RDMA (Remote Direct Memory Access) enables direct data transfer between devices in a network, and RoCE (RDMA over Converged Ethernet) is a leading implementation of this technology. It improves data transmission with high speed and low latency, making it ideal for high-performance computing and cloud environments.
Definition
As a type of RDMA, RoCE is a network protocol defined in the InfiniBand Trade Association (IBTA) standard, allowing RDMA over converged Ethernet network. Shortly, it can be regarded as the application of RDMA technology in hyper-converged data centers, cloud, storage, and virtualized environments. It possesses all the benefits of RDMA technology and the familiarity of Ethernet. If you want to understand it in depth, you can read this article RDMA over Converged Ethernet Guide | FS Community.
Types
Generally, there are two RDMA over Converged Ethernet versions: RoCE v1 and RoCE v2. It depends on the network adapter or card used.
Retaining the interface, transport layer, and network layer of InfiniBand (IB), the RoCE protocol substitutes the link layer and physical layer of IB with the link layer and network layer of Ethernet. In the link-layer data frame of a RoCE data packet, the Ethertype field value is specified by IEEE as 0x8915, unmistakably identifying it as a RoCE data packet. However, due to the RoCE protocol’s non-adoption of the Ethernet network layer, RoCE data packets lack an IP field. Consequently, routing at the network layer is unfeasible for RoCE data packets, restricting their transmission to routing within a Layer 2 network.
Introducing substantial enhancements, the RoCE v2 protocol builds upon the RoCE protocol’s foundation. It transforms the InfiniBand (IB) network layer utilized by the RoCE protocol by incorporating the Ethernet network layer and a transport layer employing the UDP protocol. It harnesses the DSCP and ECN fields within the IP datagram of the Ethernet network layer for implementing congestion control. This enables RoCE v2 protocol packets to undergo routing, ensuring superior scalability. As it fully supersedes the original RoCE protocol, references to the RoCE protocol generally denote the RoCE v2 protocol, unless explicitly specified as the first generation of RoCE. Also Check- An In-Depth Guide to RoCE v2 Network | FS Community
InfiniBand vs. RoCE
In comparison to InfiniBand, RoCE presents the advantages of increased versatility and relatively lower costs. It not only serves to construct high-performance RDMA networks but also finds utility in traditional Ethernet networks. However, configuring parameters such as Headroom, PFC (Priority-based Flow Control), and ECN (Explicit Congestion Notification) on switches can pose complexity. In extensive deployments, especially those featuring numerous network cards, the overall throughput performance of RoCE networks may exhibit a slight decrease compared to InfiniBand networks. In actual business scenarios, there are major differences between the two in terms of business performance, scale, operation and maintenance. For detailed comparison, please refer to this article InfiniBand vs. RoCE: How to choose a network for AI data center from FS community.
Benefits
RDMA over Converged Ethernet ensures low-latency and high-performance data transmission by providing direct memory access through the network interface. This technology minimizes CPU involvement, optimizing bandwidth and scalability as it enables access to remote switch or server memory without consuming CPU cycles. The zero-copy feature facilitates efficient data transfer to and from remote buffers, contributing to improved latency and throughput with RoCE. Notably, RoCE eliminates the need for new equipment or Ethernet infrastructure replacement, leading to substantial cost savings for companies dealing with massive data volumes.
How FS Can Help
In the fast-evolving landscape of AI data center networks, selecting the right solution is paramount. Drawing on a skilled technical team and vast experience in diverse application scenarios, FS utilizes RoCE to tackle the formidable challenges encountered in High-Performance Computing (HPC).
FS offers a range of products, including NVIDIA® InfiniBand Switches, 100G/200G/400G/800G InfiniBand transceivers and NVIDIA® InfiniBand Adapters, establishing itself as a professional provider of communication and high-speed network system solutions for networks, data centers, and telecom clients.
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