Computer Communications and Networks - Report Example

? [Computer Communication & Networks] Communication of home computer with the X stream In this report, we will discuss the communication of networks in each layer of the TCP/IP model. Likewise, we will also address the Open System Interconnection (OSI) model where relevant. Each layer will demonstrate the methods, processes and technologies that are associated with accessing the X stream server from a home computer. Moreover, in this scenario, we have assumed that the home computer is connected with an ADSL connection from an ISP with a Client premises equipment (CPE) named as ADSL router. What is a TCP/IP Model? Before discussing the communication in networks from the home computer to the X stream, we have to first discuss the TCP/IP model. As illustrated in the Figure 1.1, we can see the comparison of both OSI model and the TCP/IP model. The TCP/IP model is associated with Application layer, Transport layer, Internet Layer and Data link Layer. Likewise, application layer of the TCP/IP model is associated with protocols such as Simple Mail Transfer Protocol (SMTP), Hyper Text Transfer Protocol (HTTP), File Transfer Protocol (FTP) etc. The transport Layer is associated with protocols such as Transmission Control Protocol (TCP), User Datagram Protocol (UDP) etc. The Internet layer is associated with Internet Protocol (IP), Address Resolution Protocol (ARP), Internet Control Message Protocol (ICMP) and lastly, the data link layer that is also called the Network interface layer is associated with Ethernet, token ring etc. for accessing the X stream from a remote location, we will discuss the insights of these five layers of the TCP/IP model. Moreover, Figure 1 also illustrates the resemblance of each layer of TCP/IP to the OSI model. Figure 1 TCP/IP and OSI Model Image retrieved from: (Clarke, n.d) Figure 1.2, demonstrates the functionality of each layer in order to exchange data from the home computer and the X stream server. The application layer will use FTP, HTTP, SMTP for initiating request and forwarding it to the next layer i.e. the transport layer. The transport layer builds the header and data before sending it via TCP or UDP. Likewise, the next layer i.e. the network layer assigns the IP address for transmitting the data to the relevant Ethernet that is located at the network access layer. The network access layer than links the transmission to the required segment from the same layer as shown in Figure 1.2 Figure 1.2 Example demonstration via TCP/IP Model Protocol Layering Up till now we have discussed the TCP/IP model, protocols and functions associated with each layer. Protocol layering will demonstrate the functionality of each layer after another along with Protocol Data Units (PDU’s) and packet headers while connecting to the X stream from home computer. Considering the four layers of the TCP/IP model, we will discuss four PDU’s on each layer, as shown in Figure 2, the message initiates from the application layer four of the TCP/IP model. The four PDU’s are 1-PDU, 2-PDU, 3-PDU and 4-PDU. Figure 2 Image retrieved from (James F. Curose & Keith W. Ross, 2000) The layer 4 that is an application layer and considered as a high layer, constructs a message M that is composed of various parameters that needs to be tailored by the application criteria. Likewise, a typical packet may include parameters such as message type and associated data. The packet from the home computer is transmitted in the form of Message M to the third layer of the TCP/IP protocol stack, as shown in Figure 2. Likewise, layer three of the source (Home Computer) breaks the 4-PDU in to two separate parts as M1 and M2. Accordingly, the layer three of the source (Home Computer) integrates with the two separate parts M1 and M2 called as headers that contributes for constructing 3-PDU into two separate parts. Headers are associated with the information that is a requirement for the source and destination on the third layer for enabling services on layer four (James F. Curose & Keith W. Ross, 2000). Likewise, the development continues for the source (Home Computer) and adds up headers while passing through each layer till the end i.e. creation of 1- PDU. As the 1-PDU is created, it is now ready to transmit from the home computer to the X stream from the physical layer of the OSI. The destination (X stream) end receives 1-PDU from the source (Home Computer) and route the request to the protocol stack, as at each layer, identical headers are eliminated. Finally, message M1 is established again from M1 and M2 and transmitted to the destination (X stream) (James F. Curose & Keith W. Ross, 2000). Network Access Layer The network access layer is associated with the data link layer and physical layer in order to establish the connectivity of the home computer via wired or wireless carrier to transmit data to the X stream server. However, there are several carriers available today for establishing and transmitting data. Few of them are Broadband, ATM, Delay tolerant Networks, Public Switched Telephone Networks, Global systems for mobile communication etc. As we will demonstrate the connectivity of the home computer via ADSL connection, we will consider the DSL physical architecture. However a prerequisite for a ADSL connection, requires the telephone exchange of that particular region to be digital. As ADSL connection requires digital end to end connectivity, local telephone exchanges known as (PSTN) are now capable of supporting digital transmission. The home computer will establish connectivity via a ADSL router that is considered as a Client Premises Equipment (CPE). The DSL router established connection from a DSLAM known as the ?“DSL Access Multiplexor, A central office (CO) device for ADSL service that intermixes voice traffic and DSL traffic onto a customer's DSL line. It also separates incoming phone and data signals and directs them onto the appropriate carrier's network” (Dslam. 