Express features also helps to reduce network latency using the SMC-R protocol in z/OS V2.1 or later. For more information, see RFC 7609. SMC-R is transparent to applications and can be used for LPAR-to-LPAR communications on a single CPC or for server-to-server communications across multiple IBM Z CPCs. 

SMC-R uses existing IBM Z and industry standard communications technology: 

GLYPH<SM590000> RDMA, which is based on queue pair (QP) technology that also uses an InfiniBand transport service type that is called reliable connected QPs (RC-QPs), which provide these features: 

– Represent SMC Links in a logical point-to-point connection. 

– Transport data over unique RDMA network interface cards (RNICs) that are logically bound together to form Link Groups. Link Groups are used for high availability and load balancing needs. 

Ports in the IBM Z RoCE Express features (also referred to as RNICs) are used as the physical transport layer for RDMA. 

GLYPH<SM590000> Single root I/O virtualization (SR-IOV) is a Peripheral Component Interconnectfi Express (PCIe) standard that define extensions to PCIe specifications. SR-IOV enables sharing of RoCE Express ports between LPARs in the z15. 

For more information about the RoCE Express features and about SMC-R, see the IBM z15 Technical Guide , SG24-8851, and IBM z/OS V2R2 Communications Server TCP/IP Implementation Volume 1 , SG24-8360. 

## Planning for SMC-R configuration 

Deployment of the RoCE Express features is supported in either point-to-point configuration or switched configurations. When planning to deploy RoCE Express features in a switched configuration, the switches must support the following requirements: 

GLYPH<SM590000> Global Pause function frame (as described in the IEEE 802.3x standard) should be enabled 

GLYPH<SM590000> Priority Flow Control (PFC) disabled 

GLYPH<SM590000> No firewalls, no routing 

IBM provides the SMC Applicability Tool (SMCAT) that helps determine the potential gains of using SMC-R in an environment (see 2.6.5, “SMC Applicability Tool” on page 14). 

## RoCE Express features port configuration: 

GLYPH<SM590000> For 10GbE RoCE Express2 and later features, the port number is now configured with the FID number in HCD (or IOCDS) and Port number must  be configured ( there is no default ). 

GLYPH<SM590000> Port number for 10GbE RoCE Express (FC 0411) is configured in z/OS TCP/IP profile and does not change. 

When defining a FID in the TCP/IP profile for 10GbE RoCE Express2 or later features, the port number is no longer applicable. 

When preparing to deploy the RoCE Express features, consider the following items: 

GLYPH<SM590000> The RoCE Express features are “Native” PCIe features, so the following configuration items must be provided: 

– Function ID 

– Type 

