Marking Records in RPC Messages

When RPC messages are passed using the TCP/IP byte-stream protocol for data transport, it is important to identify the end of one message and the start of the next one. This is called record marking (RM).

A record is composed of one or more record fragments. A record fragment is a four-byte header, followed by 0 to 232 -1 bytes of fragment data. The bytes encode an unsigned binary number, similar to XDR integers, in which the order of bytes is from highest to lowest. This binary number encodes a Boolean and an unsigned binary value of 31 bits.

The Boolean value is the highest-order bit of the header. A Boolean value of 1 indicates the last fragment of the record. The unsigned binary value is the length, in bytes, of the data fragment.