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Physical layer

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Various Connecting Devices use at Physical layer

connecting devices can be classified in five  ways:

1. Those who work below the physical layer

2. Those who work at the physical layer.

3. Those who work between the physical layer  and data link layer

4.Those who operate at the physical layer data link layer and network layer.

5. Those who operated at all five layers. ex: gateway

 

1.Repeaters:

  1. A repeater works only at the physical layer.
  2. It is used to connects two or more segments of the same LAN.
  3. It does not connect two or more different LAN but it connects segments of same LAN.
  4. It is used to increase the domain of the LAN. When you have to increase the length of a LAN. you divide the LAN into multiple segments and connect those segments with the help of repeaters.
  5. A repeater is not an amplifying device. It does not amplify the signal.
  6. It generates the same signal on the other side of the LAN.
  7. Since it has only one layer Physical layer, it can't filter the packet it receives. 
  8. Collison domain of a repeater is very high.
  9. A repeater placed on the line before the legibility of the signal
    becomes lost can still read the signal well enough to determine the intended voltages and replicate them in their original form.

2. Hub:-

  1. A multiport repeater is called a hub.
  2. It works on the physical layer, So again like a repeater, it can't filter the packets.
  3. Collision Domain inside a hub is very high.

 

 

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1. Physical Layer

Physical layers deal with the physical aspect of communication.

Functionality:-

1. Bits Representation:

Physical layers get data from the data link layer in the form of bits (the combination of 0's and 1's), So it is the responsibility of the physical layer to convert the bits inappropriate signals because in wires or cables data flow in the form of lights.

2. Data rate: longest duration to which a but can last in the medium.

3.Synchronization of bits: 

4. Physical topology: Deals with how multiple devices are connected in a network.

5.Transmission mode:  Deals with how devices can send and receive data.

 

1. Types of Transmission mode:

There are three types of transmission mode:

1. Simplex:- In simplex, there is one sender and one receiver. There is a  sending device which only sends and other is receiving devices which only receives. It is one-way communication. Example: TVs and Remote. Tv is receiving the signals and remote only sends the signals.

              

2. Half Duplex:-

At a time you can either receive or you can send but you can't do both at the same time.ex: Walky Talky.

3. Full Duplex:-

Here there are no such restrictions. you can receive or send data at the same time.

 

 

 

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Computer Networks