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COMMUNICATION NETWORKS Mr. DEEPAK P. Associate Professor ECE Department SNGCE 1 DEEPAK.P UNIT 1 2 DEEPAK.P Objective At the end of this Unit You will learn Network services Layered architecture Network topology DEEPAK.P 3 Social relation In social science, a social relation or social interaction refers to a relationship between two , three or more individuals (e.g. a social group). Normally social network is filled with peoples. Social networking allow users to share ideas, activities, events, and interests within their individual networks. 4 DEEPAK.P Social Network To protect user privacy, social networks usually have controls that allow users to choose who can view their profile, contact them, add them to their list of contacts, and so on. Popular methods now combine many of these, with Face book and Twitter widely used worldwide. 5 DEEPAK.P Pictorial Representation of Social Networks Simple Complex 6 DEEPAK.P Aim for Networking The main aim for networking is Communication Communication means sharing something 7 DEEPAK.P Fundamental Concepts Communication Means Sharing of information. Sharing may be Local Transmits information locally Remote Sending information to remote places. Data Concepts or information is called data. Data communication Sharing of information between two devices 8 DEEPAK.P FUNDAMENTAL CONCEPTS Characteristics/Effectiveness of Data Communication Delivery Accuracy Timeless Components in data communication Protocol Sender 9 DEEPAK.P Protocol Medium Receiver Data Communication Model Protocol Stack Protocol Stack Step1 Step2 Step3 -----------------Step N Step1 Step2 Step3 -----------------Step N Medium Sender 10 DEEPAK.P Receiver Data Communication Model Protocols Specifies common set of rules and signals which computers on the network use to communicate. Protocol suite or protocol stack The total package of protocols. 11 DEEPAK.P Fundamental Concepts Sender MODEM MUX Real Life Data Communication Medium Receiver 12 DEEPAK.P MODEM De MUX Transmission Modes DEEPAK.P 13 Fundamental Concepts Mode of Transmission Transmission can be classified into two according to the direction of data flow. Unidirectional Bidirectional 14 DEEPAK.P Simplex Half Duplex Full Duplex Full – Full Duplex Mode of Transmission. Unidirectional (Simplex) Information is communicated in only one direction. It can be implemented by single wire. Examples One way street Communication from CPU to monitor. Communication from Keyboard to CPU. Communication from Computer to printer. Communication from Microphone to speaker. TV or radio broadcasting 15 DEEPAK.P Mode of Transmission Simplex Sender Receiver Direction of Data Flow Half Duplex Cannot perform two direction at a time Sender Receiver Direction of Data Flow 16 DEEPAK.P Mode of Transmission. Half duplex Information is communicated in both direction, but not simultaneously. It requires definite turn around time to change from transmitting mode to receiving mode. Due to this delay communication is slower . It can be implemented by two wire. One for Data and other is ground Examples One line traffic in narrow bridges. Walkie-talkies. CB (Citizen’s Band) Radio 17 DEEPAK.P Mode of Transmission Full Duplex It can perform two direction at a time Sender Receiver Direction of Data Flow Full –Full Duplex It can perform two direction but not between same two stations Receiver 18 DEEPAK.P Receiver/Sender Direction of Data Flow Sender Mode of Transmission. Full duplex Information is communicated in both direction simultaneously. It can be implemented by as two wire or four wire circuit. In two wire circuit, total channel capacity is divided in to two. In four wire circuit , channel capacity can be increased. Examples Two way traffic. Telephone Conversation. 19 DEEPAK.P Computer Networks DEEPAK.P 20 Computer network In its simplest form, networking is defined as two computers being linked together, either physically through a cable or through a wireless device. Computer network consists of two or more computers linked together to exchange data and share resources A computer network is a collection of hardware components and computers interconnected by communication channels. . 21 DEEPAK.P What is a Computer network • A popular example of a computer network is the Internet, which allows millions of users to share information 22 DEEPAK.P 5/5/2017 An example of a network Router Hub Bridge Hub Internet 23 DEEPAK.P Segment Node Network Goals DEEPAK.P 24 Networks Fundamentals Network Goals or aims 1.Resource sharing.---- May be Software of Hardware 2.High reliability.---Alternative Sources of data Important in banks, military, Air traffic control 3.Saving of money Money can be saved if we go through Client server model 4.Data Sharing. 5.System performance can be improved. 6.Powerful communication medium. 25 DEEPAK.P Network Criteria DEEPAK.P 26 Networks Fundamentals Network Issues/Criteria To consider a network is effective and efficient, it must meet some criteria I. Performance II. Reliability. III. Security I. Performance can be analyzed by Transit time Response Time 27 DEEPAK.P :Time taken to Transmit :Time taken to get a response Network Issues/Criteria Response Time It depends on the following factors. 28 1. No of users. (Traffic Load). 2. Types of medium 3. Type of hardware included in the network. 4. Software were not updated. 5. Lack of education 6. Improper instruction DEEPAK.P Network Issues/Criteria II. Reliability It depends on the following factors. 1. Frequency of failure. 2. Recovery time after failure. 3. Catastrophe----- prevent network from Fire hazards, Earth quakes, Theft III. Security Protecting Data from 29 1. Un authorized access 2. Virus DEEPAK.P Network Issues/Criteria Un authorized access It has two levels Lower level------Improper/Week password Higher level------Encryption techniques 30 DEEPAK.P Network Functions DEEPAK.P 31 Network Functions Addressing--- Identify sender and receiver Routing--- Find the path between sender and receiver Flow Control----Traffic flow can be controlled Congestion control Security Backup Failure monitoring Traffic Monitoring Accountability Internetworking Network Management 32 Error detection and correction DEEPAK.P Network Connections DEEPAK.P 33 Types Of Connections 1. POINT-TO-POINT Provides a direct link between two devices. Eg. Each computer is connected directly to a printer . 2. MULTI-POINT/MULTI DROP Provides a link between three or more devices on a network. It will share the link/Channel capacity 34 DEEPAK.P Types Of Connections Multi point It is two types Time sharing Sharing the link turn by turn Spatially shared Sharing of link simultaneously Two relationship is possible in multi point connection Peer- to –peer All the nodes has equal right to access the link Primary-Secondary One will be master and other will be slave 35 DEEPAK.P What is a Types Of Connections Peer-to-Peer Computers on the network are equals No file server Users decides which files and peripherals to share It is not suited for networks with many computers Easy to set up; Home networks Network Components DEEPAK.P 37 Network Components 1. Physical Media 2. Interconnecting Devices 3. Computers 4. Networking Software Network Components Physical media Cables- Telephone lines, coaxial cable, microwave, satellites, wireless, and fiber optic cables Interconnecting Devices Routers- Devices that examine the data transmitted and send it to its destination Switches- High speed electronic switches maintain connections between computers Protocols- Standards that specify how network components communicate with each other 39 DEEPAK.P Introduction to Computer Networks Physical Media Networking media can be defined simply as the means by which signals (data) are sent from one computer to another (either by cable or wireless means). 40 DEEPAK.P Introduction to Computer Networks Networking Devices HUB, Switches, Routers, Wireless Access Points, Modems etc. 41 DEEPAK.P Network Topology DEEPAK.P 42 Topology A network's topology is comparable to the blueprints of a new home in which components such as the electrical system, heating and air conditioning system, and plumbing are integrated into the overall design. Taken from the Greek work "Topos" meaning "Place," Specifies the geometric arrangement of the network or a description of the layout of a specific region. 43 DEEPAK.P Topology A network topology is the basic design of a computer network. It details how the network components such as nodes and links are interconnected. Topology, in relation to networking, describes the configuration of the network; including the location of the workstations and wiring connections. 44 DEEPAK.P Network Topology It is two types Logical Physical The complete physical structure of the cable (or data- transmission media) is called the physical topology . The way in which data flows through the network (or data- transmission media) is called the logical topology. 45 DEEPAK.P Network Topology Network topology can be classified in to BUS STAR MESH TREE RING HYBRID 46 DEEPAK.P Bus Topology DEEPAK.P 47 Bus Topology 48 DEEPAK.P Bus Topology The simplest and one of the most common of all topologies Bus consists of a single cable, called a Backbone, that connects all workstations on the network using a single line. Each workstation has its own individual signal that identifies it and allows for the requested data to be returned to the correct originator. In the Bus Network, messages are sent in both directions from a single point and are read by the node (computer or peripheral on the network) identified by the code with the message. 49 DEEPAK.P Bus Topology Most Local Area Networks (LANs) are Bus Networks because the network will continue to function even if one computer is down. This topology works equally well for either peer to peer or client server. 50 DEEPAK.P Star Topology DEEPAK.P 51 Star Topology All devices connected with a Star setup communicate through a central Hub by cable segments. Signals are transmitted and received through the Hub. It is the simplest and the oldest and all the telephone switches are based on this. In a star topology, each device has separate connection to the network. 52 DEEPAK.P Star Topology 53 DEEPAK.P 5/5/2017 Ring Topology DEEPAK.P 54 Ring Topology All the nodes in a Ring Network are connected in a closed circle of cable. Messages that are transmitted travel around the ring until they reach the computer that they are addressed to, the signal being refreshed by each node. In a ring topology, the network signal is passed through each network card of each device and passed on to the next device. 55 DEEPAK.P Ring Topology Each device processes and retransmits the signal, so it is capable of supporting many devices in a somewhat slow but very orderly fashion. Important feature is that everybody gets a chance to send a packet and it is guaranteed that every node gets to send a packet in a finite amount of time. 56 DEEPAK.P Ring Topology 57 DEEPAK.P 5/5/2017 Mesh Topology DEEPAK.P 58 Mesh Topology The mesh topology connects all devices (nodes) to each other for redundancy and fault tolerance It is used in WANs to interconnect LANs and for mission critical networks like those used by banks and financial institutions. Implementing the mesh topology is expensive and difficult 59 DEEPAK.P 5/5/2017 Mesh Topology Full Mesh 60 DEEPAK.P Partial Mesh 5/5/2017 Tree Topology DEEPAK.P 61 Tree Topology 62 DEEPAK.P 5/5/2017 Tree Topology 63 DEEPAK.P 5/5/2017 Hybrid Topology DEEPAK.P 64 Hybrid Topology Hybrid networks use a combination of any two or more topologies in such a way that the resulting network does not exhibit one of the standard topologies 65 DEEPAK.P 5/5/2017 Hybrid Topology 66 DEEPAK.P 5/5/2017 Switching DEEPAK.P 67 Connecting devices Switch HUB 68 DEEPAK.P Switch Network consists of a set of inter connected nodes called switches From which information is transmitted from source to destination through different routers. It operates at layer 2 of OSI model (Data Link Layer) 69 DEEPAK.P Switch Switches can be a valuable asset to networking. Switch can increase the capacity and speed of your network. Switches occupy the same place in the network as hubs. Unlike hubs, switches examine each packet and process it accordingly rather than simply repeating the signal to all ports. 