Network Access Protocols, Data Delivery - Essay Example

network and protocol processes al Affiliation) Key words: Protocols, Layers ROLE AND INTERACTION OF PROTOCOLS The interaction between x-stream server and web browser in network communication is a form of use of a protocol suit. Various protocols and standards are used in this interaction, in the process of information exchange between them. These different protocols work in coordination to ensure that the feedback are received by both parties and are understood. The examples of these protocols used are listed below: Application Protocol: The common protocol which governs the way x-stream server and clients interact is the HTTP (Hypertext Transfer Protocol). It defines the formatting and contents of the requests and replies that are exchanged between the x-stream server and the clients. HTTP is usually implemented as one of the application, for both x-stream server software and the client. This HTTP protocol, to govern the way messages are transported between the x-stream server and the client, relies on other protocols. (Hall, 2000) Transport Protocol: The transport protocol, which manages individual conversation between the x-stream servers and client, is the Transmission Control Protocol (TCP). It divides the messages of HTTP into smaller pieces, which are called segments. These segments are sent by the x-stream servers to the destination clients. TCP also controls the rate and size at which the x-stream server exchanges messages with the clients. (Hall, 2000) Internetwork Protocol: The Internet Protocol is a common internetwork protocol, which is used in x-stream. It takes the formatted segments from the TCP, to encapsulate them into packets, assigns the correct addresses and chooses best path to get to the destination host. (Forouzan & Fegan, 2006) Network Access Protocols: Physical data transmission on the media and data link management is the two primary functions, which are described by the network access protocols. Packets are taken from IP and are formatted by data-link management protocols to be transferred over the media (Gaffin, 2007).The way signals are transmitted over the media and the way they are implemented by clients governed by the protocols and standards for the physical media. The appropriate standards for the media being used are implemented by the transceivers on the network interface cards. THE OSI MODEL This model explains the processes of segmenting, encoding, and formatting and encapsulates data for transmission via a network. A data stream, which is sent to a destination, from a source, can be segregated into pieces and enclosed in messages travelling to other destinations from other hosts. At any given time, billions of such pieces of information travel over a network. Getting to the appropriate destination each piece of data containing enough identifying information is very critical. To successfully transfer the data to the appropriate destination application that runs on another host, from a source application running on one host, there must be various types of addresses, which must be included. Using this model, various addresses and identifiers, which are important at every layer, can be seen. (Black, 1991) 1. The Physical Layer The physical layer defines the interface specifications and the connector as well as the medium cable requirements. The procedural, mechanical, functional and electrical specifications are provided for sending a bit stream on a network. The components of this layer include the adapters, which connect media to physical interfaces, cabling system components, patch panel, hub and repeater specifications, connector design and pin assignments, parallel Small Computer System Interface (SCSI), wireless system components, and the Network Interface Card (NIC). The unshielded twisted pair (category 5e UTP) cable is usually used in a LAN environment for the physical layer, usually for individual device connections. In riser or vertical backbone link, fiber optic cabling is normally used for the physical layer. This layer is only part of the Local Area Network (LAN) 2. The Data Link Layer The functions provided by this layer include allowing of a device to access the network so as to send and receive messages, offering a physical address, so that a device’s data can be sent on the network, it works the networking software of the device when sending and receiving messages, and providing for error-detection capabilities. The networking components that function in this layer include Network Interface Cards (NIC), bridges, and Ethernet and token ring switches. NICs have a data-link layer or MAC address. This address is used by a switch in filtering and forwarding traffic, to help in relieving collisions and congestion on a network segment. Switches and bridges usually function in a similar manner, although, bridging is usually a software on a CPU whereas switches use ASICs (Application-Specific Integrated Circuits) in performing the task in dedicated hardware. This is much faster. (Thefaine, 1985) 3. The Network layer This layer provides end-to-end logical addressing system so that a data packet can be routed across some layer 2 networks such as token ring, frame relay, Ethernet etc. The network layer addresses are also sometimes referred to as logical addresses. The Internet Protocol (IP) address has made networks to be easily connected with one another and to set up (Huitema, 1998). IP addressing is used by the internet in providing connectivity to very many people all over the world. Routers in routing traffic between different networks use the network or subnet portion of the IP address. (Gaffin, 2007) Each router is configured specifically for the subnets or networks, which will be connected to its interfaces. Routing protocols such as Open Version of Shortest Path First (OSPF) and Routing Information Protocol (RIP) are used by routers to communicate with one another. This communication is done to calculate, based on a variety of criteria e.g. the path with the fewest routers, the best way to reach each network, and to learn of other networks, which are present. These routing decisions are made at the network layer by the routers and other networking systems. It may become necessary to adjust the outbound size of packets to one that is compatible with layer 2 protocol, which is being used, when passing them between different networks. Through the process known as fragmentation, the network layer accomplishes this. Doing of the fragmentation is usually a responsibility of a router’s network layer. At the network layer of the final destination, system is where all reassembly of fragmented packets takes place. To diagnose and report logical variations in normal network operation are the two of the additional functions of the network layer. As any network, system may initiate the network layer diagnostics, the system, which discovers the variations reports to the original packet sender for the packet, found outside the normal network operation. Content validation calculation is the exception in variation reporting. The receiver usually discards a packet without giving the report to the sender if the value sent by the originating system does not match the calculations done by the receiving system. Re-transmission is left to a higher layer’s protocol. Filtering traffic using layer 3 addressing on routers and similar devices can be a way of setting up basic security functionality. 