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[ih] invention of multicast addressing

Hi Craig,

>From some IBM-land document I found:

Address---Contains the SDLC address of the secondary station, which
indicates whether the frame comes from the primary or secondary. This
address can contain a specific address, a group address, or a broadcast
address. A primary is either a communication source or a destination,
which eliminates the need to include the address of the primary.

IIRC, IBM's SDLC was developed in the early/mid 70s.  Depending on
whether or not you think an SDLC "group address" fits the concept of
"multicast address", SDLC might be when the concept came about.  There
were other computer communications architectures at the time which
supported similar multiple-destination addressing, so IBM SDLC may not
have been the first.  Multi-point and multi-drop architectures were in
common use at the time because leased lines were so expensive.

I think you may find that a lot of architectural concepts like multicast
addressing have roots in the earlier vendor-proprietary computer
communications technologies, which have now mostly been steamrollered
into oblivion by The Internet.  It's very hard to tell which of all that
technology influenced the later work.


On Fri, 2010-05-07 at 13:20 -0400, Craig Partridge wrote:
> Hi folks:
> I'm trying to nail down when the concept of a "multicast address" came about
> (just a little citation in a larger paper I'm writing).
> In 1976 in the original Ethernet paper, there was unicast and broadcast.
> In 1978, in their survey of local networks, Clark, Pogran and Reed mention
> in passing that Mockapetris is playing around with bit wildcarding that
> permits multiple addressees using one address.
> In the 1980 Ethernet specification there are Ethernet multicast addresses as we 
> know them today.
> Digging a bit deeper from references in later papers, it appears that
> Mockapetris, Lyle and Farber may have proposed a form of multicasting in 1977
> (IFIP Congress paper of August 1977 that I don't have).
> That suggests that someone saw the Mockapetris-Lyle-Farber idea, simplified it
> and put it into the 1980 Ethernet standard (where it sat unused for several
> years...).  But I can find no trail... Anyone got insights?
> Thanks!
> Craig