White Paper: Planning for Exchange 2007 Unified Messaging - Part 1
Dernière rubrique modifiée : 2011-09-23
Joey Masterson, Technical Writer, Microsoft Exchange Server
September 2007
Résumé
This white paper provides the general information that you need to deploy Microsoft Exchange Server 2007 Unified Messaging (UM). This includes hardware and software considerations in addition to scalability and availability information. After you have read the Unified Messaging Technical Overview white paper, read this white paper to learn about the necessary planning information that will help guarantee a successful Unified Messaging deployment.
Applies To
Microsoft Exchange Server 2007
Table of Contents
Introduction
Planning for Unified Messaging
IP Gateway Support
IP PBX Support
Cisco CallManager
Supported IP PBXs
PBX Support
Unified Messaging Server Scalability
Network Traffic
Unified Messaging Servers
IP Gateways and Unified Messaging Scalability
Unified Messaging Availability
- Load Balancing in Unified Messaging
Introduction
The Microsoft Exchange Server 2007 Unified Messaging server role enables Unified Messaging for an Exchange 2007 organization. Unified Messaging lets users access their Exchange 2007 mailbox over any telephone for e-mail, voice mail, fax messages, and calendaring and contact information.
Migrating to Exchange 2007 Unified Messaging from your current voice mail solution or implementing a new voice mail system by using Exchange 2007 Unified Messaging can be a complex process. Planning and deployment requires the coordination of telephony, IT, and Exchange administrators. This white paper discusses how to develop a plan to deploy Exchange 2007 Unified Messaging for your organization.
.gif "important") Important : |
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| We recommend that all customers who plan to deploy Exchange 2007 Unified Messaging obtain the help of a Unified Messaging specialist. This will help guarantee a smooth transition from a legacy voice mail system. Rolling out a new UM deployment or performing an upgrade of an existing legacy voice mail system requires significant knowledge of Private Branch eXchanges (PBXs) and Exchange 2007 Unified Messaging. For more information about who to contact, see the Microsoft Exchange Server 2007 Unified Messaging (UM) Specialists Web site. |
Planning for Unified Messaging
When you plan your Exchange 2007 Unified Messaging deployment, you must consider design and other issues that may affect your ability to reach your organizational goals when you deploy Exchange 2007 Unified Messaging.
Generally, the simpler the Unified Messaging topology, the easier Unified Messaging is to deploy and maintain. Install as few Unified Messaging servers and create as few Unified Messaging objects in the Active Directory directory service as you have to support your business and organizational goals. Large enterprises that have complex network and telephony environments, multiple business units, or other complexities will require more planning than smaller organizations that have more straightforward Unified Messaging needs.
There are many areas that you must consider or evaluate to be able to successfully deploy Unified Messaging. You must understand the different aspects of Exchange 2007 Unified Messaging and each component and feature so that you can plan your Unified Messaging infrastructure and deployment appropriately.
Allocating time to plan and work through these issues will help prevent problems when you deploy Unified Messaging in your organization.
The following are some areas that you should consider and evaluate when planning for Exchange 2007 in your organization:
Your business needs for Unified Messaging
Your telephony network and your current voice mail system
Your current data network design
Your current Active Directory environment
The number of users who you must support
The number of Unified Messaging servers you will need
The storage requirements for users
The placement of IP gateways, telephony equipment, and Unified Messaging servers
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Who Should Read This White Paper
Information technology and telephony professionals who are responsible for planning and designing Exchange messaging systems that include Exchange 2007 Unified Messaging for their companies should read this white paper. Such professionals may include the following:
System architects Responsible for designing the overall server infrastructure, developing server deployment strategies and policies, and contributing to networking connectivity design.
Information technology managers Technical decision makers, who also manage the Information Technology staff responsible for the infrastructure, the desktop and server deployment, and server administration and operations across sites.
Systems administrators Responsible for planning and deploying technology across Microsoft Windows servers and evaluating and recommending new technology solutions.
Messaging administrators Responsible for implementing and managing organizational messaging.
Telephony administrators and consultants Responsible for implementing and managing an organizations telephony infrastructure.
