With regards to (~6:01) "congestion control is the responsibility of the sender" and "somehow we have to get the sending nodes to stop sending so fast". Does that not exist in Ethernet/RoCE?
> Link Level Flow Control: InfiniBand uses a credit-based algorithm to guarantee lossless HCA-to-HCA communication. RoCE runs on top of Ethernet. Implementations may require lossless Ethernet network for reaching to performance characteristics similar to InfiniBand. Lossless Ethernet is typically configured via Ethernet flow control or priority flow control (PFC). Configuring a Data center bridging (DCB) Ethernet network can be more complex than configuring an InfiniBand network.[19]
> A sending station (computer or network switch) may be transmitting data faster than the other end of the link can accept it. Using flow control, the receiving station can signal the sender requesting suspension of transmissions until the receiver catches up. Flow control on Ethernet can be implemented at the data link layer.
throw0101c · · focus · HN ↗
> Link Level Flow Control: InfiniBand uses a credit-based algorithm to guarantee lossless HCA-to-HCA communication. RoCE runs on top of Ethernet. Implementations may require lossless Ethernet network for reaching to performance characteristics similar to InfiniBand. Lossless Ethernet is typically configured via Ethernet flow control or priority flow control (PFC). Configuring a Data center bridging (DCB) Ethernet network can be more complex than configuring an InfiniBand network.[19]
* <a href="https://en.wikipedia.org/wiki/RDMA_over_Converged_Ethernet" rel="nofollow">https://en.wikipedia.org/wiki/RDMA_over_Converged_Ethernet
> A sending station (computer or network switch) may be transmitting data faster than the other end of the link can accept it. Using flow control, the receiving station can signal the sender requesting suspension of transmissions until the receiver catches up. Flow control on Ethernet can be implemented at the data link layer.
* <a href="https://en.wikipedia.org/wiki/Ethernet_flow_control" rel="nofollow">https://en.wikipedia.org/wiki/Ethernet_flow_control
lokar · · focus · HN ↗
When a link becomes saturated working out how to manage that is a hard problem.
I have only used RoCE once at scale, it was really finicky. We would get big waves to pause frames that stalled everything.