Pipex RTP problem

Discussion in 'UK VOIP' started by Dave Higton, Jun 13, 2010.

  1. Dave Higton

    Dave Higton Guest

    I only use VoIP on an occasional experimental basis. I was getting
    /very/ badly chopped audio reception, although the transmission was
    OK. Eventually I put Wireshark and Wiresalmon on, and found that I
    only receive an average of 1 in 10 RTP packets once the first 10
    have been delivered.

    This is with two UA/OS combinations (my own app on RISC OS, and
    Ekiga 2.09 on SuSE 10), and two VoIP service providers (Sipgate
    and VoIPTalk).

    The only common factors, AFAICS, are my Internet service provision
    (Pipex) and my modem/router/LAN here. The modem/router is a Netgear
    DG834Gv4. The LAN is implemented on a cheap Edimax 16 port switch.

    There is no other significant network traffic going on - no browsing,
    no media playing, etc. and I saw the same results yesterday evening
    and this morning, so I can't reasonably blame network or Internet

    Anyone ever seen a similar issue?

    Dave Higton, Jun 13, 2010
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  2. Dave Higton

    alexd Guest

    Sounds a bit fishy to me.
    I'd never suspect a 'dumb' device like a plain old ethernet switch to be
    the cause of this sort of issue, but might as well try eliminating what
    you can. Try upgrading/downgrading/going sideways with the firmware on
    the router as well in case it's some obscure NAT bug. Having said that,
    DG834Gv4 is in widespread use, so if it frequently eats RTP I'm sure
    this wouldn't be the first we'd hear of it.

    Are you getting packet loss to anywhere else? ping and iperf in UDP mode
    should help you spot this.
    Nope. In general when you see weird shit like this, it's either protocol
    inspection in the router [not likely on a Netgear] or misconfigured
    traffic throttling by the ISP.
    alexd, Jun 13, 2010
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  3. Are you setting type of service parameters? Enhanced service has a
    strict quota, so if you request it and go over budget, you could get hit
    David Woolley, Jun 13, 2010
  4. Dave Higton

    Bodincus Guest

    (13/06/10 14:29), Dave Higton:
    Beware of any anti-DDOS firewall setting.
    Many firewalls see the UDP RTP traffic as a flood and stop the packets.
    Either reconfigure the level where the DDOS triggers the dam, or disable
    it altogether.

    Bodincus - The Y2K Druid
    Law 42 on computing:
    Anything that could fail, will break at the worst possible mom%*= [email protected]@
    # Access Violation - Core dumped
    # Kernel Panic
    Bodincus, Jun 13, 2010
  5. As a curiousity, which pipex network are you on? I know this doesn't
    happen with homecall (ex C&W/bulldog).
    I can certainly vouch for both voiptalk (use them at home and work) and
    sipgate. Nice to know that there's some work on a Risc OS VoIP product,
    the last one of these I heard about was around 12 years ago when someone
    ported Speak Freely.
    I can't really comment on the DG834Gv4, I stopped buying Netgear kit
    years ago, If there are any QoS settings on it, have you tried turning
    them off?
    It would be very unusual to see this sort of problem being the fault of
    a switch that wasn't an expensive one :)(
    I have recently seen something quite similar, which turned out to be the
    QoS on a router not working properly. (The router in question runs
    linux, so I may fix this by writing my own QoS script).
    Thomas Kenyon, Jun 14, 2010
  6. Dave Higton

    Dave Higton Guest

    In message <[email protected]>
    It was originally a Pipex Xtreme Solo account - is that what you

    Anyway, it's not Pipex's fault as it turns out...
    I can't remember why I started on it. It just interested me. My
    app is written from scratch, not ported. As such, it will only
    cope with the simplest of call scenarios, but it's been a very
    interesting learning experience. Now I find myself one of the
    leading VoIP experts where I work :)

    Dave Higton, Jun 15, 2010
  7. Dave Higton

    Dave Higton Guest

    In message <[email protected]>
    Thanks, Bodincus, that was it. The DG834 has DOS detection, and
    presumably mitigation, although I can't find anywhere to configure
    it, other than turning it off altogether. The incoming RTP - and
    even the incoming SIP - were seen as DOS attacks, despite my
    having opened up and forwarded the ports (or else I wouldn't be
    able to receive anything at all). Not the smartest programming,

    However, a firmware upgrade addressed the problem, and seems to
    have solved it.

    Dave Higton, Jun 15, 2010
  8. Dave Higton

    Dave Higton Guest

    In message <hv3gsi$iqs$>
    Thanks, Alex, yes, it was the router's firmware, as I explained in
    my reply to Bodincus.

    Dave Higton, Jun 15, 2010
  9. Dave Higton

    Bodincus Guest

    (15/06/10 20:06), Dave Higton:
    Been there, seen that, got the t-shirt.
    It's 5 years I'm sniffing around VoIP, and I'm now running my own
    telephony business, so I've seen it (almost) all.

    Bodincus - The Y2K Druid
    Law 42 on computing:
    Anything that could fail, will break at the worst possible mom%*= [email protected]@
    # Access Violation - Core dumped
    # Kernel Panic
    Bodincus, Jun 15, 2010
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