Internet Service Concepts and TCP/IP

Internet Service Concepts

The Internet, often called "the Net," is a global network of computer networks enabling users to access information from any computer with permission.
Initiated by the Advanced Research Projects Agency (ARPA) of the U.S. government in 1969, it was initially known as ARPANET.
The original purpose was to enable communication between research computers at different universities.
A key design benefit was its ability to function even if parts were destroyed due to multiple routing directions.
Today, the Internet is a public, cooperative, self-sustaining facility for hundreds of millions worldwide and has fueled social media and e-commerce growth.
E-commerce, or online shopping, has emerged as a major application of the Internet.
The Internet utilizes public telecommunication networks, distinguished by its use of Transmission Control Protocol/Internet Protocol (TCP/IP).
Intranets and extranets are recent adaptations using TCP/IP.
The Internet comprises network protocols and hardware.
Protocols like TCP/IP are sets of rules for device communication; without these rules, communication would be impossible.
Protocols translate text into electronic signals for transmission and back again.
Hardware includes computers, smartphones, cables, satellites, radios, cell towers, routers, and servers.

Communication across distances, information sharing, and access to information are general uses.
Specific uses include:
- Social media and content sharing
- E-mail, IRC, Internet telephony, instant messaging, and video conferencing
- Education via online programs, courses, and workshops
- Job searching for both employers and applicants, including social networking sites like LinkedIn

Developed by ARPA in 1969 named ARPANet.
The primary aim was to connect university research labs.
A secondary goal was to secure messages through rerouting in case of attacks or disasters.

Computers connected to the internet are part of a worldwide network, and each device has a unique address.
Internet addresses are in the format "kkk.kkk.kkk.kkk" where each "kkk" ranges from 0-256. This is an IP address (Internet Protocol).

An IP address is a unique address for each machine/device connected to the internet.
Addresses are in the form "kkk.kkk.kkk.kkk", where each "kkk" ranges from 0 to 256.
If a client connects through an Internet Service Provider (ISP), a temporary IP address is assigned for the session.
If a client connects through a Local Area Network (LAN), a permanent IP address is likely assigned.
The "Ping" program verifies internet connection on systems (available on Microsoft Windows and Unix OS).

Protocol stacks enable communication between devices on the internet by converting messages into electronic signals and vice versa.
The TCP/IP protocol stack is primarily used for internet communication.
Example:
- Sending the message “Hello Friend” from a computer with IP address 173.196.95.98 to another with IP address 162.194.60.98.
- The message is encrypted into a digital form for transmission and decrypted back to the original form upon arrival.

The message starts at the application layer and moves down the protocol stack.
Large messages are broken into smaller chunks called Packets for stable data management.
At the TCP/IP layer, the data packet is assigned a port number to identify the sending application.
The IP layer provides the destination IP address for message delivery.
The hardware layer converts the alphanumeric message into a digital signal for transmission.
ISPs examine the recipient’s address and forward the packets through routers.
Packets are reassembled into the original message at the destination computer after moving upwards through the stack, where unnecessary data (IP address, port number) is removed.

Describes how computers at different locations interact, how messages are sent, and how packets are transmitted and received.
The ISP manages a pool of modems, handled by a device that contains data flow from the modem pool to a spine or specific line router, which can be linked to a port server for network connectivity and billing information.
Packets pass through the phone framework and ISP equipment, then are redirected to the ISP’s mainline or infrastructure, which purchases bandwidth.
From there, packets traverse many routers, backbones, unique lines, and other networks to reach the target device.
The traceroute program (available on Microsoft Windows and Unix) traces the path of packets, printing all routers, computer systems, and other internet entities the packet travels through.
Internet routers decide the further communication of packets.

TCP/IP stands for Transmission Control Protocol/Internet Protocol; it's a suite of communication protocols used to interconnect network devices on the internet.
TCP/IP is also used as a communications protocol in private computer networks (intranets or extranets).
TCP/IP specifies how data is exchanged over the internet, including how it should be broken into packets, addressed, transmitted, routed, and received at the destination.
TCP/IP requires little central management and is designed to make networks reliable with the ability to recover automatically from device failures.
TCP defines how applications create communication channels across a network and manages how a message is assembled into smaller packets before transmission and reassembled at the destination.
IP defines how to address and route each packet to ensure it reaches the right destination, with each gateway computer checking the IP address to forward the message.

Hypertext Transfer Protocol (HTTP): handles communication between a web server and a web browser.
HTTP Secure: handles secure communication between a web server and a web browser.
File Transfer Protocol: handles the transmission of files between computers.

TCP/IP uses the client-server model, where a client is provided a service by a server in the network.
The TCP/IP suite of protocols is classified as stateless, meaning each client request is considered new and unrelated to previous requests, freeing up network paths.
The transport layer is stateful, transmitting a single message and maintaining the connection until all packets are received and reassembled.
The TCP/IP model differs slightly from the seven-layer Open Systems Interconnection (OSI) networking model.

TCP/IP is nonproprietary and not controlled by any single company, allowing for easy modification.
It is compatible with all operating systems (OSes), computer hardware, and networks.
TCP/IP is highly scalable and can determine the most efficient path through the network.

Is complicated to set up and manage.
The transport layer does not guarantee the delivery of packets.
It is not easy to replace protocols in TCP/IP.
Does not clearly separate the concepts of services, interfaces, and protocols, so it is unsuitable for describing new technologies in new networks.
Is especially vulnerable to a synchronization attack, a type of denial-of-service attack. a bad actor uses TCP/IP.