A Communication Model. Dr. Indranil Sen Gupta. Data Commn. & Networking:
Introduction. Slide 3. Figure 1.1 from the book by Stallings ...
Data Communication & Networking: An Introduction
Dr. Indranil Sen Gupta
Data Commn. & Networking: Introduction
Slide 1
Introduction • The 1970s and 1980s have seen a merger of computer science and data communication. • Byproducts of the revolution: – No fundamental differences between data processing equipments (computers) and data communication equipments (transmission, switching). – No fundamental differences among data, voice, and video communication. – The dividing lines between uniprocessors, multiprocessors, LAN, MAN and WAN have blurred. Dr. Indranil Sen Gupta
Data Commn. & Networking: Introduction
Slide 2
A Communication Model
Figure 1.1 from the book by Stallings
Dr. Indranil Sen Gupta
Data Commn. & Networking: Introduction
Slide 3
Key Elements of the Model • Source: generates the data to be transmitted (e.g. telephones, PCs). • Transmitter: transforms and encodes the information in such a way as to produce signals that can be transmitted across sore sort of transmission system (e.g. MODEM). • Transmission System: a single transmission line or a complex network connecting source and destination. • Receiver: accepts the signal from the transmission system and converts it into a form that can be handled by the destination device. • Destination: takes the incoming data from the receiver. Dr. Indranil Sen Gupta
Data Commn. & Networking: Introduction
Slide 4
Some of the key tasks performed by a data communication system • Transmission system utilization • Interfacing • Signal generation • Synchronization • Error detection and correction • Flow control
Networking Concepts • In its simplest form, data communication takes place between two devices that are directly connected by some point-to-point transmission medium. • Sometimes they may not be directly connected: – The devices are very far apart. – Many links may be shared.
• Solution? – Attach each device to a communications network. Dr. Indranil Sen Gupta
Data Commn. & Networking: Introduction
Slide 7
Figure 1.3 from the book by Stallings
Dr. Indranil Sen Gupta
Data Commn. & Networking: Introduction
Slide 8
Networking Terminologies • LAN/MAN: – Scope is small (same room or building or Campus). – Owned by the same organization that owns the attached devices. – Data rates are typically much higher. – LANs usually employ a broadcast network approach. • No intermediate switching node • Only one station at a time can transmit packets
– Modern LAN technologies use packet/cell switching techniques. Dr. Indranil Sen Gupta
Data Commn. & Networking: Introduction
Slide 9
Contd. • WAN: – Usually covers a large geographic area. – Relies at least in parts on circuits provided by a common carrier. – Typically consists of a number of switching nodes. – Traditional technologies: • Circuit switching • Packet switching
– Recent technologies: • Frame relay • ATM Dr. Indranil Sen Gupta
Data Commn. & Networking: Introduction
Slide 10
Protocols and Protocol Architectures • A protocol is used for communication between entities in different systems. • Instead of a single module for performing communications, there is a structured set of modules that implement the communication functions. – Called the Protocol Architecture
Dr. Indranil Sen Gupta
Data Commn. & Networking: Introduction
Slide 11
TCP/IP Protocol Architecture • Most widely used inter-operable architecture. • Consists of a large number of protocols, called TCP/IP protocol suite. • Simplified layer model: – Physical: covers the physical interface between a host and the transmission medium. – Network Access: concerned with access to and routing data across a network for two end systems attached to the same network. Dr. Indranil Sen Gupta
Data Commn. & Networking: Introduction
Slide 12
Contd. – IP: used to provide routing function across multiple networks. • This protocol is implemented not only in the end systems but also in the routers.
– TCP: ensures that data is exchanged reliably. • Also known as host-to-host layer.
Dr. Indranil Sen Gupta
Data Commn. & Networking: Introduction
Slide 13
Figure 1.9 from the book by Stallings
Dr. Indranil Sen Gupta
Data Commn. & Networking: Introduction
Slide 14
The OSI Model • Developed by ISO as a model for a computer communication architecture, and as a framework for developing protocol standards. • Although more systematically designed, it ultimately lost its battle to TCP/IP, which has evolved in an ad-hoc manner. • Based on a seven layer model.
Dr. Indranil Sen Gupta
Data Commn. & Networking: Introduction
Slide 15
Seven Layer Model • Application: provides access to OSI environment for users. • Presentation: provides independence to the application processes from differences in data representation. • Session: establishes, manages and terminates connections (sessions) between co-operating applications. • Transport: provides reliable, transparent transfers of data between end points; provides end-to-end error recovery and flow control. • Network: provides upper layers with independence from the data transmission and switching technologies used to connect systems. • Data Link: provides for the reliable transfer of information across the physical link. • Physical: concerned with transmission of raw bit stream over some physical medium. Dr. Indranil Sen Gupta
