[Wolves] I have just recieved my N+ first course book and have a query......

[Dave Morley]

On Sun, 2008-01-27 at 11:26 +0000, Adam Sweet wrote:
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> James Dalley wrote:
> >  From: davmor2 at gmail.com
> >> To: wolves at mailman.lug.org.uk
> >> Date: Sat, 26 Jan 2008 21:33:33 +0000
> >> Subject: [Wolves] I have just recieved my N+ first course book and
> > have a query......
> >>
> >> In the text it says a bus topology follows the 5-4-3 rule.
> >> 5 network segments (what the hell is a segment? Is it just as simple
> >> as 5 section where computers can be added)
> >> 4 repeaters (these I understand improve the signal strength)
> >> 3 of the 5 segments can have nodes. (why?)
> >>
> >> Help please it's thrown me and I know that your explainations will make
> >> more sense than the course providers :)
> >> --
> >> Seek That Thy Might Know
> > 
> > 
> >       5-4-3 Rule
> > 
> > A consideration in setting up a tree topology using Ethernet protocol is
> > the 5-4-3 rule. One aspect of the Ethernet protocol requires that a
> > signal sent out on the network cable reach every part of the network
> > within a specified length of time. Each concentrator or repeater that a
> > signal goes through adds a small amount of time. This leads to the rule
> > that between any two nodes on the network there can only be a maximum of
> > 5 segments, connected through 4 repeaters/concentrators. In addition,
> > only 3 of the segments may be populated (trunk) segments if they are
> > made of coaxial cable. A populated segment is one which has one or more
> > nodes attached to it . In Figure 4, the 5-4-3 rule is adhered to. The
> > furthest two nodes on the network have 4 segments and 3
> > repeaters/concentrators between them.
> > This rule does not apply to other network protocols or Ethernet networks
> > where all fiber optic cabling or a combination of a fiber backbone with
> > UTP cabling is used. If there is a combination of fiber optic backbone
> > and UTP cabling, the rule is simply translated to 7-6-5 rule.
> > 
> > 
> > http://www.teach-ict.com/as_a2/topics/networks/pages/chap5.htm
> 
> It is specific to non-switched networks, ie those using hubs and
> repeaters. A hub is a multi-port repeater which sends all traffic
> received out of every port except the one it was received on.
> 
> Networks using switches don't have to adhere to this rule. On a hub or
> repeater, all devices contend for media access (ie to be able to
> transmit) and have to back off for a random period if they transmit at
> the same time (collide) before trying again. This makes transmission on
> networks using hubs and 10BASE-T (10Mb) networks very slow compared to
> switched 100BASE-TX (let alone 1Gb) networks.
> 
> (The number at the front in the name of an Ethernet standard is the
> speed, usually in Mb unless it has a G after it. The characters at the
> end denote the cabling type.)
> 
> 100BASE-TX (100Mb ethenet over CAT-5, CAT-5e or CAT-6 cable), is not
> only capable of 100Mb transmission at any one time, it is also able to
> transmit and receive at the same time (full-duplex), which makes 200Mb/s
> overall when a machine is sending and receiving data at optimum
> performance. At this stage, only 4 of the 8 wires in the cable are being
> used, 1Gb ethernet uses them all.
> 
> If anyone is using hubs or 10-BASE-T equipment out there, replace it
> immediately if performance is even remotely important.
> 
> Regards,
> 
> Adam Sweet
> 
> - --
> 
> http://blog.adamsweet.org/
> 
Thanks Guys it's just the books description was kinda naff :)
-- 
Seek That Thy Might Know
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