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Introduction to Data Communications & Networking

Introduction to Data Communications & Networking. Chapter 2 Network Models (Set 2). Dr. Ali Maqousi, Dr. Tatiana Balikhina amaqousi@uop.edu.jo , tbalikhina@uop.edu.jo Department of Computer Networks Faculty of Information Technology Petra University. 1. Layered tasks.

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Introduction to Data Communications & Networking

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  1. Introduction to Data Communications & Networking Chapter 2 Network Models (Set 2) Dr. Ali Maqousi, Dr. Tatiana Balikhina amaqousi@uop.edu.jo , tbalikhina@uop.edu.jo Department of Computer Networks Faculty of Information Technology Petra University Dr.Maqousi & Dr.Balikhina 1

  2. Layered tasks • To reduce networks design complexity most networks are organised as a series of layers or levels, each one built upon one below it. • The number, name, contents, and function of each layer differ from network to network. • In all networks the purpose of each layer is to offer certain services to the higher layers. Dr.Maqousi & Dr.Balikhina

  3. The philosopher-translator-secretary architecture Dr.Maqousi & Dr.Balikhina

  4. Network Software • Protocol Hierarchies • Design Issues for the Layers • The Relationship of Services to Protocols Dr.Maqousi & Dr.Balikhina

  5. Network Software Layers, protocols, and interfaces. Dr.Maqousi & Dr.Balikhina

  6. Network Software • The rules and conventions used in the conversation between layer n on one machine with layer n on another machine are known as the layer n protocol. • A protocol is an agreement between the communicating parties on how communication is to proceed. • Between each pair of adjacent layers is an interface. The interface defines the primitive operations and services. • A set of layers and protocols is called anetwork architecture. Dr.Maqousi & Dr.Balikhina

  7. Network Software • A well-designed layered protocol system must use the following principles: • 1- Layers should be created for every level of abstraction. • 2- Every layer should perform a well-defined function. • 3- There should be a minimum of information flow between the layers. Dr.Maqousi & Dr.Balikhina

  8. Network Software • - Encapsulation is the adding of layer specific header and trailer information to each data. • Information could be control information (sequence number), sizes, times, and other control field. • At the receiving machine the data (message) move upward, from layer to layer, with header being removed as it progresses. Dr.Maqousi & Dr.Balikhina

  9. Network Software Dr.Maqousi & Dr.Balikhina

  10. The Relation of Services to Protocols • A Service is a set of primitives (operations) that a layer provides to the layer above it. • A protocol is a set of rules governing the format and meaning of the packets, or messages that are exchanged by the peer entities within a layer. • Services relate to the interfaces between layers. In contrast protocols relate to the packets sent between peer entities on different machines. Dr.Maqousi & Dr.Balikhina

  11. Layer k+1 Layer k+1 Service provided by layer k Protocol Layer k-1 Layer k-1 • The Relation of Services to Protocols Layer k Layer k Dr.Maqousi & Dr.Balikhina

  12. Network Reference Models • Two important network architectures, OSI reference model, and TCP/ IP reference model. • The protocols associated with the OSI model are rarely used, the model itself is quite general and still valid. • The TCP/ IP model itself is not of much use but the protocols are widely used. Dr.Maqousi & Dr.Balikhina

  13. Network Reference Models THE OSI MODEL The International Standards Organization (ISO) is a multinational body dedicated to worldwide agreement on international standards. An ISO standard that covers all aspects of network communications is the Open Systems Interconnection (OSI) model. It was first introduced in the late 1970s. Dr.Maqousi & Dr.Balikhina

  14. Network Reference Models Seven layers of the OSI model Dr.Maqousi & Dr.Balikhina

  15. The interaction between layers in the OSI model Dr.Maqousi & Dr.Balikhina

  16. Network Reference Models • Open System Interconnection (OSI) • When machine A (sender) wants to transfer data out to machine B (receiver), the following steps performed: • 1) The application on A generates some data in a format suitable for the application on B. • 2) A encodes the data into a network-ready format (packets) • 3) The packets are structured in frames that contain 0’s and 1’s • 4) 0’s and 1’s are transmitted through the media to B. Dr.Maqousi & Dr.Balikhina

  17. Reference Models • Open System Interconnection (OSI) • - Layers 1, 2, and 3 are network dependent. • - Layer 5, 6, and 7 are application oriented. • - Layer 4 is a transition layer between the network and application. Dr.Maqousi & Dr.Balikhina

  18. Reference Models • Open System Interconnection (OSI) • In Point-to-point layers functions are performed at each node along the path between the source and destination. • in Peer-to-peer layers functions are only performed at the source and destination. Dr.Maqousi & Dr.Balikhina

