Computer Communications & Networks - Report Example

? Computer Communications & Networks Table OF Contents Introduction ………………………………………... Page 3 X-Stream Server ………………………………………… Page 4 Routing ………………………………………… Page 7 Conclusion …………………………………………… Page 8 References ……………………………………………. Page 10 Introduction Today, the Internet provides numerous opportunities for humans to communicate and exchange information. Apart from various advancements such as web2.0, the semantic web and virtual and augmented reality, fundamental concepts and protocols that are used to transfer and deliver a data packet is the same. However, in order to examine the processes, methods and techniques, we must first understand the TCP/IP protocol suite itself. Considering Internet Protocol (IP) first is vital because the rest of the TCP/IP suite is constructed on the IP. Likewise, it is also called as a mechanism that is incorporated for data packaging, transferring and routing via TCP/IP internetwork (Kozierok 2005). Moreover, IP is also involved in constructing and packing all data grams in a similar fashion while managing them between devices in an intelligent way. Before getting into more detail, the prime objective for having a network, internetwork and TCP/IP suits is to empower and enable networking application. For online accessibility, these applications are now operational via web browsers. For instance, anyone wants to upload pictures, multimedia contents to share with family, similarly, chatting with friends and colleagues from Internet Relay Chat (IRC) applications. In general, a common interface is now reachable for making communication purposeful. Accordingly, student portals are now developed and considered as an efficient educational interactive interface for universities and colleges. Likewise, apart from some examples given previously, student portals are advanced application bundled with many features and applications supports education and learning activities. In the next section, we will explore networking concepts for a student portal named as ‘X-stream server’ accessed by a student from a remote location. The X-Stream Server The first section i.e. the internal semantics will focus on connectivity of a computer internally as critical components of the computer network must be examines by a holistic approach as every component contributes to the heterogeneous system (Olifer, 2005). If anyone wants to access the X-stream server from the home computer, it must be connected to the Internet. The simplest of troubleshooting steps incorporates the ‘ping’ command. The syntax of the command will be ‘ping (space) (destination address)’, executes via command prompt. Likewise, ‘tracert’ command can also be used to give an illustration of delays from source to the router along with end to end connectivity to and from the destination (Ross 2009). However, many devices and protocols are integrated for maintaining and identifying the computer and sustaining connectivity. The first point of interest in addressing internal semantics is Ethernet. It is considered to be the most popular Local Area Network technology that is implemented globally (Ethernet. 2007). The Ethernet connects with a shared transmission medium called as twisted pair or a cable with a multi-port hub, switch or a bridge. Most commonly, an Ethernet switch or a DSL router + Switch is most common. A typical Ethernet frame comprises of six parameters i.e. Preamble, destination address, Source address, type, data and CRC (cyclic redundancy checking). The preamble is responsible for synchronizing clock rates for the recipient and the sender. Address is usually six bytes in size and is responsible for identifying frames as per the sender and receiver address, it transmits the data in network layer protocol. However, if the match is not made, it discards the frame. Likewise, the type indicates the protocol type. Normally it deals with IP address, which is a higher layer protocol but sometimes incorporates other protocols such as Novell or Apple talk etc. Lastly, CRC is responsible for error checking and control and drops or discard packets if they are corrupted or erroneous. Moreover, in order to prevent collision within the network ‘Carrier Sense Multiple Access with Collision Detection’ is recommended. It is a possibility that more than one connection are trying to access X-stream server at the same time, which may result in delays and possible termination of the request. As per computer desktop encyclopedia CSMA/ CD triggers when any device wants to access the network, as it listens and checks the traffic on the network. After getting the green light i.e. No traffic on the current network segment, this means that the no other communication is taking place and therefore, the transmission is allowed to carry out. However, if there is a red light i.e. there is traffic; it waits with a random amount of time prior retying to check space. Of course, there can be a situation, where two or more requests for accessing a similar resource on a network initiates, CSMA/CD detects this collision and terminate the entire similar request for a random check of space, as mentioned earlier. A switch is considered as a learning device and maintains a management information base within its database to save the MAC address of a particular computer. Likewise, the learning capability of a switch prevents from network congestion and excessive unwanted traffic on the network. However, the initial step for a computer to interact with any computer is to query the MAC address by a protocol called as Address Resolution Protocol (ARP). ARP broadcast a message to establish connectivity and for identifying the required MAC address to the internal network containing two or more hosts, each having a unique MAC address. Application layer The required MAC is identified by a match confirmed from the recipient computer via ARP command. The structure of an Ethernet MAC address contains an Organizational Unique Identifier (OUI) and Vendor Assigned value both comprises of 48 bits in length. Likewise, the OUI contains the manufacturer information that represents a hexadecimal value and Vendor Assign value also has the same characteristics except a specific value for a device. After discussing the internal communication, we will move forward and discuss IP addresses. The IP version 4 is comprised of 32 bit network address, as there are total 4 octets that represent an IP version 4 addresses. For instance, 192.101.2.1 is a 4 octet 32 bit IP address. In order to connect to the X-stream server that is at a remote location, the user must send a connection request that will be delivered via IP address. Routers are intelligent devices that routes traffic that is received from different