HW#1 --- last modified February 14 2023 01:49:58.

Solution set.

Due date: Feb 13

Files to be submitted:
  Hw1.zip

Purpose: To get familiar with common network measuring concepts, to learn about common networking tools.

Related Course Outcomes:

The main course outcomes covered by this assignment are:

LO3 -- Analyze the performance metrics of networks, including bandwidth, delay, and error rate.

LO9 -- Use networking tools including telnet, ping, traceroute, bing, and Ethereal to evaluate simple network characteristics.

Specification:

Remember to include in your Hw1.zip a readme.txt listing all your teammates! This homework will consist of the following five short exercise/experiment write-up (2-5 modified from book).

1. In the 1990s, the Gophersphere, based on the Gopher Protocol, was a potential alternative protocol to HTTP and the world wide web. Read up on this protocol, then using the telnet command line tool, make a connection to pollett.org on port 70 and request the main gopher page there. Submit as solution to this problem a transcript of the messages exchanged between you and the server.
2. Calculate the total time required to transfer a 1500kB file in the following cases, assuming an RTT of 200 ms, a packet size of 4 kB data, and an initial 2 x RTT of "handshaking" before data are sent.
   1. The bandwidth is 2.5 Mbps, and data packets can be sent continuously.
   2. The bandwidth is 2.5 Mbps, but after we finish sending each data packet, we must wait one RTT before sending the next.
   3. The bandwidth is "infinite," meaning that we take transmit time to be zero, and up to 10 packets can be sent per RTT.
   4. The bandwidth is infinite, and during the first RTT, we can send one packet (2¹ - 1), during the second RTT we can send two packets (2^{2- 1} ), during the third we can send four (2^{3 - 1}), and so on.
3. Consider a point-to-point link 75 km in length. At what bandwidth would propagation delay (at a speed of 2 x 10⁸ m/sec) equal transmit delay for 256-byte packets? What about 1024-byte packets?
4. Calculate the latency (from first bit sent to last bit received) for the following: (a) 100-Mbps Ethernet with a single store-and-forward switch in the path and a packet size of 4000 bits. Assume that each link introduces a propagation delay of 5 µs and that the switch begins retransmitting immediately after it has finished receiving the packet. (b) Same as (a) but with three switches. (c) Same as (a) but assume the switch implements "cut-through" switching: it is able to begin retransmitting the packet after the first 150 bits have been received.
5. Suppose a shared medium `M` offers to hosts `A_1,A2,...,A_N` in round - robin fashion an opportunity to transmit one packet; hosts that have nothing to send immediately relinquish M. How does this differ from STDM? How does network utilization of this scheme compare with STDM?

Point Breakdown