Introducing Unified Messaging in Office Communications Server 2007 environment
The Unified Messaging component of Exchange 2007 SP1 is the designed to be the voice mail solution for Office Communications Server 2007 (OCS). What it means is that anyone can dial an Office Communications Server user and leave a voice mail which will then be delivered to that user's Outlook inbox. The integration of Office Communication Server 2007 and Exchange 2007 Unified Messaging will take users closer to the vision Microsoft has for Unified Communications.
http://www.microsoft.com/presspass/exec/jeff/06-26-06UnifiedCommunications.mspx
For an enterprise with Office Communications Server 2007, the integration of Unified Messaging (hence Exchange 2007) will give enterprise users the added benefit of having e-mail, voice mail, and fax messages consolidated in their inbox. Moreover, certain voice mail features can now be accessed using Office Communicator clients. The Unified Messaging role must be deployed with Exchange 2007 service pack 1 to support this integration.
In an integrated environment when a call to a person is not answered (busy, ring no answer, or diverted to voice mail) it gets routed to the Unified Messaging server (UM). The front end server role of OCS (or the Director) is responsible for processing and routing the call to the UM server.
Clients for OCS can be one of the following:
• Office Communicator (OC)
• OC qualified IP phone device
These clients are also known as Unified Communications Clients or UC Clients. Any user in Active Directory (AD) will have to be enabled and configured for voice capability to talk to the OCS server. The same client will also have to be enabled for Unified Messaging to divert their missed call to the UM server.
Common Scenarios
Following are some of the common scenarios where a call will route through OCS as well as UM. In each of these scenarios the users are enabled for Office Communications as well as Unified Messaging.
Divert to Voice Mail
User A calls User B, who does not answer. The call is then diverted to the UM server by OCS. Exchange UM plays a greeting previously recorded by User B, after which User A records a message. User B receives the voice mail message in their e-mail inbox with contextual information (additional contact information, phone numbers, title) provided in the body of the voice mail message. Callers can are identified through Active Directory or from User B's personal address book in Outlook. Finally, Outlook and Outlook Web Access both display this message along with an embedded player to play the voice message.
Subscriber Access
User A logs on using Office Communicator and selects the option to call voice mail. Since the user is already authenticated through Office Communicator, UM will not require the user to enter their PIN. Exchange UM will play the prompts for voice mail, e-mail, and calendar in Outlook Voice Access, all of which is pulled from User A's mailbox. User A selects to listen to their voice mail.
Auto-Attendant
User A does not know User B's direct line or extension, so User A calls the public access number for User B's organization. User B is connected to the Exchange UM Automated Attendant, which offers various options, including a corporate directory. User A says User B's name verbally, which is recognized by the Automated Attendant and User A's call is transferred to User B's extension in the organization.
Better Together
Integration of OCS and UM gives users a seamless experience to communicate across their entire organization. A UC client has the option to do instant messaging, audio-video conversations, conferencing, and access to all UM functionality from their UC client.
The following are some of the key features of this experience:
• Provides a single authentication method – A user who has logged into Office Communicator does not need to enter their PIN when they check their voice mail from the Office Communicator interface.
• Maintain subject name and priority - An OC user can add subject and priority when making a call. If the call gets diverted to UM, the subject is added to the subject line of the message containing the voice mail or the missed call notification. Additionally, the priority of the original call is maintained by UM in the auto-generated notification for missed calls or new voice mails.
• Integrated missed call notifications - When a call is missed by the receiving party, UM will generate an e-mail notification for the missed call and place it in the inbox for the receiving party.
• Both missed calls and voice mails show the name and contact information for the calling party user. This information is retrieved through Active Directory or from the called party user's personal contact list.
• Traversing the firewall - Media streams can be traversed through the corporate firewall securely without complicated configurations.
• High fidelity voice quality - UM now supports high fidelity codecs for voice mail recording and play back.
