Definition
TCP/IP is the fundamental protocol stack for data transmission on the Internet and the Internet of Things. It was proposed by DARPA in the 1970s and has evolved into a de facto standard. TCP/IP uses a four-layer model: application layer, transport layer, network layer, and link layer. Core protocols include IP (Internet Protocol, for routing and addressing), TCP (connection-oriented reliable communication), UDP (connectionless), ICMP (control and diagnostics), etc. When IoT devices connect via cellular networks, Wi-Fi, or 6LoWPAN, application data is ultimately carried over TCP/IP and securely transmitted after TLS encryption.
Protocol stack layers and functions
- Application Layer: HTTP/2, MQTT, CoAP, AMQP, DNS, etc., implementing business logic and data formats
- Transport Layer: TCP (three-way handshake, flow control, congestion control, reliable delivery) and UDP (connectionless, low overhead, suitable for real-time and QUIC, etc.)
- Network Layer: IPv4/IPv6 (addressing and routing), ICMP (ping, traceroute), IPsec (optional encryption)
- Link Layer: Ethernet, PPP, cellular air interface (PDCP/RLC), Wi-Fi MAC, etc.
Selection between TCP and UDP
TCP provides reliable, ordered, connection-oriented transmission, suitable for scenarios like file transfer, Web, and MQTT that require data integrity; its congestion control and retransmission mechanisms may increase latency in weak network environments. UDP is connectionless and does not retransmit, suitable for real-time audio and video, sensor reporting, CoAP, and other services that are latency-sensitive and can tolerate occasional packet loss. In IoT scenarios, MQTT over TCP is used for command delivery and reliable reporting, while CoAP over UDP is used for lightweight sensor data.
Typical Use Cases
TCP/IP runs through the entire IoT chain: devices obtain IP addresses via cellular networks (PDP context) and communicate with cloud platforms via TCP/UDP; gateways convert non-IP protocols like Zigbee and BLE to TCP/IP before uploading to the cloud. IPv6 is increasingly important in IoT, solving address exhaustion and supporting stateless address auto-configuration (SLAAC), and adaptation layers like 6LoWPAN enable IPv6 support for low-power wireless networks.
SimtoLink's IoT SIM cards provide devices with cellular network access. After activating the PDP context, devices obtain an IP address and communicate with customer business platforms and cloud servers via TCP/IP. When configuring APNs and selecting communication protocols (TCP/UDP, MQTT/HTTP/CoAP) for customers, SimtoLink considers business latency, reliability, and power consumption requirements, recommends appropriate protocol stack combinations, and assists in troubleshooting TCP/IP layer issues such as IP connectivity, DNS resolution, and firewall policies.