Network+ (N10-008)
Section 2: Network Basics
3. Network Basics (OBJ. 1.2)
Networks - are used to make connections between machines
Personal Area Network (PAN) - network that has small distance
Converged Network - all data (voice, video and data) transmits in one single line
5 nines of availability (99.999%) - isn't 100% uptime, but close and reliable
Kinds of Network Traffic
File Sharing
Video Chatting
Surfing the Web
Social Media
Streaming Video
Email
Voice over IP
In this section we are covering the topics:
Network Components
Network Resources
Network Geography
Network Topologies
Internet of Things (IoT)
4. Network Components (OBJ. 2.1)
Network Components
Client
Server
Wireless Access Points
Hub
Switch
Router
WAN Link
Media
Client - a device used by an end-user to access and connects the network
Workstation, laptop, tablet, phone, smart TV or other terminal device
Server - a device that provides resources to the rest of network and provides different functions, also a dedicated hardware and specialized software
Email server, file server, chat server, print server
Hub - older technology that connects network devices together, it can lead to network errors
Wireless Access Points (WAP) - device that allows wireless devices to connect into a wired network, also it is a wireless hub
Switch - device that connects network devices together (like a next generation/smart hub), sends info on a specific port
Router - connects 2 different networks together and forwards traffics to and from a network, modern routers rely on IP address
Media - connects 2 devices or a device to a switch port
Copper Cable, Fiber optic cable, Radio waves
Wide Area Network (WAN) Link - physically connects 2 geographically dispersed networks
DSL Line, Cellular, Satellite, Microwave
5. Network Resources (OBJ. 1.2)
Network Resources - how is data moved around the network
Models of Network Resources
Client/Server Model
Peer-to-Peer Model
Client/Server Model - uses dedicated server to provide access to files, scanners, printers and other resources, administration and backup are easier because of 1 centralized server
Peer-to-Peer Model - peers share resources (files/printers) directly with others, administration and backup is difficult because it is located on different machines
Napster - uses Peer-to-Peer Model to share files back in the day
6. Network Geography (OBJ. 1.2)
Network Geography - about distance
Personal Area Network (PAN) - smallest type of wired or wireless network and covers the least amount of area, 10 ft. or less
Bluetooth, USB connections
Local Area Network (LAN) - connects components within a limited distance, few hundred ft
Office building, small office, school, house
Campus Area Network (CAN) - connects LANs that are building-centric across a university, industrial park, or business park, also spread across buildings in an area, few miles
Metropolitan Area Network (MAN) - connects scattered locations across city or metro area, up to 25 miles
buildings scattered in 1 city, police department
Wide Area Network (WAN) - connects geographically disparate internal networks and consists of leased lines or VPNs
Worldwide coverage, State, Country, World, Internet, LAN to LAN
8. Wired Network Topology (OBJ. 1.2)
Physical Topology - how devices connected physically by media, focused on physical layout of the cabling
Logical Topology - how devices connected logically, focused on network flow
Types of Topology
Bus Topology - uses a single cable where each device taps into by using etheir a vampire tap or a T-connector
Ring Topology - uses a cable running in a circular loop where each device connects the ring but data travels in a singular direction, no redundancy
Token Ring - uses an electronic token to prevent collisions when communicating on the network, eliminate collisions around a network
Fiber Distributed Data Interface (FDDI ring) - use to counter-rotating rings for redundancy, clockwise and counter-clockwise direction
Star Topology - most popular physical LAN topology where devices connect to a single point, all underlying machines are talking to a central point
Hub-and-Spoke Topology - similar to star but with WAN links instead of LAN connections and it is used for connecting multiple sites
Full-Mesh Topology - optimal routing is always available as every node connects to every other node, it has full redundancy
Partial Mesh Topology - hybrid of the full-mesh and the hub-and-spoke topologies, using this will result into optimal routing
