Overview
Benefits
- More deterministic performance, i.e. reducing jitter and latency inconsistency
- Decreased CPU utilization
- Higher packets per second (pps) on the datapath
Latency improvement is very minimal when you communicate across virtual networks or connect to on-premises and the Internet, so we omit that from the list.
Limitations
- The Azure platform does not update the Mellanox NIC drivers in the VM. The driver is known to have bugs on old kernels.
Technical Details
Azure SmartNIC
Based on FPGAs, AccelNet offloads packet forwarding to SmartNIC hardware with Generic Flow Tables. GFT is a match-action language that defines specific operations on packets for one specific network flow.
If GFT does not match a given packet, the SmartNIC hardware will send the packet to the software layer (VFP) as an Exception Packet, which are most common on the first packet of each flow. After the first packet of each flow, all forwarding can be offloaded, providing the full performance of a native SR-IOV hardware solution.
Serviceability
AccelNet is transparent to user space applications via NetVSC service in VM, which switches I/O back to synthetic vNICs during a service event to maintain connectivity.
Supported VM instances
See Linux VM sizes, where each “series” has its own page describing Accelerated Networking support among other information.
Accelerated Networking is required and turned on by default on some series, including all v5 and above Intel processor general purpose sizes.
Other Networking Acceleration Mechanisms on Azure
- Receive Segment Coalescing
- The next-generation MANA