# WHATPORT(2126)

## NAME

port 2126 — PacketCable COPS — COPS signalling between a cable operator's call server and its CMTS to authorize per-call QoS.

Protocol: TCP  
IANA registry

## DESCRIPTION

IANA registers 2126 as PktCable-COPS, assigned to CableLabs. It carries the Common Open Policy Service protocol (RFC 2748) in PacketCable's Dynamic QoS architecture: the Call Management Server acts as the policy decision point and the CMTS as the policy enforcement point, and the CMTS opens gates that reserve DOCSIS bandwidth for a voice call only when the CMS authorizes it over this connection. This is operator infrastructure — you meet it inside a cable headend, not on a customer network.

## EXPOSURE

**Do not expose.** Anything that can talk COPS to a CMTS can influence which sessions get authorized bandwidth. Keep it on the operator's internal signalling network.

## CHECK

```sh
nc -vz TARGET 2126
```

## SEE ALSO

- spec — [RFC 2748 — The COPS (Common Open Policy Service) Protocol](https://www.rfc-editor.org/rfc/rfc2748.html) (rfc-editor.org)
- iana — [IANA Service Name and Transport Protocol Port Number Registry](https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml) (iana.org)

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HTML: <https://whatport.net/2126/> · JSON: <https://whatport.net/2126.json> · full dataset: <https://whatport.net/ports.json>