Categories of Networks-Cont

WAN

o    Generally cover a large geographical area and it usually span an Unlimited number of miles by utilizing Public or Leased networks instead of having their own hardware as in the case of LANs o    Design of a WAN    Typically , it consists of a large number of Switching Nodes    Transmission from any one device is routed through these internal nodes to the specified destination device    These  nodes  are  not  concerned  with  the  content  of  the  data,  rather  their purpose is to provide a switching facility that will move the data from node to node until it reaches its destination o    How to Implement a WAN?    Traditionally WAN s have been implemented using one of the 2 technologies: -Circuit Switching -Packet Switching o    Frame Relay and ATM Networks play important role nowadays too  ™  Circuit Switching o    A  dedicated  communication  path  is  established  between  two  stations  through  the nodes of the network o    This path/CAPACITY stays up for the duration of the communication Example is Telephone Network ™  Packet Switching o    No capacity is dedicated along a path through the network o    Data Is sent out in small chunks called "Packets" o    Each path is passed from node to node o    At each node, entire packet is received, stored briefly and then transmitted to the next node.    Example is : Computer to Computer Communication Frame Relay & ATM o    Overhead bits for Error Protection are removed o    10's of 100's of Mbps and also Gbps is possible Summary     The OSI Model     Layered Architecture     Encapsulation and Decapsulation     Physical Layer     Data Link Layer Reading Sections     Section 2.4,2.5, "Data Communications and Networking" 4th Edition by Behrouz A. Forouzan     Sections  1.3,  "Data  and  Computer  Communication"  6th  Edition  by  William Stallings