Intergrating Fast
Ethernet into 10MB Ethernet Networks
Introduction
Now that
Fast Ethernet is here, the question becomes, "How do I
start using it ?" Integrating Fast Ethernet into
existing networks need not be done all at once.
Here are
some aspects of 100Mbps implementation that should be
considered:
-
Expand The Topology Outwards
and Downwards
Implementing Switching
Implement
switching in high-traffic areas to concentrate the
bottlenecks on the network. Since Fast Ethernet provides
higher throughput of bits, it makes sense to figure out
which network connections need the most relief. Which
segments consistently attempt to pump the most bytes?
Which segments consistently demonstrate the highest
average percent bandwidth usage according to your
protocol analyzer?
Installing
switches will help you figure out which network segments
are moving the most information due to the effect
switches have on your network. Installing switches is
like moving from traffic lights to limited-access
highways. The idea works extremely well in isolating
cross-town traffic, e.g. peer-to-peer networking, but
doesn't necessarily help when all of the traffic slows
down at particular locations, e.g. an enterprise-wide
server or the network Internet firewall. Because there
are other ways of isolating network bottlenecks,
implementing switches is primarily useful when
installing 10/100 switches in preparation for 100Mbps
Ethernet.
Installing
switches also gives the added benefit of segmenting
collision domains. In classic Ethernet, there can be up
to four hubs or repeaters between any two stations, but
in Fast Ethernet that number is only one or two.
Installing switches in place of repeaters spares you
having to segment your network at a later point,
allowing the cost of the transition to be spread over a
longer period of time.
Eliminating Bottlenecks
Once
bottlenecks have been identified, upgrade those network
connections to 100 Mbps. The primary difficulty in this
step is verifying that the existing cabling will be
sufficient for Fast Ethernet. On UTP, the cable either
needs to meet Category 5 specifications or have four
pairs with proper twist maintained on Category 3. If
you're planning on using 100BASE-TX, your wiring closet
will also need to be certified for a higher speed. There
are many devices available such as wire pair scanners,
which will make this job much easier.
Installing
the initial Fast Ethernet connections is much easier if
the switches installed earlier are 10/100, capable of
operating at either classic Ethernet speeds or Fast
Ethernet speeds. If the switches installed were only
10Mbps switches, they could be used as "hand-me-downs,"
replacing hubs in segments where users require more
bandwidth.
Expand The Topology Outwards and Downwards
Gradually
work the Fast Ethernet out into the rest of the network,
as far out and down as desired. Note that the price of
10/100 cards is not substantially higher than that of
10Mbps cards, so it may be a wise idea to plan ahead by
installing 10/100 cards when installing new machines.
If there
comes a point in the future when 100Mbps Ethernet needs
to be implemented on that machine, all that will need to
be changed is the connection on the other end. On the
other hand, upgrading a machine from a 10Mbps card to a
100Mbps card will require reconfiguring the user's
machine, installing a new driver, etc. A short-term
expenditure can greatly offset the cost in man-hours and
down-time later on. |
