From: medici@dorm.rutgers.edu (Mark Medici)
Newsgroups: bit.listserv.novell
Subject: Re: 10Base-T/Ethernet Question
Date: 24 Jul 92 20:44:44 GMT
Organization: Rutgers Univ., New Brunswick, N.J.

Wegerbau@PSYCH.SSCNET.UCLA.EDU writes:

| 10Base-T/Ethernet & NetWare/TCP/IP Experts...Here is my question.  Below is a
| map of our proposed network.  [S] is the 3.11 server.  [A] and [B] are UNIX
| workstations, or possibly one is a PC trying to access the other machine via
| Telnet or FTP.  1, 2, 3, 4, 5, and M are 10Base-T hubs.  I'm fairly positive
| that this will exceed the hop count when running Telnet or FTP from [A] to
| [B].  Am I wrong?  Will Novell somehow handle this?  Are there other peer to
| peer programs, possibly using IPX, that would also have a problem with this
| setup (e.g. Lan Assist or other remote control programs)?

[...stuff deleted...]

|                          [S]
|                           |
|                        ---|---
|              |---------|  M  |---------|
|           ---|---      ---|---      ---|---
|           |  1  |      ---|---      |  3  |
|           ---|---      |  2  |      ---|---
|              |         -------         |
|           ---|---                   ---|---
|  [A]------|  4  |                   |  5  |--------[B]
|           -------                   -------

Neither [A] nor [B] will have any problems communicating with the
server [S].  However, [A] and [B] may not be able to communicate with
each other, as there are more than 4 repeaters between [A] and [B].
In fact, the mere presence of more than 4 repeaters in series on a
single network segment is a violation of the 802.3 Ethernet spec, and
may cause problems even if [A] and [B] have no reason to communicate
with each other.  On the other hand, since the 4 repeater rule is a
theoretical limit, you may find no problem in your particular
installation even when [A] and [B] attempt to communicate; in spite of
the fact that this definitely exceeds the Ethernet specification.
However, I would avoid planning to intentionally break this
specification; even if it works at first you may find conditions
change that will cause problems down the road.

The 4 repeater rule is not communications protocol dependant.  Rather,
it is a physical-layer restriction of 802.3 Ethernet.  You may be
confusing the router hop-count restriction of some communications
protocols for the electrical restrictions imposed by the 802.3
specification.

What you may want to consider is replacing hub M with a multi-
interface, multi-protocol router, or at least a bridge.  This is
generally a more reliable way to handle larger networks than using
hubs or concentrators (though many concentrators can now be purchased
with on-board bridges, and combination concentrator/routers are also
available). You may even be able to use your NetWare 3.11 server as
the router if your planned traffic accross the router will be low.
NW3.11 can route IPX/SPX and IP (and even AppleTalk if you have
NetWare for Mac).

I hope this clears things up for you.
-- 
_________________________________________________________________________
RUCS     | Mark A. Medici, Systems Programmer III, User Services Division
User     | Rutgers University Computing Services, New Brunswick, NJ 08903
Services | [medici@gandalf.rutgers.edu]                    [908-932-2412]
Comments: Gated by NETNEWS@AUVM.AMERICAN.EDU