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Computer Network Class/Exam2006_2


1. ฌธ œ  „  •„ค

•ˆ ๊ธฐ•—„œ •Œ๊ณ ฆฌฆ˜๊ณผ ž„ธ•œ ๊ตฌ˜„•— Œ€•œ ‚šฉ€ ๊ตˆ˜‹˜ €–‘•˜‹ “ฏ. (‚œ„ ‚ฎถ” ค๊ณ  •œ“ฏ•จ)
๊ฐœณ„ ธ ๊ธฐˆ ˜ ƒ„ธ ‚šฉ„ ๊ธฐ‹คŠ”  „ ๊ธฐˆ — Œ€•œ น„๊ต๊ณผ ฐจ — Œ€•œ •ฅผ ค‘‹ฌœผกœ ถœ œ.
(•œงˆ””กœ „“๊ฒŒ ๊ณต€••ผ ๊ฒฐ๊ณผ ข‹„“ฏ•จ.)

ธ„ฐ„ท •ˆ ๊€ จœ ฌธ œ—„œ ฌธ œกœ ถœ œ   งŒ•˜‹ค๊ณ  ƒ๊ฐ–ˆ˜ €ถ„ธ Authencation Protocol (3-way-handshake, keberos, using RSA)— Œ€•œ ‚šฉ—ญ‹œ ฏธถœ œ˜—ˆŒ. •ถ„— ‹œ—˜ ‚œ„Š” ‚ฎ•„กŒ€งŒ, PEM ˜ ๊ตฌกฐ— Œ€•œ „ค… “ค–๊ฐ”๊ธฐ •Œฌธ— ”ฐกœ ๊€‹ฌ„ ๊ฐ€€๊ณ  ๊ณต€•œ ‚ฌžŒ •„‹ˆ •ฝ๊ฐ„ – ค› „€„ ๊ฒ Œ.

TCP˜ ฆ„ œ– €ถ„€ ›Œ‚™— ค‘š”•˜‹ค๊ณ  „ค…–ˆ๊ธฐ •Œฌธ— SLOWSTART, FAST RETRANSMIT, VEGAS — Œ€•œ •ฅผ ••–ˆ„“ฏ.

2. ฌธ œ

1. •ˆ˜ ข…ฅ˜, นจž…ฐฉ•, ๊ทธ—”ฐฅธ •ˆ ๊ธฐ• ˜ˆ, ๊ฐ„‹จ•œ „ค…
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 „ค…๊ณผ ˆ˜—…•Œ ฐฐš •ˆ๊ธฐˆ “ค„ ถ„ฅ˜•˜๊ณ  „ค…•˜Š” ฌธ œž„.

2. €‹ฐฏธ””– ŠคŠธฆฌฐ „œน„Šค— ๊€ จœ ฌธ œ ถœ œ. (RTP, ฒ„ผง, QoS “ฑ˜ ฌธ œฅผ ณต•‹œผฐŒ)
2.1 playback time — Œ€•œ ฑ…—  œ‹œœ ๊ทธž˜”„ฅผ ๊ทธฆฌ๊ณ  ๊ทธ „ค…„ •˜Š” ฌธ œ. (2.1 ฌธ œ—„œŠ” MPEG ๊ณผ ๊ฐ™€ ••• ๊ธฐ• šฉ˜€ •ŠŠ”‹ค๊ณ  ๊ฐ€ •)
2.2 MPEG „ ‚ฌšฉ•˜ ๊ทธž˜”„๊ฐ€ ––๊ฒŒ €• ๊นŒ?
2.3 RTP —ค”— ฌ•˜Š” 3๊ฐœฅผ “ค–„œ „ค…
SSRC, CSRC, Contribution Count, timestamp, sequence number, Version etc —Œ€•œ ‚šฉ„  ๊ณ  •„ค
2.4 play back € —‡๊ณ  –ธ œ ––๊ฒŒ ‚ฌšฉ˜‚˜

  playback point, playback time — Œ€•œ •ฅผ Š” ฌธ œž„. adaptive playback —Œ€•œ ฌธ œ„ ถœ œ˜—ˆŒ.
2.5 €‹ฐฏธ””– „œน„Šค—„œ TCPŠ” ™œ ž˜ ‚ฌšฉ •ˆ ๊นŒ

