Difference between revisions of "Packet Layout"
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==Header== | ==Header (Packet ID)== | ||
* Byte 0, 4 most significant bits: Packet Information | * Byte 0, 4 most significant bits: Packet Information | ||
** LL_ZERO_CODE_FLAG 0x80 -- Packet data is run length encoded, such that series of 1 to 255 zero bytes are encoded to take 2 bytes. | ** LL_ZERO_CODE_FLAG 0x80 -- Packet data is run length encoded, such that series of 1 to 255 zero bytes are encoded to take 2 bytes. | ||
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** LL_ACK_FLAG 0x10 -- This packet contains appended acks. | ** LL_ACK_FLAG 0x10 -- This packet contains appended acks. | ||
* Byte 0, 4 least significant bits: currently unused | * Byte 0, 4 least significant bits: currently unused | ||
* | * Header and Body are potentially zerocoded for compression | ||
For further explanation of the bits in the header, see [[Messages]] and [[Packet Accounting]] | For further explanation of the bits in the header, see [[Messages]] and [[Packet Accounting]] | ||
Revision as of 17:15, 15 January 2007
Packet Layout Visualization
+-+-+-+-+-------+---------------+---------------+---------------+ |Z|R|R|A| | |E|E|E|C| Packet ID (28 bits) | |R|L|S|K| | +-+-+-+-+-------+---------------+---------------+---------------+ | | : :
Header (Packet ID)
- Byte 0, 4 most significant bits: Packet Information
- LL_ZERO_CODE_FLAG 0x80 -- Packet data is run length encoded, such that series of 1 to 255 zero bytes are encoded to take 2 bytes.
- LL_RELIABLE_FLAG 0x40 -- This packet was sent reliably (implies please ack this packet)
- LL_RESENT_FLAG 0x20 -- This packet is a resend from the source.
- LL_ACK_FLAG 0x10 -- This packet contains appended acks.
- Byte 0, 4 least significant bits: currently unused
- Header and Body are potentially zerocoded for compression
For further explanation of the bits in the header, see Messages and Packet Accounting
Body
- Bytes 4 to 4 + (data length)
- Message number. This is a numeric encoding of the message types defined in the message_template.msg file. It may be 1, 2 or 4 bytes in length, depending on the message frequency (High, Medium, Low or Fixed).
- High frequency messages are assigned (at run time) numbers 0x00 - 0xFE.
- Medium frequency messages are assigned (at run time) numbers 0xFF00 - 0xFFFE.
- Low frequency messages are assigned (at run time) numbers 0xFFFF0000 and up.
- Messages with "Fixed" frequency are really those with fixed message numbers, i.e. the numbers are assigned in the message_template.msg file itself. There are currently 6 of these, 0xFFFFFFFA - 0xFFFFFFFF.
- Message data. This is different for each message type, and is defined in the message_template.msg file.
- Message number. This is a numeric encoding of the message types defined in the message_template.msg file. It may be 1, 2 or 4 bytes in length, depending on the message frequency (High, Medium, Low or Fixed).
Appended Acks
- Bytes n+(data length) thru acks
- Rest of packet is filled with as many acks from previous reliable messages as will fit.
See also: libsecondlife documentation