Common Ports

Know the port number, protocol (TCP/UDP), and what the service does. These are almost always on the exam.

Exam tip TCP = connection-oriented, needs handshake. UDP = fast, no receipt confirmation. DNS uses BOTH. DHCP is always UDP.

File Transfer & Remote Access

Port	Protocol	Name	What it does	Example use
20	TCP	FTP (Data)	Transfers file data in active mode	Downloading a file from an FTP server
21	TCP	FTP (Control)	Commands/control channel for FTP	Logging in, issuing commands like LIST, GET
22	TCP	SSH	Encrypted remote shell access	Remotely managing a Linux server securely
23	TCP	Telnet	Unencrypted remote console access	Legacy router config — NOT for production
3389	TCP	RDP	Graphical remote desktop (Windows)	IT support viewing a user's Windows desktop

Email

Port	Protocol	Name	What it does	Example use
25	TCP	SMTP	Server-to-server email delivery	Gmail sends your email to recipient's server
110	TCP	POP3	Downloads email to client, deletes from server	Old email client downloads inbox, offline only
143	TCP	IMAP4	Reads/manages email on server (sync)	Phone and laptop both see same inbox state

Web & Directory

Port	Protocol	Name	What it does	Example use
80	TCP	HTTP	Unencrypted web traffic	http://example.com — no padlock icon
443	TCP	HTTPS	Encrypted web traffic (TLS)	https://bank.com — padlock in browser
389	TCP	LDAP	Query/modify directory services	Windows Active Directory user lookups

Network Infrastructure

Port	Protocol	Name	What it does	Example use
53	UDP / TCP	DNS	Converts domain names to IP addresses	www.google.com → 142.250.x.x
67	UDP	DHCP (Server)	Server listens for IP address requests	Router assigns 192.168.1.x to new device
68	UDP	DHCP (Client)	Client sends request for IP config	Your laptop broadcasts for an IP address on boot
123	UDP	NTP	Time synchronization	Windows syncing clock to time.windows.com
161	UDP	SNMP	Monitor/manage network devices	Network management software polling switch stats

Windows Networking (SMB)

Port	Protocol	Name	What it does	Example use
137	UDP	NetBIOS Name	Register/find Windows services by name	Finding "\\FILESERVER" on a Windows network
139	TCP	NetBIOS Session	Connection-oriented data transfer (NetBIOS)	Older Windows file sharing over NetBIOS
445	TCP	SMB Direct	File/printer sharing without NetBIOS	\\server\share — modern Windows file sharing

Memory trick — SMTP vs IMAP vs POP3 SMTP = Send Mail To People (25). POP3 = Post Office Protocol, downloads once (110). IMAP = "I" can see my mail everywhere, syncs (143).

Cables & Connectors

The deep nuances — speed, distance, GHz bands, channel width, connector types, and use cases.

Ethernet (Twisted Pair) — Category Cables

Category	IEEE Standard	Max Speed	Max Distance	Notes / Exam Gotcha
Cat 5	1000BASE-T	1 Gbps	100 m	Minimum for Gigabit. No 10G support.
Cat 5e (enhanced)	1000BASE-T	1 Gbps	100 m	"e" = less crosstalk. Most homes still use this.
Cat 6	10GBASE-T	10 Gbps (55m) / 1 Gbps (100m)	100 m (55m for 10G)	Has internal plastic SPLINE separator. Know this!
Cat 6A (augmented)	10GBASE-T	10 Gbps	100 m	Full 10G at full distance. ALWAYS shielded (STP). "A" = augmented.
Cat 7	10GBASE-T	10 Gbps	100 m	Does NOT use RJ-45. Uses GG-45 or TERA connector. S/FTP shielding.
Cat 8	25/40GBASE-T	25–40 Gbps	30 m only	Data center only. Short distance trade-off for massive speed.

Exam trap Cat 6 = 10G only up to 55m. Cat 6A = 10G full 100m. Cat 7 does NOT use RJ-45. Cat 8 = 30m max.

Shielding Abbreviations (know these!)