70 DEEPAK.P Network Switch 71 DEEPAK.P Network Switch 72 DEEPAK.P Switch Some switches have additional features, including the ability to route packets. These switches are commonly known as layer-3 or multilayer switches. LAN switches come in two basic architectures, Cut-through and Store-and-forward. 73 DEEPAK.P Switch Cut-through switches only examine the destination address before forwarding it on to its destination segment. A store-and-forward switch, on the other hand, accepts and analyzes the entire packet before forwarding it to its destination. 74 DEEPAK.P Switch 75 DEEPAK.P Switches in a Network DEEPAK.P 76 Switches in Network 77 DEEPAK.P Switches in Network 78 DEEPAK.P Switching DEEPAK.P 79 Switching Determines when and how packets/messages are forwarded through the network . Specifies the granularity and timing of packet progress Relationship with flow control has a major impact on performance of a Network 80 DEEPAK.P Switching 81 DEEPAK.P Switching Switching can be classified in to Circuit switched Networks 2. Packet switched Networks 1. Datagram Network Switched virtual circuit Virtual Circuit Networks 3. 82 Message switched Networks DEEPAK.P Permanent virtual circuit Circuit Switching DEEPAK.P 83 Circuit Switching It is a methodology of implementing a telecommunications network in which two network nodes establish a dedicated communications channel (circuit). In circuit switching, most of the time line is idle Circuit switching gives fixed data rate Once circuit is established , that connection is the path for transmission. 84 DEEPAK.P Switch 85 DEEPAK.P Switch 86 DEEPAK.P Circuit Switching Circuit switching is also termed as connection oriented networks It has three steps Connection Establishment Data Transfer Circuit Disconnects 87 DEEPAK.P Circuit Switching In circuit switching, a caller must first establish a connection to a called party before any communication is possible. It maintain the connection to transfer message The circuit is terminated when the connection is closed. 88 DEEPAK.P Circuit Switching 89 DEEPAK.P Circuit Switching 90 DEEPAK.P Circuit Switching Circuit switching uses any of the three technologies 1. Space division switches 2. Time division switches 3. Combination of both 91 DEEPAK.P Space division switches Provide a separate physical connection between inputs & outputs (separated in space) Some of the space switches are Cross bar switch Crossbar switch: consists of N x N cross-points ( N: number of input lines = number of output lines) 92 Multi stage switch DEEPAK.P Cross Bar Switch 93 DEEPAK.P Cross Bar Switch 94 DEEPAK.P Multi Stage Switch/ Omega Switch 95 DEEPAK.P Time Division Switch 96 DEEPAK.P Time Division Switch TDM with Switching using TSI TSI=Time Slot Interchange 97 DEEPAK.P Packet Switching DEEPAK.P 98 Packet Switching Data are send as packets Packet size can be variable Packet contains data and header 99 DEEPAK.P Switch 100 DEEPAK.P Switching 101 DEEPAK.P Packet Switching Network layer offer two services Connection oriented service A connection is called virtual circuit Connectionless service The independent packets are called Data grams 102 DEEPAK.P 1. Data gram Network Routes from source to destination are not worked out in advance. Packets takes different routes. It does not maintain a table. It is the responsibility of transport layer to re order the Data grams 103 DEEPAK.P Data grams A 4 3 2 1 Y 1 1 3 3 1 3 4 4 2 B 104 4 3 1 4 2 2 4 3 1 X DEEPAK.P 2. Virtual Circuit Only one route from source to destination When connection is established, it is used for all the traffic. When connection is released, the virtual circuit is terminated. Every router has to maintain a table. 105 DEEPAK.P i. Switched Virtual Circuit (SVC) It is similar to dial-up lines A virtual circuit is created whenever it is needed. 106 DEEPAK.P Switched Virtual Circuit (SVC) 107 A Y B X DEEPAK.P ii. Permanent Virtual Circuit (PVC) Virtual circuit is provided between two user on a continuous basis. 108 DEEPAK.P Permanent Virtual Circuit 109 A Y B X DEEPAK.P Data gram Vs Virtual circuit Network Parameter VC Datagram Circuit setup Required Not required Addressing Each packet contains a short VC number Each packet contains a source , destination address Repairs Easy to repair Harder to repair State information Table is required to hold state information Table is not required to hold state information Routing Route is fixed. (Static routing) Routed independently(dynamic routing) Congestion control Easy Difficult 110 DEEPAK.P Message Switching DEEPAK.P 111 3. Message switching message switching is similar to packet switching, where messages were routed one hop at a time. No physical path is established in advance in between sender and receiver. When the sender has a block of data to be sent, it is stored in the first switching office (i.e. router) then forwarded later at one hop at a time. 112 DEEPAK.P Message switching 113 DEEPAK.P Layered Architecture DEEPAK.P 114 A simple example for communication We use the concept of layers in our daily life. As an example, let us consider two friends who communicate through postal mail. 115 DEEPAK.P simple example for communication But 5 Steps are needed for proper delivery DEEPAK.P 116 simple example for communication V. Writing letter in a paper ( Raw Data) IV. Put signature ,Fold the letter and put the letter in a cover (Adding Header1, Compression etc) III. Seal the cover& Put signature (Provides security, Header2) II. Dropped the letter in to mail box after fixing stamp (Adding Header3& trailer1) I. Postman collects the letter to the post office ( TRANSMISSION THROUGH A MEDIUM) 117 DEEPAK.P simple example for communication Sorting the letter at the post office (ROUTING) I. Postman collects the letter from post office to the mail box (Transmitting data bits) II. Letter was taken from mail box to Home (Removing header3& Trailer) III. Open the cover& signature (Removes Header2) IV. Take the letter from the cover (Removing Header1) V. Reading letter ( Raw Data) 118 DEEPAK.P Network architecture Network architecture is the overall design of a network The network design is divided into layers, each of which has a function separate of the other layers Protocol stack- The vertical (top to bottom) arrangement of the layers; Each layer is governed by its own set of protocols Network architecture Virtual Communication Between layers Message is generated by 5th layer Layer 4 add header in front of message Header include control information to send the message in the right order. Layer 3 breaks up the message in to small units called packets Layer 2 add header and trailer to packets. Layer 1 transmits the raw data. Issues in Layered Architecture Design Philosophy of Layered Architecture The complex task of communication is broken into simpler sub-tasks or modules Each layer performs a subset of the required communication functions Each layer relies on the next lower layer to perform more primitive functions Changes in one layer should not affect the changes in the other layers Helps in troubleshooting and identifying the problem DEEPAK.P 122 Design issues for layers Addressing Identify sender and receiver Direction of transmission Simplex, half duplex, full duplex Error control Error detection and correction algorithms Avoid loss of sequencing Sequence number Ability to receive long messages Disassemble , transmit, reassemble Use of multiplexing and de multiplexing Share the channel Network Models DEEPAK.P 124 Need for Network Models • Network communication is an extremely complex task. • Layer architecture simplifies the network design. • The complex task of communication is broken into simpler sub-tasks or modules • Need cooperative efforts from all nodes involved 125 DEEPAK.P Need for Network Models • A standard model helps to describe the task of a networking product or service • Also help in troubleshooting by providing a frame of reference. The network management is easier due to the layered architecture. . 126 DEEPAK.P Need for Layered Architecture • Each layer works with the layer below and above it • Each layer provides services to next layer 127 DEEPAK.P Who define Network Model? • Need non-profit making organizations • ISO - International Standards Organization IEEE - Institute of Electrical & Electronic Engineers ITU - International Telecommunication Union 128 DEEPAK.P OSI Model DEEPAK.P 129 OSI Reference Model The Open Systems Interconnection model is a theoretical model that shows how any two different systems can communicate with each other. 130 DEEPAK.P OSI Model OSI Reference Model The OSI model is now considered the primary Architectural model for inter-computer communications. The OSI model describes how information or data makes its way from application programmes through a network medium (such as wire) to another application programme located on another network. This separation into smaller more manageable functions is known as layering. 131 DEEPAK.P OSI Model To standardize the design of communication system, the ISO created the OSI model ISO standard that covers all aspects of network communications is the Open Systems Interconnection (OSI) model. Contains Seven layers It describes the functions to be performed at each layer DEEPAK.P 132 OSI Model First introduced this model in the late 1970s. A layer model, Each layer performs a subset of the required communication functions Changes in one layer should not require changes in other layers DEEPAK.P 133 Important ISO is the organization. OSI is the model. DEEPAK.P 134 OSI Model Application Presentation Session Transport Network Data Link Physical DEEPAK.P 135 The OSI 7-layer Model All People Pizza Seem Sausage To Throw Need Not Data Do Processing 136 Away DEEPAK.P Please Peer-to-Peer Process using OSI DEEPAK.P 137 Relationship of OSI layers Virtual Communication Physical Communication 138 DEEPAK.P Data exchange using the OSI model DEEPAK.P 139 Flow of data in the OSI model User network Coding methods Synchronization points Entire message Packet (logical address) Frames (node node) Bit stream signal 140 DEEPAK.P OSI Model OSI Model 141 DEEPAK.P Protocols in a layered architecture • Network communication is possible only if machines speaking the same languages (protocols) • Network communication is possible only if the Protocol Stacks on two machines are the same 142 DEEPAK.P Functions of Physical layer DEEPAK.P 143 Physical Layer DEEPAK.P 144 OSI Model – Physical Layer This layer is the lowest layer in the OSI model. It helps in the transmission of data between two machines that are communicating through a physical medium, which can be optical fibres, copper wire or wireless etc. Hardware Specification: The details of the physical cables, network interface cards, wireless radios, etc are a part of this layer. 