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Computer Network Class/Exam2006_2


1. ฌธ œ  „ฒด  ํ•ด„

ณด•ˆ ธฐฒ•—„œ •Œณ ฆฌฆ˜ ž„ธํ•œ ตฌํ˜„ฒ•— Œ€ํ•œ ‚ดšฉ€ ตˆ˜‹˜ด €–‘ํ•˜‹ “. (‚œด„ ‚ฎถ” คณ  ํ•œ“ํ•จ)
ฐœ„ ธ ธฐˆ ˜ ƒ„‚ดšฉ„ ฌปธฐณด‹คŠ”  „ฒด ธฐˆ — Œ€ํ•œ „ต ฐจด — Œ€ํ•œ ดํ•ด ค‘‹ฌœกœ ถœ œ.
(ํ•œงˆ””กœ „“ฒŒ ณต€ํ•ด• ฒฐ ข‹„“ํ•จ.)

ธํ„„ณด•ˆ € จœ ฌธ œ—„œ ฌธ œกœ ถœ œ   งŒํ•˜‹คณ  ƒฐํ–ˆ˜ €„ธ Authencation Protocol (3-way-handshake, keberos, using RSA)— Œ€ํ•œ ‚ดšฉ—ญ‹œ ถœ œ˜—ˆŒ. •„— ‹œํ—˜ ‚œด„Š” ‚ฎ•„กŒ€งŒ, PEM ˜ ตฌกฐ— Œ€ํ•œ „ช…ด “ค–ดฐ”ธฐ •Œฌธ— ”ฐกœ €‹ฌ„ €€ณ  ณต€ํ•œ ‚ฌžŒด •„‹ˆฉด •ฝ„ –ด ค› „€„ ชจฅดฒ Œ.

TCP˜ ํ„ œ–ด €„€ ›Œ‚™— ค‘š”ํ•˜‹คณ  „ช…ํ–ˆธฐ •Œฌธ— SLOWSTART, FAST RETRANSMIT, VEGAS — Œ€ํ•œ ดํ•ด ํ•ด•ํ–ˆ„“.

2. ฌธ œ

1. ณด•ˆ˜ ข…ฅ˜, ž…ฐฉฒ•, ทธ—”ฐฅธ ณด•ˆ ธฐฒ• ˜ˆ, „‹จํ•œ „ช…
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 „ช… ˆ˜—…•Œ ฐฐšด ณด•ˆธฐˆ “ค„ „ฅ˜ํ•˜ณ  „ช…ํ•˜Š” ฌธ œž„.

2. €ํ‹ฐ””–ด ŠคํŠธฆฌฐ „œ„Šค— € จœ ฌธ œ ถœ œ. (RTP, „ํง, QoS “˜ ฌธ œ ณตํ•ฉ‹œŒ)
2.1 playback time — Œ€ํ•œ …—  œ‹œœ ทธž˜ํ”„ ทธฆฌณ  ทธ „ช…„ ํ•˜Š” ฌธ œ. (2.1 ฌธ œ—„œŠ” MPEG ฐ™€ ••ถ• ธฐฒ•ด ดšฉ˜€ •ŠŠ”‹คณ  € •)
2.2 MPEG „ ‚ฌšฉํ•˜ฉด ทธž˜ํ”„€ –ด–ปฒŒ €ํ• Œ?
2.3 RTP ํ—ค”— ํฌํ•จ˜Š” 3ฐœ “ค–ด„œ „ช…
SSRC, CSRC, Contribution Count, timestamp, sequence number, Version etc —Œ€ํ•œ ‚ดšฉ„  ณ  ํ•ด„
2.4 play back € ฌด—‡ดณ  –ธ œ –ด–ปฒŒ ‚ฌšฉ˜‚˜

  playback point, playback time — Œ€ํ•œ ดํ•ด ฌปŠ” ฌธ œž„. adaptive playback —Œ€ํ•œ ฌธ œ„ ถœ œ˜—ˆŒ.
2.5 €ํ‹ฐ””–ด „œ„Šค—„œ TCPŠ” ™œ ž˜ ‚ฌšฉ •ˆ Œ

