Client-Server Model

The Client-Server Model §

The client-server model is the dominant paradigm for the modern internet.

Clients §

• A machine or process that sends data to, or requests data from, a server. Typically this is a personal computer, browser, phone or app, but it can also be another server.

Servers §

• A machine or process that provides data or some kind of service to clients, typically by listening for network calls. A server can also be a client for another server.

DNS Queries §

• A client will ask a pre-determined set of servers: what’s the IP address of some other server?
• An IP address is a unique identifier for a specific server
• These IPs are assigned by some kind of authority - Amazon/Google Cloud

Requests §

• A source IP address sends a series of bytes as packets
• The server uses this source IP adddress to return another series of packets

Ports §

• If an IP address is similar to a mailing address, a port is equivalent to the flat number
• Machines have 16k (14 bits?) ports
• You can attempt to communicate with any of them, but typically the port you have to request is dictacted by the protocol
  • http uses port 80
  • https uses port 443