Packet Header

With the proposed protocol negotiation described above, the messages received from the UDT socket can now be encoded/decoded as:

• Flags (1 byte / 8 bits) : Describes how to process the rest of the packet

  • Bits 6-7: Obfuscation (if non-zero then all following bytes are XORed with the key)

    • 00 - no obfuscation

    • 01 - 0x6362726973736574

    • 10 - 0x7362697261726461

    • 11 - 0x72687566666d616e

  • Bit 5: L - Is set if the packet contains a Local Node ID

  • Bit 4: V - Is set if the packet contains an MD5 Verification

• Local Node ID (2 bytes / 16 bits little-endian) : If the “L” bit is set in the flags, the Local Node ID represents the node this was sent from

• MD5 Verification (16 bytes) : If the “V” bit is set in the flags, the Verification represents a hash of the remains of the packet as well as a value specific to the node

• Contents: A collection of SDXF elements, the outermost field of which describes the Packet Type being used for each

Note

I’m increasingly uncertain of the purpose of the “Local Node ID” field and may move to dropping it from all packets