Internet Protocol Notes

What is Protocol ?

Protocols mean set of rules. It is a formal description of message formats and the rules two or more machines has follow to exchange messages. The key elements of a protocol are syntax, semantics and timing.

·         Syntax

Syntax refers to the structure or format of the data, meaning the order in which they are presented.

·         Semantics

Semantics refers to the meaning of each section of bits.

·      Timing

Timing refers to when data should be sent and how fast it can be sent.

Internetworking Technologies

Internetworking Technologies tell how the Internet accommodating multiple underlying hardware technologies and how they are interconnected and formed the network, and set of communication standard which the network used to inter-operate.

The lowercase internet means multiple networks connected together, using a commonprotocol suite. The uppercase Internet refers to the collection of hosts around the world that can communicate with each other using TCP/IP. While the Internet is an internet, the reverse is not true.

What is IP ? -

IP (Internet Protocol) does most of the work in the TCP/IP protocol suite. All protocols and applications within the TCP/IP suite run on top of IP and utilize it for logical Network layer addressing and transmission of datagrams between internet hosts. IP maps to the Internet layer of the DoD and to the Network layer of the OSI models. ICMP (Internet Control Message Protocol) is considered an integral part of IP.

Introduction to TCP/IP Protocols

·           TCP/IP Reference Model

·           Internet Protocol (IP)

·           Forwarding an IP Datagram

·           IP Datagram Format

·           IPv6 Enhancements

·           Domain Name Service

·           TCP: Key Features

·           User Datagram Protocol (UDP)

Internet Protocol (IP)

Layer 3 protocol that forwards datagrams across internet

Uses routing tables prepared by routing protocols, e.g., Open Shortest Path First (OSPF),

·         Routing Information Protocol (RIP)

·         Connectionless service

·         vs connection-oriented (circuits)

Transmission Control Protocol TCP

TCP is a connection oriented protocol and offers end-to-end packet delivery. It acts as back bone for connection.It exhibits the following key features:

·         Transmission Control Protocol TCP corresponds to the Transport Layer of OSI Model. TCP is a reliable and connection oriented protocol.

·         TCP offers:

·         Stream Data Transfer. Reliability.

·         Efficient Flow Control Full-duplex operation. Multiplexing.

·         TCP offers connection oriented end-to-end packet delivery.

·         TCP ensures reliability by sequencing bytes with a forwarding acknowledgement number that indicates to the destination the next byte the source expect to receive.

·         It retransmits the bytes not acknowledged with in specified time period.

TCP Services

·         TCP offers following services to the processes 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

TCP protocol is stream oriented because it allows the sending process to send data as stream of bytes and the receiving process to obtain data as stream of bytes

Sending and Receiving Buffers

It may not be possible for sending and receiving process to produce and obtain data at same speed, therefore, TCP needs buffers for storage at sending and receiving ends.

Bytes and Segments

The Transmission Control Protocol TCP, at transport layer groups the bytes into a packet. This packet is called segment. Before transmission of these packets, these segments are encapsulated into an IP datagram.

Full Duplex Service

Transmitting the data in duplex mode means flow of data in both the directions at the same time.

Connection Oriented Service

TCP offers connection oriented service in the following manner:

·         1.  TCP of process-1 informs TCP of process – 2 and gets its approval.

·         2.  TCP of process – 1 and TCP of process – 2 and exchange data in both the two directions.

·         3.     After completing the data exchange, when buffers on both sides are empty, the two TCP’s destroy their buffers.

Reliable Service

For sake of reliability, TCP uses acknowledgement mechanism.

Internet Protocol IP

·         Internet Protocol is connectionless and unreliable protocol. It ensures no guarantee of successfully transmission of data.

·         In order to make it reliable, it must be paired with reliable protocol such as TCP at the transport layer.

·         Internet protocol transmits the data in form of a datagram as shown in the following diagram:

Points to remember:

·         The length of datagram is variable.

·         The Datagram is divided into two parts: header and data.

·         The length of header is 20 to 60 bytes.

·         The header contains information for routing and delivery of the packet.

User Datagram Protocol UDP

·         Like IP, UDP is connectionless and unreliable protocol. It doesn’t require making a connection with the host to exchange data. Since UDP is unreliable protocol, there is no mechanism for ensuring that data sent is received.

·         UDP transmits the data in form of a datagram. The UDP datagram consists of five parts as shown in the following diagram:

Points to remember:

·         UDP is used by the application that typically transmit small amount of data at one time.

·         UDP provides protocol port used i.e. UDP message contains both source and destination port number, that makes it possible for UDP software at the destination to deliver the message to correct application program.

File Transfer Protocol FTP

·         FTP is used to copy files from one host to another. FTP offers the mechanism for the same in following manner:

·         FTP establishes two different connections: one is for data transfer and other is for control information.

·         Control connection is made between control processes while Data Connection is made between

·         FTP uses port 21 for the control connection and Port 20 for the data connection.

·         FTP creates two processes such as Control Process and Data Transfer Process at both ends

·         i.e. at client as well as at server.

HTTP Request

HTTP request comprises of lines which contains: Request link

Trivial File Transfer Protocol TFTP

Trivial File Transfer Protocol is also used to transfer the files but it transfers the files without authentication.. Unlike FTP, TFTP does not separate control and data information. Since there is no authentication exists, TFTP lacks in security features therefore it is not recommended to use TFTP.

Key points

TFTP makes use of UDP for data transport. Each TFTP message is carried in separate UDP datagram..

The first two bytes of a TFTP message specify the type of message.

The TFTP session is initiated when a TFTP client sends a request to upload or download a file. The request is sent from an ephemeral UDP port to the UDP port 69 of an TFTP server. 

Telnet

Telnet is a protocol used to log in to remote computer on the internet. There are a number of Telnet clients having user friendly user interface. The following diagram shows a person is logged in to computer A, and from there, he remote logged into computer B..

Hyper Text Transfer Protocol HTTP

HTTP is a communication protocol. It defines mechanism for communication between browser and the web server. It is also called request and response protocol because the communication between browser and server takes place in request and response pairs