i ➥ inserting a ‘0’ in user stream to differentiate it with a flag
ii ➥ inserting a ‘0’ in flag stream to avoid ambiguity
iii ➥ appending a nibble to the flag sequence
iv ➥ appending a nibble to the use data stream
Q37➡| In cryptography, the following uses transposition cyphers and the keyword is LAYER. Encrypt the following message. (Spaces are omitted during encryption) WELCOME TO NETWORK SECURITY!
i ➥ WMEKREETSILTWETCOOCYONRU!
ii ➥ EETSICOOCYWMEKRONRU!LTWET
iii ➥ LTWETONRU!WMEKRCOOCYEETSI
iv ➥ ONRU!COOCYLTWETEETSIWMEKR
Q38➡| Station A uses 32-byte packets to transmit messages to Station B using a sliding window protocol. The round trip delay between A and B is 80 ms and the bottleneck bandwidth on the path between A and B is 128 kbps. What is the optimal window size that A should use?
i ➥ 20
ii ➥ 40
iii ➥ 160
iv ➥ 320
Q39➡| A 20 Kbps satellite link has a propagation delay of 400 ms. The transmitter employs the “go back n ARQ” scheme with n set to 10. Assuming that each frame is 100 bytes long, what is the maximum data rate possible?
i ➥ 5 Kbps
ii ➥ 10 Kbps
iii ➥ 15 Kbps
iv ➥20 Kbps
Q40➡| In a sliding window ARQ scheme, the transmitter’s window size is N and the receiver’s window size is M. The minimum number of distinct sequence numbers required to ensure correct operation of the ARQ scheme is