Homework Assignment 1 Due Sep 20 3 50 PM EE122 Introduction to Communication Networks Fall 2006 Department of Electrical Engineering and Computer Sciences College of Engineering University of California Berkeley Vern Paxson Sukun Kim Dilip Antony Joseph Turn in via email to binetude eecs berkeley edu Sukun Kim 1 Peterson Davie Exercises 1 13 1 15 1 18 2 Ping The ping program determines the round trip time RTT to any host in the Internet Using a computer on campus ping the following hosts cmu edu Pittsburgh PA mit edu Boston MA washington edu Seattle WA ucsd edu San Diego CA uchicago edu Chicago IL columbia edu New York NY odu edu Norfolk VA and www vanderbilt edu Nashville TN For each of these locations find the physical distance from Berkeley or San Francisco using http routesinternational com buslines htm distance and then compute the shortest possible time T to reach that location a Plot a graph where the X axis represents the distance to each city and the Y axis represents the ratio between the RTT as measured by the ping program and the shortest possible time T to reach that city Note that the Y values are no smaller than 2 since it takes at least 2T time for any packet to reach the destination and get back b Give two reasons of why the Y values you plot are larger than 2 3 RFCs The Request for Comments RFC documents define and standardize the bulk of the protocols used by the Internet They are published on behalf of the Internet Engineering Task Force IETF which forms the main standards body of the Internet If you want to understand a protocol in full detail especially to write your own implementation of it these are the documents to refer to a One of the RFCs defining Internet protocols concerns sending packets IP datagrams over carrier pigeons It was published as a part of the IETF s April Fools series but is written as though a true protocol and in fact appears to be implementable Search http rfc editor org to locate this document Hint 1 it doesn t actually mention pigeons Hint 2 find the first version of the standard not the later one that discusses Quality of Service for carrier pigeons Once you find the document read it and summarize in your own words what it says about the MTU Maximum Transmission Unit for such transmission i e the largest individual message that can be sent b A great strength of the IP protocol is how it provides the glue to communicate data over a series of widely varying lower layer network or link technologies Using http rfc editor org or whatever search means you want to use providing your work by yourself locate RFCs that refer to transmitting IP over XXX where XXX is some link technology For example RFC 1201 is Transmitting IP traffic over ARCNET networks List all the different lower layer networking technologies for which you can find an RFC whose title indicates it defines how to send IP packets or datagrams or traffic over that technology Give both the name of the technology and the RFC defining the transmission Extra credit find more lower layer networking technologies than the TAs did which was 21 when counting very similar entries like IP over 802 and IP over 802 3 as the same and allowing general entries like IP over public data networks to be counted 4 End to End Arguments Suppose you run a document delivery company BearsEx similar to Federal Express You re just starting out so currently you only deliver from Berkeley to New York Each package you handle is dropped off at your Berkeley office From there a driver takes it to Oakland airport where it s flown to Denver and then on from Denver to New York At New York a driver takes it straight to its destination in the city So a complete trip consists of the following hops 1 2 3 4 Berkeley OAK via truck At OAK from the drop off point to the plane OAK DEN via plane At DEN from the arriving plane to the connecting plane 5 DEN JFK via plane 6 At JFK from the arriving plane to the baggage claim 7 JFK destination via truck However you have problems with loss theft Indeed as packages are transported by truck drivers they re stolen 3 of the time When they are moving through airports they re stolen 2 of the time And when they re on airplanes they re lost 1 of the time a What s the likelihood that a package makes it to its destination b As CEO you are considering spending money to reduce all BearsEx theft loss rates to 0 05 Consider each of the following alternatives i Suppose that for the sender of a package the most important thing to them is that the package eventually gets there For lost packages the receiver notices after a day that it hasn t shown up and phones the sender who always sends it again until it finally arrives or ii Suppose that for the sender of a package the most important thing to them is that the package gets there the next day If it doesn t they will give up and look for a different document delivery company For each of these possibilities discuss what the End to End Principle would dictate regarding whether BearsEx should spend extra money to reduce the theft loss rates Ignore just how much money this would be versus other costs and prices The question here is the principle of whether to spend some money on improving the service
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