system-design-refresher

Networking

For a more in-depth version you can see ccna-notes

Contents

• IP Addresses
• Internet Protocol
• Transport Layer

IP Address

A unique identifier for each device in a network.

• IPv4 addresses are 32bit
• IPv6 addresses are 128bit significally increasing the number of available IP addresses

Internet Protocol

Set of rules that define how data is sent and received

Application Layer

In this layer data specific to application protocol is stored.

Transport Layer

TCP

Transmission Control Protocol ensures complete and correct delivery of data packets. It implements a process known as 3-way handshake.

UDP

User Datagram Protocol is faster but less reliable than TCP. It doesn’t stablish a connection before sending data and doesn’t guarantee the delivery or order of the packages. Usually used for time-sensitive communications like video-calls or live-streaming where speed is crucial and some data loss is acceptable.

DNS

Domain Name System translates human-friendly domain names into IP addresses, allowing users to stablish a connection to the server and retrieve the web resource.

• A Record: Maps the domain to the corresponding IPv4 Address
• AAAA Record: Maps the domain to the corresponding IPv6 Address

ICANN

Coordinates the global IP address space and DNS. Domain name registrars are accredited by ICANN to sell domain names to the public.

Network Infrastructure

Devices connected in a LAN (Local Area Network) can communicate with each other directly.

Public vs Private IP Address

• Public IP Address: unique across the internet
• Private IP Address: unique within the local network

Firewalls

We use firewalls to protect a network which monitors and controls incoming and outgoing network traffic.

Ports

Within a device specific processes are identified by ports. Some ports are reserved for specific protocols:

• HTTP: 80
• HTTPS: 443
• SSH: 22