9. Wireless Network Topology (OBJ. 1.2)
Modes of Wireless Networks
Infrastructure Mode - uses a wireless access point as a central point and supports wireless security controls
Ad Hoc Mode - decentralized wireless network which create P2P connections and does not require a router or access point
Wireless Mesh - interconnection of different types of nodes, devices, or radios, redundant and reliable connection
10. Internet of Things (IoT) (OBJ. 1.2)
Internet of Things (IoT) - all devices that connects to internet
802.11 (Wi-Fi) - wireless networks that can operate infrastructure or ad hoc modes
Bluetooth - low-energy use variant of Bluetooth which allows for a mesh network
Radio Frequency Identification (R FID) - uses electromagnetic fields to read data stored in embedded tags
Near Field Communication - enables two devices to communicate within a 4cm range
Infrared (IR) - operates with line of sight
Z-Wave - provides short range, low-latency data transfer with slower rates and less power consumption that WI-FI, lower speed
ANT+ - collection and transfer of sensory data
Quiz 1: Networking Basics
Section 3: OSI Model
11. OSI Model Overview (OBJ. 1.1)
Open System Interconnection (OSI) Model - 1977 by ISO, ISO 7498, OSI Stack
serves as a reference model, used to compare layer and how to troubleshoot a specific problem
12. Layer 1 (Physical Layer) (OBJ. 1.1)
Physical Layer - transmission of bits across the network occurs and includes physical and electrical network characteristics
Bits - binary digits, series of 1s and 0s, basic building blocks of our data
Electrical cables
0V - 0
-5V or +5V - 1
Fiber cables
light on - 1
light off - 0
Transition Modulation - If it changes during clock cycle, 1 is represented otherwise 0
How cables are wired?
RJ45 connector - used to connect to computer or a switch
TIA/EIA-568A
TIA/EIA-568B
How are cables connected?
Topologies - Bus, Star, Ring, Hub-and-Spoke, Full-Mesh, Partial-Mesh
How is communication synchronized?
Synchronous - uses a reference clock (common time source) to coordinate the transmissions by both sender and receiver
e.g. call, same place and the same time , real time
Asynchronous - uses start and stop bits to indicate when transmissions occur from the sender to receiver
e.g. voicemail, you leave a message then they don't answer and they can view it later, out of sync/time
How is bandwidth utilized?
Broadband - divides bandwidth into separate channels
Baseband - uses all available frequencies on a medium (cable) to transmit a data, uses a reference clock
How can we get more out of a limited network?
Multiplexing - getting more out of a limited network, using a baseband at the same time
Time-Division Multiplexing (TDM) - Each session takes a turn, using time slots, to share the medium between all users
Statistical Time-Division Multiplexing (StatTDM) - Dynamically allocates the time slots on an as-needed basis
Frequency-Division Multiplexing (FDM) - divides the medium into channels based on frequencies and each session is transmitted over a different channel
Physical Devices Example
Physical Devices - repeaters, only repeats what they being told, no intelligence, dumb
Cable
Copper
Fiber
Coaxial
Wireless Devices
Bluetooth
Wi-Fi
NFC
Infrastructure Devices
Hubs
Access Points
Media Converters
13. Layer 2 (Data Link Layer) (OBJ. 1.1)
Data Link Layer - Packages data into frames and transmits those frames on a network
Media Access Control (MAC) - physical addressing system of a device which operates on logical topology
Logical Link Control (LLC) - provides connection services and allows acknowledgement of receipt of messages, basic form of flow, provides basic error control functions
if last bit is even (0) = communication is good
if last bit is odd (1) = communication is not good
How communication is synchronized?
Isochronous mode - network devices uses a common reference clock source and create time slots for transmission
Synchronous mode - network devices agree on clocking method to indicate beginning and end of frames and can use control characters, how many beats in a measure
Asynchronous mode - network devices reference their own internal clocks and use start and stop bits
Data Link Devices Example
NIC
Bridges
Switches - intelligent
14. Layer 3 (Network Layer) (OBJ. 1.1)
Network Layer - forwards traffic (routing) with logical address
Logical Addressing
Common Protocols
Internet Protocol (IP)
IPv4
IPv6
Layer 3 Switching (Routing)
How should data be forwarded or routed?
