Computer Communication NetworksVII Semester – CoreSubject Code: 06EC71 : Computer Communication NetworksVII Semester – CoreSubject Code: 06EC71 By
Department of E&C,
R.N.S.I.T Chapter 1Data Communications and Networks Overview : Chapter 1Data Communications and Networks Overview Introduction : Introduction Our goal:
Get context, overview, “feel” of networking
More depth, detail later in course
use Internet as example mostly Slide 4: Communications – activity associated with distributing or exchanging information
Telecommunications – technology of communications at a distance that permits information to be created any where and used everywhere with little delay
Today, it involves
Data: digital and analog
Voice: spoken word
Video: telelcommunication imaging Communication Services & Applications : Communication Services & Applications A communication service enables the exchange of information between users at different locations.
Communication services & applications are everywhere. E-mail E-mail
server Exchange of text messages via servers Communication Services & Applications : Communication Services & Applications Web Browsing Web server Retrieval of information from web servers Communication Services & Applications : Communication Services & Applications Instant Messaging Direct exchange of text messages Communication Services & Applications : Communication Services & Applications Telephone Real-time bidirectional voice exchange Communication Services & Applications : Communication Services & Applications Cell phone Real-time voice exchange with mobile users Communication Services & Applications : Communication Services & Applications Short Message Service Fast delivery of short text messages What is a communication network? : What is a communication network? The equipment (hardware & software) and facilities that provide the basic communication service
Virtually invisible to the user; Usually represented by a cloud Equipment
Routers, servers, switches, multiplexers, hubs, modems, … Facilities
Copper wires, coaxial cables, optical fiber
Ducts, conduits, telephone poles … Definition……… : Definition……… Two or more than two computer systems connected by means of a communication medium like a cable is termed as a Network.
Computer Network is a communication system, which links computers and their resources. Why do we need Networking? : Why do we need Networking? Sharing of data and resources
Distributing computation among nodes
Communicating with Remote I/O devices
To share data/file access.
Personal Communication (Chat, E-mail) Why do we need networks?-continued.. : Why do we need networks?-continued.. Direct point-to-point communication is not always possible/practical/efficient:
Communicating entities can be too far apart for a single link
A large set of communicating entities (e.g. telephones) would need impractically large number of connections
(full connectivity for N nodes needs N (N – 1) / 2 links)
Not all links would be needed all the time!
a communication network BENEFITS OF A NETWORK : BENEFITS OF A NETWORK Following are the benefits of networking which help to increase the productivity:
Hard Disk Sharing
Easy Back-Up Management
Centralized Administration and Support Many other examples! : Many other examples! Peer-to-peer applications
Searching for Extraterrestrial Intelligence (SETI)
Audio & video streaming
Text messaging in PDAs, cell phones (SMS)
Voice-over-Internet How are communication networks designed and operated? Basic Communication Network Architecture : Basic Communication Network Architecture Network architecture: the plan that specifies how the network is built and operated
Architecture is driven by the network services
Overall communication process is complex
Network architecture partitions overall communication process into separate functional areas called layers Network Architecture Evolution : Network Architecture Evolution Telegraph
networks Internet, Optical
networks Information transfer
per second Next Generation Internet ? Network Architecture Evolution : Network Architecture Evolution Telegraph Networks
Message switching & digital transmission
Analog transmission → digital transmission
Packet switching & computer applications
Multiservice packet switching network A Communications Model : A Communications Model Source
generates data to be transmitted
Converts data into transmittable signals
Converts received signal into data
Takes incoming data Communications Tasks : Communications Tasks Simplified Communications Model - Diagram : Simplified Communications Model - Diagram Slide 23: Data Communication System Components Slide 24: Network Transmission Medium Open air
radio, microwaves, satellites, infrared
noise signals, collision
clear signals, low power and high rate (Gbps)
Lower cost interfaces
Bi-directional What’s a protocol? : What’s a protocol? human protocols:
“what’s the time?”
