## Network Architecture

Network Architecture

Network Architecture

1. Suppose two hosts, A and B are separated by 80,000 kilometers and are connected by a direct link of R=1 Mbps. Suppose the propagation speed over the link is 2*108 meters/sec. Consider sending a file of 1,000,000 bits from Host A to Host B.

a. Suppose the file is sent continuously as one big message. How long does it take to send the file, assuming it is sent continuously?

b. Suppose now the file is broken up into 500 packets with each packet containing 2,000 bits. Suppose that each packet is acknowledged by the receiver and the transmission time of an acknowledgement packet is negligible. Finally, assume that the sender cannot send a packet until the preceding one is acknowledged. How long does it take to send the file?

c. If there are two routers between Host A and B (rather than a direct link), and all three links have 1 Mbps links, how long does it take to send the file? (use the assumptions in 1.b)

d. Calculate the bandwidth-delay product, R*tprop. What does it mean? (Provide an interpretation of the bandwidth-delay product.)

Laboratory Assignment

This portion of homework is to give you some hands-on experience which will help you to understand concepts that were or will be dealt in class.

These are OS shell commands or command-line commands. Use your terminal (Mac, Linux) or windows ‘cmd’ to run these on. You may use ‘script’ command (Mac/Linux terminal) or screen capture, to show your work.

2. Explore ‘ping’ and ‘traceroute’ (or ‘tracert’ on Windows) which are basic tools used to measure network performance and retrieve network status. Run ‘ping’ and ‘traceroute’ with at least three different hosts and options (eg. -h, -j, -w, -R, -t, -l, etc.). Record the commands and their output.

3. Explore ‘nslookup’ which is a program to query Internet domain name servers. Particularly,

a. Find out the ip address(es) of www.yahoo.com

b. Find out the name servers and their IP addresses of yahoo.com domain.

c. Find out the email servers and their IP addresses of yahoo.com domain.

d. Try two other options (i.e., different command parameters, not about changing the target name, eg. -timeout, -type). Record the commands and their output.

4. Explore IETF web page (www.ietf.org) and find out how many RFCs are there currently? Then, list at least 5 working groups. Among those working groups, choose one of them and summarize its activities in one page, i.e., objective of the charter, documents/issues published or discussed in the working group.