Content Page No. Unit I Lesson 1. Introduction to Digital Communication Lesson 2. WAN Technology Lesson 3. History about TCP/IP

Transcription

1 Content Page No. Unit I Lesson 1. Introduction to Digital Communication 1.0 Aims and Objectives Introduction to Data Communication Classification of Computer Networks Topology Protocol Internetworking Technologies Let Us Sum Up Lesson-end Activity Points for Discussion Check your Progress Reference 7 Lesson 2. WAN Technology 2.0 Aims and Objectives Introduction WAN Networking Devices WAN Protocols Let us Sum Up Lesson end Activities Points for Discussion Reference 12 Lesson 3. History about TCP/IP 3.0 Aims and Objectives Introduction Internet Society Request For Comments (RFC) Let Us Sum Up Lesson End Activities Points for Discussion Check your progress Reference 16 Lesson 4. TCP/IP layer Architecture 4.0 Aims and Objectives Introduction Internet Architecture TCP/IP layer Architecture Let us Sum Up Lesson end Activities Points for Discussion 23

2 4.7 Check your progress Reference 23 Lesson 5. Network Interface 5.0 Aims and Objectives Introduction Network Interface Card Cable Type and Specification Type Other Protocols Let us Sum Up Lesson end Activities Points for Discussion Check you Progress Reference 29 Unit II Lesson 6. IP Addressing Scheme 6.0 Aims and Objectives Introduction Classful Address Special Address Classless Inter-Domain Routing (CIDR) Multihoming Let us Sum Up Lesson end Activities Points for Discussion Check your progress Reference 36 Lesson 7. ARP & RARP 7.0 Aims and Objectives Introduction Address Resolution Protocol (ARP) Reverse Address Resolution Protocol (RARP) let us Sum Up Lesson end Activities Points for Discussion Check your progress Reference 45 Lesson 8. Subnet Address and Multicast Address 8.0 Aims and Objectives Introduction Subnet Mask Multicast Addressing Let us Sum up 50

3 8.5 Lesson end Activities Points for Discussion Check your progress Reference 51 Lesson 9. Bootstrap and DHCP protocol 9.0 Aims and Objectives Introduction DHCP Let Us Sum Up Lesson and Activities Points for Discussion Check your progress Reference 54 Lesson 10. Domain Name Service (DNS) 10.0 Aims and Objectives Introduction DNS protocol Let us Sum Up Lesson end Activities Points for Discussion Check Your Progress Reference 61 Unit III Lesson 11. Internet Protocol (IP) 11.0 Aims and Objectives Introduction Datagrams Let us Sum Up Lesson end Activities Points for Discussion Check your Progress Reference 65 Lesson 12. The Internet Control Message Protocol (ICMP) 12.0 Aims and Objectives Introduction ICMP ICMP Messages Let us Sum Up Lesson end Activities 73

4 12.6 Points for Discussion Check your progress Reference 73 Lesson 13. Fragmentation and Reassembly Aims and Objectives Introduction Fragmentation and Defragmentation Let us Sum Up Lesson end Activities Points for Discussion Check your Progress Reference 77 Lesson 14. Routing 14.0 Aims and Objectives Introduction Routing Routing Protocol Vs Routed Protocol Types of routing table entries Classification of routing table Let us Sum Up Lesson end Activities Points for Discussion Check your Progress Reference 83 Lesson 15. Distance Vector Protocol and Link State Routing Protocols 15.0 Aims and Objectives Introduction Distance Vector Routing Protocols Link State Routing Protocols Routing Information Protocol (RIP) Open Shortest Path First (OSPF) Let us Sum Up Lesson end Activities Points for Discussion Check your Progress Reference 88

5 Unit IV Lesson 16. TCP and UDP Data Structures 16.0 Aims and Objectives Introduction TCP Data Structures UDP Data Structures Let us Sum Up Lesson end Activities Points for Discussion Check your Progress Reference 95 Lesson 17. TCP Finite State Machine 17.0 Aims and Objectives Introduction Algorithm for TCP state machine TCP finite state machine Let us Sum Up Lesson end Activities Points for Discussion Check your progress Reference 98 Lesson 18. TCP Connection Management 18.0 Aim and Objectives Introduction Connection Extablishment Connection Release Let us Sum Up Lesson end Activities Points for Discussion Reference 102 Lesson 19. TCP Output Processing 19.0 Aims and Objectives Introduction Timer Management Packet Loss and Retransmission Adaptive Retransmission 106

6 19.5 Flow Control TCP Keep-Alive Messages Slow Start Algorithm and Congestion Avoidance Silly Window Syndrome (SWS) Nagle Algorithm TCP Selective Acknowledgment Let us Sum Up Lesson and Activities Points for Discussion Check your Progress Reference 111 Lesson 20. Socket Programming 20.0 Aims and Objectives Introduction Domain Internet address conversion Connection less (UDP) Communication Connection oriented (TCP) Communication Let us Sum Up Lesson end Activities Points for Discussion Check your progress Reference 125 Lesson 21. Application Layer 21.0 Aims and Objectives Introduction Telnet Rlogin Let us Sum Up Lesson end Activities Points for Discussion Check your Progress Reference 135 Lesson 22. File Transfer Protocol 22.0 Aims and Objectives Introduction File transfer protocol (FTP) Trivial File Transfer protocol (TFTP) 140

