1. Computer Networking A Top-Down Approach Featuring the Internet Introduction Jaypee Institute of Information Technology

2. Roadmap  Introduction to Basics  Computer Network – Components | Classification  Internet  Clients and Servers  Network Models  Protocol Layers - Architecture and Services  OSI – ISO Model  TCP/IP Model  Network Edge: Connection Oriented and Connectionless Services  Network Core: Switching Techniques

3. Network Models  There are two models in computer networks:  OSI reference model  TCP/IP model

4. Roadmap  Introduction to Basics  Computer Network – Components | Classification  Internet  Clients and Servers  Network Models  Protocol Layers - Architecture and Services  OSI – ISO Model  TCP/IP Model  Network Edge: Connection Oriented and Connectionless Services  Network Core: Switching Techniques

5. What is a Protocol  A Protocol defines the format and the order of messages exchanged, the actions taken on the transmission and/or receipt of a message and other actions. Hi Got the time? 2:00 TCP connection req. TCP connection reply. time Get http://www.rpi.edu/index.htm

6. Syntax Data formats Signal levels Semantics Control information Error handling Timing Speed matching Sequencing Key Elements of a Protocols

7.  Task of communication broken up into modules  For example file transfer could use three modules  File transfer application  Communication service module  Network access module  Required for devices to communicate  Vendors have more marketable products  Customers can insist on standards based equipment Protocol Architecture (Summary)

8. Layered Architecture of Network  Network Architecture: The collection of layers and protocols.  Why layering ?  Easy to understand and maintain.  Interoperability  Flexibility  Scalability  To develop loosely coupled systems  Test components independently Note: There is no physical transfer of data across layers  Every layer follows some protocols

9. Layered Architecture  Networks organized as a stack of layers:  To offer services to the layer above it using an interface (libraries hide details while providing a service)  Reduces design complexity  Protocols: peer-to-peer layer-n conversations  Data Transfer: each layer passes data & control information to the layer below; eventually physical medium is reached.

10. Advantages Modularity – protocols easier to manage and maintain Abstract functionality –lower layers can be changed without affecting the upper layers Reuse – upper layers can reuse the functionality provided by lower layers Disadvantages Information hiding – inefficient implementations Layering - Summary

11. Roadmap  Introduction to Basics  Computer Network – Components | Classification  Internet  Clients and Servers  Network Models  Protocol Layers - Architecture and Services  OSI – ISO Model  TCP/IP Model  Network Edge: Connection Oriented and Connectionless Services  Network Core: Switching Techniques

12. OSI  Open Systems Interconnection  Developed by the International Organization for Standardization (ISO)  Seven layers  A theoretical system delivered too late!

13. OSI - The Model  A layered model  Each layer performs a subset of the required communication functions  Each layer relies on the next lower layer to perform more primitive functions  Each layer provides services to the next higher layer  Changes in one layer should not require changes in other layers

14. ISO OSI Reference Model  Seven layers  Lower three layers are peer-to-peer  Next four layers are end-to-end Application Presentation Session Transport Network Datalink Physical Application Presentation Session Transport Network Datalink Physical Network Datalink Physical Physical medium

15. OSI Layer 1-Physical Layer  Physical Layer  Physical interface between devices Mechanical (joins 1 or more signal conductor, circuits) Electrical (Representation of bits and bit rate) Functional ( function performed by individual circuits ) Procedural (sequence of events)  Modulation and Demodulation  Raw bit stream  Modem: broadly used to refer to any module that performs the function above

16. OSI Layer 2- Data Link layer  Data Link Layer  Means of activating, maintaining and deactivating a reliable link  Segmenting mechanism  Framing (Header and Trailer)  Error detection  Data synchronization( b/w transmitter and receiver)  Flow control (data congestion is not there at slow receivers due to fast senders)  Error Control (bit level error, hop-to-hop error)  MAC (Physical) Addressing

17. OSI Layer 3- Network Layer  Network Layer  Transport of information  Virtual circuit service (connection oriented)  Packet switching or datagram service (connection less)  Logical addressing (IP address)  Routing  Congestion control (flow of packet into the network)  Both connection-less and connection-oriented

18. OSI Layer 4- Transport Layer  Transport Layer  Exchange of data between end systems  Error control (end-to-end)  Flow control (end-to-end)  In sequence (segment)  No losses  No duplicates  Quality of service( Throughput, transit delay, error rate)