Communications Server for z/OS V1R7 TCP/IP Implementation, Volume 1: Base Functions, Connectivity, and Routing

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