7 22.4 Let us Sum Up Lesson end Activities Point for Discussion Check your Progress Reference 143 Lesson Aims and Objectives Introduction Electronic Mail Addresses Scheme TCP/IP Standard for Electronic Mail Services Simple Mail Transfer Protocol (SMTP) Post Office Protocol (POP3) Internet Message Access Protocol (IMAP) Let us Sum Up Lesson end Activities Points for Discussion Check your progress Reference 152 Lesson 24. Network Management System 24.0 Aims and Objectives Introduction Simple Network Management Protocol Let us Sum Up Lesson and Activities Point for Discussion Check Your Progress Reference 157 Lesson 25. X.25 Protocol 25.0 Aims and Objectives Introduction X.25 layers Let us Sum Up Lesson end Activities Points for Discussion Check Your Progress Reference 163

8 Unit I Lesson 1. Introduction to Digital Communication 1.0 Aims and Objectives 1.2 Introduction to Data Communication 1.2 Classification of Computer Networks 1.3 Topology 1.4 Protocol 1.5 Internetworking Technologies 1.6 Let Us Sum Up 1.7 Lesson-end Activity 1.8 Points for Discussion 1.9 Check your Progress 1.10 References 1.0 Aims and Objectives To learn the concepts which is essential for Computer Networks 1.1 Introduction to Data Communication The term telecommunication means communication at a distance. The word data refers to information presented in whatever form is agreed upon by the parties creating and using the data. Data communications are the exchange of data between two devices via some form of transmission medium such as a wire cable. Computer Network A network is a set of devices (often referred to as nodes) connected by communication links. A node can be a computer, printer, or any other device capable of sending and/or receiving data generated by other nodes on the network. Software modules in one system are used to communicate with one or more software modules in the distance System. Such interfaces across a distance are termed as peer-to-peer interfaces; and the local interfaces are termed as service interfaces. The modules on each end are organized as a sequence of functions called layers. The set of modules organized as layers is also commonly called a protocol stack.

9 Over the years, some layered models have been standardized. The ISO Open Systems Interconnection (ISO/OSI) layered model has seven layers and was developed by a set of committees under the auspices of International Standards Organization (ISO). 1.2 Classification of Computer Networks Based on Transmission Mode Transmission mode defines the direction of signal flow between two linked devices. There are three types of transmission modes. Simplex In simplex mode, the communication is unidirectional. Among the stations only one can transmit and the other can only receive. Half-Duplex In half-duplex mode, the communication is bidirectional. In this both station can sent and receive but not at the same time. Full-Duplex In Full-Duplex mode, both stations can transmit and receive simultaneously. Based on Time in Transmission Type Synchronous Transmission In synchronous Transmission both the sender and the receiver use the same time cycle for the transmission. We send bits one after another without start/stop bits or gaps. It is the responsibility of the receiver to group the bits. Bit stream is delivered with a fixed delay and given error rate. Each bit reaches the destination with the same time delay after leaving the source. Asynchronous Transmission In Asynchronous Transmission we send one start bit at the beginning and one stop bit at the end of each byte. There may be a gap between each byte. Bit stream is divided into packets. Packets are received with varying delays, so packets can arrive out of order. Some packets are not received correctly. Based on Authentication Peer to Peer Connection In peer-to-peer networks, there are no dedicated servers. All the computers are equal and, therefore, are termed as peers. Normally, each computer functions as both a client and a server. No one can control the other computers.

10 Server Based Connection Most networks have a dedicated server. A dedicated server is a computer on a network which functions as a server, and cannot be used as a client or a workstation. A dedicated server is optimized to service requests from network clients. A server can control the clients for its services. Based on Geographical location LAN (Local Area Network) Networks which cover close geographical area. LAN used to link the devices in a single office, building or campus. It provides high speeds over short distance. Systems are connecting directly to Network. The LAN is owned by private people. MAN (Metropolitan Area Network) Metropolitan area network is an extension of local area network to spread over the city. It may be a single network or a network in which more than one local area network can share their resources. WAN (Wide Area Network) WAN spread over the world may be spread over more than one city country or continent. Systems in this network are connected indirectly. Generally WAN network are slower speed than LAN s. The WAN network are owned or operated by network providers. If it is owned by a single owner then it is called Enterprise network. Often these types have combination of more than one topology. Based on Reliability Reliability is maintained by authentication. Connection-oriented This type of communication establishes a session connection before data can be sent. This method is often called a "reliable" network service. It can guarantee that data will arrive in the same order. Connection less This type of communication does not require a session connection between sender and receiver for data transfer. The sender simply starts sending packets to the destination. A connectionless network provides minimal services.

11 1.3 Topology Topology refers to physical layout including computers, cables, and other resources; it determines how components communicate with each other. Today s network designs are based on three topologies: Bus consists of series of computers connected along a single cable segment Star connects computers via central connection point or hub Ring connects computers to form a loop All computers, regardless of topology, communicate by addressing data to one or more computers and transmitting it across cable as electronic signals. Data is broken into packets and sent as electronic signals that travel on the cable. Only the computer to which the data is addressed accepts it. 1.4 Protocol Protocols mean set of rules. It is a formal description of message formats and the rules two or more machines has follow to exchange messages. The key elements of a protocol are syntax, semantics and timing. Syntax Syntax refers to the structure or format of the data, meaning the order in which they are presented. Semantics Semantics refers to the meaning of each section of bits. Timing Timing refers to when data should be sent and how fast it can be sent. 1.5 Internetworking Technologies Internetworking Technologies tell how the Internet accommodating multiple underlying hardware technologies and how they are interconnected and formed the network, and set of communication standard which the network used to interoperate. The lowercase internet means multiple networks connected together, using a common protocol suite. The uppercase Internet refers to the collection of hosts around the world that can communicate with each other using TCP/IP. While the Internet is an internet, the reverse is not true.

