Topology

Topology is defined into physical and logical.

• Physical topology of a network refers to how the cables are arranged
• Logical topology of a network refers to hoe the packets sent

Physical Bus Logical Bus Topology

Also called Linear Bus, which consists of a single cable called backbone ( trunk/segment) that connects all computers on the network in a line.

In this topology, electronic signals is sent to all of the computers on the network, and the data is accepted only by the computer matches the address in the signal.

Signal Bounce

Because the signal is sent to the entire network, if the signal continue uninterrupted, it'll keep bouncing back along the cable. Which means others computers on the network cannot sent data. So we use a terminator to absorbing the signal.

Disadvantages:

1. Difficult to troubleshoot and reconfigure
2. A break in the cable brings the whole network down.

suited for temporary network or network that have less than 10 computers.

Physical Ring Logical Ring Topology

Connects computers in a circle, there are no terminated ends. The signals travel around the loop in one direction and transmitted from one computer to the next computer. (function as repeater)

Disadvantages:

1. A break in a cable or a failure computer or network card can bring down the entire network

This Topology is very rare.

Physical Star Logical Bus Topology (Star Bus topology)

For a logical bus hub (Ethernet hub), signals are transmitted from the sending computer through the hub to all computer on the network.

CSMA/CD

CSMA/CD is media access method and stands for Carrier Sense Multiple Access with Collision Detection, usually use with a logical bus network.

It is a passive topology.

Connecting more than one Ethernet Hubs

we usually use UTP cable in Ethernet

Standard UTP cable

• use to connect computers to hub's standard port
• use to connect hub's standard port to another hub's uplink port

Crossover UTP Cable

• Use to connect computer to computer without hub.
• use to connect hub's standard port to another hub's standard port.

Physical Star Logical Ring (Star Ring Topology)

token passing is also a media access method.

The first started computer make a free token transmit to the network around a ring. Computer must wait for a free token before transferring data.

When a computer receives a free token, it modifies the token and transmits the data around the ring.

When the data is received by the destination computer, an acknowledgment is generated and returned to the source computer. After verifying the acknowledgment, the source computer creates a new free token and pass around the network.

in this topology, only one computer holding the token can send the data, it prevents data collisions.

It is an active topology. Computers act like repeaters to boost the signals.

Token Ring Hub

• Token Ring Hub
• MAU (Multistation Access Unit)
• MSAU (MultiStation Access Unit)
• SMAU (Smart Multistation Access Unit)

Advantages of using physical topology:

1. If a break of cable or failure of computer or network card, only the computer failed to connect the network.
2. centralized management because the hub has LEDs.
3. Easy to troubleshoot and reconfigure.

Disadvantages:

1. If the hub fails, the entire network will fail.
2. Each computer is connected to a central point, so it needs more cabling.

Connecting with MAUs