TELECOM Digest OnLine - Sorted: Re: STP Vendors

Re: STP Vendors

Thor Lancelot Simon (tls@panix.com)
Wed, 11 May 2005 00:28:30 UTC

In article <telecom24.207.9@telecom-digest.org>, John McHarry
<jmcharry@comcast.net> wrote:

> Does anyone know why the US went with STPs instead of F links? Last I

You've got the question backwards; the network architecture originated
in the US, and was adapted by the Europeans to more nearly approximate
their hop-by-hop analog interoffice signaling.

F links are, in essence, wasteful; generally they lead to a
significant surplus of signaling bandwidth at some points in the
network and periodic deficits elsewhere. It is also somewhat easier
to engineer a heavily redundant signaling architecture -- particularly
in the tree-structured EO and tandem voice network US carriers
inherited from Bell -- if you physically separate packet switching for
the signaling links from the actual presence of voice trunk groups
between switches.

Finally, it's noteworthy that other network protocol suites (e.g. IP,
XNS, SNA) generally distinguish between the routing and end-host
functions; certainly most stacks can do both, but a really high
performance router, for most protocols, doesn't make a great end host,
and vice versa. Why expect it to be different for SS7? You don't
_need_ all the baggage of a voice switch along for the ride if your
intent is to just forward signal units, and dispensing with it means
reduced cost and size, which means you can have more message routers
and more links on those routers, which means you can have a more
redundant network.

Thor Lancelot Simon tls@rek.tjls.com

"The inconsistency is startling, though admittedly, if consistency is
to be abandoned or transcended, there is no problem." - Noam Chomsky

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