12 1.6 Let us Sum up Data Communication The term telecommunication means communication at a distance. Computer Network links. A network is a set of devices (often referred to as nodes) connected by communication Classification of Computer Networks Based on Transmission Mode Simplex In simplex mode, the communication is unidirectional. Half-Duplex In half-duplex mode, the communication is bidirectional. Full-Duplex In Full-Duplex mode, both stations can transmit and receive simultaneously. Based on Transmission Mode Synchronous Transmission Each bit reaches the destination with the same time delay after leaving the source. Asynchronous Transmission Packets are received with varying delays, so packets can arrive out of order. Some packets are not received correctly. Based on Authentication Peer to Peer Connection In peer-to-peer networks, there are no dedicated servers. No one can control the other computers. Server Based Connection A dedicated server is optimized to service requests from network clients. A server can control the clients for its services. Based on Geographical location LAN (Local Area Network) Networks which cover close geographical area MAN (Metropolitan Area Network) Metropolitan area network is an extension of local area network to spread over the city. WAN (Wide Area Network) WAN spread over the world may be spread over more than one city country or continent.

13 Based on Reliability Connection-oriented It can guarantee that data will arrive in the same order. Connection less This type of communication does not require a session connection between sender and receiver for data transfer. The sender simply starts sending packets to the destination. Topology Topology refers to physical layout including computers, cables, and other resources Bus consists of series of computers connected along a single cable segment Star connects computers via central connection point or hub Ring connects computers to form a loop Protocol Protocols mean set of rules Syntax Syntax refers to the structure or format of the data, meaning the order in which they are presented. Semantics Semantics refers to the meaning of each section of bits. Timing Timing refers to when data should be sent and how fast it can be sent. Internetworking Technologies Network of Inter connected Networks. 1.7 Lesson-end Activities 1. What is telecommunication? 2. What is Computer Network? 1.8 Points for Discussion 1. What are the classifications of Computer Networks.? 1.9 Check you Progress 1. What is topology? Write short notes on different topology. What are the advantages and disadvantages of this topology? 2. What is protocol? What are the elements of protocol?

14 1.10 References 1. Internetworking with TCP/IP Principles, Protocols, and Architecture Volume I, Douglas E. Comer, Prentice Hall of India Pvt. Ltd, 2. Computer Networks, Andrew S. Tanenbaum, Prentice Hall of India Pvt. Ltd. 3. Introduction to Data Communications and Networking, Behrouz Forouzan, McGraq- Hill 4. MCSE Networking Essentials Study Guide, Duncan Anderson, Tata McGraw-Hill

15 Lesson 2. WAN Technology 2.0 Aims and Objectives 2.1 Introduction 2.2 WAN Networking Devices 2.3 WAN Protocols 2.4 Let us Sum Up 2.5 Lesson end Activities 2.6 Points for Discussion 2.7 References 2.0 Aims and Objectives To learn the devices which are used in WAN To learn the Protocols which are used in WAN 2.1 Introduction LAN (Local Area Network) network spread for close geographical area. It provides high speeds over short distance. In this network all the systems must connect directly to network. In WAN (Wide Area Network) the network can be far apart. In this network systems are connected indirectly. This network generally slower speed than LAN s. Another way to connect networks is with a bridge. These connect networks at the link layer, while routers connect networks at the network layer. Bridges makes multiple LANs appear to the upper layers as a single LAN. 2.2 WAN Networking Devices Repeaters A repeater is a device that regenerates signals so that the signal can travel on addition cable segments. They do not translate or filter data. Repeater is used to connect two networks that use the same technology. It receives every data packet on each network, and retransmits it onto the other network. The net result is that the two networks have exactly the same set of packets on them. Its primary purpose is to get around limitations in cable length caused by signal loss or timing dispersion. For a repeater to function, both segments which the repeater joins must have the same media access scheme, protocol and transmission technique. Repeaters can move packets from one medium to another. Some multiport repeaters can connect different types of media. Repeaters improve performance by dividing the network into segments, thus reducing the number of computers per segment.

16 Bridge Bridge is a device that can join two LANs. However, bridge can also divide an overloaded network into separate networks, reducing the traffic on each segment and making each network more efficient. A bridge can link unlike physical media such as twisted-pair and coaxial Ethernet. It can also link unlike network segments such as Ethernet and Token Ring. A bridge can be installed internally or if the destination address is not listed in the routing table, the bridge forwards the packets to all segments. Multiple bridges can be used to combine several externally. Bridges are faster than routers because routers perform complex functions on each packet. Switches Switches allow different nodes of a network to communicate directly with each other in a smooth and efficient manner. Switches are divided into two types Store and Forward and Cut Through. Store and Forward switches stores the details and forwarded to the respective system. In the Cut through switches it just forward the details to the respective systems. Routers A router is a device used to connect networks that use different architectures and protocols. They can switch and transfer information packets across multiple networks. This process is called routing. They can determine the best path for sending data and filters broadcast traffic, to the local segment. Routers cannot link to remote computers. They can read only addressed network packets. Routers can link segments that use different data packaging and media schemes. Gateways Gateways make communication possible between systems that use different communication protocols, data formatting structures, languages and architectures. Gateways repackage data going from one system to another. Gateways are usually dedicated servers on a network and are task-specific.

