[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

SLA for voice and video over IP/MPLS

On Thu, Feb 24, 2011 at 6:10 PM, Diogo Montagner
<diogo.montagner at gmail.com> wrote:
> Hello,
> I am looking for industry standard parameters to base the SLA of one
> network regarding to voice, video and data application.

One won't find many, but a common rule of thumb is most apps will be
'fine' with networks that provide 10E-6 BER or lower loss rates.

> Which are the the accepted values for jiiter, delay, latency and
> packet loss for voice, video and data in a IP/MPLS ?

This question is being framed backwards -- an engineer should ask ask
what the particular codecs can tollerate, then seek out networks which
can deliver on those needs. If the a/v equipment vendor can't tell the
customer or user what sort of network is required, I recommend
selecting a new a/v vendor. In any event, audio codecs such as ILBC,
g729, and 722 are well positioned for 'loss concealment' mechanisms in
the decoders, masking some reasonable amount of loss. This has been
exhaustively tested, and the data is readily available [0].

Video codecs that degrade gracefully are also fairly common, though
the industry focus seems to be on concealing loss for generic
real-time data, and offloading this work onto a different abstraction.
One example would be packetized 'forward error correction' schemes,
which can be configured or adapted to nearly arbitrarily 'high' loss
rates (eg. "ProMPEG" [1] and related work). If the a/v system in
question can support FEC of any sort, then this should substantially
reduce ones transport-layer loss rate concerns.


[0]: http://www.vocal.com/speech_coders/psqm_data.html
[1]: http://www.ispa-sat.ru/info/Inside%20Pro-MPEG%20FEC%20(IBC)%20.pdf