Report of TCP/IP


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Report of TCP/IP

  1. 1. OSI ModelIntroduction:-The Open Systems Interconnection (OSI) model is a reference tool for understandingdata communications between any two networked systems. It divides the communications processesinto seven layers. Each layer both performs specific functions to support the layers above it andoffers services to the layers below it. The three lowest layers focus on passing traffic through thenetwork to an end system. The top four layers come into play in the end system to complete theprocess.The main benefits of the OSI model include the following:- Helps users understand the big picture of networking. Helps users understand how hardware and software elements function together. Makes troubleshooting easier by separating networks into manageable pieces. Defines terms that networking professionals can use to compare basic functional relationships on different networks. Helps users understand new technologies as they are developed. Aids in interpreting vendor explanations of product functionality. Seven Layers:- 1.) Application Layer 2.) Presentation Layer 3.) Session Layer 4.) Transport Layer 5.) Network Layer 6.) Data link Layer 7.) Physical Layer 1
  2. 2. Layer 1 - The Physical Layer:-Physical Layer is responsible for transmitting row bit stream over the physical cable. The physicallayer defines the hardware items such as cables, cards, voltages etc.Components of the physical layer include:- Cabling system components Adapters that connect media to physical interfaces Connector design and pin assignments Hub, repeater, and patch panel specifications Wireless system components Parallel SCSI (Small Computer System Interface) Network Interface Card (NIC)Functions:-The physical layer, the lowest layer of the OSI model, is concerned with the transmission andreception of the unstructured raw bit stream over a physical medium. It describes theelectrical/optical, mechanical, and functional interfaces to the physical medium, and carries thesignals for all of the higher layers. It provides: Data encoding: modifies the simple digital signal pattern (1s and 0s) used by the PC to better accommodate the characteristics of the physical medium, and to aid in bit and frame synchronization. It determines: o What signal state represents a binary 1 o How the receiving station knows when a "bit-time" starts o How the receiving station delimits a frame Physical medium attachment, accommodating various possibilities in the medium: o Will an external transceiver (MAU) be used to connect to the medium? o How many pins do the connectors have and what is each pin used for? Transmission technique: determines whether the encoded bits will be transmitted by baseband (digital) or broadband (analog) signaling. 2
  3. 3. Physical medium transmission: transmits bits as electrical or optical signals appropriate for the physical medium, and determines: o What physical medium options can be used o How many volts/db should be used to represent a given signal state, using a given physical mediumLayer 2 - Data link Layer:-Data link layer is responsible for controlling the error between adjacent nodes and transfer the framesto other computer via physical layer. Data link layer is used by hubs and switches for their operation.Components of the Data link layer include:- Network interface cards Ethernet and Token Ring switches BridgesFunctions:-The data link layer provides error-free transfer of data frames from one node to another over thephysical layer, allowing layers above it to assume virtually error-free transmission over the link. Todo this, the data link layer provides: Link establishment and termination: establishes and terminates the logical link between two nodes. Frame traffic control: tells the transmitting node to "back-off" when no frame buffers are available. Frame sequencing: transmits/receives frames sequentially. Frame acknowledgment: provides/expects frame acknowledgments. Detects and recovers from errors that occur in the physical layer by retransmitting non-acknowledged frames and handling duplicate frame receipt. Frame delimiting: creates and recognizes frame boundaries. Frame error checking: checks received frames for integrity. Media access management: determines when the node "has the right" to use the physical medium. 3
  4. 4. Layer 3 - The Network Layer:-This layer is responsible for translating the logical network address and names into their physicaladdress. This layer is also responsible for addressing, determining routes for sending and managingnetwork problems such as packet switching, data congestion and routines.Functions:-The network layer controls the operation of the subnet, deciding which physical path the data shouldtake based on network conditions, priority of service, and other factors. It provides: Routing: routes frames among networks. Subnet traffic control: routers (network layer intermediate systems) can instruct a sending station to "throttle back" its frame transmission when the routers buffer fills up. Frame fragmentation: if it determines that a downstream routers maximum transmission unit (MTU) size is less than the frame size, a router can fragment