17 2.3 WAN Protocols Frame Relay Frame relay is used to connect large number of sites in the network because it is relatively inexpensive to do so. The service provider gives you a frame relay circuit and is charged for the amount of data and the bandwidth you use as oppose to T1 circuit that charges with a flat monthly rate whether you use partial bandwidth or the full bandwidth regardless. Frame relay is a high performance WAN protocol that operates at the Data Link layer and the Physical layer of the OSI model. Integrated Services Digital Network (ISDN) Integrated Services Digital Network (ISDN) is designed to run over existing telephone networks. It can deliver end to end digital service carrying voice and data. ISDN operates at OSI model, physical layer, data link layer and network layer. It can carry multimedia and graphics with all other voice, data services. ISDN supports all upper layer protocols and you can choose PPP, HDLC or LAPD as your encapsulation protocol. It has two offerings, Primary rate which is 23B+D channels. 23, 64 kbps and one 64kbps mainly used for signaling. The other is the Basic Rate which has 2B+D channels two 64kbps and one 16kbps. At data link layer ISDN supports two protocols; LAPB and LAPD. LAPB is used to mainly transfer data from upper layers and has three types of frames. I-Frames carry upper layer information and carries out sequencing, flow control, error detection and recovery. S- Frames carry control information for the I-frame. LAPD provides an additional multiplexing function to the upper layers enabling number of network entities to operate over a single physical access. Each individual link procedure acts independently of others. The multiplex procedure combines and distributes the data link channels according to the address information of the frame. Each link is associated with a specific Service Access Point (SAP), which is identified in the part of the address field. High Level Data Link Control (HDLC) High Level Data Link Control (HDLC) is a bit oriented data link layer frame protocol that has many versions similar to LAP, LAPB, and LAPD. CISCO routers default encapsulation is HDLC, but it is proprietary to CISCO.

18 Point to Point Protocol (PPP) Point to Point Protocol (PPP) is a Data Link Layer protocol that can be used over ether asynchronous (dial up) or synchronous (ISDN) lines. It uses Link Control Protocol (LCP) to build and maintain data link connections. Included in PPP is the authentication protocols, PAP and CHAP, and data compression. It supports IP, IPX, AppleTalk, DECnet and OSI/CLNS. 2.4 Let us Sum Up WAN Networking Devices Repeaters A repeater is a device that regenerates signals so that the signal can travel on addition cable segments. Bridge Bridge is a device that can join two LANs. Switches Switches allow different nodes of a network to communicate directly with each other in a smooth and efficient manner. Routers A router is a device used to connect networks that use different architectures and protocols. Gateways Gateways make communication possible between systems that use different communication protocols, data formatting structures, languages and architectures. WAN Protocols Frame Relay Frame relay is used to connect large number of sites in the network because it is relatively inexpensive to do so. The service provider gives you a frame relay circuit and is charged for the amount of data and the bandwidth you use as oppose to T1 circuit that charges with a flat monthly rate whether you use partial bandwidth or the full bandwidth regardless.

19 Integrated Services Digital Network (ISDN) Integrated Services Digital Network (ISDN) is designed to run over existing telephone networks. High Level Data Link Control (HDLC) High Level Data Link Control (HDLC) is a bit oriented data link layer frame protocol that has many versions similar to LAP, LAPB, and LAPD. Point to Point Protocol (PPP) Point to Point Protocol (PPP) is a Data Link Layer protocol that can be used over ether asynchronous (dial up) or synchronous (ISDN) lines. 2.5 Lesson End Activities 1. When we need Repeater and when we need Bridge? 2. How the Gateway is different from the Router? 2.6 Points for Discussion 1. What is the difference between Switch and Hub? 2.7 Check Your Progress Write short notes on o Repeater o Bridge o Switch o Router o Gateways o ISDN and HDLC 2.8 References 1. Internetworking with TCP/IP Principles, Protocols, and Architecture Volume I, Douglas E. Comer, Prentice Hall of India Pvt. Ltd, 2. Computer Networks, Andrew S. Tanenbaum, Prentice Hall of India Pvt. Ltd. 3. Introduction to Data Communications and Networking, Behrouz Forouzan, McGraq- Hill 4. MCSE Networking Essentials Study Guide, Duncan Anderson, Tata McGraw-Hill

