Computer Networking

Transport Layer

Network Protocols

Protocols are a set of rules or standards used by networks for communication of different devices connected to a network.

Protocols define what, when, and how to communicate. Devices can’t communicate without protocols.

Different layers of OSI model use different protocols.

Function of protocols

  • Sequencing Data : Breaking a long message into smaller blocks/packets.
  • Routing Data: Finding the most efficient path between source and destination before sending data.
  • Flow Data: if the sender computer is faster than receiver computer then protocols manage it.
  • Error control: it handles the errors if an error is detected.

Key elements of the protocol

I. Syntax

Syntax is the format of data for example first 8-bits represent the address of sender and last 8-bits represent the address of receiver and the rest represent the actual message.

II. Semantics

It tells the meaning of bit of each section. For example, it tells the meaning of

  • First 8-bits: represent the sender address
  • Last 8-bits: represent the destination address
  • And meaning bits: represent the actual message

iii. Timing

Timing indicates

  • When data should be sent
  • How fast it can be sent

For example sometimes sender sends the data at the speed of 100Mbps and receiver receives at the speed of 1Mbps. This overhead causes the loss of data.

Network Standards

The Network standards are design two main organizations, American national standard institute (ANSI) and IEEE.

These Network standards are very important for computer industry because they help the manufacturer to produce compatible the hardware and software’s.

Some main network standards are given below

1. Ethernet (802.3)

  • This standard is used in wired network (LAN).
  • Data Transfer rate from 10 Mbps to 100Gbps
  • Ethernet standard network follow the P2P model where no server computer is present.
  • Collision may occur when two devices attempts to send the data at the same time.  This issue can be resolve by resending data.

2. Token Ring

It is an alternative to Ethernet used in wired network (LAN). It uses a special signal called token or ticket.

Any device in the network may transmit the data only if it has a token.  Without token/ticket device cannot communicate with network. In this way there is no chance of collision. But data speed is slow as compare to Ethernet.

When a computer in token ring standard network wants to send a message it

  • Gets the token
  • Puts the data in token
  • Adds the address of receiving computer

Token passes from computer to computer, the computer whose address is match with the mentioned (destination) address in token will receive the data. It also sends the acknowledgement signals to sender to indicate that the has been received successfully.

Token ring follow the ring topology and also used in start topology. Its data transfer rate is from 4Mbps to 1Gbps.


  • TCP/IP stands for transmission control protocol/ internet protocol. This protocol is most widely used now days.
  • It transfer data over the internet through two protocols one is TCP and other is IP.
  • TCP is responsible for delivery of data. It divide the data into small packets and transfer it over the internet, these packets are resembled properly in an order when they reach at destination.
  • IP tells the address and routing information. Small Packets travel over the internet with the help of router.

4. Bluetooth

  • In this standard, data is transmitted between two Bluetooth devices using short range radio waves.
  • The distance between two devices must be within the range of 33 feet.
  • Bluetooth devices use the small chip to communicate with other Bluetooth devices.
  • Bluetooth wireless port adapter is used to convert existing USB port to Bluetooth port.
  • Mostly devices like desktop computers, notebook computers, laptops, smart phones, keyboard, mouse, printer, etc. are Bluetooth-enabled.
  • Data transfer rate is 3 Bbps.
  • Low power consumption, low speed and high security as compare to Wifi.

5. WiFi

It is wireless network standard developed by IEEE. There are various wifi standards that supports different speeds and distance explained below.

802.11 Standards Maximum Speed
802.11 b 11 Mbps
802.11 g 54 Mbps
802.11 n 300-600 Mbps
802.11 ac 1.8 to 3.6 Gbps
802.11 ad 6.7 Gbps

Example of wifi network is hotspot. Hotspot is used by mobile users to connect wifi enabled devices.

The distance between hotspot and wifi-enabled devices must be within the range of 300 feet in open area and 100 feet in closed area.

High power consumption, High speed and low security as compare to Bluetooth.

6. IrDA

  • It transmit data wirelessly through infrared light waves
  • Data transfer speed is 115 Kbps to 4Mbps
  • It requires a line-of-sight for data transmission. It means sending and receiving devices must be in line. There should be no obstacle between these devices.

7. WiMax

  • WiMax stand for worldwide interoperability for microwave access.
  • It is used for long wireless connection.
  • It is faster and has a greater range than Wi-fi.
  • WiMax devices communicate with each other’s by using radio waves via WiMax tower.
  • tower of WiMAX can cover a radius of upto 30 miles.
  • WiMax are of two types, Fixed wireless and  Mobile wireless WiMAX.

Note : some other network standards are

  • NFC (near field communication)
  • RFID (radio frequency identification)
  • WAP (wireless application protocols)

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