cn-computer newtwork ppt

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					                           Types of links

• Broadcast links:
  -Single communication channel is shared by all machines.
  -Packets [messages/contexts] sent by any machine received by all.
  -Packet [Address field] : Specifies intended recipient.
  -Receiver checks address field.

• Point-to-point links:
  -localized networks use broadcasting, larger use point-to-point.
  -packets from source are transferred via intermediate machines to
  destination. [finding best route is important].
                     Categories of Networks

•   Local Area Networks
•   Metropolitan Area Networks
•   Wide Area Networks
•   Internetworks
                        Broadcast Networks

• Classification of interconnected processors by scale.
                    Local Area Networks
 – privately owned and links the devices in a single office, building,
   or campus.
 - Limited to few kilometers.
 - Allow resources (both h/w & s/w) to be shared.
Eg: Server-large capacity disk drive (provide service to clients).
LAN can be distinguished by the parameters:
    2.transmission media ---which?
    3.topology (bus, ring, star)
- Data Rate:        4 to 16 Mbps – earlier
              100 0r 1000 Mbps - nowadays
 - Hub: A central device in a star topology that provides a common
   connection among the nodes.
An isolated LAN connecting 12 computers to a hub in a closet
             Metropolitan Area Networks

• Size between a LAN and a WAN.
• Designed for customers,
  - who need a high speed connectivity net
  - have endpoints over a city
• Eg:
  - Telephone company network
  - Cable TV network
                 Metropolitan Area Networks
•   Television signals & internet being fed into headend for distribution to homes.
                  Wide Area Networks

• Long-distance transmission of data, image, audio & video
  over large geographical area. [country, continent]
• Two types of WAN:
               - Switched WAN
               - Point-to-Point WAN
• Switched WAN:
  - connects end systems comprise a router (internet-working
  connecting device) that connects to another LAN or WAN.
• Point-to-Point WAN:
  - connects home computer or a small LAN to an ISP.
WANs: a switched WAN and a point-to-point WAN
                      Wide Area Networks
• Relation between hosts on LANs and the subnet.
• Subnet : carry messages from host to host.
• Subnet: 1.Transmission lines (move bits b/w m/cs, made of wires, fibres etc)
           2. Switching elements (routers)
                 - computers connect one or more transmission lines.
                 - choose outgoing line to forward data.
                       Wide Area Networks
•   Sending host cuts messages into packets, then packets are injected into n/w.
•   Stream of packets are transported from sender to receiver.
•   Packet is routed via ACE instead of ABDE, ACDE.
•   Routing decision is made by router A based on algorithm.
                        Internetwork:connection of two or more networks.

A heterogeneous network made of four WANs and two LANs
                     THE INTERNET

•The Internet is a communication system that has
brought a wealth of information to our fingertips and
organized it for our use.
•A network is a group of connected communicating devices such as
computers and printers.
•An internet is two or more networks that can communicate with
each other.

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