FBLA Network design

300+ terms of network design (FBLA)

OSI Model

A 7-layer conceptual framework (Physical, Data Link, Network, Transport, Session, Presentation, Application) that standardizes how network devices communicate

Physical Layer (L1)

OSI layer dealing with raw bit transmission over physical media like cables and radio signals; devices include hubs, repeaters, and cabling

Data Link Layer (L2)

OSI layer responsible for node-to-node delivery using MAC addresses; works with frames; devices include switches and bridges

Network Layer (L3)

OSI layer responsible for logical addressing and routing using IP addresses; works with packets; devices include routers

Transport Layer (L4)

OSI layer that manages end-to-end communication, reliability, segmentation, and flow control via TCP/UDP; works with segments

Session Layer (L5)

OSI layer that establishes, manages, and terminates sessions between applications

Presentation Layer (L6)

OSI layer that translates formats, encrypts, and compresses data for the application layer (SSL, JPEG, ASCII)

Application Layer (L7)

OSI layer closest to the end user; provides network services directly to applications (HTTP, FTP, SMTP, DNS)

OSI Mnemonic (bottom-up)

Please Do Not Throw Sausage Pizza Away = Physical, Data Link, Network, Transport, Session, Presentation, Application

Encapsulation

The process of wrapping data with protocol headers as it moves down the OSI layers before transmission

PDU (Protocol Data Unit)

The data unit at each OSI layer: bits (L1), frames (L2), packets (L3), segments (L4)

TCP/IP Model

A 4-layer model (Network Access, Internet, Transport, Application) that maps to the OSI model and underlies the modern internet

TCP (Transmission Control Protocol)

Connection-oriented, reliable transport protocol using a three-way handshake; guarantees delivery and order; used for web, email, file transfer

UDP (User Datagram Protocol)

Connectionless, unreliable transport protocol with low overhead; used for streaming, gaming, VoIP, and DNS queries

Three-Way Handshake

TCP connection setup process: SYN, SYN-ACK, ACK

ICMP

Internet Control Message Protocol; used for diagnostics and error reporting (ping and traceroute use it)

ARP (Address Resolution Protocol)

Protocol that maps an IP address to a MAC address on a local network

Unicast

One-to-one transmission from a single sender to a single receiver

Broadcast

One-to-all transmission sent to every device on a network segment

Multicast

One-to-many transmission sent only to devices that have joined a specific group

Simplex

Communication in one direction only (e.g. radio broadcast)

Half Duplex

Communication in both directions but only one direction at a time (e.g. walkie-talkie)

Full Duplex

Simultaneous communication in both directions (e.g. phone call, modern switched Ethernet)

CSMA/CD

Carrier Sense Multiple Access with Collision Detection; wired Ethernet method that detects and recovers from collisions

CSMA/CA

Carrier Sense Multiple Access with Collision Avoidance; wireless method that tries to prevent collisions before they occur

Collision Domain

A network segment where data packets can collide; each switch port is its own collision domain

Broadcast Domain

The set of devices that receive a broadcast frame; routers separate broadcast domains, switches do not (unless using VLANs)

Ethernet (802.3)

The IEEE standard family for wired LAN communication

Subnetting

Dividing a larger network into smaller logical sub-networks to improve efficiency, organization, and security

CIDR

Classless Inter-Domain Routing; IP allocation using slash notation (e.g. /24) to indicate the number of network bits

Subnet Mask

A 32-bit number separating the network portion from the host portion of an IP address (e.g. 255.255.255.0)

Class A Address

1.0.0.0 to 126.255.255.255; default mask 255.0.0.0; very large networks (16M+ hosts)

Class B Address

128.0.0.0 to 191.255.255.255; default mask 255.255.0.0; medium networks (~65K hosts)

Class C Address

192.0.0.0 to 223.255.255.255; default mask 255.255.255.0; small networks (254 hosts)

Private IP Ranges

10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16; reserved addresses not routable on the public internet

IPv4

32-bit addressing scheme in dotted decimal (e.g. 192.168.1.1); about 4.3 billion addresses

IPv6

128-bit addressing scheme in hexadecimal separated by colons; replaces IPv4 due to address exhaustion

MAC Address

48-bit physical hardware address burned into a NIC; written in hex; used for Layer 2 communication

Default Gateway

The router address a device uses to send traffic destined outside its local network

Loopback Address

127.0.0.1; used to test a device's own TCP/IP stack

APIPA

Automatic Private IP Addressing; a self-assigned 169.254.x.x address indicating a device could not reach a DHCP server

