Computer Communications & Networks - Lab Report Example

Computer Communications & Networks X Stream Server [Type the 12 Table OF Contents Introduction ………………………………………... Page 2 X-Stream Server ………………………………………… Page 2-7 Conclusion …………………………………………… Page 7 References ……………………………………………. Page 8 Introduction Internet has turned out to be a revolution and the greatest discovery for humans. Now every piece of information is on the Internet. Apart from communicating with each other, state of the art web based applications are now available on our home computer desktop. Popular Internet services includes video conferencing, VoIP based application, interactive help lines, social networking sites, online discussion forums, webinars, podcasts, etc. Organization are expanding by doing business online, saving costs by incorporating cloud computing, educational institutes are providing there students the advantage of computer based training and learning and list goes on. In this report we will discuss the semantics that are behind the scenes when we enter a URL for opening the X stream education portal. There are many networked devices, components, technologies, and methods involved to open a single web page from the Internet. All these devices talk with each other by different protocols. TCP/IP is one of the fundamental protocols that are mandatory for establishing connection on the Internet. However, the combination of these protocols serves to sustain an Internet connection and request the source to provide a new packet, in case of a missing or corrupted packet. We will discuss in detail and try to cover different aspects of accessing the remote X stream server from home. X-Stream Server The first point of focus will be the hardware and software that will contribute to establish connectivity. The hardware may involve an Ethernet adapter, DSL router and system software. However, we will take a holistic approach that will cover all factors that may initiate and construct the data packet and transmit it to the destination to establish connectivity. As there is a requirement of accessing X stream server from the home, mandatory requirements are an Internet connection and a web browser. In order to test connectivity of the Internet connection, ping command is executed from the command prompt of the operating system. The syntax will be ping (space) (destination address), moreover, in order to review hops and delays in accessing the X stream server, the ‘tracert’ command can be executed from the command prompt. The syntax for this command will be tracert (space) (destination address). The ping command utilized Internet Control Message Protocol (ICMP) to check the connectivity of the destination by sending ICMP echo request on periodic basis. Moreover, the ‘tracert’ command demonstrates all the hops and delays that are in the way of that particular destination. Likewise, it is not necessary that only routers are involved in the process of establishing and exchanging information from the required host. The Ethernet is the first device that initiates and constructs a request datagram from the home computer, as it is considered to be the most popular Local Area Network technology that is implemented globally (Ethernet. 2007). The connectivity of the Ethernet adapter is established by both wired and wireless networks. However, in terms of wired connectivity, twisted pairs of cable are connected in to the Ethernet RJ45 socket. The other end of the wire is terminated to the router, switch or hub. In this scenario, home user will use a DSL router that will connect the home computer with the Internet Service Provider (ISP). Likewise, the Ethernet construct the datagram consisting of six parameters i.e. destination address, source address, preamble, type, CRC and data. The preamble parameter is responsible for clock synchronization of the data packets from the source and destination. Likewise, the addresses comprises of six bytes, which is accountable for frames from the source and destination exchanging within the network layer protocols. In case of a mismatch, the frame is denied or discarded. Moreover, the type illustrates the protocol type. Usually the type parameter defines the IP addresses that considered to be a high layer protocol, however, it also includes various other protocols such as Apple talk, NetWare, etc. The CRC parameter is responsible for error checking and correction, as it monitors the data transmission and discards any erroneous packets if detected. After receiving all values of these parameters the datagram listens for any ongoing traffic on the network segment. This is the point where ‘Carrier Sense Multiple Access with Collision Detection’ plays its role. Usually, a lot of other requests are seeking for attention, and if collide with each other or make a queue, creates a deadlock or network congestion. In order to prevent this situation CSMA/CD becomes in charge of the situation. As per desktop encyclopedia CSMA/ CD triggers when any network component or device request for establishing connection or seeking for an access to the network. It creates a signal for every request for listening to empty spaces on the network segment. If other request is operating on the same segment, it holds the new request in queue and let the current request to be fulfilled. As soon as the current request completes, the green signal opens for the new request. However, CSMA/CD randomly retries to send the new request in order to gain a space for execution. Likewise, there are cases where, two or more request wants to access a similar network resource, CSMA/CD identifies this issue and delays the entire request to wait for a green light. After constructing a successful packet and getting a green light from CSMA/CD, the request now heads towards the switch. However, it is not necessary that a home user must have a switch. Switches are intelligent devices that maintained a database within its circuit. The database is called as the Management Information base (MIB) (Aagesen, Chutiporn Anutariya et al., 2004). The MIB stores three parameters i.e.MAC address, Interface name and Time To Live (TTL). For example, home computer wants to send a request to the router for accessing the X stream web portal. The switch quickly learns the MAC address