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If you're looking for a solution that enables you to connect your Office Communications Server infrastructure to the PSTN, you will want to consider configuring a SIP Trunk. A SIP trunk configuration is a great way to go if you don't already have an IP/PBX.
Author: Rui Maximo, Mike Wood (ThinkTel)
Publication date: March 9, 2010
Product version: Microsoft Office Communications Server 2007 R2
If you're looking for a solution that enables you to connect your Office Communications Server infrastructure to the PSTN, you will want to consider configuring a SIP Trunk. A SIP trunk configuration is a great way to go if you don't already have an IP/PBX. If you already have an IP/PBX, connecting your Office Communications Server to your IP/PBX using Direct SIP is an option that will take advantage of your existing IP/PBX investment. A SIP trunk is less complex to set up and requires no extra hardware, such as an IP/PBX, to deploy. This article covers how to set up a SIP trunk from ThinkTel (http://www.ThinkTel.ca). ThinkTel is a supported SIP trunk provider that participates in the Open Interoperability Program (OIP) (http://go.microsoft.com/fwlink/?LinkId=178632) for Communications Server 2007 R2 and is based in Canada.
To configure a ThinkTel SIP trunk with your Office Communications Server infrastructure, you'll need to complete the following steps. These can be performed easily in less than 15 minutes:
Order Your ThinkTel SIP Trunk
To order your SIP trunk, go to http://support.thinktel.ca/siptrunk/retail. The process is simple. On the SIP trunk order form shown in Figure 1, specify your information. In particular, the following settings must be set to specific values:
Figure 1. ThinkTel SIP trunk order
After you submit your order form, ThinkTel will send you an e-mail that has a ticket number for your order. Typically within 24 to 48 hours, you will get an e-mail back from the system that has your pilot number (used as your billing number) and SIP proxy. You can use this pilot number as a regular DID; however, it is recommended that you assign new numbers for your organization and users and leave this unused to make bill consolidation easier. The SIP proxy will be used to configure the PSTN Gateway IP address field of your Mediation Server.
To manage your ThinkTel account, go to https://dims.thinktel.ca and log on by using the credentials sent to you in e-mail. You can allocate more phone numbers by clicking the PBX DID Orders link on the right side of the page. On this site you can also add and edit 911 listings on a per DID basis, review your bill, download CDRs, and monitor the usage on your trunks to ensure you always have capacity available.
In addition to making changes to your account, you can request access to a Web-based API that enables you to take inventory of your existing numbers, locate rate centers with available numbers, and order new numbers. The API is available through a REST or SOAP interface.
Configure Your External Firewall
Because your ThinkTel SIP trunk connects to your Mediation Server, all you have to do is allow incoming and outgoing traffic between your Mediation Server and ThinkTel. Generally, by default, outgoing traffic that originates from your internal network is allowed by most firewalls. Consequently, you need to configure firewall rules to allow only incoming traffic originating from the Internet. Two firewall rules are required to flow through your firewall:
Create a Phone Route to Route Outbound Calls to Your SIP Trunk
Before your users can initiate outbound calls to your ThinkTel SIP trunk, you must specify a route. This route defines where to send outbound calls to. Because calls going to the SIP trunk must first pass through your Mediation Server, you must route outbound calls to your Mediation Server first. The Mediation Server will then route calls to your SIP trunk. To keep things simple, we'll define a rule that routes all outbound calls to your Mediation Server.
Figure 2 illustrates this configuration.
Figure 2. Phone Route
The next step is to create a location profile. A location profile defines a set of normalization rules. This location profile will be assigned to your Mediation Server and users so they can dial out to the SIP trunk. The normalization rules specify which phone number formats are acceptable and what format phone numbers will be converted to. You can define the phone number formats to accept any format as long as the phone number is not ambiguous. However, the resulting format these phone numbers are translated to must conform to E.164 format to be accepted by your SIP trunk provider.
To create a location profile:
Figure 3. Normalization rule
Configure Your Mediation Server
Assuming your Mediation Server is already installed, activated, and set up to communicate with your Communications Server infrastructure, we'll focus on assigning the location profile that you just created to your Mediation Server (Figure 4) and configuring it to connect to your ThinkTel SIP trunk as its PSTN gateway (Figure 5).
Figure 4. Assign Location Profile to Mediation Server
Figure 5. Mediation Server SIP trunk configuration
Configure Your Users
The direct inward dialing (DID) numbers provided by your SIP trunk provider must be associated to the user accounts in your organization for inbound call routing to work. These DID numbers should be assigned to users in E.164 format. When an incoming call originates from the SIP trunk, Communications Server performs a reverse number lookup (RNL) of the DID to determine which user account is assigned this number. Office Communications Server translates the TEL URI number to the corresponding user's SIP URI and routes the call to the user.
To configure a user with a DID number (Figure 6):
Figure 6. User Configuration for Enterprise Voice
Configuring a SIP trunk provides PSTN access to Communications Server 2007 R2 users. In working with our partner, ThinkTel has streamlined the process and user interface for ordering a SIP trunk for Office Communications Server 2007 R2 making the entire process simple. ThinkTel Communications is a partner in the Microsoft Unified Communications Open Interoperability Program. Acknowledgements go to the ThinkTel team for providing a test SIP trunk and explaining their offering so I could author this article. In particular, I would like to thank Mike Wood for his expertise and assistance.
To learn more, check out the following articles:
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