E.164 Number Format
The format of the telephone number associated with the UC-enabled user is E.164 (example: +19805551234). Therefore, if a user enters a number that is in different format (example: extension 1234) it has to be manipulated into the E.164 format. OCS will take this number and search the corporate directory to find the user who has a matching number and then voice mail will be routed to the correct user. OCS uses normalization rules to translate these number formats and uses an internal translation service to perform canonicalization transformation. Stay tuned for future blog post on this topic.
A Simple Scenario
In this scenario User A makes a call to user B using Office Communicator. User B does not answer and the call is forwarded to voice mail. User A hears the mailbox greeting and leaves a voice mail for User B.
Call Flow
The following is the call flow for the above scenario:
1. When User A makes a call to User B, the request is first sent to the OCS front end server as a SIP INVITE. OCS will first try to find the target user (User B) in AD and determine whether User B is OC-enabled. If the user is OC-enabled, the call will be forwarded to the registered SIP endpoint for User B. OCS will send the request as a SIP INVITE.
2. If User B does not answer the call, a response message will be sent back to OCS server indicating that User B did not answer the call.
3. OCS will query AD to find out if User B is UM-enabled, and if so, will extract out information such as their proxy address, dial plan name, and the UM server(s) assigned to the dial plan. OCS will use its routing logic to determine the appropriate UM server to route the call to.
4. A new INVITE request will be sent to the UM server by the OCS server. In this new INVTIE request, User B's SIP address will be added as a diversion header indicating that this is a voice mail call for User B.
5. A new session will be created between OCS and UM. OCS will exchange media information with UM and indicate that the RTP end point is the IP address of User A. After media negotiation is done, UM will establish a RTP session with User A and play prompts for leaving a voice mail. User A will directly communicate with UM and leave a voice mail for User B.
6. The remainder of the communication remains the same for any Exchange 2007 environment. After the voice mail is received by UM, it will be handed it off to a hub-transport server which will in turn route the voice mail to the user's mailbox on the appropriate mailbox server.
Configuring Unified Messaging and Office Communications Server 2007
Microsoft Exchange Server 2007 Unified Messaging and Microsoft Office Communications Server 2007 can be deployed together to provide voice messaging, Instant Messaging (IM), enhanced user presence, audio-video conferencing, and an integrated e-mail and messaging experience for users in your organization. This topic discusses how to configure Exchange 2007 Unified Messaging and Communications Server 2007 to support these features.
Deploying Exchange Unified Messaging and Communications Server 2007
Exchange 2007 Unified Messaging combines voice messaging and e-mail messaging into a single messaging infrastructure. Communications Server 2007 Enterprise Voice takes advantage of the Unified Messaging infrastructure to provide voice mail, subscriber access, call notification, and auto attendant services.
Before you can implement these services or features, you must do the following:
• Install Communications Server 2007 in the same Active Directory directory service topology as the Unified Messaging servers.
• Deploy the following Exchange 2007 server roles:
• Unified Messaging server role The Unified Messaging server connects Exchange 2007 with Communications Server 2007.
• Hub Transport server role The Hub Transport server routes e-mail messages from the Unified Messaging server to user mailboxes.
• Client Access server role The Client Access server hosts client protocols, such as Post Office Protocol 3 (POP3), Internet Message Access Protocol 4 (IMAP4), Secure Hypertext Transfer Protocol (HTTPS), Outlook Anywhere (formerly known as RPC over HTTP), the Availability service, and the Autodiscover service. The Client Access server also hosts Exchange Web services.
• Mailbox server role The Mailbox server hosts user mailboxes.
• Install Exchange 2007 Service Pack 1 (SP1) on the computers that have the Unified Messaging server role installed.
• Install and configure Communications Server 2007 in your organization, as follows:
1. Install Communications Server 2007 on servers in your organization.
2. Install a valid certificate that is valid and signed by a certification authority on the Communications Server 2007 servers.
3. Make sure that the certificate that you installed on the Communications Server 2007 servers is trusted by the Unified Messaging servers.
