1. TABLE OF CONTENT INTRODUCTION ROLE OBJECTIVE FUNCTION NETWORK LAYER NETWORK LAYER PROTOCOL OSI MODEL BASIC REQUIREMENT OF PROTOCOL EX:ENTHERNET PROTOCOL INTERNET PROTOCOL IPv4 BEST DELIVERY ADDRESSING PACKET STRUCTURE PACKET TRANSFER GROUPING DEVICES IN NETWORK& HIERARCHICAL ADDRESSING FUNDAMENTAL OF ROUTE,NEXT HOP,ADDRESS AND PACKET FOWARDING PROBLEM ROUTER SUMMARY

2. INTRODUCTION The protocols of the OSI model Network layer specify addressing and processes that enable Transport layer data to be packaged and transported. The Network layer encapsulation allows its contents to be passed to the destination within a network or on another network with minimum overhead. 3. ROLE Examining how it divides networks into groups of hosts to manage the flow of data packets within a network. We also consider how communication between networks is facilitated. This communication between networks is called routing. 4. OBJECTIVE Identify the role of the Network layer as it describescommunication from one end device to another enddevice. Examine the most common Network layerprotocol, Internet Protocol (IP), and its features forproviding connectionless and best-effort service. Understand the principles used to guide the division, orgrouping, of devices into networks. Understand the hierarchical addressing of devices and howthis allows communication between networks. Understand the fundamentals of routes, next-hopaddresses, and packet forwarding to a destination network. 5. FUNCTION OF NETWORK LAYER Connection model Host addressing Message forwarding 6. NETWORK LAYER PROTOCOL A communications protocol is a formal description ofdigital message formats and the rules for exchanging thosemessages in or between computing systems and intelecommunications. Protocols may include signaling, authentication and errordetection and correction capabilities. Communicating systems use well-defined formats forexchanging messages. Describes the syntax, semantics, andsynchronization of communication. 7. A programming language describes the same for computations, sothere is a close analogy between protocols and programminglanguages: protocols are to communications what programminglanguages are to computations. Protocol exists in Network Layer: IPv4/IPv6, Internet Protocol DVMRP, Distance Vector Multicast Routing Protocol ICMP, Internet Control Message Protocol IGMP, Internet Group Multicast Protocol PIM-SM, Protocol Independent Multicast Sparse Mode PIM-DM, Protocol Independent Multicast Dense Mode IPsec, Internet Protocol Security IPX, Internetwork Packet Exchange RIP, Routing Information Protocol DDP, Datagram Delivery Protocol The level of a sub-document determines the class it belongs to. Thesub-documents belonging to a class all provide similar functionalityand, when form follows function, have similar form. 8. The Network Layer is Layer 3 of the seven-layer OSI model ofcomputer networking. The Network Layer is responsible for routing packets delivery includingrouting through intermediate routers, whereas the Data Link Layer isresponsible for Media Access Control, Flow Control and ErrorChecking. The Network Layer provides the functional and procedural means oftransferring variable length data sequences from a source to adestination host via one or more networks while maintaining thequality of service functions. 9. Connection model(connectionless communication) For example, IP is connectionless, in that a frame can travelfrom a sender to a recipient without the recipient having tosend an acknowledgement.Host addressing Every host in the network needs to have a unique addresswhich determines where it is. This address will normally beassigned from a hierarchical system. 10. OSI MODEL 11. BASIC REQUIREMENT OF PROTOCOL Data formats for data exchange. In digital message bit strings are exchanged.The bit strings are divided in fields and each field carries information relevantto the protocol. Conceptually the bit string is divided into two parts called theheader area and the data area. Address formats for data exchange. The addresses are used to identify both thesender and the intended receiver(s). Address mapping. Sometimes protocols need to map addresses of one schemeon addresses of another scheme. For instance to translate a logical IP addressspecified by the application to a hardware address. Routing. When systems are not directly connected, intermediary systems alongthe route to the intended receiver(s) need to forward messages (instead ofdiscarding them) on behalf of the sender. 