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Shamim Al Mamun Assistant Professor
Institute of Information Technology Jahangirnagar University
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Contents
Data Communication Network
Internet & World Wide Web
Home Networking
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Data Communication Network
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• 1960’s – “How can we transmit bits across a
communication medium efficiently and reliably?”
• 1970’s – “How can we transmit packets across a communication medium efficiently and reliably?”
• 1980’s – “How can we provide communication services across a series of interconnected
networks?
Brief History of Computer Networks
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• 1990’s – “How can we provide high-speed, broadband communication services to support high-performance computing and multimedia applications across the globe?”
• 2000's – What do you think will dominate in the
next 10 years?
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A Communication Model
1 2 3 4 5 6
Input Information
m
Input data g or signal
g(t)
Transmitted signal
s(t)
Received signal
r(t)
Output data g’
or signal g’(t) ’
Output Information
m’
Transmission medium Transmitter
Input
Device Output
Device Receiver
Source System Destination System
Sender Receiver
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Common Communication Tasks
Data encoding: the process of transforming input data or signals into signals that can be transmitted
Signal generation: generating appropriate electro-
magnetic signals to be transmitted over a transmission medium
Synchronization: timing of signals between the
transmitter and receiver ; when a signal begins and when
it ends; duration of each signal
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Error detection and correction: ensuring that transmission errors are detected and corrected Flow control: ensuring that the source does not
overwhelm the destination by sending data faster than the receiver can handle
Multiplexing: a technique used to make more efficient
use of a transmission facility. This technique is used at
different levels of communication
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Addressing: indicating the identity of the intended destination
Routing: selecting appropriate paths for data being transmitted
Message formatting: conforming to the appropriate format of the message to be exchanged
Security: ensuring secure message transmission
Systems management: configuring the system, monitoring
its status, reacting to failures and overloads, and planning
for future growth
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Communication Network
A communication network is a collection of devices connected by some communications media
• Example devices are:
– mainframes, minicomputers, supercomputers – workstations, personal computers
– printers, disk servers, robots – X-terminals
– Gateways, switches, routers, bridges – Cellular phone, Pager, TRS
– Refrigerator, Television, Video Tape Recorder
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• Communications Media
– twisted pairs – coaxial cables
– line-of-sight transmission: lasers, infra-red, microwave, radio
– satellite links – fiber optics – Power line
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Network Structures
Point-to-Point Networks
• each communication line connects a pair of nodes
• a packet (or message) is transmitted from one node to another
• intermediate nodes, in general, receive and store entire packet and then forward to the next node
• also called “store-and-forward” or “pack-switched”
• some topologies: star, ring, tree
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Broadcast Networks
• have a single communication line shared by all computers on the network
• packets sent by a host are received by all computers
• some topologies: bus, satellite, radio
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Types of Communication Networks
• Local Area Networks (LANs)
– < a few km
– high data transmission rate (at least several Mbps) – ownership usually by a single organization
– e. g., Ethernet, IBM Token Ring, Token Bus, FDDI, Fast Ethernet, ATM, Gigabit Ethernet
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POSTECH LAN (1998.6)
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POSTECH LAN (1999. 3)
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• Metropolitan Area Networks (MANs)
– up to 50 km
– fibre optics is a popular technology for MANs – may be private or public
– may involve a number of organizations
– e.g., cable TV networks (CATV), ATM networks
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• Wide Area Networks (WANs)
– a few km to thousands of km
– point-to-point networks (also called long-haul networks) – lower data transmission rate than LANs
– fiber optics is a popular technology for MANs ownership usually by more than a single organization
– e.g., ARPANET, MILNET (US military), CA*NET, NSFNET, KREONET, BoraNet, KORNET, INET, Internet
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Internet in Korea (1995.5)
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Internet in Korea (1999.6)
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Growth of Internet Users in Korea
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Growth of Internet Hosts in Korea
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Computer Communication Architecture
• Computer Communication – the exchange of
information between computers for the purpose of cooperative action
• Computer Network – a collection of computers
interconnected via a communication network
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• Protocol – agreement required between the communication entities and consists of three components:
Syntax: data format and signal levels
Semantics: control information for coordination and error handling
Timing: speed matching and sequencing
• Communications Architecture – a structured set of
modules that implements the communication function
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ISO-OSI Reference Model
• International Standards Organization (ISO) – Open Systems Interconnection (OSI) Reference model is a framework for connecting computers on a network
• Motivation?
