For UDP messages, Ice uses two additional properties, Ice.UDP.SndSize and Ice.UDP.RcvSize. (Note that the value of these properties is in bytes, not kilobytes.) These properties determine the maximum size for the sending and receipt of UDP messages. The default value depends on your operating system. (Typical defaults are 64kB on Windows, and 8kB on Linux.) The maximum sensible value for these properties is 65535 (64kB). You can set them to larger values, but doing so merely increases the size of the kernel buffers and does not affect the hard limit of 65507 bytes for the payload of a UDP packet. (It follows that, for UDP, the maximum Ice message size, including protocol overhead, is 65507 bytes because that is the limit imposed by UDP.) If you set Ice.MessageSizeMax in addition to the UDP send/receive size, the smaller of the property settings applies.