This step is more specific and technical base, compared to previous step. You need to know at least the basic information about network like network protocol and how it works.

How E-mail works with network 7 layers.
[John sends E-mail to Sarah]
1.[Application Layer] Using internet browser to send email like Chrome, firefox
2.[Presentation Layer] POP/SMTP
3.[Session Layer] POP/26
4.[Transport Layer]

ㅁTCP(Transmission Control Protocol) : it provides connecting service over IP protocol, easily found when we use internet.

Alive or Dead?
ㅁPing Sweep

Open or Closed?