RDMA over Converged Ethernet

The advantages of RDMA over other network application programming interfaces such as Berkeley sockets are lower latency, lower CPU load and higher bandwidth.

[4] Although in general the delivery order of UDP packets is not guaranteed, the RoCEv2 specification requires that packets with the same UDP source port and the same destination address must not be reordered.

[4] In addition, RoCEv2 defines a congestion control mechanism that uses the IP ECN bits for marking and CNP[13] frames for the acknowledgment notification.

RoCE was expected to bring InfiniBand applications, which are predominantly based on clusters, onto a common Ethernet converged fabric.

[16] Others expected that InfiniBand will keep offering a higher bandwidth and lower latency than what is possible over Ethernet.

The memory requirements of a large number of connections along with TCP's flow and reliability controls lead to scalability and performance issues when using iWARP in large-scale datacenters and for large-scale applications (i.e., large-scale enterprises, cloud computing, web 2.0 applications etc.[21]).

One solution is to use converged Ethernet switches to make the local area network reliable.

This requires converged Ethernet support on all the switches in the local area network and prevents RoCEv2 packets from traveling through a wide area network such as the internet which is not reliable.

[25] Other vendors involved in the network industry provide support for both protocols such as Marvell, Microsoft, Linux and Kazan.