Group13_Avani:Protocol stack and addressing

A protocol stack/communication stack is a particular software implementation of a computer networking protocol suite.
The Open System Interconnection Reference Model (OSI Reference Model or OSI Model) is an abstract description for layered communications and computer network protocol design. It is a prescribed hierarchy of software layers, starting from the application layer at the top to the physical layer at the bottom. The stack resides in each client and server.

OSI MODEL

LAYER -FUNCTION

7. Application -Network process to application

6. Presentation -Data representation and encryption

5. Session -Interhost communication

4. Transport -End-to-end connections and reliability

3. Network -Path determination and logical addressing

2. Data link -Physical addressing

1. Physical -Media, signal and binary transmission

A client application sends data down its protocol stack, passing through each of the protocols and interfaces. At the receiving side, the data packets traverse a similar stack of protocols and programs, this time in reverse. Starting at the physical layer, the packet passed through each successive layer until it reaches the top of the stack at the relevant application process. At each layer, the information appended by the different protocols is examined so that the host can forward the packet to its final destination. For the host to accomplish this, both the client and the host need to run the same program at each level.
To deliver data between two Internet hosts, it is necessary to move data across the network to the correct host, and within that host to the correct user or process. One of the schemes used by TCP/IP to accomplish these tasks is protocol stack addressing which deliver data to the correct host.
Specification used for multiple protocol stack addressing are:
• Media Access Control (MAC) driver: This is a device driver written by the vendors of the NIC that directly interfaces with the NIC hardware.
• Upper-Level Protocol driver
• Protocol manager program
To avoid confusion with MAC addresses, which are machine or station addresses, the term IP address will be used to designate this kind of address.Since the network and data link layer use different addressing schemes, some system is needed to convert or map the IP addresses to the MAC addresses. Transport-layer services and user processes use IP addresses to identify hosts, but packets that go out on the network need MAC addresses. The Address Resolution Protocol (ARP) is used to convert the 32-bit IP address of a host into its 48-bit MAC address. When a hosts wants to map an IP address to a MAC address, it broadcasts an ARP request on the network, asking for the host using the IP address to respond. The host that sees its own IP address in the request returns its MAC address to the sender. With a MAC address, the sending host can transmit a packet on the Ethernet and know that the receiving host will recognise it.