  €‹ฐฏธ””– ŠคŠธฆฌฐ „œน„Šค™€ TCP˜ ๊ถ• ž˜ งž€•ŠŠ” œ ฅผ ๊ธฐˆ •˜ผŠ” ฌธ œ. ˆ˜—…‹œ๊ฐ„— ‡ฒˆ ง–ˆ๊ธฐ •Œฌธ— ‚œ„ ‰. (UDP œ„— RTP ฅผ ˜ฌฆฌ๊ฒŒ œ œ ™€ ผงฅƒ†ต•จ)

3. PEM œผกœ ฉ”ผ ‚ผ๊ฒฝšฐ, ‚€Š” ‚šฉ“ค ๊ตฌกฐ™€ •จ๊˜ „ค…. ๊ฐ™ ‚€Š” ฒจ€ ŒŒผ€ a.jpg
 ผฐ˜ ธ ฉ”ผ  „†ก ”„กœ† ฝœ˜ •™€ MIME ”„กœ† ฝœ— Œ€•œ ๊ฐ„‹จ•œ •. ๊ทธฆฌ๊ณ  E(MD(5), PrivateKeyOfSnd) ˜ •„ ฐฉ•๊ณผ ๊ณ„ธต  ธฆ— Œ€•œ •ฅผ Š” ฌธ œ˜€Œ.
 ฌธ œ˜ ‚šฉ— ฉ”ผ˜ —ค”™€ ๊ตฌกฐฅผ ‚˜ƒ€‚ผŠ” ง žˆ๊ธฐ 떄ฌธ— ฑ…„ ฐธกฐ•˜๊ฑฐ‚˜ ผฐ˜ œผกœ ฐ›Š” ฉ”ผ˜ ๊ตฌกฐฅผ •œฒˆ ณธ’ค ‹œ—˜„  ข‹Œ.
 (ง„„ ‚˜๊ฐ€๊ธฐ  „ ˆ˜—…•Œ ฉ”ผ ๊ตฌกฐ ๊ณ  ˜คผ๊ณ –ˆŠ”ฐ •„„ •ˆ๊ณ  ™€„œ ‚ธ“ฏ•จ. ใ…ก.ใ…ก)

4. slow start ‚˜˜คŠ” ๊ทธž˜”„
4.1 slow start ‘œ‹œ, —‡ธ€ „ค…

  SLOWSTART ‚ฌšฉ‹œ๊ธฐ™€ •‹น ๊ธฐ•˜ ‚ฌšฉœ — Œ€•œ •„ค
4.2 fast restrasntmit — Œ€•œ „ค…๊ณผ ๊ทธ ‡๊ฒŒ –ˆ„•Œ ๊ทธž˜”„๊ฐ€ ––๊ฒŒ €•˜‚˜?

  FRšฉ‹œ ๊ทธž˜”„˜ €™” ถ”™€ ๊ทธ œ ฅผ „ค…. ค‘ณต ACK  „†ก— Œ€•œ •ผ๊ธฐ™€ VEGAS—„œ š”•˜Š” faster retransmit „ค…–ˆŒ.

5. †ต•„œน„Šค™€, ฐจณ„ „œน„Šค˜  ‘๊ทผ•˜ ฐจฅผ “ฐ๊ณ  (Qos— ”ฐฅธ „œน„Šคฅผ  œ๊ณต•ฃผŠ” Œ€‘œ ธ ๊ธฐ•) ๊ฐ „œน„Šค—„œ WFQฅผ ––๊ฒŒ ๊ตฌ˜„–ˆŠ”€
 Integrated Service(flow-based), Differentiated Service(service-based) —Œ€•œ  „ฐ˜ ธ •ฅผ •˜Š” ฌธ œ. •‹น ๊ธฐ•— WFQฅผ  šฉ•˜Š” ฐฉ•— Œ€•œ •ฅผ Š” ฌธ œกœ •ฝ๊ฐ„ ‘šฉ•„œ  œผž€ ๊ฒƒœผกœ ž„. ฑ…— DS— Œ€•œ „ค…€ WRED, RIO— Œ€•œ „ค…งŒ ˜–žˆ—ˆ๊ณ ,  ฐฉ‹€ Queuing — ˜•œ WFQ˜ ‚ฌ›„ ฒ˜ฆฌ๊ฐ€ •„‹Œ ‚ฌ „ ฆฌ— ๊€ จœ ‚šฉ—ˆŒ. †”งžˆ WFQ ™œ ƒˆŠ”€ ๊ฒ Œ. -_-;;
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