a frame for transmission and re-assembly at the destination station. Logical-physical address mapping: translates logical addresses, or names, into physical addresses. Subnet usage accounting: has accounting functions to keep track of frames forwarded by subnet intermediate systems, to produce billing informationLayer 4 - The Transport Layer:-This layer is responsible for end-to-end delivers of messages between the networked hosts. It firstdivides the streams of data into chunks or packets before transmission and then the receivingcomputer re-assembles the packets. It also guarantees error free data delivery without loss orduplications.Functions:-The transport layer ensures that messages are delivered error-free, in sequence, and with no losses orduplications. It relieves the higher layer protocols from any concern with the transfer of data betweenthem and their peers. 4
  5. 5. The size and complexity of a transport protocol depends on the type of service it can get from thenetwork layer. For a reliable network layer with virtual circuit capability, a minimal transport layer isrequired. If the network layer is unreliable and/or only supports data grams, the transport protocolshould include extensive error detection and recovery.The transport layer provides: Message segmentation: accepts a message from the (session) layer above it, splits the message into smaller units (if not already small enough), and passes the smaller units down to the network layer. The transport layer at the destination station reassembles the message. Message acknowledgment: provides reliable end-to-end message delivery with acknowledgments. Message traffic control: tells the transmitting station to "back-off" when no message buffers are available. Session multiplexing: multiplexes several message streams, or sessions onto one logical link and keeps track of which messages belong to which sessions (see session layer).Layer 5 - The Session Layer:-This layer is responsible for establishing the process-to-process communication between the hosts inthe network. The interactive login is an example of services provided by this layer in which theconnective is re-connected in care of any interruption.Functions:-The session layer allows session establishment between processes running on different stations. Itprovides: Session establishment, maintenance and termination: allows two application processes on different machines to establish, use and terminate a connection, called a session. Session support: performs the functions that allow these processes to communicate over the network, performing security, name recognition, logging, and so on. 5
  6. 6. Layer 6 - The Presentation Layer:-The Presentation layer is responsible for protocol conversion, date encryption/decryption, Expandinggraphics command and the date compression. This layer makes the communications between twohosts possible.Functions:-The presentation layer formats the data to be presented to the application layer. It can be viewed asthe translator for the network. This layer may translate data from a format used by the applicationlayer into a common format at the sending station, and then translate the common format to a formatknown to the application layer at the receiving station.The presentation layer provides: Character code translation: for example, ASCII to EBCDIC. Data conversion: bit order, CR-CR/LF, integer-floating point, and so on. Data compression: reduces the number of bits that need to be transmitted on the network. Data encryption: encrypt data for security purposes. For example, password encryption.Layer 7 - The Application Layer:-The application layer provides different services to the application. Example of services provided bythis layer is file transfer, electronic messaging e-mail, virtual terminal access and networkmanagement.Functions:-The application layer serves as the window for users and application processes to access networkservices. This layer contains a variety of commonly needed functions: Resource sharing and device redirection Remote file access Remote printer access Inter-process communication Network management Directory services 6
  7. 7. Electronic messaging (such as mail) Network virtual terminals TCP/IP ModelIntroduction:-The OSI model describes computer networking in seven layers. While there havebeen implementations of networking protocol that use those seven layers, most networks today useTCP/IP. But, networking professionals continue to describe networking functions in relation to theOSI layer that performs those tasks. The TCP/IP model uses four layers to perform the functions ofthe seven-layer OSI model.The four layers of the TCP/IP architecture can be compared to certain levels of the OSI model. It’simportant to know what each level of the TCP/IP protocol architecture does, and how these layersmap to the OSI model. The Application Layer of the TCP/IP model performs much the same tasks asthe Application, Presentation, and Session layers of the OSI model. The Transport layer in theTCP/IP architecture is similar to the Transport layer in the OSI model. This layer can use TCP orUDP as well. The TCP/IP model uses four layers to perform the functions of the seven-layer OSImodel. 7