“I have a question”
… specific msgs sent
… specific actions taken when msgs received, or other events network protocols:
machines rather than humans
all communication activity in Internet governed by protocols-In general a set of rules governing the process Protocols define format, order of msgs sent and received among network entities, and actions taken on msg transmission, receipt What’s a protocol? : What’s a protocol? a human protocol and a computer network protocol: Hi Hi TCP connection
req Key Elements of a Protocol : Key Elements of a Protocol Syntax
Sequencing Slide 28: Few Basic Concepts Line Configuration
Categories of Networks
Internetworks Slide 30: Point-to-Point Line Configuration Dedicated link between two devices
Entire capacity is reserved for transmission between those two devices Slide 31: Point-to-Point Line Configuration Slide 32: Point-to-Point Line Configuration Slide 33: Multipoint Line Configuration More than two specific devices share a single link
A spatially or time shared connection Networking : Networking Point to point communication not usually practical
Devices are too far apart
Large set of devices would need impractical number of connections
Solution is a communications network
Wide Area Network (WAN)
Local Area Network (LAN) Slide 35: The Physical layout of a network is Topology Mesh Network Topology : Mesh Network Topology Type I - Nodes are arranged in grids
each node can talk to its neighbors directly
non-neighbor nodes needs store-and-forward for communication Slide 37: Type II - Mesh Topology Practical Example: Connection of telephone regional offices Advantages : Advantages Use of dedicated links guarantees that each connection carries its own data load
Robust – one faulty link doesn't incapacitate the whole system
Privacy & Security guaranteed
Fault identification &isolation is easy Disadvantages : Disadvantages Large amount of cabling required
More I/O ports required
Installation & reconnection are difficult
Huge wiring bulk
Very expensive Slide 40: Star Network Topology One node at the center as the master node
Other nodes linked to the master as slaves
slaves communicate via master
easy to arbitrate among slaves (master decides)
not scalable (the master is the bottleneck)
normally used for small networks or those that require predictable performance
master failure shuts down the whole net
Example: Ethernet, DSL Advantages : Advantages Less Expensive
Easy to install & reconfigure (each device needs only one link to connect it to any number of others)
Additions, moves & deletions involve only one connection
Robust – (one link failure doesn’t affect the others)
Easy fault identification & isolation Disadvantages : Disadvantages The whole network is dependant on one single point, the hub /master
Cabling requirement is high Slide 43: Star Topology Slide 44: Tree Topology Slide 45: Bus Network Topology Every nodes tap into a common medium
Signals may collide with each other
need to arbitrate who will get the bus
capable of broadcasting message (one send & many listen)
the common medium is the bottleneck
single node failure causes no network failure
the medium failure brings down the network
Example: (10BASE2, 10BASE5) Ethernet Slide 46: Bus Topology Ring Network Topology : Ring Network Topology Nodes are arranged in a ring
One node receives from its predecessor & sends to its successor
arbitrate who can access the ring
messages forwarded by each node
sender deletes its messages from the ring
the common ring is the single point of failure (complicated connectors needed)
Unidirectional traffic Slide 48: Ring Topology Hybrid Network Topology : Hybrid Network Topology No restrictions on how to link the nodes
Topology can adapt to individual organization needs Slide 50: Hybrid Topology Slide 52: Simplex Ex: Keyboards and traditional monitors Slide 53: Half-Duplex Ex: Walkie-talkies & Citizen band radios Slide 54: Full-Duplex Ex: Telephone network Network Classification : Network Classification Classification of interconnected processors by scale. Slide 57: Network Types by Scope WAN
wide area network
cross large span of space (continental)
typically heterogeneous and low speed
regional scope (city-wide)
local area network
limited scope (a couple of buildings)
typically homogeneous & high speed
example: Ethernet & Token ring Local Area Networks : Local Area Networks Local area networks (LANs) are privately-owned networks within a single building or campus of up to a few kilometers in size.
LANs are distinguished by three characteristics:
(Restricted in) Size
Transmission technology: 10 Mbps to 10 Gbps (1 Mbps = 1,000,000 bits/sec, 1 Gbps = 1,000,000,000 bits/sec).
Topology: bus and ring Local Area Networks : Local Area Networks Two broadcast networks
(a) Bus: Ethernet – IEEE 802.3
(b) Ring: IEEE 802.5, FDDI Slide 60: Local Area Network Slide 61: Local Area Network LAN Configurations : LAN Configurations Switched
May be single or multiple switches
Ease of installation Metropolitan Area Networks : Metropolitan Area Networks A metropolitan Area Networks (MAN) is a network that interconnects users with computer resources in a geographic area or region such as a city.
Wireless: IEEE 802.16 Metropolitan Area Networks : Metropolitan Area Networks MAN
Middle ground between LAN and WAN
Private or public network
Large area Metropolitan Area Networks : Metropolitan Area Networks A metropolitan area network based on cable TV. Slide 66: Metropolitan Area Network Wide Area Networks : Wide Area Networks A wide area network (WAN) spans a large geographical area, often a country and continent.
It contains a collection of machines (hosts).
The hosts are connected by a communication subnet.
The subnet consists of two components:
Switching elements: router Wide Area Networks : Wide Area Networks Relation between hosts on LANs and the subnet. Wide Area Networks : Wide Area Networks Large geographical area
Crossing public rights of way
Rely in part on common carrier circuits
Asynchronous Transfer Mode (ATM) Slide 70: Wide Area Network Internetworks : Internetworks Different networks are connected by means of machines called gateways.
A collection of interconnected networks is called an internetwork or internet.
