Status-Acknowledge(Ack)

The Status-Acknowledge(Ack) message flows from the node to the application and from the application to the node, and is used with both SSCP and PLU connections.

The following structure shows the message format for all SSCP messages and for PLU messages flowing from the node to the application.

struct Status-Acknowledge(Ack) {
    PTRBFHDR  nxtqptr;
    PTRBFELT  hdreptr;
    CHAR      numelts;
    CHAR      msgtype;
    CHAR      srcl;
    CHAR      srcp;
    INTEGER   srci;
    CHAR      destl;
    CHAR      destp;
    INTEGER   desti;
    CHAR      sfhdr.stackhdr.akstat;
    CHAR      sfhdr.stackhdr.akqual;
    INTEGER   sfhdr.stackhdr.akmsgkey;
    CHAR      sfhdr.stackhdr.akflags1;
    CHAR      sfhdr.stackhdr.akflags2;
    INTEGER   sfhdr.stackhdr.aknumb1;
    INTEGER   sfhdr.stackhdr.aknumb2;
    INTEGER   sfhdr.stackhdr.akseqno;
}; 
 

LUA only (see Remarks):
Element

struct Status-Acknowledge(Ack) {
    PTRBFELT   hdreptr->elteptr;
    INTEGER    hdreptr->startd;
    INTEGER    hdreptr->endd;
    CHAR       hdreptr->trpad;
    CHAR[268]  hdreptr->dataru;
}; 
 

Members

nxtqptr

Pointer to next buffer header.

hdreptr

Pointer to buffer element (NIL if not using LUA).

numelts

Number of buffer elements (0x00 if not using LUA).

msgtype

Message type STATFMI (0x21).

srcl

Source locality.

srcp

Source partner.

srci

Source index.

destl

Destination locality.

destp

Destination partner.

desti

Destination index.

sfhdr.stackhdr.akstat

Status type ACK (0x01).

sfhdr.stackhdr.akqual

Acknowledgment type ACKPOS (0x02).

sfhdr.stackhdr.akmsgkey

Message key.

sfhdr.stackhdr.akflags1

Application flag 1.

sfhdr.stackhdr.akflags2

Application flag 2.

sfhdr.stackhdr.aknumb1

Undefined.

sfhdr.stackhdr.aknumb2

Reserved.

sfhdr.stackhdr.akseqno

SNA sequence number.

LUA only (see Remarks):
Element

hdreptr–>elteptr

Pointer to buffer element (NIL).

hdreptr–>startd

Start of data in this buffer element

13 or
10 for second and subsequent segments of outbound segmented RUs

hdreptr–>endd

End of data in this buffer element.

hdreptr–>trpad

Reserved.

hdreptr–>dataru

Data RU.

The message format for PLU messages flowing from the application to the node is identical to the preceding format, except that the application flag 1 and application flag 2 fields are not used. They are replaced by the following INTEGER field:

sfhdr.stackhdr.akmsgtim

Last host response time

0xFFFF - no response time measured
0xnnnn - last response time measured, in units of 0.1 second

Remarks

• The message key and application flags reflect the message key and application flags of the data message to which this is an acknowledgment (see note on LUA below).
• For outbound Status-Acknowledge(Ack) messages from the local node to the application, the SNA sequence number gives the sequence number of the inbound data message to which this is an acknowledgment (see note on LUA below); it is normally used only by TS profile 4 applications.
• For inbound Status-Acknowledge(Ack) messages from the application to the local node, the SNA sequence number reflects the sequence number of the outbound data message to which this is an acknowledgment.
• If the host specified that response time statistics are to be maintained (see RTM Parameters and Response Time Monitor Data for details), the application is responsible for measuring and reporting response times to the local node, using the akmsgtim field of this message.
• If the application is using the LUA variant of the FMI (see FMI Concepts), the TH and (if appropriate) RH are included in the data, and the startd field points to the TH. The akmsgkey, akflags1, and akflags2 fields are undefined and should not be used; the corresponding data from the element should be used instead. The akseqno field is similarly undefined on messages from the local node to the application; it must be set on messages from the application to the local node. The akseqno field is used to hold the sequence number of the request being acknowledged.
• If the application is not using the LUA variant of the FMI, the message consists of a buffer header only; there is no buffer element.