課題

<勉強オーダー：Cloudを勉強する前に知っておくべき知識>

[N Tier]
⇒なぜN Tier構成を行うのか説明出来る。

1. To be more secure. As you separate them, you could build more secure layer which is essential for application and database comparing to presentation(usually located as very first tier)
2. Efficient for development(easy to separate roles), testing(easy to test separately), deployment, maintenance

Overall, more layers(tiers) means you can have more control on them. 

⇒今見ているプロジェクトが何N Tierなのか言える。

3 tier architecture
Client tier -> web/app tier -> database tier

参考：https://www.youtube.com/watch?v=gdEZBNUccq8

In addition, 

Why not 2-tier?
Less secure, hard to scale, harder to maintain

4-tier architecture
Client tier -> web-tier(web-server) -> Business logic tier(app-server) -> database tier

[TCP/ IP]
・キーワード
　⇒ IP v4
　⇒ Subnet(Mask)
　⇒ Private network
　⇒Router

I wrote some notes about these key words. 

⇒自分のパソコンのPublic IP・Private IPが何か確認出来る
You can check your Public IP simply by typing 'what is my ip address?' on browser.
For Private IP, you can check it through the terminal on your device. 

⇒Subnetを分ける意味を説明出来る
To divide the broadcast area (network).
If you have a large number of hosts on a network, you won't be able to communicate smoothly. To solve this problem, you need to distribute the network properly. It also helps to save IP addresses by properly separating the networks.

⇒SubnetにおけるGatewayの役割が何か説明出来る
Written in notes above.