The SPXII protocol is a connection-oriented, reliable, sequenced transport protocol. It provides message-level service (for reliability) rather than packet-level service.
SPXII also provides flow control which regulates the speed with which packets are sent and received by both sending and receiving processes.
As a message service, SPXII provides enhanced throughput. This protocol reduces the amount of traffic on the wire by negotiating for large packets and reducing the number of acknowledgments.
Applications using SPXII do not need to determine packet size. The SPXII driver handles packet size for the application.
To enhance reliability, SPXII delays the close of a connection until all queued data is delivered. If a disconnect indication arrives from the remote side of a connection, SPXII attempts to send all remaining unsent packets upstream to the remote side before taking action on the disconnection indication. Similarly, if an application tries to close a connection, SPXII delays the closing of the application endpoint until all data has been sent to the application and acknowledged. If it is not possible to deliver all remaining data within the timeout period (120 seconds), SPXII completes the requested disconnect.
When setting up UnixWare, you may want to turn on SPXII and enter other information such as the maximum number of SPXII connections and sockets for your network.
If you want to be able to log in to UnixWare from a NetWare workstation, you must configure SPXII on UnixWare and enable NVT as well (see the following topic for an overview of NVT).
The NVT2 service establishes terminal connections between DOS workstations and UNIX systems over SPXII.
NVT2 servers advertise remote login service and listen for SPX connection requests on the advertised socket. The NVT client then sends connection requests to the advertised socket.
Since NVT2 uses SPXII and each NVT2 connection requires a server SPXII connection, the maximum allowed SPXII connections which you specify should be at least 100.
With UnixWare, the NVT2 server uses the Service Access Facility (SAF-configured) listener to handle connect requests and the SAP daemon to handle advertising. When NVT2 is turned on, a script registers the SAF listener process on the NVT2 socket and NetWare Protocol Stack Daemon (NPSD) informs the SAP daemon to advertise NVT2.
If SPXII should go down normally, NVT2 will go down and come back up when SPXII comes back up.
If SPXII goes down abnormally (such as a crash), NVT2 will go down and come back up, but the service will remain registered with SAF and will be invalid. In this case, the protocol stacks must be brought back up manually by stopping and restarting the NUC.
This service allows you to make a local printer available to NetWare users by connecting a local UnixWare printer to a NetWare print queue. This service depends on SPXII.