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OmniMessage IMS Frontend

SIP transport layer for OmniMessage - handles getting messages into and out of IMS networks

What it Does

This is a lightweight SIP frontend that acts as a transport layer between IMS networks and the OmniMessage backend. All message processing, routing logic, and business logic is handled by OmniMessage - this frontend simply:

  • Receives SIP REGISTER messages and forwards subscriber data to OmniMessage
  • Receives Mobile Originated (MO) SMS via SIP MESSAGE and forwards to OmniMessage
  • Retrieves Mobile Terminated (MT) SMS from OmniMessage and sends via SIP MESSAGE
  • Reports delivery status back to OmniMessage
  • Handles SIP-level protocol details (headers, acknowledgments, etc.)

Architecture

The IMS frontend consists of two main components:

SIP protocol handling:

  • SIP REGISTER - Extracts subscriber data and forwards to OmniMessage
  • SIP MESSAGE - Receives MO SMS and forwards to OmniMessage
  • SIP MESSAGE - Sends MT SMS from OmniMessage to subscribers
  • SIP NOTIFY - Handles event notifications
  • UAC responses - Captures delivery confirmations and forwards to OmniMessage

OmniMessage backend transport layer:

  • insert_location() - Sends subscriber registration data to OmniMessage
  • insert_message() - Sends incoming MO messages to OmniMessage
  • get_queue() - Retrieves pending MT messages from OmniMessage
  • process_message() - Sends delivery status updates to OmniMessage
  • frontend_register() - Registers this frontend with OmniMessage

All message processing, routing decisions, queuing, storage, and business logic happens in OmniMessage. This frontend is purely a SIP transport adapter.

Configuration

All configuration is stored in the config.yaml file.

Configuration Parameters​

api_base_url - Base URL for the OmniMessage backend API

  • Format: https://hostname:port
  • Example: https://10.5.198.200:8443
  • Used for all backend API calls (insert_location, insert_message, get_queue, etc.)

location - Identifier for this IMS frontend instance

  • Format: FQDN-style identifier
  • Example: smsc01.mnc001.mcc001.3gppnetwork.org
  • Used to identify this frontend in the backend system
  • Should be unique across all frontends

s_cscf_sip_uri - S-CSCF SIP URI for routing messages (optional)

  • Format: sip:hostname:port
  • Example: sip:127.0.0.2:5060
  • If set, all outbound SIP MESSAGEs route through this S-CSCF
  • If not set, messages route directly to the IMS domain

ims_domain - IMS domain for subscriber routing

  • Format: IMS domain name
  • Example: ims.mnc001.mcc001.3gppnetwork.org
  • Used to construct SIP URIs for subscriber addressing
  • Used when s_cscf_sip_uri is not configured

Message Flow

SIP REGISTER Flow​

Mobile Originated (MO) SMS Flow​

Mobile Terminated (MT) SMS Flow​