Format

(Overall) / (Per Pair) TP

UUnshielded
SBraided shielding
FFoil shielding

Examples

UTPUnshielded Twisted Pair — most common
STPShielded Twisted Pair — direct burial, EMI areas
S/FTPBraided overall + foil on each pair (Cat 7)
F/UTPFoil overall, no shielding on pairs

568A vs 568B Wire Color Order

TIA/EIA 568A

Pin 1 — White/Green

Pin 2 — Green

Pin 3 — White/Orange

Pin 4 — Blue

Pin 5 — White/Blue

Pin 6 — Orange

Pin 7 — White/Brown

Pin 8 — Brown

TIA/EIA 568B (Most common)

Pin 1 — White/Orange

Pin 2 — Orange

Pin 3 — White/Green

Pin 4 — Blue

Pin 5 — White/Blue

Pin 6 — Green

Pin 7 — White/Brown

Pin 8 — Brown

Note 568B is most common in US orgs. Both ends must match. Mixing A on one end / B on the other is NOT a crossover cable.

Fiber Optic

Type	Light Source	Core Size	Max Distance	Jacket Color	Standards
Single-Mode (SMF)	Laser	~9 µm (small)	Up to 100 km	Yellow	OS1, OS2
Multi-Mode (MMF)	LED	~50–62.5 µm (large)	Up to 550 m	Orange or Aqua	OM1–OM5

Memory trick SMF = Single laser = Skinny core = Super long distance. MMF = Multiple bouncing paths = short distance = LED. OM3/OM4 = Aqua jacket, support 10G.

Fiber Connectors

Connector	Full Name	Mechanism	Notes
ST	Straight Tip	Bayonet — stick and twist to lock	Older; common in older data centers
SC	Subscriber Connector	Push to lock, pull to release	Square shape. Very common in data centers.
LC	Lucent Connector	Clip locks in place, press to release	Smaller/compact. Most common modern connector.

USB Versions

Name	Also Called	Speed	Connector	Port Color
USB 1.1	Full Speed	12 Mbps	Type A/B	White/Black
USB 2.0	Hi-Speed	480 Mbps	Type A/B/Mini/Micro	Black or White
USB 3.2 Gen 1	USB 3.0 / 3.1 Gen 1 / SuperSpeed	5 Gbps	Type A (blue), Micro-B	Blue
USB 3.2 Gen 2	USB 3.1 Gen 2 / SuperSpeed+	10 Gbps	Type A (teal), USB-C	Teal
USB 3.2 Gen 2×2	SuperSpeed+ Dual Lane	20 Gbps	USB-C only	—
USB4	—	40 Gbps	USB-C only	—

Alias confusion — exam favorite USB 3.0 = USB 3.1 Gen 1 = USB 3.2 Gen 1 = 5 Gbps. Know all the names for the same thing!

Thunderbolt

Version	Speed	Connector	Notes
Thunderbolt 1	10 Gbps/channel (20 Gbps total)	Mini DisplayPort	2 channels
Thunderbolt 2	20 Gbps	Mini DisplayPort	Aggregated channels
Thunderbolt 3	40 Gbps	USB-C	Max 3m copper, 60m optical. Daisy-chain 6 devices.
Thunderbolt 4	40 Gbps	USB-C	Dual 4K display support, more PCIe bandwidth.

Video Cables

Connector	Signal	Audio?	Notes
HDMI (Type A)	Digital	Yes	19-pin. ~20m passive. Consumer standard.
DisplayPort	Digital (packetized)	Yes	Can daisy-chain monitors. Locking connector.
DVI-D	Digital only	No	Electrically compatible with HDMI (passive adapter OK)
DVI-A	Analog only	No	Backward compatible with VGA
DVI-I	Digital + Analog	No	"I" = Integrated. Has both. Most flexible DVI.
VGA (DE-15)	Analog only	No	Blue connector, 15 pins. Degrades after 5–10m.

Storage Cables

Interface	Speed	Length	Connector	Notes
SATA Rev 1	1.5 Gbps	1 m	7-pin data + 15-pin power	L-shaped, keyed, can't reverse
SATA Rev 2	3.0 Gbps	1 m	7-pin data + 15-pin power
SATA Rev 3	6.0 Gbps	1 m	7-pin data + 15-pin power	Most common. 600 MB/s effective throughput.
eSATA	Matches SATA version	2 m	Different external connector	No power over cable. Externally connected SATA.
M.2 (SATA)	6 Gbps	On-board slot	B key or B+M key	Same SATA speed, tiny form factor
M.2 (NVMe)	Up to 64 Gbps (PCIe 4.0 x4)	On-board slot	M key only	Uses PCIe. FAR faster than SATA. Check key type!
IDE/PATA	133 Mbps (ATA-7)	45 cm	40-pin ribbon	Wide flat ribbon. Legacy only.

