Two rapidly evolving and merging technologies are the Internet and wireless data communications. Another trend is the increased use of real-time multimedia applications for audio and video communication. The most popular transport protocol among these delay sensitive applications is UDP (user datagram protocol), which is a lightweight protocol that provides multiplexing among user processes and has low protocol processing overhead. UDP's checksum policy is to protect either an entire packet including UDP and IP headers or nothing in the packet at all. This conforms badly with applications that prefers errors in the payload to the loss of whole packets. Many real-time applications fall into this category. We present a new protocol, UDP Lite, that provides the kind of protection often needed by these real time applications especially when they are run over wireless networks. UDP Lite increases the flexibility of UDP by providing an optionally partial checksum. Each packet can be optionally divided into a sensitive and an insensitive part by the sender. Errors in the sensitive part will cause packets to be discarded by the UDP Lite receiver, while errors in the insensitive part are ignored by UDP Lite. We show how UDP Lite uses a wireless network more efficiently for two different scenarios. By combining UDP Lite with compressed RTP, the gain can be even higher. Simulations show that the error rate of the network can increase by almost an order of magnitude without increasing the packet loss ratio. This enables cheaper network solutions for applications such as IP telephony