Network seminar.key

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1 Intro to Network

2 ( ) ( ).

3 ?!? ~! This is ~ ( )

4 /,,,????

5 TCP/IP Application Layer Transfer Layer Internet Layer Data Link Layer Physical Layer OSI 7

6 TCP/IP Application Layer Transfer Layer 3 4 Network Layer Layer! ( CS ) Data Link Layer Physical Layer

7 Application Layer Transfer Layer Internet Layer Application HTTP FTP / SMTP, IMAP, POP DNS Shell SSH Data Link Layer Physical Layer

8 Application Layer Transfer Layer TCP/UDP TCP initialization UDP / Internet Layer TCP UDP 16, 0~65535 Data Link Layer Physical Layer

9 Application Layer Transfer Layer IPv4, IPv6 IP(+ ) Internet Layer Data Link Layer Physical Layer

10 Application Layer Transfer Layer Ethernet MAC Internet Layer Data Link Layer Physical Layer

11 Application Layer Transfer Layer Internet Layer Data Link Layer Physical Layer

12 Application Layer Application Layer Transfer Layer Transfer Layer Network Layer Network Layer Data Link Layer Data Link Layer Physical Layer Physical Layer

13 .... HUB. 3...

14 IP, hierarchy ( ) IPv4: IP IPv6: IP IPv6 IPv6 2% MAC, hierarchy ( )

15 IPv4 A class: 0~ x.x.x 2 24 (MIT, ) B class: 128~ x.x 2 16 (KAIST) C class: 192~ x 2 8 D class: 224~239 E class: 240~255 Multicast CIDR (Classless Inter-Domain Routing)

16 (Router) (port) Forwarding table 3 Network Layer IP

17 (Switch) MAC, forwarding L2, L3, L4 ex. L2 Data Link Layer ex. L3 Internet Layer

18 ~

19 IP = = x IP! Q ?

20 Public IP vs. Private IP IP, ICANN IPv = 42 Private IP IP, (ex. 10.x.x.x, x.x) A B (Public IP CDN IP ) IP 10.x.x.x x.x!?

21 NAT IP Public IP (+port) Private IP (+port) Public IP : :2001 Private IP : :5000.,. IP.

22 google.com DHCP, DNS, ARP, TCP, HTTP

24 5 Layers 5!? - IP - IP, MAC IP - DNS IP - IP MAC

25 DHCP: IP IP! DHCP! DHCP: IP Protocol OS DHCP Broadcast Broadcast? (dst IP )

26 DHCP: IP DHCP UDP! UDP dst port 67 src port 68 (DHCP ) IP dst IP: (Broadcast) src IP: ( ) dst MAC : FF:FF:FF:FF:FF:FF (Broadcast) src MAC : NIC MAC

27 DHCP: IP DHCP DHCP ACK. IP, DNS IP, IP,, UDP, IP, MAC., src MAC DHCP ( ), dst MAC.

28 DNS: google.com IP? : IP, DNS IP, IP, domain name! IP DNS: IP DNS IP DHCP, IP Request!

29 ARP: IP? DNS,, IP IP! IP DNS.... dst MAC MAC..

30 ARP: IP? ARP: IP MAC protocol broadcast IP ~. ARP dst MAC FF:FF:FF:FF:FF:FF IP. (link layer) ARP IP ARP.! MAC ARP, ARP MAC src MAC ARP.!

31 ! ARP ARP link layer protocol LAN. arp -a : ARP arp -d [IP] : ARP entry arp -s [IP] [MAC] : ARP entry arp table /proc/net/arp

32 DNS: google.com IP? (RIP, OSPF ) DNS IP, DNS DNS DNS DB google IP DNS.

33 TCP Handshake: Google IP HTTP! IP subnet! ->! IP, MAC. HTTP GET TCP. TCP 3 way handshaking.

34 TCP Handshake: Google SYN - SYNACK - ACK, TCP!!

35 HTTP Request:! GET Request! Response-> index.html component component (TCP persistent connection -> )

36 HTTPS & TLS Handshaking:! HTTP encryption.!. TLS (Transport Layer Security): transport HTTPS TLS (SSL) HTTP! *DNS DNSSEC

37 Try It Yourself!

38 network.., /etc/resolv.conf /etc/network/interfaces.

39 ..

40 IPv4. - (M) : DHCP( IP ) / ( IP). - : IP. - DNS : DNS. (,).

43 - ifconfig ifconfig : CLI. ifconfig ifconfig eth0 [IP] netmask [subnet] broadcast [IP] route add default gw [IP] dev eth0 DNS vi /etc/resolv.conf nameserver ifconfig eth0 down ifconfig eth0 up ping

44 - ifconfig

45 - ifconfig

46 Try It Yourself! VPN

47 VPN VPN /

48 VPN IP. IP.

49 VPN ID pptpd password.

50 VPN. VPN.

51 VPN.

52 VPN PPTP.

53 VPN PMTU.

TCP.IP.ppt

TCP.IP.ppt TCP/IP TCP/IP TCP/IP TCP/IP TCP/IP Internet Protocol _ IP Address Internet Protocol _ Subnet Mask Internet Protocol _ ARP(Address Resolution Protocol) Internet Protocol _ RARP(Reverse Address Resolution