[VoiceOps] Question about Packet Jitter

[anorexicpoodle]

If the SBC is holding all media, is there a reason it cannot simply
report what the jitter on the egress leg was and skip the derived jitter
equation? This is a simple enough trick for Acme, and I cannot imagine
most of the other vendors wouldn't have similar functionality. 

On Thu, 2010-10-28 at 08:34 -0400, Jim Dalton wrote:

> I have a question about calculating jitter.  Consider the call diagram
> below.
> A SIP call flows from the source device to the Session Border Controller
> (SBC)
> to the destination device.  All RTP packets are proxied through the SBC.
> 
> +========+                    +=====+                   +=============+
> | Source |  Ingress Call Leg  | SBC |  Egress Call Leg  | Destination |
> | Device |------------------->|     |------------------>|   Device    |
> +========+                    +=====+                   +=============+
>             Jitter Src to SBC
>           ------------------->
>  
>                     Jitter Source to Destination
>           --------------------------------------------->
> 
> If the packet jitter is known for the Ingress Call Leg from the source
> to SBC and for end to end packet flow from the source to the destination,
> is it possible to calculate jitter for the Egress Call Leg from the SBC
> to the destination device? 
> 
> I do not think the following relationship is accurate.
> (jitter Source to Destination) less (jitter Src to SBC) = (jitter SBC to
> Destination)
> 
> Can anyone provide some guidance on this question?
> 
> Thank you,
> 
> Jim Dalton
> VoIP Least Cost Routing, Analysis, Billing
> 1.404.526.6053
> www.TransNexus.com
> 
> 
> 
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