M.2 exam trap M.2 form factor does NOT guarantee NVMe. Could be SATA. Must check documentation and key type (M key = NVMe capable, B/B+M key = SATA).

Copper Connectors Quick Reference

Connector	Full Name	Pins	Used For
RJ-45	Registered Jack 45	8P8C	Ethernet
RJ-11	Registered Jack 11	6P2C	Telephone / DSL
F-connector	—	Coaxial, threaded	Cable TV / DOCSIS cable modem (RG-6)
DB-9 / RS-232	D-sub	9 pin	Serial console access (router/switch config)
Molex	—	4-pin	Legacy power: HDDs, fans, optical drives (+12V, +5V)

Wireless Networks

802.11 standards, frequencies, channel widths, Bluetooth, and short-range wireless.

802.11 Standards

Standard	Wi-Fi Gen	Frequency	Max Speed	Channel Width	Notes
802.11a	—	5 GHz	54 Mbps	20 MHz	Older, less range than 2.4 GHz
802.11b	—	2.4 GHz	11 Mbps	22 MHz	Original Wi-Fi standard
802.11g	—	2.4 GHz	54 Mbps	20 MHz	Backward compatible with 802.11b
802.11n	Wi-Fi 4	2.4 / 5 GHz	600 Mbps	20 / 40 MHz	MIMO — multiple antennas
802.11ac	Wi-Fi 5	5 GHz only	3.5 Gbps	20/40/80/160 MHz	MU-MIMO. 5 GHz only = shorter range
802.11ax	Wi-Fi 6 / 6E	2.4 / 5 / 6 GHz	9.6 Gbps	Up to 160 MHz (320 MHz for 6E)	OFDMA, better in crowded environments. 6E adds 6 GHz band.
802.11be	Wi-Fi 7	2.4 / 5 / 6 GHz	46 Gbps	Up to 320 MHz	Multi-Link Operation (MLO). Latest standard.

Frequency Bands — Channel Behavior

2.4 GHz Band

Channels1–11 (North America). Only 1, 6, 11 are non-overlapping.
Width20 MHz channels standard
RangeBetter range, more wall penetration
InterferenceCrowded — shares with Bluetooth, microwaves, baby monitors
Freq range2412 MHz to 2482 MHz

5 GHz Band

ChannelsMany non-overlapping channels (24+ in US)
Width20, 40, 80, 160 MHz
RangeShorter range, less wall penetration
SpeedFaster — less interference
Freq range5150–5825 MHz

6 GHz Band (Wi-Fi 6E/7)

Width20, 40, 80, 160, 320 MHz channels
BenefitHuge spectrum, no legacy devices, very low interference
RangeShortest of three bands — needs to be close

Cellular Networks

Generation	Introduced	Speed	Key Features
3G	1998	Several Mbps	GPS, mobile TV, video conferencing
4G / LTE	~2010	150 Mbps down (LTE) / 300 Mbps (LTE-A)	Based on GSM/EDGE. LTE-A = Advanced.
5G	2020	100 Mbps–10 Gbps (depends on frequency)	Low latency, massive IoT support, mmWave for high speed

Short-Range Wireless

Technology	Range	Frequency	Use Cases
Bluetooth	~10 m (consumer)	2.4 GHz (ISM band)	Headsets, speakers, keyboards, tethering, health monitors
NFC	≤4 cm	~13.56 MHz	Payments (Apple Pay), access badges, Bluetooth pairing bootstrap
RFID	Varies (passive to active)	Varies	Inventory tracking, access badges, pet identification

NFC vs RFID RFID is mostly one-way (read a tag). NFC is two-way communication, builds on RFID, and requires much closer proximity (4cm).

Hardware

Motherboards, CPUs, power, BIOS, connectors, display types, and printers.

