On Thu, Sep 11, 2014 at 10:29:24PM +0100, gordonjcp(a)gjcp.net wrote:
On Thu, Sep 11, 2014 at 09:17:26PM +0000, Fons
Adriaensen wrote:
Re. the format used by njbridge: for IPv4 the IP
and UDP
headers together take 28 bytes. That is less than 2 percent
of 1500, and is a small price for having packets that can be
handled by switches and routers. There is really no point in
trying to reduce that sort of overhead. The njbridge format
itself adds a 20 byte header to sample packets. This data is
used to identify the packet, to improve the timing and handle
skipped cycles, xruns, lost packets and the like. All together
the overhead is less than 3.5%.
But then you *must* take care of timing, since you have no ideai
if packets passed through a router will arrive in order, how long
they'll take to traverse it, or even if they'll arrive unmangled
at all.
The format used by njbridge takes can handle all of that. The current
receiver (n2j) discards packets that arrive out of order (they will
have been replaced by silence before they arrive) but it would be
possible to re-insert them. But being able to do that implies more
latency - a packet can't arrive out of order without being late as
well.
If you are going to strip it down, just go with bare
Ethernet frames :-)
What I wanted to make clear is that there is really no point
in doing that.
Ciao,
--
FA
A world of exhaustive, reliable metadata would be an utopia.
It's also a pipe-dream, founded on self-delusion, nerd hubris
and hysterically inflated market opportunities. (Cory Doctorow)