The Internet

Purpose of ISP (Internet Service Provider)

Supplies a device to that provides a connection from your home to the service provider

Edge routers

Link networks together

Subscriber router

A type of router provided to homes and small businesses, containing two interfaces and are simpler

Enterprise router

Connects large businesses and ISP networks to the internet

Core Router

Routers that are part of the backbone of the internet, having the highest speed and multiple interfaces

Packet

Data being transported (the payload), aswell as a header

Packet switching

The process of moving packets around the internet, invoolvinng sending packets from end-to-end

What does the router do?

The router examines the destination address of a packet and decides which interface it should use to get to it.

Routing table

The set of rules a router uses to decide what to do with an incoming packet

When do routers become slow?

When routers recieve packets faster than they are able to route them, causing the memory to buffer them and cause delays

Circuit switching

A dedicated connection is formed between two points and the connection remains active for the duration of the transmission

Domain name

User-friendly names that replace the IP address of a webpage on the internet

DNS (Domain Name System)

Retrieves the IP address associated with a domain name, is hierarchal with a root (.) on the top

DNS lookup

Used to get a new copy of a web page

How does entering a URL work?

1. The browser sends the hostname part to the DNS

2. DNS checks the hostname in the lookup table

3. DNS respondes with the IP address to the browser

4. Browsers sends a reqests for the resources from the IP address

5. Resources are returned to browser

Recursive name server

Performs full DNS resolution requests

Protocol stack

A set of protocols used to format the data, transform it into bits, then transmit and do the same in reverse

Application layer

Where data is sent from software into the protocol stack, eg HTTP, adding a relevent header to the data

Transport layer

Breaks the application data into packets, adding destination port numbers to the header, then transported using TCP or UDP

Internet layer

Prepares the data for the intenet, addinng the source and destination addresses to the header and using packet switching to send the packet to the desired destination

Link layer

Transports IP packets across each of the individual links made from the communicationg computers,

What happened to OSI?

The seven layer model had it's layers merged into the TCP/IP stack

Encapsulation (internet)

Modular commnication, adding information to the header of a packet to send data from one computer to another