Inside Macintosh: Networking /

Chapter 6 - AppleTalk Transaction Protocol (ATP) / About ATP

ATP Flags

Many of the functions that you use for an ATP transaction pass control information in an ATP parameter block field called atpFlags. This field comprises a single byte whose bits you can set to signal control information, if appropriate. In some cases, ATP sets these flag bits for its own use. The discussion of each function that uses these flags includes the control information about the bits specific to that function. Table 6-1 shows the Pascal and assembly constants defined for these bits.

Table 6-1 Constants for ATP flag bits

Bit	Pascal constant	Assembly constant	Meaning
0	atpSendChkvalue	sendChk	Use DDP's checksum feature when sending a packet.
1	atpTIDValidvalue	tidValid	The transaction ID value that ATP assigns is set; you can check the reqTID field now.
2	None	atpXcall	This exactly-once transaction request uses an extended parameter block, the last field of which (TRelTime) is set to the release timer value for the ATP responder side.
3	atpSTSvalue	atpSTSBit	The ATP requester must retransmit a request immediately. (ATP sets the send-transmission- status bit, which it uses internally.)
4	atpEOMvalue	atpEOMBit	The last packet in this response is the end of the message.
5	atpXOvalue	atpXOBit	This request is an exactly-once transaction.