Definition
TCP/IP (Transmission Control Protocol/Internet Protocol) is the foundational communication protocol suite of the internet. Initially developed by the U.S. Department of Defense, it standardizes data transmission across interconnected networks.
Core Protocols
- TCP: Ensures reliable, ordered delivery of data streams via:
- Connection establishment (
SYN,SYN-ACK,ACKhandshake) - Flow control (window scaling)
- Error recovery (retransmission of lost packets).
- IP: Handles logical addressing (IPv4/IPv6) and routing of packets between hosts.
TCP/IP Model Layers
| Layer | Function | Example Protocols |
|---|---|---|
| Application | User-facing services | HTTP, FTP, DNS |
| Transport | End-to-end data integrity | TCP, UDP |
| Internet | Logical addressing & routing | IP, ICMP, ARP |
| Link | Physical data transmission | Ethernet, Wi-Fi (802.11) |
Key Technical Features
- Packet Switching: Data is fragmented into packets with headers (source/dest IP, ports, checksums).
- Stateless IP: Each packet is routed independently; sequencing handled by TCP.
- MTU (Maximum Transmission Unit): Default 1500 bytes (Ethernet), adjustable to avoid fragmentation.
TCP vs. UDP
| Parameter | TCP | UDP |
|---|---|---|
| Reliability | ✅ (Ack/retry) | ❌ (Best-effort) |
| Ordering | ✅ (Sequencing) | ❌ |
| Overhead | High (20B header) | Low (8B header) |
| Use Cases | Web, email | VoIP, gaming |
IPv4 vs. IPv6
- IPv4: 32-bit address (4.3B unique addresses), NAT-dependent.
- IPv6: 128-bit address (3.4×10³⁸ addresses), built-in security (IPsec).
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