IP addresses from different networks. Moreover, they recognize different networks via different subnets and relay traffic on other networks as requested. If a router received a request from a home computer for accessing the X-stream server, the request will be fulfilled accordingly if a valid IP address and subnet is embedded in the packet header. Let’s assume how a datagram is delivered to the webserver of the X stream from home, only three devices are associated with this transmission i.e. Home computer, Router and X stream server. The first step includes a construction of a datagram that will fill essential parameters in the packet header such as Source MAC address, Destination MAC address, Source IP address and Destination IP address. However, destination IP address is not known at this point and the source MAC address will be the router that will relay the datagram to the relevant network. The router receives the datagram frame and learns the IP address of the sender i.e. the home user. However, the sender identifies this router by learning the MAC address of the router on Interface 1. The router then sends the IP based request on a different subnet via interface 2, however, at this point, interface 2 learns both MAC address i.e. the source MAC address and destination MAC address. Finally, the request is delivered to the X stream server that is on a different subnet and at a remote location. This scenario only explains connectivity encompassing only router, however, more than one router can be involved. Transport layer In order to get into detailed semantics, first we have to understand the factor that addresses the TCP/IP model. Likewise the IP stack comprises of Physical layer, Data link layer, network layer, Transport layer and Application layer (Ross 2009). In a real world scenario, the first step in accessing the X stream server will be to enter a Uniform Resource Locator. Likewise, the home user will type a URL address in the address bar of the web browser. The request will be initiated from the Ethernet card following with the DSL router of the home user. The DSL router will redirect the request to the first hop router. Let’s assume the router of the home network has the following IP address with subnet 169.150.4.125 and the request of the home initiates from R1 (Home Network) 169.150.4.0/32. The router R1 identifies the destination address and routes the request to another router that is located in the premises of the Internet Service Provider (ISP). It depends because ISP’s also tends to outsource DNS servers. The internet/Network layer The first hop of this request will be the ISP router R2 (ISP Network) 169.150.0.0/24. The functionality of a DNS server in this scenario will be to translate the URL of the X stream server i.e. www.xyz.com into IP address. As the core function of dedicated DNS servers is to translate names of websites and network resources into numeric addresses so that network devices can process and route the data accordingly (DNS server. 2011). After translating the URL from the DNS, a numeric value is directed to the router of the University i.e. R3 64.228.155.0/20. The router identifies the request and redirects the request to the webserver located in the university with IP address 64.228.155.32 and the requested connection is established. Routing As mentioned DNS before, the DNS query is encapsulated with UDP, IP and Ethernet are prior sending the request to the router, however, prior sending the request to the router, the MAC address is required that is fetched by ARP. This protocol broadcasts the request for matching the MAC address, already discussed before. After the correct match is found, now the home user’s Ethernet has learned for its first hop i.e. Router. After identifying the router i.e.169.150.0.0/24, encapsulated DNS request is sent. Likewise, the DNS request travels through the home user’s switch or DSL router + switch to the router. The datagram from the home user interface is routed to the ISP’s network via routing protocols. These protocols deliver the request from the home user to the router where routing tables are created and IP address of the X stream server website i.e. www.xyz.com from the DNS is fetched. However, in order to query HTTP, TCP sockets are opened from the web server by the user via TCP SYN segment which is a 3 way handshake and this is the first step. Secondly, web server gives a response in terms of TCP SYNACK and the connection establishes. Similarly, TCP sockets accept HTTP request containing the IP datagram that is router to www.xyz.com (Seth, Venkatesulu, 2008). Therefore, the X stream server answers the HTTP request by opening the requested web page or service. Conclusion In this scenario, we have learned the in depth connectivity mechanisms of an IP based network for accessing the X stream server from home. It was a great learning experience from end to end connectivity and retrieving requested data and services from a remote site. It is clear that information and data available in the application layer is quite different and considered to be an operating system integrated with a general graphical user interface (Thompson, n.d ), as compared to the information travelling in other layers of the OSI and TCP/IP Model. Network devices understand in the medium of numeric and hexadecimal values such as the subnet and MAC address. Moreover, the switches also play a vital role of robust communication and fail/safe methods such as CSMA/CD. Furthermore, I would like to mention one of the core components i.e. DNS. It seems that if there is some issue with retrieving the numeric address of any website, there will be no accessibility of the website in spite of running all the functions correctly. Lastly, every process is important and has its importance in terms of data communication and network along with different routing protocols that also maintains routing tables for robust and secure connectivity. References Csma/cd. 2011. Computer Desktop Encyclopedia,, pp. 1. DNS server. 2011. Computer Desktop Encyclopedia,, pp. 1. Ethernet. 2007. Network Dictionary , pp. 180-181. Kozierok, C., 2005. The TCP/IP guide: a comprehensive, illustrated Internet protocols reference San Francisco: No Starch Press. Olifer, N. and Olifer, V., 2005. Computer networks: principles, technologies, and protocols for network design Hoboken, N.J.: John Wiley & Sons. Ross, K.W., 2009. Computer networking: a top-down approach Pearson/Addison Wesley. Seth, S. and Venkatesulu, M.A., TCP/IP architecture, design and implementation in Linux Hoboken, New Jersey: Wiley; c2008. Thompson, L.S., Industrial Data Communications (Resources for Measurement and Control Series) ISA: The Instrumentation, Systems, and Automation Society. Read More