145 DEEPAK P DEEPAK.P 145 5 May 2017 OSI Model – Physical Layer Physical interface between devices Handles the transmission of bits over a communications channel Choice of Wired / wireless medium Data is converted into signals Includes voltage levels, connectors, media choice modulation techniques EIA/TIA-232, RJ45, NRZ. DEEPAK.P 146 Functions of Physical Layer Make and Break physical connections. Define voltages and data rate Convert data bit in to electrical stream Decide mode of transmission Define physical topology Line configuration 147 DEEPAK P DEEPAK.P 147 5 May 2017 Medium used for Physical Connections 148 DEEPAK.P Medium used for Physical Connections 149 DEEPAK.P Note The physical layer is responsible for movements of individual bits from one hop (node) to the next. DEEPAK.P 150 Functions of Data link layer DEEPAK.P 151 OSI Model – Data Link Layer • Means of activating, maintaining and deactivating a reliable link DEEPAK.P 152 Functions of Data Link Layer Framing Physical Addressing Flow Control Error Control Access control Synchronization. DEEPAK.P 153 Access control in Data Link Layer Sharing the access of the link Based on access control IEEE split the data link layer in to two is called IEEE project 802 Logical Link Control(LLC) 1. • 2. Establish and maintain link Media Access control(MAC) Provides shared access and communicates with network Interface Cards Establish a logical link between two computers DEEPAK.P 154 Data Link Sub layers Logical Link 802.1 Control 802.2 (LLC) Media Access Control (MAC) 155 DEEPAK.P 802.3 802.4 802.5 802.12 Note The data link layer is responsible for moving frames from one hop (node) to the next. DEEPAK.P 156 Functions of Network layer DEEPAK.P 157 OSI Model – Network Layer • Transport of information • Responsible for creating, maintaining and ending network connections • Routing • Transfers a data packet from node to node within the network. Examples :- IP, IPX, AppleTalk. DEEPAK.P 158 Network Layer DEEPAK.P 159 Functions of Network layer 1. Routing of signals 2. Divide outgoing message in to packets 3. Act as network controller 4. Logical Addressing 1. 160 Convert logical address to physical address DEEPAK P DEEPAK.P 160 5 May 2017 Note The network layer is responsible for the delivery of individual packets from the source host to the destination host. DEEPAK.P 161 Functions of Transport layer DEEPAK.P 162 Transport Layer Transport – Exchange of data between end systems (end to end flow control) • • Error free • • Sequencing • Quality of service Layer 4 protocols include TCP (Transmission Control Protocol) and UDP (User Datagram Protocol). DEEPAK.P 163 Services offered by Transport Layers Connection oriented Service Establish connection Use the connection Release the connection Connection less Service Similar to postal service Each message is routed independently Quality of service Reliable--- No Data Loss, Using ACK Un reliable DEEPAK.P 164 Transport Layer DEEPAK.P 165 Functions of Transport layer 166 1. Transmission is parallel or single path 2. Multiplexing 3. Segmentation and re assembly 4. Service point addressing 5. Connection control DEEPAK P DEEPAK.P 166 5 May 2017 Note The transport layer is responsible for the delivery of a message from one process to another. DEEPAK.P 167 Functions of Session layer DEEPAK.P 168 OSI Model – Session Layer Session – Control of dialogues between applications • Synchronization Points (backup points) • Examples :- SQL, ASP(AppleTalk Session Protocol), NETBIOS, RPC, PAP. DEEPAK.P 169 Functions of Session layer Controls logging off and logging on User identification Billing and session management 170 DEEPAK P DEEPAK.P 170 5 May 2017 Note The session layer is responsible for dialog control and synchronization. DEEPAK.P 171 Functions of Presentation layer DEEPAK.P 172 OSI Model – Presentation Layer 1. 2. 3. Translation Data compression Encryption Examples :- JPEG, MPEG, ASCII, EBCDIC, HTML. DEEPAK.P 173 Note The presentation layer is responsible for translation, compression, and encryption. DEEPAK.P 174 Functions of Application layer DEEPAK.P 175 OSI Model – Application Layer Application – Layer where the application using the network resides. – Common network applications include remote login file transfer e-mail web page browsing etc. – Means for applications to access OSI environment DEEPAK.P 176 Note The application layer is responsible for providing services to the user. DEEPAK.P 177 Summary of layers DEEPAK.P 178 • To identify the language (protocol) of each layer, identifier (header and trailer) are added to data 179 DEEPAK.P TCP/IP Model DEEPAK.P 180 TCP/IP Model It is used earlier by ARPANET Developed by research foundation by US department of defense Later this architecture is known as TCP/IP model It has two protocols Transmission control protocol Message is divided in to packets Then Put in to IP packet 2. Internet protocol Provide IP addressing 1. DEEPAK.P 181 TCP/IP Protocol Suit TCP/IP suite is the set of protocols that implement the protocol stack on which the Internet runs. It is sometimes called the Internet Model. This model consists of five ordered layers This model was developed prior to OSI model DEEPAK.P 182 Internet layers Internet Data Link Physical DEEPAK.P 183 OSI vs TCP/IP Application Presentation Session Transport Network Data Link Physical DEEPAK.P 184 TCP/IP Model 185 DEEPAK.P TCP/IP Model Networking concept can also explained with the help of 4 layer protocol concept It is a variation of TCP/IP 5 layer model DEEPAK.P 186 Variation of TCP/IP Application Presentation Session Transport Network Data Link Physical DEEPAK.P 187 TCP/IP protocol stack Internetwork Network Interface and Hardware DEEPAK.P 188 Data flow in TCP/IP Model DEEPAK.P 189 TCP/IP Protocol Architecture Model DEEPAK.P 190 OSI vs TCP/IP OSI TCP/IP 7 Layer 4/5 layer Transport layer guarantees delivery of packets Transport layer does not guarantees delivery of packets Separate session layer No session Layer, Characteristics are provided by transport layer Separate presentation layer No presentation Layer, Characteristics are provided by application layer Network layer offer connectionless and connection oriented service Network layer offer connectionless service Easy to replace the protocols Not easy to replace protocols General Model TCP/IP cannot be used for any other application Some Protocols in TCP/IP Suite DEEPAK.P 192 Some Protocols in TCP/IP Suite DEEPAK.P 193 TCP/IP Frames Header contains source and destination IP addresses; Upper level (i.e. transport) protocol type Header contains source and destination physical addresses; Upper level (i.e. network) protocol type IP Header Frame Check Sequence Ethernet Header IP datagram is encapsulated in an Ethernet frame DEEPAK.P 194 TCP/IP Frames DEEPAK.P 195 TCP/IP Services Two kinds of services: TCP & UDP. TCP—Transmission Control Protocol, reliable connection oriented transfer of a byte stream. UDP—User Datagram Protocol, best-effort connectionless transfer of individual messages. DEEPAK.P 196 UNIT 2 197 DEEPAK.P Network Classification/ Network configuration DEEPAK.P 198 Network Classification Networks may be classified according to a wide variety of characteristics such as the Transmission Technology Scale Medium used to transport the data Topology Organizational scope. Communications protocol used 199 DEEPAK.P Network Classifications Network categorization according the following are important 1. Transmission Technology 2. Scaling/ According to physical size According to Transmission technology 200 1. Broadcast Networks 2. Point to point Networks DEEPAK.P Network Classifications 1. Broadcast Networks • Single communication channel shared by all the users • Packets sent by any machine are received by all the others (only one sender) 2. Point to point Networks • It consists of many connections between all machines • It consists of dedicated links between each node 201 DEEPAK.P Network Classifications • Broadcast Networks • Point to point Networks 202 DEEPAK.P Network Classification according to scaling DEEPAK.P 203 Main Categories of networks 204 DEEPAK.P Main Categories of Network Local area network (LAN) Metropolitan area network (MAN) Links computers within a building or group of buildings Uses direct cables, radio or infrared signals Links computers within a major metropolitan area Uses fiber optic cables Wide area network Links computers separated by a few miles or thousands of miles Uses long-distance transmission media 205 DEEPAK.P Network Scaling 206 DEEPAK.P Network Scaling 207 Inter processor distance Processors are located in networks 0.1 m Same circuit board Data flow machine 1m Same system Multi computer 10m Same room LAN 100m Same building LAN 1km Same campus LAN 10km Same city MAN 100km Same country WAN 1000km Same continent WAN 10000km Same planet Internet DEEPAK.P PAN PAN DEEPAK.P 208 Personal Area Networks (PAN) • A PAN is a network that is used for communicating among computers and computer devices (including telephones) in close proximity of around a few meters within a room. • It can be used for communicating between the devices themselves, or for connecting to a larger network such as the internet. • PAN’s can be • Wired • Wireless • 209 DEEPAK.P 5/5/2017 Personal Area Networks (PAN) 210 DEEPAK.P 5/5/2017 Personal Area Networks (PAN) PAN’s can be wired with a computer bus such as a universal serial bus USB (a serial bus standard for connecting devices to a computer, where many devices can be connected concurrently) PAN’s can also be wireless through the use of bluetooth (a radio standard for interconnecting computers and devices such as telephones, printers or keyboards to the computer) or IrDA (infrared data association) technologies • 211 DEEPAK.P 5/5/2017 Personal Area Networks (PAN) • Wireless PAN 212 DEEPAK.P 5/5/2017 LAN DEEPAK.P 213 Local area networks (LAN) A LAN is a network that is used for communicating among 214 computer devices, usually within an office building or group of buildings or home LAN’s enable the sharing of resources such as files or hardware devices that may be needed by multiple users Is limited in size, typically spanning a few hundred meters, and no more than a mile Is fast, with speeds from 10 Mbps to 10 Gbps Requires little wiring, typically a single cable connecting to each device Has lower cost compared to MAN’s or WAN’s DEEPAK.P 5/5/2017 MAN DEEPAK.P 215 Metropolitan area network A metropolitan area network (MAN) is a computer network in which two or more computers or communicating devices or networks which are geographically separated but in same metropolitan city. A MAN is optimized for a larger geographical area than a LAN A MAN typically covers an area of between 5 and 10 km diameter. 216 DEEPAK.P MAN 217 DEEPAK.P Metropolitan area network Network in a City is call MAN It is larger than a LAN, but smaller than a WAN It is also used to mean the interconnection of several LANs by bridging them together. This network is also referred to as a campus network 218 DEEPAK.P MAN 219 DEEPAK.P WAN DEEPAK.P 220 Wide area network (WAN) A Wide Area Network is a network in which a large geographical area of around several hundred miles to across the globe May be privately owned or leased Also called “enterprise networks” if they are privately owned by a large company It can be leased through one or several carriers (ISPs- Internet Service Providers) such as AT&T, Sprint, Cable and Wireless Can be connected through cable, fiber or satellite Is typically slower and less reliable than a LAN 221 DEEPAK.P WAN 222 DEEPAK.P WAN 223 DEEPAK.P Types of WANs Internet Backbone providers charge fees to Internet Service Providers (ISP) ISPs sell subscriptions to users Public Data Network (PDN) for-profit data communications network Not secure Fees paid on a per-bytetransferred basis Not ideal for businesses Good security High bandwidth Private Data Network Used by corporations, banks and governments Not open to the public Most secure type of WAN 224 Virtual private network- Lines are leased to a single DEEPAK.P company LAN STRUCTURE DEEPAK.P 225 LAN When you have several computers, it can be convenient to connect them to each other to create a local area network (LAN). A physical network structure is composed mostly of cables, switches and workstations. 226 DEEPAK.P LAN There are two main types of local network architecture: 1. Wired networks, based on the Ethernet technology, which represent almost all local area networks. Given that Ethernet networks generally use RJ45 cables, people often talk of RJ45 networks; 2. 227 Wireless networks, which generally use the Wi-Fi technology. DEEPAK.P 5/5/2017 Local area networks (LAN) 228 DEEPAK.P LAN Ethernet Structure Ethernet LAN made up of several desktop systems and a server attached to a coaxial cable. 