Computer Networks - 2002 2003 Exam - Electrical Engineering, Exams of Electrical Engineering

Download Computer Networks - 2002 2003 Exam - Electrical Engineering and more Exams Electrical Engineering in PDF only on Docsity! S217 24/06/03 THE MANCHESTER METROPOLITAN UNIVERSITY FACULTY OF SCIENCE AND ENGINEERING DEPARTMENT OF ENGINERING AND TECHNOLOGY SESSION 2002/2003 Examination for the BSc (HONS) INFORMATION TECHNOLOGY BSc (HONS) MEDIA TECHNOLOGY BSc (HONS) COMPUTING AND NETWORK TECHNOLOGIES FINAL YEAR BSc COMBINED HONOURS STAGE THREE UNIT 64EE3038 : COMPUTER NETWORKS Tuesday 13 May 2003 9.30 am to 12.30 pm Instructions to Candidates Answer FIVE questions. Figure Q6 is provided as a separate sheet and if used should be handed in with your answer book. 24/06/2003 continued 1 1. (a) Discuss how in the 1960’s a perceived threat to the USA led to the development of the TCP/IP Reference Model and the Internet. [6] (b) Outline how standards for the TCP/IP Reference Model and the Internet are established. [6] (c) State the type of transport layer service that is most suitable for an application in which messages flow according to a client-server model and fast response is required. [4] (d) Discuss the main weaknesses of the TCP/IP Reference Model. [4] 24/06/2003 continued 4 5. (a) The ISO File Transfer Access and Management (FTAM) protocol uses a file representation known as virtual filestore (VFS). Explain why the VFS file representation is used. [4] (b) Describe the VFS file access structure with reference to the terms FADU and DU, explaining clearly the difference between FADU’s and DU’s. [6] (c) Using the appropriate diagram, show the complete access structure of the FTAM virtual file store represented by the access context context_1: Where: context_1:= (R,duR,/,A,/,B,duB,\,/,C,duC,\,\,/,D,duD,\,/,E,duE,/,F,\,\) [5] (d) Using an appropriate diagram, show the four regimes defined in the ISO FTAM protocol and outline the events which occur during an FTAM operation. [5] 24/06/2003 continued 5 6. (a) Describe the advantages of an ATM network when compared with conventional packet switching and hence explain why packet switching is not suitable for use with multimedia networks. [5] (b) An important design decision when designing a cell relay network such as ATM is the length of the cell data field. Consider this decision from the viewpoint of transmission efficiency and packetisation delay. Derive an expression for the transmission efficiency N as a function of the header field of H octets and the data field of length L octets. It may be assumed that all cells are completely filled during transmission. Find the optimal value of efficiency and comment on this value for ATM cells. [5] (c) Data rates used for voice encoding are 32kbits/s and 64kbits/s. Plot the packetisation delay and transmission efficiency as a function of cell data field size using Figure Q6, which is also available as a separate sheet and should be included with your answer. [5] (d) Comment on the graph and discuss its significance for the choice of cell length used in ATM networks. [5] Packetisation Delay and Transmission Efficiency vs Cell Length Figure Q6 Packetisation Delay and Transmission Efficiency vs. Cell Data Field 0 5 10 15 20 25 30 35 8 16 32 64 128 Cell Data Field L [octets] P ac ke tis at io n D el ay [ m s] 1.1 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 6 S217 24/06/03 7. (a) The Integrated Services Digital Network (ISDN) supports two distinct types of service. Describe the two services and their relationship to the ISO seven layer model. [4] (b) Describe the two subscriber access paths to the ISDN. [4] (c) Explain what is meant by the term ‘common channel signalling’ and discuss its importance in the ISDN. [6] (d) Discuss the operation of the circuit switched, frame relay and packet switched cell types with regard to the U and C planes of the ISDN. [6] 8. (a) Describe the configuration of an FDDI network, including the types of station used. [5] (b) Explain with the aid of an example how medium access control is achieved within an FDDI network. [5] (c) FDDI-II networks are able to operate in hybrid mode in order to provide isochronous services. Describe how the network achieves cycle synchronization when being initialized into the hybrid mode. [5] (d) The campus of a university has eleven principal buildings each of which requires access to a high speed backbone computer network and telephone services. The use of an FDDI-II network is envisaged which is to be programmed such that no less than 30Mbit/s of packet switched data is available at any time. Find the maximum number of telephone conversations which may occur simultaneously using the network.. [5] END