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.

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🌐 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.

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🔑 Key Components of TCP/IP:

Layer	Description	Protocol Examples
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

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📊 TCP vs. IP - Explained Simply:

Aspect	TCP (Transmission Control Protocol)	IP (Internet Protocol)
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

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⚙️ How TCP/IP Works (Step by Step):

1. Data Creation: User sends data (e.g., opening a website).

2. TCP Segment: TCP divides data into packets and adds sequence numbers for ordering and error correction.

3. IP Packet: Each TCP packet is wrapped in an IP packet, which contains source and destination IP addresses.

4. Physical Transmission: Data is sent over the network (Ethernet, Wi-Fi).

5. Routing: Routers forward the packets to the destination.

6. Reassembly: TCP on the receiving end reassembles packets and checks for errors.

7. Delivery to Application: Data is passed to the correct application (browser, email client).

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💡 TCP/IP Model vs. OSI Model:

OSI Layer	TCP/IP Layer
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.

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🚀 Common TCP/IP Protocols by Layer:

Layer	Protocols
Application	HTTP, HTTPS, FTP, SMTP, POP3, IMAP, DNS
Transport	TCP, UDP
Internet	IP (IPv4, IPv6), ICMP, ARP
Network Access	Ethernet, Wi-Fi, PPP

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🔐 Important Concepts in TCP/IP:

Concept	Description
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

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🧭 IP Address Example:

Term	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)

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📡 TCP Three-Way Handshake (Connection Setup):

Step	Sender (Client)	Receiver (Server)
1	SYN (Synchronize, request connection)
2		SYN-ACK (Acknowledge and reply)
3	ACK (Acknowledge response)

✅ After the handshake, data transmission begins.

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✅ Summary Table:

Feature	TCP/IP
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)

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📖 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.