Encapsulation and Decapsulation

Reference: [์ฑ…] IT ์—”์ง€๋‹ˆ์–ด๋ฅผ ์œ„ํ•œ ๋„คํŠธ์›Œํฌ ์ž…๋ฌธ

  • ์ƒ์œ„ ๊ณ„์ธต์—์„œ ํ•˜์œ„ ๊ณ„์ธต์œผ๋กœ data๋ฅผ ๋ณด๋‚ด๋ฉด Physical Layer์—์„œ ์ „๊ธฐ ์‹ ํ˜ธ ํ˜•ํƒœ๋กœ network๋ฅผ ํ†ตํ•ด ์‹ ํ˜ธ๋ฅผ ๋ณด๋‚ธ๋‹ค

  • ๋ฐ›๋Š” ์ชฝ์—์„œ๋Š” ๋‹ค์‹œ ํ•˜์œ„ ๊ณ„์ธต์—์„œ ์ƒ์œ„ ๊ณ„์ธต์œผ๋กœ data๋ฅผ ๋ณด๋‚ธ๋‹ค

    • ์ด๋ ‡๊ฒŒ data๋ฅผ ๋ณด๋‚ด๋Š” ๊ณผ์ •์„ Encapsulation, ๋ฐ›๋Š” ๊ณผ์ •์„ Decapsulation์ด๋ผ๊ณ  ๋ถ€๋ฅธ๋‹ค

encapsulation and de-encapsulation in tcp/ip model

  • ํ˜„๋Œ€ network๋Š” ๋Œ€๋ถ€๋ถ„ packet๊ธฐ๋ฐ˜ network์ด๋‹ค

    • packet network๋Š” data๋ฅผ packet์ด๋ผ๋Š” ์ž‘์€ ๋‹จ์œ„๋กœ ์ชผ๊ฐœ ๋ณด๋‚ด๋Š”๋ฐ,

      • ์ด๋Ÿฐ ๊ธฐ๋ฒ•์œผ๋กœ ํ•˜๋‚˜์˜ ํ†ต์‹ ์ด ํšŒ์„  ์ „์ฒด๋ฅผ ์ ์œ ํ•˜์ง€ ์•Š๊ณ  ๋™์‹œ์— ์—ฌ๋Ÿฌ ๋‹จ๋ง์ด ํ†ต์‹ ํ•˜๋„๋ก ํ•ด์ค€๋‹ค

    • data๋ฅผ packet์œผ๋กœ ์ชผ๊ฐœ๊ณ  network๋ฅผ ์ด์šฉํ•ด ๋ชฉ์ ์ง€๋กœ ๋ณด๋‚ด๊ณ , ๋ฐ›๋Š” ์ชฝ์—์„œ๋Š” ๋‹ค์‹œ ํฐ data ํ˜•ํƒœ๋กœ ๊ฒฐํ•ฉํ•ด ์‚ฌ์šฉํ•œ๋‹ค

Encapsulation

  • application์—์„œ data๋ฅผ **Data Flow Layer (1~4์ธต)**๋กœ ๋‚ด๋ ค๋ณด๋‚ด๋ฉด์„œ packet์— data๋ฅผ ๋„ฃ์„ ์ˆ˜ ์žˆ๋„๋ก ๋ถ„ํ• ํ•˜๋Š”๋ฐ, ์ด ๊ณผ์ •์„ Encapsulation์ด๋ผ๊ณ  ํ•œ๋‹ค

  • network ์ƒํ™ฉ์„ ๊ณ ๋ คํ•ด ์ ์ ˆํ•œ ํฌ๊ธฐ๋กœ data๋ฅผ ์ชผ๊ฐœ๊ณ , ์œ„์˜ ๊ทธ๋ฆผ์ฒ˜๋Ÿผ 4๊ณ„์ธต (Transport Layer)๋ถ€ํ„ฐ ๋„คํŠธ์›Œํฌ ์ „์†ก์„ ์œ„ํ•œ ์ •๋ณด๋ฅผ header์— ๋ถ™์—ฌ ๋„ฃ๋Š”๋‹ค

    • header ์ •๋ณด๋Š” 4๊ณ„์ธต, 3๊ณ„์ธต, 2๊ณ„์ธต์—์„œ ๊ฐ๊ฐ ์ž์‹ ์ด ํ•„์š”ํ•œ ์ •๋ณด๋ฅผ ์ถ”๊ฐ€ํ•˜๋Š”๋ฐ ์ด ์ •๋ณด๋Š” ๋ฏธ๋ฆฌ ์ •์˜๋œ bit ๋‹จ์œ„ (0๋˜๋Š” 1)๋กœ ์“ด๋‹ค

