Device Transmission on a Network Using Token Bus

Added on - 22 Sep 2019

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Question 1(7 + 8 + 10 = 25 marks)a)In modern switched Ethernet networks, it is not unusual for a router to receive more trafficthan it is able to forward due to the relative speeds of the Ethernet network versus thelinks from the router to other networks or the Internet. In such circumstances, packetswould be randomly dropped either by the router or by the interconnecting switch whenbuffers are filled. Briefly discuss how polling could be used to overcome this problem, anddiscuss two advantages and two disadvantages of this approach.b)Prior to the development of full-duplex Ethernet, Token Bus networks provided a meansthrough which communication could be achieved on a shared medium without collisions.Briefly describe how devices transmitted on a network using Token Bus (ignore tokenmanagement) and discuss the performance token bus as transmission speed increases.c)Collisions and broadcasts have a negative impact on the throughput of an Ethernetnetwork.i)Describe how collisions and broadcasts influence the throughput on an Ethernetnetwork using a bus topology.ii)Repeaters, hubs, bridges, and switches are all devices that can be used in theconstruction of Ethernet networks. Briefly discuss how each of these deviceswould influence the impact of collisions and broadcasts within a single Ethernetnetwork.Hint: VLANs divide a network into two or more networks and is irrelevantto this question.Question 2(6 + 6 + 8 + 20 = 40 marks)a)IPv4 uses a checksum to determine if any errors have occurred in the transmission of adatagram, however this checksum only checks for errors in the IPv4 header. Discuss whyonly the header is checked by IPv4 for errors, and discuss whether it is necessary to checkfor errors at all given that Ethernet already checks the entire frame using CRC.b)Given a subnet mask of 255.255.192.0, demonstrate for an IP address of your choosing thecalculation of the range of addresses that are valid from that network (host ID all 0sthrough to host ID of all 1s).Note: The IP address you choose must consist of four decimal numbers that are greaterthan or equal to 101, and must be odd numbers.c)The fragmentation mechanism provided by IPv4 can contribute to network congestion.Briefly describe how fragmentation works and, given that there is no change to higherleveldata, explain how this mechanism could contribute to congestion.d)Consider implementing a negative acknowledgement mechanism for IPv4 that would alerta source host to a datagram being discarded due to a corruption in the path between thecommunicating hosts at any router in the path or the destination host.i.Briefly describe how your protocol would work. ii.Illustrate the operation ofyour protocol using a time diagram/sequence diagram (see Session 5 Slide 39 for anexample), including both successful and unsuccessful delivery of datagrams.iii.Discuss two advantages and two disadvantages of your protocol.Question 3(11 + 8 + 16 = 35 marks)
a)Both RIPv2 and OSPFv2 routing protocols receive updated information about the state ofthe network from their neighbours. However it can be said that the decisions made byvector-distance routing protocols (such as RIPV2) are based on “second hand” information,whilst the decisions made by link state routing protocols (OSPFv2) is based on “first hand”information. Briefly describe what information is contained in the updated informationrouters receive, where the information comes from, and why it is considered “secondhand” or “first hand”.b)Given the following Link State Database and network topology:ABCDEFA--1-41B---316C1---2-D-3---2E412---F16-2--Demonstrate the working of the Shortest Path First algorithm and final routing table forone of the routers of your choosing. Your answer must indicate the paths and costs thatwill be taken by all datagrams through the network.c)For each of the fields listed below appearing in the IPv4 and IPv6 headers, briefly describethe purpose of those fields, explain how they are related, and explain why a change hasbeen made:i.IPv4 defines both header length (HLEN) and total length fields, whilstIPv6 defines only a payload length.ii.IPv4 defines a protocol field, whilst IPv6 defines a next header field. iii.IPv4 defines a time to live (TTL) field, whilst IPv6 defines a hoplimit field.Marking SchemeACEFBD
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