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Computer Network Class/Exam2006_2


1. ๋ฌธ œ  „ฒด  •„

๋ณด•ˆ ธฐ๋ฒ•—„œ •Œ ๋ฆฌ˜ณผ ž„•œ ตฌ˜„๋ฒ•— ๋Œ€•œ ๋‚ดšฉ€ ตˆ˜‹˜ง€–‘•˜‹ ๋“ฏ. (๋‚œด๋„ ๋‚ฎถ”๋   •œ๋“ฏ•จ)
œ๋ณ„ ธฐˆ ˜ ƒ„ธ ๋‚ดšฉ„ ๋ฌปธฐ๋ณด๋‹ค๋Š”  „ฒด ธฐˆ — ๋Œ€•œ ๋น„ตณผ ฐจ — ๋Œ€•œ •ด๋ฅผ ‘‹œผ๋กœ œ œ.
(•œ๋งˆ๋””๋กœ„“ฒŒ ณต๋ถ€••ฒฐณผ ‹„๋“ฏ•จ.)

„ฐ๋„ ๋ณด•ˆ ด€๋ จ๋œ ๋ฌธ œ—„œ ๋ฌธ œ๋กœ œ œ ๋  ๋งŒ•˜‹  ƒฐ–ˆ๋˜ ๋ถ€๋ถ„ธ Authencation Protocol (3-way-handshake, keberos, using RSA)— ๋Œ€•œ ๋‚ดšฉ—ญ‹œ ๋ฏธœ œ๋˜—ˆŒ. ๋•๋ถ„— ‹œ—˜ ๋‚œด๋„๋Š” ๋‚ฎ•„กŒง€๋งŒ, PEM ˜ ตฌกฐ— ๋Œ€•œ „ค๋ช…ด ๋“ค–ดฐ”ธฐ ๋•Œ๋ฌธ— ๋”ฐ๋กœ ด€‹„ ฐ€ง€  ณต๋ถ€•œ ‚ฌ๋žŒ•„‹ˆ๋ฉด •„ –ด๋ › „ง€๋„ ๋ชจ๋ฅด Œ.

TCP˜ ๋ฆ„ œ–ด ๋ถ€๋ถ„€ ›Œ๋‚™— ‘š”•˜‹  „ค๋ช…–ˆธฐ ๋•Œ๋ฌธ— SLOWSTART, FAST RETRANSMIT, VEGAS — ๋Œ€•œ •ด๋ฅผ ••–ˆ„๋“ฏ.

2. ๋ฌธ œ

1. ๋ณด•ˆ˜ ข…๋ฅ˜, นจž…๋ฐฉ๋ฒ•, —๋”ฐ๋ฅธ ๋ณด•ˆ ธฐ๋ฒ• ˜ˆ, „‹•œ „ค๋ช…
secrecy(interception -> DES, RSA)
authenticate(fabrication -> 3-way handshake, keberos, using RSA)
integrigy(modification -> keyed MD5)
availability(interruption, DoS, Jamming -> Firewall, Proxy-base Network System)— ๋Œ€•œ „ค๋ช…ณผ ˆ˜—…๋•Œ ๋ฐฐšด ๋ณด•ˆธฐˆ ๋“ค„ ๋ถ„๋ฅ˜•˜  „ค๋ช…•˜๋Š” ๋ฌธ œž„.

2. ๋ฉ€‹ฐ๋ฏธ๋””–ด ŠคŠธ๋ฆฌ๋ฐ „œ๋น„Šค— ด€๋ จ๋œ ๋ฌธ œ œ œ. (RTP, ๋ฒ„ผ๋ง, QoS ๋“ฑ˜ ๋ฌธ œ๋ฅผ ๋ณต•‹œผฐŒ)
2.1 playback time — ๋Œ€•œ ฑ…—  œ‹œ๋œ ธ๋ž˜”„๋ฅผ ธ๋ฆฌ  „ค๋ช…„ •˜๋Š” ๋ฌธ œ. (2.1 ๋ฌธ œ—„œ๋Š” MPEG ณผ ฐ™€ ••• ธฐ๋ฒ•šฉ๋˜ง€ •Š๋Š”๋‹  ฐ€ •)
2.2 MPEG „ ‚ฌšฉ•˜๋ฉด ธ๋ž˜”„ฐ€ –ด๋–ปฒŒ ๋ณ€• นŒ?
2.3 RTP —ค๋”— ฌ•จ๋˜๋Š” 3œ๋ฅผ ๋“ค–ด„œ „ค๋ช…
SSRC, CSRC, Contribution Count, timestamp, sequence number, Version etc —๋Œ€•œ ๋‚ดšฉ„    •„
2.4 play back € ๋ฌด—‡  –ธ œ –ด๋–ปฒŒ ‚ฌšฉ๋˜๋‚˜

  playback point, playback time — ๋Œ€•œ •ด๋ฅผ ๋ฌป๋Š” ๋ฌธ œž„. adaptive playback —๋Œ€•œ ๋ฌธ œ๋„ œ œ๋˜—ˆŒ.
2.5 ๋ฉ€‹ฐ๋ฏธ๋””–ด „œ๋น„Šค—„œ TCP๋Š” ™œ ž˜ ‚ฌšฉ •ˆ๋ นŒ

