Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!apple!netcom!jbreeden
From: jbreeden@netcom.COM (John Breeden)
Newsgroups: comp.dcom.lans
Subject: Re: 10Base-T hubs
Message-ID: <1991Apr3.164611.4088@netcom.COM>
Date: 3 Apr 91 16:46:11 GMT
References: <1991Apr03.004515.12021@rs6000.cmp.ilstu.edu>
Distribution: usa
Organization: Netcom - Somewhere in the S.F. Bay Area
Lines: 59

In article <1991Apr03.004515.12021@rs6000.cmp.ilstu.edu> ejbehr@rs6000.cmp.ilstu.edu (Eric Behr) writes:
>We're considering using our twisted pair wires for Ethernet. Hence tons of
>questions, some of which are below:
>
>- aside from distance/no. of stations differences, is UTP inherenly less
>reliable than thin/thick E-net?
>

No (I can hook up just as many stations using UDP as thin/thicknet).

>- in a smallish network (30 nodes, less that 300 ft.) is a passive hub OK?
>Price difference between active and passive hubs is substantial...
>

If you are using a "passive" hub, it's not 10baseT. The standard calls for
hubs that are active repeaters. If you decide to use "passive" hubs, you'll
save money but a) you're not 10baseT and b) you're not "reliable".

One of the things that makes 10baseT reliable is the active nature of the 
hubs (ie: multiport repeater function - packet re-generation).

>
>- is there any advantage to "cascading" hubs (attaching the next one to a
>port in the previous one - you lose two ports) as opposed to putting both
>directly on a thin/thick backbone and using all ports for the UTP star?
>

No, you can attach hubs off of coax, chain hub to hub or star hubs off of
a single hub or any combination.

>- (must be obvious...) does 10Base-T *have* to use star topology?
>If so, then (troubleshooting aspects set aside) I save maybe $500 in
>thinwire cabling costs but I lose $1000+ on a hub... I think that
>10Base-T's economic advantages are a bit overblown given the current
>prices; am I right?
>

Yes, 10baseT must be in a star configuration (it's in the standard). There
is nothing that stops you from using a bus configuration (other than 
mechanical, you need to flip wire pairs to make it work). You loose the
"reliability" of 10baseT without the hubs (packet regeneration, port jamming
on bad packets, station isolation, "added-value vendor" hub management etc).

10baseT's economic advantage is'nt in the installation (that rumor got started
with the "cost savings" of using existing phone wiring, which considering the
type and condition of the wire installed may not be the case.

The "cost savings" is the ease of trouble reporting, isolation and management 
due to the a) star configuration and b) management and fault isolation 
inherent in the hubs.

If you are looking for "cheap" - use thinnet.
-- 
 John Robert Breeden, 
    jbreeden@netcom.com, apple!netcom!jbreeden, ATTMAIL:!jbreeden
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 "The nice thing about standards is that you have so many to choose 
  from. If you don't like any of them, you just wait for next year's 
  model."