1. Tutorial 1

2. Q1
1- A company has an internet address /22 and want to divide this block of addresses to 8 equal blocks ( subnets) /

3. In the subnetting, the number of bits added to the mask could be calculated as: #of bits = log2 ( #of subnets) = log2 ( 8) =

4. Subnet1
/25
27= 256
Subnet2
/25
Subnet3
/25
Subnet4
/25
Subnet5
/25
Subnet6
/25
Subnet7
/25
Subnet8
/25

5. Q2 2-Channel with BW = 3 Mbps
Calculate the utilization in a go-back-in protocol(with window size =31 ) with a 10KByte packet.
Utilization=(total data in bits/bandwidth) *100
=((31*10*1000*8)/3* )*100

6. How could you increase the utilization in this system By increasing the packet size or increasing the window size or both

7. Q3
3-In a ring topology : What is the difference between ring and dual ring if one of the links damaged ? Damage in ring topology stops the entire network Link damage in dual ring redirects the traffic in to the opposite side

8. Show the fault management steps in ring topology?
Detecting the damaged link
Isolating the fault by removing the damaged link and reconnect the rest of network
Correcting the fault by replacing the link and reconnect the network
Documenting the fault

9. Q4 4- A component with a MTBF of 8 days and a MTTR of 3 hours .
Calculate the availability.
Availability = MTBF / (MTBF + MTTR)
= 8*24/(8*24+3)

10. How could you increase the availability. prove that
How could you increase the availability ?prove that. By decreasing the MTTR

11. 5- Calculate the channel capacity if the Bandwidth is 5KHz and the SNR is 100 and find Two different ways to increase the capacity. C=Blog(1+SNR) =5*1000 log(1+100) bps

12. Q6
6- What is the transmission time if the distance between the two points is 24,000 km, the propagation speed is 2.4 × 108 m/s, queuing time and processing time is zero and latency is 1s? Latency = propagation time + transmission time+ queuing time + processing time Propagation time = distance/propagation speed Transmission time=packet size/ BW

13. 7- A system with 5 replica managers :
Draw the system if an active replication is applied?
Draw the system if a passive replication is applied?
Calculate the availability if there is 7% probability of a replica manager failure.
Calculate the availability if we use just a single server.

14. Draw the system if an active replication is applied?RM FE C RM RM

15. Draw the system if a passive replication is applied?FE C RM
Primary
Backup RM RM

16. Calculate the availability if there is 7% probability of a replica manager failure.
A=1-Probability(all managers failed or unreachable)=1-pn
P=0.07
N=5
A= 1-pn = 1-(0.07)5 = =0.999=99.9%

17. Calculate the availability if we use just a single server. P=0.07 N=1
A=1-Probability(all managers failed or unreachable)=1-pn
P=0.07
N=1
A= 1-pn = 1-(0.07)1 =0.93=93%

18. 8- If the time required to open a certain page from the browser cache is 500ms , proxy cache is 2555ms and web server cache is 5000ms fill in the table below
Action
The proximate time required
PC1 requests the page for the first time
5000ms
PC2 requests the page for the first time
2555ms
PC1 requests the page for the second time
500ms
PC2 requests the page for the second time

19. 2- If the time required to open a certain page from the browser cache is 500ms , proxy cache is 2555ms and web server cache is 5000ms fill in the table below