4. Confirm that at least one Communications Server 2007 pool object is created during installation.
Certificate Configuration Recommendations
You must have a certificate that is trusted by both the computers that are running Microsoft Exchange and Office Communications Server 2007. In an environment that has Office Communications Server 2007 and Exchange 2007 Unified Messaging, use the following guidelines for deploying a trusted certificate:
• Import a certificate that is valid and signed by a certification authority (CA). This should be a trusted third-party commercial certificate or a public key infrastructure (PKI) certificate and should be imported on the Communications Server 2007 computers and the Exchange servers that have the Unified Messaging and Client Access server roles installed.
• The most simple certificate deployment scenario is to import the same third-party commercial or PKI certificate to each Exchange 2007 server that has the following server roles installed: Unified Messaging, Client Access, and Hub Transport. Also install this trusted certificate on each computer that is running Office Communications Server 2007. This will help simplify your certificate deployment and reduce the administrative overhead associated with deploying certificates. However, you must obtain a trusted certificate that supports Subject Alternative Names (SANs).
• Although you can install the Unified Messaging server role and other Exchange 2007 server roles on the same computer, when you are deploying Communications Server 2007 we recommend that you install the Unified Messaging server role on a computer that will not be running other Exchange 2007 server roles. If another server role is installed on the same computer as the Unified Messaging server role, the Microsoft Exchange Unified Messaging service may select the incorrect certificate and be unable to use mutual TLS to encrypt traffic. This occurs because of limitations with subject alternative names found in certificates.
For example, if you install the Unified Messaging server role first, and then later install the Client Access server role on the same server, the Microsoft Exchange Unified Messaging service will use the certificate that is created by the Client Access server role instead of the certificate that was created when the Unified Messaging server role was installed. This is because the Microsoft Exchange Unified Messaging service looks for the certificate in the Trusted Root Store that has the most time left before it will expire.
• Because the trusted certificate uses mutual TLS to establish an encrypted channel with Communications Server 2007, Client Access, Hub Transport, and Unified Messaging servers, the name on the certificate that is used during mutual TLS negotiation must match the fully qualified domain name (FQDN) of the server that presents the certificate.
Deployment Path
After you have installed the required server roles in your Exchange 2007 organization, there is a recommended sequence of steps that you must perform on the Exchange UM environment and in your Communications Server 2007 environment to correctly deploy Enterprise Voice and Exchange 2007 Unified Messaging. Exchange 2007 Unified Messaging is used to provide call answering, Outlook Voice Access, and auto attendant services. Communications Server 2007 enables more advanced features that are found in Enterprise Voice services. The following figure illustrates the recommended deployment path for implementing Enterprise Voice services found with Exchange 2007 Unified Messaging and Communications Server 2007.
Deploying Exchange 2007 Unified Messaging and Office Communications Server 2007
There are several steps that you must complete to configure Exchange 2007 Unified Messaging to work with Enterprise Voice in Communications Server 2007. You must do the following:
1. Create one or more Exchange 2007 Unified Messaging Session Initiation Protocol (SIP) URI dial plans that each map to a corresponding Communications Server 2007 location profile. An Enterprise Voice location profile must be created for each Exchange UM dial plan. The location profile name has to match the fully qualified domain name (FQDN) of the UM dial plans. The Unified Messaging dial plan FQDN is used as the name of its corresponding location profile. Use the Get-UMDialPlan cmdlet to obtain the FQDN of a SIP URI dial plan, and then create its corresponding location profile.
2. Install a certificate on the Unified Messaging servers that is valid and signed by a certification authority, and then restart the Microsoft Exchange Unified Messaging service on each Unified Messaging server.