20 Lesson 3. History about TCP/IP 3.0 Aims and Objectives 3.1 Introduction 3.2 Internet Society 3.3 Request For Comments (RFC) 3.4 Let Us Sum Up 3.5 Lesson End Activities 3.6 Points for Discussion 3.7 Check your progress 3.8 References 3.0 Aims and Objective To learn the history about TCP/IP 3.1 Introduction TCP/IP is a set of protocols developed to allow cooperating computers to share resources across a network. In 1969 the Defense Advanced research projects Agency (DARPA) funded a research and development project to create an experimental packet switching network. This network is called ARPANET. In 1975 the ARPANET was converted from an experimental network to an operational network, and the responsibility for administering the network was given to the Defense Communication Agency (DCA). The TCP/IP protocols were adopted as Military Standards (MIL STD) in 1983, and all hosts connected to the network were required to convert to the new protocols. DARPA funded to implement TCP/IP in Berkely Unix. In 1983, the old ARPANET was divided into MILNET and smaller ARPANET. The Internet was used to refer to the entire network; MILNET and ARPANET. Advantages of TCP/IP Open protocol standards, freely available and developed independently from any specific computer hardware or operating system. A common addressing scheme which is enable to connect the most widely used networks. It may use any protocols. It connects dissimilar systems. It provides client/server framework. It provides access to the Internet

21 Differences of the OSI and TCP/IP models TCP/IP combines the presentation and session layer into its application layer. TCP/IP combines the OSI data link and physical layers into one layer. TCP/IP appears simpler because it has fewer layers. TCP/IP transport layer using UDP does not always guarantee reliable delivery of packets as the transport layer in the OSI model does. 3.2 Internet Society The Internet Society (ISOC) is a professional society to facilitate, support, and promote the evolution and growth of the Internet as a global research communications infrastructure. 3.3 Request For Comments (RFC) Documentation about TCP/IP protocols, standards, and policies are available in the online repositories without any charge. The RFC series is numbered sequentially in the chronological order RFCs are written. Even though Internet is a common public one for organizing administrative activities they have different committees. They are : Internet Architecture Board (IAB) The Internet Architecture Board (IAB) is the technical oversight and coordination body. It is composed of about 15 international volunteers from various disciplines and serves as the final editorial and technical review board for the quality of Internet standards. The IAB falls under the ISOC. Internet Engineering Task Force (IETF) The Internet Engineering Task Force (IETF) is the near-term, standards-oriented group, divided into nine areas (applications, routing and addressing, security, etc.). The IETF develops the specifications that become Internet standards. An additional Internet Engineering Steering Group (IESG) was formed to help the IETF chair. Internet Research Task Force (IRTF) The Internet Research Task Force (IRTF) pursues long-term research projects.

22 3.4 Let us Sum Up In 1969 the Defense Advanced research projects Agency (DARPA) funded a research and development project to create an experimental packet switching network. This network is called ARPANET. In 1983, the old ARPANET was divided into MILNET and smaller ARPANET. The Internet was used to refer to the entire network; MILNET and ARPANET. Request For Comments (RFC) Documentation about TCP/IP protocols, standards, and policies are available in the online repositories without any charge. The RFC series is numbered sequentially in the chronological order RFCs are written. Advantages of TCP/IP A common addressing It may use any protocols. It connects dissimilar systems. It provides client/server framework. It provides access to the Internet Internet Architecture Board (IAB) The Internet Architecture Board (IAB) is the technical oversight and coordination body.. Internet Engineering Task Force (IETF) The Internet Engineering Task Force (IETF) is the near-term, standards-oriented group, divided into nine areas (applications, routing and addressing, security, etc.). Internet Research Task Force (IRTF) The Internet Research Task Force (IRTF) pursues long-term research projects. 3.5 Lesson end Activities 1. When the TCP/IP project started and by whom? 3.6 Points for Discussion

23 1. What are the governing bodies involved in Internet Organisations? 3.7 Check your progress 1. What is the purpose of RFC? 2. Write the difference between OSI and TCP/IP layer. 3. How Internet is organized? 3.8 References 1. Internetworking with TCP/IP Principles, Protocols, and Architecture Volume I, Douglas E. Comer, Prentice Hall of India Pvt. Ltd, 2. Computer Networks, Andrew S. Tanenbaum, Prentice Hall of India Pvt. Ltd. 3. Introduction to Data Communications and Networking, Behrouz Forouzan, McGraq- Hill 4. MCSE Networking Essentials Study Guide, Duncan Anderson, Tata McGraw-Hill

24 Lesson 4. TCP/IP layer Architecture 4.0 Aims and Objectives 4.1 Introduction 4.2 Internet Architecture 4.3 TCP/IP layer Architecture 4.4 Let us Sum Up 4.5 Points for Discussion 4.6 Check your progress 4.0 Aims and Objectives To learn the architecture and layer and their functions of TCP/IP 4.1 Introduction Each layer contains logical groupings of functions that provide specific services for facilitating a communication. A function, or a group of functions, making up a functional unit is a logical entity that accepts one or more inputs (arguments) and produces a single output (value) determined by the nature of the function. Functions can be grouped in a collective unit, which is then defined as (N) layer having (N+1) layer an upper layer boundary and (N-1) layer as a lower boundary. The N layer receives services from N-1 layer and provides services to N+1 layer. 4.2 Internet Architecture A few stand-alone systems were collected together into a network. People are combining multiple networks together into an internetwork, or an internet. An internet is a collection of networks that all use the same protocol suite. The easiest way to build an internet is to connect two or more networks with a router. This is often a special-purpose hardware box for connecting networks. The following diagram shows that two networks connected and form an Internet. Figure 4.1 : Simple Internet

