CSCI 278 : COMPUTER NETWORKS Instructor : Seung Bae Im MIDTERM EXAM ----- Spring 1997 Closed book, closed notes. Print your name on each page of the answer sheets. Do not write on the back of a page(they will not be graded). State all assumptions. Majority of the questions require Brief answers! Use time efficiently. 1.(5 points) (a) List standardization organizations(as many you know which are related to networking--distinguish between national/regional/international) (b) What is the main dilemma of the standardization? 2.(30 points) Define/describe the following terms: (a) Nth Layer Protocol (b) OSI 7 layer model (c) Data Encapsulation /decapsulation (d) Contrast FDM & TDM (e) Main difference between 100BaseT and 100BaseVGAnyLan (f) 8BZS(8 Binary Zero Substitution) 3.(10 points) (a) Digital communication systems achieve Òhiger S/N(Signal to Noise ratio) than analog systems. Explain how? (b) List the advantages of fiber optics compared to electromagnetic medium (twisted pair, Coaxial cables, ...) 4.(10 points) (a) Difference between BPS and Baud. (b) What is ShannonÕs Capacity? Why canÕt we achieve ShannonÕs capacity in practical systems? ( C = H log2( 1 + S/N ) ) 5.(15 Points) Answer the questions. (a) Why do we twist wires(UTP/STP)? (b) The European version of T1 carrier is called E1. E1 uses 8 bits per sample, 4Khz bandwidth for each voice signal. It multiplexes 30 voice channels and use 2 extra channels for signaling and synchronization. (1) Calculate the total rate(bps) of E1. (2) Now, we like to carry an E1 on a transmission line. If you are given a line with 10MHz bandwidth, calculate the S/N in decibel. Exact value is not needed. (c) For ISDN: Describe 2B+D, Does ISDN use in-band or out-of-band signaling? 6.(15 points) (a) Why Ethernets are said to have ÒNon-deterministic delayÓ? (b) The current trend in networking is going from Òshared mediaÓ to Òswitched mediaÓ. Discuss the difference. (c) Describe the function of ÒEthernet 10BaseT HubÓ. What are the advantages of the 10BaseT compared to 10Base5 or 10Base2? Any disadvantage? 7.(15 points) Discuss/describe (a) What are the file systems that are supported in Windows NT Workstation? (b) What do you have to check before you buy a device for Windows NT computer? (c) NOS(Network Operating System) (d) Where does NT stores information about system configuration, user desktop environment, ...? (e) What kinds of transport protocols does NT support?