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vbss application sharing a-remote candidate RRS feed

  • Question

  • Hello

    Following is the log from skype client .  where there are two different ports for application sharing.  I am thinking the first 45281 (destination port) is for RDP and second  59055 (destination port) is for vbss(video).  Can you confirm if that's what it means?

    also when I do wireshark trace I see both ports being used ..also i wasn't doing  audio or video for this. call. so I am little confused since in this instance vbss met all the prerequisite then I should only see vbss (udp) traffic why am I seeing rdp based sharing also..

    v=0
    o=- 0 2 IN IP4 172.20.104.xx
    s=session
    c=IN IP4 172.20.104.xx
    b=CT:99980
    t=0 0
    a=x-mediabw:applicationsharing-video send=8100;recv=4000
    m=applicationsharing 42011 TCP/RTP/SAVP 127
    a=ice-ufrag:lbMR
    a=ice-pwd:FNRfKT4UaOa4Ka0iv8n64M/m
    a=candidate:2 1 TCP-ACT 2121006591 172.20.104.xx 42011 typ host
    a=crypto:2 AES_CM_128_HMAC_SHA1_80 inline:y2RU/JXKcv/8oll/yvbRGK9UKkGnjStq7WiMlPAx|2^31|1:1
    a=remote-candidates:1 172.21.240.xx 45281 2 172.21.240.xx 45281
    a=setup:active
    a=connection:existing
    a=rtpmap:127 x-data/90000
    a=rtcp-mux
    a=x-applicationsharing-session-id:1
    a=x-applicationsharing-role:viewer
    a=x-applicationsharing-media-type:rdp
    a=x-applicationsharing-contentflow:recvonly
    m=video 42000 RTP/SAVP 122 123
    a=x-ssrc-range:3998478849-3998478948
    a=rtcp-fb:* x-message app send:src,x-pli recv:src,x-pli
    a=rtcp-rsize
    a=label:applicationsharing-video
    a=ice-ufrag:WyGf
    a=ice-pwd:K4XvwF3av9T+mWYYxZ1bmGXX
    a=x-mediasettings:applicationsharing-video=required
    a=candidate:1 1 UDP 2130706431 172.20.104.xx 42000 typ host
    a=cryptoscale:1 client AES_CM_128_HMAC_SHA1_80 inline:y2RU/JXKcv/8oll/yvbRGK9UKkGnjStq7WiMlPAx|2^31|1:1
    a=remote-candidates:1 172.21.240.xx 59055 2 172.21.240.xx 59055
    a=recvonly
    a=rtpmap:122 X-H264UC/90000
    a=fmtp:122 packetization-mode=1;mst-mode=NI-TC
    a=rtpmap:123 x-ulpfecuc/90000
    a=rtcp-mux


    • Edited by mod 13 Monday, February 26, 2018 8:58 PM
    Monday, February 26, 2018 8:53 PM

All replies

  • Hi mod 13,

    Please run the get-CsConferencingPolicy ,check the attribute (ApplicationSharingMode) in the SFB server management shell.

    Which SFB client did you use? VBSS is only provided in the Office 2016 version of the Skype for Business 2016 client, starting with the public release of the 16.x client version (e.g. 16.0.4266.1003).  The rebranded Lync 2013/Skype for Business 2015 15.x client installations do not include this capability and will continue to share content using RDP.

    VBSS is also only available in peer-to-peer SfB sharing sessions and is only utilized on the Present Desktop sharing option.  Selecting any of the other sharing options like Present Program or Present PowerPoint Files will still behave the same as in previous clients.  The PowerPoint File sharing option leverages the Office Web Apps Server which does not actually stream the content and thus VBSS is not applicable here.  The Present Program option does not currently take advantage of VBSS so RDP at a low frame rate is still used.


    Best Regards,
    Leon Lu


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    Tuesday, February 27, 2018 9:03 AM
  • Hello Leon

    I am using SFB 2016 version 16.0.4549.1000 so I know that it is compatible.  also target machine is also using the same version.  And I am well aware of vbss prerequisites and compatibility and feature set

    But I don't think you understood my question.  I have two part questions.

    1) first question is to interpret the sfb logs  in above screenshot and tell me why there are two ports for application sharing on server showing up.  My interpretation is 45281 is  for RDP and other one is for vbss 59055 (since its  in video range) .

    2) Seems like it is using vbss in my case becuase its showing up on remote candidate on sfb logs why wireshark showing traces of both ports on the clients and servers.

    hopefully  I am clear this time.

    thanks 

    Tuesday, February 27, 2018 3:12 PM
  • Hi mod 13,

    Thanks for your waiting.

    Based on my research, about your client logs,  “a=x-mediabw:applicationsharing-video” means the client can use VBSS for the sharing session.

    The first media session “m=applicationsharing 42011 TCP/RTP/SAVP 127” is related to RDP,

    And the second media session “a=label:applicationsharing-video” and “a=x-mediasettings:applicationsharing-video=required” is related to VBSS.

    Both the RDP and VBSS capabilities are advertised in the messages above then the clients will negotiate both sessions even though the content will actually flow through the VBSS session.  In the event that RDP needs to be used (e.g. for remote control) then the clients can quickly switch to using RDP as a legacy fallback option.

    So for your questions, as you said, one port is for RDP and other one is for VBSS, and as the clients will negotiate both sessions, so you will see both the two ports.


    Best Regards,
    Leon Lu


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    Monday, March 5, 2018 7:08 AM
  • I agree with you on first answer that both(RDP and VSSS) of them are negotiated and rdp is selected as fail back.  But my second question was specifically about the traffic itself.  Where I saw vbss ports being used but also rdp ports being used same time on wireshark which was strange. And I was doing just the presentation not any remote control. 
    Monday, March 5, 2018 8:36 PM
  • Hi mod 13,

    Thanks for your waiting.

    On the client side, as the RDP and VBSS are both negotiated, I think there will be traffic on both ports. And I did some research and found for some scenarios, the VBSS may be not available, you could check the following link for more information:

    https://ucvnext.org/2016/02/video-based-screen-share-within-skype4b-and-office365/

     

    Note: This response contains a reference to a third party World Wide Web site. Microsoft can make no representation concerning the content of these sites. Microsoft is providing this information only as a convenience to you: this is to inform you that Microsoft has not tested any software or information found on these sites and therefore cannot make any representations regarding the quality, safety, or suitability of any software or information found there. There are inherent dangers in the use of any software found on the Internet, and Microsoft cautions you to make sure that you completely understand the risk before retrieving any software on the Internet.


    Best Regards,
    Leon Lu


    Please remember to mark the replies as answers if they helped. If you have feedback for TechNet Subscriber Support, contact tnsf@microsoft.com.


    Click here to learn more. Visit the dedicated forum to share, explore and talk to experts about Microsoft Teams.


    Wednesday, March 7, 2018 9:03 AM