Unit 1 Introduction to computer network
-
Upload
chintan-patel -
Category
Technology
-
view
1.058 -
download
1
description
Transcript of Unit 1 Introduction to computer network
![Page 2: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/2.jpg)
COMPUTER NETWORK
TEACHING SCHEME
Theory : 4 lecture / weekPractical : 1 lab / week
Evaluation Scheme
University exam (theory) : 70Mid sem exam (theory) : 30Internal : 50
Books
1 Computer network, by Tanenbaum , Pearson.2 Introduction to data communication and
networking by Forouzan,TMH.
![Page 3: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/3.jpg)
Syllabus
• Introduction :
• The Physical Layer :
• The data link layer
• The medium access control sublayer
• The network layer
• The transport layer
• The application layer
![Page 4: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/4.jpg)
Introduction
• Use of computer network• Network hardware• Network software• OSI Model(Open system interconnect)• TCP/IP Model• Comparison • The internet• X.25 Frame relay • ATM(Asynchronus transfer mode)• ETHERNET• WIRELESS LAN : 802.11
![Page 5: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/5.jpg)
Computer NetworkNetworking is the linking two or more computing devices together for the purpose of sharing data. Networks are built with a mix of computer hardware and computer software.
![Page 6: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/6.jpg)
Use of computer network
• Business Application• Home application• Mobile usage• Social issues
![Page 7: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/7.jpg)
Business Application
• Resource sharing Make all programs , equipments , and specially data available
to anyone on the network without regards to the physical location of the resource and user.
• Client server modal• Communication medium• E commerce
![Page 8: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/8.jpg)
Client – server model
Small network with 2 clients and one server
![Page 9: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/9.jpg)
Client : Simple user computer in networkServer : Powerful Computer on which data is storedRequest : Message send by client to serverReply : Reply by server to client based on request
Client – server model
![Page 10: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/10.jpg)
Communication medium
• Email • E commerce
Home applications• Access to remote information• Person to person communication• Interactive entertainment• Electronic commerce
![Page 11: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/11.jpg)
Difference between Client-server model and person to person communication
In person to person communication , There is no fix client and server.
Best example : Watsapp , Wechat for mobile and yahoo group chat or google group chat, mobile conference
![Page 12: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/12.jpg)
Network Hardware
• Broadcasting• Multicasting• Point to point network
• Local Area Network• Metropolitan Area network• Wide area network
![Page 13: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/13.jpg)
Local Area Network
• Within single building or campus• Used to connect personal computer and work
stations.• Traditional LAN runs at 10 mbps to 100 mbps.• Broad cast LAN.
Ring and Bus
![Page 14: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/14.jpg)
Metropolitan Area Network
• Communication Subnet• Transmission Lines• Switching element(Routers)
Wide area network
• Covers city….• Cable television network
![Page 15: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/15.jpg)
• Relation between hosts on LANs and the subnet.
• A stream of packets from sender to receiver.
![Page 16: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/16.jpg)
Wireless Networks• System interconnecting.
Wireless components of computer, Keyboard , mouse Connect using bluetooth
• Wireless LANs. IEEE 802.11 Standard
• Wireless WANs.
• (a) Bluetooth configuration• (b) Wireless LAN
![Page 17: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/17.jpg)
Network software
• Protocol Hierarchy• Design issues of layer• Connection-oriented and Connection
less services
![Page 18: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/18.jpg)
Protocol hierarchy
• Layers, protocols, and interfaces.
![Page 19: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/19.jpg)
• Physical medium• Interface• Header• Design Issues
Error Control Flow control Routing Multiplexing and De multiplexing
![Page 20: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/20.jpg)
Connection Oriented and Connection less service
• Connection oriented service• After telephone system
Establish a connection Use the connection Releases the connection
• Connection less service• After postal system
Message have full destination address Routed through system and reached to destination
• Quality of service Reliable service (no packet loss)
With acknowledgement
• Request reply service used in client server model
![Page 21: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/21.jpg)
• Service : Set of operations that a layer provides to the layer above it. What operations to be performed.
• Protocol : Set of rules governing the formats and meaning of packet or messages.