229 DEEPAK.P 5/5/2017 Repeaters to Build Multi segment LANs 230 DEEPAK.P 5/5/2017 Bridges to Build Multi segment LANs 231 DEEPAK.P 5/5/2017 Local area networks (LAN) Users can access software, data and peripherals Require special hardware and software Computers connected to a LAN are called workstations or nodes Different types: Peer-to-peer Client-server 232 DEEPAK.P Local area networks (LAN) Peer-to-peer 233 DEEPAK.P Client-server Introduction to Computer Networks LAN Clients and Servers In a client/server network arrangement, network services are located in a dedicated computer whose only function is to respond to the requests of clients. The server contains the file, print, application, security, and other services in a central computer that is continuously available to respond to client requests. 234 DEEPAK.P Local area networks (LAN) LAN’s can be either wired or wireless. Twisted pair, coax or fiber optic cable can be used in wired LAN’s Nodes in a LAN are linked together with a certain topology. These topologies include: 235 1. Bus 2. Ring 3. Star 4. Branching tree DEEPAK.P 5/5/2017 LAN Topology DEEPAK.P 236 LAN Topologies Topologies resolve the problem of contention or users trying to access the LAN at the same time Collisions or corrupt data occurs when computers use the network at the same time Bus topology Called daisy chain Every workstation connected to a single bus cable Resolves collisions through contention management Difficult to add workstations Star topology Contains a hub or central wiring concentrator Easy to add workstations Resolves collisions through contention management Ring topology All workstations attached in a circular arrangement A special unit of data called a token travels around the ring Workstations can only transmit data when it possesses a token 237 DEEPAK.P LAN Topologies Bus Topology Each node is connected one after the other (like christmas lights) Nodes communicate with each other along the same path called the backbone Backbone 238 DEEPAK.P LAN Topologies Ring Topology The ring network is like a bus network, but the “end” of the network is connected to the first node Nodes in the network use tokens to communicate with each other Backbone 239 DEEPAK.P LAN Topologies Star Topology Each node is connected to a device in the center of the network called a hub The hub simply passes the signal arriving from any node to the other nodes in the network The hub does not route the data Hub 240 DEEPAK.P LAN Topologies Branching Tree Topology 241 DEEPAK.P Components in LAN DEEPAK.P 242 Components in a Local area networks A node is defined to be any device connected to the network. This could be a computer, a printer, a router, etc. A Hub is a networking device that connects multiple segments of the network together A Network Interface Card (NIC) is the circuit board that has the networking logic implemented, and provides a plug for the cable into the computer (unless wireless). In most cases, this is an Ethernet card inserted in a slot of the computer’s motherboard 243 DEEPAK.P 5/5/2017 Components in a Local area networks The Network Operating System (NOS) is the software (typically part of the operating system kernel) that communicates with the NIC, and enables users to share files and hardware and communicate with other computers. Examples of NOS include: Windows XP, Windows NT, Sun Solaris, Linux, etc.. 244 DEEPAK.P 5/5/2017 Hardware and software requirement for LAN Hardware Network interface card (NIC)Inserted into computer’s expansion slot Software Operating system that supports networking (Unix, Linux, Windows, Mac OS) Additional system software Hardware and software requirement for LAN File server A high speed, high capacity computer Contains the network operating system ( Novell Netware, Windows NT, XP Server) Contains network versions of programs and large data files Advantage of LAN 1. File transfers; 2. Sharing of resources (internet connection sharing, printer sharing, shared disks, etc.); 247 3. Mobility (in the case of a wireless network); 4. Discussion (mainly when the computers are remote); 5. Network games. DEEPAK.P 5/5/2017 Multiple Access Communications DEEPAK.P 248 Multiple Access Communication The channel is employed to provide communication media between a set of geographically distributed terminals. Channel access method or multiple access method allows several terminals connected to the same multi-point transmission medium to transmit over it and to share its capacity. Multiple access schemes are used to allow many nodes to share the link simultaneously. 249 DEEPAK.P Multiple Access Communication 1. 2. 3. FDMA TDMA CDMA A channel-access scheme is also based on a multiple access protocol and control mechanism, also known as media access control (MAC). 250 DEEPAK.P Data Link Control 251 DEEPAK.P Data Link Control( DLC) In the OSI networking model, Data Link Control (DLC) is the service provided by the data link layer. Network interface cards have a DLC address that identifies each card. DLC identifier (DLCI) that uniquely identifies the node on the network. For networks that conform to the IEEE 802 standards (e.g., Ethernet ), the DLC address is usually called the Media Access Control (MAC) address. 252 DEEPAK.P Data Link Sub layers Logical Link 802.1 Control 802.2 (LLC) Media Access Control (MAC) 253 DEEPAK.P 802.3 802.4 802.5 802.12 Logical Link Control( LLC) 1. Logical Addressing 2. Provide Control Information 3. Control the Data 254 DEEPAK.P Media Access Control( MAC) 1. Flow control Link /Media control 2. Error Control 3. Access control 4. Synchronization 255 DEEPAK.P Link/ Media Control 256 1. Flow Control Restrict the amount of data that the sender can send 2. Error Control a. Damaged frames b. Lost frames c. Lost Acknowledgement DEEPAK.P 1. 257 DEEPAK.P Flow Control Performance Metrics and Delays Transmission time (delay) a. Time taken to emit all bits into medium 2. Propagation time (delay) a. Time for a bit to traverse the link 3. Processing time (delay) a. time spent at the recipient or intermediate node for processing 4. Queuing time (delay) a. waiting time at the queue to be sent out 1. Model of Frame Transmission transmission time propagation time Flow Control Necessary when data is being sent faster than it can be processed by receiver. If sender sends faster than recipient processes, then buffer overflow occurs Flow control prevents buffer overflow Flow control can be of two types Stop & Wait 2. Sliding window 1. 260 DEEPAK.P 1. Stop and Wait Flow Control This flow control mechanism forces the sender after transmitting a data frame to stop and wait until the acknowledgement of the data-frame sent is received. 1. 2. 3. 4. 5. 6. Source transmits frame Destination receives frame and replies with acknowledgement (ACK) Source waits for ACK before sending next frame Destination can stop flow by not sending ACK Works well for large frames Inefficient for smaller frames Stop and Wait Flow Control Stop and Wait Flow Control Generally large block of data split into small frames Called “Fragmentation” and is used when 1. 2. 3. 4. Limited buffer size at receiver Errors detected sooner (when whole frame received) On error, retransmission of smaller frames is needed Prevents one station occupying medium for long periods Channel Utilization is higher when 1. 2. The transmission time is longer than the propagation time Frame length is larger than the bit length of the link 2. Sliding Window Flow Control The problem of “Stop and Wait” is not able to send multiple packets Sliding Window Protocol allows multiple frames to be in transit In this flow control mechanism both sender and receiver agrees on the number of data-frames after which the acknowledgement should be sent. Sliding Window Flow Control 1. Receiver has buffer of W (called window size) frames 2. Transmitter can send up to W frames without ACK 3. Each frame is numbered 4. Sequence number bounded by size of the sequence number field 5. ACK includes number of next frame expected Sliding Window Flow Control (W = 5) Example of a Sliding Window Protocol (W = 7) 3. 268 DEEPAK.P Access Control Access Control Access Control means controlling the link when computers transmit. It is important in situations where more than one computer wants to send data at the same time over the same circuit. The two main MAC approaches are 1. Controlled access 2. Contention Based / Polling 269 DEEPAK.P 1. Controlled Access Controlled access works like a stop light, controlling access to the shared resource of the network circuit. It is also used by some local area network protocols (token ring, FDDI). 270 DEEPAK.P 2. Contention Based Access Contention approaches, such as Ethernet, allow all the computers to transmit whenever the circuit is free. Like two people in a group speaking at the same time, their messages collide and have to be resent. This means collisions can occur (more than one computer transmitting at the same time). 271 DEEPAK.P Contention Based Access Contention approaches to media access control need to have a way to sort out which computer is allowed to transmit first after a collision occurs. A mechanism used for this is polling 272 DEEPAK.P Relative Performance Contention approaches tend to work better for smaller networks with relatively low usage. Since usage is low, the probability of collisions is also low, but when volume is high their performance deteriorates. Controlled access tends to work better for networks with high traffic volumes where the probability of collisions is high and controlling access means the network will be more efficiently used. 273 DEEPAK.P Relative Performance of Controlled vs. Contention based MAC protocols Multiple Access 275 DEEPAK.P Multiple Access Broadcast link is called multi access channel. If two transmitter transmit at the same time , their signal may interface or collide. A method is needed to share the broadcast link and avoid collision is called medium access control (MAC) 276 DEEPAK.P Multiple Access CHANNEL 277 DEEPAK.P Multiple Access When no: of stations uses a common link, we have to use multiple access protocol. Thee techniques or protocols are mainly used to deal with multiple access problem Random Access. 2. Controlled Access. 3. Channelization. 1. 278 DEEPAK.P Multiple Access Controlled Access 279 DEEPAK.P 1. Random Access Protocols Random Access There is no Control station. Each station has the right to use the common medium. The will be an increased probability of collision. Random access protocols are ALOHA 2. CSMA 3. CSMA/CD 4. CSMA/CA 1. 280 DEEPAK.P 2. Controlled Access Protocols Controlled access There will be a Control station. Control station has the right to allocate the link to the different users. The probability of collision will be some what lesser. Main Controlled access protocols are a) Reservation b) Round-Robin 281 DEEPAK.P 2. Controlled Access Protocols Round Robin In Round Robin techniques, each and every node is given the chance to send or transmit by rotation. 282 DEEPAK.P 2. Controlled Access Protocols Reservation Centralized b) Distributed a) 283 DEEPAK.P Controlled Access Protocols Reservation Centralized Clients was prioritized so that they are polled more frequently. b) Distributed Permission to access the link is carried out using a special message called a poll. a) 284 DEEPAK.P Polling 285 DEEPAK.P Polling Polling, on computer networks, involves a server and client. With polling, the server periodically contacts each client to see if it wants to transmit. Clients transmit only after being asked by the server if they want to send something. 286 DEEPAK.P Polling Polling may be Centralized (often called hub polling) 2. Decentralized(distributed)/Roll call. 1. In roll call polling, each client is checked in order to see if it wants to transmit. Clients can also be prioritized so that they are polled more frequently. In a decentralized polling scheme, each station knows its successor in the polling sequence and send the poll directly to that station. 287 DEEPAK.P Polling 288 DEEPAK.P Polling Permission to transmit on the network is passed from station to station using a special message called a poll. In hub polling (also called token passing) one computer starts the poll, sending message (if it has one) and then passes the token on to the next computer. This continues in sequence until the token reaches the first computer, which starts the polling cycle all over again. 