Subject: Re: [codec] proposed charter

From: Gregory Maxwell <[email-masked]>
Date: Tue, 10 Nov 2009 07:07:16 -0800

Behalf Of Henry Sinnreich [[email-masked]] wrote:
> Also the reference to packet loss in the Internet opens a can of worms, since broadband
> networks don’t really suffer from sizable random packet loss, but may suffer from packet
> burst loss (such as producing voice clipping) due to congestion or route flapping for which
> no codec can expected to be tolerant or immune.

The public internet very much suffers from random packet loss.

Best practices queue management has people using random-early-discard, and as far as I can
tell no one of significance is placing VoIP traffic transiting from other people's networks into a
special high priority queue, so even when there is no significant congestion.   This isn't a high
level of loss, but it is a constant reality so we ought to expect it to be well handled, and handling
it well is very much a property of the codec.

Congestion and broken links are also a reality, especially when you consider internetworks. 
Anecdotally— Wednesday, Thursday, and Friday of last week I was seeing a random loss of
4-6% between my home and my office (which are less than two miles apart, but three providers
apart). Today, and most of the rest of the time it is fine.

Although not an issue for me,  many end users have significant bandwidth bottlenecks at the
first hop out of their local network.  If you have a 128Kbit/sec upstream cap then any kind of
file upload is going to cause loss— absent some QoS configuration which still does not generally
exist even though it has been justified for years.   

Burst losses, as you say, are much harder to do anything useful with... and are often more an
exercise in jitter buffer performance than codec performance. 
 
I have a pair of small computers with GPS disciplined oscillators and some software I wrote that
sends out nanosecond timestamped and sequenced numbered packets.  If people can suggest
types of network paths they'd like to see data more solid than anecdotes, I'd be glad to send it
out and collect traces.