Motherboard Form Factors

Form Factor	Size	Expansion Slots	Best For
ATX	Standard / large	Most (7 slots)	Full desktop builds, max expandability
microATX (uATX)	Smaller, same mounting	Limited (typically 4)	Mid-tower builds, backward compat with ATX
Mini-ITX	Smallest, screw-compatible with ATX	1 PCIe slot	HTPCs, thin clients, embedded/streaming devices

Power Connectors

Connector	Pins	Voltage	Powers
24-pin ATX	24 (20+4)	+3.3V, ±5V, ±12V	Main motherboard power. Can connect 24-pin to 20-pin board.
4/8-pin CPU (EPS12V)	4 or 8 (square)	+12V	CPU. Located near CPU socket. Forgetting this = no POST.
PCIe 6-pin	6	+12V	GPU — 75 watts
PCIe 8-pin	8 (6+2)	+12V	GPU — 150 watts per connector
SATA Power	15	3.3V, 5V, 12V	SATA drives, SSDs
Molex (4-pin)	4	+12V, +5V	Legacy HDDs, fans, optical drives

Voltage Rails — What Runs on What

+12V

PCIe adapters, HDD motors, cooling fans, most modern components

+5V

Some motherboard components. Many now use +3.3V instead.

+3.3V

M.2 slots, RAM slots, motherboard logic circuits

+5VSB

Standby voltage — keeps USB and Wake-on-LAN active when off

-12V

Integrated LAN, older serial ports, some PCI cards

PCIe Expansion Bus

Designation	Lanes	Bandwidth	Common Use
PCIe x1	1	~1 GB/s	Sound cards, NICs, USB expansion
PCIe x4	4	~4 GB/s	NVMe M.2 adapters, some SSDs
PCIe x16	16	~16 GB/s	Graphics cards — primary GPU slot

"x" is pronounced "by" — x16 = "by 16." PCIe is serial, unidirectional lanes. Slower devices don't slow down others.

BIOS / UEFI

Legacy BIOS

Age25+ years old. Text-only interface.
LimitNo modern hardware driver support
BootMBR (Master Boot Record) only

UEFI BIOS

StandardUnified Extensible Firmware Interface — based on Intel EFI
FeaturesGraphical + text, Secure Boot, GPT partition support
Secure BootVerifies bootloader digital signature — prevents malware
TPMTrusted Platform Module — hardware encryption chip

Display Types

Type	How it works	Pros	Cons
TN (Twisted Nematic) LCD	Liquid crystals twist to block backlight	Fastest response (gaming)	Poor viewing angles, color shift
IPS (In-Plane Switching) LCD	Crystals rotate parallel to panel	Excellent color, wide viewing angle	More expensive, slower response than TN
VA (Vertical Alignment) LCD	Crystals perpendicular to panel	Good compromise TN/IPS, good color	Slower response than TN
OLED	Organic compound emits light directly	No backlight needed, perfect blacks, thin, flexible	More expensive, can burn-in
Mini LED	Same as LCD but tiny LED backlight zones	Much better black levels and local dimming than LCD	Still needs backlight unlike OLED

Printer Types

Printer	How It Works	Key Maintenance	Media
Laser	Laser + charged drum + toner + fuser heat	Replace toner, fuser, feed rollers. Reset page counter!	Plain paper
Inkjet	Tiny ink drops onto page (CMYK)	Clean print heads, replace cartridges, calibrate	Plain / photo paper
Thermal	Heat turns special paper black — no ink	Clean heating element with IPA. Replace thermal paper only.	Thermal paper (sensitive to heat/light)
Dot-matrix (Impact)	Pins hit ribbon against paper	Replace ribbon, replace print head	Continuous/multi-part carbon paper

Laser printer 6-step process 1. Processing → 2. Charging (corona wire) → 3. Exposing (laser) → 4. Developing (toner sticks) → 5. Transferring (toner to paper) → 6. Fusing (heat melts toner)

Memory & Storage

RAM types, DDR generations, RAID levels, and storage media.

RAM Types

Type	Form Factor	Max per DIMM	Notes
SDRAM	DIMM	—	Synchronous with system clock. Classic baseline.
DDR3 SDRAM	DIMM / SO-DIMM	16 GB	Twice DDR2 speed. No backward compat.
DDR4 SDRAM	DIMM / SO-DIMM	64 GB	Faster frequencies than DDR3. Key notch moved.
DDR5 SDRAM	DIMM / SO-DIMM	64 GB+	Key moved again. No backward compat. Higher bandwidth.
SO-DIMM	Small Outline	Same as DIMM gen	Laptop form factor — half width of DIMM

Key rule Every DDR generation has a different key notch position — you physically cannot install the wrong generation. No DDR is backward compatible.

