Networking Basics: TCP/IP and Topologies

• A network is a group of two or more computer systems linked together
• It allows computers to communicate, share resources, and access information

TCP/IP

• TCP/IP is a suite of communication protocols used to interconnect network devices on the internet
• TCP stands for Transmission Control Protocol
  • It handles reliable data transfer between two points
  • It breaks data into packets, ensures correct order, and retransmits lost packets
• IP stands for Internet Protocol
  • It handles addressing and routing of data packets
  • It assigns each device an IP address and routes packets across networks

Network Topology

• Network topology refers to the arrangement of devices and connections in a network
• Bus Topology
  • All devices connect to a single cable, called the bus
  • Simple and inexpensive, but a break in the cable disrupts the entire network
• Star Topology
  • All devices connect to a central hub or switch
  • Easy to troubleshoot, but the central hub is a single point of failure
• Ring Topology
  • Each device connects to two other devices, forming a ring
  • Data travels in one direction
  • Failure of one device can disrupt the entire network
• Mesh Topology
  • Each device connects to many other devices
  • Highly redundant and fault-tolerant, but expensive to implement
• Tree Topology
  • Combines features of bus and star topologies
  • Hierarchical structure
  • Easy to expand, but failure of the root node can disrupt the network

OSI Model

• The OSI (Open Systems Interconnection) model is a conceptual framework that standardizes the functions of a telecommunication or computing system into seven abstraction layers
• Layer 7: Application
  • Provides network services to applications, such as email, file transfer, and web browsing
  • Protocols include HTTP, FTP, SMTP, DNS
• Layer 6: Presentation
  • Handles data representation, encryption, and decryption
  • Ensures data is readable by both communicating systems
  • Protocols include SSL/TLS
• Layer 5: Session
  • Manages connections between applications
  • Establishes, maintains, and terminates sessions
  • Protocols include NetBIOS, SIP
• Layer 4: Transport
  • Provides reliable data transfer between end points
  • Handles segmentation, error control, and flow control
  • Protocols include TCP and UDP
• Layer 3: Network
  • Handles routing of data packets across networks
  • Assigns logical addresses (IP addresses)
  • Protocols include IP, ICMP
• Layer 2: Data Link
  • Provides error-free transmission of data frames between two directly connected nodes
  • Defines MAC addresses and handles media access control
  • Protocols include Ethernet, Wi-Fi
• Layer 1: Physical
  • Defines the physical characteristics of the network, such as cables, connectors, and voltage levels
  • Transmits raw bit streams over the physical medium
  • Protocols include Ethernet, Bluetooth

Network Security

• Network security involves protecting network infrastructure and data from unauthorized access, use, disclosure, disruption, modification, or destruction
• Firewalls
  • Act as a barrier between a trusted network and an untrusted network (e.g., the internet)
  • Control network traffic based on predefined rules
• Intrusion Detection Systems (IDS)
  • Monitors network traffic for suspicious activity
  • Alerts administrators to potential security threats
• Intrusion Prevention Systems (IPS)
  • Similar to IDS, but can also take automated actions to block or prevent attacks
• Virtual Private Networks (VPN)
  • Creates a secure, encrypted connection over a public network
  • Allows remote users to securely access a private network
• Encryption
  • Converts data into an unreadable format
  • Protects data confidentiality during transmission and storage
• Access Control
  • Restricts access to network resources based on user identity and permissions
  • Uses authentication and authorization mechanisms
• Wireless Security
  • Secures wireless networks using protocols like WPA2/WPA3
  • Prevents unauthorized access to the wireless network

Network Protocols

• Network protocols are a set of rules that govern communication between devices on a network
• HTTP (Hypertext Transfer Protocol)
  • Used for transferring web pages and other content over the internet
  • Port 80
• HTTPS (Hypertext Transfer Protocol Secure)
  • A secure version of HTTP that uses encryption to protect data
  • Port 443
• FTP (File Transfer Protocol)
  • Used for transferring files between computers
    • Port 21 (control), Port 20 (data)
• SMTP (Simple Mail Transfer Protocol)
  • Used for sending email
  • Port 25
• POP3 (Post Office Protocol version 3)
  • Used for retrieving email from a server
  • Port 110
• IMAP (Internet Message Access Protocol)
  • Used for retrieving and managing email on a server
  • Port 143
• DNS (Domain Name System)
  • Translates domain names into IP addresses
  • Port 53
• DHCP (Dynamic Host Configuration Protocol)
  • Automatically assigns IP addresses to devices on a network
  • Port 67 (server), Port 68 (client)
• SSH (Secure Shell)
  • Used for secure remote access to a computer
  • Port 22
• Telnet
  • Used for remote access to a computer (unencrypted)
  • Port 23
• TCP (Transmission Control Protocol)
  • Provides reliable, connection-oriented data transfer
• UDP (User Datagram Protocol)
  • Provides unreliable, connectionless data transfer
• ICMP (Internet Control Message Protocol)
  • Used for sending error messages and diagnostic information
  • Used by ping command

Binary, Denary, and Hexadecimal

• These are different number systems used in computing
• Binary
  • Base-2 number system
  • Uses only two digits: 0 and 1
  • Used internally by computers to represent data and instructions
• Denary (Decimal)
  • Base-10 number system
  • Uses ten digits: 0 to 9
  • Used by humans for everyday calculations
• Hexadecimal
  • Base-16 number system
  • Uses sixteen digits: 0 to 9 and A to F (A=10, B=11, C=12, D=13, E=14, F=15)
  • Used for representing binary data in a more compact and human-readable format
  • Commonly used for memory addresses and color codes

Classful Addressing

• Classful addressing is an older IP addressing architecture that divides IP addresses into five classes: A, B, C, D, and E
• Each class defines a range of IP addresses and the number of bits used for network and host identification
• Class A
  • Network bits: 8, Host bits: 24
  • First octet: 1-126
  • Large number of hosts per network
• Class B
  • Network bits: 16, Host bits: 16
  • First octet: 128-191
  • Medium number of hosts per network
• Class C
  • Network bits: 24, Host bits: 8
  • First octet: 192-223
  • Small number of hosts per network
• Class D
  • First octet: 224-239
  • Used for multicast addressing
• Class E
  • First octet: 240-255
  • Reserved for future use
• Classful addressing has been largely replaced by Classless Inter-Domain Routing (CIDR), which allows for more flexible allocation of IP addresses