289 DEEPAK.P Polling 290 DEEPAK.P Polling In hub polling, the polling order is maintained by a single central station or hub. When a station finishes its turn transmitting, it sends a message to the hub, which then forwards the poll to the next station in the polling sequence. 291 DEEPAK.P Token Passing 292 DEEPAK.P Token Passing 293 DEEPAK.P Token Passing 294 DEEPAK.P Channelization 295 DEEPAK.P Multiple Access Protocols Channelization Typical channelization methods include 1. 2. 3. 296 Frequency differentiation (FDMA) Time division multiplexing (TDMA) Code division multiple access (CDMA) DEEPAK.P Random Access 297 DEEPAK.P Multiple Access 298 DEEPAK.P Random Access Random Access There is no Control station. Each station has the right to use the common medium. The will be an increased probability of collision. Random access protocols are ALOHA 2. CSMA 3. CSMA/CD 4. CSMA/CA 1. 299 DEEPAK.P Multiple Access Multiple Access Carrier Sense Multiple Access CSMA/CD 300 DEEPAK.P CSMA/CA Multiple Access methods ALOHA used a simple procedure called multiple access (MA) It was improved to develop Carrier Sense Multiple Access (CSMA) Carrier Sense" describes the fact that a transmitter uses feedback from a receiver that detects a carrier wave before trying to send. OR That is, it tries to detect the presence of an encoded signal from another station before attempting to transmit. 301 DEEPAK.P Carrier Sense Networks A Network which adopts carrier sense is called carrier sense networks CSMA evolves two methods 1. CSMA/CD 2. CSMA/CA 302 DEEPAK.P ALOHA 303 DEEPAK.P ALOHA System It is invented by Norman Abramson in 1970 f1 Central Computer f2 f1= Random access f2= Broadcast 304 DEEPAK.P ALOHA System Contention System Multiple user share a common link, leads to conflicts are known as contention systems. ALOHA is a Contention system If a collision occurs, wait random amount of time then retransmit; repeat until successful Receiver send ACK for data Detect collisions by timing out for ACK 305 DEEPAK.P ALOHA System 306 DEEPAK.P ALOHA System ALOHA has two version 307 1. Pure ALOHA/ Un slotted a) Does not need time synchronization 2. Slotted ALOHA b. Need time synchronization DEEPAK.P Pure ALOHA It allows any station to broadcast at any time. If two signal collides, each station wait a random time and tries again Collisions are easily detected When central station receives a frame it sends an ACK on a different frequency. It is very simple 308 DEEPAK.P Pure ALOHA Central station F1 Station F2 Station Station 309 DEEPAK.P Station Pure ALOHA Collision 0 310 DEEPAK.P T 2T Pure ALOHA System 311 DEEPAK.P Slotted ALOHA Developed by Roberts in 1972 Changing the protocol from continuous time to slotted time One frame can be sent in each slots. All transmitters are synchronized so that all transmissions start at the beginning of a slot 312 DEEPAK.P Slotted ALOHA Time is divided in to discrete intervals (T) Each interval corresponds to one frame 0 313 DEEPAK.P T 2T Slotted ALOHA 314 DEEPAK.P Slotted ALOHA 315 DEEPAK.P Slotted ALOHA Vs Pure ALOHA 316 DEEPAK.P CSMA 317 DEEPAK.P CSMA Link Utilization can be improved in CSMA It operates on the principle of Carrier sensing In this principle , a station listen to see the presence of fames in the link. CSMA can be divided in to three Non Persistent 1- persistent P- Persistent 318 DEEPAK.P CSMA Non Persistent Station check the link. If the station is busy, it has to wait for fixed interval of time After this time , it again check the status of the channel. Wait randomly Channel ? Busy Idle 319 DEEPAK.P CSMA 1- persistent It continuously monitor the link until it is idle. It then transmits immediately. Channel ? Busy Idle 320 DEEPAK.P CSMA P- persistent All waiting stations are not allowed to transmit simultaneously when the channel is idle. Only P=1/N station can transmit while others will wait. Channel ? idle Channel ? Busy 321 >p Wait a slot Idle Prob. outcome? <p Use back off process DEEPAK.P Busy Station can transmit Carrier Sense Comparison 322 DEEPAK.P CSMA/CD 323 DEEPAK.P CSMA/CD Carrier Sense Multiple Access with Collision Detection (CSMA/CD) It is widely used on LAN in MAC layer CSMA/CD protocol can be considered as a refinement over the CSMA scheme. This refined scheme is known as Carrier Sensed Multiple Access with Collision Detection (CSMA/CD) or Listen-While-Talk. 324 DEEPAK.P CSMA/CD The nodes continue to monitor the channel while transmitting a packet and immediately stop transmission when collision is detected and it transmits jamming signal for a brief duration to ensure that all stations know that collision has occurred. Collision can be detected by comparing TX data with RX data in Ethernet 325 DEEPAK.P CSMA/CD Listen to channel while transmitting data If collision occurs, immediately stop sending, back- off and retransmit Sending a jam signal to all transmitters Better performance than plain CSMA Examples: Ethernet, Wi-Fi 326 DEEPAK.P CSMA/CD 327 DEEPAK.P Carrier Sense comparison 328 DEEPAK.P CSMA/CD CSMA/CD can be in one of three states Contention, transmission, or idle. Frame Transmission period 329 DEEPAK.P Frame Contention period Frame Contention Slots Frame Idle Periods CSMA/CD Frame format Pre amble(7Byte)-Alert receiver to coming Frame SFD-Start Frame de limiter(1)-Beginning of Frame DA-Destination Address(2 to 6)-Destination address of NIC SA-Source Address(2 to 6) -Source address of NIC L-Length of data field(2)-Length or type of PDU Frame Data (Variable)-Actual Data FCS/CRC-Frame check status(4)-Error correction PAD- Adding extra bit to adjust the frame size PR 330 DEEPAK.P SFD DA SA L DATA PAD FCS CSMA/CA 331 DEEPAK.P CSMA/CA Sender send a request-to-send (RTS) frame to receiver and indicates the time needed to complete data transmission Receiver send clear-to-send (CTS) frame, indicates time to complete data transmission and reserves channel for the sender Sender transmits the data and receiver responds with an ACK frame, ensuring reliable transmission RTS and CTS frames let other stations know of the data transmission so that collision is avoided Used by 802.11 wireless LAN 332 DEEPAK.P CSMA/CA Unlike CSMA/CD (Carrier Sense Multiple Access/Collision Detect) which deals with transmissions after a collision has occurred, CSMA/CA acts to prevent collisions before they happen. CSMA/CA differs from CSMA/CD due to the nature of the medium, the radio frequency spectrum. RTS-CTS-DATA-ACK to request medium Random back off after collision is detected 333 DEEPAK.P CSMA/CA The main difference is the collision avoidance : on a wire, the transceiver has the ability to listen before and while transmitting and so to detect collisions. Collisions are avoided using three strategies Inter frame space (IFS) The contention window Acknowledgements 334 DEEPAK.P LAN standards 335 DEEPAK.P LAN standards LAN uses four architecture Ethernet Token Bus Token Ring Fiber Distributed Data Interface These standards are the part of IEEE’s Project 802 336 DEEPAK.P IEEE 802 IEEE 802 refers to a family of IEEE standards dealing with local area networks and metropolitan area networks. This IEEE project covers the first two layers of the OSI model and part of the third level. IEEE 802 splits the OSI Data Link Layer into two sub-layers named Logical Link Control (LLC) Media Access Control (MAC) 337 DEEPAK.P IEEE 802 More specifically, the IEEE 802 standards are restricted to networks carrying variable-size packets. LLC Upper sub layer It will take care of Logical address, Control information and data. MAC Lower sub layer It contains Synchronization, Flag, Flow and Error control specifications 338 DEEPAK.P IEEE 802 IEEE 802 OSI Model Other Layers Other Network 802.1 Internetworking Network 802.2 Logical link control Data Link 802.3 CSMA 802.4 Token Bus 802.5 Token ring Physical 339 DEEPAK.P IEEE 802 LAN standards Network Layer Network Layer LLC 802.2 Logical Link Control MAC Physical Layer 802.3 CSMA-CD 802.5 Token Ring 802.11 Wireless LAN Various Physical Layers Data Link Layer Other LANs Physical Layer OSI IEEE 802 340 Figure 6.11 IEEE 802 PDU (Protocol Data Unit) The data unit in LLC is called PDU PDU contains 4 fields Destination service access point (DSAP) Source Service Access point (SSAP) Control field Information field DSAP 341 DEEPAK.P SSAP Control Information IEEE 802 standards IEEE 802.1 Management and Internetworking IEEE 802.2 Logical Link Control(LLC) IEEE 802.3 Ethernet (CSMA/CD) IEEE 802.4 Token Bus 342 DEEPAK.P IEEE 802 standards IEEE 802.5 Token Ring IEEE 802.6 MAN Networks IEEE 802.7 Broad Band LAN IEEE 802.8 Fiber Optic LANS 343 DEEPAK.P IEEE 802 standards IEEE 802.9 Integrated Data and Voice Networks IEEE 802.10 Security IEEE 802.11 Wireless Networks 344 DEEPAK.P IEEE 802 standards In LAN all the stations share common cable IEEE adopted 3 mechanism for media access control CSMA/CD(IEEE 802.3) Token Bus (IEEE 802.4) Token Ring (IEEE 802.5) 345 DEEPAK.P IEEE 802.3 346 DEEPAK.P IEEE 802.3(Ethernet) The IEEE 802.3 standard is based on the ALOHA system IEEE standard 802.3 specifies the following characteristics of Ethernet. The medium is normally base band co-axial cable. Bandwidth is 10Mbps Cable segment length is 500m. 347 DEEPAK.P IEEE 802.3(Ethernet) It is a packet switching LAN technology. Most widely used LAN protocol. It uses CSMA/CD It defines two categories Base Band Broad band 348 DEEPAK.P Baseband & Broadband LAN 349 DEEPAK.P Base band LAN The two ways to allocate the capacity of transmission media are with baseband and broadband transmissions. Baseband devotes the entire capacity of the medium to one communication channel. The base band specifies a digital signal 350 DEEPAK.P Base band LAN Baseband LAN uses a single-carrier frequency over a single channel. Most LANs function in baseband mode. Ethernet, Token Ring and Arcnet LANs use base band transmission. 351 DEEPAK.P Broad band LAN Broadband enables two or more communication channels to share the bandwidth of the communications medium. Broadband LANs use frequency-division multiplexing on a coaxial cable to establish a communications network 352 DEEPAK.P Broad band Vs Base Band LAN Baseband transmission is bidirectional but the broadband is unidirectional. No any frequency division multiplexing use in baseband . where as frequency division multiplexing use in broadband . In baseband signal travel short distance and in broadband signal can travel long distance. Broad band specifies analog signal 353 DEEPAK.P IEEE 802.3(Ethernet) 808802.3 802.3 Base Band 10 Base5,10 base 2,10 base T,10 base F 354 DEEPAK.P Broad Band 10 broad 36 IEEE 802.3(Ethernet) The first number (10,1,100) indicates Data rates in MBPS The last number indicates cable length in meters or type of cable. Ethernet uses coaxial cable as medium. A device called Transceiver is used to establish connection between computer and cable. Cable Transceiver Hosts 355 DEEPAK.P IEEE 802.3(Ethernet Generations) Standard Ethernet (10 Base 5{Thick Ethernet/Thicknet}) (10 Base 2{Thin Ethernet}) (10 Base T{Twisted Pair Ethernet}) (10 Base F{Fiber Ethernet}) Fast Ethernet Gigabit Ethernet 10 Gigabit Ethernet 356 DEEPAK.P Standard Ethernet(10 Base 5) It uses bus topology LAN is divided in to segments Maximum segment length is 500 meters Total length cannot exceed 2500 meters(5 segments) Segment 1 Segment 5 ……….. 2.5m 2.5m 500 m 357 DEEPAK.P 500 m 2500 m Standard Ethernet(10 Base 2) It uses bus topology It reduces cost , Installation is easy Maximum segment length is 200 meters Smaller capacity N 358 DEEPAK.P Standard Ethernet(10 Base T) It uses Star topology It uses Un shielded Twisted Pair cable(UTP) Data rate is 10MBPS Maximum length(Hub to station) of 100 meters 359 DEEPAK.P Standard Ethernet(10 Base F) It uses Star topology It uses Fiber optic cables Data rate is 10MBPS Maximum length(Hub to station) of 2Km Fiber optic cables 360 DEEPAK.P IEEE 802.3(Ethernet) 361 DEEPAK.P Ethernet Frame Format Preamble 7 bytes SFD 1 byte Destination Address 6 bytes Source address 6 bytes P DA = 2 SA = 6 362 DEEPAK.P L Length PDU Data and 2 bytes padding 0-46 bytes DATA FCS CRC 4 bytes Ethernet Frame Format • Preamble: For synchronization • Des. Add: Destination address • Sour. Add: Source address • FCS: Frame Check Sequence --- Error control 363 DEEPAK.P Ethernet Address Ethernet addresses are 48 bits long. Ethernet addresses are governed by IEEE and are usually imprinted on Ethernet cards when the cards are manufactured. 