CompTIA A+ V15 220-1201

File Transfer Protocol (Active Mode Data Transfer)

TCP/20

File Transfer Protocol (Control)

TCP/21

Secure Shell

TCP/22

Telnet

TCP/23

Simple Mail Transfer Protocol

TCP/25

Domain Name System

TCP/53

UDP/53

Dynamic Host Configuration Protocol (Server)

UDP/67

Dynamic Host Configuration Protocol (Client)

UDP/68

Trivial File Transfer Protocol

UDP/69

HyperText Transfer Protocol

TCP/80

Kerberos

TCP/88

UDP/88

Post Office Protocol v3

TCP/110

Network Time Protocol

UDP/123

NetBIOS (Name)

UDP/137

NetBIOS (Datagram)

UDP/138

NetBIOS (Session)

TCP/139

Internet Message Access Protocol v4

TCP/143

Simple Network Management Protocol (Polling/Queries)

UDP/161

Simple Network Management Protocol (Traps/Alerts)

UDP/162

Lightweight Directory Access Protocol

TCP/389

UDP/389

HyperText Transfer Protocol Secure

TCP/443

Server Message Block

TCP/445

Simple Mail Transfer Protocol Secure

TCP/587

Lightweight Directory Access Protocol Secure

TCP/636

File Transfer Protocol Secure (Data Transfer)

TCP/989

File Transfer Protocol Secure (Control)

TCP/990

Internet Message Access Protocol Secure

TCP/993

Post Office Protocol 3 Secure

TCP/995

Remote Desktop Protocol

TCP/3389

UDP/3389

T568A Wiring Scheme

1. *Green/White*

2. *Green*

3. *Orange/White*

4. Blue

5. Blue/White

6. *Orange*

7. Brown/White

8. Brown

T568B Wiring Scheme

1. *Orange/White*

2. *Orange*

3. *Green/White*

4. Blue

5. Blue/White

6. *Green*

7. Brown/White

8. Brown

802.11b (WiFi 1)

2.4 GHz, MIMO Streams N/A
11 Mbit/s per stream, 11 Mbit/s total

802.11a (WiFi 2)

5 GHz, MIMO Streams N/A,
54 Mbit/s per stream, 54 Mbit/s total

802.11g (WiFi 3)

2.4 GHz, MIMO Streams N/A
54 Mbit/s per stream, 54 Mbit/s total

802.11n (WiFi 4)

2.4 & 5 GHz, 4 x MIMO
150 Mbit/s per stream, 600 Mbit/s total

802.11ac (Wi-Fi 5)

5 GHz, 8 x DL MU-MIMO
867 Mbit/s per stream, 6.9 Gbit/s total

802.11ax (Wi-Fi 6/6E)

2.4 & 5 GHz, 8 x DL & UL MU-MIMO
1,201 Mbit/s per stream, 9.6 Gbit/s total

802.11be (Wi-Fi 7)

2.4, 5, 6 GHz, 16 × DL & UL MU-MIMO
2.88 Gbit/s per stream, 46 Gbit/s total

Why are Li-Ion and LiPo batteries used instead of NiCad?

No “Memory Effect”

How big are storage drives in laptops?

2.5” form factor,

M.2 is even smaller.

What is Memory Effect?

Affects NiCad batteries. Battery “remembers” point it was repeatedly discharged, reducing usable run time. Remedied by full charge-discharge cycles.

How many pins are in a USB-C connector?

24

What versions of USB does USB-C support?

USB 2.0, 3.0, 3.1,& 4.0

Other than charging and data transfer, what other signals can USB-C transmit?

DisplayPort, HDMI, & Thunderbolt

DisplayPort

Digital information sent in packetized form
Compatible with HDMI & DVI as adapter
May include locking mechanism

HDMI

All digital, no analog
20m distance before losing too much signal
19-pin connector

Digital Video Interface (DVI)

Single link: 3.7gbit/s (HDTV @ 60 FPS)
Dual link: 7.4gbit/s (HDTV @ 85 FPS)
No audio

Video Graphics Array (VGA)

DB-15 connector
No audio
Analog signal

Thunderbolt

Premium, multi-purpose port for data, power, and displays.

Universal connection for laptops, docking stations, and external hard drives.

Relies on DisplayPort for video.

3G

1998

Updates improved speeds

Bandwidth improvement allowed new functionality (GPS, mobile TV, video on demand, & video conferencing.)

4G & LTE

Based on Global System for Mobile Communications (GSM) and Enhanced Data Rates for GSM Evolution (Edge)

150mbit/s download rates

LTE Advanced (LTE-A) supports 300mbit/s download rates

5G

2020

100-900mbit/s slower speeds, up to 10gbit/s

Significant IoT impact

Wi-Fi

Connect to 802.11 network for email/internet

Requires access point

Support voice communication, good when lacking cellular coverage

SIM

Modular chip identifier for cellular devices

Carrier/user information, phone number, cell network information, & storage

eSIM embedded into device

GPS

DoD creation, >30 satellites in orbit

Precise navigation within view of 4 satellites

Location based on timing, longitude, latitude, and altitude

What is the network topology aka the “road?”

Ethernet, DSL, Cable

If network topology is the road, what are the trucks?