25 Two computers, anywhere in the world, following certain hardware, software, protocol specifications, can communicate, reliably even when not directly connected. LANs are no longer scalable beyond a certain number of stations or geographic separation. 4.3 TCP/IP layer Architecture There is no standard for layers in TCP/IP. Some refers as 5 layers including physical layer and some may refer four layers. The four layered structure of TCP/IP is seen in the way data is handled as it passes down the protocol stack from the Application Layer to the underlying physical network. Each layer in the stack adds control information to ensure proper delivery. This control information is called a header because it is placed in front of the data to be transmitted. Each layer treats all of the information it received from the layer above as data and places its own header in front of that information. The addition of delivery information at every layer is called encapsulation. When data is received each layer strips off its header before passing the data on to the layer above. Each layer has its own data structures and terminology to describe that structure. In application layer the TCP data is called stream where as in the UDP it is called message. In the transport layer the data is called segment where as in the UDP it is called packet. In the Internet layer both TCP and UDP data are called as datagrams. In the network access layer both TCP and UDP data are called frame. Application Transport Internet Network A ccess Figure 4.2 TCP/IP layers

26 Network Access layer The TCP/IP Network Access layer can encompass the functions of all three lower layers of the OSI References Model (Network, Data Link and Physical). As new hardware technologies appear new Network Access protocols must be developed so that TCP/IP networks can use the new hardware. Functions Addressing scheme For this it provide a protocol called Address Resolution Protocol (ARP) defined in the RFC Transmission of IP datagram over Ethernet network This specifies how IP datagrams are encapsulated for transmission over Ethernet networks. Header Encapsulation Figure 4.3 TCP/IP Encapsulation

27 When an application sends data using TCP, the data is sent down the protocol stack, through each layer, until it is sent as a stream of bits across the network. Each layer adds information to the data by prepending headers (and sometimes adding trailer information) to the data that it receives. Figure shows this process. The unit of data that TCP sends to IP is called a TCP segment. The unit of data that IP sends to the network interface is called an IP datagram. The stream of bits that flows across the Ethernet is called a frame. Internet layer All TCP/IP communication data are flow through IP regardless of its final destination. It provides basic packet delivery service. The important protocol in this layer is Internet Protocol defined in RFC 791. Function of Internet Protocol Defining the datagram, this is the basic unit of transmission in the Internet. Defining the Internet addressing scheme. Routing datagrams to remote hosts Performing fragmentation and reassembly of datagrams IP is a connectionless protocol. IP does not exchange control information to establish an end-to-end connection before transmitting data. It also called unreliable protocol because it contains no error detection and recovery code. Routing Datagrams Gateways are devices that switch packets between the different physical networks. Deciding which gateway to use is called routing. IP makes the routing decision for each individual packet. Internet gateways are commonly referred to IP routers because they use Internet Protocol to route packets between networks.

28 Host 1 Host 2 Application Application Transport Gateway 1 Gateway 2 Transport Internet Internet Internet Internet Network Network Network Network Network A Network B Network C Figure 4.4 Routing Through Gateways The uses of gateways are to forward packets. The hosts process packets through all four protocol layers, while the gateways process the packets only up to the Internet layer where the routing decisions are made. Fragmenting datagrams Datagrams may routed through different networks. Each type of network has a Maximum Transmission Unit (MTU), which is the largest packet that it can transfer. If the datagram received from one network may be too large to be transmitted in a single packet on a different network. In this case, IP module in a gateway is to divide the datagram into smaller pieces. This process is called fragmentation. Transport layer Transport Layer has two important protocols for connection oriented and connection less services. They are TCP and UDP. TCP (Transmission Control Protocol) provides a connectionoriented, reliable, byte stream service (RFC793). TCP is an independent, general purpose protocol that can be adapted for use with delivery systems other than IP. A stream of 8-bit bytes is exchanged across a TCP connection. UDP (User Datagram Protocol) is a simple, unreliable, datagram-oriented, transport layer protocol (RFC768).

29 Application Layer Top of the TCP/IP architecture layer is Application Layer. It contains collection of services. Each service can be identified by their number called port number. Each service is defined by separate protocol and has their separate RFC. Eg. FTP. Telnet 4.4 Let us Sum Up TCP/IP layer Architecture Network Access layer - Functions Addressing scheme Transmission of IP datagram over Ethernet network Internet layer Function of Internet Protocol Defining the datagram, this is the basic unit of transmission in the Internet. Defining the Internet addressing scheme. Routing datagrams to remote hosts Performing fragmentation and reassembly of datagrams IP is a connectionless protocol Routing Datagrams Gateways are devices that switch packets between the different physical networks. Deciding which gateway to use is called routing. Fragmenting datagrams Datagrams. Each type of network has a Maximum Transmission Unit (MTU), which is the largest packet that it can transfer. If the datagram received from one network may be too large to be transmitted in a single packet on a different network. In this case, IP module in a gateway to divide the datagram into smaller pieces. This process is called fragmentation. Transport layer TCP (Transmission Control Protocol) provides a connection-oriented, reliable, byte stream service. UDP (User Datagram Protocol) is a simple, unreliable, datagram-oriented, transport layer protocol (RFC768). Application Layer Top of the TCP/IP architecture layer is Application Layer. It contains collection of services.

