bobkil@ibmpcug.UUCP (Bob Kilgore) (08/04/89)
HELLO TO ALL:
I have had for the past few weeks a one way, or 'read only'
connection to this group. The transmit problems are now
sorted out and I can respond to some of the things I have
been reading.
First with regard to the interesting discussion on bridges,
A number of vendors were mentioned and there products
described. One that seems to have been left in the 'bit
bucket' is SPIDER. They manufacture and sell a full line of
remote bridges. They are well packaged and seem to work
without any intervention, however they have a full set of
management tools that are accessible via a connector on the
bridge. The remote bridge can be controlled via connection
to the local bridge, or 'half bridge' if you are a purist.
Spider Systems U.S.
12 New England Executive Park,
Burlington, MA 01803
(617)-270-3510
The discussion has raised an interesting point that I have
been considering for some time. What exactly is a 'BRIDGE',
a 'ROUTER', and a 'GATEWAY'. It seems to me that there were
definite descriptions for each of these functions. I don't
think the description left room for a 'remote bridge'.
These terms are now in general use and I am not certain we
all know exactly what they are intended to describe.
I would like to here from anyone that has some thoughts on
this subject. My feeling is that if we continue to let the
'marketing department' define the terms for us, none of us
will be able to understand what it is we are supposedly
talking about. Continue the mystic of data communications.
Best Regards to all
bob
bobkil@ibmpcug.co.uk
!uunet!ibmpcug.co.uk!bobkil
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--
Automatic Disclaimer:
The views expressed above are those of the author alone and may not
represent the views of the IBM PC User Group.darcy@tci.UUCP (Jeff d'Arcy) (08/05/89)
bobkil@ibmpcug.UUCP (Bob Kilgore) writes: >The discussion has raised an interesting point that I have >been considering for some time. What exactly is a 'BRIDGE', >a 'ROUTER', and a 'GATEWAY'. It seems to me that there were My understanding: A bridge is a link level device that joins two separate media of similar *or* different types to provide the appearance of a single uninterrupted medium. Thus, there may be Ethernet bridges, Ethernet-Token Ring bridges, etc. A router is an network level device that provides communication between nodes that are not directly connected but use the same network-level protocol (IP, DECnet, etc). Gateways are not, in my experience, as clearly defined as the other two items. IMHO, "gateway" refers to a session or higher level device that performs translations between different protocols of the same basic service type (such as AppleShare to NFS or SMTP to VMSmail). Others use the term to refer to network or transport layer devices that perform different-protocol same-service translations (IP-DECnet would be an example if such a beast existed). Don't bother correcting me; this is just my opinion/understanding of the -- Jeff d'Arcy ...!uunet!tci!darcy (508) 443-7311 x283 TCI is not responsible for my opinions, nor I for theirs
pcf@galadriel.bt.co.uk (Pete French) (08/07/89)
From article <335@tci.UUCP>, by darcy@tci.UUCP (Jeff d'Arcy): > bobkil@ibmpcug.UUCP (Bob Kilgore) writes: >>The discussion has raised an interesting point that I have >>been considering for some time. What exactly is a 'BRIDGE', >>a 'ROUTER', and a 'GATEWAY'. It seems to me that there were > ... > > A router is an network level device that provides communication between nodes > that are not directly connected but use the same network-level protocol (IP, > DECnet, etc). > The devices that I am currently working on at BTRL are called BROUTERS (short for Bridge-Routers). These provide transparent connection between networks at the MAC level with networks that are physically remote from each other - they act in a similar manner to half-bridges except that the link between the bridges is done over a WAN of some kind. This means that instead of having just a pair of Brouters for every two networks you can have as many as you like and they will route packets to each other over the WAN (hence the routing part of the name). The discussion of Bridges/Routers over the past week has much depressed me. Theres nothing like being told how good al the opposition are to make you feel like giving up and going home :-) -Pete French. British Telecom Research Labs. (These opinions are not those of BT or its catering staff)
jmh@ns.network.com (1606) (08/07/89)
My understanding of the Differences among the three terms (Bridge, router,
gateway) as the standards community is attempting to use them is:
A Bridge is a layer 2 device,
A Router is a layer 3 device (hence protocol dependent)
A Gateway is a layer 7 device designed for one or more specific
applications.
There is some use of interconnection devices at layer 4. These devices
(aside from the irrelevant fact that the ISO environment tries to claim
that there should be no such thing) do not yet have a clear name. As they
are usually intended to convert between two protocol families, I tend to
refer to them as layer 4 routers, but even that is sloppy and misleading.
Joel M. Halpern jmh@nsco.network.com
Network Systems Corporationgoodloe@b11.ingr.com (Tony Goodloe) (08/07/89)
In article <11146@ibmpcug.UUCP>, bobkil@ibmpcug.UUCP (Bob Kilgore) writes: > I don't > think the description left room for a 'remote bridge'. I know that there are lots of "definitions" out there. I would like to hear your definition of a "bridge" the precludes "remote." I define a bridge as a device that connects multiple nets at the MAC layer. A router does so at the network layer. A gateway does so at higher layers, and a repeater does so at the physical layer. My definitions don't have any mention of the geographic extent. I know of local and remote repeaters, bridges, and routers. I have not seen any local gateways though. Just curious. tony
hedrick@geneva.rutgers.edu (Charles Hedrick) (08/08/89)
Note that the term "gateway" was used for many years in the IP literature for a device that switches datagrams at OSI level 3, i.e. what is often referred to now as a "router". Use of the term "gateway" for an application-level entity seems to be an ISO-ism. It's probably too late to convince the ISO community not to use "gateway" in a manner that conflicts with previously established IP usage. So I'm afraid that "gateway" now has to be considered ambiguous. Unless the meaning is clear from context, I recommend using "router" for the level 3 entity and some more explicit term for the level 7 entity, e.g. "application-level gateway" or "protocol-translating gateway".
swb@batcomputer.tn.cornell.edu (Scott Brim) (08/09/89)
Just to keep it interesting, what Apple calls a bridge is what we would call a router.
kwe@bu-cs.BU.EDU (kwe@bu-it.bu.edu (Kent W. England)) (08/12/89)
In article <8586@batcomputer.tn.cornell.edu> swb@tcgould.tn.cornell.edu (Scott Brim) writes: >Just to keep it interesting, what Apple calls a bridge is what we would >call a router. You are right, in "Inside AppleTalk" from APDA, Apple consistently calls an AppleTalk router a "bridge". But in the new "Inside AppleTalk" published by Addison-Wesley (a book worth getting; completely rewritten and very nice) somehow that nomenclature has mysteriously changed. It is now the "AppleTalk Internet Router". This funny excerpt from an Apple press release dated 22 May 89. It takes the form of Q&A (Apple talks to itself): Q: Is the AppleTalk Internet Router the same class of device that other vendors call bridges? (eg, the Kinetics FastPath and Hayes Interbridge) A: Yes. ... Some of these vendors refer to their product as a "bridge" rather than a router. Recent applications of both bridges and routers are elevating the need to distinguish between the two. ... ------ Of course, the only reason Kinetics ever called the FastPath a "bridge" was so as not to confuse Apple users who read the Apple literature. Only Apple was ever confused about what a bridge really is.