![Page 22: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/22.jpg)
• GOOGLE FIBER.• GOOGLE BALLON
CHINTAN PATEL(ASSISTANT PROFESSOR)
![Page 23: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/23.jpg)
REFERENCE MODELS• The OSI Reference Model
• The TCP/IP Reference Model
• A comparison of the OSI And TCP/IP
Reference model
CHINTAN PATEL(ASSISTANT PROFESSOR)
![Page 24: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/24.jpg)
• OSI Model is very important as well as protocol discussed are also very important.
• TCP / IP model it self is not much of use but protocols inside are very important.
CHINTAN PATEL(ASSISTANT PROFESSOR)
![Page 25: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/25.jpg)
The OSI Reference model• Proposed by ISO(International Standard Organization).• Called As ISO OSI Reference model. (Open System Inter connections).• Why open system inter connection?• Open system is a set of protocols that allows any two different system to
communicate regardless of their underlying architecture.• Purpose of OSI Model is to show how to facilitate communication
between different system without changing in their underling hardware.
CHINTAN PATEL(ASSISTANT PROFESSOR)
![Page 26: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/26.jpg)
Principles applied to layers
• Where different abstraction is needed• Each layer should perform well defined
functions.• Must follow internationally standardized
protocol.• Information flow should be minimum.
EACH LAYER HAS SEPARATE INTERNATIONAL STANDARD
CHINTAN PATEL(ASSISTANT PROFESSOR)
![Page 27: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/27.jpg)
CHINTAN PATEL(ASSISTANT PROFESSOR)
![Page 28: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/28.jpg)
Peer-to-peer process• Layer x on one machine directly communicate with Layer X on
another m/c with some series of rules called protocols.
![Page 29: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/29.jpg)
The physical Layer• Transmitting raw bits over communication channel.• Representation of Bits.• Defines transmission mode : • Defines encoding(0 and 1 changed in signal)• Defines the types of transmission mediums• Defines topology configuration.• Decides data rate.• Purely hardware layer.
CHINTAN PATEL(ASSISTANT PROFESSOR)
![Page 30: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/30.jpg)
Data link layer• Converts physical layer data into error free data for network layer• framing• Transmit the frames.• Physical addressing (provide sender and receiver mac address in header)• Traffic regulation mechanism• Flow control• Error control• MAC Sub layer : To control access to the shared channel .
CHINTAN PATEL(ASSISTANT PROFESSOR)
![Page 31: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/31.jpg)
Hop to Hop delivery
To send data from A to F, First Data link layer at A will send data to the Data link layer B.GATE: Data link layer is responsible for Hop to Hop delivery.
CHINTAN PATEL(ASSISTANT PROFESSOR)
![Page 32: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/32.jpg)
The Network Layer• Responsible for the delivery of individual packet from one host to another host• Routing : (How packets are routed from source to destination).• Logical Addressing.• Congestion control.• Quality of service provided(Delay, transit time , Jitter).• Solves problems like:
Address used by 2nd network may be different by 1st
Packet may be too large. Protocol may differ.
CHINTAN PATEL(ASSISTANT PROFESSOR)
![Page 33: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/33.jpg)
Source to Destination delivery
• GATE : Network layer is responsible for End to End or Source to Destination delivery.
Router makes the decision based on destination.
CHINTAN PATEL(ASSISTANT PROFESSOR)
![Page 34: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/34.jpg)
The Transport Layer• Segmentation and Reassembly• Service point Addressing
Delivery should not be from one computer to the next but it should also be from specific running process on computer to specific running process on another.
Adds service point address or Port number• End to End Error control and flow control.• GATE : Error correction is usually achieved through Retransmission.• GATE: Responsible for Process to Process delivery
CHINTAN PATEL(ASSISTANT PROFESSOR)
![Page 35: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/35.jpg)
The Session layer• Allow user on different machine to establish session between them.• Dialog Control(Keeping track of whose turn is to transmit).• Token management(Preventing two parties from the attempting same critical operations
at same time).• Synchronization (Check pointing long transmissions to allow them to continue from
where they were after crash ). If system is sending file of 2000 pages. its advisable to insert check point after every
100 pages. In this case if crash happens at 523 page no. than retransmission of 501 to 523.not
previous pages.
