[VoiceOps] RTP End?

John S. Robinson jsr at communichanic.com
Thu Sep 13 11:57:29 EDT 2012

Clint -- The answer to this is fairly straightforward.
//If/ your Empirix Hammer is providing media quality monitoring, it 
/must/ rely on the the actual RTP media stream that it is monitoring.

A media stream is defined as Source IP:Port plus Destination IP:port 
plus *SSRC. *SSRC is often over overlooked, but strict media gateways or 
media relays /may/ refuse to process any further RTP packets when SSRC 
or Source IP:port changes without any new SDP offer-answer.

RTP Start is established when the the *first *packet is received on the 
*Destination* IP:port negotiated by SDP offer:answer.   At that time the 
RTP monitor (or any strict media handler) /learns/ the *Source* IP:Port, 
and the SSRC

As someone else has pointed out, there is no "RTP end" packet.  So "RTP 
end" is declared when there are no further media packets received on the 
stream, defined by Source IP:Port plus Destination IP:port *plus* 
*SSRC*.   This may happen at any time in an established session.   If 
something "goes wrong" in a media stream, the "RTP end" /may /be 
declared well before any sip method (usually BYE) which ends the 
session.    This explains why you  "have seen this many times preceeding 
a BYE - or even without a BYE."    Any "RTP end" which occurs 
substantially before a BYE /without/ an almost immediate new "RTP Start" 
indicates the potential media failure.   If that happens, the media 
failure may be the root cause of the BYE.   In that case, you may be 
loosing revenue.

None of this is in any way related to presence or absence of RTCP.

Hope this helps.   If you would like any further discussion, please 
contact me privately.

Best regards,

    Communichanic Consultants, Inc
    John S. Robinson <mailto:jsr at communichanic.com>, President

On 9/12/2012 17:25, Clint Mojzes wrote:
> We are using a tool called Empirix Hammer to analyze and report on our 
> network traffic. This tool as uncovered something that it calls "RTP 
> End" and I'm trying to get a better definition of what it means. I 
> haven't been able to find anything online, including RFCs etc. 
> Basically when the Hammer see this special packet, it is when a phone 
> or media gateway is tearing down a call. Logically speaking it is 
> identifying the end of a media stream, but I'm looking for a technical 
> definition. Can anyone provide any insight?
> Thanks,
> -Clint
> **
> _______________________________________________
> VoiceOps mailing list
> VoiceOps at voiceops.org
> https://puck.nether.net/mailman/listinfo/voiceops

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