Switched Networks

Switched Networks

Networks are getting more and more popular,
and because of this more people use them, which slows them down.

Networks in the future will need to have enough bandwidth to support applications,
like multimedia, witch require larger bandwidth. Switching will change
the way networks are designed. These changes will maximize productivity.

Switching technology is increasing
the efficiency and speed of networks. This technology is making current
systems more powerful. Many networks are experiencing bandwidth shortages.

There are several reasons for this including: an increase in traffic, because
networks have so many users, Amount of data between client/server applications,
and the inefficient traffic patterns of most networks.

Switching directs network traffic
in a very efficient manner. It sends information directly from the
port of origin directly to its destination port. Switching increases
network performance, enhances flexibility and eases moves, add-ons and
changes. One of the benefits of switching is that it maintains a
direct line of communication between two ports, and maintains multiple
simultaneous links between various ports. It reduces network traffic
by reducing media sharing.

This technology has some benefits over
ethernet routed networks. First, a 10 Mbps or 100 Mbps shared media can
be changed to 10 Mbps or 100 Mbps of dedicated bandwidth. Routers have
many devices attached to their ports, sharing the bandwidth. Switches let
you to connect either a shared segment of bandwidth (workgroup) or a dedicated
one (server) to each port. Second, this can be done without changing any
software or hardware already on the workstations Finally, a switch installation
is less complex than a bridge/router configuration.

A ethernet LAN runs at 10 Mbps. Stations
attach through a hub or repeater. Every station can receive transmissions
from all of the stations, but only in a half-duplex. This means that stations
cannot send and receive data simultaneously. In a ethernet network only
one packet can transmit at one time, this is what slows down networks.

The bridge, the router and the switch, all attempt to reduce transmission
time to increase performance.

A two-port bridge splits a network into
two physical segments and only lets a transmission cross if its destination
is on the other side. It also will only move a packet to the other side
if it is necessary. This reduces network traffic because traffic
on one side stays local.

Routers link multiple networks together.

It maintains the flow of traffic and routes data to the network that it
must go to. (Each port has a unique network number.) it also has a "firewall"
function. Bridges and routers have similar bus architectures. Switches
eliminate the bus architecture.

Ethernet switches segment a LAN into many
dedicated lines. A switch port may be configured in segments with many
stations hooked to it or with a single station hooked to it. The rule is
that only one conversation may originate from any port at a time, it doesnít
matter if there is one or a lot of stations connected to that port. All
ports have to listen before they transmit. When a single LAN station is
connected to a switched port it is in full-duplex mode. This helps
because there are no collisions of packets since they are all separate
ports. Full-duplex switching means traffic can be sent and received at
the same time. Ethernet networks go from 100 Mbps to 200 Mbps. (hubs between
a workgroup and a switch will not run full-duplex, the workgroup is unswitched
ethernet.). Switches are starting to be more popular than routers
and bridges. Switches now do the segmentation once done by routers and
bridges. Switches can do more than put a packet to one side or the other
- they send traffic right to its destination.

RISC (Reduced Instruction Set Computer)
is a type of CPU to process in switches. It is used for general,
or simple task, RISC switches are not as well at performing specific tasks.

One of the advantages of RISC is that it
is inexpensive compared to one with customized CPU. RISCs are already somewhat
common in businesses and are off-the-shelf processors. This type
of switch can perform some functions similar to a router. The downside
of this type of RISC is that it is a store-and-forward processor that is
not as fast as an ASIC switch.

ASIC (Application Specific Integrated

Circuit) This is the other design widely used in switches to process. They
are custom designed to handle specific operations, all of the functions
are in hardware. If any changes are needed, manufacturing must be done
to rework hardware. No software upgrades are available.

Another type of network architecture that
is benefiting from switching is, token ring. One of the advantages
is Ė faster and larger networks. Since switches do all of