5: Network Protocols

Peer-to-peer network

A small environment, often in homes or microbusinesses, where devices act as both providers and consumers of services without dedicated central servers.

Small home network

A setup that links a few personal devices together and to the public internet for basic sharing and access.

SOHO network

A configuration that lets remote or home offices reach corporate resources and shared services over a secure connection.

Medium to large network

An enterprise-scale deployment, such as in corporations or schools, that spans many locations and supports hundreds or thousands of hosts.

World wide network

The global “network of networks” interconnecting hundreds of millions of systems, commonly referred to as the internet.

Host

Any endpoint on a communication system that participates directly in data exchange, also called an end device, node, or endpoint.

Server

A system running specialized software that answers requests for resources such as web pages, files, or email from other endpoints.

Client

A system running applications like browsers, mail programs, or file tools that send requests and display responses from remote providers.

File server

A central system that stores user and corporate documents, accessed through file-browsing software on connected machines.

Web server

A system running HTTP software that responds to browser requests by delivering pages and media content.

Email server

A system running mail software that stores and forwards messages to users’ mail applications.

Typical session (school)

An interaction where a student’s search query travels via wireless and wired infrastructure and ISP links to reach a search service and return results.

Typical session (gaming)

An interaction where a console sends player actions over residential access links and provider networks to a game host, which returns graphics and audio updates.

Typical session (medical cloud)

An interaction where digitized clinical images and patient data are encrypted, addressed, and sent over the internet to centralized storage and retrieval services.

Internet Exchange Point (IXP)

Global Tier 1 and Tier 2 ISPs connect portions of the internet together, usually through an

Tier 3 ISP

connect homes and businesses to the internet.

Point of Presence (PoP)

A location, typically inside a building, where physical and logical connections are made between a provider’s infrastructure and customer networks.

Protocol (general)

A defined set of rules that governs how communication participants format, send, receive, and interpret messages.

Network protocol feature set

The group of behaviors a communication standard defines, including encoding, structure, size, timing, and delivery options.

HTTP

A set of rules for exchanging text, images, audio, video, and other web content over the World Wide Web.

TCP

A transport mechanism that provides reliable, ordered delivery of data between processes on different hosts, confirming successful receipt.

IP (family)

A set of mechanisms responsible for addressing and forwarding packets so they can travel from a source to a destination across one or more interconnected systems.

Message structure

The defined layout and fields that determine how a communication unit is arranged for correct processing.

Path sharing

The process by which forwarding devices exchange reachability information about networks and routes.

Information sharing

The exchange of error notifications and system messages that allow participants to respond to problems and status changes.

Session management

The setup, maintenance, and teardown of logical exchanges so that application data flows can start and end cleanly.

TCP/IP protocol suite

The open, standards-based family of protocols used for most modern networks and the public internet.

Open standard suite

A collection of communication rules that is publicly available so any vendor can implement it in hardware or software.

Standards-based suite

A collection of communication rules that has industry backing and formal approval from recognized bodies.

DNS

A naming service that converts human-readable host labels into numerical network addresses.

DHCPv4

A service that automatically hands out IPv4 addressing details to endpoints at startup and reclaims them when unused.

DHCPv6

A service that automatically hands out IPv6 addressing details to endpoints at startup.

SLAAC

A method that lets a device derive its own IPv6 configuration using router announcements instead of a dedicated assignment server.

SMTP

A messaging protocol that sends mail from clients to mail servers and between mail servers.

POP3

A mail protocol that retrieves messages from a server and downloads them into a local application.

IMAP

A mail protocol that lets a user access and manage messages kept on a server while leaving them stored there.

FTP

A set of rules that enables interactive transfer of files between two systems over a communication path.

SFTP

A secure file transfer mechanism that uses encrypted sessions for moving data between systems.

TFTP

A simple, connectionless file-transfer mechanism offering best-effort delivery without built-in acknowledgment.

HTTPS

An encrypted form of web communication that protects data while it moves between browser and site.

