Data center congestion management for non-TCP traffic
Methods, apparatus and software for implementing enhanced data center congestion management for non-TCP traffic. Non-congested transit latencies are determined for transmission of packets or Ethernet frames along paths between source and destination end-end-nodes when congestion along the paths is not present or minimal. Transit latencies are similarly measured along the same source-destination paths during ongoing operations during which traffic congestion may vary. Based on whether a difference between the transit latency for a packet or frame and the non-congested transit latency for the path exceeds a threshold, the path is marked as congested or not congested. A rate at which the non-TCP packets are transmitted along the path is then managed as function of a rate at which the path is marked as congested. In one implementation, non-TCP traffic is managed by mimicking a Data Center TCP technique, under which the congestion marking status of the path is substituted as an input to a DCTP algorithm in place of the normally-used ECN-Echo flag input. The congestion window output by the DCTCP algorithm is then used to manage the rate at which non-TCP packets to be forwarded via the path are transmitted from a source end-node.
1. A method for implementing congestion management of non-TCP (Transmission Control Protocol) traffic in a network, comprising:
determining a non-congested transit latency for a path between a source end-node and a destination end-node, wherein the path traverses at least one switch and the non-congested transit latency is an overall transit latency for the path;
measuring transit latencies for transfer of non-TCP packets or Ethernet frames encapsulating non-TCP packets along the path between the source end-node and the destination end-node, each transit latency that is measured for a non-TCP packet or an Ethernet frame encapsulating a non-TCP packet comprising an overall transit latency for the path;
determining, for transfer of each of at least a portion of the non-TCP packets or Ethernet frames, whether to mark the path as congested or not congested based on a difference between the transit latency measured for the non-TCP packet or Ethernet frame and the non-congested transit latency determined for the path; and
managing a rate at which the non-TCP packets are transmitted from the source end-node to be forwarded via the path to the destination end-node based as a function of a rate at which the path is marked as congested,
wherein the non-congested transit latency is an overall transit latency that is measured along a one-way path from the source end-node to the destination end-node, and each of the transit latencies for the transfer of the non-TCP packets or the Ethernet frames is an overall transit latency that is measured along the same one-way path.
2. The method of claim 1 , further comprising mimicking Data Center TCP (DCTCP) for non-TCP traffic by:
inputting into a DCTCP algorithm a congestion marking status of the path in place of using a congestion marking status conveyed via an ECN-Echo flag as an input to the DCTCP algorithm; and
employing a congestion windows (cwnd) output by the DCTCP algorithm to manage the rate at which the non-TCP packets are transmitted from the source end-node.
3. The method of claim 1 , further comprising:
measuring a best frame transit time (BFTT) along a source-destination path from the source end-node to the destination end-node, and storing the BFTT for the source-destination path;
for each of a plurality of Ethernet frames encapsulating non-TCP packets, measuring a frame transfer time (F) along the source-destination path for the Ethernet frames;
subtracting the BFTT from the FIT and determining whether the result of the subtraction exceeds a threshold;
if the result of the subtraction exceeds the threshold, marking a congestion flag in an ACK packet that is returned from the destination end-node to the source-destination end-node, otherwise leaving the congestion flag in the ACK packet unmarked;
detecting a marked status of the ACK packet via inspection of the congestion flag; and employing the marked status to implement congestion management for the path.
4. The method of claim 1 , wherein the method is implemented for a plurality of paths between a plurality of source and destination end-nodes, the plurality of paths collectively traversing a plurality of switches, and wherein the method is implemented without any modification to the switches.
5. The method of claim 1 , wherein the method is implemented by modifying at least one of software or hardware components configured to implement a conventional non-TCP protocol only at the source end-node, wherein the destination end-node employs conventional software and hardware components for implementing the non-TCP protocol.
6. The method of claim 1 , wherein the non-TCP traffic comprises one of RDMA over Converged Ethernet (RoCE) traffic or Fiber Channel over Ethernet traffic.
7. The method of claim 1 , wherein the method is facilitated via the use of timestamps corresponding to when an Ethernet frame is transmitted from a transmit port and received at a receive port, and further wherein at least one timestamp is added to a field in the Ethernet frame.