At 04:04 PM 4/15/01, you wrote:
>Priscilla,
>
>With reference to the comment below:
>
>The cram
> > session has the usual misconceptions, such as claiming that SRB and SRT
are
> > in 802.5, which they aren't, and that HSRP is a routing protocol that is
> > standing by, (it's a router standing by), and AppleTalk is "chatty."
> >
>I have two questions:
>
>1) Has the SRB definition only recently moved to IEEE 802.1d?
SRB is documented in IBM's Token Ring Architecture Reference Manual. It's
not in an IEEE document. When IBM brought the SRB specs to the IEEE, the
IEEE said that SRB must fit with existing bridging standards, and IBM and
IEEE jointly developed SRT and added it to 802.1D in the early 1990s.
One area of confusion is that SRT was designed mostly by people on the
802.5 committee, including IBM engineers. Some preliminary documents said
802.5 on them. But the intent was that it be part of 802.1D right from the
beginning. (I was on the 802.5 committee for a short time in the early
1990s and that's the impression I got anyway.) It's a picky thing, but I
like to point it out in case someone actually wants to ready the
specifications.
> I do not
>have the very latest versions of both IEEE 802.5 and 802.1d but keep
>thinking (probably wrongly) that SRB is included in the former one. At
>least in previous published version I have got. I know the SRT is 802.1d
>but cannot find any indication in the standards and status reports on
>IEEE concerning SRB.
>
>2) I also though the AppleTalk is quite chatty. Chooser is given as a
>usual example for that. Or is it only when the Chooser window is left
>open unnecessarily?
Apple fixed the excessive traffic caused by leaving the Chooser open in
1989. (System 7). It was only a lot of traffic if the user had also
highlighted an object type (printer, server) and zone name. It was never
really a serious problem. Usually the user didn't have those highlighted.
There are a couple legitimate reasons to call AppleTalk "chatty." The
10-second timer for RTMP is awfully small. But the advantage to a small
timer is quick convergence. Also, end stations learn very quickly who their
new router is. There's no need for HSRP. The other case where AppleTalk is
chatty is the AppleTalk Transaction Protocol (ATP) sends keepalives to the
other side every 10 seconds.
But, AppleTalk does not advertise zones. (If you see that common
misconception in a book, throw it out. ;-) The request to learn the zones
associated with a network is a unicast frame. AppleTalk does not broadcast.
It multicasts. A well-behaved NIC in a PC should not bother the PC CPU with
AppleTalk multicasts.
I bristle when I see documents that are clearly oversimplified making the
statement that AppleTalk is chatty. If you're just going to say a few
things about AppleTalk, you could mention the good things: easy
configuration, dynamic addressing, easy resource location, etc.
Priscilla
>Rita
________________________
Priscilla Oppenheimer
http://www.priscilla.com
Message Posted at:
http://www.groupstudy.com/form/read.php?f=7&i=735&t=662
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