Memory Features

ECC (Error Correcting Code)

WhatDetects AND corrects single-bit errors on the fly
WhereServers, VM hosts, database systems
NoteLooks identical to non-ECC. Must be supported by mobo.

Multi-Channel Memory

Dual2x memory buses = 2x throughput. 2 matched sticks.
Quad4x throughput. Slots often color-coded on mobo.
NoteUse identical sticks for best results. Check slot colors.

Storage Devices

Type	Speed (IOPS)	Moving Parts?	Notes
HDD (7200 RPM)	~100–200 IOPS	Yes — platter + arm	Clicking = failure. Grinding = imminent failure.
SSD (SATA)	~50,000–100,000 IOPS	No	Flash memory. Up to 600 MB/s (SATA III limit).
NVMe SSD (PCIe)	Up to 1,000,000 IOPS	No	3–7 GB/s sequential. Uses PCIe lanes, not SATA.
eMMC	Low	No	Soldered flash. Budget devices, not upgradeable.

SATA vs NVMe SATA uses AHCI controller (designed for spinning disks). NVMe uses PCIe bus directly — far lower latency, designed for flash. Both can use M.2 form factor but NVMe is dramatically faster.

RAID Levels

Level	Name	Min Drives	Redundancy?	Survive How Many Failures?	Use Case
RAID 0	Striping	2	None	0 — any drive failure = total data loss	Max speed, no safety (video editing scratch)
RAID 1	Mirroring	2	Full duplicate	Array works as long as 1 drive is alive	Boot drives, critical data
RAID 5	Striping + parity	3	One parity block	1 drive failure — can lose all but one	Efficient storage with protection
RAID 6	Striping + 2x parity	4	Two parity blocks	2 drive failures — needs all but two	High availability, large arrays
RAID 1+0	Stripe of mirrors	4	Mirrored sets	Can lose all but one from each mirror set	Best speed + redundancy, expensive

RAID ≠ Backup RAID protects against drive failure, not accidental deletion, ransomware, or fire. Always have a separate backup!

Networking Concepts

IP addressing, DNS records, DHCP, VLANs, VPNs, network types, and devices.

IPv4 Private Address Ranges (RFC 1918)

Range	CIDR Block	Subnet Mask	Class	Addresses
10.0.0.0 – 10.255.255.255	10.0.0.0/8	255.0.0.0	Class A	16.7 million
172.16.0.0 – 172.31.255.255	172.16.0.0/12	255.240.0.0	16x Class B	1.04 million
192.168.0.0 – 192.168.255.255	192.168.0.0/16	255.255.0.0	256x Class C	65,536

APIPA Range 169.254.1.0 – 169.254.254.255 — Automatically assigned when DHCP fails. Link-local only. Not routable. Always means "DHCP problem" on the exam.

DNS Record Types

Record	Full Name	What It Stores	Example
A	Address	IPv4 address for a hostname	www.example.com → 93.184.216.34
AAAA	Quad-A	IPv6 address for a hostname	www.example.com → 2606:2800::1
CNAME	Canonical Name	Alias pointing to another name	ftp.example.com → www.example.com
MX	Mail Exchanger	Mail server for a domain	example.com mail → mail.example.com
TXT	Text Record	Free-form text, often for verification	SPF, DKIM, domain ownership proofs

Email Security DNS Records

SPF

Sender Policy Framework

Lists all servers authorized to send email for a domain. Stored as a TXT record. Prevents mail spoofing.

DKIM

DomainKeys Identified Mail

Digitally signs outgoing mail. Public key stored in DNS TXT record. Receiving server validates signature.

DMARC

Domain-based Message Authentication, Reporting, and Conformance

Extends SPF + DKIM. You define policy: accept, quarantine, or reject emails that fail SPF/DKIM. Reports sent back to admin.

DHCP — DORA Process

1. Discover

Client broadcasts "is there a DHCP server?" (UDP)

2. Offer

DHCP server responds with an IP address offer

3. Request

Client broadcasts "I accept this offer" (confirms choice)

4. Acknowledge

Server confirms the lease. Client gets IP, mask, gateway, DNS.