  ๋ฉ€‹ฐ๋ฏธ๋””–ด ŠคŠธ๋ฆฌ๋ฐ „œ๋น„Šค™€ TCP˜ ถ•ž˜ ๋งžง€•Š๋Š” œ ๋ฅผ ธฐˆ •˜ผ๋Š” ๋ฌธ œ. ˆ˜—…‹œ„— ๋ช‡๋ฒˆ ๋ง–ˆธฐ ๋•Œ๋ฌธ— ๋‚œด๋„ ‰ด. (UDP œ„— RTP ๋ฅผ ˜ฌ๋ฆฌฒŒ ๋œ œ ™€ ผ๋งฅƒ†ต•จ)

3. PEM œผ๋กœ ด๋ฉ”ผ ๋ณด๋‚ผฒฝšฐ, ๋ณด๋‚ดง€๋Š” ๋‚ดšฉ๋“ค ตฌกฐ™€ •˜ „ค๋ช…. ฐ™ด ๋ณด๋‚ดง€๋Š” ฒจ๋ถ€ ŒŒ€ a.jpg
 ผ๋ฐ˜ ธ ๋ฉ” „†ก ”„๋กœ† œ˜ •™€ MIME ”„๋กœ† œ— ๋Œ€•œ „‹•œ •ด. ธ๋ฆฌ  E(MD(5), PrivateKeyOfSnd) ˜ •„ ๋ฐฉ๋ฒ•ณผ „ธต  — ๋Œ€•œ •ด๋ฅผ ๋ฌป๋Š” ๋ฌธ œ˜€Œ.
 ๋ฌธ œ˜ ๋‚ดšฉ— ๋ฉ”˜ —ค๋”™€ ตฌกฐ๋ฅผ ๋‚˜ƒ€๋‚ด๋ผ๋Š” ๋งžˆธฐ 떄๋ฌธ— ฑ…„ ฐธกฐ•˜ฑฐ๋‚˜ ผ๋ฐ˜ œผ๋กœ ๋ฐ›๋Š” ด๋ฉ”˜ ตฌกฐ๋ฅผ •œ๋ฒˆ ๋ณธ๋’ค ‹œ—˜„ ๋ณด๋ฉด ‹Œ.
 („๋„ ๋‚˜ฐ€ธฐ  „ ˆ˜—…๋•Œ ๋ฉ”ตฌกฐ ๋ณด  ˜ค๋ –ˆ๋Š”๋ฐ •„๋ฌด๋„ •ˆ๋ณด  ™€„œ ๋‚ธ๋“ฏ•จ. ใ…ก.ใ…ก)

4. slow start ๋‚˜˜ค๋Š” ธ๋ž˜”„
4.1 slow start ‘œ‹œ, ๋ฌด—‡ง€ „ค๋ช…

  SLOWSTART ‚ฌšฉ‹œธฐ™€ •ด๋‹ธฐ๋ฒ•˜ ‚ฌšฉœ — ๋Œ€•œ •„
4.2 fast restrasntmit — ๋Œ€•œ „ค๋ช…ณผ ธ๋ ‡ฒŒ –ˆ„•Œ ธ๋ž˜”„ฐ€ –ด๋–ปฒŒ ๋ณ€•˜๋‚˜?

  FRšฉ‹œ ธ๋ž˜”„˜ ๋ณ€™” ถ”™€ œ ๋ฅผ „ค๋ช…. ‘๋ณต ACK  „†ก— ๋Œ€•œ •ธฐ™€ VEGAS—„œ š”•˜๋Š” faster retransmit „ค๋ช…–ˆŒ.

5. †ต•„œ๋น„Šค™€, ฐจ๋ณ„ „œ๋น„Šค˜  ‘ผ๋ฒ•˜ ฐจด๋ฅผ “ฐ  (Qos— ๋”ฐ๋ฅธ „œ๋น„Šค๋ฅผ  œณต•ฃผ๋Š” ๋Œ€‘œ ธฐ๋ฒ•) ฐ „œ๋น„Šค—„œ WFQ๋ฅผ –ด๋–ปฒŒ ตฌ˜„–ˆ๋Š”ง€
 Integrated Service(flow-based), Differentiated Service(service-based) —๋Œ€•œ  „๋ฐ˜ •ด๋ฅผ •˜๋Š” ๋ฌธ œ. •ด๋‹ธฐ๋ฒ•— WFQ๋ฅผ  šฉ•˜๋Š” ๋ฐฉ๋ฒ•— ๋Œ€•œ •ด๋ฅผ ๋ฌป๋Š” ๋ฌธ œ๋กœ •„ ‘šฉ•„œ  œผ๋ž€ ฒƒœผ๋กœ ๋ณดž„. ฑ…— DS— ๋Œ€•œ „ค๋ช…€ WRED, RIO— ๋Œ€•œ „ค๋ช…๋งŒ ๋˜–ดžˆ—ˆ , ด ๋ฐฉ‹€ Queuing — ˜•œ WFQ˜ ‚ฌ›„ ˜๋ฆฌฐ€ •„‹Œ ‚ฌ „ ฒด๋ฆฌ— ด€๋ จ๋œ ๋‚ดšฉ—ˆŒ. †”งžˆ WFQ ™œ ๋ƒˆ๋Š”ง€ ๋ชจ๋ฅด Œ. -_-;;
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