted CA certificates).