3. To encrypt the VoIP traffic, configure the SIP URI dial plan as SIP secured or Secured.
Although a Unified Messaging dial plan can be configured as SIP Secured or Secured, we recommend that you configure the dial plan as Secured to enable Microsoft Office Communicator Phone Edition devices to work correctly. This is recommended because of the default encryption level settings that are configured in Communications Server 2007. An Office Communicator Phone Edition device will only work if the encryption settings are configured as they are in the following table. This table shows the relationship between the encryption settings for both Communications Server 2007 and Unified Messaging dial plans.
Encryption settings for Office Communicator Phone Edition
4. Add the servers that are running the Unified Messaging server role to the SIP dial plan. To enable the server to answer incoming calls, you must add the Unified Messaging server to a dial plan.
5. Create a SIP address for the users who will be using Enterprise Voice.
6. Open the Exchange Management Shell and run the exchucutil.ps1 script that is located in the Exchange Installation folder\Exchange Server\Script folder. The exchucutil.ps1 script does the following:
• Grants Office Communications Server permission to read Exchange UM Active Directory objects, specifically, the SIP URI dial plan objects that were created in the previous task.
• Creates a UM IP gateway object in Active Directory for each Communications Server pool or for each server that is running Communications Server 2007 Standard Edition that hosts users who are enabled for Enterprise Voice.
• Creates an Exchange UM hunt group for each gateway. The hunt group pilot identifier will be the name of the dial plan that is associated with the corresponding gateway. The hunt group must specify the Exchange 2007 Unified Messaging SIP dial plan that is used with the UM IP gateway.
You must also complete the following tasks to configure Communications Server 2007 to work with Exchange 2007 Unified Messaging:
• Create location profiles. The location profile name has to match the FQDN of the corresponding UM dial plans.
• Assign location profiles to Communications Server 2007 pools.
• Deploy and configure media gateways and Mediation Servers.
• Define telephone usages, voice policies, and outbound call routes.
• Configure the users for Enterprise Voice services.
• Run the ocsumutil.exe command that creates the contact objects for subscriber access and for the auto attendant. It also validates that there is a location profile name whose name matches the FQDN of the Exchange UM dial plan.
After you have configured the Communications Server 2007 and the Unified Messaging servers, you must enable the user to use Communications Server 2007 and install Office Communicator 2007 on the user's client computer.
Configuring Exchange unified messaging with OCS 2007
Exchange 2007 Unified Messaging combines email, voicemail and fax into a single unified message store. Office Communications Server 2007 integrates into the UM infrastructure to provide call answering, subscriber access, call notification and auto-attendant services. But what's the best way to integrate both products? Configuring Exchange for OCS isn't that different from configuring UM with other IP-based private branch exchanges (PBX).
An Exchange UM dial plan supports three different security levels: unsecured, SIP secured, and secured, the below table shows the differences in terms of Mutual TLS and SRTP for each security level.
You'll want to create a UM dial plan for each Enterprise Voice location profile.
When integrating Exchange UM with OCS 2007 and selecting the appropriate dial-plan security level, consider the following criteria:
• Mutual TLS is required between Exchange UM and OCS. Unsecured level is not an option.
• Office Communicator 2007 clients support secure real-time transport protocol (SRTP); therefore, both secured and SIP secured levels can be used. The encryption level that Communicator uses can be set by means of Group Policy or by changing the PC2PCAVEncryption registry key.
• If Communicator Phone Edition is deployed, the security level should be set to secured.
If you choose to use the Exchange Management Console, create a new dial plan with the security setting SIP secured.
If you use the Exchange Management Shell, type the following command:
New-UMDialPlan -name {dial plan name} -URIType "SipName" -VoIPSecurity {SIPSecured
Secured} -NumberOfDigitsInExtension {number of digits} -AccessTelephoneNumbers "{access number in E.164 format}"
Example:
New-UMDialPlan -Name 'OCS' -NumberOfDigitsInExtension '4' -URIType 'SipName' -VoIPSecurity 'SIPSecured' --AccessTelephoneNumbers '+44020071000'
The dial plan must be enabled on the UM server. Open the Exchange Management Console, expand Server Configuration and select Unified Messaging. On the right pane, right click the UM server and select Properties.
