affairs of state or diplomatic occasions 2. the original draft of a diplomatic document, especially of the terms of a treaty agreed to in conference and signed by the parties 3. a formal or official record of scientific experimental observations 4. Computing a set of rules governing the exchange or transmission of data between devices — “Oxford Dictionary of English” 2022 1-2 — 2022-06-06 – p.42/78
things a complex system of railways, roads, or other routes: the railway network a group of people who exchange information and contacts for professional or social purposes: a support network . . . a number of interconnected computers, machines, or operations: a computer network . . . — “Oxford Dictionary of English” 2022 1-2 — 2022-06-06 – p.45/78
Keio Univ. Two among the best private universities in Japan These two universities are known for their rivalry and matches in baseball and other sports known as “ ” (first characters of Waseda, Keio and match), although Keio students would often call it “ ” ;) For undergraduates, classes may have to be cancelled for students to go cheer on the baseball team Story The head of the Keio cheerleading squad sends a letter of challenge in the form of a traditional scroll to the head of Waseda’s cheerleading squad It is a very long scroll that has to be untied from Keio’s Mita campus, slipped into Mita Station on the Mita Line, and then slipped out from Waseda Station on the Tozai Line to reach the Waseda campus so that the head of Waseda’s cheerleading squad can read it This is a metaphor of stream communication over the Internet as we do it via Zoom at the class Two ways TCP (Transmission Control Protocol) . . . Don’t miss reading every word of it (e.g. browsing a web page) UDP (User Datagram Protocol) . . . Well, it’s a long scroll, and it’s okay if it’s missing parts (e.g. Zoom) 2022 1-2 — 2022-06-06 – p.52/78
way, inside the entrance of Mita Station, there is a photocopier, which copies just part of the scroll at a time, and students pass through the ticket gate with one fragment each in their hand Each fragment is sequentially numbered from the top of the scroll Students are not familiar with the railway network, and when they ask the station staff how to get to Waseda, they are told to go to Otemachi, so they do Students ask again at Otemachi Station (router), and are told to change to the Tozai Line When they arrive at Waseda Station, a student operates a scanner/printer before the exit, scanning the fragments in numerical order and outputting a long scroll on the printer, and students pull it to the Waseda campus Now, some students may get lost on the way What would you do? 2022 1-2 — 2022-06-06 – p.53/78
TCP Students pick up their receipts (with fragment #) at Waseda Station and take them back to Mita Station At Mita Station, if a receipt is not returned, it is assumed that the fragment was not delivered, and another student is sent out with the fragment UDP Why do we care if some students are lost? (They are grown up, and we are certain that they will make it to their home) 2022 1-2 — 2022-06-06 – p.54/78
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