Data communication and Computer networking - Myassignmenthelp.Com

Questions: 1. A person sends a file from their PC. Explain the TCP/IP encapsulation process the PC undertakes to send this file. Make sure to clearly discuss what happens at each layer of the TCP/IP model. 2. Calculate the approximate bit rate and signal level(s) for a 20 MHz bandwidth system with a signal to noise ratio of 1040. 3.Compare IPv6 Link-Local, Unique Local Unicast and Global Unicast addressing. Discussion MUST also include a comparison with IPv4 private and public addresses? 4. There are 2 ways that the Domain Name System (DNS) can resolve a domain name. Describe how each function in the Internet. 5. Describe persistent and non-persistent HTTP connections. Which one is generally more efficient and why? 6. What is trackless BitTorrent? Briefly explain the protocol it employs to download a file. Answers: Answer 1: When the person initiates the transfer of file a series of steps takes place like, Figure 1:Transfer of file Figure 2:TCP/IP Protocol Architecture Layer 1: Application Layer: Here a communication arises The basic work of the application layer is that the protocols of this layer format the file in a way that it can be easily used by the transport layer protocols. The File Transfer Protocol (FTP) is used for this file transfer. Layer 2: Transport Layer: Here data encapsulation begins When the file enters the transport layer, the protocols i.e. TCP and UDP initiate the data encapsulation process. These protocols build a virtual flow of data between the sending and the receiving application and gives port number to the file. Layer 3: Network Interface Layer: The file is prepared for delivery The file from transport layer protocols is now sending to the internet layer which consists of the IP protocol. IP protocol formats the file into units known as IP datagrams and then their IP address is determined to make the delivery easy. Layer 4: Data-Link Layer: The file is framed here The protocols of Data-link layer arranges the IP datagram into frame along with the attachment of a header and a footer into that frame and checks the errors of the file. Layer 5: Physical Network Layer: Here the frames are sent and received This layer receives the frames from the data link layer and changes the IP addresses into the hardware addresses according to the network media and then send them(Forouzan, 2007). Receivers end: When the file reaches the receivers end, the file navigates through the TCP/IP protocol model in the reverse order. Answer 2: This can be solved by Shannons theorem which is used to calculate the capacity of the system in presence of noise. C = B log2 (1 + SNR) Here, C= capacity B= bandwidth SNR= signal to noise ratio C= 20 log2 (1+1040) C=20 log21041 C= 20*10.023 C=200.46mbps Hence, the highest bit rate of this system is 200.46 mbps. Nyquist Theorem calculates the number of signals levels. C=2Blog2M Here, C= capacity calculated B= bandwidth M= no of signal levels Therefore, 200.46=2*20log2M Log2M=5.0115 M=32.25(approx.) Hence, 32 signal levels will be required. Answer 3: Link Local addresses Link Local IPv6 addresses are used by the nodes on the same link to communicate with neighbouring nodes. But the normal address of the prefix is fe80: /10. 64 bits 10 bits 54 bits 1111111010 0 interface ID Figure 3: Format of link local address These addresses are not routable and are assigned automatically. Mostly they are used on a subset. Unique Local Unicast addresses These addresses are similar to IPv4 private addresses and are composed by adding any random 40-bit hexadecimal string into FD00: /8 prefix. They are only accessible inside an organisation and not outside it. Figure 4: Format of Unique Local Unicast address Global Unicast addresses Any packet which is sent to a global unicast address is only delivered to the interface which identifies that address. They are used to analyse a single interface and are internet routable addresses. n bits m bits 128-n-m bits global routing prefix subnet ID interface ID Figure 5: Format of Global Unicast Address IPv4 have only two types of addressing which are public IP address and private IP address. Public IPv4 address This address is allocated by InterNIC to any device so that it can directly access the internet. They are in a form of blocks of CIDR-based addresses and also exist as a route in the routers of the Internet. Private IPv4 address These addresses are assigned to the organizations to develop their own private network by InterNIC. The private addresses are reserved for class A, class B and class C. The private address cannot be connected to the internet. Answer 4: Domain Name System resolves a fully qualified domain name (FQDN) to an IP address. The two ways by which DNS resolves a domain name are, Recursive resolution The client sends a query to the server and expects that the server will solve it efficiently. The server then searches for resolution in its own database and after that in its local cache. If the resolution is not found in the database and the cache then the server goes through the DNS tree until an answer is received by it. Iterative resolution Here, when the client sends a query to the server it returns the client IP address of the server not the complete answer. After receiving this information the clients makes query to another server and this process goes on till an authoritative answer is not received. The DNS server only tries to find the query in the local cache(Forouzan, 2007). Answer 5: Persistent HTTP connections When the server sends the response message, it leaves the TCP connection open hence, the client and the server are allowed to send requests and responses. These connections are the default mode for HTTP/1.1. Non-persistent HTTP connections In this type of connection, the server closes the connection once it sends a response message to the client. This connection is used only for one request and on response. The default mode of these connections is HTTP/1.0. The persistent HTTP connections are more efficient because in these connections the performance is increased as the CPUs time is saved in router and hosts. The client do not have to wait for one response and can send multiple requests simultaneously along with this the network congestion is also reduced(Irwin, 2016). Answer 6: In trackless Bit Torrent, the list of people who are downloading the same torrent does not hold a particular central tracker, and is inside the network of peer downloaders. As a result, the user should know only one node on the network and not all of them. Distributed Hash Table is the technology which is used in trackless Bit Torrent to download a file. The steps to download a file are, To get the tracker URL inside a file the client looks for that .torrent file. The client will now contact this tracker and with the help of this tracker he will get a list of peers. From that list of peers the file can be downloaded. After downloading the .torrent file, the client figures out the key from this file, This key is now used to get the node from the Distributed Hash Table lookup From this table a peer list is again received and the client downloads the file. References Forouzan, B., Fegan, S. (2007).Data communications and networking. New York: McGraw-Hill Higher Education. Irwin, J., Wu, C. (2016).Introduction to Computer Networks and Cybersecurity. Florida: CRC Press.