On the UM Settings tab, add the dial plan and click OK.
A box will appear to show you how to create a new UM auto attendant.
Although it's not required, you can use the Exchange Management Console to create a new UM auto attendant for the dial plan that you just configured. You can also use a PowerShell cmdlet to create a new UM auto attendant for the previously configured dial plan.
New-UMAutoAttendant -Name {auto attendant name} -UMDialPlan {name of dial plan} -PilotIdentifierList {auto attendant phone number in E.164 format} -SpeechEnabled $true -Status Enabled
Example:
New-UMAutoAttendant -Name 'OCS Auto Attendant' -UMDialPlan 'OCS' -PilotIdentifierList '+44020071099' -Status 'Enabled' -SpeechEnabled $true
Run ExchUCUtil.ps1
The ExchUCUtil.ps1 script performs the following:
• Creates a UM IP gateway object in Active Directory for each Communications Server pool that hosts Enterprise Voice-enabled users.
• Creates an Exchange UM hunt group for each gateway. The hunt group pilot identifier will be the name of the dial plan associated with the corresponding gateway.
• Grants Communications Server permission to read Exchange UM Active Directory objects, specifically, SIP dial plans that were created in the previous task.
To run this script, open the Exchange Management Shell and navigate to the Scripts folder, which can be found under the Exchange installation directory, and type ExchUCUtil.ps1.
Verify that there are no errors in the output and check the UM IP Gateways tab in the Exchange Management Console. There you'll see the newly created gateway and hunt group.
Now, obtain a certificate for Exchange UM server from a trusted root certificate authority (CA).
Exchange and OCS will communicate using mutual TLS, so they both need a certificate from a trusted CA.
The Exchange setup installs a self-signed certificate that cannot be used with OCS, so you must obtain a new certificate. You can do so using a series of PowerShell cmdlets.
Note: To view the certificate, type Get-ExchangeCertificate in the Exchange Management Shell.
Use this command to generate the request:
New-ExchangeCertificate -GenerateRequest -Path c:\certreq.txt -SubjectName "c=UK, o=MI6, cn=e2k7.mydomain.local" -DomainName autodiscover.webmail.com, webmail.mydomain.local -PrivateKeyExportable $true
The generated text file contains the encoded certificate request that can be used on the online certificate request form.
After the certificate has been issued and saved locally, the following cmdlet will enable it for use with the Exchange UM service and HTTPS:
Enable-ExchangeCertificate -Thumbprint A9594D9632BAB0A136B2372442656CD99C13121B -Services "UM, IIS"
TIP: Open the Exchange server default web site with Internet Explorer to check there are no certificate errors.
Next, restart the Exchange unified Messaging service. Although there are two certificates (self-signed and the new one) installed, the UM service will pick the one that is not self-signed. You can search for event ID 1112 on the Exchange server application log to check which certificate Exchange is using.
You can also double check the certificate by inspecting the serial number.
Enable users for unified messaging
Before enabling users for unified messaging, I recommend filling in the telephone number information in AD. Although Microsoft recommends using E.164 normalized numbers, you can safely use a four-digit (or more) extension on the telephone number field. But I strongly recommend using E.1645 numbers on the Telephones tab (mobile number, home number, etc.).
TIP: If you use non-E.164 telephone numbers, make sure there is a rule on the Company_Phone_Number_Normalization_Rules.txt file (OCS Address Book server) to normalize the numbers.
Once the telephones are added to AD, open the Exchange Management Console to enable users for unified messaging. Then navigate to Recipient Configuration and select Mailbox.
Right-click on the user and select Enable Unified Messaging.
On the Enable Unified Messaging window, click Browse and select the UM Mailbox Policy.
Click Next -- notice that Exchange uses the extension number from AD --, then click Next again.
Finally, click Enable and then Finish.