Internet Protocol

If the trucks hold boxes, what does the boxes contain?

TCP/UDP data

[Header][ Ethernet Payload ][Trailer]

[ Header ] [ IP ] [ IP Payload ] [ Trailer ]

[ Header ] [ IP ] [ TCP ] [ TCP Payload ] [ Trailer ]

[ Header ] [ IP ] [ TCP ] [ HTTP Data ] [ Trailer ]

What OSI Layer does TCP & UDP belong in?

OSI Layer 4

The Transport Layer

Why would you use UDP?

Real-time communication (VoIP)

Connectionless protocols

Non-ephemeral ports

Permanent port numbers 0-1,023

Usually for a server/service

Ephemeral ports

Temporary port numbers 1024-65,535

Determined in real-time by client

Wireless networks are standardized by what organization?

Institute of Electrical and Electronics Engineers

802.11 Committee

What is RFID used for?

Access Badges

Inventory/Assembly line tracking

Animal identification

Anything that needs to be tracked

How does RFID work?

Radio energy transmitted to the tag

RF powers tag, ID transmitted back

Bidirectional communication

What is NFC used for?

Contactless Payments

Transit and Ticketing

Digital Keys and Access Control

Quick Device Pairing

Tags

Health Monitoring

DNS Servers

Names to IP addresses, vice versa

Load balanced

Managed by ISP or IT dept

DHCP Servers

IP address configuration

Available on most home routers

Enterprise DHCP redundant

File Share Services

Centralized storage of any file type

Standard system of file management

Front end hides protocol for copy, delete, rename, etc

Print Servers

Connects printer to network, may be software

May be built-in to the printer

Uses standard printing protocols like SMB, Internet Printing Protocol, or Line Printer Daemon.

Mail Servers

Stores & sends mail

24/7 Support

Managed by ISP or IT dept

Syslog Services

Standard for message logging

Central logging receiver integrated into a SIEM

Needs LOTS of disk space

Web Servers

Respond to browser requests

Uses HTTP/HTTPS

Stores web pages

Authentication Servers

Centralized management of login authentication resources

Almost always enterprise service

Redundant

Database Servers

Saves information in columns & rows

Relational database links tables together

Accessed using SQL

NTP Servers

Everything needs to work from the same clock

Clients requests time updates from server

Server responds to time requests from clients

Spam Gateways

Stops unsolicited mail at gateway

On-site or cloud-based

All-in-one Security Appliance

AKA Next-gen Firewall, Unified Threat Management, or Web Security Gateway

URL & spam filter

Content & malware inspection

CSU/DSU for older WAN

Switching & routing

IDS/IPS

Bandwidth Shaper

VPN Endpoint

Load Balancers

Invisible to end-user

Large-scale implementations/farms

Fault tolerance

Proxy Server

Intermediate server

Client requests proxy, proxy provides results

Useful for access control, caching, URL filtering, & content scanning

SCADA/ICS

PC manages industrial equipment

Distributed control systems for real-time information

Extensively segmented network

Legacy Systems

Really old, really important

Learning the old can be just as important as learning the new

Embedded Systems

Purpose-built

Not usual to directly access OS

Alarms, door security, time cards, etc

IoT Devices

Appliances

Smart devices

Thermostats

Doorbells, doors, and windows

May require segemented network for security

.com, .org, .net, .gov, .us, etc… are all examples of what?

Top-Level Domains

dig command

Primarily Linux & Mac command, can be installed to some Windows versions
Queries DNS information from websites
Returns IP Address & more

nslookup command

Windows specific DNS lookup

Resource Records (RR)

Database records of domain name services
IP addresses, certificates, host alias names, etc…
*Always backup DNS configurations*

Address (A or AAAA) Records

Defines IP address of a host
A records for IPv4
AAAA records for IPv6

Canonical Name (CNAME) Records

DNS entry that maps aliases to its true canonical domain
Used when running multiple services
Simplifies DNS configuration so you only have to update an IP address

Mail Exchanger (MX) Records

Determines host name for a mail server

Text (TXT) Records

Human-readable information
Can be used for verification purposes
Used for email security

Domain Keys Identified Mail (DKIM)

Digitally sign a domain’s outgoing mail
Validated by mail servers
Public key is in DKIM TXT record

Sender Policy Framework (SPF)

Lists all servers authorized to send emails for a domain
Prevents mail spoofing
Mail servers verifies if mail came from an authorized host

Domain-based Message Authentication, Reporting, & Conformance (DMARC)

Extension of SPF & DKIM
Prevents mail spoofing
DMARC TXT record allows domain owner to decide whether email should be received, rejected, or sent to spam

Dynamic Host Configuration Protocol (DHCP)

Released 1997
Automatic address/IP configuration
Used for almost all devices

DHCP DORA

Discover: Find DHCP Server
Offer: Get offer
Request: Lock in offer
Acknowledge: DHCP Server confirmation

DHCP Scope Options

IP address range—& excluded addresses
Subnet mask
Lease durations
DNS Server
Default Gateway
VoIP Servers

DHCP Pools

Grouping of IP addresses
Each subnet has its own scope
e.g.) Subnet:192.168.1.0/24