# System Requirements for Onsite Proxy

Before you deploy an Onsite Proxy, confirm that its host runs a supported operating system and has enough CPU and memory for the call volume you expect. The resources you allocate decide how many concurrent calls, IP phones, and BLF keys a single proxy can handle.

:::note
BLF stands for Busy Lamp Field. A BLF key is a programmable button on a desk phone that shows the live status of another extension (idle, ringing, or on a call). Each monitored extension counts as one BLF against the limits below.
:::

## Supported operating systems

Install the Onsite Proxy on one of the following platforms.

| Platform | Architecture | Distribution |
| --- | --- | --- |
| Linux | x86_64 | Ubuntu 24.04 LTS, Debian 12 |
| Linux | ARM64 | Raspberry Pi OS |

## Recommended specifications

Capacity scales with the CPU and memory you assign to the proxy at deployment time. Pick a configuration that comfortably covers your site, and give yourself headroom for growth.

| vCPU | Memory (GB) | Concurrent calls | IP phones | BLFs |
| --- | --- | --- | --- | --- |
| 1 | 1 | ≤ 250 | ≤ 500 | ≤ 500 |
| 2 | 2 | ≤ 500 | ≤ 1000 | ≤ 1000 |
| 4 | 4 | ≤ 1000 | ≤ 1000 | ≤ 1000 |

:::tip
Size the proxy to your busiest moment, not your total device count. Estimate the maximum number of calls that will be up at the same time, then choose the first row that clears that number with room to spare. Rounding up now is cheaper than redeploying a larger proxy later.
:::

:::caution
When several Onsite Proxies connect to the same Cloud Voice PBX, their combined concurrent calls cannot exceed the PBX's own concurrent-call limit. Traffic above that ceiling fails to connect, so plan the total across all proxies, not each proxy on its own. You can review the limit in the PBX system information on the dashboard.
:::