364 DEEPAK.P Ethernet Address 00 00 E2 15 1A CA 365 DEEPAK.P Comparison 366 DEEPAK.P Scheduling Approaches to MAC 367 DEEPAK.P Approaches to Media Sharing Medium sharing techniques Static channelization Partition medium Dedicated allocation to users Satellite transmission Cellular Telephone Dynamic medium access control Scheduling Polling: take turns Request for slot in transmission schedule Token ring Wireless LANs Random access Loose coordination Send, wait, retry if necessary Aloha Ethernet Scheduling Approaches to MAC Multiple users share the communication channel so a scheme (medium sharing technique) must be devised to prevent collision of packets 1. Reservation Systems 2. Polling Systems 3. Token Passing Systems 4. Static Channelization: TDMA and FDMA 369 DEEPAK.P Reservation Systems • Transmissions from stations are organized in cycles that have variable length. • Each cycle consists of a reservation interval followed by the transmitted packets. 370 DEEPAK.P Reservation Systems A station uses its mini slot in the reservation interval to broadcast its intention for transmission 371 DEEPAK.P Modification in Reservation Systems Variable length frames be accommodated if the reservation slot for a station contains information on the frame length 372 DEEPAK.P Modification in Reservation Systems More than one frame can be transmitted by a station by modifying the reservation slot to indicate number of frames to be transmitted per station 373 DEEPAK.P Network Connecting Devices 374 DEEPAK.P Network Connecting Devices 375 DEEPAK.P Network Connecting Devices Repeaters and Hubs--- To increase the coverable distance Bridges----- Traffic Management It has some filtering capacity Routers---- Routing to other networks Gateway---- Provides security Switches ---- Fast connecting 376 DEEPAK.P Connecting Devices and OSI Model 377 DEEPAK.P Network Connecting Devices 378 DEEPAK.P Repeaters 379 DEEPAK.P Repeaters 380 DEEPAK.P Repeater 381 DEEPAK.P Repeaters A repeater is specific hardware designed to overcome signal attenuation It usually has only two ports and is designed to pure boost or amplify a signal. Ethernet hubs and repeaters operate at the Physical Layer of the OSI Reference model 382 DEEPAK.P Repeaters 383 DEEPAK.P Hubs 384 DEEPAK.P HUBS hub are very similar to repeaters and is basically a multi port repeater. Repeater is usually used for the extension of the length while hub is a simple connectivity gadget that is used to broaden a network. The central connecting device in a computer network is known as a hub. 385 DEEPAK.P HUBS Hubs are also known as "multi-port repeaters" or "active star networks”. 386 DEEPAK.P Working of a HUBS 387 DEEPAK.P HUB When data packets arrives at hub, it broadcast them to all the LAN cards in a network. There are two types of hub Active hub--- Repeats or re generate signal Passive hub--- Used only for connection 388 DEEPAK.P LAN BRIDGES 389 DEEPAK.P Bridge A bridge is a network communication device that is used to connect one segment of the network with another that uses the same protocol. Bridges are fast devices for forwarding the data but not as fast as the routers and switches. A bridge when combined with the router, known as a brouter. Bridges has now replaced the switches and routers. 390 DEEPAK.P Bridges 391 DEEPAK.P Bridge 392 DEEPAK.P Bridges 393 DEEPAK.P Bridges Bridges operate in the Data Link layer Bridges are two types Transparent Bridge Routing Bridge The duties of Transparent bridges are Filtering frames Forwarding Blocking 394 DEEPAK.P Bridges 395 DEEPAK.P Transparent Bridges 396 DEEPAK.P Transparent Bridges A transparent bridge is a common type of bridge that observes incoming network traffic to identify media access control (MAC) addresses. These bridges operate in a way that is transparent to all the network's connected hosts. Transparent bridges are implemented primarily in Ethernet networks. 397 DEEPAK.P Transparent Bridges There are two types of Transparent Bridge Modes: Store-and-Forward: Stores the entire frame and verifies the CRC before forwarding the frame. If a CRC error is detected, the frame is discarded. Cut-Through: Forwards the frame just after it reads the destination MAC address without performing a CRC check. 398 DEEPAK.P Transparent Bridges Transparent bridges save and maintain the source-route addresses of incoming frames by listening to all the connected bridges and hosts. They use a transparent bridging algorithm to a accomplish this. The algorithm has five parts: Learning Flooding Filtering Forwarding Avoiding loops 399 DEEPAK.P Transparent Bridges Transparent bridges actively listen to traffic on each segment on which it is attached. When a transparent bridge encounters a frame that is to be forwarded to a destination MAC it forwards it out a specific port that it has associated with that MAC address. 400 DEEPAK.P Transparent Bridges If a bridge does not 'know' that MAC address (has no port associated with that MAC), it sends the frame out all the other ports on the bridge. Frames are never forwarded out the port they are received on. 401 DEEPAK.P Source Route Bridges 402 DEEPAK.P Source route Bridges The route through the LAN internet is determined by the source (originator) of the traffic hence this bridge is called as source routing bridge. The routing information field (RIF) in the LAN frame header, contains the information of route followed by the LAN network. 403 DEEPAK.P Mixed-Media Bridging 404 DEEPAK.P Mixed Media Bridges Transparent bridges are found predominantly in Ethernet networks, and source-route bridges (SRBs) are found almost exclusively in Token Ring networks. Both transparent bridges and SRBs are popular, so it is reasonable to ask whether a method exists to directly bridge between them. 405 DEEPAK.P Mixed Media Bridges 406 DEEPAK.P LAN Switches 407 DEEPAK.P Switch A network switch (sometimes known as a switching hub) is a computer networking device that is used to connect devices together on a computer network. Switches are another fundamental part of many networks because they speed things up. Switches allow different nodes (a network connection point, typically a computer) of a network to communicate directly with one another in a smooth and efficient manner. A switch is considered more advanced than a hub because a switch will only send a message to the device that needs or requests it, rather than broadcasting the same message out of each of its ports. 408 DEEPAK.P Switch A switch is a multi-port network bridge that processes and forwards data at the data link layer (layer 2) of the OSI model. Like a hub, a switch connects multiple segments of a network together, with one important difference. Whereas a hub rebroadcasts anything it receives on one port to all the others, a switch makes a direct link between the transmitting device and receiving device. Any party not involved in that communication will not receive the transmission. The benefit of a switch over a hub is that the switch increases performance because it doesn’t suffer from the wasted bandwidth of the extra transmissions. 409 DEEPAK.P Switch 410 DEEPAK.P Switch Working 411 DEEPAK.P Switching Methods 412 DEEPAK.P Router 413 DEEPAK.P Router 414 DEEPAK.P Comparison of Networking Devices 415 DEEPAK.P Comparison of Networking Devices 416 DEEPAK.P UNIT 3 Inter Networking 417 DEEPAK.P Inter network 418 DEEPAK.P Inter network Internetworking is the practice of connecting a computer network with other networks through the use of gateways that provide a common method of routing information packets between the networks. The resulting system of interconnected networks is called an internetwork. Internetworking is a combination of the words inter ("between") and networking; The most common example of internetworking is the Internet 419 DEEPAK.P Inter network Inter networking can be classified in to two Connection oriented or concatenated of virtual circuit subnets Connectionless or Datagram 420 DEEPAK.P Connection oriented Virtual circuit 421 DEEPAK.P virtual circuit • 422 A virtual network link is a link that does not consist of a physical (wired or wireless) connection between two computing devices but is implemented using methods of network virtualization. DEEPAK.P concatenated of virtual circuit A X.25 Routers ATM Subnet 3 SNA M M Subnet 1 B Host Subnet 2 Multi protocol router (Gateway) SNA-System Network Architecture 423 DEEPAK.P virtual circuit Establishment Subnet shows that the destination is remote destination and builds a virtual circuit to the router nearest to the destination. 2. It then constructs a virtual circuit from that router to an external gateway (multi protocol router). 3. This gateway notes down the existence of this virtual circuit in its table and builds another virtual circuit to a router which is in the next subnet. 4. This process continues until the destination host has been reached. 1. 424 DEEPAK.P virtual circuit Establishment 5. After building the virtual circuit, data packets begin to flow along the path 425 DEEPAK.P Advantage& Disadvantage virtual circuit Advantage Buffer can be reserved in advance Shorter header can be used Sequencing can be guaranteed Drawbacks There is no alternate path to avoid congestion Router failure creates big problems 426 DEEPAK.P Connection less 427 DEEPAK.P Datagram Internetworking Datagram packets Path 1 M M A Routers Subnet 3 Datagram packets M M Subnet 1 B Path 2 Host Subnet 2 428 DEEPAK.P Multi protocol router (Gateway) Datagram Internetworking The packets that are forwarded across the Internet are known as IP datagrams An IP datagram consists of a header and a payload The header contains information that allows Internet routers to forward the datagram from the source host to the destination host 429 DEEPAK.P Datagram Internetworking Header contains all information needed to deliver datagrams to destination computer Destination address Source address Identifier Other delivery information Router examines header of each datagram and forwards datagram along path to destination 430 DEEPAK.P Advantage& Disadvantage Datagram Advantage Higher Bandwidth Deal with congestion in a better way It is robust in Router failure Drawbacks No guarantee of packets Addressing is difficult Longer header is needed 431 DEEPAK.P Tunneling 432 DEEPAK.P Tunneling It is used when source and destination networks of same type are to be connected through a network of different type. Consider an ethernet network to be connected to another ethetnet through a WAN The task is send on IP packet from host A of Ethernet 1 to the host B of ehernet 2 wia a WAN. In this example, the IP packet do not have to deal with WAN. 433 DEEPAK.P Tunneling The host A&B do not have to deal with WAN The multiprotocol routers M1 and M2 will have to understand about IP and WAN packet. Therefore WAN can be imagined to be equivalent to a big tunnel extending between multiprotocol routers M1 and M2. So this technique is called Tunneling 434 DEEPAK.P Tunneling WAN HOST A Tunnel M1 M2 HOST B Ethernet 1 Ethernet 2 IP IP WAN packet Header Ethenet Frame IP packet is inside the payload field of WAN packet 435 DEEPAK.P Sequence of events in Tunneling 436 1. Host A construct a packet containing the IP address of host B 2. It then inserts this IP packet in to ethernet frame. 3. This frame is addressed to the multi protocol router M1. 4. Host A then puts this frames on Ethernet. 5. When M1 receives this frames, it removes IP packet, inserts it in the IP payload packet of the WAN network layer packet and addresses the WAN packet to M2. 