  €ํ‹ฐ””–ด ŠคํŠธฆฌฐ „œ„Šค™€ TCP˜ ถํ•ฉด ž˜ งž€•ŠŠ” ดœ  ธฐˆ ํ•˜Š” ฌธ œ. ˆ˜—…‹œ„— ช‡ฒˆ งํ–ˆธฐ •Œฌธ— ‚œด„ ํ‰ด. (UDP œ„— RTP  ˜ฌฆฌฒŒ œ ดœ ™€ งฅƒํ†ตํ•จ)

3. PEM œกœ ดฉ” ณด‚ฒฝšฐ, ณด‚ด€Š” ‚ดšฉ“ค ตฌกฐ™€ ํ•จป˜ „ช…. ฐ™ด ณด‚ด€Š” ฒจ€ ํŒŒ€ a.jpg
 ฐ˜ ธ ฉ”  „†ก ํ”„กœํ† ฝœ˜ ดํ•ด™€ MIME ํ”„กœํ† ฝœ— Œ€ํ•œ „‹จํ•œ ดํ•ด. ทธฆฌณ  E(MD(5), PrivateKeyOfSnd) ˜ ํ•ด„ ฐฉฒ• „ธต  ธฆ— Œ€ํ•œ ดํ•ด ฌปŠ” ฌธ œ˜€Œ.
 ฌธ œ˜ ‚ดšฉ— ฉ”˜ ํ—ค”™€ ตฌกฐ ‚˜ํƒ€‚ดŠ” งด žˆธฐ 떄ฌธ— …„ ฐธกฐํ•˜‚˜ ฐ˜ œกœ ฐ›Š” ดฉ”˜ ตฌกฐ ํ•œฒˆ ณธ’ค ‹œํ—˜„ ณดฉด ข‹Œ.
 („„ ‚˜€ธฐ  „ ˆ˜—…•Œ ฉ” ตฌกฐ ณดณ  ˜คณ ํ–ˆŠ”ฐ •„ฌด„ •ˆณดณ  ™€„œ ‚ธ“ํ•จ. ใ…ก.ใ…ก)

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

  SLOWSTART ‚ฌšฉ‹œธฐ™€ ํ•ด‹ ธฐฒ•˜ ‚ฌšฉดœ — Œ€ํ•œ ํ•ด„
4.2 fast restrasntmit — Œ€ํ•œ „ช… ทธ ‡ฒŒ ํ–ˆ„•Œ ทธž˜ํ”„€ –ด–ปฒŒ €ํ•˜‚˜?

  FRดšฉ‹œ ทธž˜ํ”„˜ €ํ™” ถ”ด™€ ทธ ดœ  „ช…. ค‘ณต ACK  „†ก— Œ€ํ•œ ด•ธฐ™€ VEGAS—„œ ดš”ํ•˜Š” faster retransmit „ช…ํ–ˆŒ.

5. ํ†ตํ•ฉ „œ„Šค™€, ฐจ„ „œ„Šค˜  ‘ฒ•˜ ฐจด “ฐณ  (Qos— ”ฐฅธ „œ„Šค  œณตํ•ดŠ” Œ€ํ‘œ ธ ธฐฒ•) ฐ „œ„Šค—„œ WFQ –ด–ปฒŒ ตฌํ˜„ํ–ˆŠ”€
 Integrated Service(flow-based), Differentiated Service(service-based) —Œ€ํ•œ  „ฐ˜ ธ ดํ•ด ํ•˜Š” ฌธ œ. ํ•ด‹ ธฐฒ•— WFQ  šฉํ•˜Š” ฐฉฒ•— Œ€ํ•œ ดํ•ด ฌปŠ” ฌธ œกœ •ฝ„ ‘šฉํ•ด„œ  œž€ ฒƒœกœ ณดž„. …— DS— Œ€ํ•œ „ช…€ WRED, RIO— Œ€ํ•œ „ช…งŒ ˜–ดžˆ—ˆณ , ด ฐฉ‹€ Queuing — ˜ํ•œ WFQ˜ ‚ฌํ›„ ฒ˜ฆฌ€ •„‹Œ ‚ฌ „ ฒดฆฌ— € จœ ‚ดšฉด—ˆŒ. †”งํžˆ WFQ ™œ ƒˆŠ”€ ชจฅดฒ Œ. -_-;;
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