Path: utzoo!attcan!uunet!know!zaphod.mps.ohio-state.edu!usc!elroy.jpl.nasa.gov!decwrl!sgi!vjs@rhyolite.wpd.sgi.com
From: vjs@rhyolite.wpd.sgi.com (Vernon Schryver)
Newsgroups: comp.dcom.lans
Subject: Re: How many physical addresses belong to 1 Ethernet station?
Summary: IGMP is coming
Message-ID: <72777@sgi.sgi.com>
Date: 20 Oct 90 18:46:26 GMT
References: <1990Oct18.172918.24929@forwiss.uni-passau.de> <2988@jaytee.East.Sun.COM>
Sender: guest@sgi.sgi.com
Organization: Silicon Graphics, Inc., Mountain View, CA
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In article <2988@jaytee.East.Sun.COM>, ckollars@deitrick.East.Sun.COM (Chuck Kollars - DSGG Technical Marketing - Boston) writes:
> ...
> To date the multicast capability is not used very much.  Many ethernet 
> hardware vendors use one multicast address to exchange "private" management
> information.  You may see more use of Ethernet multicast addresses in
>the future:...


IGMP (see, for example, RFC-1112) involves a mapping from Class D network
numbers to Ethernet and FDDI multicast addresses.  IGMP is coming.  At
least one host vendor is currently shipping it.  I've been told that IGMP
will arrive in force on the Internet with OSPF.

Multicast makes for good network games, and there is already one game with
an assigned number.  It would have been a better way to do network
databases like YP/NIS.  I think one network name service compeating with
YP/NIS and the Internet DNS is using multicast.   There is at least one
protocol, XTP, which uses multicast MAC addresses to implement "reliable
multicast datagrams."  There are Class D numbers assigned to rwho and
NetworkTimeProtocol.  See the current Assigned Numbers RFC.


Vernon Schryver,   vjs@sgi.com


P.S. It would have been nice if the AMD FORMAC (FDDI MAC chip) had some
    reasonable support for multicast.  Unfortunately, the only apparent way
    to make the FORMAC do multicast, "external address detection," causes
    it to generate a "non-maskable interrupt" on each multicast or
    broadcast frame received.  That is compared to the nice multicast
    filter on the AMD ethernet LANCE.