      • 4๊ณ„์ธต์—์„œ header๋ฅผ ์ถ”๊ฐ€ํ•˜๊ณ  3๊ณ„์ธต์œผ๋กœ ๋‚ด๋ ค๋ณด๋‚ด๋ฉด 3๊ณ„์ธต์—์„œ ํ•„์š”ํ•œ header๋ฅผ ์ถ”๊ฐ€ํ•˜๊ณ  2๊ณ„์ธต์œผ๋กœ ๋‚ด๋ ค๋ณด๋‚ธ๋‹ค

      • 2๊ณ„์ธต์—์„œ๋„ ํ•„์š”ํ•œ ์ •๋ณด๋ฅผ header์— ์ถ”๊ฐ€ํ•œ ํ›„ ์ „๊ธฐ ์‹ ํ˜ธ๋กœ ๋ณ€ํ™˜ํ•ด ์ˆ˜์‹ ์ž์—๊ฒŒ ์ „์†กํ•œ๋‹ค

  • data๋ฅผ ์ „์†กํ•˜๋Š” ์ž‘์—…์€ ์ƒ๊ฐ๋ณด๋‹ค ๋ณต์žกํ•ด์„œ data flow layer (1~4๊ณ„์ธต) ์—์„œ๋งŒ 3๊ฐœ์˜ header ์ •๋ณด๊ฐ€ ์ถ”๊ฐ€๋œ๋‹ค

Decapsulation

  • data๋ฅผ ๋ฐ›๋Š” ์ชฝ์—์„œ๋Š” Decapsulation ๊ณผ์ •์„ ์ˆ˜ํ–‰ํ•œ๋‹ค

  • ๋ฐ›์€ ์ „๊ธฐ ์‹ ํ˜ธ๋ฅผ data ํ˜•ํƒœ๋กœ ๋งŒ๋“ค์–ด 2๊ณ„์ธต์œผ๋กœ ์˜ฌ๋ ค๋ณด๋‚ธ๋‹ค

  • 2๊ณ„์ธต์—์„œ๋Š” ์†ก์‹ ์ž๊ฐ€ ์ž‘์„ฑํ•œ 2๊ณ„์ธต header์— ํฌํ•จ๋œ ์ •๋ณด๋ฅผ ํ™•์ธํ•œ๋‹ค

    • ๋งŒ์•ฝ 2๊ณ„์ธต์— ์ ํžŒ ์ •๋ณด ์ค‘ ๋ชฉ์ ์ง€๊ฐ€ ์ž์‹ ์ด ์•„๋‹ˆ๋ผ๋ฉด ์ž์‹ ์—๊ฒŒ ์˜จ packet์ด ์•„๋‹ˆ๋ฏ€๋กœ ๋ฒ„๋ฆฐ๋‹ค

      • ์ด ์—ญํ• ์€ LAN Card๊ฐ€ ๋‹ด๋‹นํ•œ๋‹ค

    • 2๊ณ„์ธต์— ์ ํžŒ ์ •๋ณด์˜ ๋ชฉ์ ์ง€๊ฐ€ ์ž์‹ ์ด ๋งž๋‹ค๋ฉด, 3๊ณ„์ธต์œผ๋กœ ์ •๋ณด๋ฅผ ๋ณด๋‚ด์ค€๋‹ค

      • data๋ฅผ ์ƒ์œ„ ๊ณ„์ธต์œผ๋กœ ์˜ฌ๋ ค๋ณด๋‚ผ ๋•Œ 2๊ณ„์ธต์˜ header ์ •๋ณด๋Š” ๋” ์ด์ƒ ํ•„์š”์—†์œผ๋ฏ€๋กœ ๋ฒ—๊ฒจ๋‚ด๊ณ  ์˜ฌ๋ ค๋ณด๋‚ธ๋‹ค

      • 3๊ณ„์ธต๊ณผ 4๊ณ„์ธต์—์„œ๋„ ๋˜‘๊ฐ™์ด ๊ฐ ๊ณ„์ธต์˜ ์ •๋ณด๋ฅผ ํ™•์ธํ•˜๊ณ , ์ž์‹ ์—๊ฒŒ ์˜จ ๊ฒƒ์ด ๋งž๋Š”์ง€ ํ™•์ธ ํ›„ ๋งž์œผ๋ฉด ์ƒ์œ„ ๊ณ„์ธต์œผ๋กœ ์˜ฌ๋ ค๋ณด๋‚ธ๋‹ค

