TCP/IP Model

• TCP/IP is a suite of communication protocols for interconnecting network devices on the internet
• TCP/IP provides end-to-end communications on data exchange over the internet, that identifies the method it should be broken into packets, addressed, transmitted, routed, and received at the destination

Layers of the TCP/IP Model

• The TCP/IP model has four layers: Application, Transport, Internet, and Network Access
• The Application Layer represents the network applications' data
• Protocols in the application layer include HTTP, FTP, SMTP, and DNS
• The Transport Layer handles reliable communication between applications
• TCP and UDP are the transport layer's main protocols, providing connection-oriented and connectionless services
• The Internet Layer is responsible for addressing, routing, and packaging data packets
• IP (Internet Protocol) is the primary protocol used at the Internet Layer
• The Network Access Layer (or Link Layer) handles the physical transmission of data
• Protocols like Ethernet and Wi-Fi operate at the Network Access Layer

TCP (Transmission Control Protocol)

• TCP is a connection-oriented protocol
• TCP provides delivery of data packets that is reliable, ordered, and error-checked
• TCP establishes a connection before data transfer using a three-way handshake: SYN, SYN-ACK, and ACK
• TCP uses sequence numbers and acknowledgments to ensure reliable data delivery
• TCP includes flow control mechanisms to prevent overwhelming the receiver, for example, sliding window
• TCP provides congestion control to avoid network congestion, examples of this are slow start and congestion avoidance

IP (Internet Protocol)

• IP is a connectionless protocol handling addressing and routing packets between networks
• IPv4 uses 32-bit addresses, while IPv6 uses 128-bit addresses
• IP packets have a header containing source and destination IP addresses, TTL (Time To Live), and other control information
• IP performs fragmentation and reassembly of packets if the data exceeds the MTU (Maximum Transmission Unit) of a network

UDP (User Datagram Protocol)

• UDP is a connectionless protocol
• Through UDP, a simple, unreliable data transfer service is provided
• UDP does not guarantee delivery, order, or error checking
• UDP is useful for applications where speed is more important than reliability, such as streaming media and online gaming
• UDP has a smaller header overhead compared to TCP, resulting in faster speeds
• UDP is often used for multicasting and broadcasting

IP Addressing

• An IP address is a unique identifier assigned to each device on a network
• IPv4 addresses are 32-bit numeric addresses, typically written in dotted decimal notation: 192.168.1.1
• IPv6 addresses are 128-bit alphanumeric addresses, written in hexadecimal notation: 2001:0db8:85a3:0000:0000:8a2e:0370:7334
• IP addresses are divided into network and host portions
• Subnet masks determine the network portion of an IP address, for example: 255.255.255.0
• CIDR (Classless Inter-Domain Routing) notation specifies the number of bits used for the network portion of an address, for example: 192.168.1.0/24
• Private IP addresses are used for internal networks and are not routable on the public internet, for example: 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16
• Public IP addresses are used for devices that need to communicate directly over the internet

Ports

• Ports are virtual points where network connections start and end
• Ports allow multiple applications to use the same IP address simultaneously
• Port numbers are 16-bit integers, ranging from 0 to 65535
• Well-known ports (0-1023) are reserved for common services, such as HTTP (80), HTTPS (443), FTP (21), SMTP (25), and DNS (53)
• Registered ports (1024-49151) can be used by applications
• Dynamic or private ports (49152-65535) are used for temporary connections

Subnetting

• Subnetting divides a network into smaller subnetworks or subnets
• Subnetting improves network performance, security, and manageability
• Subnetting involves borrowing bits from the host portion of an IP address to create network addresses
• Subnet masks are used to define the boundaries of each subnet
• VLSM (Variable Length Subnet Masking) allows for subnets of different sizes within the same network

Routing

• Routing selects the best path for data packets to travel from source to destination
• Routers are network devices that forward data packets based on their destination IP addresses
• Routing tables contain information about network destinations and the best paths to reach them
• Static routing involves manually configuring routing tables
• Dynamic routing uses routing protocols to automatically learn and update routing tables
• Common routing protocols include RIP, OSPF, EIGRP, and BGP

DNS (Domain Name System)

• DNS translates domain names, for example www.example.com, into IP addresses, for example 192.0.2.1
• DNS uses a hierarchical, distributed database to store domain name information
• DNS servers are organized into a hierarchy of root, top-level domain (TLD), and authoritative name servers
• DNS queries are resolved through a recursive or iterative process
• DNS records include A (Address), CNAME (Canonical Name), MX (Mail Exchange), and NS (Name Server) records

Network Address Translation (NAT)

• NAT maps private IP addresses to public IP addresses
• NAT allows multiple devices on a private network to share a single public IP address
• NAT hides the internal network structure from the outside world, improving security
• NAT can cause issues with applications that require end-to-end connectivity
• PAT (Port Address Translation) or NAT Overload maps multiple private IP addresses to a single public IP address using different port numbers

Network Security

• Firewalls control network traffic and prevent unauthorized access
• Intrusion Detection Systems (IDS) monitor network traffic for malicious activity
• Intrusion Prevention Systems (IPS) automatically block or mitigate detected threats
• VPNs (Virtual Private Networks) create secure, encrypted connections over public networks
• Encryption protocols like SSL/TLS and IPsec are used to protect data in transit
• Regular security updates and patching are essential to protect against vulnerabilities

The TCP/IP model is a suite of communication protocols used to interconnect network devices on the internet. It has four layers: Application, Transport, Internet, and Network Access. Each layer has its own protocols, such as HTTP, TCP, and IP.