IP Gateway Support
Integrating Exchange Server 2007 Unified Messaging with your company's telephony network is one of the most significant deployment challenges when you deploy Unified Messaging. Interoperating with Exchange 2007 Unified Messaging will depend on your specific PBX or IP PBX configurations and may also require that you install IP gateways, purchase additional PBX hardware, or configure and enable features on your PBXs or IP PBXs. In some cases, the PBX may cause reduced functionality or limitations in the Unified Messaging features. This is especially true for IP PBXs. This section discusses the manufacturers and specific models of IP gateways that you can configure to support Exchange 2007 Unified Messaging.
| Important : |
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| We recommend that all customers who plan to deploy Exchange 2007 Unified Messaging obtain the assistance of a Unified Messaging specialist. They will help make sure that there is a smooth transition to Exchange 2007 Unified Messaging from a legacy voice mail system. Performing a new deployment or upgrading a legacy voice mail system requires significant knowledge about PBXs and Exchange 2007 Unified Messaging. For more information about how to contact a Unified Messaging specialist, see the Microsoft Exchange Server 2007 Unified Messaging (UM) Specialists Web site. |
There are many models and manufacturers of PBXs, IP gateways, and IP PBXs. However, there are basically two configurations for IP gateway devices:
IP PBX A single hardware device.
PBX (legacy) and an IP gateway Two separate hardware devices.
Dialogic and AudioCodes IP gateways have been tested and are supported for Exchange 2007 Unified Messaging.
For more information about the latest support and configuration information available for AudioCodes IP gateways, see the Microsoft Exchange Server 2007 UM Resource Page.
For more information about the latest support and configuration information for Dialogic IP gateways, see the Dialogic Documentation Web site.
Notes
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Correctly configuring IP gateways for your organization is a difficult deployment task that must be completed to successfully deploy Exchange 2007 Unified Messaging. To help answer questions and give you the most up-to-date IP gateway configuration information, see the Telephony Advisor for Exchange Server 2007 Web site. This Web site gives you IP gateway configuration notes and files that you must have to correctly configure your organization's IP gateways to work with Exchange 2007 Unified Messaging.
Exchange 2007 Unified Messaging relies on an IP gateway that can receive incoming calls from a legacy PBX or on an IP PBX that can receive incoming calls and then correctly forward those incoming calls to a Unified Messaging server in your organization.
| Important : |
|---|
| We recommend that all customers who plan to deploy Exchange 2007 Unified Messaging obtain the assistance of a Unified Messaging specialist. A Unified Messaging specialist helps you make sure that there is a smooth transition to Exchange 2007 Unified Messaging from a legacy voice mail system. Performing a new deployment or upgrading a legacy voice mail system requires significant knowledge about PBXs and Exchange 2007 Unified Messaging. For more information about how to contact a Unified Messaging specialist, see the Microsoft Exchange Server 2007 Unified Messaging (UM) Specialists Web site. |
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IP PBX Support
An IP PBX is a telephone switching system inside an enterprise that switches calls between Voice over IP (VoIP) users on local lines and lets all users share a certain number of external telephone lines. The typical IP PBX can also switch calls between a VoIP user and a traditional telephone user, or between two traditional telephone users much like a conventional PBX does. With a conventional PBX, you must have separate networks for voice and data communications. One of the main advantages of an IP PBX is that it uses converged data and voice networks. This means that network access, VoIP communications, and traditional telephone communications are all possible by using a single line to each user. Like a traditional PBX, an IP PBX is typically owned by an organization.
There are many manufacturers of IP PBXs. However, for an IP PBX to interoperate with Exchange 2007 Unified Messaging, the IP PBX generally must support the following:
Session Initiation Protocol (SIP) over Transmission Control Protocol (TCP)
T.38 for fax
However, even if a specific IP PBX supports SIP over TCP and T.38, there is no guarantee that the IP PBX will successfully interoperate with Exchange 2007 Unified Messaging.
Correctly configuring your organization's IP PBXs is a difficult but required deployment task. To help answer questions and give you the most up-to-date IP PBX configuration information, see the Telephony Advisor for Exchange Server 2007 Web site. This Web site gives you IP PBX configuration notes and files that are required to correctly configure your organization's IP PBXs to work with Exchange 2007 Unified Messaging.
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Cisco CallManager
Cisco CallManager tracks all active VoIP network components. These components include telephones, gateways, conference bridges, voice mail boxes, and other components. Cisco CallManager frequently uses the Skinny Client Control Protocol (SCCP) as a communications protocol for signaling the hardware endpoints of the system, such as IP-based telephones, or it uses SIP to pass call signaling to IP gateways. Cisco CallManager evaluates numbers that are dialed and starts IP gateway events to receive or send calls to the Public Switched Telephone Network (PSTN).