6. The multi protocol router M2 remeoves the IP packet and send it to host B in an ethernet frame. DEEPAK.P Datagram forwarding in IP 437 DEEPAK.P IP forwarding Using Datagram The IP forwarding algorithm, commonly known as IP routing, is a specific implementation of routing for IP networks and gives a more directed approach in forwarding datagram's over a network. In order to achieve a successful transfer of data the algorithm uses a routing table to select a next-hop router as the next destination for a datagram. The IP address that is selected is known as the next-hop address. 438 DEEPAK.P Delivery of an IP datagram Internetwork is a collection of LANs or point-to-point links or switched networks that are connected by routers. 439 DEEPAK.P Datagram forwarding in IP An IP network is a logical entity with a network number We represent an IP network as a “cloud” The IP delivery service takes the view of clouds, and ignores the data link layer view 440 DEEPAK.P Datagram Packets at the network layer level are called datagrams They are encapsulated in frames for delivery across physical networks Datagrams are formed by header and payload Datagrams can have different sizes – Header is fixed (20 bytes) – Data area can contain between 1 byte and 65 KB 441 DEEPAK.P Forwarding Datagrams Header contains all information needed to deliver datagrams to destination computer Destination address – Source address – Identifier – Other delivery information Router examines header of each datagram and forwards datagram along path to destination 442 DEEPAK.P Networks and IP addressing IP address: Network part + Host part Network: Any host can physically be reached by any other host without intervening router All hosts in the same network have the same network number 443 DEEPAK.P Networks and IP addressing 444 DEEPAK.P Routing tables Each router and each host keeps a routing table which tells the router how to process an outgoing packet Main columns: 1. Destination address: where is the IP datagram going to? 2. Next hop: how to send the IP datagram? 3. Interface: what is the output port? 445 DEEPAK.P Routing tables Next hop and interface column can often be summarized as one column Routing tables are set so that datagrams gets closer to the its destination. 446 DEEPAK.P Delivery with routing tables 447 DEEPAK.P IP Frame format Header Beginning of Data Payload 448 DEEPAK.P IP Header 449 DEEPAK.P IP Header ProtocolVersion(4 bits) : This is the first field in the protocol header. This field occupies 4 bits. This signifies the current IP protocol version being used. Most common version of IP protocol being used is version 4 while version 6 is out in market and fast gaining popularity. 450 DEEPAK.P IP Header Header Length(4 bits) : This field provides the length of the IP header. The length of the header is represented in 32 bit words. Since this field is of 4 bits so the maximum header length allowed is 60 bytes. 451 DEEPAK.P IP Header Type of service(8 bits) : The first three bits of this field are known as priority bits and are ignored as of today. The next 4 bits represent type of service and the last bit is left unused. The 4 bits that represent TOS are : minimize delay, maximize throughput, maximize reliability and minimize monetary cost. 452 DEEPAK.P IP Header Total length(16 bits): This represents the total IP datagram length in bytes. Since the header length (described above) gives the length of header and this field gives total length so the length of data and its starting point can easily be calculated using these two fields. Since this is a 16 bit field and it represents length of IP datagram so the maximum size of IP datagram can be 65535 bytes. 453 DEEPAK.P IP Header Identification(16 bits): This field is used for uniquely identifying the IP datagrams. This value is incremented every-time an IP datagram is sent from source to the destination. This field comes in handy while reassembly of fragmented IP data grams. 454 DEEPAK.P IP Header Flags(3 bits): This field comprises of three bits. While the first bit is kept reserved as of now, the next two bits have their own importance. The second bit represents the ‘Don’t Fragment’ bit. The third bit represents the ‘More Fragment’ bit. 455 DEEPAK.P IP Header Fragment offset(13 bits): In case of fragmented IP data grams, this field contains the offset( in terms of 8 bytes units) from the start of IP datagram. So again, this field is used in reassembly of fragmented IP datagrams. 456 DEEPAK.P IP Header Time to live(8 bits) : This value represents number of hops that the IP datagram will go through before being discarded. The value of this field in the beginning is set to be around 32 or 64 (lets say) but at every hop over the network this field is decremented by one. When this field becomes zero, the data gram is discarded. So, we see that this field literally means the effective lifetime for a datagram on network. 457 DEEPAK.P IP Header Protocol(8 bits) : This field represents the transport layer protocol that handed over data to IP layer. This field comes in handy when the data is demultiplex-ed at the destination as in that case IP would need to know which protocol to hand over the data to. 458 DEEPAK.P IP Header Header Checksum(16 bits) : This fields represents a value that is calculated using an algorithm covering all the fields in header (assuming this very field to be zero). This value is calculated and stored in header when IP data gram is sent from source to destination and at the destination side this checksum is again calculated and verified against the checksum present in header. If the value is same then the datagram was not corrupted else its assumed that data gram was received corrupted. So this field is used to check the integrity of an IP datagram. 459 DEEPAK.P IP Header Source and destination IP(32 bits each) : These fields store the source and destination address respectively. Since size of these fields is 32 bits each so an IP address os maximum length of 32 bits can be used. So we see that this limits the number of IP addresses that can be used. To counter this problem, IP V6 has been introduced which increases this capacity. 460 DEEPAK.P IP Header Options(Variable length) : This field represents a list of options that are active for a particular IP datagram. This is an optional field that could be or could not be present. If any option is present in the header then the first byte is represented as follows : 461 DEEPAK.P IP Header In the description above, the ‘copy flag’ means that copy this option to all the fragments in case this IP datagram gets fragmented. The ‘option class’ represents the following values : 0 -> control, 1-> reserved, 2 -> debugging and measurement, and 3 -> reserved. Some of the options are given below : 462 DEEPAK.P IP Header 463 DEEPAK.P IP Header Data: This field contains the data from the protocol layer that has handed over the data to IP layer. Generally this data field contains the header and data of the transport layer protocols. Please note that each TCP/IP layer protocol attaches its own header at the beginning of the data it receives from other layers in case of source host and in case of destination host each protocol strips its own header and sends the rest of the data to the next layer. 464 DEEPAK.P ARP 465 DEEPAK.P ARP Address Resolution Protocol (ARP) is a telecommunications protocol used for resolution of network layer addresses into link layer addresses ARP was defined by RFC (radio Frequency Committee) 826 in 1982 If a machine talks to another machine in the same network, it requires its physical or MAC address. ARP is used to convert an IP address to a physical address such as an Ethernet address 466 DEEPAK.P ARP IP address of the destination node is broadcast and the destination node informs the source of its MAC address. Assume broadcast nature of LAN Broadcast IP address of the destination Destination replies it with its MAC address. Source maintains a cache of IP and MAC address bindings 467 DEEPAK.P ARP 468 DEEPAK.P ARP A host wishing to obtain a physical address broadcasts an ARP request onto the TCP/IP network. The host on the network that has the IP address in the request then replies with its physical hardware address. 469 DEEPAK.P ARP Send broadcast request receive unicast response 470 DEEPAK.P ARP 471 DEEPAK.P ARP Problem: Router A needs to forward an IP datagram to router B (which is on the same Ethernet LAN) Router A knows the IP address of B. But the IP datagram must be encapsulated within an Ethernet frame, whose Ethernet destination address is the address of B’s NIC How can A discover the Ethernet Address of B’s NIC? 472 DEEPAK.P ARP A uses the Address Resolution Protocol (ARP) to discover B’s NIC Ethernet address. It goes like this: A broadcasts an Ethernet frame on the LAN. The payload of the frame is an ARP request: who has address 148.4.20.10 (B’s IP address). All computers in the LAN hear the broadcast. The computer whose IP address is 148.4.20.10 (B) replies to A: my ethernet address is aa:bb:cc:dd:ee:ff. 473 DEEPAK.P ARP Now A has the ethernet address of B ’s NIC, and can send the IP datagram to B encapsulated within an Ethernet frame with destination address aa:bb:cc:dd:ee:ff. 474 DEEPAK.P ARP request/reply In capsulation in Ethernet Frame 475 DEEPAK.P ARP Header format 476 DEEPAK.P ARP Header Hardware type (HTYPE) This field specifies the network protocol type. Example: Ethernet is 1. Protocol type (PTYPE) This field specifies the internetwork protocol for which the ARP request is intended. For IPv4, this has the value 0x0800. The permitted PTYPE values share a numbering space with those for Eather type Hardware length (HLEN) Length (in octets) of a hardware address. Ethernet addresses size is 6. 477 DEEPAK.P ARP Header Protocol length (PLEN) Length (in octets) of addresses used in the upper layer protocol. (The upper layer protocol specified in PTYPE.) IPv4 address size is 4. Operation Specifies the operation that the sender is performing: 1 for request, 2 for reply. Sender hardware address (SHA) media address of the sender. 478 DEEPAK.P ARP Header Sender protocol address (SPA) internetwork address of the sender. Target hardware address (THA) media address of the intended receiver. This field is ignored in requests. Target protocol address (TPA) internetwork address of the intended receiver. ARP protocol parameter values have been standardized and are maintained by the Internet Assigned Numbers Authority (IANA). 479 DEEPAK.P ICMP 480 DEEPAK.P ICMP Data delivery using IP datagram is the best delivery scheme but it has two deficiencies. Lack of error control Lack of assistance mechanism. These ICMP can compensate these deficiencies. It is a companion to IP protocol 481 DEEPAK.P ICMP IGMP IP Network Layer ICMP ARP RARP 482 DEEPAK.P ICMP Internet Control Message Protocol It is a network layer protocol Used mostly for error reporting at the IP level. But its message is not passed directly to the data link layer The messages are first encapsulated inside IP datagram before going to the lower layer 483 DEEPAK.P Encapsulation of ICMP messages 484 DEEPAK.P ICMP ICMP MESSAGE ERROR REPORTING 485 DEEPAK.P QUERY ICMP The error reporting message reports problems occurred at router or a host. The query message , which occurs in pairs , help a host or a network manager to get specific information from a router or another host ICMP does not correct errors , it simply reports them. 486 DEEPAK.P ICMP error reporting Error reporting Destination un reachable Source Quench Time exceeded Parameter problems Re direction Source quench--- Flow control to IP Parameter problem– Any ambiguity in the header part Re direction--- Host routing table updation is caaried out 487 DEEPAK.P ICMP For example, if the TTL of the IP datagram reaches 0 when it reaches a router, the datagram is dropped by the router, and the router sends an ICMP message back to the source of the datagram to inform it that the datagram was dropped because its TTL reached 0 (Time Exceeded) If a router does not know how to route an IP datagram, it drops the datagram an send an ICMP message back to the source (Destination unreachable). 