The function of Internet Protocol

The Internet Protocol is responsible for addressing hosts and for routing data-grams (packets) from a source host to a destination host across one or more IP networks. For this purpose, the Internet Protocol defines the format of packets and provides an addressing system that has two functions: identifying hosts; and providing a logical location service.

Data gram construction

Each data gram has two components: a header and a payload. The IP header is tagged with the source IP address, the destination IP address, and other meta-data needed to route and deliver the data gram.

IP addressing and routing

IP addressing entails the assignment of IP addresses and associated parameters to host interfaces.The address space is divided into networks and sub networks, involving the designation of network or routing prefixes.

Describe functions of different layers of OSI model.

  • Physical Layer: The physical layer is responsible for transmit in raw bit streams between two nodes. That is, it may convert the sequence of binary digits into electrical signals; light signals, or electromagnetic signals, depending on whether the two nodes are on a cable circuit, fiber-optic circuit, or microwave/radio circuit, respectively.
  • Data-Link Layer: The physical layer simply transmits the data from the sender’s mode to the receiver’s node as raw bits. It is the responsibility of the data-link layer to detect and correct any errors in the transmitted data. Since the physical layer is only concerned with a raw bit stream, the data-link layer partitions it into frames, so that error detection and correction can be performed independently for each frame. The data-link layer also performs flow control of frames between two sites.
  • Network Layer: The network layer is responsible for setting up a logical path between two nodes for communication to take place. It encapsulates frames into packets, which can be transmitted from one node to another by using a high-level addressing and routing scheme.
  • Transport Layer: The transport layer accepts message of arbitrary length from the session layer,
    segments them into packets, submits them to the network layer for transmission, and finally
    reassembles the packets at the destination. The transport layer protocols include mechanisms for handling lost and out-of-sequence packets. For this, the transport layer records a sequence number in each packet, and uses the sequence numbers for detecting lost packets and for- ensuring that messages are reconstructed in the correct sequence.
  • Session Layer: The session layer provides means of establishing, maintaining and terminating a dialogue or a session between two end users.
  • Presentation Layer: The presentation layer provides facilities to convert message data into a form, which is meaningful to the communicating application layer entities. Performs such transformation are Code conversion, compression, encryption and decryption etc.
  • Application Layer: the application layer provides services that directly support the end users on the network. It is a collection of miscellaneous protocols for various commonly used applications, such as electronic mail, file transfer, remote login, remote job entry etc.