TCP/IP
✅ What is TCP/IP?
TCP/IP (Transmission Control Protocol/Internet Protocol) is the fundamental suite of communication protocols that allows computers to communicate over the Internet and other networks.
It is a set of rules (protocols) that dictate how data should be packaged, addressed, transmitted, routed, and received.
🌐 Why is TCP/IP Important?
Foundation of the Internet and local networks.
Ensures reliable data transfer between devices.
Used by nearly all modern networks for email, websites, file sharing, etc.
🔑 Key Components of TCP/IP:
Application Layer
User interaction, services
HTTP, HTTPS, FTP, SMTP, DNS
Transport Layer
End-to-end connection, data reliability
TCP, UDP
Internet Layer
Logical addressing and routing
IP, ICMP, ARP
Network Access Layer
Physical transmission of data (hardware, drivers)
Ethernet, Wi-Fi, PPP
📊 TCP vs. IP - Explained Simply:
Function
Ensures reliable delivery, error checking
Addresses and routes packets
Role
Splits data into packets, ensures they arrive
Assigns IP addresses, handles packet delivery
Connection Type
Connection-oriented (requires handshake)
Connectionless
Reliable?
✅ Yes (retransmits lost packets)
❌ No (best effort delivery)
Used for
Web browsing, email, file transfer
Routing packets to correct destination
⚙️ How TCP/IP Works (Step by Step):
Data Creation: User sends data (e.g., opening a website).
TCP Segment: TCP divides data into packets and adds sequence numbers for ordering and error correction.
IP Packet: Each TCP packet is wrapped in an IP packet, which contains source and destination IP addresses.
Physical Transmission: Data is sent over the network (Ethernet, Wi-Fi).
Routing: Routers forward the packets to the destination.
Reassembly: TCP on the receiving end reassembles packets and checks for errors.
Delivery to Application: Data is passed to the correct application (browser, email client).
💡 TCP/IP Model vs. OSI Model:
Application
Application
Presentation
Application
Session
Application
Transport
Transport
Network
Internet
Data Link
Network Access
Physical
Network Access
🔑 Note: TCP/IP combines some OSI layers for simplicity.
🚀 Common TCP/IP Protocols by Layer:
Application
HTTP, HTTPS, FTP, SMTP, POP3, IMAP, DNS
Transport
TCP, UDP
Internet
IP (IPv4, IPv6), ICMP, ARP
Network Access
Ethernet, Wi-Fi, PPP
🔐 Important Concepts in TCP/IP:
IP Address
Unique identifier for a device on a network
Port Number
Identifies specific application or service
Packet
Small unit of data transferred over a network
Routing
Determining the path packets take to reach destination
Subnet Mask
Defines network and host portions of an IP address
DNS
Domain Name System, resolves names to IP addresses
Gateway
Device (router) that connects local network to outside networks
🧭 IP Address Example:
IPv4 Address
192.168.1.10
Subnet Mask
255.255.255.0
Default Gateway
192.168.1.1
DNS Server
8.8.8.8 (Google DNS)
📡 TCP Three-Way Handshake (Connection Setup):
1
SYN (Synchronize, request connection)
2
SYN-ACK (Acknowledge and reply)
3
ACK (Acknowledge response)
✅ After the handshake, data transmission begins.
✅ Summary Table:
Full Form
Transmission Control Protocol / Internet Protocol
Purpose
Networking and communication protocols
Layers
4 (Application, Transport, Internet, Network Access)
Transport Protocols
TCP, UDP
Addressing
IP addresses (IPv4, IPv6)
Reliability
Ensured by TCP
Connection Type (TCP)
Connection-oriented
Common Ports
80 (HTTP), 443 (HTTPS), 21 (FTP), 25 (SMTP), 53 (DNS)
📖 Real-life Example:
➡️ When you visit https://example.com:
DNS resolves "example.com" to an IP address.
Your browser uses TCP/IP to create a connection to that IP address on port 443 (HTTPS).
Data is transferred via TCP/IP stack.
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