Static IP

A manually assigned IP address that never changes; used for servers and printers

Dynamic IP

An IP address automatically assigned by DHCP that can change over time

Octet

One of the four 8-bit sections of an IPv4 address (values 0-255)

Binary

Base-2 numbering system using only 0 and 1; the foundation of IP addressing math

Hexadecimal

Base-16 numbering system (0-9, A-F); used for MAC addresses and IPv6

Binary Place Values

128, 64, 32, 16, 8, 4, 2, 1; memorize these to convert binary octets to decimal quickly

Bit vs Byte

A bit is a single binary digit; a byte is 8 bits

Port (networking)

A 16-bit number identifying a specific process or service on a device

Port 20/21 - FTP

File Transfer Protocol; 20 is data, 21 is control

Port 22 - SSH

Secure Shell; encrypted remote command-line access (secure replacement for Telnet)

Port 23 - Telnet

Unencrypted remote access; legacy and insecure

Port 25 - SMTP

Simple Mail Transfer Protocol; sending email

Port 53 - DNS

Domain Name System; resolving domain names to IP addresses

Port 67/68 - DHCP

Dynamic Host Configuration Protocol; automatic IP assignment

Port 69 - TFTP

Trivial File Transfer Protocol; simple unauthenticated file transfer using UDP

Port 80 - HTTP

Unencrypted web traffic

Port 110 - POP3

Post Office Protocol v3; downloads email to one device

Port 123 - NTP

Network Time Protocol; synchronizes device clocks across a network

Port 143 - IMAP

Internet Message Access Protocol; syncs email across devices via the server

Port 161/162 - SNMP

Simple Network Management Protocol; monitoring and managing network devices

Port 389 - LDAP

Lightweight Directory Access Protocol; querying directory services like Active Directory

Port 443 - HTTPS

Encrypted web traffic via TLS/SSL

Port 445 - SMB

Server Message Block; Windows file and printer sharing

Port 514 - Syslog

Centralized logging protocol for network devices

Port 3389 - RDP

Remote Desktop Protocol; remotely accessing a Windows desktop

Star Topology

All devices connect to a central hub or switch; easy to manage but the central device is a single point of failure

Bus Topology

All devices share one central cable; cheap but a cable break disables the network

Ring Topology

Each device connects to exactly two others forming a circular data path

Mesh Topology

Devices interconnected with many redundant paths; high reliability, high cost

Hybrid Topology

A layout combining two or more topology types

Point-to-Point

A direct connection between exactly two devices

LAN

Local Area Network; small area like a home, office, or building

WAN

Wide Area Network; spans large geographic areas connecting multiple LANs

MAN

Metropolitan Area Network; spans a city or large campus

PAN

Personal Area Network; very short range, typically Bluetooth

Client-Server Model

Centralized servers provide resources and services to multiple client devices

Peer-to-Peer (P2P)

Devices share resources directly with each other without a central server

Intranet

Private internal network accessible only to an organization's members

Extranet

Controlled private network allowing access to authorized outside parties like vendors and partners

Scalability

A network design's ability to grow and handle increased demand without redesign

High Availability

Design goal of maximizing uptime through redundancy and failover (e.g. 99.999% uptime)

Single Point of Failure

Any component whose failure takes down the entire system; good design eliminates these

Network Segmentation

Dividing a network into smaller sections to improve security and performance

Physical Network Diagram

Documentation showing actual hardware, cabling, and physical connections

Logical Network Diagram

Documentation showing IP addressing, subnets, VLANs, and data flow rather than physical layout

Router

Layer 3 device that forwards packets between different networks using IP addresses

Switch

Layer 2 device connecting devices within a LAN; forwards frames using MAC addresses

Hub

Layer 1 device that broadcasts incoming data to all ports without filtering; obsolete

Bridge

Layer 2 device that connects and filters traffic between two network segments

Gateway

Device connecting two networks that use different protocols, translating between them

Repeater

Layer 1 device that regenerates and amplifies signals to extend transmission distance

Firewall

Security device or software that monitors and controls traffic based on defined rules

Packet Filtering Firewall

Inspects packets individually by IP, port, and protocol without tracking connection state

Stateful Firewall

Tracks the state of active connections and filters based on context

Access Point (AP)

Device allowing wireless devices to connect to a wired network via Wi-Fi

Modem

Converts digital signals to analog and back for transmission over telephone or cable lines

NIC

Network Interface Card; hardware allowing a device to connect to a network

Patch Panel

Mounted unit of ports used to organize and manage cabling in a server room

Load Balancer

Device that distributes incoming traffic across multiple servers to prevent overload