OSI model

• Simple Mail Transfer Protocol(SMTP)

  • SMTP: 우체국, POP3, ICMP: 집배원

  OTP, 인증번호 관리

  https://nodemailer.com/

  https://github.com/marcomelilli/nestjs-email-authentication/tree/master

• How to calculate network address and broadcast address

  • subnet mask: 11111111.11111111.11111111.11100000 (255.255.255.224)
  • IP: 11011000.11001011.01000000.01011011 (216.203.64.91)
  • Network address: 11011000.11001011.01000000.01000000 (216.203.64.64) → AND operation of subnet mask and IP
  • Broadcast address: 11011000.11001011.01000000.01011111 (216.203.64.95)

• TCP vs UDP

  	Connection	Flow Control(speed)	Congestion Control(amount)
  TCP	yes	yes	yes
  UDP	no	no	no

• IP

  • Computer or smart phone’s unique address for connecting internet.
  • Public IP
    • A: xxx.yyy.yyy.yyy (x is denoted fix)
    • B: xxx.xxx.yyy.yyy
    • C: xxx.xxx.xxx.yyy
  • Private IP
    • A: 10.0.0.0 ~ 10.255.255.255
    • B: 172.16.0.0 ~ 172.31.255.255
    • C: 192.168.0.0 ~ 192.168.255.255
  • Network Address Translation(NAT)
    • Inter-communication between public IP and private IP