2011). The DSLAM is located at the exchange and is connected by the router. There may be more than one DSLAM’s in the exchange, as more than one Internet service providers are available. Depending on the model and type, DSLAM contains cards that are inserted in the slots just like the PCI slots in the home computer. Moreover, these cards have ports that are used to tag the telephone line of the customers in order to provide ADSL service from the telephone exchange. Figure 3 Physical ADSL Architecture Image retrieved from http://www.gis.net/~sotis/dslexp.html Figure 3 shows the association of each device that plays its role to establish connectivity. We will not discuss each component of the ADSL architecture, as the Internet backbone connects with the ISP. The physical layer summarized the connectivity from the home user to the X stream server includes the ADSL router, as the first component. Likewise, the request relays from the Main distribution frame to the DSLAM. The DSLAM redirects the traffic to the Internet backbone router for redirecting it to the ISP. The backbone router than forwards the request to the relevant network i.e. X stream network / server. The association of the data link layer with the Network access layer sends a frame from the physical Internet connection via a transmission adapter. Likewise, the transmitting adapter sends the transmission from the home network that is received from the receiving adapter from the X stream network. The location of these adapters is located at the sending and receiving of both nodes. Moreover, (James F. Curose & Keith W. Ross, 2000) the data link layer also provides link accessibility and framing capability led by reliability of transmission and flow control. Furthermore, it also supports error correction and control in full or half duplex modes. Network Layer Network layer includes logical addressing that is required to relay transmission to the legitimate destination or host. This is the job of the router that is considered to be an intelligent device capable of taking routing decisions. Data packet is received and transmitted to the internetwork by routers using IP addresses. Routers utilize several routing protocols to update the routing database along the path. Home computer will use a Routing Information Protocol (RIP) to transmit the routing details for the particular connection request. The router on the first hop will decide which routing protocol to use, as per configuration settings. Likewise, Open shortest path first (OSPF) is used to determine the shortest and traffic free path and Border Gateway Protocol (BGP) is also used for exchanging routing details from router to router to keep the routing table updated. Figure 4 shows all the parameters for an IPv4 IP packet header. The packet header includes 32 bit source and destination address, version, IHL, ToS, Size, Identification, FLAGS, Fragment Offset, TTL, Protocol, Checksum and other options. As IP is absolute vital for establishing connectivity on the LAN, WAN and MAN, network layer is responsible for forwarding the connection request in order to access the X stream server from a sophisticated world of computer networks and devices. Moreover, this layer also provides the encapsulation for data grams with reconstruction and data packet fragmentation. Furthermore, analyzing and handling errors to ensure reliable connectivity is also a role of this layer. Figure 4 IPv4/IPv6 Packet Header Image retrieved from (Morrow, Vijayananda,n.d) Transport Layer Transport layer is constructed on two core protocols i.e. TCP and UDP. The transport layer extracts the input from the session layer for passing the connection to the network layer. However, in the transport layer, connection can be broken down in to two channels (if required). Likewise, the TCP due to its characteristics of a connection oriented protocol ensures sustainability of the connection along with error correction. Whereas, the UDP possessing characteristics of a connection less protocol, does not ensure sustainability or error correction. However, it is effective for high quality videos and voice communication that can still continue if any packet damages during the transmission. Some of the examples for UDP are VoIP based applications that also supports video streaming from a web cam at the same time. Application Layer Application layer is physical present at the screen of the computer i.e. users can interact with it, configure it, manage it and customize it according to the requirements. File transfer Protocol (FTP), Domain Name System (DNS), Routing Information Protocol (RIP), Simple Mail Transfer Protocol (SMTP), Simple Network Management Protocol (SNMP), Hyper Text Transfer Protocols (HTTP), Internet Control Message Protocol (ICMP) are some of the few protocols that are associated with the application layer. Each of these can be defined as: FTP: Used for uploading or downloading videos, images, and documents to share with friends from a virtual terminal. SMTP: Used for delivering messages from the Internet. It is usually associated with electronic mails that may also use Post office Protocol (POP3) for downloading emails stored on the server. DNS: “A dedicated server or a service within a server that provides DNS name resolution in an IP network. It turns names for Web sites and network resources into numeric IP addresses. DNS servers are used in large companies, in all ISPs and within the DNS system in the Internet, a vital service that keeps the Internet working.” (DNS server. 2011) RIP: The routing information protocol exchanges information from routers to update their routing table. SNMP: Simple Network Management Protocol is configured with network management application that identifies and alerts for any event associated with downtime, malfunction, status, health etc. HTTP: Hyper Text Transfer Protocol is used for sending user request from the web client to the web server via an Internet browser. Home user request for a web page from the X stream server by entering the Uniform Resource Location in the web browser. The request is routed to the corresponding network devices and continues to move forward till the destination i.e. X stream is reached. Conclusion In short, we have discussed all the workings on each layer of the TCP/IP model and associated with the OSI layer where relevant. The home user will initiate a request from an application layer i.e. the web browser with an IP address associated with it. Likewise, the network layer receives this information and moves the transmission after processing to the transport layer. The transport layer forwards the connection request to the network access layer that establishes connectivity to the network of the X stream. Bibliography James F. Curose & Keith W. Ross (2000). Computer Networking A Top Down Approach. 4th ed. London: Addison - Wesley. 62. Dslam. 2011. Computer Desktop Encyclopedia, , pp. 1. MORROW, M.J. and VIJAYANANDA, K., n.d, Developing IP-Based Services: Solutions for Service Providers and Vendors (The Morgan Kaufmann Series in Networking) Morgan Kaufmann. CLARKE, n.d, G.E., CompTIA Network+ Certification Study Guide, 5th Edition (Exam N10-005) (Certification Press) McGraw-Hill Osborne Media. DNS server. 2011. Computer Desktop Encyclopedia, , pp. 1. Read More