$1.$ The maximum payload data rate in the STM$-1$ level of the Synchronous Digital H$-$erarchy $($SDH$)$ is:

$152\mathrm{.}1$

$153\mathrm{.}2$

$150\mathrm{.}336$

$155\mathrm{.}52$

$2.$ How many interconnecting links are required in a $40-$node mesh network?

$680$

$880$

$980$

$780$

$3.$ Which of the features below best relates to a Connectionless Network?

$$ There is no delay variation between packets

$$ It is inherently reliable such as in cases of node failure

$$ A guaranteed quality of service $($QoS$)$ is offered for time sensitive applications

$$ A fixed route is negotiated before packet transmission

$4.$ How many links does a star network require to connect $20$ nodes?

$20$

$10$

$30$

$40$

$5.$ Which comment below best relates to all$-$ optical processing compared to optical$-$electronic$-$optical$($o$-$e$-$o$)$techniques$?$

$$ Optical bypassing is very difficult

$$ It can provide a lower capital expenditure $($CAPEX$)$ solution compared to o$-$e$-$o

$$ It has more electronic components

$$ It can only use one wavelength

$6.$ Approximately how many cross$-$points would a non$-$connecting $1000$ x$1000$ three$-$stage switch require?

$1000$

$1,000\mathrm{.}000$

$2000$

$200,000$

$7.$ Which feature below is NOT generally found in Micro$-$Electronic$-$Mechanical System$($MEMS$)$ switches?

$$ Tilting mirrors arranged in other $2$D or $3$D geometers

$$ Mirrors which more up and down forming a cross$-$bar switch

$$ Strong magnetic fields

$$ Electrostatically actuated gold$-$coded silicon

$8.$ Why were Space$-$Time$-$Space switches preferred in early digital telecommunication networks?

$$ Storage of speech samples was expensive

$$ The switches were always non$-$blocking

$$ Because memory chips were very cheap

$$ Because switching could not be carried out if the desired time slot was busy

$9.$ In packet switching networks, the destination address is$,$

$$ Not required

$$ Assigned after the path is released

$$ Stored in each packed header

$$ Signalled over a separate channel

$10.$ What is the approximate overall blocking probability of a three$-$stage switch with $10$ centre$-$stage switches and $10\%$ link blocking probability?

$6\backslash$times $10-8$

$7\backslash$times $10-8$

$6\backslash$times $10-9$

$7\backslash$times $10-9$

$11.$ How many $64$ kbit$/$s payload data streams can the synchronous digital hierarchy $($SDH$)$ STM$-1$ frame carry?

$2359$

$2379$

$2389$

$2349$

$12.$ If the cost of transmission in a large network with N routers varies as A$/$N and the cost of routing varies as B $\backslash$times N$1$ where A$=1,000,000$ and B$=1000,$ what integer value of N minimises the total cost?

$30$

$34$

$32$

$33$

$13.$ Which of the following phrases best describes one features of opaque optical networks?

$$ They require the same wavelength end$-$to$-$end across the network

$$ Optical by$-$pass is provided by a static optical add$/$drop multiplexer

$$ All the switching and other intelligent network functions are handled by purely electronic systems

$$ They provide dynamics all the optical wavelength level

$14.$ How many mirrors are needed in $200\backslash$times $200$ three$-$dimensional micro$-$electro$-$mechanical$-$systems $($MEMS$)$ optical switch?

$20,000$

$400$

$40,000$

$200$

$15.$ On average, during the busiest hour of the day, a certain call$-$centre makes $200$ outgoing calls of average duration $5$ minutes. During this hour, it receives $600$ incoming calls of average duration $10$ minutes. What is the approximate total traffic load of the call$-$centre in Erlangs?

$117$E

$217$E

$417$E

$317$E

$16.$ An $8000$ km trans$-$Pacific fibre optic link will use Erbium$-$doped fibre amplifiers $($EDFAs$)$ each with $30$ dB gain. Estimate how many EDFAs will be needed if the fibre attenuation is $0\mathrm{.}2$ dB$/$km$?$ You may assume that the transmitter power is $+15$ dBm and that the receiver requires a minimum signal power of $-25$dBm$.$

$32$

$52$

$62$

$42$

$17.$ A certain packet has a $16-$bit header. The transmission channel has a $10-6$ bit$-$error probability. What overall packet length in bits will maximize throughput efficiency?

$2000$

$3000$

$5000$

$4000$

$18.$ A pure ALOHA system uses a $64$bit$/$s channel. On average, each terminal generates a $1024-$bit packet every $40$ seconds. Approximately how many terminals can the system accommodate?

$225$

$1250$

$2250$

$125$

$19.$ What is the approximate ARQ$($ automatic repeat request$)$ stop$-$and wait channel utilization with $240$ ms roundtrip delay when $1000$ byte packets are transmitted at $1$Gbit$/$s$?$ All other factors may be neglected in the calculation.

$0\mathrm{.}001\%$

$3\backslash$times $10-6$

$0\mathrm{.}003\%$

$3\backslash$times $10-7$

$20.$ A certain Clos three$-$stage non$-$blocking switch has $1000$ input and $1000$ output connections. What is the approximate minimum number of cross$-$points required?

$69443$

$59443$

$79443$

$89443$

$21.$ What is the total loss of the optical fibre in the network in dB from hub to customer?

$600$

$150$

$225$

$125$

$22.$ what is the total dispersion of the optical network in ns from hub to customer when EDFAs are used?

$15$

$18$

$25$

$20$

$23.$ what is the total gain of the EDFAs in dB$?$

$40$

$100$

$80$

$20$

$24.$ what is the total dispersion of the optical network in ns from hub to customer when electronic regenerators are used?