Howto:SBC scaling for large number of channels

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Applies To

This information applies to:

  • SBC functionality on Gateways or IPVA with v12r1 or later


More Information

Preamble

With the innovaphone SBC, we provide approximately 100 - 200 concurrent Channels per Gateway or IPVA. In bigger Scenarios where a few hundred (or more) Channels are required, several Gateways can be joined to a "Load Balancing Scenario" to provide a large number of Channels.

Because a lot of SIP Provider does not support multiple registrations from many different Gateways and cannot guarantee an evenly Call distribution (Load Balancing), a dedicated SBC as SIP-Gateway for registrations is needed.

Please ask your SIP Provider if he provides Multiple Registrations and Load Balancing before you start with the planning of the scenario.

This document describes the principles how to configure a "Load Balancing Scenario" with the reference to an example.

Be aware that this is just an example to explain how it works; maybe it’s a little bit different in your scenario - depending on the SIP Provider!


Function Principle

The Limitation of the concurrent Channels per Gateway is based on the Media Relay Feature. If this Feature is enabled (and it’s mandatory for the SBC), the Channels are limited.


To bypass this limit, the idea is:

  • to have a dedicated Gateway without Media-Relay. This acts only as Registration Gateway to the SIP Provider. Without Media Relay this Gateway can handle a very large number of calls. We call it "Register-GW" in this document.
  • to use as many Gateways as needed for Media Relay. All calls should be evenly distributed on this Gateway to have a "Load Balance Scenario". We call them "Relay-GWs" in this document.


Register-GW

  • On the "Register-GW" we need a PBX because only with the PBX we have an evenly distribution to several Gateways. Therefore the PBX must be enabled (Master) on this Gateway, but we need only two Gateway Objects in it. The first is for the registration from the Provider- SIP-Interface (on the same GW) and the second is for all registrations from the "Relay-GWs". No other object is needed.
  • The SIP-Interface to the Provider is similar to the SBC of the "Common Scenario". It has two registrations, one to the SIP Provider and another to the internal PBX. Only Media relay is disabled.
  • The default Routes between SIP Provider and PBX must be adapted.


Relay-GWs

The "Relay-GWs" are serving the Media Relay Part in this scenario. On each "Relay-GW" there are two registrations and simple routes between it.

  • One registration to the "Register-GW"- PBX with Media Relay and the same Media Properties like the SIP Interface to the Provider at the "Register-GW".
  • One registration to the real PBX w/o Media Relay with default settings.

SBC scenarios.jpg


Configuration Example

The following example shows how a configuration can be done, maybe it’s a little bit different in your scenario. Depending on the SIP Provider and the needed Number Mappings or Routes, there can be a lot of alternative Configurations

Overview

1) On the "Register-GW " the PBX must be enabled and

two Gateway Objects with a Number must be created. In

this example we have chosen the Prefix "1" for calls to

the SIP Provider and the Prefix "2" for calls to the

internal PBX.


2) The SIP Interface must be configured without Media

Relay. The SIP Registration goes to the Provider; the

internal Registration goes to the local PBX.


3) In the Routes TO the "PBX of the Register-GW", a

leading "2" must be added to reach the opposite

GW-Object in the "PBX of the Register-GW".

In the Routes FROM the "PBX of the Register-GW", the

leading "1" must be cut because it's not needed anymore.


4a) On the "Relay Gateway" one Interface must be

configured for the registration to the "PBX of the

Register-GW" with Media Relay


4b) On the "Relay Gateway" one Interface must be

configured for the registration to the Regular

PBX without Media Relay


5) In the Routes FROM the Regular PBX, the

Tone Interface and a leading "1" must be added to reach

the opposite GW-Object in the "PBX of the Register-GW".

In the Routes TO the Regular PBX, the leading "2"

must be cut because it's not needed anymore.

. ConfigurationOverview.jpg



Configuring the Customers regular PBX

1. Create a Trunk Object in the regular PBX

Of Course, in the regular PBX (where usually the Users are registered), a Trunk Object must be existing for external calls.

RealPBX 1TrunkObject.jpg

Configuring the Registration Gateway

2. Enable the PBX on the Register-GW

On the same GW where the SBC (SIP Interface to Provider) is configured, a PBX must be created. Any System or PBX Name can be chosen because it’s normally an isolated PBX. But two Port Licenses are needed for the two Gateway registrations.

RegisterGW 1MasterPBX.jpg


3. Create two Gateway Objects

Two Gateway Objects must be created on this PBX. Defaults settings can be used, but each Gateway Object must have a Number. In this example we have chosen the Prefix "1" for calls to the SIP Provider and the Prefix "2" for calls to the internal PBX.

RegisterGW 2PBX-GatewayObjects.jpg


4. Configure SIP Interface

At the SIP Interface to the Provider, nothing special must be configured, please use the Provider specific settings from the Profiles or from the Provider Documentation. Only Media Relay must be set to "off" and the internal registration goes to the PBX on its own Gateway.

RegisterGW 3SIP-Interface.jpg


4. Modification of the Routes

Following modification must be done in the Routes:

  • The "2" (Prefix of the second Gateway Object in the PBX) must be added to Numbers that goes to the PBX.
  • If there is a default Tone Mapping, it can be disabled or deleted.
  • The leading "1" (Prefix of the first GW Object in the PBX) must be cut from each Number that comes from the PBX.

RegisterGW 4Routing.jpg

Configuring the SBC Relay Gateways

The following configurations are absolute identical on each Relay Gateway.


5. Creation of GW Interfaces

Two GW Interfaces must be created. The first one is to register with the Second Gateway Object on the PBX of the "Register-GW". Here, the Media Relay must be enabled. The second one is to register with the Trunk Object on the regular PBX. Here, the Media Relay must be disabled. All other settings (like Codecs, T.38, etc.) are depending on your requirements.

RelayGW 1GW-Interfaces.jpg


6. Creation of the Routes

Routes must be created between these Gateway Interfaces:

  • The leading "2" (Prefix of the second Gateway Object in the Register GW PBX) must be cut from each Number that comes from the Register GW; "Interworking" should be set.
  • A standard Tone Mapping should be added.
  • The "1" (Prefix of the first GW Object in the Register GW PBX) must be added to the called Number that goes to the Register GW; "Interworking" should be set.

RelayGW 2Routing.jpg