Over For Efficiency
are hardware devices that look similar to routers, hubs,
and bridges. However, three important factors separate
switches from their networking cousins:
overall speed (switches are much faster);
forwarding methodology or electronic logic (smarter);
and higher port counts
your network grows in terms of nodes, users, and services
provided, sooner or later you'll be faced
with the monster of all network problems: insufficient
will degrade, users will cry about slow network response
times, and client/server applications will grind to
a halt. This is not good for your network. You've got
two options at this point--work for a company that doesn't
care how much money you spend and can afford long spans
of network downtime, or adopt switching.
are smarter than hubs and offer more dedicated bandwidth
to users or groups of users. A switch forwards data
packets only to the appropriate port for the intended
recipient, based on information in each packet header.
To insulate the transmission from the other ports, the
switch establishes a temporary connection between the
source and destination, and then terminates the connection
when the conversation is done.
Do Switches Work?
In simple terms, switches function by breaking down
greater, traffic-intensive networks into smaller, more
controllable sub-networks. Instead of each device constantly
vying for attention on a single saturated segment of
10Mbps Ethernet, switches allow single devices (or groups
of devices) to "own" their own dedicated 10Mbps
segments connected directly to the high-speed switch,
which then facilitates inter-segment communication.
this sounds a lot like a bridge, there are some important
distinctions that make switches much more dynamic and
useful pieces of hardware.
bridges, switches subdivide larger networks and prevent
the unnecessary flow of network traffic from one segment
to another, or in the case of cross-segment traffic,
switches direct the frames only across the segments
containing the source and destination hosts.
Different Are Switches?
Switches themselves are hardware devices that look similar
to routers, hubs, and bridges. However, three important
factors separate switches from their networking cousins:
overall speed (switches are much faster); forwarding
methodology or electronic logic (smarter); and higher
port counts. In contrast to the functionality of bridges
and routers, which traditionally utilize the less effective
and more expensive microprocessor and software methods,
switches direct data frames across the various segments
in a faster and more efficient manner through an extensive
reliance upon on-board logic, through Application-Specific
Integrated Circuits (ASICs).
By now you should be convinced of the important role
that switches could play as part of your Ethernet network.
Let us take a look at the various kinds of switches
that are available.
Dynamic switches not only forward packets to their proper
destination, but also maintain a table that associates
individual nodes with the specific ports to which they
are connected. This information, updated each time,
a particular machine transmits across the network, allows
the switch to quickly direct frames across proper segments,
rather than across all segments on the switch.
Segment switches can handle the traffic from an entire
network segment on each port, allowing you to connect
a higher number of workstations or segments with fewer
switches/physical ports. The great aspect of segment
switches is that they are also capable of handling a
single workstation on each port (in essence, a segment
with one node). Because of the inevitable cost controls
that you encounter on a daily basis, segment switching
is the preferred and most readily implemented solution
because it requires little in the way of additional
expenditures for hardware, additional cabling, and so
Port switches are designed to accommodate a single device
on each physical port. However, implementing a port-switching
solution demands a good deal of capital for additional
wiring (cable runs are needed from each device directly
to the switch) and enough switches to provide the requisite
number of physical ports. Additionally, as your network
grows, you'll face significantly increased expansion
costs because you'll need new cable runs and possibly
entirely new switches every few months. If you've got
lots of cash, this is a great option; you'll have quite
an impressive network.
Cut-through switches help speed network communication
by forwarding packets much sooner than traditional switches
will allow. This is achieved by forwarding packets to
their destination machine prior to receiving them in
their entirety, sending them on as soon as the switch
is able to determine the destination address. Unfortunately,
if yours is an extraordinarily busy network, the benefits
of cut-through switching will be less noticeable, and
will reach their limits much sooner than in a less intensive
And Forward Switches
Store-and-forward switches take an entirely different
approach. Instead of the faster send-it-as-soon-as-you-can
rule used by cut-through devices, store-and-forward
devices wait until the entire packet is received by
the switch, only then sending it on to its destination.
this doesn't strictly increase network performance,
it does eliminate the additional transmissions that
must occur as a result of packet errors that otherwise
would have occupied network resources, thus providing
an associated speed increase.
including switches as part of your greater network,
you'll gain a wide variety of benefits, including decreased
latency, faster file transfers, fewer collisions and
other transmission errors, and significantly easier
management of the greater network.
inexpensive compared to other options such as fast
Ethernet or FDDI.
be implemented in a proportionately shorter period
regain lost bandwidth and allows for full duplex
Rathod can be reached at firstname.lastname@example.org