The Sync field is constant and is the character sequence #96#. As TCP guarantees reliable delivery, there is no CRC or checksum on a packet; this would be a duplication of the error checking abilities of TCP. The purpose of the Sync field is to provide defense against an internal RPC Manager fault, where a partial packet was transmitted. TCP guarantees reliable, atomic delivery of an atomically written sequence of bytes. The Sync field ensures that a non-atomic write (which should not happen) will not cause erroneous action at the receiving RPC Manager.