– to reduce the complexity of networking software
– as a step towards international standardization of the various protocols
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• The main principles applied to the OSI layered architecture are
– each layer represents a layer of abstraction, – each performs a set of well-defined functions,
– implementation of a layer should not affect adjacent layers, and inter-layer communication should be minimized
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Application Presentation
Session Transport
Network Data Link
Physical OSI Stack
Application Presentation
Session Transport
Network Data Link
Physical OSI Stack
Application Presentation
Session Transport
Network Data Link
Physical
OSI Stack
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Functions of the OSI Layers
1. Physical layer – responsible for the electro- mechanical interface to the communications media
2. Data link layer – responsible for transmission,
framing and error control over a single communications link.
3. Network layer – responsible for data transfer across
the network, independent of both the media comprising
the underlying subnetworks and the topology of those
subnetworks.
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4
. Transport layer – responsible for reliability and
multiplexing of data transfer across the network (over and above that provided by the network layer) to the level required by the application.
5. Session layer – responsible for establishing,, and managing sessions between cooperating applications.
6. Presentation layer – responsible for providing independence to the application process from differences in data representation (syntax).
7. Application layer – ultimately responsible for
managing the communications between applications.
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How Communication Takes Place Between the Layers
• communication takes place between peer entities.
• a layer provides services to the layer above it.
• services are available at SAPs (Service Access Points)
– analogous to telephone numbers and street addresses
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Relation Between Layers at an Interface
ICI SDU
ICI SDU
IDU
SAP
SDU Header
Layer N Interface Layer N + 1
Layer N entities
exchange N- PDUs
in their layer N Protocol
SAP = Service Access Point IDU = Interface Data Unit
SDU = Service Data Unit PDU = Protocol Data Unit
ICI = Interface Control Information
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• On the sending side:
– a layer receives a PDU (Protocol Data Unit) from the layer above it, with some ICI (Interface Control Information) (such as address, data size, etc.).
– the layer ads some PCI (Protocol control Information) to the APDU and passes the enlarged PDU to the layer below along with more ICI.
– A layer may also fragment a PDU into several smaller pieces to be passed separately to the layer below (in this case, the peer entity at the receiving end will reassemble the fragments).
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• At the receiving end:
– a layer receives a PDU from the layer below.
– The layer strips off the PCI added by its peer, and passes the PDU to the layer above it.
– If the sending layer fragmented a PDU, its peer is responsible for reassembling it before passing it up.
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Other Communication Models
The Anarchistic Network Model
• have been used mostly in PCs The TCP/IP Model
• only 5 layers exist
• used mostly in Internet network applications
35 Application
Operatin g System
Controller Physical The Anarchistic Network Model
Application Presentation
Session Transport
Network Data Link Physical The OSI Model
Application
Transport Network Data Link
Physical The TCP/IP Model
the network
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Communication Service Types
• Connection-oriented service
– modeled after the telephone system
– must establish a connection before use, and terminates the connection when finished.
– FIFO guaranteed.
– the path from the sender to receiver is fixed.
– resources are pre-allocated at setup time
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• Connectionless service
– modeled after the postal system
– no connection required, but instead full addressing required in each message
– FIFO not guaranteed.
– the path is not fixed
– resources are dynamically allocated
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Standards Organizations
ITU-T (International Telecommunication Union -
Telecommunications Sector) - formerly CCITT (International Telegraph and Telephone Consultative Committee), a
committee within ITU, a United Nations agency, responsible for X.25, X.21, X.400, X.500, X.700, X.900, etc.
