NetIPC 3000/XL Programmer's Reference Manual (5958-8600)

34 Chapter1
NetIPC Fundamentals
Direct Access to Level 3 (X.25)
Direct Access to Level 3 (X.25)
Features
The following features of direct access to level 3 (X.25) with NetIPC are
described in this section:
• Supports switched virtual circuits (SVCs) and permanent virtual
circuits (PVCs).
• Provides access to the call user data (CUD) field in call packets.
• Provides access to X.25 addresses in call packets.
• Creation of a catch-all socket which can be used to accept data
packets with no CUD or unrecognized CUD.
• Provides ability to send up to 128 bytes of call user data using the
fast select facility.
• Provides ability to append, generate and examine the facility field in
call packets.
• Provides access to X.25 protocol features.
• Allows direct specification of the target X.25 address or PVC
number.
Limitations
Limitations using direct access to level 3 (X.25) are:
• Intranet use only (level 4 provides internet and intranet
connections)
• One virtual connection socket accesses one X.25 virtual circuit for
data transfers over X.25. Multiplexing of connections over a virtual
circuit is not supported.
• IPCNAME, IPCNAMERASE and IPCLOOKUP are not supported.
Switched Virtual Circuits (SVCs)
Switched virtual circuits are defined as a logical association that only
exists as long as the connection does. Both processes create their own
local call sockets using IPCCREATE that can be associated with protocol
relative addresses. To establish a connection with a specific server
process, a request process must include a server protocol relative
address in the IPCDEST intrinsic. Alternatively, an
opt parameter in
IPCCREATE can be used to create a catch-all socket where any incoming