a5sp06solutions

# a5sp06solutions - CS 414 Assignment 5 Solutions 3 points...

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CS 414 Assignment 5 Solutions 3 points per answer for 3a-g, 10 points per answer for 4a-c, 5a-b, 12 points for 2 and 14 points for 1 (100 max). Due Wednesday April 05. 1. In TCP slow start, at first the sending host will double the number of packets it sends every time it receives all acknowledgements for the previous packets it sent. In other words, the sending host will send one packet, receive the ACK for that packet, send two packets, receive the ACKs for those packets, send four packets, and so on. This exponential growth continues until there is a packet loss. (Subsequent to this loss, the sending host will increase the number of packets linearly, not exponen- tially.) Consider the scenario where a host H1 has two connections, one to a host HL on the same LAN, and one to a host HW thousands of miles away. The one-way latency to host HL is 1 micro-second, the one-way latency to host HW is 50 milli-seconds and the round-trip latency is twice the one-way latency. Assuming no packet losses, and assuming near-infinite bandwidth and processing speeds at all hosts, how long does it take to send the first 1023 packets to each host? Solution Since there is no packet loss, the number of packets sent in a window grows exponentially. So it takes 10 send-ACK cycles to send the 1023 packets (1,ACK,2,ACK,4,ACK,...,512,ACK and TCP send is not complete unless ACK is received). This comes to 20 micro-seconds for HL and 1 second for HW. 2. The operating system uses segmentation with paging. The virtual address is 32-bits long. Consider the scenario where a process has 6 segments with bases and limits given below: Base Limit (base 16) 0 0e457000 0100 1 2a983400 8000 2 7c567000 1040 3 0e468800 4008 4 0c945c00 0810 5 0e756900 1000 Assume a page size of 1KB (1024 bytes). What is the size of the page table (number of entries) and

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• Spring '06
• BIRMAN
• Virtual memory, page faults, internal fragmentation, page size

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