A common form of internet is a collection of LANs connected by a WAN. Slide 72: Internetwork
(Internet) NetworkingConfiguration : NetworkingConfiguration What’s the Internet: “nuts and bolts” view : What’s the Internet: “nuts and bolts” view millions of connected computing devices: hosts, end-systems
PCs workstations, servers
PDAs phones, toasters
running network apps
fiber, copper, radio, satellite
transmission rate = bandwidth
routers: forward packets (chunks of data) “Cool” internet appliances : “Cool” internet appliances World’s smallest web server
http://www-ccs.cs.umass.edu/~shri/iPic.html IP picture frame
http://www.ceiva.com/ Web-enabled toaster+weather forecaster What’s the Internet: “nuts and bolts” view : What’s the Internet: “nuts and bolts” view protocols control sending, receiving of msgs
e.g., TCP, IP, HTTP, FTP, PPP
Internet: “network of networks”
public Internet versus private intranet
RFC: Request for comments
IETF: Internet Engineering Task Force local ISP company
network regional ISP router workstation server mobile What’s the Internet: a service view : What’s the Internet: a service view communication infrastructure enables distributed applications:
Web, email, games, e-commerce, database., voting, file (MP3) sharing
communication services provided to apps:
connection-oriented cyberspace [Gibson]:
“a consensual hallucination experienced daily by billions of operators, in every nation, ...." Frame Relay : Frame Relay Packet switching systems have large overheads to compensate for errors
Modern systems are more reliable
Errors can be caught in end system
Most overhead for error control is stripped out Asynchronous Transfer Mode : Asynchronous Transfer Mode ATM
Evolution of frame relay
Little overhead for error control
Fixed packet (called cell) length
Anything from 10Mbps to Gbps
Constant data rate using packet switching technique Wireless Communication : Wireless Communication Wireless communication is not a new idea.
Native American smoke signal
Chinese Beacon fire
Wireless telegraph using Morse Code
Modern digital wireless systems have better performance, but the basic idea is the same. Wireless Networks : Wireless Networks Categories of wireless networks:
Wireless WANs System Interconnection : System Interconnection System interconnection is all about interconnecting the components of a computer using short-range radio.
Some companies got together to design a short-range wireless network called Bluetooth to these components.
Bluetooth allows digital cameras, headsets, scanners, and other devices to connect to a computer in a short range. Bluetooth Standard : Bluetooth Standard The Bluetooth document is adopted by IEEE (Institute of Electrical and Electronics Engineers) 802.15 as a basis for wireless personal area networks.
Work at 2.4 GHz
Transfer up to 2 Mbps
10 meters range Wireless Networks : Wireless Networks (a) Bluetooth configuration
(b) Wireless LAN Wireless LANS : Wireless LANS The wireless local area networks (LANs) are systems in which every computer has a radio modem and antenna with which it can communicate with other systems.
Wireless LANs are common in small offices and homes.
There is a standard for wireless LANs, called IEEE 802.11. Wireless WANS : Wireless WANS The wireless wide area networks (WANs) are systems used in the wide area.
The radio network used for cellular telephones is an example of a low-bandwidth (low transfer rate) wireless system.
First generation: analog for voice
Second generation: digital for voice
Third generation: digital for voice and data Wireless Networks : Wireless Networks (a) Individual mobile computers
(b) A flying LAN Wireless WANS : Wireless WANS High-bandwidth wide area wireless networks are also being developed.
A standard for it, called IEEE 802.16, has also been developed.
Work at 10-to-66 GHz
Transfer up to 155 Mbps
30 miles range Home Network Categories : Home Network Categories Computers (desktop PC, PDA, shared peripherals)
Entertainment (TV, DVD, VCR, camera, stereo, MP3)
Telecomm (telephone, cell phone, intercom, fax)
Appliances (microwave, fridge, clock, furnace, air cooler)
Telemetry (utility meter, burglar alarm, babycam). Home Network Properties : Home Network Properties The network and devices have to be easy to install.
The network and devices have to be foolproof in operation.
Low price is essential for success.
The main application is likely to involve multimedia.
It must be possible to start out with one or two devices and expand the reach of the network gradually.
Security and reliability will be very important. A closer look at network structure : A closer look at network structure network edge: applications and hosts
network of networks
access networks, physical media: communication links Circuit Switching : Circuit Switching Dedicated communications path established for the duration of the conversation
e.g. telephone network Packet Switching : 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 Data Communication Frameworks : Data Communication Frameworks Two major data communication frameworks have been developed to help ensure that networks meet business and communication requirements:
Open Systems Interconnection (OSI) reference model developed by the International Standards Organization (ISO)
Transmission Control Protocol/Internet Protocol (TCP/IP) suite Transmission Speeds : Transmission Speeds Important Standard-Setting Organizations : Important Standard-Setting Organizations Online System Requirements : Online System Requirements PERFORMANCE
Flexibility Online Systems Requirements Continued : Online Systems Requirements Continued Availability
Mean time between failure (MTBF)
Mean time to repair (MTTR)
Security Business Data Communication Applications : Business Data Communication Applications Major data communication applications include:
Knowledge management systems
E-commerce and e-business applications
Wireless applications Groupware Applications : Groupware Applications Group calendar systems
Electronic filing cabinets
Project management software
Group support systems Electronic meeting and videoconferencing systems
Document management systems (image processing systems) Other Data Communication Applications : Other Data Communication Applications Batch applications
Data entry applications
Inquiry/response applications Interactive applications
Combined applications Application Service Providers : Application Service Providers Many businesses have turned to third-party services for some or all of their business and data communications applications
Application service providers (ASPs) are third-party organizations that manage and distribute software and services to other companies over the Web
Many ASPs specialize in integrated e-commerce and e-business applications Business Data Communications Issues : Business Data Communications Issues Major data communications issues include:
Privacy and security Services versus Throughput Rates : Services versus Throughput Rates