LAN SDN hard core technology insider 24 outlook for the future - RDMA (middle)

yesterday , We Yes RDMA A basic introduction to the mechanism of .

RDMA The essence of , For large-scale distributed computing storage , Let the network card bypass CPU, Cooperate with remote server to directly access memory , Accelerate the interaction between servers , Reduce delay , Put the precious CPU Resources are used for high-value computing and logical control .

Let's review this picture again ：

You can see that ,RDMA It is different from the channel of the network . This is because , In the early ,RDMA It cannot be hosted on the Ethernet , We need to rely on a method called Infiniband Network technology .

Infiniband Literally, it means “ Infinite bandwidth ”. It is based on the credit token mechanism , Only the downstream receiving end has processed the packet , Free cache resources , Send the token to the upstream sender , The upstream sender can send the next packet . This can ensure that the transmission of data packets is reliable , No packet loss due to congestion .

Students who are familiar with early network technology must realize , This sum 802.5 Token Ring The mechanism is very similar , Also has the Token Ring The same flaw in the mechanism —— The high cost .

in fact , because Infiniband The reasons of technology in terms of cost and openness , At present, only Mellanox One supplier provides complete Infiniband Solution , This has to be expected to make use of Infiniband Technology for large-scale RDMA Networking users have doubts .

therefore , Ethernet based RoCE (RDMA Over Converged Ethernet) technology , from 2018 Popular since . It can use Ethernet card RDMA.Intel And Mellanox All mainstream Ethernet cards support this technology .

RoCE There are two versions ：RoCE v1 and RoCE v2.

RoCE v1 It is via Ethernet 0x8915 Type identification , in other words , It is not IP agreement . This makes RoCE It can only be applied in a small range .

To address this limitation , The engineers worked out RoCE v2. It is associated with RoCE v1 Not compatible , But the use of UDP port 4791 To communicate . This makes RoCE It can traverse the layer 3 switch 、 Router or firewall , Greatly improved RoCE Application scope of .

that , Does it only need network card support RoCE, You can run efficiently on the Ethernet RDMA Well ？

Tomorrow, , We will answer this question for you .