CHINTAN PATEL(ASSISTANT PROFESSOR)
![Page 36: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/36.jpg)
The presentation layer• Concerned with syntax and semantics of the information
transformed.• Translation : Presentation layer at sender changes the
information from sender dependent format to common format. Presentation layer at receiver dos vice versa.
• Encoding• Encryption• Compression
CHINTAN PATEL(ASSISTANT PROFESSOR)
![Page 37: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/37.jpg)
• Providing services to users.• Widely used application protocols like HTTP.• File transfer protocol , SMTP Protocol.• Allows user to access files in remote host , to retrieve files
from a remote computer for use in local computer.
The Application layer
CHINTAN PATEL(ASSISTANT PROFESSOR)
![Page 38: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/38.jpg)
GATE• Layer responsible for dialog control – Session layer.• Suppose in packet loss , system is retransmitting only loss packets .
which layer is responsible : Session layer. Which activity : Synchronization or check point.
• Which layer of OSI Provides privacy : Presentation layer by encryption.
CHINTAN PATEL(ASSISTANT PROFESSOR)
![Page 39: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/39.jpg)
TCP/IP Reference model
CHINTAN PATEL(ASSISTANT PROFESSOR)
![Page 40: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/40.jpg)
CHINTAN PATEL(ASSISTANT PROFESSOR)
![Page 41: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/41.jpg)
The Internet Layer• IP(Internetworking protocol)
Unreliable and connection less protocol – A best effort delivery. No error checking. No guarantee of receiving .
• GATE: IP transforms packet in datagram format.• Data gram can travel along different route and can arrive out of sequence.• ICMP(internet control message protocol)
To send notification of datagram to sender. sends query and error reporting messages.
• IGMP(Internet group message protocol)• ARP(Address resolution protocol) : Associating logical address with physical
address. Used to find physical address when logical address is known
• RARP(Reverse ARP) : provides IP address when physical address is known.
CHINTAN PATEL(ASSISTANT PROFESSOR)
![Page 42: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/42.jpg)
The Transport Layer
• Responsible for delivery of message from one running process to another process.
• Similar to OSI Model.• End-to-End transport layer protocols.
TCP (Transmission control protocol) UDP (User datagram protocol) SCTP (Stream control transmission protocol)
Combines best features of TCP And UDP
CHINTAN PATEL(ASSISTANT PROFESSOR)
![Page 43: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/43.jpg)
TCP And UDP
• TCP : Reliable connection oriented protocol• Allows byte streaming originating at one m/c to be delivered without
error on any other m/c in internet.• Divides a stream of data into smaller units called segment.• GATE : In Transport layer data will be in which formats : segments• Segments have sequence number for reordering .• TCP collects data grams from IP and reorders them based on
sequence number.• Receiver will reassemble the received message.• Also handles flow control.
CHINTAN PATEL(ASSISTANT PROFESSOR)
![Page 44: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/44.jpg)
UDP(User Datagram Protocol)
• unreliable• Process to process protocol • Adds port address , checksum error control and
length information.
CHINTAN PATEL(ASSISTANT PROFESSOR)
![Page 45: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/45.jpg)
The Application Layer
• Contains all higher level protocols.• TELNET(Provides bidirectional text oriented
communication).• FTP• SMTP• DNS (domain name system)• HTTP
CHINTAN PATEL(ASSISTANT PROFESSOR)
![Page 46: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/46.jpg)
Comparison of OSI And TCP / IP• Central concept in OSI are
Services Interface Protocol
• TCP/IP Model did not clearly distinguish between above 3.• OSI Model was devised before the corresponding protocol were invented.• TCP/ IP , protocol was came first and model is just description of existing
protocols.• OSI model has 7 layers and the TCP/IP has 4 layer.• OSI Model supports connectionless and connection oriented communication in network layer and only connection oriented communication in transport
layer.• TCP/IP model has only connection less in network layer but supports both in
transport layer.