TIP: In order to make the Call Voice Mail option available in Office Communicator, make sure the SIP URI, for example xyz@mydomain.local, is the default EUM address. The address should be in bold.
Auto-Attendant and Dial Plan Configuration
After installing the Unified Messaging server role, we need to set up a dial plan and auto-attendant on the Exchange 2007 UM server. To create a dial plan and auto-attendant follow these steps:
1. Open the Exchange Management Console.
2. Locate and click on the Unified Messaging tree node in the left pane of the console.
3. In the Action Pane, click the New UM Dial Plan link. This will launch the New UM Dial Plan Wizard.
4. In the first step of the New UM Dial Plan wizard, type a name for the dial plan. In the Number of digits in extension numbers text box enter the number of digits to use for the dial plan.
5. Now click the New button.
Now that we’ve set up the dial plan, let’s configure an auto-attendant:
1. In the Exchange Management Console, locate and click on the Unified
Messaging node in the tree in the left pane of the console.
2. From within the work pane, click UM Auto Attendants. Then click New UM Auto Attendant in the Action pane. The New UM Auto Attendant Wizard will launch.
3. From the New UM Auto Attendant Wizard screen, enter a name for the new attendant into the Name text box.
4. Click the Browse button located next to Select Associated Dial Plan. Locate the dial plan you created earlier in this section, and then click OK.
5. Back in the New UM Auto Attendant Wizard enter an extension number to use for the auto-attendant in the Extension Numbers text box.
6. Select the options to Create the auto-attendant enabled and Create the
auto-attendant as speech enabled. Then click the New button.
7. Now click the Finish button to complete the wizard.
You have now successfully created a dial plan and auto-attendant for use with Exchange 2007 UM.
Mailbox Configuration: Combining OCS and Exchange 2007 Unified Messaging
We set up and configured Exchange 2007 UM with a dial plan and auto-attendant. You now need to configure user mailboxes for UM and OCS 2007–Exchange 2007 connectivity.
Now let’s finish configuring OCS to Exchange 2007 integration. First you need to enable users for UM.
Perform the following steps:
1. Open the Exchange Management Console.
2. Locate the Recipient Configuration section in the tree and expand it.
3. In the middle pane, click to select the user you want to enable for UM.
4. In the Action pane, click Enable Unified Messaging. The Enable Unified Messaging Wizard will launch.
5. Click the Browse button to select a UM policy. Then click OK.
6. To configure a pin choose to Automatically Generate Pin to Access Outlook Voice Access. Then click the Next button.
7. In the Extension configuration section, select Automatically generated SIP resource identifier. Then click the Next button.
8. On the next page, click Enable and then click the Finish button.
You have now configured a user for unified communications. Now let’s set up the connection between OCS 2007 and Exchange 2007. This process involves several different configurations, and it can get complicated. Luckily, Microsoft has provided us with a powershell script and OCSUMUTIL to configure and link the two systems. The OCSUMUTIL creates contacts for Exchange auto-attendants and the phone number for subscriber access to Exchange unified messaging. The OCSUMUTIL also ensures that Enterprise Voice location profiles in OCS match up to an Exchange UM dial plan.
To integrate Exchange 2007 and OCS 2007 do the following:
1. From your Exchange UM server open the Exchange Management Shell.
2. From the Exchange Management Shell run the script exchucutil.ps1 which is located in the Exchange installation folder. This script performs several configuration steps, including providing OCS 2007 access to Exchange 2007 objects.
3. After running the Exchange configuration script, note the UMIPGateway.
4. From the Exchange Management Shell type Set-umipgateway –identity
name from step 3 –port 5061 and press Enter.
5. Now let’s link OCS to the Exchange environment. Log on to the Exchange UM server.
6. From a command prompt, run ocsumutil /domain:yourdomainname and press Enter.
7. Finally, restart the Unified Messaging service on your Exchange 2007 UM server and restart the Office Communications Server Front-End Service on your OCS 2007 server(s).
You have now completed the process of setting up and configuring connectivity between Exchange 2007 UM and OCS 2007.
