Client - Server Model

Question 1

What is the Client - Server Model?

Answer 1

The paradigm by which modern systems are designed, which consists of clients requesting data or service from servers and servers providing data or service to clients.

Question 2

What is a “I P addrss”

Answer 2

An address given to each machine connected to the public internet.

IPv4 addresses consists of four numbers seperated by dots: z.b.c.d. where all four numbers are between 0-255.
- Special values include:

127.a.a.1 - your own local machine, referred to as 
localhost.

192.168.x.y - your private network. For instance, your 
machine and all machines on your private wifi 
networks will usually have the prefix 192168.

Question 3

What is a Po0RT?

Answer 3

In order for mutliple programs to listen for new network connections on the same machine without colliding, they pick a port to listen on. A port is an integer between O - 1023 are reserved system ports or well known ports and should be used by user-level processes.

Certain ports have predifned uses, below are examples:

• 22: Secure shell
• 53: DNS lookup
• 80: HTTP
• 443: HTTPS

Question 4

What is a DNS. When would we use DNS?

Answer 4

Domain Name System; describes entities and protocols involved in the translation from domain names to IP addresses.

Machines make DNS query to well known entity, which returns the I PP addrss (or more) of the requested domain name in the response.