Question about Packet Jitter
Before you get down into the weeds with the math... All the ITU docs that I've read portray the "network" as set of "non-rtp-aware, forward-as-fast-as-you-can router-type-things that probably have some qos capability". The "edge" is implicitly defined as the first occurrence of a jitter buffer. As near as I can tell, there are no rtp jitter buffers in an ITU "network" for which all this fancy math applies. If you transcode, scrub media with a ditech pvp, or otherwise implement anything that knows it should generate an rtp stream by sending a packet every X milliseconds, the ITU math is bounded by that device. If the SBC in your example transcodes or has a jitter/loss-concealment buffer, it *is* the edge, and you cannot average the link jitters as described in the ITU docs. David Hiers CCIE (R/S, V), CISSP ADP Dealer Services 2525 SW 1st Ave. Suite 300W Portland, OR 97201 o: 503-205-4467 f: 503-402-3277 -----Original Message----- From: voiceops-bounces at voiceops.org [mailto:voiceops-bounces at voiceops.org] On Behalf Of Jim Dalton Sent: Friday, October 29, 2010 6:43 AM To: 'Schwarz, Albrecht (Albrecht)'; voiceops at voiceops.org Subject: Re: [VoiceOps] Question about Packet Jitter
VoIP performance experts should be familiar with
- ITU-T Y.1541 concerning IPDV (IP packet delay variation = jitter); there are many sections on IPDV, particularily also on "aggregated PDV";
[JD wrote:] ITU-T Y.1541 "Amendment 1: New Appendix X - An example showing how to calculate IPDV across multiple sections" addresses my question. Thank you, Jim D. _______________________________________________ VoiceOps mailing list VoiceOps at voiceops.org https://puck.nether.net/mailman/listinfo/voiceops This message and any attachments are intended only for the use of the addressee and may contain information that is privileged and confidential. If the reader of the message is not the intended recipient or an authorized representative of the intended recipient, you are hereby notified that any dissemination of this communication is strictly prohibited. If you have received this communication in error, please notify us immediately by e-mail and delete the message and any attachments from your system.
That's of course not really true, looks like you missed a lot of ITU-T docs. You got to check out the - Y.x-series - G.x-series and - P.x-series of ITU-T Recommendations. At also the work in progress of SG12: http://www.itu.int/ITU-T/workprog/wp_search.aspx?isn_sp=545&isn_sg=551&isn_s... See e.g. P.1010 : Fundamental voice transmission objectives for VoIP terminals and gateways or Drafts P.VOIP-MM Q 2/12 Measurement methodologies for P.VOIP P.IPterm Q 3/12 Transmission characteristics for VoIP terminals etc etc
-----Original Message----- From: Hiers, David [mailto:David_Hiers at adp.com] Sent: Montag, 1. November 2010 21:54 To: Jim.Dalton at transnexus.com; Schwarz, Albrecht (Albrecht); voiceops at voiceops.org Subject: RE: [VoiceOps] Question about Packet Jitter
Before you get down into the weeds with the math...
All the ITU docs that I've read portray the "network" as set of "non-rtp-aware, forward-as-fast-as-you-can router-type-things that probably have some qos capability". The "edge" is implicitly defined as the first occurrence of a jitter buffer.
As near as I can tell, there are no rtp jitter buffers in an ITU "network" for which all this fancy math applies. If you transcode, scrub media with a ditech pvp, or otherwise implement anything that knows it should generate an rtp stream by sending a packet every X milliseconds, the ITU math is bounded by that device.
If the SBC in your example transcodes or has a jitter/loss-concealment buffer, it *is* the edge, and you cannot average the link jitters as described in the ITU docs.
David Hiers
CCIE (R/S, V), CISSP ADP Dealer Services 2525 SW 1st Ave. Suite 300W Portland, OR 97201 o: 503-205-4467 f: 503-402-3277
-----Original Message----- From: voiceops-bounces at voiceops.org [mailto:voiceops-bounces at voiceops.org] On Behalf Of Jim Dalton Sent: Friday, October 29, 2010 6:43 AM To: 'Schwarz, Albrecht (Albrecht)'; voiceops at voiceops.org Subject: Re: [VoiceOps] Question about Packet Jitter
VoIP performance experts should be familiar with
- ITU-T Y.1541 concerning IPDV (IP packet delay variation = jitter); there are many sections on IPDV, particularily also on "aggregated PDV";
[JD wrote:] ITU-T Y.1541 "Amendment 1: New Appendix X - An example showing how to calculate IPDV across multiple sections" addresses my question.
Thank you,
Jim D.
_______________________________________________ VoiceOps mailing list VoiceOps at voiceops.org https://puck.nether.net/mailman/listinfo/voiceops
This message and any attachments are intended only for the use of the addressee and may contain information that is privileged and confidential. If the reader of the message is not the intended recipient or an authorized representative of the intended recipient, you are hereby notified that any dissemination of this communication is strictly prohibited. If you have received this communication in error, please notify us immediately by e-mail and delete the message and any attachments from your system.
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albrecht.schwarz＠alcatel-lucent.com -
David_Hiers＠adp.com