of the home computer and the DSL router as well. This will facilitate the transmission to be resilient because the required MAC addresses are fetched by the MIB of the switch. However the identification of MAC addresses is handled by Address Resolution Protocol (ARP). Likewise, ARP broadcasts a query for matching the required MAC from a specific node on the network. However, the node can be a device, as well as a computer. As every device has a unique MAC address, all the nodes receives a query for a required MAC address, upon confirmation of a match, the connectivity is established. After analyzing the MAC query packet comprises of 48 bits in size, we can identify two values i.e. Organizational Unique Identifier (OUI) and Vendor Assigned Value. The OUI is the representation of the manufacturer provided information stored in hexadecimal value and the Vendor assigned value is also a hexadecimal value that incorporates vendor specific information. For defining the IP address, we will discuss a 32 bit octet IPv4 address. For example, 192.168.1.1 is a 32 but IP v4 address. For connecting the X stream server from a remote location, home user will initiate a connection request that will travel from the home to the X stream via an IP address. In the process, routers will play a vital role, as they are considered as intelligent devices that are responsible for routing request to different networks comprises of different subnets. After receiving the request from the home user computer, it analyzes the datagram packet to extract a valid IP address and subnet. The construction of the datagram includes values that will be embedded in the packet header from the home user i.e. Source MAC address, Destination MAC address, Source IP address and Destination IP address. As the home user only knows the URL of the X stream server and the URL is not resolved by the DNS, we do not know the IP address of the X stream server. However, the source MAC address is the router that will route the datagram to the relevant destination. After receiving the datagram frame, the router learns the IP address of the home user. On the other side, the network of the home user learns the correct router by learning the MAC address of the router on Interface ‘X’. Likewise, the router routes the request on a different network interface ‘Y’ of different subnet. At this point the router learns MAC addresses of the source and the destination. The request is routed to the X stream server on a different network and subnet on a remote location. Explaining the connectivity of the home user to the X stream server by discussing TCP/IP model will be more interesting. The IP stack includes Physical layer, Data link layer, network layer, Transport layer and Application layer (Ross 2009). The home user only has a Uniform Resource Location (URL) i.e. ‘https://x-stream.leedsmet.ac.uk/’. Likewise, this information must be typed in the browser to gain access. As mentioned in the previous discussion that the request is constructed by the Ethernet adapter following the home DSL router. Consequently, the DSL router will route the request to the concerned router in order to gain access. If we assume that the home based DSL router has the following IP address 175.110.106.189 with a subnet of 175.110.0.0 /20 (Home Network). After receiving a request from the computer, the DSL router replays the request to the corresponding ISP router with a subnet of 169.100.0.0/32 (ISP Network). However, there is a requirement of mentioning a DNS server. Home Internet users do not have DNS configured. ISP is responsible to resolve the URL into IP addresses. In order to do so, the request from the home network will terminate on the ISP Network that will resolve the URL and sends the request to the relevant destination accordingly (DNS server. 2011). After resolving the DNS for the URL, the router checks for the shortest and robust path for processing the quest with the help of routing protocol. Some popular routing protocols include Routing Information Protocol (RIP), Open Shortest Path First (OSPF), Border Gateway Protocol (BGP) etc. After identifying the most suitable path for the request, the connection to the X stream server will be established. Encapsulation of User datagram protocol (UDP), IP and Ethernet takes place before sending it to the router for resolving DNS query. As the MAC address is already extracted by the ARP command, the identified router receives the encapsulated DNS query. Furthermore, for querying the sockets of HTTP and TCP to open a connection in a web server, a three way handshake takes place. The first phase is the handshake that operates on TCP SYN segment. The second phase includes a response from a web server via TCP SYNACK in order to establish connectivity. After establishing connection, TCP sockets are ready to accept HTTP traffic along with the IP datagram relayed to the ‘https://x-stream.leedsmet.ac.uk/’ (Seth, Venkatesulu, 2008). Lastly, the X stream server responds back by opening the requested educational portal and services. Conclusion In our journey for demonstrating the connectivity of a home user with a remote X stream server was interesting. The first section covered mandatory requirements as well issues that occur on physical layer connectivity. Likewise, we have discussed the Ethernet packet header along with its purpose in details. The next discussion was about CSMA/CD, as the request needs space to fulfill the execution. Next we have discussed the ARP command along with the discussion of a MAC address packet. Moreover, in the next section we have discussed the network layer connectivity and router functionality. We have also put some light on routing protocols and their functions. Furthermore, in the last section, DNS query construction is discusses along with socket connections by incorporating HTTP, TCP/IP, UDP and ARP for opening the X stream web page on the home user browser. References AAGESEN, F.A., CHUTIPORN ANUTARIYA and WUWONGSE, V. 2004, Intelligence in Communication Systems : IFIP International Conference, INTELLCOMM 2004, Bangkok, Thailand, November 23-26, 2004, Proceedings (Lecture Notes in Computer Science) Springer. 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. 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. Read More