CPaaS and VoIP Terminology

Core Concepts

REG (Registered)

A fundamental SIP concept where devices and agents establish presence on the platform. Registration involves sending SIP REGISTER messages, authenticating with credentials, and maintaining registration through periodic renewals. Registration status is essential for call routing and system health monitoring.

OOS (Out of Service)

Indicates that a device is unavailable. This can be caused by network issues, hardware failures, maintenance windows, or registration expiration. Monitoring OOS duration and frequency is important for system reliability.

Device AOR (Address of Record)

The canonical SIP URI address for a device. Formats include:

sip:user@domain
sips:user@domain (encrypted)

The AOR may include transport parameters and can vary between user-agents and device-agents.

FQDN (Fully Qualified Domain Name)

The complete domain name for a VoIP host. FQDNs are used for SIP server identification, certificate validation, DNS SRV records, and load balancing.

CDR (Call Detail Record)

Comprehensive call metadata captured for every call. Includes timestamps, addresses, duration, routing information, quality metrics, termination reasons, jitter, packet loss, and codec data. See CDR Field Mappings for the full field reference.

SIP Protocol

SIP Methods

Method	Purpose
`INVITE`	Initiate a session (start a call)
`BYE`	Terminate a session (end a call)
`REGISTER`	Register or update device presence
`SUBSCRIBE`	Request event notifications
`NOTIFY`	Deliver event notifications
`OPTIONS`	Query capabilities

SIP Response Codes

Range	Category	Examples
1xx	Provisional	100 Trying, 180 Ringing, 183 Session Progress
2xx	Success	200 OK
3xx	Redirection	302 Moved Temporarily
4xx	Client Error	401 Unauthorized, 404 Not Found, 486 Busy Here
5xx	Server Error	500 Internal Server Error, 503 Service Unavailable
6xx	Global Error	603 Decline

Media and Transport

RTP (Real-time Transport Protocol)

The protocol used for delivering audio and video over IP networks. RTP handles packet sequencing, timing, media mixing, and payload identification. It works alongside RTCP (RTP Control Protocol) for quality monitoring.

ICE (Interactive Connectivity Establishment)

A NAT traversal framework that enables media connections between endpoints behind firewalls. ICE uses:

STUN (Session Traversal Utilities for NAT) — discovers the public IP and port of an endpoint
TURN (Traversal Using Relays around NAT) — relays media when direct connections fail

ICE performs candidate gathering and connectivity checks to find the best media path.

User Status

Presence

A real-time availability status system. Common presence states include:

State	Meaning
Available	User is ready to receive calls
Busy	User is on an active call or has set themselves as busy
Away	User is temporarily unavailable
Do Not Disturb	All calls are sent to voicemail or rejected

Presence can also include custom states configured by the administrator.