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3D1X2 Study - Sec+ Study - Basics - Part 1

Updated on June 3, 2019

OSI Model

Physical Layer - 1st Layer - Involves connections and cables

Data Link Layer - 2nd Layer - Involves switches and ports

Network Layer - 3rd Layer - Involves routers and routing protocols

Transport Layer - 4th Layer - Involves how information/packets are transported

Session Layer - 5th Layer - Service requests

Presentation Layer - 6th Layer - Format (ex: JPEG/GIF), Data compression, Encryption

Application Layer - 7th Layer - Applications on a computer (I.E., CHROME, etc.)


TCP vs UDP

TCP - Transmission Control Protocol - 20 bytes

  • Connection Oriented - 3way Handshake
  • STREAM ORIENTED
  • Reliable Data Delivery - Sequencing and Checksums
  • Will keep sending until delivered
  • Provides Flow Control
  • Big Headers
  • Example: Skype & Facetime

UPD - User Datagram Protocol - 8 bytes

  • Connectionless
  • MESSAGE ORIENTED
  • Send small amounts of data
  • No guarantee of sending/No congestion control/Less reliable
  • Example: E-Mail

Protocols & Ports

Protocol
Port
TCP/UDP
Key Words
FTP - File Transfer Protocol
20/21
TCP
Most commonly used file transfer
SSH - Secure Shell
22
TCP
Secure alternative to Telnet
Telnet
23
TCP
Not Secure
SMTP - Simple Mail Transfer Protocol
25
TCP
E-Mail
DNS - Domain Name System
53
TCP/UDP
Translate website names to IP addresses
DHCP - Dynamic Host Configuration Protocol
67/68
UPD
Gives DYNAMIC IP addresses (Meaning: you do not have to physically assign IPs)
TFTP - Trivial File Transfer Protocol
69
UDP
File transfer without establishing a session
HTTP - Hypertext Transfer Protocol
80
TCP
Web browsing - most common
POP - Post Office Protocol ver 3
110
TCP
Retrieve mail from server and then deleted contents from server
NTP - Network Time Protocol
123
UDP
Synchronize (clocks)
NetBIOS
137/138/139
TCP/UDP
interconnect Windows pcs
IMAP - Internet Message Access Protocol
143
TCP
Retrieves mail like POP but is 2nd best
SNMP - Simple Network Management Protocol
161/162
TCP/UDP
Sends messages about the network and if something happens (like a log)
BGP - Border Gateway Protocol
179
TCP
Maintains routing tables on public internet
LDAP - Lightweight Directory Access Protocol
389
TCP/UDP
ITU-T X.500
HTTPS - Hypertext Transfer Protocol SSL/TLS
443
TCP
Secure websites that begin with HTTPS instead of HTTP. Examples: places where you're going to enter private info like credit cards. I.E. Amazon
LDAPS - Lightweight Directory Access Protocol over TLS/SSL
636
TCP/UDP
Secure form of LDAP
FTP over TLS/SSL
989/990
TCP
Secure File Transfer Protocol

Topologies

A topology is HOW a network is laid out (blueprint). And can be both PHYSICAL and LOGICAL.


BASIC Physical Topologies (they can become more advanced)

**Bus - Computers connect in a straight line. (Think of the main network cable as a road and the computers as bus stops)

  • Easy to add more computers
  • Requires less cable
  • Inexpensive
  • Good for small networks

**Ring - All computers connect to the computer to the right and left of them (makes a circle. Like "ring around the rosey")

  • No collisions
  • Troubleshooting is easy
  • No terminators

**Star - All computers have independent lines to the network source (switch) (most common)

  • Failure of cable will not bring everything down
  • Easy to troubleshoot
  • Faster network speeds
  • Most common topology
  • Higher cost

**Mesh - Combining 2 or more of the above topologies. Also known as a Hybrid.

**Tree - Imitates extended star topology and inherits properties of bus topology

Subnetting and IP Classes - The Basics

CLASS
RANGE
HOST SIZE
A
1-126
LARGE (16M)
B
128-191
INTERMEDIATE (65K)
C
192-223
SMALL (250)
D
RESERVED
Multicasting
E
RESERVED
Research & Development

Network Devices

Modems - Gives access to INTERNET.

  • A modem is like the translator between your computer and the internet. Your computer sends/understands DIGITAL signals and the internet sends/understands ANALOG. To get them to talk, the modem has to translate.

Routers - Comes in AFTER the modem. Once the modem has the internet, the router GETS the internet to MULTIPLE switches/host/computers. (layer 3)


Switches - Come in AFTER the Router and connects directly to the computers. (layer 2)


Media Converter - A little box that converts signals from different type cables.

  • Example: Switch > Fiber > Media Converter boxes > Ethernet > PC


Multiplexers - Increased the amount of data that can be sent over the network. 4 inputs and 1 output.

Basic Network

Internet > Router > Switch > Laptops
Internet > Router > Switch > Laptops

Sec+ Study

When I took Sec+ in 2016, I was studying for version SY0-401. I bought the original study guide, but I also bought a book full of nothing but practice questions. This book explained why the correct answer is right and why the other answers are wrong. This really helped me with my word association and understanding how questions would be asked. I passed the 1st time.

https://www.amazon.com/CompTIA-Security-Get-Certified-Ahead/dp/1939136032/ref=sr_1_15?keywords=s

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