Packet switching - data is divided into packets and forwarded
Circuit switching - dedicated communication link is established between 2 devices
Message switching - data is divided into messages which may be stored and then forwarded
Route Discovery and Selection - manually configured as a static route or dynamically through a routing protocol, how data flow
Bandwidth usage
Connection services - augment layer 2 connection services to improve reliability
Flow control - barrier, stopping the flow of much messages
Packet reordering - divided data into packets and then send randomly to receiver and then fixes the order of packet
Multiplexing strategy
Internet Control Message Protocol (ICMP) - send error messages and operational operation to an IP destination
ping command
traceroute command - to know what routes are up and down
Layer 3 Devices Example
Router
Multi-layer switches - router and a switch
Common Protocols
IPv4, IPv6
ICMP
15. Layer 4 (Transport Layer) (OBJ. 1.1)
Transport Layer - dividing layer of upper and lower layer of OSI model
Segments - data in transport layer
Common Protocols
Transmission Control Protocol (TCP) - connection-oriented protocol that is reliable way to transport segments across the network, always get an acknowledgement
Three-way handshake - establishes connection
Three-way handshake
User Datagram Protocol (UDP) - Connectionless protocol that is unreliable way to transport segments across the network
if drop, user is unaware
good for audio and video streaming
Windowing - allows client to adjust amount of data in each segment, data flow control
speeds up and slows down to keep up
send less data with increased retransmissions
send more data with decreased retransmissions
Buffering - devices allocate memory to store segments if bandwidth isn't readily available
store for the mean time and then spit out the information when they are available
Layer 4 Devices Example
TCP
UDP
WAN Accelerators
Load Balancers
Firewalls
16. Layer 5 (Session Layer) (OBJ. 1.1)
Session Layer - keeps conversations separate to prevent intermingling of data
Steps of a session
Set up - checking of user credentials and assigning numbers to sessions to identify them
Maintain - maintain the session over and over again
Transfer data
Re-establish connection - maintaining
Acknowledgement of receipt - confirmation of data
Tear down - ending of a session after the transfer is done or when the other party disconnects
Layer 5 Devices Example
H.323/H.264 - setup, maintain and tear down voice and video connections, over RTP, used in YouTube, Skype and other teleconference apps
NetBIOS - used to share files over a network
17. Layer 6 (Presentation Layer) (OBJ. 1.1)
Presentation Layer - formats the data to be exchanged and secures that data with proper encryption
Data Formatting - data is formatted to have compatibility among devices
ASCII - text, says that A = 65, ensures data is readable by the receiving system, provide proper structures
GIF - pictures with motion
JPEG - photo
PNG - images in internet
Encryption - used to scramble the data in transit to keep it secure from prying eyes and provide data confidentiality
Transport Layer Security (TLS) - used to secure data in computer to web, creates an encrypted tunnel
Layer 6 Devices Example
Scripting Languages
Standard Text
Pictures
Movie Files
Encryption algorithms
TLS
SSL
18. Layer 7 (Application Layer) (OBJ. 1.1)
Application Layer - provides application-level services where users communicate with the computer
Application Services - unites communicating components from more than one network application
Network Management
File Transfer
File Sharing
Remote Access
Client Server Processes
Email
POP3
SMTP
IMAP
Service Advertisements - sending out of announcements to other devices on the network to state the services they offer
device advertises itself to be used by users
Layer 7 Devices Example
Email Applications
POP3
IMAP
SMTP
Web browsing
HTTP/s
Domain Name Service
DNS
File Transfer Protocol
FTP/s
SFTP
Remote Access
SNMP
SSH
Telnet
20. Encapsulation and Decapsulation (OBJ. 1.1)
Encapsulation - process of putting headers (and trailers) around some data
De-encapsulation - removing encapsulation
Protocol Data Unit (PDU) - single unit of information transmitted in a computer network
L7 PDU - Layer and PDU
How they pass data TCP Header - used in TCP, has 20 bytes
Sequence and Acknowledgement Number - ensures all the data is received
TCP Flags
SYN (Synchronization) - used to synchronize connection during three-way handshake
ACK (Acknowledgement) - used in three-way handshake, but also need to acknowledge the successful receipt of packets
FIN (Finished) - used to tear down virtual connections created using three-way handshake and the SYN flag
