Troubleshooting and limitations with Skype for Business and Pexip Infinity integrations

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

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

For a list of known limitations with Pexip Infinity and Microsoft Skype for Business and Lync integrations, see Limitations.

SfB/Lync 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 SfB/Lync client (via the FEP):

    • Management Node support log (History & Logs > Support log)
    • SfB/Lync FEP logging tool
  • Check if the Conferencing Node receiving the call is in maintenance mode.


If the SfB/Lync 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 SfB/Lync client. This can be done both on the Conferencing Node (with the support log) and on the FEP serving the SfB/Lync client (using the SfB/Lync debugging tools).

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

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

After ICE negotiation has completed between the SfB/Lync client and the Conferencing Node, the SfB/Lync 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.

Conferencing Node is in maintenance mode

If a Conferencing Node in a trusted application pool is placed into maintenance mode, and a SfB/Lync server sends a call to that node, the node will respond with 503 Service Unavailable and the call will then fail (SfB/Lync will not try another node in the pool).

Therefore, if you need to place a Conferencing Node into maintenance mode, we recommend that you wait until all SfB/Lync calls on that node have completed, and then you should temporarily remove the node from the trusted application pool and then place it into maintenance mode. The node should then be returned to the trusted application pool after it has been taken back out of maintenance mode.

SfB/Lync 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 SfB/Lync client is correctly configured with an audio and video device.
  • Verify that the call from the SfB/Lync client is placed as a video call rather than a SfB/Lync (audio-only) call.
  • Verify (with SIP logs) that the SIP call setup behaves as expected:
    • INVITE from SfB/Lync 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 SfB/Lync client receives RTP media from Pexip Infinity (using for instance Wireshark).
  • Verify that Pexip Infinity Conferencing Node receives RTP media from SfB/Lync client (using for instance tcpdump).

Collecting SIP logs using the SfB/Lync 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;
  • 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 SfB/Lync 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 SfB/Lync 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 SfB/Lync meeting with no participants

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

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

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

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

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

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 SfB 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 Skype for Business server, and on Pexip Infinity (Platform > Global settings > Connectivity > Enable VbSS for Skype for Business).

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 SfB/Lync client to a locked conference

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

However, other participants in the Pexip Infinity conference will not see the message. The SfB/Lync 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).

SfB/Lync participants do not receive presentations / content sharing

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

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

Content from Pexip participants not included in a Skype for Business / Lync meeting recording

If a Skype for Business client running on Windows 7 attempts to record a Skype for Business / Lync meeting, the recording will not include any content from Pexip participants calling into the meeting through the Infinity Gateway.

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

If a SfB/Lync participant in a SfB/Lync meeting is presenting while another device joins the SfB/Lync meeting via the Infinity Gateway, the SfB/Lync 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.

SfB/Lync 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 SfB/Lync clients.

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

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

The following table describes the typical problems and suggested resolutions for issues related to connecting to SfB/Lync 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).

Problems connecting gateway calls to SfB/Lync clients

The following table describes the typical problems and suggested resolutions for issues related to allowing devices to call SfB/Lync clients via the gateway.

Symptom Possible cause Resolution
The SfB/Lync server returns a 400 Bad request response. The Call Routing Rule towards the SfB/Lync server has the wrong Call target type, such as Lync / Skype for Business meeting direct (Conference ID in dialed alias). Ensure that the Call target is set to Lync / Skype for Business clients, or meetings via a Virtual Reception.

For more information, see Configuring rules to allow devices to call Skype for Business / Lync clients via the gateway.

Gateway clients are disconnected from SfB/Lync meetings

The following table describes the typical problems and suggested resolutions for issues related to gatewayed participants being disconnected from SfB/Lync meetings.

Symptom Possible cause Resolution
Gatewayed participants are disconnected from SfB/Lync meetings. Participant history shows a disconnect reason of "CCCP call disconnected: Conference Terminated - Enterprise User Absent".

All of the SfB/Lync clients have left the meeting and the gateway participants have been timed out.

(Note that "CCCP call disconnected" can also appear in other situations.)

There is a SfB/Lync setting (AnonymousUserGracePeriod) that represents the amount of time an anonymous (unauthenticated) user, such as a gateway participant, can remain in a SfB/Lync meeting without an authenticated user being present in that same meeting. The default value is 90 minutes.

You can check the current value by using the following PowerShell command: Get-CsUserServicesConfiguration and you can set the timeout value with: Set-CsUserServicesConfiguration

For more information, see

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 that are connected to a Pexip VMR that is merged with a Skype for Business / Lync meeting, or that are in a gateway call, can't see shared content when a SfB/Lync user presents PowerPoint files, the most likely reason is that SIP TLS verification mode is On (Platform > Global settings > Security) and that Pexip Infinity does not trust the SfB/Lync 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 > Trusted CA certificates).

Shared PowerPoint files are slow to display to Pexip participants

Depending on the size of the PowerPoint file, it can take a long time to display the presentation content to Pexip participants. This delay occurs while Pexip Infinity waits for the SfB/Lync server to make the presentation files (JPEG images) available.

The time spent waiting is shown in the Pexip Infinity support log, for example:

Level="INFO" Name="support.ms_data_conf.ms_data_conf" Message="Got download information for all PowerPoint JPEGs" Content-ID="1" Ppt-title="example.pptx" Download-URL-Base="" Waited="118.913 seconds"

Occasional dropped video frames

On rare occasions, some SfB/Lync users in a SfB/Lync meeting may occasionally experience dropped video frames from VTC endpoints that are gatewayed into that meeting.

Pexip only transmits low resolutions to mobile SfB clients

A mobile SfB client (iOS and Android), or SfB Mac client that is dialed into a Pexip Infinity VMR will never request anything higher than 360p. This means that although Pexip Infinity may receive a higher resolution video from the SfB client, it will only send up to a maximum of 640x360 to the SfB client (and limited to 180p to mobile and 360p to tablet devices).