Subject: Re: bridges,switch
To: Andrew Brown <>
From: Erik E. Fair <>
List: tech-net
Date: 04/19/1999 15:57:42
Oh, dear me. Terminology definitions required:

repeater - only does signal regeneration for distance, i.e. bit level copy.
No filtering capability at all (not even collisions), since it doesn't even
store&forward. All 10base-T hubs are repeaters. An Ethernet with repeaters
in it is still subject to the Ethernet maximum cable length limits.

bridge - packet store&forward device; can retransmit for a collision.
"learning bridges" collect up station addresses on a per port basis, and do
not forward packets involved in "local conversations" to other ports. These
can be used to extend an Ethernet beyond its length limit (as can routers).

switch - same as a "learning bridge" (marketing-speak)

router - protocol dependent packet store&forward device; only forwards
packets directed to it, according to its routing tables for that protocol
(e.g. IP, AppleTalk, DECNET, XNS).

gateway - old Internet community term for "router", now more commonly used
for Application Specific translation functions (e.g. an SMTP-to-cc:Mail
"gateway"). Some Old Network Boys (and old RFCs) use the old definition.

	Erik <>