I have been doing some reading on audio over IP (or networking of any
kind) and one of the things that comes up from time to time is collisions.
Anything I read about ethernet talks about collisions and how to deal with
them. When I was thinking of a point to point layer two setup, my first
thought was there should be no collisions. Having read all the AES67 and
other layer 3 protocols there does not seem to be mention of collisions
really. My thought is that on a modern wired network there should be no
collisions at all. The closest thing would be a delay at a switch while it
transmitted another packet that in a hub would have been a collision.
So my thought is that AoIP at low latencies depends on a local net with no
collision possible. Am I making sense? or am I missing something?
The various documents do talk about three kinds of switches, home,
enterprise and AVB. It is quite clear what makes an AVB switch, but what
does an "enterprise" switch have over any other switch aside from
speed? I am sure I am being small minded in my thoughts here. For example,
I am expecting very little non-audio bandwidth and I am guessing that the
average home switch does not prioritize any style of packet over another.
I guess I am asking what parts of a switcher are important for audio? I am
guessing that HW encription (offloading the SSL from the server to the
switch) is not something that helps audio. Even with proprietary
protocols, it would not make sense to use encription. There seems to be a
real plug and play emphasis where the audio enabled LAN is firewalled from
the rest of the world. The streams are multicast so any box that
recognizes the packets can use those channels and offer it's own audio
channels. Any box can send control messages to reroute audio... there must
be some kind of authentication for that.... (light bulb) this is why AES67
does not include controls and perhaps discovery either. I can just see
someone walking into a concert with a notepad and deciding they want
their own mix... I am guessing the promoter would not want people walking
away with their own "direct from the mixer" audio track of the event
either. Not quite plug and play then. The wireless router wants to limit
what traffic it deals with.
So AES67 allows the control to be offloaded to a web interface with access
control (switch SSL offloading would not help here anyway). Discovery ends
up being manual at first glance. I am thinking it will not be long before
the control and setup will automate loging into the web IF and setting
things up. A system wide user/password and an interface that defaults to
streaming it's own inputs as multicast is already discoverable.
--
Len Ovens
www.ovenwerks.net
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