Internet Protocols - Internet Technologies

What are Internet Protocols?

Transmission Control Protocol (TCP)

  • It is a connection oriented protocol providing end-to-end delivery of packets. It acts as backbone for the connection. Below are the key features.
  • Transmission Control Protocol (TCP) corresponds to the Transport Layer of OSI Model.
  • TCP is considered to be reliable and connection oriented protocol.

TCP provides:

  • Stream Data Transfer.
  • Reliability.
  • Efficient Flow Control
  • Full-duplex operation.
  • Multiplexing.
  • End-to-end packet delivery is provided by TCP connection.

Reliability is ensured as TCP sends the bytes in sequence with a forwarding acknowledgment number which informs the destination about the next byte the source expect to receive.

Bytes that are not acknowledged are re-transmitted in specified time period.

TCP Services

Below are the services TCP provides to the process at the application layer.

  • Stream Delivery Service
  • Sending and Receiving Buffers
  • Bytes and Segments
  • Full Duplex Service
  • Connection Oriented Service
  • Reliable Service

STREAM DELIVER SERVICE

Data is sent and received in stream of bytes so TCP protocol is stream oriented.

SENDING AND RECEIVING BUFFERS

As it is not possible to have same speed at the sending and receiving end, TCP needs buffers to store the data at both sending and receiving ends.

BYTES AND SEGMENTS

Segment is the grouping of the bytes into a packet. Before sending these segments, they are encapsulated into an IP datagram.

FULL DUPLEX SERVICE

Full duplex means transmitting data in both the directions at the same time.

CONNECTION ORIENTED SERVICE

  • TCP provides connection oriented service in the below manner:
  • TCP of process-1 notifies TCP of process – 2 and to get its approval.
  • TCP of process – 1 and TCP of process – 2 and data is exchanged in both the directions.

Once the data is exchanged and the buffers are empty, the two TCP’s destroy their buffers.

RELIABLE SERVICE

TCP uses acknowledgement mechanism for the sake of Reliability.

Internet Protocol (IP)

IP is unreliable protocol means it does not ensure the guarantee of successful transmission of data.

It becomes reliable once it is paired up with TCP protocol at the transport layer.

Below diagram shows the Internet protocol transmitting data in form of a datagram.

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Points to note:

The datagram length can be varied.

  • It is divided into header and data section.
  • Header length can be 20 to 60 bytes.
  • Information for routing and delivering the packet is in header section.

User Datagram Protocol (UDP)

Similar to IP, UDP is also unreliable and connectionless protocol. Having a connection with the host for exchanging data is not required. There is no guarantee that the data sent is received at the other end.

Data is sent in form of a datagram in UDP and has five parts as shown below.

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Points to note:

Applications that send small amounts of data at one time use UDP.

UDP offers the protocol port being used. The message has both source and destination port number that helps UDP software at the receiving end to route the message to correct application program.

File Transfer Protocol (FTP)

FTP is used in copying the files from one host to another. Below is the mechanism for the FTP.

  • FTP creates two processes i.e. Control Process and Data Transfer process at both ends, client as well as at server.
  • Two different connections are made, one is data transfer and other is for control information.
  • Port 21 is used for control connection and Port 20 for data connection.

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Trivial File Transfer Protocol (TFTP)

A TFTP transfer file without authentication and due to this security is the concern and it is not preferred to use TFTP. It does not divide the control and data information.

Key points

  • UDP is used for transporting data.
  • Type of a message is specified with first two bytes.
  • When the TFTP client sends a request to download or upload a file, the TFTP session starts.
  • Request is transmitted from an ephemeral UDP port to the UDP port 69 of a TFTP server.

Difference between FTP and TFTP

S.N.

Parameter

FTP

TFTP

1

Operation

Transferring Files

Transferring Files

2

Authentication

Yes

No

3

Protocol

TCP

UDP

4

Ports

21 – Control, 20 – Data

Port 3214, 69, 4012

5

Control and Data

Separated

Separated

6

Data Transfer

Reliable

Unreliable

Telnet

Using Telnet protocol, one can log in to a remote computer on the internet. Number of Telnet clients are available which are user friendly. Below diagram depicts the user logged into computer A and from there, he remote logged into computer B.

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Hyper Text Transfer Protocol (HTTP)

HTTP is a communication protocol defining the mechanism for browser and web server communication. As the communication happens in request and response pairs, it is also called as request and response protocol.

HTTP Request

HTTP request consists of lines which contain below:

  • Request line
  • Header Fields
  • Message body

Key Points

  • The first line of the request specifies the request method i.e. Post or Get.
  • Second line has the header section indicating the DNS from where index.htm is retrieved.

HTTP Response

HTTP response has a certain structure similar to request. HTTP response contains:

  • Status line
  • Headers
  • Message body

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