APRS-q-msg.txt

The "q-construct" is implemented on APRS-IS to add the following capabilities to the Internet APRS transport mechanism.

APRS-IS Entry Identification
Support for a Future Authorization Algorithm
Support for Loop Detection
Support for Automatic Loop Protection
Compatibility with Existing IGate and Client Software
Only Server Support Needed for Implementation
The currently defined q constructs are:

Server Generated:

qAC - Packet was received from the client directly via a verified connection (FROMCALL=login). The callSSID following the qAC is the server's callsign-SSID.
qAX - Packet was received from the client directly via a unverified connection (FROMCALL=login). The callSSID following the qAX is the server's callsign-SSID. This construct is in addition to the TCPIP*/TCPXX* construct currently in place. TCPXX and qAX have been depricated on APRS-IS.
qAU - Packet was received from the client directly via a UDP connection. The callSSID following the qAU is the server's callsign-SSID.
qAo - (letter O) Packet was received via a client-only port, the FROMCALL does not match the login, and the packet contains either a ,I or qAR construct where the indicated IGate matches the login.
qAO - (letter O) Packet was received via a client-only port and the FROMCALL does not match the login.
qAS - Packet was received from another server or generated by this server. The latter case would be for a beacon generated by the server. Due to the virtual nature of APRS-IS, use of beacon packets by servers is strongly discouraged. The callSSID following the qAS is the login or IP address of the first identifiable server (see algorithm).
qAr - Packet was received indirectly (via an intermediate server) from an IGate using the ,I construct. The callSSID following the qAr it the callSSID of the IGate.
qAR - Packet was received directly (via a verified connection) from an IGate using the ,I construct. The callSSID following the qAR it the callSSID of the IGate.

Client Generated:

qAR - Packet is placed on APRS-IS by an IGate from RF. The callSSID following the qAR is the callSSID of the IGate.
qAO - (letter O) Packet is placed on APRS-IS by a receive-only IGate from RF. The callSSID following the qAO is the callSSID of the IGate. Note that receive-only IGates are discouraged on standard APRS frequencies. Please consider a bidirectional IGate that only gates to RF messages for stations heard directly.
qAZ - Packet is generated by the server/client/IGate and should not be propagated. The callSSID following the qAZ is the callSSID of the server/client/IGate. This is normally used for connection messages such as messages to USERLIST.
qAI - Trace packet. This packet tells each server to add login identification to the packet. This packet starts with the callSSID of the originating station following the qAI. See algorithm for more details.