Re: [Etherboot-developers] [RFC] Multicast reception....

[<ebi...@ln...>]

Peter Lister <P.L...@sy...> writes:

> > > Please see RFC2090 (tftp multicast). It offers you quite a lot of what you
> > > need. Can be downloaded from http://www.faqs.org/rfcs/rfc2090.html
> > 
> > It's a good RFC, but it has several problems.  
> > 
> >  - It doesn't fix TFTP's streaming problem.  That is the server has
> >    challenges to keep the network busy.
> > 
> >  - It requires all clients to be registered.  My design goal is 10,000
> >    clients.  If something goes wrong 10,000 timeouts can be a real problem.
> > 
> >  - It doesn't handle large files.  (A requirement for using multicast
> >    transfers for other purposes). 
> > 
> > I already have a tested protocol that is a little simpler on the
> > server end but it about equivalent on the client end.
> 
> Eric, can I encourage you to accommodate RFC 2090, or at least make it
> easy for others to do so. I understand your design goals, but supporting
> RFCs where they exist seems like a good idea.

I don't expect my protocol to be the end all be all, but simply something
good enough to use to today, and something that is good enough the
practical difficulties can be explored.

The IGMP code, and the multicast support I am coding should be reuseable
just like the existing udp stack.

> Also, have you looked at http://vaccine.sourceforge.net ?

I just looked.  The code was never completed, and the paper is
wishy washy. 

Multicast data transfer is simple.  There is not a black art to
getting something that works.  Handling the retransmit scenario is
a challenge but getting the common case right is simple.  

The paper "A reliable multicast framework for Light-weigth sessions
and application level framing" is hightly academic and comes to few 
specific conclusions, and is targeted at conferencing type
applications. 

For network booting, and even host installation the primary target
are local networks, doing file transfers.  This allows for a lot
of simplifications, from the what is needed for real-time conferencing
software.  In particular you can transfer the entire file without even
thinking about retransmissions.

Eric