---
title: Interconnect and download speed on GET /executors
description: The interconnect object and the nvlink verdict on every node listing, and the nvlink and min_download_mbps filters, so a script can pick a multi-GPU node that NCCL will actually use.
---

> ## Documentation Index
> Fetch the complete documentation index at: https://docs.lium.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Interconnect and download speed on `GET /executors`

A multi-GPU job runs at the speed of the link between the GPUs and at the speed the node can pull your data. [Before you rent 8 GPUs](/pod-users/multi-gpu-checks) explains how to check both by hand once the pod is up. This page is the API side: the listing now carries the answer, and you can filter on it before you rent.

## Two new fields on every node

Every node in `GET /executors`, and the `executor` object of a pod on `GET /pods`, has:

| Field | Type | Meaning |
|-------|------|---------|
| `nvlink` | `true`, `false` or `null` | `true` when every GPU pair on the node is joined by NVLink. `false` when at least one pair is not. `null` when no validator has reported the topology yet, or the node has one GPU. |
| `interconnect` | object or `null` | How the GPUs are wired, from the validator's `nvidia-smi topo` run. `null` until a scrape has reported it. |

`interconnect` has these keys, each `null` when the validator could not read it:

| Key | Meaning |
|-----|---------|
| `gpu_count`, `gpu_pairs` | GPUs on the host and the number of GPU pairs judged. |
| `nvlink` | Same verdict as the top-level field: every pair on NVLink. |
| `nvlink_links`, `nvlink_pairs`, `nvlink_active_links` | NVLink links per GPU, the pairs joined by NVLink, and the links that are up. A board with NVLink bridges on some pairs only reports `nvlink: false` with `nvlink_pairs` below `gpu_pairs`. |
| `pcie_class` | The worst PCIe class among the pairs that are not on NVLink: `SYS`, `NODE`, `PHB`, `PXB` or `PIX`, from worst to best. |
| `p2p`, `p2p_pairs`, `p2p_ok_pairs` | `p2p` is `true` only when every pair passed `nvidia-smi topo -p2p r`. A `false` here is the host where NCCL does not start without `NCCL_P2P_DISABLE=1`. |
| `matrix` | The GPU x GPU cell table from `nvidia-smi topo -m`, so a client can print the topology. |

The wiring of a host does not change between scrapes, so a scrape that fails to read the topology keeps the last known `interconnect` instead of turning the node back to `null`.

`nvlink` and `interconnect.nvlink` always carry the same value. Only a JSON boolean counts as a verdict when the API reads a stored row: a persisted string `"true"` reads as `null` in both places, and the `nvlink=true` filter leaves that node out. If one key of `interconnect` arrives in a shape the API cannot type, that key alone is `null` and the other keys stay. `interconnect` itself is `null` only when the host has no object at all.

A `specs.network` figure that is not a number is treated as missing, both by the `min_download_mbps` filter and by `effective_download_speed_mbps`. One such node does not fail the listing for everyone.

The [public nodes feed](/developers/public-nodes-feed) carries the `nvlink` verdict too. The full `interconnect` object stays on `GET /executors`.

## Two new filters

| Query parameter | Effect |
|-----------------|--------|
| `nvlink=true` | Only nodes whose `nvlink` is `true`. A node with no topology verdict yet is left out on purpose: an unknown box is not NVLink for a renter who asked for it. `false` or omitted means no filter. |
| `min_download_mbps=2000` | Only nodes whose most trusted download figure, in Mbps, is at least the value. The figure is the VerifyX average first, then the speed-test average, then the raw samples; zero counts as missing. A node with no measurement is left out. |

```bash
curl -s "https://lium.io/api/executors?nvlink=true&min_download_mbps=2000" \
  | jq '.[] | {id, nvlink, p2p: .interconnect.p2p, nvlink_active_links: .interconnect.nvlink_active_links}'
```

The response is the usual list of nodes; the two filters combine with the existing ones (`machine_names`, `price_lte`, `gpu_count_gte` and the rest). `GET /pods` takes the same two parameters and applies them to the node each pod runs on. In the lium SDK, `Lium.rent(min_download_mbps=...)` applies the download floor (lium 0.0.39 and later, through rent-by-spec). `Lium.rent(interconnect="nvlink")` is refused on lium.io, because rent-by-spec has no interconnect constraint: list with `nvlink=true` on this API and rent the node you picked with `Lium.up()`. The `lium ls` columns and the `--nvlink` filter are unreleased (lium#149, open); until then, call the API.