Gateway Application

The objective of your configuration is to enable the device to forward calls between the IP-based endpoints and PSTN-based endpoints. The PSTN-based endpoints can be digital endpoints such as ISDN trunks. The IP-based endpoints (SIP entities) can be servers such as SIP proxy servers and IP PBXs, or end users such as LAN IP phones. In the SIP world, the endpoints are referred to as SIP user agents (UA). The UA that initiates the call is referred to as the user agent client (UAC); the UA that accepts the call is referred to as the user-agent server (UAS).

The following table describes the main configuration concepts and terminology.

Configuration Concepts and Terminology

Configuration Terms

Description

IP Groups

An IP Group is a logical representation of the SIP entity (UA) with which the device receives and sends calls. The SIP entity can be a server (e.g., IP PBX or SIP Trunk) or it can be a group of users (e.g., LAN IP phones). For servers, the IP Group is typically used to define the address of the entity (by its associated Proxy Set). IP Groups are typically used in Tel-to-IP routing rules to denote the destination of the call.

Proxy Sets

A Proxy Set defines the actual address (IP address or FQDN) of SIP entities that are servers (e.g., IP PBX). As the IP Group represents the SIP entity, to associate an address with the SIP entity, the Proxy Set is assigned to the IP Group.

SIP Interfaces

A SIP Interface represents a Layer-3 network for the IP-based SIP entity. It defines a local listening port for SIP signaling traffic on a local, logical IP network interface. The term local implies that it's a logical port and network interface on the device. The SIP Interface is used to receive and send SIP messages with a specific SIP entity (IP Group). Therefore, you can create a SIP Interface for each SIP entity in the VoIP network with which your device needs to communicate.

The SIP Interface is associated with the SIP entity, by assigning the SIP Interface to an SRD that is in turn, assigned to the IP Group of the SIP entity.

Media Realms

A Media Realm defines a local UDP port range for RTP (media) traffic on any one of the device's logical IP network interfaces. The Media Realm is used to receive and send media traffic with a specific SIP entity (IP Group).

The Media Realm can be associated with the SIP entity, by assigning the Media Realm to the IP Group of the SIP entity, or by assigning it to the SIP Interface associated with the SIP entity.

SRDs

An SRD is a logical representation of your entire VoIP network. The SRD is in effect, the foundation of your configuration to which all other previously mentioned configuration entities are associated.

Typically, only a single SRD is required and this is the recommended configuration topology. As the device provides a default SRD, in a single SRD topology, the device automatically assigns the SRD to newly created configuration entities. Thus, in such scenarios, there is no need to get involved with SRD configuration.

Multiple SRDs are required only for multi-tenant deployments.

IP Profiles

An IP Profile is an optional configuration entity that defines a wide range of call settings for a specific SIP entity (IP Group). The IP Profile includes signaling and media related settings, for example, jitter buffer, silence suppression, voice coders, fax signaling method, SIP header support (local termination if not supported), and media security method. The IP Profile is in effect, the interoperability "machine" of the device, enabling communication with SIP endpoints supporting different call "languages".

The IP Profile is associated with the SIP entity, by assigning the IP Profile to the IP Group of the SIP entity.

Tel Profiles

A Tel Profile is an optional configuration entity that defines a wide range of call settings for a specific PSTN-based endpoint. The IP Profile includes settings such as message waiting indication (MWI), input gain, voice volume and fax signaling method.

The Tel Profile is associated with the PSTN-based endpoint, by assigning it to the Trunk Group belonging to the endpoint.

Tel-to-IP Routing Rules

Tel-to-IP routing rules are used to route calls from PSTN-based endpoints to an IP destination (SIP entity). The PSTN side can be denoted by a specific Trunk Group, or calling or called telephone number prefix and suffix. The SIP entity can be denoted by an IP Group or other IP destinations such as IP address, FQDN, E.164 Telephone Number Mapping (ENUM service), and Lightweight Directory Access Protocol (LDAP).

IP-to-Tel (Trunk Group) Routing Rules

An IP-to-Tel Routing rule is used to route specific incoming IP calls to a specific Trunk Group. The specific channel pertaining to the Trunk Group to which the call is routed can also be configured.

Accounts

An Account is used to register or authenticate PSTN-based endpoints with a SIP entity (e.g., a registrar or proxy server). The device does this on behalf of the PSTN-based endpoint. Authentication (SIP 401) is typically relevant for INVITE messages forwarded by the device to a SIP entity. Registration is for REGISTER messages, which are initiated by the device on behalf of the PSTN-based endpoint.

The following figure shows the main configuration entities and their involvement in call processing. The figure is used only as an example to provide basic understanding of the configuration terminology. Depending on configuration and network topology, the call process may include additional stages or a different order of stages.