UDP
NetworkingUDP is a connectionless transport-layer protocol that sends datagrams without establishing a session or guaranteeing delivery, ordering, or duplicate protection. It favors low latency and minimal overhead by avoiding acknowledgments and retransmissions. Applications that can tolerate some packet loss or handle reliability themselves often use UDP, making it common for real-time traffic and simple request-response exchanges.
How It Works
User Datagram Protocol (UDP) operates at the transport layer (Layer 4) and sits on top of IP. Instead of creating a connection like TCP, UDP sends independent packets called datagrams. Each datagram includes source and destination ports, a length field, and a checksum (mandatory in IPv6, optional in IPv4). Because there is no handshake, a sender can transmit immediately, and the receiver processes whatever arrives.
UDP does not provide built-in mechanisms for retransmission, congestion control, or in-order delivery. If packets are lost, duplicated, or arrive out of sequence, the application must decide what to do. Many real-time systems prefer this tradeoff: it is often better to drop late data than to delay everything waiting for missing packets. Some protocols add reliability on top of UDP when needed, such as QUIC (used by HTTP/3), which implements encryption and stream management in user space while still benefiting from UDP traversal through networks.
Why It Matters for Web Hosting
When comparing hosting plans, UDP affects performance, firewalling, and supported services. Many hosting environments allow only TCP ports by default, while game servers, VoIP, streaming, DNS resolvers, and some VPNs require specific UDP ports to be open and properly routed. If your application depends on UDP, evaluate whether the plan offers configurable firewall rules, DDoS filtering that understands UDP floods, and network policies that permit the required port ranges without excessive rate limiting.
Common Use Cases
- DNS queries and responses (port 53)
- Real-time voice and video (VoIP, WebRTC media transport)
- Online gaming and latency-sensitive multiplayer traffic
- Streaming and telemetry where occasional loss is acceptable
- VPN tunneling modes that use UDP for better throughput and NAT traversal
- HTTP/3 traffic via QUIC over UDP (port 443)
UDP vs TCP
TCP is connection-oriented and provides reliable, ordered delivery with congestion control, which suits web pages, file transfers, and databases. UDP is connectionless and does not guarantee delivery or order, which reduces overhead and latency but shifts reliability concerns to the application. In hosting, choose TCP-centric plans for traditional websites and APIs, and ensure UDP support (open ports, routing, and protection) for real-time services, DNS, VPNs, and QUIC-based workloads.