Chapter Summary

   

Rules and regulations known as network protocols control communication among systems connected on a network. The International Standards Organization has developed guidelines for the development of network protocols and has proposed a network model known as Open Systems Interconnect or OSI. This is a seven-layer network model. Layer names and their corresponding numbers are:

  1. physical layer

  2. data link layer (DLL)

  3. network layer

  4. transport layer

  5. session layer

  6. presentation layer

  7. application layer

Each layer in the layered model performs a specific operation during the data transfer process. The data transfer process originates in the application layer. The presentation layer is responsible for the conversion of data formats. The session layer establishes, manages , and terminates a communication session between two systems on a network. The transport layer is responsible for end-to-end data integrity, error detection, and correction. It fragments data received from the transport layer into packets and transfers these packets using lower level layers . The network layer is used for addressing and routing. The data link layer controls medium access and transmits data in the form of frames by using the physical layer.

During the data transfer process, an application starts the data transfer process and data travel down the layers of the protocol stack until they reach the physical layer where they are sent over to the receiving node. The reverse process takes place on the receiving node where data travel from the physical layer toward the application layer.

Layers having the same level on the sending and the receiving hosts are called peer layers. Data communication between peer layers is controlled by peer protocols. Each layer conveys its protocol information to its peer layer on the destination host. This information is called the layer header. Layer headers are added to data on the sending side and are stripped off on the receiving side.


   
Top


HP Certified
HP Certified: HP-UX System Administration
ISBN: 0130183741
EAN: 2147483647
Year: 2000
Pages: 390
Authors: Rafeeq Rehman

flylib.com © 2008-2017.
If you may any questions please contact us: flylib@qtcs.net