Overview of Distributed Protocol Interface (DPI) versions 1.1 and 2.0

Two levels of Distributed Protocol Interface (DPI) are supported by z/OS® Communications Server. The following list shows some support differences between the two versions:

Support provided by DPI Version 1.1
- Was supported on earlier releases of TCP/IP and continues to be supported by the SNMP agent; existing subagents written with DPI Version 1.1 still run with no changes required.
- Supports SNMP Version 1 protocols, but not SNMP Version 2.
- Is intended for C socket API users, not z/OS UNIX C socket users.
- Supports connections from subagents using TCP sockets.
- Is documented in RFC 1228.
Support provided by DPI Version 2.0:
- Is supported in TCP/IP z/OS UNIX and above.
- Contains more functions that make writing a subagent easier.
- Supports both SNMP Version 1 and Version 2 protocols.
- Is used by z/OS UNIX C socket users but not standard C socket users.
- Supports connections from subagents using TCP sockets and UNIX Stream sockets.
- Is documented in RFC 1592.

While DPI Version 1.1 can continue to be used by existing subagents, users who are writing new subagents or modifying old ones should consider upgrading to DPI Version 2.0 to take advantage of the SNMP Version 2 protocols and the greater functionality of DPI Version 2.0.

Although the SNMP agent that is included with z/OS Communications Server is now enabled to support SNMP Version 3 (SNMPv3), no changes are required to subagents written with either DPI Version 1.1 or Version 2.0. SNMPv3 did not introduce any new protocol data unit (PDU) types. Support for the SNMPv3 framework is handled by the SNMP agent.

Users of DPI Version 1.1 must compile using the DPI library routines provided in SEZADPIL and the version of the header file, snmp_dpx.h, that is provided in SEZACMAC. When an included header file exists as a member of an MVS™ partitioned data set, the underscore (_) in the header file name is changed to an at sign (@) when the header file is located during the compiling of a program. Therefore, header file snmp_dpx.h can be found as member SNMP@DPX in the SEZACMAC data set. See SNMP agent Distributed Protocol Interface version 1.1 for additional details.

Users of DPI Version 2.0 must compile using the DPI library routines provided in the directory /usr/lpp/tcpip/snmp/build/libdpi20 and the DPI Version 2.0 copy of the header file, snmp_dpi.h in /usr/lpp/tcpip/snmp/include. Additional details are in SNMP agent Distributed Protocol Interface version 2.0.

For information about migrating an existing subagent from DPI Version 1.1 to DPI Version 2.0, see Required actions for migrating your SNMP DPI subagent to Version 2.0.