  19. LAYERS IN THE OSI MODEL In this section we briefly describe the functions of each layer in the OSI model. Physical LayerData Link Layer Network Layer Transport Layer Session Layer Presentation Layer Application Layer Dr.Maqousi & Dr.Balikhina

  20. Physical Layer Dr.Maqousi & Dr.Balikhina

  21. Physical Layer The physical layer is responsible for movements of individual bits from one hop (node) to the next over a communication channel. The physical layer is also concerned with the following: • Physical characteristicsof interfaces and medium. • Representation of bits (voltage levels for 0 or 1 bit and type of encoding). • Data rate (number of bits transmitted per second or bit duration). • Synchronization of bits (the sender and receiver must be synchronized). • Line configuration (point-to-point configuration or multipoint configuration). • Physical topology (mesh, star, bus, ring, hybrid). • Transmission mode (simplex, half-duplex, full-duplex). Dr.Maqousi & Dr.Balikhina

  22. Data Link Layer The data link layer transforms the physical layer, a raw transmission facility, to a reliable link. It makes the physical layer appear error-free to the upper layer (network layer). Dr.Maqousi & Dr.Balikhina

  23. Data Link Layer The data link layer is responsible for moving frames from one hop (node) to the next. Dr.Maqousi & Dr.Balikhina

  24. Data Link Layer Other responsibilities of the data link layer: • Framing (The sender breaks up the stream of bits obtained from network layer into data frames and transmit the frames sequentially) • Physical addressing (next hop device address). • Flow control (regulation of the rate of the sender and receiver). • Error control (Detection and retransmission of damaged or lost frames. Trailer used to achieve it). • Access control (When two or more devices are connected to the same link). Dr.Maqousi & Dr.Balikhina

  25. Network Layer The network layer ensures that each packet gets from its point of origin to its final destination, possibly across multiple networks (links). The network layer manages source-to-destination delivery of individual packets. Dr.Maqousi & Dr.Balikhina

  26. Network Layer The network layer is responsible for the delivery of individual packets from the source host to the destination host. Dr.Maqousi & Dr.Balikhina

  27. Network Layer Other responsibilities of the network layer: • Logical addressing (sender and receiver addresses). • Routing (When independent networks or links are connected to create internetworks (network of networks) or a large network, the connecting devices (called routers or switches) route or switch the packets to their final destination). Dr.Maqousi & Dr.Balikhina

  28. Network Layer • Network-layer protocols typically are routing protocols. • Routs can be based on static tables. • Routs can also be determined at the start of each conversation. • Routs can be dynamic, being determined anew for each packet, to reflect the current network load (congestions). • Examples of routing protocols: • BGP Border Gateway Protocol • OSPF Open Shortest Path First • RIP Routing Information Protocol Dr.Maqousi & Dr.Balikhina

  29. Transport Layer The transport layer is responsible for process-to-process delivery of the entire message not of individual packets. A process is an application program running on a host. Dr.Maqousi & Dr.Balikhina

  30. Transport Layer Dr.Maqousi & Dr.Balikhina

  31. Transport Layer Other responsibilities of the transport layer: • Service-point addressing (Header must include an address called a service-point address (or port address) to deliver message from sender’s running program (process) to the receivers process). • Segmentation and reassembly (Sequence numbers of segments enable the transport layer to reassemble the message correctly). • Connection control (Connectionless or connection-oriented). • Flow control (End-to-end flow control). • Error control (Here it is process-to-process error control. The sending transport layer makes sure that the entire message arrives at the receiving transport layer without error (damage, loss, or duplication). Error correction is usually achieved through retransmission). Dr.Maqousi & Dr.Balikhina

  32. Session Layer The session layer is the network dialog controller. It establishes, maintains, and synchronizes the interaction among communicating systems. Dr.Maqousi & Dr.Balikhina

  33. Session Layer Session Layer functions: • Dialog control (establishes, manages, and terminates communication session). • Synchronization (The session layer allows a process to add checkpoints, or synchronization points, to a stream of data). Dr.Maqousi & Dr.Balikhina

  34. Presentation Layer The presentation layer is concerned with the syntax and semantics of the information exchanged between two systems andresponsible for translation, compression, and encryption. The purpose of this layer is to ensure the information sent from one machine is readable to another machine. Dr.Maqousi & Dr.Balikhina

  35. Presentation Layer Presentation Layer functions: • Translation (The presentation layer at the sender changes the information (character strings, numbers, images and so on) from its sender-dependent format into a common format. The presentation layer at the receiving machine changes the common format into its receiver-dependent format). • Encryption (It is used to ensure privacy. Decryption reverses the original process to transform the message back to its original form). • Compression (Data compression reduces the number of bits contained in the information). Dr.Maqousi & Dr.Balikhina

  36. Presentation Layer • Examples of presentation-layer coding and conversion schemes: • Common data representation formats. (standard for image, sound,& video format) • Conversion schemes such as EBCDIC and ASCII. (using different text & data representation.) • Standard data compression schemes. • Standard data encryption schemes. Dr.Maqousi & Dr.Balikhina

