Appendix D. Shared Memory Communications 477
A reliable “lossless” Ethernet network fabric (LAN for layer 2 data center network distance)
An RDMA network interface card (RNIC)
Figure D-1 RDMA technology overview
RDMA technology is now available on Ethernet. RoCE uses an existing Ethernet fabric
(switches with Global Pause enabled) and requires advanced Ethernet hardware
(RDMA-capable NICs on the host).
D.2.2 Shared Memory Communications over RDMA
SMC-R is a protocol that allows TCP socket applications to transparently use RDMA.
SMC-R is a “hybrid” solution as shown in Figure D-2 on page 478:
It uses an existing TCP connection to establish the SMC-R connection.
A TCP option (SMCR) controls switching from TCP to “out of band” SMC-R.
The SMC-R information is exchanged within the TCP data stream.
Socket application data is exchanged through RDMA (write operations).
The TCP connection remains to control the SMC-R connection.
This model preserves many critical operational and network management features of
TCP/IP.
Host A
Memory
Host B
Memory
CPU
CPU
Rkey A
Rkey B
AB
RNIC
RNIC
Ethernet Fabric
To Next Page
Loading...
Need help?
General