ISO (International Standards Organization): ISO 8073 (connection-oriented transport protocol)
ANSI (American National Standard Institute)
IEEE (Inst. of Electrical and Electronics Engineers): IEEE 802
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IETF (Internet Engineering Task Force): TCP/IP, FTP, SNMP W3C (World-Wide Web Consortium): HTTP, HTML, XML ATMF (ATM Forum) - ATM related standards
TMF (TeleManagement Forum) - formerly known as NMF,
Network Management Forum
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Internet and World Wide Web
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History of the Internet
1969 - Researchers at four US campuses create the first hosts of the ARPANET
1971 - The ARPANET grows to 23 hosts connecting universities and research centers 1973 - The ARPANET goes international with connections to England and Norway 1982 - The term "Internet" is used for the first time and TCP/IP is created
1992 - Internet Society is chartered. World-Wide Web released by CERN.
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Definitions
• A network of networks
• Based on TCP/IP (Transmission Control Protocol/Internet Protocol)
• A variety of services and tools
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Network of networks
a group of two or more networks that are :
• interconnected physically
• capable of communicating and sharing data with each other
• able to act together as a single network
• virtually all of today’s computers are connected via
Internet
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Based on TCP/IP
TCP/IP enables the different types of machines on separate networks to communicate and exchange information.
TCP/IP is
• A suite of protocols
• Rules for sending and receiving data across networks
• Addressing
• Management and verification
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Variety of services or tools
The Internet offer access to data, graphics, sound, software, text, and people through a variety of services and tools for communication and data exchange
• Usenet
• FTP
• Gopher
• Telnet
• World Wide Web
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World Wide Web
• A way to provide and access information resources on the Internet
• Using Web Browser & Web Server
• Based on HTML and HTTP
• Multimedia
– Hypertext "links" can lead to other documents, sounds,
images, databases (like library catalogs), e-mail addresses, etc.
• Non-Linear
– There is no top, there is no bottom. Non-linear means you do not have to follow a hierarchical path to information resources.
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Web Browser
• a piece of software that acts as an interface between the user and the Internet, specifically the World Wide Web
• The browser acts on behalf of the user. The browser:
– contacts a web server and sends a request for information – receives the information and then displays it on the user's
computer
• The browser can be graphical or text-based and can make the Internet easier to use and more intuitive
• The helper applications are automatically invoked by the browser when a user selects a link to a resource that
requires them
• A Web browser can be used on most of computers
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Web Server
• Also known as HTTP Server or HTTP Daemon
• The repository of web pages of which types are HTML and any application data with MIME type
• Listens for HTTP requests from the web browsers, serves those requests
• Designed to communicate with web browsers using HTTP protocol
• Typically runs on general purpose computer
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HTML
• consists of standardized codes,or "tags", that are used to define the structure of information on a web page
• defines several aspects of a web page including heading levels, bold, italics, images, paragraph breaks and
hypertext links to other resources.
• a sub-language of SGML (Standard Generalized
Markup Language) that defines and standardizes the structure of documents.
• standardized and portable: A document that has been
prepared using HTML can be viewed using a variety of
web browsers, such as Netscape and Lynx
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HTTP
• the set of rules, or protocol, that governs the transfer of hypertext between two or more computers.
• Based on Client/Server paradigm
• Convey variety of Internet resources: HTML documents, text files, graphics, animation and sound
• HTTP also provides access to other Internet protocols, among them:
– File Transfer Protocol (FTP)
– Simple Mail Transfer Protocol (SMTP) – Network News Transfer Protocol (NNTP) – etc.
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URL
• a standardized addressing scheme for Internet resources
• used to link documents on the Internet
• the browser knows where to go to get the document
• basic format of an URL
type-of-resource:// domain.address:port/path/filename
– ftp://ftp.postech.ac.kr/pub/welcome.txt – file:///C|/My Documents/resume.htm – news:han.protocol.http
– telnet://vision.postech.ac.kr
– http://www.postech.ac.kr/index.html
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Home Networking
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Definition
the collection of technologies and services that make it possible to connect
• PCs
• Network devices
• Appliances
• Security equipment
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Why now?
