King Saud University College of Computer and Information Sciences

Department of Information TechnologyIT332 – Distributed Systems Second Semester 1434/1435 H

Tutorial #2 Due Date: Wed 1st April (09:59am)

N.B: To be submitted individually to the course email. Late and handwritten solutions will not be accepted.

Q.1 A client makes remote procedure calls to a server. The client takes 5 milliseconds to compute the arguments for each request, and the server takes 10 milliseconds to process each request. The local operating system processing time for each send or receive operation is 0.5 milliseconds, and the network time to transmit each request or reply message is 3 milliseconds. Marshaling (or unmarshaling) takes 0.5 milliseconds per message.Calculate the time taken by the client to generate and return from two requests, in case it has two threads that can make requests concurrently on a single processor. You can ignore context-switching times.

Q.2 If a communication paradigm is asynchronous, is it also time decoupled? Explain your answer with examples as appropriate.

Q.3 When searching for files in an unstructured peer-to-peer system, it may help to restrict the search to nodes that have similar files as you. Explain how gossiping can help to find those nodes.

Q.4 Consider the following Chord-based P2P system: a) Determine where the files with key values 10, 19, 20 and 30 will be stored. b) Resolve the following key lookups:

Key 15 starting from node 4 Key 22 starting from node 4 Key 18 starting from node 20

c) Adjust the finger tables of nodes 18 and 14 when a node with ID 24 enters the ring. Also give the finger table of node 24.

Q.5 Using existing Bit-torrent client software, create and share a torrent file with either your friends (privately) or with anyone (publicly). You should see your upload rate start to increase with every peer that begins to download from you. Submit print screen for your work.Notes: No programming is needed; you can use any BitTorrent client with built in embedded tracker to share files.

Q.6 Consider the WordCount program we ran at the lab, you are required to extend it to count Bigrams. Bigrams are simply sequences of two consecutive words. For example, the previous sentence contains the following bigrams: "Bigrams are", "are simply", "simply sequences", "sequence of", etc. Submit your .java program and print screen of your output.