[e2e] a means to an end
fred at cisco.com
Thu Nov 6 13:56:45 PST 2008
On Nov 6, 2008, at 1:29 PM, David P. Reed wrote:
> Let's say I have a message for all Republicans. I can send that
> message quite reliably, without ever knowing "where" the set of all
> Republicans is. In fact, it's a feature that I can do that. What's
> particularly nice is that in some cases, it is far *more* efficient
> to do that than to "first, find the locations of all Republicans"
> and "second, deliver the message to that set of locations".
> Maintaining a complex location set as an intermediate computed value
> seems like it would cost a lot more than just telling each
> Republican I know to pass the message to any Republicans he/she knows.
We call that "multicast". Yes, we know that the objective is to get it
to the members of the group identified by the group address.
> The original "six degrees of separation" experiment showed that
> networks can route messages without being told "where". The only
> argument is one of efficiency, and that argument only applies when
> a) nothing moves very fast, and b) the sender can be assumed to know
well, maybe. In today's network, there are a lot of things, and the do
indeed move pretty quickly. That said, if I want to send something to
some object in the network named "David P. Reed", it sure is helpful
to have some idea that the object might be associated with another
object like "reed.com", and to be able to translate that into some
notion of where "David P. Reed" might be found. The alternative is
some variation on a search algorithm like "ask everyone you know if
they have seen David P. Reed recently, and if so where they last saw
him", which has scaling difficulties.
Sure. I can dense-mode broadcast everything everywhere. I have visions
of how well that would work. My son gave me an example that might be
applicable. He is in USMC OCS, which means that if he wants to say
anything to anyone that isn't an officer candidate he has to stand at
attention and shout it. Saturday night, he and a bunch of compadres
were having dinner together and discussing OCS pick-up lines. They
theorized that they were supposed to
1) approach a table full of young ladies
2) pop to attention
"Good evening, ma'am! Candidate Baker requests information
the telephone number of the ladie in the blue dress! Thanks you
4) politely await any result that might ensue.
Now, let's imagine that all conversations happened that way - all the
It sure is more convenient to be able to include only the people you
want involved in the conversation and leave everyone else out of it.
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