Based on the following passage, answer the Questions: A 3000 km long trunk operates at 1.536 mbps and is used to transmit 64 bytes frames and uses sliding window protocol. The propagation speed is 6 μ sec/km.
For the link in the passage, use a data rate of 1.536 Mbps and interpret 6 μs/km as propagation delay per kilometre. Assume error-free Go-Back-N transmission with continuously available data. ACKs are sent immediately after complete frame reception on a separate return channel with the same propagation delay; ACK transmission and processing times are negligible. What is the minimum number of sequence-number bits needed to allow a sender window large enough for full forward-link utilization?
7 bits
Step 1 — Frame and propagation times:
\(T_t=\frac{64\times8}{1.536\times10^6}=\frac{1}{3000}\ \mathrm{s},\qquad T_p=3000\times6\times10^{-6}=0.018\ \mathrm{s}.\)
Step 2 — Window needed for continuous transmission: An ACK for the first frame returns after its transmission time plus the round-trip propagation delay.
\(a=\frac{T_p}{T_t}=54,\qquad W_{\mathrm{full}}=\left\lceil1+2a\right\rceil=109.\)
Step 3 — Sequence-number field: For Go-Back-N, the sender window must be smaller than the sequence-number space.
\(2^m-1\ge109.\)
\(2^6-1=63<109,\qquad2^7-1=127\ge109.\)
Thus the minimum is 7 bits.
Important Questions from Data Link Layer
If a file consisting of 50,000 characters takes 40 seconds to send, then the data rate is ______
Which one of the following functionality is not performed by data link layer?
- It is necessary to design a link-layer protocol between two hosts that are directly connected over a lossless link of length 3000 kilometers. Assume that the link bandwidth is $10^8$ bits per second and that the propagation delay in the link is 5 nanoseconds per meter. Every transmitted data byte is assigned a unique sequence number.
Let $N$ be the minimum number of bits needed for the sequence number field in the protocol header such that
i. the sequence numbers do not wrap around before 60 seconds, and
ii. the maximum utilization of the link is achieved.
The value of $N$ is ______. (answer in integer) In a LAN environment, switches improve network efficiency primarily by:
Which of the following protocols is responsible for converting higher level protocol addresses to physical network addresses?
