Notes-Lec 1 - Introductory Lecture
Notes-Lec 1 - Introductory Lecture
Notes-Lec 1 - Introductory Lecture
Introductory Lecture
Course Overview
Data Communication Networks and Open System
Standards
Data Transmission
Data Link Controls
Technologies of Local Area Networks and Wide Area
Networks
Communication Architecture and Protocols
Course Objectives
The aim of this course is to provide a unified
Course Objectives
Followings are the basic objectives :
To provide a conceptual foundation for the study
Text Books
Data and Computer Communications,
Course Website
http://web.uettaxila.edu.pk/cms/teCCNmsAU09/
Lecture Topics
Text's slides
chapter 1, chapter 2
chapter 3, chapter 4
chapter 5
chapter 6
chapter 7
Multiplexing
chapter 8
Spread Spectrum
chapter 9
chapter 10
10
chapter 14
11
LANs
chapter 15
12
chapter 16
13
Class Summary
Overview
Transmitter
Converts data into transmittable signals
Transmission System
Carries data
Receiver
Converts received signal into data
Destination
Takes incoming data
Networking
A
number of connections
Solution is a communications network
Wide Area Network (WAN)
Local Area Network (LAN)
...
Bus
Full mesh
function
Switch S can filter and forward!
Switch may forward multiple packets in parallel for
additional efficiency!
Star
Ring
Ring
Star
Tree
Internet
Circuit Switching
Dedicated communications path established for the
Packet Switching
Data sent out of sequence
Small chunks (packets) of data at a time
Packets passed from node to node between source
and destination
Used for terminal to computer and computer to
computer communications
Frame Relay
Packet switching systems have large overheads to
devices
Data rates much higher
Usually broadcast systems
Now some switched systems and ATM are being
introduced
LAN Configurations
Switched
Switched Ethernet
Wireless
Mobility
Ease of installation
Networking
Configuration
Further Reading
Stallings, W. [2003] Data and Computer
Semantics
Control information
Error handling
Timing
Speed matching
Sequencing
Protocol Architecture
Task of communication broken up into modules
For example file transfer could use three modules
File transfer application
Communication service module
Network access module
network
Sending computer provides address of destination
May invoke levels of service
Dependent on type of network used (LAN, packet
switched etc.)
Transport Layer
Reliable data exchange
Independent of network being used
Independent of application
Application Layer
Support for different user applications
e.g. e-mail, file transfer
Addressing Requirements
Two levels of addressing required
Each computer needs unique network address
Each application on a (multi-tasking) computer needs
layer
Transport layer may fragment user data
Each fragment has a transport header added
Destination SAP
Sequence number
Error detection code
This gives a transport protocol data unit
Network PDU
Adds network header
network address for destination computer
Facilities requests
OSI
Open Systems Interconnection
Developed by the International Organization for
Standardization (ISO)
Seven layers
A theoretical system delivered too late!
TCP/IP is the de facto standard
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
OSI Layers
Elements of Standardization
Protocol specification
Operates between the same layer on two systems
May involve different operating system
Protocol specification must be precise
Primitive Types
REQUEST
INDICATION
RESPONSE
CONFIRM
Mechanical
Electrical
Functional
Procedural
Data Link
Means of activating, maintaining and deactivating
a reliable link
Error detection and control
Higher layers may assume error free transmission
technology
Not needed on direct links
Transport
Exchange of data between end systems
Error free
In sequence
No losses
No duplicates
Quality of service
Use of a Relay
Physical Layer
Physical interface between data transmission device
Application Layer
Support for user applications
e.g. http, SMTP
OSI v TCP/IP
TCP
Usual transport layer is Transmission Control Protocol
Reliable connection
Connection
Temporary logical association between entities in different
systems
TCP PDU
Called TCP segment
Includes source and destination port (c.f. SAP)
Identify respective users (applications)
Connection refers to pair of ports
TCP tracks segments between entities on each connection
UDP
Alternative to TCP is User Datagram Protocol
Not guaranteed delivery
No preservation of sequence
No protection against duplication
Minimum overhead
Adds port addressing to IP
TCP/IP Concepts
Addressing level
Level in architecture at which entity is named
Unique address for each end system (computer) and
router
Network level address
IP or internet address (TCP/IP)
Network service access point or NSAP (OSI)
Process within the system
Port number (TCP/IP)
Service access point or SAP (OSI)
PDUs in TCP/IP
Required Reading
Stallings, W. [2003] Data and Computer
Q&A
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