12. Detection of transmission errors is necessary, because no network iserror-free. Bits of the bit string become corrupted or lost. Acknowledgements of correct reception of packets by the receiver areusually used to prevent the sender from retransmitting the packets.Some protocols, notably datagram protocols like the Internet Protocol(IP), do not acknowledge. Loss of information - timeouts and retries. Sometimes packets are loston the network or suffer from long delays. To cope with this, a senderexpects an acknowledgement of correct reception from the receiverwithin a certain amount of time. Direction of information flow needs to be addressed if transmissionscan only occur in one direction at a time (half-duplex links). To gaincontrol of the link a sender must wait until the line becomes idle andthen send a message indicating its wish to do so. 13. Sequence control. We have seen that long bitstrings are divided inpieces, that are send on the network individually. The pieces may getlost on the network or arrive out of sequence, because the pieces cantake different routes to their destination. Flow control is needed when the sender transmits faster than thereceiver can process the transmissions or when the network becomescongested. Sometimes, arrangements can be made to slow down thesender, but in many cases this is outside the control of the protocol. Getting the data across is only part of the problem. The data receivedhas to be evaluated in the context of the progress of theconversation, so a protocol has to specify rules describing the contextand explaining whether the (form of the) data fits this context or not. 14. EX: ENTHERNET PROTOCOL Ethernet was invented at Xerox PARC in the early 1970s. It has gained widespread use on LANs and became standardized as IEEE standard 802.3.To connect to a LAN, a computer has to be equipped with an Ethernet network interface card. Conceptually, all stations share a single communication channel called a shared bus. Transmissions on this channel are received by all stations at (nearly) the same time. The hardware provides no indication to the sender about whether the transmission was delivered and is therefore called a best-effort delivery mechanism. Stations wanting to transmit, wait for the channel to become free and then start transmitting one single frame and then stop for a small amount of time before transmitting a next frame to allow others to transmit. 15. INTERNET PROTOCOL The Internet Protocol (IP) is the principal communications protocolused for relaying datagram (packets) across an internetwork using theInternet Protocol Suite. Responsible for routing packets across networkboundaries, it is the primary protocol that establishes the Internet. As a consequence of this design, the Internet Protocol only provides besteffort delivery and its service can also be characterized as unreliable. Innetwork architectural language it is a connection-less protocol, in contrastto so-called connection-oriented modes of transmission.The lack of reliability allows any of the following fault events to occur: data corruption lost data packets duplicate arrival out-of-order packet delivery 16. The Internet Protocol is responsible for addressinghosts and routing datagram (packets) from asource host to the destination host across one ormore IP networks. For this purpose the Internet Protocol defines anaddressing system that has two functions. Addresses identify hosts and provide a logicallocation service. 17. IPv4 Internet Protocol version 4 (IPv4) is the fourth revision in the developmentof the Internet Protocol (IP) and it is the first version of the protocol to bewidely deployed. Together with IPv6, it is at the core of standards-based internetworkingmethods of the Internet. IPv4 is still by far the most widely deployed InternetLayer protocol. As of 2011, IPv6 deployment is still in its infancy. IPv4 uses 32-bit (four-byte) addresses, which limits the address space to4,294,967,296 (232) possible unique addresses. However, some arereserved for special purposes such as private networks (~18 millionaddresses) or multicast addresses (~270 million addresses). IPv4 addresses may simply be written in any notation expressing a 32-bitinteger value, but for human convenience, they are most often written in dot-decimal notation, which consists of the four octets of the address expressedseparately in decimal and separated by periods. 