์ด๋Ÿฌํ•œ ์ž‘์—…์€ ์•„๋ž˜์˜ 2๊ฐ€์ง€ ์ •๋ณด ํ๋ฆ„์œผ๋กœ ์„ค๋ช…ํ•  ์ˆ˜ ์žˆ๋‹ค

  1. Encapsulation, Decapsulation ๊ณผ์ •์„ ํ†ตํ•ด data๊ฐ€ ์ „์†ก๋˜๋Š” ๊ณผ์ •

  2. ๊ฐ ๊ณ„์ธต header๋ฅผ ์ด์šฉํ•ด ์†ก์‹ ์ž ๊ณ„์ธต๊ณผ ์ˆ˜์‹ ์ž ๊ณ„์ธต ๊ฐ„์˜ ๋…ผ๋ฆฌ์  ํ†ต์‹  ๊ณผ์ •

  • ์‹ค์ œ๋กœ data๋Š” ์ƒ์œ„ ๊ณ„์ธต(Upper Layer)์—์„œ ํ•˜์œ„ ๊ณ„์ธต(Lower Layer)๋กœ ์ƒ์œ„ ๊ณ„์ธต์—์„œ packet ํ˜•ํƒœ๋กœ ํ•˜๋‚˜์”ฉ encapsulation๋˜๋ฉด์„œ ๋‚ด๋ ค์˜ค๊ณ , 2๊ณ„์ธต์˜ LAN card์—์„œ ์ „๊ธฐ ํ˜•ํƒœ๋กœ ๋ณ€ํ™˜๋˜์–ด ๋ชฉ์ ์ง€๋กœ ์ „๋‹ฌ๋œ๋‹ค

  • ํ•ด๋‹น ์ „๊ธฐ ์‹ ํ˜ธ๋ฅผ ๋ฐ›์€ ๋ชฉ์ ์ง€์—์„œ๋Š” data ํ˜•ํƒœ๋กœ ๋ณ€ํ™˜ํ•ด ์ƒ์œ„ ๊ณ„์ธต์œผ๋กœ ์˜ฌ๋ ค์ฃผ๊ณ , packet๋“ค์„ ์กฐํ•ฉํ•ด data ํ˜•ํƒœ๋กœ ๋งŒ๋“ค๊ฒŒ ๋œ๋‹ค

  • ์ฆ‰, ์‹ค์ œ data๋Š” ์ƒ์œ„ ๊ณ„์ธต์—์„œ ํ•˜์œ„ ๊ณ„์ธต, ํ•˜์œ„ ๊ณ„์ธต์—์„œ ์ƒ์œ„ ๊ณ„์ธต์œผ๋กœ ์ „๋‹ฌ๋˜๊ณ  header ์ •๋ณด๋Š” ๊ฐ ๊ณ„์ธต๋ผ๋ฆฌ ์ „๋‹ฌ๋œ๋‹ค

Data๋ฅผ encapsulationํ•˜๋Š” ๊ณผ์ •์—์„œ header์— ๋„ฃ๋Š” ์ •๋ณด๋Š” ๋‹ค์–‘ํ•œ๋ฐ, ์ด๋Ÿฐ ๋ณต์žกํ•œ ์ •๋ณด๋“ค์—์„œ๋„ ๊ทœ์น™์ด ์žˆ์œผ๋ฉฐ ์•„๋ž˜์˜ ๋‘ ๊ฐ€์ง€ ์ •๋ณด๋Š” ๋ฐ˜๋“œ์‹œ ํฌํ•จ๋˜์–ด์•ผ ํ•œ๋‹ค

