Networking Technologies Journal of Computer Science Issues

Question: Describe about the Networking Technologies for Journal of Computer Science Issues. Answer: Advantages and disadvantages of bus, mesh and star physical topologies Topologies Advantages Disadvantages BUS Example: 10base-5 (ThickNet) and 10Base-2 (ThinNet) It is easier to connect a peripheral or a computer to a linear bus. It is well-suited for small networks. It is cheaper to implement (Heidarifar Ghasemi, 2016, p. 250). It cannot be used as a single standalone solution. If there is a break in the main cable, then entire network will shut down. Isolating faults within the network nodes is difficult. MESH Example: WAN and Internet This network consists of many alternate paths for data transmission and therefore the entire network does not shut down due to a failure of a single node. It is easy to identify faults due to point-to-point of contact between each pair of nodes. It is possible to send and receive data from one node to several other nodes at the same time owing to the design of the network (Pandya, 2013). The maintenance and costs incurred are high since a lot of cabling are required. A mesh network is complex and therefore, its administration is difficult. In this network, the node of one network is connected to all other nodes in the network, many of them have no significant use which contributes to network connection redundancy. STAR Example: LocalTalk or Ethernet The topology possesses lesser security risk as the analysis of traffic is easy. Detection of faults in the network devices is easy because of the centralized nature of the network. Traffic load is handled better with good speeds because of the high-capacity central hub. The data does not pass through many nodes in this network (Goyal, Ram, Dua, 2016, p. 11). Extra hardware is required, and therefore cost of setup runs high. The capacity of the central hub dictates the number of nodes that can be added. The entire of operation of the network depends on the central hub; hence, failure entire network fails if the central hub experiences failure. Explanation of OSI model is better than the TCP/IP model. Reason it hasn't taken over from the TCP/IP model OSI model is better than TCP/IP model because: The standard of OSI is protocol independent and generic, while the TCP/IP model is created on standard protocols. Compared to TCP/IP, OSI provides a wide variety of choice. Its universal platform means OSI works on any operating system. iii. Product functionality is interpreted at every stage of the OSI layer. For security purpose, OSI encrypts the data. Compression and expansion of messages are made less complicated so that messages travel efficiently from one device to another. The addition of multiple network models is easy (Edwards Bramante, 2015). The Internet was originally planned to be built on the OSI model, but it failed due to politics, bad implementation, technology and bad timing. When TCP/IP model was completed at that time, a lot of money and time had been already invested in OSI model. The presentation and session layers were empty while the data link layer was clogged. TCP/IP was more reliable than OSI and supported Unix, which was used in academia. Eventually, OSI model became a poor model; it was discarded, and TCP/IP was adopted (Bora, Bora, Singh, Arsalan, 2014). Fig 1: TCP/IP and OSI model (Source: Heidarifar Ghasemi, 2016, p. 250) Calculation of approximate bit rate and signal level(s) for a 3.5 MHz bandwidth system with a signal to noise ratio of 133 Capacity of Channel: Comparison of IPv4 and IPv6 private addressing. Reason behind same private addresses in different locations causes conflict on the Internet Ali (2012) opined that, all the addresses of IPv4 (Internet Version Protocol 4) are public except three address ranges which are private (p. 315). The private addresses are designed by IETF RFC. Private addresses cannot be used on the Internet and are mainly used organizations. It has a 32-bit address and a total of 232 addresses. Address Resolution Protocol (ARP) is used for mapping IPv4 address to MAC addresses. IPv6 (Internet Version Protocol 6) addresses are temporary and public and are designated by RFC 3041. IPv6 addresses can be globally routed through the Internet and are meant to shield the client's identity during communication. The IPv6 addresses are temporary and therefore, it does not possess a valid MAC address. Both IPv4 and IPv6 addresses look almost similar. IPv6 is a 128-bit address and allows a total of 3.4 x 1038 addresses. In IPv6, ARP is replaced by Neighbor Discovery Protocol or NDP (Cui, Wu, Wu, Vautrin, Lee, 2013). To enable traffic from hosts using private addresses to access internet hosts utilizing a public address, NAT or Network Address Translation is used. NAT allows the conversion of private addresses to public addresses to connect to the Internet. Public addresses are costly and are limited and are therefore only allocated by the ISP. Same private addresses can be multiple times in different networks. Hence, private addresses do not cause conflict on the Internet (Zimu, Wei, Yujun, 2012). RFC1939, a POP3 session is one of the following states: closed, authorization, transaction or update. Diagram showing these four states and how POP3 moves between them Fig 2: Finite State Machine of Post Office Protocol (POP3) (Source: Gellens, Newman, Yao, Fujiwara, 2013) POP3 is a client/server protocol. A POP3 session starts by contacting POP3 server by a POP3 client by making a TCP connection in the Authorization state. When the authentication is successful, the client does mail access transactions in the Transaction state. When the action is finished, the session is closed down by the client and automatically Update state is entered. In Update state, the POP3 session ends after the cleanup functions are completed (Gellens, Newman, Yao, Fujiwara, 2013). Explanation of Distributed Hash Table (DHT) and its use in P2P networks DHT or Distributed Hash Tables are algorithms used in current P2P applications to provide a fault tolerant, scalable, reliable, and efficient way to handle peer-to-peer networks. They are used in P2P applications to keep and fetch data efficiently (Zhang Li, 2014). He, Dong, Zhao, Wang, Qiang (2016) stated that, to control the P2P network, DHTs maintain a centralized server instead of a decentralized server. The system, therefore, is composed of different parts (p. 61). In P2P network, DHTs accomplish data retrieval and routing in logarithmic time and is fast. DHT makes the system quite robust which it can withstand from large-scale attacks. P2P using DHTs are true P2P applications. Another reason being DHT is employed in P2P network is that P2P applications and networks operate differently from conventional applications, as they centralize critical data which create issues. In DHT P2P, every node in the network is assigned a Globally Unique Identifier or GUID. Example: BitTorrent utilizes DHT or distributed sloppy hash table, to keep trackers torrents peer contact information. Hence, each tracker is a peer. It is implemented over UDP and is based on Kademila. DHT stores the location of peers in its nodes. DHT nodes are present in the BitTorrent clients, which is used to communicate other nodes in the DHT, to get the address of peers to download from utilizing the BitTorrent protocol (Moore, Morrell, Marchany, Tront, 2015, p. 1562) References Ali, A. N. A. (2012). Comparison study between IPV4 IPV6.International Journal of Computer Science Issues,9(3), 314-317. Bora, G., Bora, S., Singh, S., Arsalan, S. M. (2014). OSI reference model: An overview.International Journal of Computer Trends and Technology (IJCTT,7(4). Cui, Y., Wu, J., Wu, P., Vautrin, O., Lee, Y. (2013).Public IPv4-over-IPv6 access network(No. RFC 7040). Edwards, J., Bramante, R. (2015).Networking self-teaching guide: OSI, TCP/IP, LANs, MANs, WANs, implementation, management, and maintenance. John Wiley Sons. Gellens, R., Newman, C., Yao, J., Fujiwara, K. (2013).Post Office Protocol Version 3 (POP3) Support for UTF-8(No. RFC 6856). Goyal, N., Ram, M., Dua, A. K. (2016). 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