CHINTAN PATEL(ASSISTANT PROFESSOR)
![Page 47: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/47.jpg)
Some Important Devices
• WORK STATION• HUB• SWITCH• BRIDGE• ROUTER• GATEWAY
CHINTAN PATEL(ASSISTANT PROFESSOR)
![Page 48: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/48.jpg)
CONNECTION ORIENTED NETWORKS
![Page 49: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/49.jpg)
History• Comes from world of telephone companies.• All packet will follow same route.• So if line will down , call is aborted.• Why telephone companies like it??
1. Quality of service Once connection is established , less chance of packet loss
because resources are reserved for that connection. 2. Billing
Clock can be easily maintained . so billing can easily done.
![Page 50: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/50.jpg)
Connection Oriented Networks• X.25
Establish a connection with remote computer. That is placed a telephone call.
Data packet was consisting of 3 byte header and 128 byte of data. Header consisting of Connection number, A packet sequence number , An
acknowledgement number.
• Frame Relay
Connection oriented network with no error control and no flow control. In order delivery , No error control , No flow control. Most important application is interconnecting LAN at multiple company
offices.
• ATM (Asynchronous Transfer Mode)
![Page 51: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/51.jpg)
ATM
• Asynchronous transfer mode.• Connection oriented.• Solved many communication problem by
merging voice , data , cable TV , smoke signals.• ATM was more success full than OSI and now
widely used in telephone systems.
![Page 52: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/52.jpg)
ATM Virtual circuit• Virtual circuit is connection.• Permanent virtual circuit is permanent
connection between two hosts.• First sending a packet for to set up connection.• Router will make entry in its internal table.
![Page 53: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/53.jpg)
• After establishing the connection , send a data.• Here data will be small , fixed size packets called
a cells. Total 53 byte = 5 byte header + 48 byte data.
• Connection identifier is there in header based on that router can tell which cell belong to which connection.
• Helps router in routing decisions
![Page 54: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/54.jpg)
• Fixed length packet can be sended at high speed but variable length can not.
• All cells follows the same route to destination.• Cell delivery is not guarantee but order is.• During talk, problem can not occur in telephone.• ATM N/W’s are organized like WAN , With lines
and router.• Most common speeds for ATM n/w are 155
mbps.
![Page 55: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/55.jpg)
ATM Reference model• Different than OSI and TCP/IP.
![Page 56: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/56.jpg)
• 3 LAYERS. The physical layer. ATM ATM Adaption layer.
![Page 57: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/57.jpg)
• Physical layer will deals with physical medium• ATM Layer deals with cells and cell transport.
Defines layout of cell and tells about header fields. Deals with establishment and release of virtual circuit. Congestion controls.
• ATM Adaption layer(AAL). Deal with packet segmentation and reassembly.
![Page 58: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/58.jpg)
• User plane : Deals with data transport, flow control , error control.
• Control plane : Deals with connection management.
• Plane and layer management deals with resource management and interlayer coordination.
![Page 59: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/59.jpg)
• Physical layer = Transmission convergence(TC) + PMD(Physical medium dependent)
• Transmission Convergence sub layer : converts bits (0 and 1s ) in cells.
• PMD : Handle bit timing.
![Page 60: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/60.jpg)
![Page 61: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/61.jpg)
Ethernet
• Architecture of the original Ethernet.
![Page 62: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/62.jpg)
Wireless LANs
• (a) Wireless networking with a base station.• (b) Ad hoc networking.
![Page 63: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/63.jpg)
Wireless LANs (2)
• The range of a single radio may not cover the entire system.
![Page 64: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/64.jpg)
Figure (a)The hidden station problem. (b) The exposed station problem.
![Page 65: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/65.jpg)
The Hidden Terminal Problem• Wireless stations have transmission ranges
and not all stations are within radio range of each other.
• Simple CSMA will not work!• C transmits to B.• If A “senses” the channel, it will not hear C’s
transmission and falsely conclude that A can begin a transmission to B.
![Page 66: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/66.jpg)
The Exposed Station Problem
• The inverse problem.• B wants to send to C and listens to the
channel.• When B hears A’s transmission, B falsely
assumes that it cannot send to C.
![Page 67: Unit 1 Introduction to computer network](https://reader038.fdocuments.us/reader038/viewer/2022102806/5576ba10d8b42ad0448b5190/html5/thumbnails/67.jpg)
Wireless LANs (3)
• A multi cell 802.11 network.