  1. ํ˜„์žฌ ๊ณ„์ธต์—์„œ ์ •์˜ํ•˜๋Š” ์ •๋ณด

  2. ์ƒ์œ„ protocol ์ง€์‹œ์ž

1. ํ˜„์žฌ ๊ณ„์ธต์—์„œ ์ •์˜ํ•˜๋Š” ์ •๋ณด

  • OSI 7๊ณ„์ธต์˜ ๊ฐ ๊ณ„์ธต์—์„œ์˜ ๋ชฉ์ ์— ๋งž๋Š” ์ •๋ณด๋“ค์ด ํฌํ•จ๋œ๋‹ค

  • 4๊ณ„์ธต์˜ ๋ชฉ์ ์€ ํฐ data๋ฅผ ์ž˜ ๋ถ„ํ• ํ•˜๊ณ  ๋ฐ›๋Š” ์ชฝ์—์„œ๋Š” ์ž˜ ์กฐ๋ฆฝํ•˜๋Š” ๊ฒƒ์ด๊ธฐ ๋•Œ๋ฌธ์— data์— ์ˆœ์„œ๋ฅผ ์ •ํ•˜๊ณ  ๋ฐ›์€ packet์˜ ์ˆœ์„œ๊ฐ€ ๋งž๋Š”์ง€ ์ ๊ฒ€ํ•˜๋Š” ์—ญํ• ์ด ์ค‘์š”ํ•˜๋ฉฐ ์ด ์ •๋ณด๋ฅผ header์— ์ ์–ด ๋„ฃ๊ฒŒ ๋œ๋‹ค

    • TCP/IP์˜ 4๊ณ„์ธต protocol์ธ TCP์—์„œ๋Š” Sequence number, ACK number field๋กœ ์ด data๋ฅผ ํ‘œํ˜„ํ•œ๋‹ค

  • 3๊ณ„์ธต hearder์—๋Š” 3๊ณ„์ธต์—์„œ ์ •์˜ํ•˜๋Š” ๋…ผ๋ฆฌ์  ์ฃผ์†Œ์ธ ์ถœ๋ฐœ์ง€, ๋„์ฐฉ์ง€ IP ์ฃผ์†Œ๋ฅผ header์— ์ ์–ด๋„ฃ๋Š”๋‹ค

  • 2๊ณ„์ธต์€ MAC ์ฃผ์†Œ๋ฅผ ์ •์˜ํ•˜๋Š”๋ฐ, 3๊ณ„์ธต์ฒ˜๋Ÿผ 2๊ณ„์ธต๋„ ์ถœ๋ฐœ์ง€, ๋„์ฐฉ์ง€ MAC ์ฃผ์†Œ๋ฅผ header์— ๋„ฃ๋Š”๋‹ค

2. ์ƒ์œ„ protocol ์ง€์‹œ์ž

  • protocol stack์€ ์ƒ์œ„ ๊ณ„์ธต์œผ๋กœ ์˜ฌ๋ผ๊ฐˆ์ˆ˜๋ก ์ข…๋ฅ˜๊ฐ€ ๋งŽ์•„์ง„๋‹ค

    • 3๊ฒŒ์ธต protocol์ธ IP๋Š” 4๊ณ„์ธต์—์„œ๋Š” TCP์™€ UDP๋กœ ๋‚˜๋‰˜๊ณ , ๊ทธ๋ณด๋‹ค ๋” ์ƒ์œ„ ๊ณ„์ธต์—์„œ๋Š” FTP, HTTP, SMTP, POP3๋“ฑ ๋” ๋‹ค์–‘ํ•œ prtocol๋กœ ๋‹ค์‹œ ๋‚˜๋‰œ๋‹ค

  • Encapsulation ๊ณผ์ •์—์„œ๋Š” ์ƒ์œ„ Protocol์ด ๋งŽ์•„๋„ ๋ฌธ์ œ๊ฐ€ ์—†์ง€๋งŒ, decapsulation ํ•˜๋Š” ๋ชฉ์ ์ง€ ์ชฝ์—์„œ๋Š” header์— ์•„๋ฌด ์ •๋ณด๊ฐ€ ์—†์œผ๋ฉด ์–ด๋–ค ์ƒ์œ„ protocol๋กœ ์˜ฌ๋ ค๋ณด๋‚ด ์ฃผ์–ด์•ผ ํ• ์ง€ ๊ฒฐ์ •ํ•  ์ˆ˜ ์—†๋‹ค

    • ex) 3๊ณ„์ธต์—์„œ ๋ชฉ์ ์ง€ IP์ฃผ์†Œ๋ฅผ ํ™•์ธํ•˜๊ณ  4๊ณ„์ธต์œผ๋กœ data๋ฅผ ์˜ฌ๋ ค๋ณด๋‚ผ ๋•Œ header์— ์ƒ์œ„ protocol ์ •๋ณด๊ฐ€ ์—†๋‹ค๋ฉด TCP๋กœ ๋ณด๋‚ด์•ผ ํ• ์ง€ UDP๋กœ ๋ณด๋‚ด์•ผ ํ• ์ง€ ๊ตฌ๋ถ„ํ•  ์ˆ˜ ์—†๋‹ค

