Similar to SMC-R, this protocol uses shared memory architectural concepts that eliminate TCP/IP processing in the data path, yet preserve TCP/IP Qualities of Service for connection management purposes. 

Support in select Linux on Z distributions is now provided for Shared Memory Communications over Direct Memory Access (SMC-D). For more information, see this Linux on Z Blogspot web page. 

The supported operating systems are listed in Table 7-8 on page 267 and Table 7-9 on page 269. 

## HiperSockets Completion Queue 

The HiperSockets Completion Queue function is implemented on z15, z14, z13, and z13s. This function is designed to allow HiperSockets to transfer data synchronously (if possible) and asynchronously, if necessary. Therefore, it combines ultra-low latency with more tolerance for traffic peaks. HiperSockets Completion Queue can be especially helpful in burst situations. The supported operating systems are listed in Table 7-8 on page 267 and Table 7-9 on page 269. 

## HiperSockets Virtual Switch Bridge 

The HiperSockets Virtual Switch Bridge is implemented on z15, z14, z13, and z13s. With the HiperSockets Virtual Switch Bridge, z/VM virtual switch is enhanced to transparently bridge a guest virtual machine network connection on a HiperSockets LAN segment. This bridge allows a single HiperSockets guest virtual machine network connection to also directly communicate with the following components: 

GLYPH<SM590000> Other guest virtual machines on the virtual switch 

GLYPH<SM590000> External network hosts through the virtual switch OSA UPLINK port 

The supported operating systems are listed in Table 7-8 on page 267 and Table 7-9 on page 269. 

## HiperSockets Multiple Write Facility 

The HiperSockets Multiple Write Facility allows the streaming of bulk data over a HiperSockets link between two LPARs. Multiple output buffers are supported on a single Signal Adapter (SIGA) write instruction. The key advantage of this enhancement is that it allows the receiving LPAR to process a much larger amount of data per I/O interrupt. This process is transparent to the operating system in the receiving partition. HiperSockets Multiple Write Facility with fewer I/O interrupts is designed to reduce processor utilization of the sending and receiving partitions. 

Support for this function is required by the sending operating system. For more information, see “HiperSockets” on page 194. The supported operating systems are listed in Table 7-8 on page 267. 

## HiperSockets support of IPV6 

IPv6 is expected to be a key element in the future of networking. The IPv6 support for HiperSockets allows compatible implementations between external networks and internal HiperSockets networks. The supported operating systems are listed in Table 7-8 on page 267 and Table 7-9 on page 269. 

