Chapter 1. Introduction 7
– OSA-Express provides a mechanism for communication called Queued Direct I/O
(QDIO). Although it uses the MPC+ protocol for its control signals, the QDIO interface
is quite different from channel protocols. It uses Direct Memory Access (DMA) to avoid
the overhead associated with channel programs. A partnership between CS for z/OS
IP and the OSA-Express adapter provides compute-intensive functions from the
System z9 or zSeries server to the adapter. Segmentation offload is a feature of
OSA-Express2. This interface is called IP Assist (IPA). Offloading reduces System z9
and zSeries server cycles required for network interfaces and provides an overall
improvement in the OSA-Express environment compared to existing OSA-2 interfaces.
OSA-Express collaborates with CS for z/OS TCP/IP to support Gigabit Ethernet,
1000BASE-T, Fast Ethernet, Fast Token-Ring, and ATM LAN emulation.
– HiperSockets (Internal Queued Direct I/O, iQDIO) provides high-speed, low-latency IP
message passing between Logical Partitions (LPARs) within a single System z9 or
zSeries server. The communication is through processor system memory via Direct
Memory Access (DMA). The virtual servers that are connected via HiperSockets form a
virtual LAN. HiperSockets uses internal QDIO at memory speeds to pass traffic
between virtual servers.
Cross-System Coupling Facility (XCF)
XCF allows communication between multiple CS for z/OS IP stacks within a Parallel Sysplex.
The XCF DLC can be defined, as with traditional DLCs, but it also supports XCF Dynamics, in
which the XCF links are brought up automatically.
If DYNAMICXCF is coded, z/OS images within the same server will use the HiperSockets
DYNAMICXCF connectivity instead of the standard XCF connectivity for data transfer.
For more information about devices and connectivity options refer to Chapter 4, “Connectivity”
on page 101.
1.3.4 Supported routing applications
z/OS Communications Server ships two routing applications, OrouteD and OMPROUTE. CS
for z/OS IP V1R7 is the last release to support OrouteD.
OMPROUTE implements the Open Shortest Path First protocols (OSPF and OSPVFv3) and
Routing Information Protocols (RIPv1, RIPv2, RIPng). It enables the CS for z/OS IP to
function as an OSPF/RIP-capable router in a TCP/IP network. Either (or both) of these two
routing protocols can be used to dynamically maintain the host routing table. Additionally, CS
for z/OS IP provides an OMPROUTE subagent that implements the OSPF MIB variable
containing OSPF protocol and state information for SNMP. This MIB variable is defined in
RFC 1850. Refer to Chapter 5, “Routing” on page 139, for a detailed discussion on
OMPROUTE and its function within the CS for z/OS IP environment.
1.3.5 Application programming interfaces
As Figure 1-1 on page 5 illustrates, all of the APIs provided by CS for z/OS IP, with the
exception of the PASCAL API, interface with the Logical File System (LFS) layer. The APIs
are divided into the following categories:
? Pascal
? TCP/IP socket APIs
? z/OS UNIX APIs
8 Communications Server for z/OS V1R7 TCP/IP Implementation, Volume 1 - Base Functions, Connectivity, and Routing
Pascal API
The Pascal application programming interface enables you to develop TCP/IP applications in
Pascal language. Supported environments are normal MVS address spaces. Unlike the other
APIs, the Pascal API does not interface directly with the LFS. It uses an internal interface to
communicate with the TCP/IP protocol stack. The Pascal API only supports AF_INET.
TCP/IP socket APIs
The z/OS V1R7 Communications Server provides several APIs to access TCP/IP sockets.
These APIs can be used in either or both integrated and common INET PFS configurations.
In a common INET PFS configuration, however, they function differently from z/OS UNIX
APIs. In this type of configuration, the z/OS Communications Server APIs always bind to a
single PFS transport provider, and the transport provider must be the TCP/IP stack provided
by the z/OS V1R7 Communications Server. The following TCP/IP socket APIs are included in
the z/OS V1R7 Communications Server:
? The CICS socket interface enables you to write CICS applications that act as clients or
servers in a TCP/IP-based network. CICS sockets only support AF_INET.
? The C sockets interface supports socket function calls that can be invoked from C
programs. However, note that for C application development, IBM recommends the use of
the UNIX C sockets interface. These programs can be ported between MVS and most
UNIX environments relatively easily if the program does not use any other MVS-specific
services. C sockets only support AF_INET.
? The Information Management System (IMS) IPv4 socket interface supports client/server
applications in which one part of the application executes on a TCP/IP-connected host
and the other part executes as an IMS application program. The IMS sockets API
supports AF_INET.
? The Sockets Extended macro API is a generalized assembler macro-based interface to
sockets programming. The Sockets Extended macro API supports AF_INET and
AF_INET6.
? The Sockets Extended Call Instruction API is a generalized call-based, high-level
language interface to sockets programming. The Sockets Extended Call Instruction API
supports AF_INET and AF_INET6.
z/OS UNIX APIs
The following APIs are provided by the z/OS UNIX element of z/OS and are supported by the
TCP/IP stack in the z/OS V1R7 Communications Server:
? z/OS UNIX C sockets is used in the z/OS UNIX environment. It is the z/OS UNIX version
of the native MVS C sockets programming interface. Programmers use this API to create
applications that conform to the POSIX or XPG4 standard (a UNIX specification). The
z/OS UNIX C sockets support AF_INET and AF_INET6.
? z/OS UNIX assembler callable services is a generalized call-based, high-level language
interface to z/OS UNIX sockets programming. The z/OS UNIX assembler callable services
support AF_INET and AF_INET6.
Refer to the z/OS V1R7.0 XL C/C++ Compiler and Run-Time Migration Guide for the
Application Programmer CBCMG140 06/28/05 16:05:01, GC09-4913-03, for complete
documentation of the z/OS UNIX C sockets APIs and refer to z/OS V1R7.0 UNIX System
Services Programming Tools BPXZA640 05/03/05 16:19:37, SA22-7805-04 .
REXX sockets
The REXX sockets programming interface implements facilities for socket communication
directly from REXX programs by using an address rxsocket function. REXX socket programs
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