You can find the slides presented during the tutorial here .
This repository starts from a fork of the UET transport simulation project to which it adds instructions to help participants in the Sigcomm 2025 Ethernet Networking for AI tutorial begin exploring the behaviour of congestion control and load balancing algorithms design for AI workloads.
The simulation works with synthetic traffic patterns called connection matrices which specify flow start times and sizes; all flows are assumed to be backlogged. The simulator does transport-level simulation only. The transport does not accurately model the UET transport; rather it is an idealized sprayed transport that has zero-RTT setup and that supports multiple load balancing algorithms, congestion control algorithms, and topologies.
The simulator does not model computation, semantic level operations (i.e. RDMA writes), colllective implementations or other higher level constructs.
#About htsim
HTSIM is a high-performance discrete event simulator used for network simulation. It offers faster simulation methods compared to other options, making it ideal for modeling and developing congestion algorithms and new network protocols. The role of htsim in the Ultra Ethernet Consortium (UEC) standards development is to support the transport layer working group's work on congestion control mechanisms.
In UEC, htsim:
- provides a platform for continuous implementation and development of UEC transport layer.
- is used to simulate and run different topologies and scenarios, helping to identify issues in the current specifications and estimate the throughput and latency for given parameters like topology, flow matrix and congestion configuration.
- provides a reference for users and developers to run simulations with different configurable parameters for various scenarios and algorithms
htsim's role is deliberately focused on congestion control.
UEC's htsim is not:
- a complete implementation of the UEC transport specification.
- a standard in any way; specifically, it is not part of the official UEC standards release. While we aim to match the spec as closely as possible, there might be discrepancies between the UEC CMS specification and the simulator. Only the official CMS specification is significant, the simulator is not.
Check the README file in the htsim/ folder.