30 4.5 Lesson end Activities 1. What is the purpose of Internet Architecture Board? 4.6 Points for Discussion 1. What is Header Encapsulation and Decapsulation? 4.7 Check your Progress 1. What are layers available in TCP/IP? 2. What is the function of Network layer? 3. What is the function of IP layer? 4. What is the function of Transport layer? 4.8 References 1. Internetworking with TCP/IP Principles, Protocols, and Architecture Volume I, Douglas E. Comer, Prentice Hall of India Pvt. Ltd, 2. Computer Networks, Andrew S. Tanenbaum, Prentice Hall of India Pvt. Ltd. 3. Introduction to Data Communications and Networking, Behrouz Forouzan, McGraq- Hill 4. MCSE Networking Essentials Study Guide, Duncan Anderson, Tata McGraw-Hill

31 5.0 Aims and Objectives 5.1 Introduction 5.2 Network Interface Card 5.3 Cable type and Specification Type 5.4 Other Protocols 5.5 Let us Sum Up 5.6 Lesson end Activities 5.7 Points for Discussion 5.8 Check you Progress 5.9 References Lesson 5. Network Interface 5.0 Aims and Objectives To learn about Network interface Device and their function 5.1 Introduction The purpose of the network interface layer is it handles the details of the communication media (Ethernet, token ring, etc.) 5.2 Network Interface Card A network interface card is used to connect a computer to an Ethernet network. The card (shown in the figure below) provides an interface to the media. This may be either using an external transceiver (as shown) or through an internal integrated transceiver mounted on the network interface card PCB. The card usually also contains the protocol control firmware and Ethernet Controller needed to support the Medium Access Control (MAC) data link protocol. Figure 5.1 Network Interface Card (NIC)

32 The Ethernet Most of our networks these days use Ethernet also called Network Interface Card(NIC). Ethernet has its own Addressing scheme. No two machines have the same Ethernet address. This is a unique number issued by IEEE to the manufacturer. So each Ethernet controller comes with an address built in from the factory. The address consists of 48 bits. First 24 bits represents the vendor and next 24 bits represents the serial number of the NIC card. This hardware address is used by the Media Access Control (MAC) layer of the Data Link layer to identify uniquely, the LAN device, to the network layer. Ethernet equipment manufacturers have to register with a central authority, to make sure that the numbers they assign don't overlap any other manufacturer. Ethernet is a "broadcast medium". When you send a packet out on the Ethernet, every machine on the network sees the packet. So something is needed to make sure that the right machine gets it. Every Ethernet packet has a 14-octet header that includes the source and destination Ethernet address, and a type code. Figure 5.2 Ethernet Data format Each machine is supposed to pay attention only to packets with its own Ethernet address in the destination field. Each machine has to have a table of what Ethernet address corresponds to what Internet address. In addition to the addresses, the header contains a type code. The type code is to allow for several different protocol families to be used on the same network. So you can use TCP/IP, DECnet, Xerox NS, etc., at the same time. Each of them will put a different value in the type field. Finally, there is a checksum. The Ethernet controller computes a checksum of the entire packet. When the other end receives the packet, it recomputes the checksum, and throws the packet away if the answer disagrees with the original. The checksum is put on the end of the packet, not in the header. The original Ethernet was developed as an experimental coaxial cable network in the 1970s by Xerox Corporation to operate with a data rate of 3 Mbps using a carrier sense multiple access

33 collision detect (CSMA/CD) protocol for LANs with sporadic but occasionally heavy traffic requirements. IEEE Specification for Ethernet Ethernet LAN specification 802.3u Fast Ethernet 802.3z Gigabit Ethernet Ethernet card is an add on card which needed for the computers which connected to the network. Computers which used as a stand alone system need not have Ethernet card. The following figure shows the sample Ethernet card. Figure 5.3 Ethernet Card 5.3 Cable type and Specification Type Ethernet support different types of cables, each have their own specification and transmission distance. These are given in the following table.

34 S pecification 10BaseT 10Base2 10Base5 10BaseF 100BaseT 100BaseTX C ab le T ype U nshielded T w isted P air T hin C oaxial T hick C oaxial Fiber O ptic U nshielded T w isted P air U nshielded T w isted P air M axim u m len gth 100 m eters 185 m eters 500 m eters 2000 m eters 100 m eters 220 m eters 5.4 Other Protocols Serial Line IP (SLIP) SLIP stands for Serial Line IP. It is a simple form of encapsulation for IP datagrams on serial lines, and is specified in RFC SLIP has become popular for connecting home systems to the Internet, through the ubiquitous RS-232 serial port found on almost every computer and high-speed modems. Point-to-Point Protocol (PPP) PPP, the Point-to-Point Protocol, corrects all the deficiencies in SLIP. PPP consists of three components. A way to encapsulate IP datagrams on a serial link. PPP supports either an asynchronous link with 8 bits of data and no parity (i.e., the ubiquitous serial interface found on most computers) or bit-oriented synchronous links. A link control protocol (LCP) to establish, configure, and test the data-link connection. This allows each end to negotiate various options. A family of network control protocols (NCPs) specific to different network layer protocols. RFCs currently exist for IP, the OSI network layer, DECnet, and AppleTalk. The IP NCP, for example, allows each end to specify if it can perform header compression, similar to CSLIP. RFC 1548 [specifies the encapsulation method and the link control protocol. RFC 1332 specifies the network control protocol for IP.

