January 14, 2003Week 2: Day 1
Welcome to the Course!
Remember that topology, diagram, map, and layout all refer to the physical installation of the network as well as the protocols and communications methods used.
The
bus topology as the simplest of all networking topologies. All computers are
connected to a single backbone, over which all communication takes place. A
single cable break in a bus topology network can cause all network communication
to cease. When a computer has data to send, it addresses the data and places
it on the wire. The data is received by all computers, but only the computer
the data is destined for accepts the data packets. Only one computer can send
data at a time. Because of this, the larger a bus network gets, the slower communication
is.
The
bus topology is a passive topology. This means that the computers on the bus
listen for data being sent. They do not take an active role in forwarding data
to the destination computer. A signal continues through the network until it
is absorbed by a terminator. If a cable break occurs, there is no termination,
and the signal continues to bounce indefinitely. Although it is very easy to
expand a bus network, the topology is still limited to the maximum cable distance
of the network architecture. We will discuss this in more detail in Chapter
3. As the cable reaches its maximum distance, a phenomenon called attenuation
occurs. This means that the signal is weakened over distance. However, a repeater
can be placed on the segment to increase the strength of the signal.
Star TopologyThe star topology network connects all computers at a central point, the hub. This is convenient for administration, but requires a more intricate cabling installation. One of the biggest attractions of the star topology network is that, if a cable run from a workstation to the hub fails, only that workstation is effected, it does not effect the rest of the network.
As
opposed to bus and star topologies, rings are active topologies. This is because
each computer in the network is responsible for transmitting the data to the
next computer in line. It is important to note that not all ring networks are
physically wired as rings. Token ring networks are generally wired as stars,
whereas FDDI network are wired as true rings.
Like bus networks, a single computer or cable failure effects communication
on the entire network. However, many modern ring topologies use smart hubs what
recognize a computer or cable failure and automatically reroute network traffic
around the failure. With ring topology networks, equal access is given to each
network resource so that no single computer can monopolize the network.
On Thusday, we will discuss Hubs, Switches, and Selection criteria.
Here is today's case project. What do you think?
The 15 computers in Cindy’s office are scattered over two floors of a single building. Each floor has a central telephone room with access to the other floor. She has been asked to connect the computers in a peer-to-peer network. What type of network should Cindy implement?