Network Types

Acronym	Name	Scale	Technology
PAN	Personal Area Network	Body / room (~10m)	Bluetooth, NFC, IR
LAN	Local Area Network	Building / campus	Ethernet (802.3), Wi-Fi (802.11)
WLAN	Wireless LAN	Building / campus	802.11 Wi-Fi
MAN	Metropolitan Area Network	City	Metro Ethernet, fiber rings
WAN	Wide Area Network	Globe	MPLS, point-to-point serial, satellite
SAN	Storage Area Network	Data center	Fibre Channel, iSCSI — block-level storage

Key Network Devices

Device	OSI Layer	Forwards By	Notes
Hub	L1 Physical	Broadcasts to all ports	Legacy. Creates one big collision domain.
Switch	L2 Data Link	MAC address (frame)	ASIC hardware. Can have PoE. Managed = VLAN/STP support.
Router	L3 Network	IP address (packet)	Connects different subnets. NAT, ACLs, routing protocols.
Access Point	L2	MAC address	Not a router. Bridge between wired and wireless. Extends LAN.
Firewall	L4 (Transport)	Port / IP rules	Filters traffic by port/IP. Can proxy, VPN, and route.

PoE Standards

Standard	Power	Current Max	Notes
PoE (802.3af)	15.4W	350 mA	Original PoE standard. VoIP phones, small APs.
PoE+ (802.3at)	25.5W	600 mA	Larger APs, PTZ cameras
PoE++ (802.3bt) Type 3	51W	600 mA	High-power devices
PoE++ (802.3bt) Type 4	71.3W	960 mA	Works with 10GBASE-T. Laptops, high-end APs.

Cloud & Virtualization

Cloud service models, deployment types, hypervisors, and key characteristics.

Cloud Service Models — What YOU Manage

Model	You manage	Provider manages	Example
IaaS — Infrastructure as a Service	OS, runtime, data, apps	Hardware, network, storage, virtualization	AWS EC2, Azure VMs — you control the OS up
PaaS — Platform as a Service	App code and data only	Everything else including OS and runtime	Salesforce, Google App Engine — just write code
SaaS — Software as a Service	Nothing (just use it)	Everything	Google Workspace, Microsoft 365 — ready to go

Memory: Pizza as a Service IaaS = Bought pizza ingredients, made it yourself. PaaS = Restaurant kitchen, you just cook. SaaS = Ordered delivery — you just eat.

Cloud Deployment Models

Private

Your own virtualized data center. Dedicated resources. Highest control and cost.

Public

Available over the Internet to anyone. AWS, Azure, GCP. Pay for what you use.

Hybrid

Mix of public + private. On-prem for sensitive data, cloud for burst capacity.

Community

Multiple organizations share same infrastructure. e.g., government agencies.

Cloud Characteristics

Elasticity

Scale resources up or down instantly based on demand. Pay only for what you use.

Availability

Always-on with redundancy. Multiple data centers, failover built in.

Metered

Charged for usage: ingress (upload), storage, egress (download).

Multitenancy

Multiple customers share same infrastructure. Isolated from each other logically.

Hypervisor Types

Type	How It Works	Examples	Notes
Type 1 — Bare Metal	Hypervisor IS the OS — runs directly on hardware	VMware ESXi, Hyper-V (Server), Xen	Enterprise. Better performance. No host OS overhead.
Type 2 — Hosted	Hypervisor runs inside an existing OS	VMware Workstation, VirtualBox, Parallels	Desktop/development use. Host OS required.

Virtualization Concepts

VDI

Virtual Desktop Infrastructure

Desktops run on a server. Thin client connects over network. Apps run remotely. Minimal local hardware needed.

Containerization

e.g., Docker

App + dependencies in a container. Shares host OS kernel. Lightweight, portable. Apps can't interact with each other.

VM Escaping

Security Risk

Malware recognizes it's in a VM, compromises the hypervisor, then jumps to other guest VMs. Critical security concern.

Sandboxing

Isolated Testing

Isolated environment with no connection to production. Develop and test code safely. Roll back with snapshots.

Key Acronyms & Definitions

Phrases, definitions, and abbreviations you need to know cold for the 220-1201 exam.

Networking

TCP

Transmission Control Protocol

Connection-oriented, ordered, reliable delivery. 3-way handshake (SYN, SYN-ACK, ACK).

UDP

User Datagram Protocol

Connectionless, fast, no guarantee. Best for DNS, DHCP, streaming, TFTP.