  8. 8. Four Layers:- 1.) Application Layer 2.) Transport Layer 3.) Internet Layer 4.) Network LayerLayer 1-Application Layer:-The Application Layer in TCP/IP groups the functions of OSI Application, Presentation Layer andSession Layer. Therefore any process above the transport layer is called an Application in theTCP/IP architecture. In TCP/IP socket and port are used to describe the path over which applicationscommunicate. Most application level protocols are associated with one or more port number.Functions:- Refers to standard network services like http, ftp, telnet as well as communication methods used by various application programs Also defines compatible representation of all dataLayer 2-Transport Layer:-In TCP/IP architecture, there are two Transport Layer protocols. The Transmission Control Protocol(TCP) guarantees information transmission. The User Datagram Protocol (UDP) transports datagramwithout end-to-end reliability checking. Both protocols are useful for different applications.Functions:- Manages the transfer of data by using connection oriented (TCP) and connectionless (UDP) transport protocols Manages the connections between networked applicationsLayer 3-Internet Layer:-The Internet Protocol (IP) is the primary protocol in the TCP/IP Network Layer. All upper and lowerlayer communications must travel through IP as they are passed through the TCP/IP protocol stack. 8
  9. 9. In addition, there are many supporting protocols in the Network Layer, such as ICMP, to facilitateand manage the routing process.Functions:- Manages addressing of packets and delivery of packets between networks Fragments packets so that they can be dealt with by lower level layer (Network Interface layer Network)Layer 4-Network Layer:-In the TCP/IP architecture, the Data Link Layer and Physical Layer are normally grouped together tobecome the Network Access layer. TCP/IP makes use of existing Data Link and Physical Layerstandards rather than defining its own. Many RFCs describe how IP utilizes and interfaces with theexisting data link protocols such as Ethernet, Token Ring, FDDI, HSSI, and ATM. The physicallayer, which defines the hardware communication properties, is not often directly interfaced with theTCP/IP protocols in the network layer and above.Functions:- Delivers data via physical link (Ethernet is the most common link level protocol ) Provides error detection and packet framing Difference between OSI Model and TCP/IP ModelThe Internet Protocol Suite also known as TCP/IP is the set of communicationsprotocols used for the Internet and other similar networks. It is named from two ofthe most important protocols in it: the Transmission Control Protocol (TCP) andthe Internet Protocol (IP), which were the first two networking protocols definedin this standard. IP networking represents a synthesis of several developments thatbegan to evolve in the 1960s and 1970s, namely the Internet and LANs (LocalArea Networks), which emerged in the mid- to late-1980s, together with theadvent of the World Wide Web in early 1990s.The Internet Protocol Suite, like many protocol suites, may be viewed as a set oflayers. Each layer solves a set of problems involving the transmission of data, and 9
  10. 10. provides a well-defined service to the upper layer protocols based on usingservices from some lower layers. Upper layers are logically closer to the user anddeal with more abstract data, relying on lower layer protocols to translate data intoforms that can eventually be physically transmitted.The main difference in two models is:- The OSI model consists of 7 architectural layers whereas the TCP/IP only has 4 layers. OSI is a reference model and TCP/IP is an implementation of OSI model. TCP/IP Protocols are considered to be standards around which the internet has developed. The OSI model however is a "generic, protocol-independent standard." . TCP/IP combines the presentation and session layer issues into its application layer. TCP/IP combines the OSI data link and physical layers into the network access layer. TCP/IP appears to be a simpler model and this is mainly due to the fact that it has fewer OSI Model TCP/IP Model1 OSI stand for the open system TCP/IP stands for transmission control interconnection. It is called because of it protocol/internet protocol. It is named allows any two different systems to after these two protocols, being part of communicate regardless of their this model architecture.2 OSI model has seven layers physical, TCP/IP Model has four layers host-to- data link, network, transport session network layer, network transport and presentation and application layer application layer3 Session and presentation layers are Session and presentation layers are not present in this model present in this model4 This model provides clear distinction This model does not provides clear between services, interfaces and distinction between services, interfaces protocols and protocols5 In this model protocols does not fit well In this model protocols fits well in to the in to the model model 10
  11. 11. 6 OSI model supports both connection and TCP/IP model supports only connectionless oriented communication connectionless communication in in network layer network layer 11