488 DEEPAK.P ICMP Messages with message number 489 DEEPAK.P ICMP header 490 DEEPAK.P ICMP header Type field defines the type of message Code field specifies reason for particular message Checksum for error reporting 491 DEEPAK.P DHCP 492 DEEPAK.P DHCP Dynamic Host Configuration Protocol Allows a computer to obtain an IP address and other parameters from a DHCP server A DHCP server is a program running in some fixed computer in the LAN that has been configured to assign IP addresses from a given range to other computers in the LAN that request them The DHCP server also provides things like default routes, and DNS server addresses 493 DEEPAK.P DHCP DHCP requests are broadcasted within the local LAN (frame dest ff:ff:ff:ff:ff:ff) If the DHCP server is in a different LAN, the request won’t reach that server. One way around this is to configure some other computer in the LAN as a dhcp relay agent : the relay will intercept the DHCP request and forward it to the DHCP server on the other LAN Simplifies management, as only one DHCP sever needs to be configured for the entire network, rather than having to configure separate DHCP servers for each LAN 494 DEEPAK.P Subnetting 495 DEEPAK.P Subnet A sub network, or subnet, is a logically visible subdivision of an IP network. The practice of dividing a network into two or more networks is called subnetting. All computers that belong to a subnet are addressed with a common, identical, most-significant bit-group in their IP address 496 DEEPAK.P Subnet Subnetting an IP Network can be done for a variety of reasons, including organization, use of different physical media (such as Ethernet, FDDI, WAN, etc.), preservation of address space, and security. The most common reason is to control network traffic. 497 DEEPAK.P IP Packet 498 DEEPAK.P IP Packet 499 DEEPAK.P IP Packet An IP packet has two fundamental components: IP header 1. Payload 2. 500 IP header contains many fields that are used by routers to forward the packet from network to network to a final destination. Contains layer 3 info Fields within the IP header identify the sender, receiver, and transport protocol and define many other Parameters. Represents the information (data) to be delivered to the receiver by the sender. Contains data & upper-layer info DEEPAK.P IP Versions 501 DEEPAK.P IPV4 502 DEEPAK.P IPV4 Internet Protocol is one of the major protocol in TCP/IP protocols suite. This protocol works at Network layer of OSI model and at Internet layer of TCP/IP model. Thus this protocol has the responsibility of identification of hosts based upon their logical addresses and to route data between/among them over the underlying network. IPv4 is a connectionless protocol for use on packet-switched networks. 503 DEEPAK.P IPV4 Internet Protocol version 4 (IPv4) is the fourth version in the development of the Internet Protocol (IP) Internet, and routes most traffic on the Internet. However, a successor protocol, IPv6, has been defined and is in various stages of production deployment. IPv4 is described in IETF publication RFC 791 It operates on a best effort delivery model, in that it does not guarantee delivery, nor does it assure proper sequencing or avoidance of duplicate delivery. 504 DEEPAK.P IPV4 IPv4 uses 32-bit (four-byte) addresses, which limits the address space to 4294967296 (232) addresses. 505 DEEPAK.P IPv4 - Packet Structure The encapsulated data is referred to as IP Payload. IP header contains all the necessary information to deliver the packet at the other end. 506 DEEPAK.P IPv4 - Packet Structure 507 DEEPAK.P IPv4 - Addressing IPv4 supports three different type of addressing modes: Unicast Addressing Mode: In this mode, data is sent only to one destined host. The Destination Address field contains 32- bit IP address of the destination host. Here client sends data to the targeted server 508 DEEPAK.P IPv4 – Unicast Addressing 509 DEEPAK.P IPv4 – Broadcast Addressing Mode: In this mode the packet is addressed to all hosts in a network segment. The Destination Address field contains special broadcast address i.e. 255.255.255.255. When a host sees this packet on the network, it is bound to process it. Here client sends packet, which is entertained by all the Servers: 510 DEEPAK.P IPv4 – Broadcast Addressing Mode: 511 DEEPAK.P IPv4 – Multicast Addressing Mode: This mode is a mix of previous two modes, i.e. the packet sent is neither destined to a single host nor all the host on the segment. In this packet, the Destination Address contains special address which starts with 224.x.x.x and can be entertained by more than one host. 512 DEEPAK.P IPv4 – Multicast Addressing Mode: 513 DEEPAK.P IPV6 514 DEEPAK.P IPV6 Internet Protocol version 6 (IPv6) is the latest revision of the Internet Protocol (IP), the communications protocol that provides an identification and location system for computers on networks and routes traffic across the Internet. IPv6 was developed by the Internet Engineering Task Force (IETF) to deal with the long-anticipated problem of IPv4 address exhaustion. IPv6 is an Internet Layer protocol for packet-switched internetworking and provides end-to-end datagram transmission across multiple IP networks, 515 DEEPAK.P IPV6 516 DEEPAK.P IPV6 & IP V 4 517 DEEPAK.P IPV6 & IP V 4 518 DEEPAK.P Routing 519 DEEPAK.P Routing Routing means finding a suitable path for a packet from sender to destination 520 DEEPAK.P Routing Routing is the main function of the network layer. Network layer protocols responsible for deciding which output line an incoming packet should be transmitted on. Routing is usually performed by a dedicated device called a router. The path with lowest cost is considered as best. 521 DEEPAK.P Routing The routing algorithm is the part of a network layer software responsible 522 for deciding which output line a packet should be transmitted on Each router stores information about forwarding in a routing table – Initialized at system initialization – Must be updated as network topology changes A routing table contains a list of destination networks and next hop for each destination Note that a router has several IP addresses! – One IP address per interface DEEPAK.P Classification of Routing Routing schemes differ in their delivery semantics: Unicast: delivers a message to a single specific node. Broadcast: delivers a message to all nodes in the network. Multicast: delivers a message to a group of nodes that have expressed interest in receiving the message. Anycast: delivers a message to any one out of a group of nodes, typically the one nearest to the source. Geocast: delivers a message to a geographic area. 523 DEEPAK.P Classification of Routing Routing can be classified in to two Static Routing or Non adaptive Do not consider measurement and estimate of current traffic and topology on their routing decisions Eg. Flooding, Flow based routing, Shortest path Dynamic Routing or Adaptive Change routing decisions to reflect changes in topology Eg. Distance vector routing , Link state routing 524 DEEPAK.P Routing Protocols Routing Protocols Interior (Routing inside an autonomous System) OSPF(Open shortest path first 525 DEEPAK.P RIP(Routing information Protocol Exterior (Routing between autonomous system) BGP (Border gateway Protocol) Desirable Properties of Routing Algorithms 526 DEEPAK.P Static Routing 527 DEEPAK.P Flooding It is a static algorithm Every incoming packet is sent out on every outgoing line except the one it arrived on. It will generate vast no of duplicate packets. 528 DEEPAK.P Flooding 529 DEEPAK.P Application of Flooding Military application Distributed database application Wireless network 530 DEEPAK.P Selective Flooding Variation of flooding is selective flooding Do not send every incoming packet out on every line. It sends to the line that are going approximately in the right direction. 531 DEEPAK.P Flow-based Routing Similar in spirit to minimum distance, but takes traffic flow into consideration. From the known average amount of traffic and the average length of a packet you can compute the mean packet delays using queuing theory. Flow-based routing then seeks to find a routing table to minimize the average packet delay through the subnet. 532 DEEPAK.P Flow-based Routing Assume that traffic is huge from A to B B C D A E G F H TAKE THE ROUTE AGEFC INSTEAD OF ABC 533 DEEPAK.P Shortest path Links between routers have a cost associated with them. In general it could be a function of Distance Bandwidth Average traffic Communication cost Mean queue length Measured delay Router processing speed 534 DEEPAK.P Shortest path algorithms The shortest path algorithm just finds the least expensive path through the network, based on the cost function. Dijkstras algorithms Bellman-ford algorithms 535 DEEPAK.P Dynamic Routing 536 DEEPAK.P Distance vector Routing 537 DEEPAK.P Distance Vector Routing In this routing each router 'telling the neighbors about the whole network'. Each router maintains a table called vector. Each router periodically shares its knowledge about the entire network with its neighbors. The working principle of distance vector routing includes Knowledge about the whole network Routing only to neighbors Information sharing at regular intervals 538 DEEPAK.P Distance Vector Routing 539 DEEPAK.P Distance Vector Routing In distance vector algorithms, each router has to follow the following steps: It counts the weight of the links directly connected to it and saves the information to its table. In a particular period of time, the router sends its table to its neighbor routers (not to all routers) and receives the routing table of each of its neighbors. Based on the information the router receives from its neighbors' routing tables, it updates its own. 540 DEEPAK.P Distance Vector Routing Distance vector routing is also called Distributed bellman- ford algorithm Ford-Fulkerson algorithm In distance vector routing Cost is based on Hop count Time delay No of packets in a queue. 541 DEEPAK.P Distance Vector Routing 542 DEEPAK.P Distance Vector Routing The cost of each link is set to 1. Thus, the least cost path is simply the path with the fewer hops. The table below represents each node’s knowledge about the distance to all other nodes: 543 DEEPAK.P Distance Vector Routing Initially, each node sets a cost of 1 to its directly connected neighbors and infinity to all the other nodes. Below is shown the initial routing table at node A: 544 DEEPAK.P Distance Vector Routing During the next step, every node sends a message to its directly connected neighbors. That message contains the node's personal list of distances. 545 DEEPAK.P Distance vector Routing 546 DEEPAK.P A H K J 0 24 20 21 8 A 12 36 31 28 20 A 25 18 19 36 28 I 40 27 8 24 20 H 14 7 30 22 17 I 23 20 19 40 30 I 18 A 17 31 6 31 18 H 20 0 19 12 H 21 0 14 22 10 I 9 11 7 10 0 - 24 22 22 0 6 K 29 33 9 9 15 K JA delay is 8 547 I JI delay is 10 DEEPAK.P JH delay is 12 JK delay is 6 New Routing Table for J Distance Vector Routing Problem (assume that cost is 1 for each link) 548 DEEPAK.P Link state Routing 549 DEEPAK.P Link state Routing Link state algorithms are sometimes characterized informally as each router 'telling the other router about its neighbors'. The concept has 5 parts Discover it’s neighbors and learn their network address Measure the delay or cost to each of it’s neighbors. Construct a packet telling all it has learned. Send this packet to all other routers. Compute the shortest path to every other router. 550 DEEPAK.P Link state Routing neighbor to all routers neighbor to all routers neighbor to all routers neighbor to all routers neighbor to all routers 551 DEEPAK.P neighbor to all routers Routing for Mobile Hosts 552 DEEPAK.P Routing for mobile Hosts Wireless hosts are often mobile, changing location over time This mobility of a wireless host may cause the host to connect to Different networks at different points of time. 553 DEEPAK.P CIDR 554 DEEPAK.P CIDR 555 DEEPAK.P CIDR 556 DEEPAK.P