Tools automate an Exchange UM and OCS 2007 integration
The integration of Exchange UM and OCS 2007 poses some challenges and requires detailed configuration of different utilities and contacts. Performing these tasks manually can be difficult, but certain tools, such as the Exchange UM Integration Utility (OcsUMUtil.exe), can automate the process.
RUN OcsUMUtil.exe
The final step to integrating Exchange UM and OCS 2007 is to run the Exchange UM Integration Utility (OcsUMUtil.exe). The default path on the OCS front-end server should be C:\Program Files\Microsoft Office Communications Server 2007\Server\Support.
The Exchange UM Integration Utility performs the following tasks:
• Creates contact objects for each auto attendant and subscriber access number that Enterprise voice users will need.
• Verifies that the name of each Enterprise Voice location profile matches its corresponding UM dial plan phone context.
Double-click on OcsUMUtil.exe and then onto Load Data to get started. Select a UM SIP dial plan on the left-hand side and click Add.
In the Organizational Unit (OU) check box, select an OU and click OK. In the Name box, accept the default dial plan name or type a new user-friendly name for the contact object that you are creating. In the SIP Address box, accept the default SIP address or type a new SIP address. In the Server or Pool drop-down box, select the OCS Pool where the contact object will be enabled.
In the Phone Number box, leave the default option of Use this pilot number from Exchange UM selected. This number should have been configured when the dial plan and the auto attendant were created.
In the Contact Type list, select the contact type that you want to create -- Subscriber Access or Auto Attendant -- and click OK.
You should create at least one contact for each auto attendant. The utility will display a warning if there an auto attendant object does not have a corresponding contact.
Create at least one contact for each auto attendant. Depicts the two contacts that were created -- Auto Attendant and Subscriber Access.
To verify that the contact objects have been created, open Active Directory Users and Computers and select the OU where the objects were created. Contact objects should appear in the details pane.
Verifying the results
If everything was configured correctly, the Office Communicator client will now display the Call Voice Mail option.
The Call Voice Mail option can be used to call Exchange UM with a simple click.
Other features include missed call notifications, allowing Directory Search calls to outside telephone numbers.
A cool feature of Exchange UM is Directory Search, which lets you browse the Global Address List to find a contact. If the only UM dial plan that's set up is for OCS, you'll have to configure Dialing Rule Groups to be able to make calls to telephone numbers outside of your company.
An easy way to do this is to edit the dial plan properties. Select the Dialing Group Rules tab, then add two rule groups: countrywide and worldwide. Include "*" as Number Mask and Dialed Number.
These two rule groups must also be added to the Dialing Restrictions of the UM mailbox default policy.
Reverse number lookup (RNL)
Both OCS and Exchange Server will try to connect a telephone number to a name every time a call is received or when the system sends a missed call notification.
Both Exchange Server and OCS will search Active Directory and personal Outlook contacts using reverse number lookup (RNL). Although they search the same places, the methods they use are somehow different.
OCS (Communicator) normalizes dialed numbers according to defined rules and performs RNL against the generated address book, which, in turn gets its Primary Phone Numbers from the msRTCSIP-line AD attribute and Outlook contacts. It's also important you ensure that personal contacts are normalized.
Exchange 2007 SP1 will perform RNL against other UM-enabled mailboxes in the same UM dial plan, against personal Outlook contacts and finally against the msRTCSIP-line AD attribute. The normalization logic (InternationalNumberFormat) is only applied if the calling number has the same number of digits of the user's dial plan. Otherwise, Exchange will only add a "tel:+" to the number.
What are some OCS limitations?
OCS behaves like a regular IP PBX, so the UM experience is very similar to the same type of PBX or a SIP gateway. The only limitation is fax capabilities. Users who are associated with a SIP URI dial plan cannot receive incoming faxes because incoming voice and fax calls are routed through a Mediation Server computer and the T.38 protocol is not supported.
