1. Computer Networking A Top-Down Approach Featuring the Internet
Introduction

2. Roadmap Introduction to Basics Network Models
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 Protocol Layers - Architecture and Services Network Models
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
TCP connection req. Hi
TCP connection reply.
Got the
time?
Get
2:00
<file>
time

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

7. Protocol Architecture (Summary)
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

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. Layering - Summary Advantages Disadvantages
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

11. Roadmap Protocol Layers - Architecture and Services Network Models
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
Application
Presentation
Presentation
Session
Session
Transport
Transport
Network
Network
Network
Datalink
Datalink
Datalink
Physical
Physical
Physical
Physical medium

15. OSI Layer 1-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
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
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
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)