| ATM Switches |
What are switches and what does ATM stand
for? |
 What is a switch? In a network, a
device is required to connect computers together to allow them to talk to
each other. In small networks, a device called a Hub can be used (3Com hub
right). This is a simple piece of equipment which connects all devices
together so that all the computers can see each other all of the time. In
small networks this works well, but as the network gets bigger and more
data is passed through it, data collisions occur because two computers try
to talk at the same time. This is normal behaviour, and if it occurs, the
computers will wait a short time and try again. A good analagy is a party
where if everyone talks together it gets increasingly more difficult to
hear what is being said. A Switch only allows one computer to talk at a
time. Because this reduces collisions and the re-tries, more data can be
passed through a switch than a hub. An analogy of this is where people use
a telephone to talk to each other. Many simeultanous conversations can be
carried on, but each one is separate from the others.
Two sorts of
switch are used in the ERC Network, they are the Ethernet switches used to
link individual pc's together, and ATM ones used on the Wide Area Network
(WAN).
|
| What does ATM stand for? ATM is an acronym for Asysnchronous
Transfer Mode. ATM was designed to be able to carry Voice, Video and Data
together without any of the limitations of alternative technologies. In
addition it allows data traffic for different user networks to be carried
over the same physical network securely. |
 At Media Hub and The Xchange, there
is a large IBM modular switch type 8265. This has slots for modules to fit
into. Each module is for a different type of connection. Several modules
are for the 2MB/s connections to sites, and the rest are used for server
connections at 155MB/s. The 2MB/s connections at The Xchange are connected
to Leased
Lines from Telewest. The 155MB/s server and links between switches are
carried on multimode fibre optic cable. Each server has an ATM network
card in it, click here
to see a picture of one.
At the ERC site end there is an FVC ATM switch used to connect the site to
the Wide Area Network and an IBM Ethernet switch for plugging the
computers into. For more information about the equipment used at each
site, please click here.
|
At Media Hub and The Xchange, there
is a large IBM modular switch type 8265. This has slots for modules to fit
into. Each module is for a different type of connection. Several modules
are for the 2MB/s connections to sites, and the rest are used for server
connections at 155MB/s. The 2MB/s connections at The Xchange are connected
to Leased
Lines from Telewest. The 155MB/s server and links between switches are
carried on multimode fibre optic cable. Each server has an ATM network
card in it, click here
to see a picture of one. 