differs from the packet format shown here for illustration in fig3 a packet 300 is shown with various data fields from the physical and transport layers of the rapid i o protocol starting with the first of these fields field 302 is the ackid or acknowledgment id field which is a five bit number that distinguishes packet 300 from other packets when a packet is received the receiver stands an acknowledgment having an ackid field that matches the ackid field of the packet field 304 consists of three bits of reserved space set to zero field 306 is a 2 bit number that represents the priority of packet 300 and as compared to other packets being transmitted over the same connection field 308 the tt field indicates a type of transport address mechanism used and is just used by the transport layer of the rapid i o framework ftype field 310 is a 4 bit field that represents the type of transaction to which packet 300 pertains either as a request packet or a response packet the remaining packet fields 312 which all belong to the transport and logical layers follow ftype field 310 and have a size that is a multiple of 16 bits the last data field in packet 300 crc field 314 is a 16 bit cyclic redundancy check the value that is used to detect errors in transmission or reception of packet 300 specifically the 16 bit crc that is used is based on the itu polynomial x 16 x 12 x 5 1 fig3 b is a diagram of a command symbol 315 as used in a preferred embodiment of the present invention command symbol 315.