Newsgroups: comp.os.linux.networking
Subject: Re: Max length of a LAN?
References: <[email protected]>  <[email protected]>
Ish Rattan  writes:

> James Knott  wrote:
> > Ish Rattan wrote:
> 
> >> Hello,
> >> 
> >> Apology for asking an off topic question.
> >> 
> >> Most textbooks say that LAN can span 2500 meters and 4 repeaters
> >> are allowed. So, the max length is 2500 or 10000 meters (4 segments
> >> of 2500 each)? Info, is needed to to find round trip signal propgation
> >> time -- generally quoted as 50 microsecs. If one assumes speed of
> >> signal in copper as 2 x 10^8 m/s the result does not seem to match.
> 
> > There's more than just the cable propogation time to consider.  Each of 
> > those repeaters and NICs has a minimum amount of time to handle a packet.  
> > All those times must total less than the maximum allowed delay.  Also, when 
> > you pass through a switched hub, the 2 sides are completely independent, 
> > each with their own limits.
> 
> I agree but I am curious as what is the max length of a LAN 2.5Km or
> 10.0Km?

There is no general answer to the question that is the max lenght of a LAN.
Different LAN technologies have different limits. And differnet textbooks
can give different limitation.

As general rule 2.5 km is kept as general rule for maximum LAN length.
This length is based on LAN technologies used somethign like 15 years
ago. This 2.5 km limit seems to match Ethernet limits quite well, and
is propably used as guideline for some other LAN standards as well
(many standard are from same standardizing organization IEEE).

With the modern LAN technologies, like switched Ethernet networks,
you can easily build networks larger than 2.5 km if you want 
(just use correct technologies well). And those technologies are
really used to build LANs, campus are networks, metropolitan are networks
etc. The line between LAN and WAN is nowadays quite fuzzy...
LANs can be nowadays larger than used to be possible, and
updated traditional LAN technologues (most often Ethernet)
are used in WAN applications nowadays quite often.




-- 
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at 
http://www.epanorama.net/