18. BEST DELIVERY Best effort delivery describes a network service in which the network doesnot provide any guarantees that data is delivered or that a user is given aguaranteed quality of service level or a certain priority. Conventional telephone networks are not based on best-effort communication,but on circuit switching. During the connection phase of a new call, resourcesare reserved in the telephone exchanges, or the user is informed that the call isblocked due to lack of free capacity. The mailman will make his "best effort" to try to deliver a message, but thedelivery may be delayed if too many letters arrive to a postal office suddenly.The sender is not informed if a letter has been delivered successfully. However, the best-effort paradigm is to some extent abandoned on theInternet. Modern IP routers provide mechanisms for differentiated orguaranteed quality of service to certain data flows, based on for example theIntServ or DiffServ protocols. 19. ADDRESSING It is a common misunderstanding that addresses ending with an octet of 0 or255 can never be assigned to hosts. In glassful addressing (now obsolete with the advent of CIDR), there are onlythree possible subnet masks: Class A, 255.0.0.0 or /8; Class B, 255.255.0.0 or /16;and Class C, 255.255.255.0 or /24. However, this does not mean that every addresses ending in 255 cannot be usedas a host address. For example, in the case of a Class B subnet192.168.0.0/255.255.0.0 (or 192.168.0.0/16), equivalent to the address range192.168.0.0192.168.255.255, the broadcast address is 192.168.255.255. However, one can assign 192.168.1.255, 192.168.2.255, etc. (though this can causeconfusion). Also, 192.168.0.0 is the network identifier and so cannot beassigned, but 192.168.1.0, 192.168.2.0, etc. can be assigned (though this can alsocause confusion). 20. PACKET STRUCTUREHeader The fields in the header are packed with the most significant byte first (bigendian), and for the diagram and discussion, the most significant bits areconsidered to come first (MSB 0 bit numbering). The most significant bit isnumbered 0, so the version field is actually found in the four most significantbits of the first byte, for example.Version The first header field in an IP packet is the four-bit version field. For IPv4, thishas a value of 4 (hence the name IPv4). 21. PACKET STRUCTURE 22. GROUPING DEVICE IN NETWORK & HIERARHICALADDRESSING 23. GROUPING DEVICE IN NETWORK & HIERARHICALADDRESSING 24. GROUPING DEVICE IN NETWORK & HIERARHICALADDRESSING 25. GROUPING DEVICE IN NETWORK & HIERARHICALADDRESSING 26. FUNDAMENTAL OF ROUTER,NEXT HOP,ADDRESS & PACKET FOWARDING . 27. FUNDAMENTAL OF ROUTER,NEXT HOP,ADDRESS& PACKET FOWARDING Route assignment, route choice, or traffic assignment concernsthe selection of routes (alternative called paths) between origins anddestinations in transportation networks. It is the fourth step in theconventional transportation forecasting model, following TripGeneration, Destination Choice, and Mode Choice. The zonal interchange analysis of trip distribution provides origin-destination trip tables. Mode choice analysis tells which travelers willuse which mode. 28. PROBLEM WHEN USING MANY DEVICES IN A NETWORK The packets are passed to the router and waiting to be deployed. Host doesnt know how to deliver the data. Because the delivery of data is done by the gateway. This will result in communication problems. 29. ROUTER Process of taking a URL endpoint and decomposing it intoparameters to determine which module, controller, andaction of that controller should receive the request. Routes may be used numerous times to create a chain oruser defined application. A module name may be specified as the first path element. 30. ROUTING TABLE 31. PACKET TRANSFER USING ROUTER 32. ROUTING PROTOCOL The purpose of routing protocols is to tell thehardware between the transmitter and receiver whereto send all the pieces of a network transmission. Routing protocol shares this information first amongimmediate neighbors, and then throughout thenetwork. This way, routers gain knowledge of the topology ofthe network. 33. SUMMARY Understand the role of the network layer as it functioncommunication from one end device to another enddevice. Explain the purpose of the Hierarchical Addressing ofdevice and how this allows the communication betweennetwork. Understand the Fundamentals of Routes, Next HopAddresses and Packet Forwarding