  37. Presentation Layer • Examples of presentation-layer implementations are: • QuickTime for video and audio • MPEG for video compression and coding • GIF (Graphics Interchange Format) and JPEG (Joint Photographic Experts Group) for compressing and coding graphic images. • TIFF (Tagged Image File Format) coding format for graphic image. Dr.Maqousi & Dr.Balikhina

  38. Application Layer The application layer is responsible for providing services to the user. Dr.Maqousi & Dr.Balikhina

  39. Application Layer • The application layer contains a variety of protocols that are commonly needed by users to access the network. • Some of OSI application services are: • - File Transfer and access Management (FTAM). • - Virtual Terminal Protocol (VTP). • - Message-handling service (X.400). • - Directory service (X.500). • Some of TCP/ IP application services are: • - TELNET. • - File Transfer Protocol (FTP). • - Simple Mail Transfer Protocol (SMTP). • - Hyper Text Transfer Protocol (HTTP). Dr.Maqousi & Dr.Balikhina

  40. Summary of OSI layers Dr.Maqousi & Dr.Balikhina

  41. TCP/IP PROTOCOL SUITE The layers in the TCP/IP protocol suite do not exactly match those in the OSI model. The original TCP/IP protocol suite was defined as having four layers: host-to-network, internet, transport, and application. However, when TCP/IP is compared to OSI, we can say that the TCP/IP protocol suite is made of five layers: physical, data link, network, transport, and application. Dr.Maqousi & Dr.Balikhina

  42. TCP/IP and OSI model Dr.Maqousi & Dr.Balikhina

  43. The TCP / IP model • It consists of two main protocols; Internet Protocol (IP) and Transmission Control Protocol (TCP). • It is designed to survive loss of subnet hardware. • It has a flexible architecture to support applications with different requirements. Dr.Maqousi & Dr.Balikhina

  44. Host-to-Network Layer • The Host-to-Network Layer is the physical and data link layers. • TCP/IPdoes not define any specific protocol at this layer. • The host has to connect to the network using some protocol so it can send IP packets to it. Dr.Maqousi & Dr.Balikhina

  45. IP protocol • The Internet protocol (IP) is a key player that holds the whole architecture together. • Its job is to deliver IP packets (datagrams) where they are supposed to go. Packet routing and avoiding congestion are major issues. • Its job is similar to the mail system, where a sequence of letters are dropped into a mail box in one country, and most of them will be delivered to the correct address in the destination country. Dr.Maqousi & Dr.Balikhina

  46. IP protocol • IP is an unreliable and connectionless protocol and provides best-effortdelivery service. • The term best effort means that IP provides no error checking or tracking. • Datagrams can travel along different routes and can arrive out of sequence or be duplicated. • IP is a host-to-host protocol, meaning that it can deliver a packet from one physical device to another. Dr.Maqousi & Dr.Balikhina

  47. Transport layer in TCP/IP model • Transport level protocols responsible for delivery of a message from a process (running program) to another process (process-to-process). • it is designed to allow peer entities on the source and destination hosts to carry on a conversation. • Two main transport protocols are: • Transmission control protocol (TCP); • User datagram protocol (UDP). • A new transport layer protocol, Stream Control Transmission Protocol (SCTP), has been devised to meet the needs of some newer applications such as voice over the Internet. Dr.Maqousi & Dr.Balikhina

  48. TCP protocol • TCP is a reliable connection-oriented protocol. • TCP allows a byte stream originating on one machine to be delivered without errors to another machine. • Tasks of TCP: • 1) At the sender, TCP divides a stream of data obtained from an application into smaller units called segments. • Each segment includes a sequence number for reordering after receipt. • Segments are carried across the internet inside of IP datagrams. • At the receiving end, TCP collects each datagram as it comes in and reorders the transmission based on sequence numbers. • 2) It handles flow control. Dr.Maqousi & Dr.Balikhina

  49. UDP protocol • UDP is an unreliable connectionlessprotocol and is the simpler than TCP. • UDP is suitable for applications that don’twantTCP’s sequencing or flow control and wish to provide their own. • It adds only port addresses, checksum error control, and length information to the data from the upper layer. • UDP is used whenever the prompt delivery (without delay) is more important than accurate delivery. Dr.Maqousi & Dr.Balikhina

  50. Application layer in TCP/IP model • It contains all the higher-level protocols, it is on top of transport layer. • The application layer in TCP/IP is equivalent to the combined session, presentation, and application layers in the OSI model. • Examples of higher-level protocols are: • Virtual terminals (TELNET). • File transfer (FTP) • Electronic mail (SMTP) Dr.Maqousi & Dr.Balikhina

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