A few doubts w.r.t RTCP packets...

Discussion in 'VOIP' started by Stephen Regan, Feb 12, 2005.

  1. Hi,

    Let me give a brief description of my project before I put forth my
    doubts. I am developing a project to develop a VoIP quality monitoring
    software that resides in a dedicated machine and captures the RTCP
    packets for voice quality measurement. The initial version will not
    involve in voice recording and other stuffs. Just plain RTCP packet
    capture and decoding... Ok. Now, to my queries..

    Is'nt it mandatory for all VoIP endpoints to send RTCP packets when
    they are engaged in a call? Looks like SJPhone does not send them. Is
    this quite natural or is it a limitation in SjPhone. What are the
    consequences of this.

    Next, I tried with Window Messenger. Messenger does send RTCP packets
    at regular intervals and I am able to recieve them properly. But, I am
    able to receive the packet only from the machines that are involved in
    the conversation. How can I get them from a separate machine that is
    not actively involved in the call? I think RTP/RTCP spec does allow
    such third party devices/applications to decode rtcp information. How
    do I enable this??

    Any pointers are greatly appreciated.

    With Regards,
    Stephen Regan.
    Stephen Regan, Feb 12, 2005
    #1
    1. Advertising

  2. Stephen Regan

    Yaser Doleh Guest

    Stephen Regan wrote:
    > Hi,
    >
    > Let me give a brief description of my project before I put forth my
    > doubts. I am developing a project to develop a VoIP quality monitoring
    > software that resides in a dedicated machine and captures the RTCP
    > packets for voice quality measurement. The initial version will not
    > involve in voice recording and other stuffs. Just plain RTCP packet
    > capture and decoding... Ok. Now, to my queries..
    >
    > Is'nt it mandatory for all VoIP endpoints to send RTCP packets when
    > they are engaged in a call? Looks like SJPhone does not send them. Is
    > this quite natural or is it a limitation in SjPhone. What are the
    > consequences of this.
    >


    I don't think it is mandatory. I may be wrong.

    > Next, I tried with Window Messenger. Messenger does send RTCP packets
    > at regular intervals and I am able to recieve them properly. But, I am
    > able to receive the packet only from the machines that are involved in
    > the conversation. How can I get them from a separate machine that is
    > not actively involved in the call? I think RTP/RTCP spec does allow
    > such third party devices/applications to decode rtcp information. How
    > do I enable this??
    >


    How so you capture the packets on the same machine and how are you
    attempting to capture them on a third machine? How is that third machine
    connected to the network ?

    > Any pointers are greatly appreciated.
    >
    > With Regards,
    > Stephen Regan.
    >
    Yaser Doleh, Feb 12, 2005
    #2
    1. Advertising

  3. I used ethereal to read the packets in both the case. In the first
    case, ethereal was running in one of the endpoint machine and in the
    second case, it was running in a third machine. All the three machines
    are in the same network and are connected to the same switch.
    Stephen Regan, Feb 14, 2005
    #3
  4. I am not able to see my reply. Hence reposting it :-(. Plz ignore this
    if its duplicated.

    I used Ethereal to capture the packets. In the first case, Ethereal was
    running in one of the endpoint machine. In the second case, I tried
    running ethereal in the machine in which SIP Server was running, as
    well as a machine that is not involved in the VoIP call, except being
    in the same network as that of the other machines.

    BTW, all machine are in the same network and are connected to the same
    switch.
    Stephen Regan, Feb 14, 2005
    #4
  5. Stephen Regan

    Yaser Doleh Guest

    Stephen Regan wrote:
    > I used ethereal to read the packets in both the case. In the first
    > case, ethereal was running in one of the endpoint machine and in the
    > second case, it was running in a third machine. All the three machines
    > are in the same network and are connected to the same switch.
    >


    The switch probably not passing the packets. All switches don't unless
    you configure them to specificly do. Low cost small switches cannot be
    configured to pass the packets. Try it with some old cheap Ethernet HUB.
    That should work.

    Yaser
    Yaser Doleh, Feb 14, 2005
    #5
  6. Stephen Regan

    SteveRegan Guest

    Yaser,

    Do you mean to say all the RTCP packets will be broadcasted to all the
    machines in the network. Any way, I will check its getting dropped in
    the switch.

    Stephen Regan.
    SteveRegan, Feb 15, 2005
    #6
  7. Yaser,

    Do you mean to say all the RTCP packets will be broadcasted to all the
    machines in the network.

    Any way, I will check its getting dropped in the switch.

    Stephen Regan.
    Stephen Regan, Feb 15, 2005
    #7
  8. Stephen Regan

    Yaser Doleh Guest

    SteveRegan wrote:
    > Yaser,
    >
    > Do you mean to say all the RTCP packets will be broadcasted to all the
    > machines in the network. Any way, I will check its getting dropped in
    > the switch.
    >
    > Stephen Regan.
    >


    No, In the old days when Ethernet used a coax cable or used hubs, any
    packet on the LAN was available for any machine to pickup. Hence you
    could use sniffers to listen to communications between 2 machines using
    a 3rd one. These days Ethernet switches ensure that packets only travel
    between 2 ports and do not send a packet on a port unless it need to. So
    a third machine will not be able to pick up packets not addressed to it.
    I am talking about all ethernet packets (at the physical layer.

    Yaser
    Yaser Doleh, Feb 15, 2005
    #8
    1. Advertising

Want to reply to this thread or ask your own question?

It takes just 2 minutes to sign up (and it's free!). Just click the sign up button to choose a username and then you can ask your own questions on the forum.
Similar Threads
  1. Stephen Regan

    RTCP monitor..

    Stephen Regan, Feb 8, 2005, in forum: VOIP
    Replies:
    1
    Views:
    687
    Roman Nikitchenko
    Feb 9, 2005
  2. Stephen Regan

    Convert RTCP Jitter to milliseconds

    Stephen Regan, Apr 7, 2005, in forum: VOIP
    Replies:
    0
    Views:
    1,392
    Stephen Regan
    Apr 7, 2005
  3. Replies:
    1
    Views:
    6,128
  4. C. J. Clegg
    Replies:
    0
    Views:
    492
    C. J. Clegg
    Apr 16, 2006
  5. Replies:
    1
    Views:
    2,087
    artun
    May 6, 2006
Loading...

Share This Page