Subject: Re: Doing ftp via multicast addresses. - approaches

From: [email-masked] (James E. [Jed] Donnelley)
Date: Fri, 16 Feb 1996 20:25:32 -0800

[email-masked] (Kamal Dhaliwal) writes:

> >Does anybody has experience in doing ftp using multicast
> >addresses i.e.
>
> >If you want to ftp a file to 10 sites, can you use
> >multicasting to send it to 10 different sites?

and Jon Crowcroft <[email-masked]> replies:

>no, no, no, no, no, no, no, no, no, no :-)
>
>FTP uses TCP
>TCP cannot use IP multicast -

Well, not IP multicast directly.  However, I would also like
to point out an approach that is also referenced in:

http://hill.lut.ac.uk/DS-Archive/MTP.html

Specifically, "Hopwise Reliable Multicast":

http://www.igd.fhg.de/www/www95/proceedings/papers/87/HRM.html
or better as:
http://www-atp.llnl.gov/atp/papers/HRM/HRM.html
(where the figure gif is functioning)

wherein an approach is discussed that uses TCP on
a hopwise basis to achieve multicast transport.
In the absence of realtime constraints I find this
approach compelling, but I don't believe it has ever
been pursued in any form.  I also believe (but without
any justification) that it would require only a fairly
minor extension to mrouted to get a prototype going (a
simple matter of programming :-).  I should note as Jon
indicated that this approach is not suitable for use over
routed IP multicast (though I believe there is no significant
loss of performance when used with "mrouters" over IP
unicast).

--Jed   http://www-atp.llnl.gov/atp/jed-signature.html