4. The Transport Layer The transport layer offers the end-to-end communication through a network between end devices. The transport layer offers either connectionless, connection oriented or reliable best effort communications. The functions offered by the transport layer include client side entity identification, application identification, and segmentation of data for network transport. It also confirms whether the entire message arrived intact, transmission error detection, sharing of multiple sessions or multiplexing over a single physical link, realignment of segmented data on the receiving side in the correct order, establishment of both ends of virtual circuits and maintenance, and data flow control to prevent overruns. The transport layer protocols used were the connection oriented TCP (Transmission Control Protocol) and the connectionless UDP (User Datagram Protocol) (Forouzan & Fegan, 2006). 5. The Session Layer This layer provides services including keeping track of the number of bytes that each end of the session approves to have received from the other end of the session. The session layer also permits application functioning on devices to manage, establish or terminate a dialog through a network. The functions of session layer include synchronization of data flow, virtual connection between application entities, connection parameter negotiations, creation of dialog units, service partitioning into functional groups, retransmission of data that is not received by a device and acknowledgements of data received during a session. 6. The Presentation Layer The way an application formats data that is to be sent out onto the network is the major responsibility of the presentation layer. This layer allows an application to read and understand the message. The functions of the presentation layer include content translation, graphics formatting, system specific translation, encryption and decryption of a message for security purposes, and expansion and contraction of a message for efficient travelling. 7. The Application Layer An end user who is operating a device that is connected to a network is provided an interface by the application layer. This is the layer that the user sees when he loads an application. The application layer is the data that the user sees when he uses x-stream, and the examples may include the ability to print on a network, electronic mail, support for file transfers, and the ability to download files among others. TRAVERING OF DATA THROUGH THE PROTOCOL STACK Data Delivery As data is transmitted across the protocol stack on host during the encapsulation process, address identifiers are added onto the data. Just as data is prepared for transmission by multiple layers of protocols, delivery is also ensured by multiple layers of addressing. The header of layer 2 PDU, known as a frame, contains the first identifier, which is the host physical address. Layer 2 is associated with message delivery on one local network. The identifier of the receiving device on the media is represented by the layer 2 address, and is unique on the domestic network. This address is referred to as MAC (Media Access Control) in Local Area Networks using Ethernet. The frames, which are exchanged between two receiving devices communicating on a local Ethernet network, contain the source and destination MAC addresses. Layer 2 tackles information is usually removed as data is encapsulated and transfers the protocol stack into layer 3 once the destination host (Sveum, 2000) receives a frame successfully Getting data through the internetwork The primary design of level 3 protocols is to move data within an internetwork from one locale network to another locale network. Unlike layer 2 addresses, which are only meant for communication among devices on a single locale network, identifiers must be included in the layer 3 addresses to enable location of hosts on different networks by the intermediary network devices. Information about the network location of the host is contained in every IP host address in the protocol suit (Clark, 2003). The destination host address, which is usually found in the packet head, Layer 3 PDU, is read after decapsulation of the frame by an intermediary network device, which is usually a router, at the boundary of every domestic network. The routers to determine the path to use in order to arrive at the destination host then employ the network identifier portion of the address (Kirch & Dawson, 2000). The router then encapsulates the packet into a new frame, after determining the path, and sends it towards the destination to the end device. The headers of the packet and frame are then removed when the frame reaches the final destination, and the data is shifted to layer 4 (Sveum, 2000). Getting data to the right application The information, which is found in the header of PDU at layer 4, does not find a destination network or a destination host. It only identifies the specific service running or process on the end host device, which will work on the data that is being delivered. Hosts, whether servers or clients on the internet, can simultaneously run multiple network applications. At least one network process is invoked by viewing a web page, and a web browser is caused to coordinate with web servers by clicking a hyperlink. There is usually communication between individual processes that run on the original and destination host. Each service or application at layer 4 is represented by a port number. Pair of level 4 port numbers, which represents two communicating applications, is used to identify unique dialog between two devices. Therefore, the port number is used to determine the process or application that is the right destination for data, when received (Insam, 2003). REFERENCES Black, U. D. 1991. OSI: a model for computer communications standards. Englewood Cliffs, N.J.: Prentice-Hall. Clark, M. P. 2003. Data networks, IP and the Internet protocols, design and operation. Chichester, England: Wiley. Forouzan, B. A., & Fegan, S. C. 2006. TCP/IP protocol suite (3rd ed.). Boston: McGraw-Hill. Gaffin, J. C. 2007. Internet protocol 6. New York: Novinka Books. Hall, E. A. 2000. Internet core protocols the definitive guide. Cambridge, Mass.: OReilly. Huitema, C. 1998. IPv6--the new Internet protocol (2nd ed.). Upper Saddle River, NJ: Prentice Hall PTR. Insam, E. 2003. TCP/IP embedded internet applications. Amsterdam: Newnes. Kirch, O., & Dawson, T. 2000. Linux network administrators guide (2nd ed.). Beijing: OReilly. Sveum, M. E. 2000. Data communications: an overview. Upper Saddle River, N.J.: Prentice Hall. Thefaine, Y. 1985. PC protocol card: an interface to the ALAN network switch (user guide). Yorktown Heights, N.Y.: IBM Thomas J. Watson Research Center. Read More