  • ์ด๋Ÿฌํ•œ ๋ฌธ์ œ๊ฐ€ ๋ฐœ์ƒํ•˜์ง€ ์•Š๋„๋ก Encapsulationํ•˜๋Š” ์ชฝ์—์„œ๋Š” header์— ์ƒ์œ„ protocol ์ง€์‹œ์ž ์ •๋ณด๋ฅผ ํฌํ•จํ•ด์•ผ ํ•œ๋‹ค

์ƒ์œ„ ํ”„๋กœํ† ์ฝœ ์ง€์‹œ์ž

  • ๊ฐ ๊ณ„์ธต๋งˆ๋‹ค ์ƒ์œ„ protocol ์ง€์‹œ์ž๋ฅผ ๊ฐ€์ง€๊ณ  ์žˆ์ง€๋งŒ ๊ณ„์ธต๋งˆ๋‹ค ์ด๋ฆ„์ด ๋‹ค๋ฅด๋‹ค

    • 4๊ณ„์ธต์€ port ๋ฒˆํ˜ธ

    • 3๊ณ„์ธต์€ protocol ๋ฒˆํ˜ธ

    • 2๊ณ„์ธต์€ Either type์ด๋ผ๊ณ  ๋ถ€๋ฅธ๋‹ค

  • ์—ฌ๊ธฐ์„œ ์ฃผ์˜ํ•ด์•ผ ํ•  ์ ์€ port ๋ฒˆํ˜ธ๋Š” 4๊ณ„์ธต header์— ์ ํžŒ ์ •๋ณด์ด์ง€๋งŒ application layer์—์„œ protocol ์ข…๋ฅ˜๋ผ๋Š” ๊ฒƒ์ด๋‹ค

    • ์ฆ‰, decapsulation ํ•  ๋•Œ ์ƒ์œ„ protocol ์ •๋ณด๋ฅผ ์ด์šฉํ•ด ์–ด๋А ์ƒ์œ„ protocol๋กœ ๋ณด๋‚ด์•ผ ํ• ์ง€ ๊ตฌ๋ถ„ํ•ด์•ผ ํ•˜๋ฏ€๋กœ ๋™์ž‘ํ•˜๋Š” ๊ณ„์ธต๋ณด๋‹ค ํ•œ ๊ณ„์ธต ์œ„์˜ ์ •๋ณด๊ฐ€ ์ ํ˜€์žˆ๊ฒŒ ๋œ๋‹ค

port ๋ฒˆํ˜ธ - 4๊ณ„์ธต

Port ๋ฒˆํ˜ธ
Service

TCP 20, 21

FTP (File Transfer Protocol)

TCP 22

SSH (Secure Shell)

TCP 23

TELNET (Telnet Terminal)

TCP 25

SMTP (Simple Mail Transport Protocol)

UDP 49

TACACS

TCP 53 / UDP 53

DNS (Domain Name Service)

UDP 67, 68

BOOTP (Bootstrap Protocol)

TCP 80 / UDP 80

HTTP (HyperText Transfer Protocol)

UDP 123

NTP (Network Time Protocol)

UDP 161, 162

SNMP (Simple Network Management Protocol)

TCP 443

HTTPS

TCP 445 / UDP 445

Microsoft-DS

protocol ๋ฒˆํ˜ธ - 3๊ณ„์ธต

Protocol ๋ฒˆํ˜ธ
Protocol

1

ICMP (Internet Control Message)

2

IGMP (Internet Group Management)

6

TCP (Transmission Control)

17

UDP (User Datagram)

50

ESP (Encap Security Payload)

51

AH (Authentication Header)

58

IPv6์šฉ ICMP

133

FC (Fibre Channel)

Ether Type

Ether Type
Protocol

0x0800

IPv4 (Internet Protocol version 4)

0x0806

ARP (Address Resolution Protocol)

0x22F3

IETF TRILL Protocol

0x8035

RARP (Reserve ARP)

0x8100

VLAN-tagged frame (802.1Q)

Shortest Path Bridging (802.1aq)

AH (Authentication Header)

0x86DD

IPv6 (Internet Protocol version 6)

0x88CC

LLDP (Link Layer Discovery Protocol)

0x8906

FCoE (Fibre Channel over Ethernet)

0x8915

RoCE (RDMA over Coverged Ethernet)

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