REST

An approach to building services that uses resource-oriented URLs, standard methods, and web requests to support applications.

UDP

A connectionless transport mechanism that sends datagrams between processes without establishing a reliable session.

IPv4

A widely used version of the addressing and forwarding protocol that employs 32-bit locators for end-to-end delivery.

IPv6

A newer version of the addressing and forwarding protocol that employs 128-bit locators and expands the available address space.

NAT

A function that replaces internal IPv4 locators with globally routable ones when traffic leaves a private domain.

ICMPv4

A control and error-reporting mechanism for IPv4 that returns feedback from a destination or intermediate system to a source.

ICMPv6

A control and error-reporting mechanism for IPv6 that mirrors many of the capabilities of its IPv4 counterpart.

ICMPv6 Neighbor Discovery

A collection of messages that support resolving link-layer locators and detecting duplicate addresses in IPv6 environments.

OSPF

A link-state interior routing method that builds a hierarchical view of networks based on areas and shortest paths.

EIGRP

A Cisco-developed interior routing method that uses multiple metrics such as bandwidth, delay, load, and reliability to pick paths.

BGP

An exterior routing method that exchanges reachability between service providers and large organizations.

ARP

A mapping mechanism that discovers link-layer locators associated with IPv4 addresses on a local segment.

Ethernet

A family of standards defining how bits are formatted, signaled, and framed on wired access links.

WLAN

A group of standards defining how bits are framed and transmitted over 2.4 GHz and 5 GHz radio for local wireless access.

Encapsulation (analogy)

The act of placing one message inside another container, like putting a written note into a properly addressed envelope.

Encapsulation (network)

The process of wrapping data with protocol headers and trailers at each layer of the stack before transmission.

De-encapsulation

The step-by-step removal of protocol headers and trailers by a receiver as data travels up the stack to an application.

Message size rule

The idea that communication units are divided into reasonably small pieces to make them easier to transmit and understand.

Signal encoding

The conversion of bits into patterns of sound, light, or electrical impulses appropriate to a specific medium, then back into bits at the receiver.

Flow control

A mechanism that regulates how much data can be sent and at what rate so that a receiver is not overwhelmed.

Response timeout

A limit on how long a communicator waits for a reply before treating the attempt as failed and taking alternate action.

Access method

The rules that determine when a device may send on a shared medium, such as checking if a wireless channel is free.

Unicast

A one-to-one delivery approach where a message is addressed to a single destination endpoint.

Multicast

A one-to-many delivery approach where a message is sent to a selected group of interested endpoints.

Broadcast

A one-to-all delivery approach where a message is delivered to every endpoint on a local segment at once.

Layered model

A conceptual structure that divides communication functions into stacked sections so operations are modular and easier to manage.

OSI model

A seven-part reference framework that defines functions and services at each stage of communication from physical signaling up to user-facing processes.

TCP/IP model

A four-part reference framework aligned with the main groups of protocols in the modern suite, from access up to user data.

Segmentation

The division of a large data stream into smaller units so they can be sent as separate network packets.

Multiplexing

The interleaving of multiple conversations across a link so many exchanges can occur simultaneously.

Sequencing

The numbering and ordering of pieces of a broken-up message so they can be reassembled correctly at the destination.

Protocol Data Unit (PDU)

The name given to a data structure at a specific layer after headers or trailers for that layer have been applied.

Data (PDU)

The generic label for the application-level payload before lower-layer headers are added.

Segment

The transport-level PDU containing application bytes and transport headers.

Packet

The network-level PDU containing transport data wrapped with addressing information.

Frame

The data-link-level PDU containing higher-layer information, link headers, and often a trailer.

Bits

The electrical, optical, or radio representations of ones and zeros used for physical transmission.

Transport-layer address

A numeric value, such as a port, that identifies which local service or application should receive incoming bytes.

Network-layer address

A locator identifying the logical segment or system a device belongs to, used for end-to-end routing.

Data-link address

A hardware-centric identifier used on a local segment to deliver frames to the correct physical interface.