1. Class Notes CS403- Internet Technology Prepared by: Gulrez Alam Khan

2. Week-1 (Lecture-1) Introduction to Networks What is a computer Network? A network is any collection of independent computers that communicate with one another over a shared network medium. When these computers are joined in a network, people can share files and peripherals such as modems, printers, tape backup drives, or CD-ROM drives Every network includes: At least two computers Server or Client. Networking Interface Card's (NIC) A connection medium Ex. wire or cable Network Operating system software Ex. Microsoft Windows NT or 2000

3. Week-1 (Lecture-1) Types of Networks LAN (Local Area Networks) Within a building Small and basic network WAN (Wide Area Networks) Connect multiple LANs together Ex. Connect two rooms LANs MAN (Metropolitan area Networks) A network of computers with in a City. Ex. Connects two buildings.

4. Week-1 (Lecture-1) Intranet A private network utilizing Internet-type tools Within an organization i.e. Large organizations Internet System of linked networks worldwide in scope facilitate data communication services Ex. remote login, file transfer, electronic mail World Wide Web and newsgroups.

5. Week-1 (Lecture-1) VPN (Virtual Private Network) For safe network access. It uses a technique known as tunneling to transfer data securely on the Internet.

6. Week-1 (Lecture-1) LAN Topologies Each network is classified into a category Each category contain its advantages and disadvantages. The four basic topologies are: 1.Bus Topology 2.Ring Topology 3.Star Topology 4.Mesh Topology

7. Week-1 (Lecture-1) Bus Topology: Single cable to which all computers connected. Computer passes signal through bus. A signal send by one computer can be received by any computer. Advantages Very simple communication Fast communication Disadvantages If bus cable not working? Creates the problem for network Can not apply a fast algorithm to send message.

8. Week-1 (Lecture-1) Ring Topology: Computers to be connected in a closed loop Needed for the ring to continue operation even if some of the computers are disconnected Use token system for communication Advantages very organized (reduces chances of collision) Fast (traffic flows in only one direction). Disadvantages Each packet of data must pass through all the computers between source and destination. Network is highly dependent on the wire.

9. Week-1 (Lecture-1) Star Topology: All computers attach to an electronic central point (HUB). HUB: Accepts data from a sending computer and delivers it to the appropriate destination. Advantages Easy to connect new nodes or devices Failure of one node or link doesn’t affect the rest of network Disadvantages Too much dependency on central device Central device increases the overall cost of the network.

10. Week-1 (Lecture-1) Mesh Topology: Direct connection between each pair of computers. In mesh topology: No. of computers = n, no. of connections = c then c = n(n-1) / 2 or n2 – n – 2c = 0 And c>n in any case. Advantages Data can be transmitted from different devices simultaneously Failure of one node or link doesn’t affect the rest of network Disadvantages Cost is very high. high chances of redundancy.

11. Week-1 (Lecture-2) Network Interface Card (NIC) A device that plugs into a motherboard and provides ports for the network cable connections. It is the computer's interface with the LAN.

12. Week-1 (Lecture-2) Network HUB: A point where data converges from one directions and is forwarded to another directions. Seen in local area networks Ex. Ethernet hub, active hub, network hub, repeater hub, multiport repeater Gateways: A network point that acts as an entrance to another network Both networks uses different protocols network. It contain protocol translators, impedance matching devices or signal translators as necessary to provide system Interoperability. Also contain mutually acceptable administrative procedures between both networks.

13. Week-1 (Lecture-2) Routers: This device determines the next network point to which a packet should be forwarded toward its destination. Allow different networks to communicate with each other Perform the "traffic directing" functions on the Internet Router creates and maintain a table of the available routes and their conditions and uses this information along with distance and cost algorithms to determine the best route for a given packet. A packet will travel through a number of network points with routers before arriving at its destination.

14. Week-1 (Lecture-2) Bridge: A bridge is a product that connects two LANs that uses the same protocol. Ex. Ethernet or token ring. It examines each message on a LAN, "passing" those known to be within the same LAN. Its of three types. 1.Local bridge 2.Remote bridge 3.Wireless bridge

15. Week-1 (Lecture-2) Difference between (Bridge, Router, Gateway): Bridge: Device to interconnect two LANs that use the SAME logical link control protocol but may use different medium access control protocols. Router: Device to interconnect SIMILAR networks, e.g. similar protocols and workstations and servers. Gateway: Device to interconnect DISSIMILAR protocols and servers, and Macintosh and IBM LANs and equipment

16. Week-1 (Lecture-2) Modulation: conversion of the digital computer signals (high/low, on/off or logic 1 and 0 states) to audio-frequency tones. Demodulation: Converts the audio tones back into digital signals that a computer can understand directly.