HSN CXI Address Calculation

Purpose

This report summarizes the investigation into whether Copper transport endpoints can be derived directly from HSN interface metadata on Aurora-class systems.

The work used:

  • a distributed collector that records hostnames, HSN IPv4 addresses, MAC addresses, and Thallium CXI self-addresses

  • a parser and analyzer that compares those fields across cabinets, chassis, slots, and interface indices

Main Finding

CXI addresses are structured, but they are not derivable from a simple one-step mapping based only on HSN IPv4 address or MAC address.

The strongest observed structure is associated with:

  • cabinet family

  • chassis grouping

  • slot placement

  • interface-pair symmetry across cxi0 through cxi7

Questions Investigated

The study was designed to answer the following questions:

  1. Can a CXI address be predicted directly from an HSN IPv4 address?

  2. Can a CXI address be predicted directly from the corresponding MAC address?

  3. If not, what parts of the CXI hexadecimal representation exhibit stable structure?

  4. Can a partial decoding rule be proposed from observed node, slot, and interface patterns?

Data Collection Summary

The collector produces rows with the following structure:

hostname | hsn0 | mac0 | cxi0 | hsn1 | mac1 | cxi1 | ... | hsn7 | mac7 | cxi7

The resulting table is suitable for:

  • address-book validation

  • endpoint provenance checks

  • fabric regularity studies

  • future tooling that reasons about network placement

Primary Conclusions

  • There is no strong direct equality rule between HSN last-octet values and CXI low-byte values.

  • There is no strong direct equality rule between MAC tail bytes and CXI low-byte values.

  • Higher CXI hexadecimal digits correlate with cabinet family.

  • Middle hexadecimal digits show chassis-level structure.

  • Interface-pair symmetry is visible across the CXI endpoint set.

Operational Use

This report is most useful for:

  • validating address-book generation logic

  • investigating inconsistent endpoint assignments

  • checking whether a discovered address-book artifact looks structurally plausible

Local Source and Tooling

The collector and related tooling live under:

  • copper-tests/copper-get-addressbook/

In particular:

  • list_cxi_hsn_thallium.cpp

  • compile_thallium_addressbook.sh

  • run_thallium_addressbook.slurm

  • run_thallium_addressbook.pbs