Sip registration forwarding

TSBC registration forwarding feature allows to control the registration requests flow between SIP User Agents and registrars. It allows adaptation of SIP register messages between SIP User Agents and registrars. It keeps information about SIP User Agent contacts and allows routing of SIP calls base on registration information.

Protection

• TSBC protects registrar from overloading of SIP User Agents register requests using different strategies (i.e. Firewall, Rate Adaptation, SIP Header Manipulation, Etc.).

Forwarding Modes

• The TSBC always modifies the contact URI in SIP register requests to remain on the path between SIP User Agents and registrars.
• The TSBC supports two different SIP registration forwarding modes (i.e. "Contact Remapping" or "Contact Passthrough").
• The "Contact Passthrough" forwarding mode makes contact username portion of the contact URI in SIP register requests to pass through unchanged.
• The "Contact Remapping" forwarding mode modifies contact username portion of the contact URI in SIP register requests and make it unique.

Registrar Selection Mode

• The TSBC supports Active/Standby registrar selection mode. The active registrar is the one with status up and the lowest priority (automatic fallback).

NAT traversal

• The TSBC handles SIP Calls NAT traversal then allows interaction between SIP User Agents from public and private networks.
• It supports SIP register requests "Rate Adaptation" between SIP User Agents and registrar.
• Because refreshing requests are not always sent to registrar, "Rate adaptation" feature reduces SIP register requests sent to registrar. The "Rate Adaptation" feature is also useful to keep firewall ports open.

SIP Calls routing

• The TSBC keeps SIP User Agents contacts information. This information serves on SIP calls routing when a SIP User Agent is trying to reach a registered users. It could be used also to accept calls from registered users only.

Registered users and routing scripts

In routing scripts, "dynamic" routes will be automatically created when a call is trying to reach a registered user.

• These "dynamic" routes will use the outbound NAP that the registered user had registered from
• These "dynamic" routes will add to any "static" routes that also match the incoming call (if any)

Priority of dynamic routes

When "priority_and_weight_load_balancer" routing script is used, ordering of dynamic vs. static routes can be controlled:

• Dynamic routes will inherit the priority of the outbound (remapped) NAP that the targeted registered user was registered from
• All matching routes (static and dynamic) will be ordered by priority
• Some static routes may have higher priority than dynamic routes, others lower priority
• The option :max_priority_delta can be used to get rid of all route with lower priority.
  • This can be used to keep only dynamic routes in some cases, for example if static routes have much lower priority than dynamic routes
  • This can be used to keep only static routes in other cases, for example when incoming calls are from a specific NAP which matches a very high priority route

Configuration

FreeSBC
3.0 Creating a SIP Domain