Building “Internet” into consumer products is now possible
• Standardization has occurred
• Costs are low
Low-cost, high-speed LAN and routers
• Ethernet, IEEE 1394, Phone Wire, PLC, RF, etc.
• Video rate networks - IEEE 1394,Gigabit Ethernet
Modem and broadband networking are becoming ubiquitous
Golden age of networking
Golden age of networking
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Technology Enablers
ADSL and HFC (cable) networks
• Enable broadband Internet to the home
LANs, power line carrier, phone line networks, and wireless
• Enable ubiquitous connectivity
Internet connection sharing
• Brings the Internet to everything in the home
The communications software infrastructure has been determined:
The Web and TCP/IP
The Web and TCP/IP
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Analogous History
• Single to multiple cars per family
• One to multiple phones per household
• Multiple phone lines per house
• One to multiple TVs per house
MegaTrend: From one Internet MegaTrend: From one Internet
device per home to
device per home to MANY MANY
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Roles for Home Networking
Data
• Extension of current use of Internet by PDAs, tablets, multiple PCs
Communications
• Telephony, videophone, chat, conferencing
Entertainment
• Games, TV, high-fidelity audio
Control
• Lights, HVAC, security, appliances
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Connecting Everything
Network Network camera camera
Communications Communications
and control and control
HomeRF HomeRF
HubHub
Power line Power line
network network
HomePNA HomePNA
Phone line network Phone line network
Public networks Public networks PSTN, Internet PSTN, Internet
Printer Printer
Camera
Camera ScannerScanner
Web Web phone phone
IEEE 1394 IEEE 1394
Entertainment Entertainment
Center Center
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Challenges for deployment of home network
Ease of installation
• There are no Net admins at home…
Network configuration has to be automatic
• There are no Net admins at home…
Network health and recovery
• There are no Net admins at home…
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Home Network Architecture
End to end End to end broadband broadband
Public networks Public networks PSTN, Internet PSTN, Internet
Camera
Camera PrinterPrinter
New media support New media support
Internet Internet
Connection Connection Sharing
Sharing
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Architecture for The Future
Great standards exist today
• IETF: TCP/IP, DNS, DHCP, HTTP, SSL, LDAP, IPSEC
• W3C: HTML, XML
Great services exist today
• Today: eCommerce, search
• Early Stages: Internet audio/video,
IP Telephony - much like early 1950s TV
• Billions of Web hits served daily
Leveraging Web Leveraging Web
technologies technologies
Internet exists and it works
Internet exists and it works
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TCP/IP and Web is the software infrastructure
Web is evolving
• HTTP v1.1 for performance improvements
• XML extends Web for software applications
– “Pages” can now be simply data
– Internet Explorer 5.0 has XML support
Easy to wrap existing programs/tools/systems in Web
• Programming language neutral
• Contents neutral
• Operating system neutral
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Web for “Devices”
TCP/IP stack
TCP/IP stack 30 ~ 90K bytes code 30 ~ 90K bytes code
30 ~ 80K gates on silicon 30 ~ 80K gates on silicon
Embedded web Embedded web
server
server 20 ~ 80K bytes code 20 ~ 80K bytes code
30 ~ 90K gates on silicon 30 ~ 90K gates on silicon
Ethernet, 1394 or Ethernet, 1394 or PPP/async driver
PPP/async driver Device specific size Device specific size
Device or service Device or service
specific code
specific code Application specific size Application specific size
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Example Web Devices
Refrigerator PC: Sharewave
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Example Web Devices
Internet-on-a-chip design from Toshiba Semiconductor
• Features:
– Network Stack - TCP, IP, UDP and PPP
– General Sockets - 4 - Email - SMTP, POP3 and MIME – Web - HTTPv1.0 and HTMLv3.2 (text only)
– Japanese and English character support
• Interfaces:
– CPU Interface (Generic 80x86 CPU Interface) – SRAM Interface
– Physical Layer Interface (RS232C & parallel port) – Decoder Interface
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Example Web device
Interactive TV from Spyglass
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Example Web devices
Internet Router from POSTECH
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