Concept of SIP Trunking in OCS infrastructure...
SIP Trunking and Office Communications
Server 2007 R2...
SIP Trunking is a generic means
to connect multiple IP-PBXs across a wide area network (WAN) within
the same enterprise. To know more about SIP Trunking...
The purpose of a SIP Trunk in an Office Communications Server
topology is to enable an enterprise to connect its on-premises voice
network to a service provider offering Public Switched Telephone
Network (PSTN) origination and termination. Relying on an
independent server provider for PSTN connectivity eliminates the
need to deploy and maintain IP-PSTN gateways.
The Office Communications Server 2007 R2 Session Initiation Protocol
(SIP) Trunking capability enables the following scenarios:
An enterprise user inside or outside the corporate firewall can make
a local or long-distance call specified by an E.164-compliant number
that is terminated on the PSTN as a service of the corresponding
Any PSTN subscriber can contact an enterprise user inside or outside
the corporate firewall by dialing a Direct Inward Dialing (DID)
number associated with that enterprise user.
How does it work?
An IP Virtual Private Network (VPN) is used for connectivity between
the enterprise network (OCS VOIP) and the PSTN service provider. The
purpose of this private network is to provide IP connectivity,
security, and (optionally) quality-of-service guarantees.
In this SIP trunking topology, the Mediation Server performs media
and signaling translation, just as it does when connected to an
enterprise IP-PSTN gateway.
All SIP traffic and media traffic between the enterprise network and
the service provider network flows through the VPN and Mediation
The Mediation Server can discover the service provider proxy (the
Session Border Controller in the diagram) through:
Static provisioning, in which the Mediation Server is provisioned
manually with a Fully Qualified Domain Name (FQDN) or IP address of
the service provider proxy.
A Domain Name System (DNS) query against an FQDN published by the
PSTN service provider.
The PSTN service provider can use either of these methods for
discovering the list of enterprise proxies (Mediation Servers) to
which it can connect.
Note: This article applies to Office
Communications Server 2007 R2.
What is SIP Trunking?
SIP Trunking and Best Practices
Using IP Trunking to maximize value creation