NAT

Network Address Translation

Maps private IPs to a public IP. Conserves IPv4 addresses.

VLAN

Virtual Local Area Network

Logical network separation on the same physical switch. Uses 802.1Q tagging.

VPN

Virtual Private Network

Encrypted tunnel over public network. Client-to-site or site-to-site.

APIPA

Automatic Private IP Addressing

169.254.x.x assigned when DHCP fails. Link-local, not routable.

DOCSIS

Data Over Cable Service Interface Specification

Standard for cable modem internet. Used with F-connector / coax.

SSID

Service Set Identifier

The name of a Wi-Fi network.

SNMP

Simple Network Management Protocol

UDP/161. Monitor and manage network devices.

ONT

Optical Network Terminal

Converts fiber (ISP side) to copper (your side). Demarc point for fiber internet.

Hardware & Storage

POST

Power-On Self Test

BIOS routine at startup. Tests CPU, memory, video. Beep codes indicate failures.

UEFI

Unified Extensible Firmware Interface

Modern replacement for BIOS. Graphical, supports Secure Boot and GPT.

TPM

Trusted Platform Module

Hardware chip for encryption keys. Single-device use. BitLocker uses it.

HSM

Hardware Security Module

Like TPM but for enterprise/multi-device. Often a separate card or appliance.

NVMe

Non-Volatile Memory Express

Protocol for SSD over PCIe. Much faster than SATA AHCI. Low latency.

AHCI

Advanced Host Controller Interface

SATA interface standard. Designed for spinning hard drives. Slower than NVMe.

RAID

Redundant Array of Independent Disks

Multiple drives for speed/redundancy. NOT a substitute for backup.

SMART

Self-Monitoring, Analysis and Reporting Technology

Built-in drive health monitoring. Warning signs = back up and replace.

DIMM

Dual Inline Memory Module

Desktop RAM. 64-bit data width. Different contacts on each side.

SO-DIMM

Small Outline DIMM

Laptop RAM. Half the width of DIMM. Same generations (DDR3/4/5).

Cloud & Virtualization

IaaS

Infrastructure as a Service

You manage OS up. Provider manages hardware. AWS EC2, Azure VMs.

PaaS

Platform as a Service

You manage app + data only. Provider manages OS and runtime.

SaaS

Software as a Service

You just use the app. Provider manages everything. Google Docs, O365.

VDI

Virtual Desktop Infrastructure

Desktops run on a server. Desktop as a Service (DaaS). Thin clients.

VM

Virtual Machine

Software emulation of a complete computer running on a hypervisor.

SCADA

Supervisory Control and Data Acquisition

Industrial Control System. Power plants, manufacturing. Must be segmented from regular network.

IoT

Internet of Things

Smart devices: thermostats, cameras, refrigerators. Should be on segmented network.

Mobile & Wireless

NFC

Near-Field Communication

Two-way, ≤4cm. Payments, access badges. Builds on RFID.

RFID

Radio-Frequency Identification

Mainly one-way. Tags, inventory, pet chips. No power needed on tag.

SIM

Subscriber Identity Module

Unique identifier card for cellular devices. Can have dual-SIM.

LTE

Long Term Evolution

4G standard. Based on GSM/EDGE. 150 Mbps down standard, 300 Mbps LTE-A.

PAN

Personal Area Network

Short-range personal network. Bluetooth, NFC. Your phone + wireless earbuds.

MDM

Mobile Device Management

Centrally manage, secure, and wipe mobile devices in an organization.

Print & Display

PCL

Printer Command Language

HP's printing language standard. Most common across the industry.

CMYK

Cyan, Magenta, Yellow, Key (Black)

Color model for inkjet printing. 4 separate cartridges typically.

OPC

Organic Photoconductor (Drum)

Light-sensitive drum in laser printer. Keep it in the bag — sensitive to light!

OLED

Organic Light Emitting Diode

Each pixel emits its own light. No backlight. Perfect blacks. Thin + flexible.

IPS

In-Plane Switching (LCD)

Best color accuracy and viewing angles. More expensive than TN.

TN

Twisted Nematic (LCD)

Fastest response time (gaming). Poor viewing angles.

ADF

Automatic Document Feeder

Feeds multiple pages through scanner automatically.

SMB

Server Message Block

Windows file/printer sharing protocol. Also called CIFS. Port 445.