RST (Reset) - used when client or server receives a packet that is not expecting during a connection, rejecting request
PSH (Push) - used to ensure data is given priority and is processed at the sending or receiving ends
URG (Urgent) - similar to PSH and identifies incoming data as urgent, process it immediately
UDP Header - used in UDP, has 8 bytes
IP Header - used in IP
Ethernet Header - used in layer 2
MAC Address - is a physical address used to identify a network card in a local network
Quiz 2: OSI Model
Section 4: TCP/IP Model
21. TCP/IP Model (OBJ. 1.1)
Network Interface Layer - electrical and physical characteristics, transferring bits, what medium (cable)
Internet Layer - where data is taken and packaged into IP diagrams, connect to internet
IP
ICMP
ARP
Reverse ARP
Transport Layer - Defines the level of service and the status of the connection being used by TCP, UDP, RTP
TCP - connection full
UDP - connectionless
RTP - real-time
Application Layer - dictates how programs are going to interface with the transport layer by conducting session management
HTTP
Telnet
FTP
SSH
SNMP
DNS
SMTP
SSL/TLS
22. Data Transfer Over Networks (OBJ. 1.1)
Port - where data go, logical opening on a system representing a service or application that is listening and waiting for traffic, 0 - 65,535
Well-known/Reserved Ports - 0 - 1023
FTP - 21
HTTP - 80
SMTP - 25
Ephemeral Ports - 1024 - 65,535
IPv4 packet - consists of source address, destination address, IP flags and protocol
23. Ports and Protocols (OBJ. 1.5)
File Transfer Protocol (FTP)
Port 20, 21
Provides insecure file transfers, clear no encryption
Secure Shell (SSH)
Port 22
Provides secure remote control machine using text-based environment, safe and encrypted
Secure File Transfer Protocol (SFTP)
Port 22
Provides secure file transfers, encrypted, using SSH to do file transfer
Telnet
Port 23
Provides insecure remote control using text-based environment, no encryption
Simple Mail Transfer Protocol (SMTP)
Port 25
Provides the ability to send emails over network
Domain Name Service (DNS)
Port 53
Converts domain names to IP address, and IP addresses to names
Dynamic Host Control Protocol (DHCP)
Port 67, 68
Automatically provides network parameters to your clients, such as assigned IP address, subnet mast, default gateway, and the DNS server should they use
Trivial File Transfer Protocol (TFTP)
Port 69
Used for lightweight file transfer method for sending configuration files or network booting of an operating system, stripped version of FTP
Hypertext Transfer Protocol (HTTP)
Port 80
Used for insecure web browsing
Post Office Protocol Version 3 (POP3)
Port 110
Used for receiving incoming emails, uses store and forward communication
Network Time Protocol (NTP)
Port 123
Used to keep accurate time to clients on a network
Network Basic Input/Output System (NetBIOS)
Port 139
Used for file or printer sharing in a Windows network
Internet Mail Application Protocol (IMAP)
Port 143
A newer method of retrieving incoming emails which improves upon the older POP3, keeps synchronized to all of devices
Simple Network Management Protocol (SNMP)
Port 161, 162
Used to collect data about network devices and monitor their status
Lightweight Directory Access Protocol (LDAP)
Port 389
Used to provide directory services to your network, Active Directory in Windows, can store user and groups
Hypertext Transfer Protocol - Secure (HTTPS)
Port 443
Used for secure browsing, using secure tunnel (Secure Socket Layer (SSL) - older / Transport Layer Security (TLS) - newer)
Server Message Block (SMB)
Port 445
Used for Windows file and printer sharing services
System Logging (Syslog)
Port 514
Used to send logging data back to a centralized server
Simple Mail Transfer Protocol Transport Layer Security (SMTP TLS)
Port 587
Secure and encrypted way of sending emails
Lightweight Directory Access Protocol - Secure (LDAPS)
Port 636
Provides secure directory services
Internet Message Access Protocol over SSL (IMAP over SSL)
Port 993
Secure and encrypted way to receive emails
Post Office Protocol Version 3 over SSL (POP3 over SSL)
Port 995
Secure and encrypted way to receive emails
Structured Query Language Protocol (SQL)
Port 1433
Used for communication from a client and a database engine
SQLnet Protocol - Oracle
Port 1521
Used for communication from a client to an Oracle database
MySQL
Port 3306
Used for communication from a client to the MySQL database engine
Remote Desktop Protocol (RDP)
Port 3389
Provides graphical remote control of another client or server, full GUI
Session Initiation Protocol (SIP)
Port 5060, 5061
Used to initiate VoIP and video calls
24. Finding Open Ports (OBJ. 5.3)
Nmap (Network Mapper) - command line that maps the network
used by network technicians and security professionals
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