IBM z13s, Technical Manual

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Appendix D. Shared Memory Communications
491
SMC-D is a “hybrid” solution as shown in Figure D-13:
򐂰 It uses a TCP connection to establish the SMC-D connection.
򐂰
The TCP connection can be either through the OSA adapter or IQD HiperSockets
򐂰 A TCP option (SMCD) controls switching from TCP to “out of band” SMC-D.
򐂰 The SMC-D information is exchanged within the TCP data stream.
򐂰 Socket application data is exchanged through ISM (write operations).
򐂰 The TCP connection remains to control the SMC-D connection.
򐂰 This model preserves many critical existing operational and network management
features of TCP/IP.
Figure D-13 Dynamic transition from TCP to SMC-D by using two OSA-Express adapters
The hybrid model of SMC-D uses these key existing attributes:
򐂰 It follows the standard TCP/IP connection setup.
򐂰
The hybrid model switches to ISM (SMC-D) dynamically.
򐂰 The TCP connection remains active (idle) and is used to control the SMC-D connection.
򐂰
The hybrid model preserves the following critical operational and network management
TCP/IP features:
– Minimal (or zero) IP topology changes
– Compatibility with TCP connection-level load balancers
OSA ISM
TCP
IP
Interface
Sockets
Middleware/Application
z/OS LPAR B
SMC-D
OSA ISM
TCP
IP
Interface
Sockets
Middleware/Application
z/OS LPAR A
SMC-D
TCP connection establishment over IP
IP Network (Ethernet)
ISM VCHID (within System z)
TCP connection transitions to SMC-D allowing application data to be exchanged using Direct
Memory Access (LPAR to LPAR)
Dynamic (in-line) negotiation for SMC-R&SMC-D is initiated by presence of TCP Options
TCP syn flows (with TCP Options
CLC indicating SMC-R+SMC-D capability)
data exchanged using
native PCI operations
(PCI STB)
IBM z13 or z13s
Data exchanged using
native PCI operations
(PCI STB)
OSA and ISM
have the same
PNet ID