35 Loopback Interface Most implementations support a loopback interface that allows a client and server on the same host to communicate with each other using TCP/IP. The class A network ID 127 is reserved for the loopback interface. By convention, most systems assign the IP address of to this interface and assign it the name localhost. An IP datagram sent to the loopback interface must not appear on any network. 5.5 Let Us Sum Up Network Interface Card A network interface card is used to connect a computer to an Ethernet network. The card (shown in the figure below) provides an interface to the media. IEEE Specification for Ethernet Ethernet LAN specification 802.3u Fast Ethernet 802.3z Gigabit Ethernet Serial Line IP (SLIP) SLIP stands for Serial Line IP. It is a simple form of encapsulation for IP datagrams on serial lines Loopback Interface Most implementations support a loopback interface that allows a client and server on the same host to communicate with each other using TCP/IP. 5.6 Lesson end Activities Discuss different type of Cable types. 5.7 Points to Discussion How Ethernet card is connected to the PC? 5.8 Check your progress 1. What is the purpose of Network Interface card? 2. How Ethernet is working?

36 (or) Explain the functionality of Ethernet with a neat figure. 3. Write Short Notes on: a) SLIP, b) PPP 5.9 References 1. Internetworking with TCP/IP Principles, Protocols, and Architecture Volume I, Douglas E. Comer, Prentice Hall of India Pvt. Ltd, 2. Computer Networks, Andrew S. Tanenbaum, Prentice Hall of India Pvt. Ltd. 3. Introduction to Data Communications and Networking, Behrouz Forouzan, McGraq- Hill 4. MCSE Networking Essentials Study Guide, Duncan Anderson, Tata McGraw-Hill

37 Unit II Lesson 6. IP Addressing Scheme 6.0 Aims and Objectives 6.1 Introduction 6.2 Classful Address 6.3 Special Address 6.4 Classless Inter-Domain Routing (CIDR) 6.5 Multihoming 6.6 Let us Sum Up 6.7 Lesson end Activities 6.8 Points for Discussion 6.9 Check your progress 6.10 References 6.0 Aims and Objectives To learn the TCP/IP addressing schemes 6.1 Introduction There are three types of IP addresses: unicast (destined for a single host), broadcast (destined for all hosts on a given network), and multicast (destined for a set of hosts that belong to a multicast group). IP Addressing Scheme Universal Service - all computers on all physically different networks can communicate. Physical addresses - allow communication between computers on one network. The IP address - provides virtual addressing. The address is software controlled, whereas the address for the network card is hardware based. The IP addressing scheme is quite complex, and there have been many revisions to the IP scheme. The IANA, InterNIC, and ARIN work together to subdivide and issue addresses for Internet clients. You can subdivide addresses assigned by InterNIC. Routing tables can be created manually and dynamically. IP addressing schemes allows for seamless integration amongst heterogeneous networks. To send a packet, the destination IP address of the computer is used not the hardware address. This allows for communication across networks.

38 The IP address is 32 bits in length (IPv4) and contains sequence of 1s and 0s. The IP addresses are divided into a prefix and suffix. The suffix is the host address. The prefix is the network number. The address space of IPv4 is 232 or 4,294,967, Classful Address In classful addressing, the address space is divided into five classes: A, B, C, D, and E to define large, medium, and small networks. The Class D address class was created to enable multicasting. IETF reserves Class E addresses for its own research. To make the IP address easier to use, the address is usually written as four decimal numbers separated by periods. This way of writing the address is called the dotted decimal format. Eg. Numbers through It is much better than reading Dotted-decimal notation and binary notation for an IPv4 address shown in the following diagram: Figure 6.1 Dotted decimal notation and binary notation

39 Dotted Decimal with Classes Figure 6.2 Classes in binary and dotted-decimal notation Class A: 1 prefix octet (128 networks) 3 suffix octets ( hosts) Class B: 2 prefix octets (16384 networks) 2 suffix octets (65536 hosts) Class C: 3 prefix octets ( networks) 1 suffix octet (256 hosts) Number of blocks and block size in classful IPv4 addressing shown bellow: Figure 6.3 Classful address block size No two machines that connect to a public network can have the same IP address because public IP addresses are global and standardized. A central authority exists for IP address

40 delegation. In the US, it s ARIN American Registry for Internet Numbers. People just can t arbitrarily use any IP network if their network is publicly accessible. That would lead to routing conflicts. Classful addressing, which is almost obsolete, is replaced with classless addressing. The first address in a block is normally not assigned to any device; it is used as the network address that represents the organization to the rest of the world. The first address in the block can be found by setting the rightmost 32 n bits to 0s. The last address in the block can be found by setting the rightmost 32 n bits to 1s. The number of addresses in the block can be found by using the formula 232 n. Private IP addresses Private IP addresses are a solution to the problem of the exhaustion of public IP addresses. Addresses that fall within these ranges are not routed on the Internet backbone. It is described in RFC (Full Class A) (16 Class B s) (Full Class B) Figure 6.4 Private classful address and their ranges 6.3 Special Address Network addresses 0 and 127 are reserved for special uses. Network 0 designates the default route. The default route is used to simplify the routing information that IP must handle. Network address 127 is loop back address. The loop back address simplifies network applications by allowing the local host to be addressed in the same manner as remote host. An IP address with all bits set to one is a broadcast address. A broadcast address is used to simultaneously address every host on a network.