In data communication terminology, a transmission medium is a physical path between the transmitter and the receiver i.e it is the channel through which data is sent from one place to another. Transmission Media is broadly classified into the following types:
1. Guided Media:
It is also referred to as Wired or Bounded transmission media. Signals being transmitted are directed and confined in a narrow pathway by using physical links.
Features:
- High Speed
- Secure
- Used for comparatively shorter distances
There are 3 major types of Guided Media:
(i) Twisted Pair Cable –
It consists of 2 separately insulated conductor wires wound about each other. Generally, several such pairs are bundled together in a protective sheath. They are the most widely used Transmission Media. Twisted Pair is of two types:
1.Unshielded Twisted Pair (UTP):
This type of cable has the ability to block interference and does not depend on a physical shield for this purpose. It is used for telephonic applications.
Advantages:
- Least expensive
- Easy to install
- High-speed capacity
Disadvantages:
- Susceptible to external interference
- Lower capacity and performance in comparison to STP
- Short distance transmission due to attenuation
2. Shielded Twisted Pair (STP):
This type of cable consists of a special jacket to block external interference. It is used in fast-data-rate Ethernet and in voice and data channels of telephone lines.
Advantages:
- Better performance at a higher data rate in comparison to UTP
- Eliminates crosstalk
- Comparatively faster
Disadvantages:
- Comparatively difficult to install and manufacture
- More expensive
- Bulky
(ii) Coaxial Cable –
It has an outer plastic covering containing 2 parallel conductors each having a separate insulated protection cover. Coaxial cable transmits information in two modes: Baseband mode(dedicated cable bandwidth) and Broadband mode(cable bandwidth is split into separate ranges). Cable TVs and analog television networks widely use Coaxial cables.
Advantages:
- High Bandwidth
- Better noise Immunity
- Easy to install and expand
- Inexpensive
Disadvantages:
- Single cable failure can disrupt the entire network
(iii) Optical Fibre Cable –
It uses the concept of reflection of light through a core made up of glass or plastic. The core is surrounded by a less dense glass or plastic covering called the cladding. It is used for transmission of large volumes of data.
Advantages:
- Increased capacity and bandwidth
- Lightweight
- Less signal attenuation
Disadvantages:
- Difficult to install and maintain
- High cost
- Fragile
2. Unguided Media:
It is also referred to as Wireless or Unbounded transmission media.No physical medium is required for the transmission of electromagnetic signals.
Features:
- A signal is broadcasted through the air
- Less Secure
- Used for larger distances
There are 3 major types of Unguided Media:
(i) Radiowaves –
These are easy to generate and can penetrate through buildings. The sending and receiving antennas need not be aligned. Frequency Range:3KHz — 1GHz. AM and FM radios and cordless phones use Radiowaves for transmission.
Further Categorized as (i) Terrestrial and (ii) Satellite.
(ii) Microwaves –
It is a line of sight transmission i.e. the sending and receiving antennas need to be properly aligned with each other. The distance covered by the signal is directly proportional to the height of the antenna. Frequency Range:1GHz — 300GHz. These are majorly used for mobile phone communication and television distribution.
(iii) Infrared –
Infrared waves are used for very short distance communication. They cannot penetrate through obstacles. This prevents interference between systems. Frequency Range:300GHz — 400THz. It is used in TV remotes, wireless mouse, keyboard, printer, etc.
The cast term here signifies some data(stream of packets) is being transmitted to the recipient(s) from the client(s) side over the communication channel that helps them to communicate. Let’s see some of the “cast” concepts that are prevailing in the computer networks field.
1. Unicast –
This type of information transfer is useful when there is a participation of a single sender and a single recipient. So, in short, you can term it as a one-to-one transmission. For example, a device having IP address 10.1.2.0 in a network wants to send the traffic stream(data packets) to the device with IP address 20.12.4.2 in the other network, then unicast comes into the picture. This is the most common form of data transfer over the networks
2. Broadcast –
Broadcasting transfer (one-to-all) techniques can be classified into two types:
Direct Broadcasting –
This is useful when a device in one network wants to transfer packet stream to all the devices over the other network. This is achieved by translating all the Host ID part bits of the destination address to 1, referred to as Direct Broadcast Address in the datagram header for information transfer.
This mode is mainly utilized by television networks for video and audio distribution.
One important protocol of this class in Computer Networks is [Address Resolution Protocol (ARP)] that is used for resolving the IP address into a physical address which is necessary for underlying communication.
3. Multicast –
In multicasting, one/more senders and one/more recipients participate in data transfer traffic. In this method traffic recline between the boundaries of unicast (one-to-one) and broadcast (one-to-all). Multicast lets the server’s direct single copies of data streams that are then simulated and routed to hosts that request it. IP multicast requires the support of some other protocols like IGMP (Internet Group Management Protocol), Multicast routing for its working. Also in Classful IP addressing Class D is reserved for multicast groups.
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