Internet Protocols: Fundamentals, Data Transmission, Addressing, and Application Protocols

Protocol

An agreed-upon set of rules that specifies the proper formatting of data, communication procedures, and handling of information between any two networked components.

Open Protocols

Communication protocols that are standardized and nonproprietary, which allows users to easily connect additional computing devices to the internet.

Abstraction (Protocols)

Allows for a clear set of standards for how information should be exchanged to be explicitly described, while avoiding the complexity and minutiae of how a manufacturer implements that standard in their hardware or software.

Protocol Design Goals

Any agreed-upon standard needs to: 1) Enable the reliable and efficient transmission of data at large and small scales, 2) Provide an unambiguous set of protocols, and 3) Be flexible enough to adapt to and accommodate future technological innovations.

Hierarchy

Along with redundancy (provided by protocols), hierarchy helps systems, like the internet, scale to solve larger problems.

Packet Switching

The underlying method of transferring data between nodes (proposed by Vint Cerf and Bob Kahn in 1974). All data is subdivided into small, fixed-size blocks (packets) that are transmitted independently from one another, potentially taking different routes to the destination.

Routing

The process of finding a path from sender to receiver. Routing on the internet is usually dynamic (not specified in advance).

Packet

A suitably sized block of data containing a Header and a Payload. Packets may arrive at the destination in order, out of order, or not at all.

Packet Header

Contains metadata such as the Source IP Address and the Destination IP Address, and any other information needed to deliver the packet.

Packet Payload

The actual data that is being sent.

TCP (Transmission Control Protocol)

Does an inventory at the destination to ensure all packets have arrived and puts them in the correct order to reconstruct the data. If packets are missing or corrupt, TCP requests the sender to send the data again (enhancing reliability).

UDP (User Datagram Protocol)

An internet data transmission protocol often used when speed is prioritized over the guaranteed delivery offered by TCP.

IP Address

A unique numerical identifier assigned to each node, allowing other nodes to know which nodes they are directly connected to and determine a route. IANA oversees distribution of these addresses.

IPv4

Uses 32-bit addresses (four octets separated by periods). Capacity is limited to 4.3 billion unique addresses, which is finite and has been exhausted in some regional registries (like APNIC in 2011 and ARIN in 2015).

IPv6

Uses 128-bit addresses (four times the length of IPv4). This new standard is capable of sustaining more than $3.4 \times 10^{38}$ individual nodes, effectively solving the issue of address capacity.

DNS (Domain Name System)

A massive lookup table that acts like a large directory or phone book, associating a Domain Name (human-friendly) with its associated IP Address (machine-friendly) for routing.

DNS Hierarchy

The domain name syntax is hierarchical (an arrangement of elements in a ranking of inclusiveness or superiority). The structure starts with the root and divides into familiar domains (.com, .org, etc.) and subdomains, enabling scalability.

DNS Security

DNS is typically not as well secured as many other services because the information it contains (hostnames and IP addresses) is publicly available.

HTTP/HTTPS

Protocols for webpages. HTTP transfers web content. HTTPS is the secure, encrypted version.

SMTP

Protocol used for e-mail transfer.

FTP

Protocol used for file transfer.