Exchange 2007 Unified Messaging has been tested for use with Cisco CallManager version 5.x. If you have Cisco CallManager 5.x on your network, you will be able to connect Exchange 2007 Unified Messaging servers directly to CallManager without the requirement of an IP gateway. Many of the features that are included with Exchange 2007 Unified Messaging are fully functional with Cisco CallManager 5.x. However, the Message Waiting Indicator (MWI) feature does not work and faxing does not work because the T.38 faxing protocol is not supported by Cisco CallManager.
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| We do not recommend Cisco CallManager 4.x for use in Exchange 2007 Unified Messaging production environments. |
There are various limitations related to Cisco CallManager 4.x. Therefore, we recommend that you use it only for test or lab environments. The limitations are as follows:
Call transfers do not work. Therefore, the auto attendant feature cannot transfer incoming calls.
Faxing does not work.
Accessing a user's voice mail and e-mail messages from a telephone is unreliable.
The Message Waiting Indicator (MWI) feature does not work.
Notes
Exchange 2007 Unified Messaging does not include support for the Message Waiting Indicator (MWI) feature. However, you can obtain information about how to enable this feature by visiting the Geomant Web site. This third-party application extends Exchange 2007 Unified Messaging to include the Message Waiting Indicator (MWI) and Short Message Service text messaging capability.
Notes
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To configure Cisco CallManager 4.x for your test environment, perform the following tasks:
Configure it to send SIP messages to port 5061 on the Unified Messaging server.
Create a SIP Trunk and an associated route pattern.
Supported IP PBXs
Cisco CallManager version 5.0 has been tested for direct IP interoperability with Exchange 2007 Unified Messaging. However, a listing of the IP-PBXs that are supported is available on the Telephony Advisor for Exchange Server 2007 Web site.
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PBX Support
A PBX, sometimes known as a telephone switch or telephone switching device, is a device that connects office telephones in a business to the public telephone network. The central functions of a PBX are to route incoming calls to the appropriate extension in an office, and to share telephone lines between extensions. Users of the PBX share a certain number of outside lines for making telephone calls external to the PBX.
Most medium-size and larger organizations use a PBX because it is much less expensive than connecting an external telephone line to every telephone in the organization. In addition, it is easier to call someone who has an extension number within the same PBX because the number that you dial is typically merely three or four digits.
Correctly configuring your organization's PBXs is frequently one of the more difficult deployment tasks because PBXs are very different and their functionality depends on the PBX model and software that is installed. To help answer questions and give you the most up-to-date PBX configuration information, see the Telephony Advisor for Exchange Server 2007 Web site. This Web site gives you PBX configuration notes and files that are required to correctly configure your organization's PBXs to work with Exchange 2007 Unified Messaging.
In many organizations today, accessing e-mail and voice mail is very important to the success of daily operations. To provide continuous access to e-mail and voice mail, you must correctly plan and implement a solution for your Microsoft Exchange Server 2007 organization that will help guarantee the availability of the servers that provide these services.
To provide a highly scalable and available solution in Exchange 2007 Unified Messaging, you must understand how the Unified Messaging components can be scaled to support your users. You must also understand how to implement a solution that will make your Unified Messaging servers highly available.
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Unified Messaging Server Scalability
Scalability is defined as the capability to increase resources to increase the capacity of a given service. There are two types of scalability that can be used to increase the capacity of Unified Messaging servers in your organization: horizontal and vertical. In Exchange 2007 Unified Messaging, when you scale vertically, you add hardware resources to a single Unified Messaging server or multiple Unified Messaging servers, for example:
Adding more hard disk space for message storage
Increasing the speed or number of processors
Increasing the amount or speed of RAM
Increasing the number of network adapters or increasing the number of local area network (LAN) ports in a single network adapter
In Unified Messaging, when you scale horizontally, you install the Unified Messaging server role on new Unified Messaging servers and add more Unified Messaging servers to a dial plan to increase the number of incoming concurrent calls that the system can accept. To scale your Unified Messaging environment horizontally, you can also increase the number of IP gateways. This increases the number of ports that are available to be used for incoming calls.
Exchange 2007 Unified Messaging provides an efficient and simple deployment model that is highly scalable without increasing the complexity of the deployment. There are many deployment models for Unified Messaging in your organization. But the recommended deployment model for Unified Messaging is to centralize your Unified Messaging servers. All the available deployment options for Unified Messaging have several steps in common that are required to create a scalable system to support many Unified Messaging users. These steps are as follows:
Provision PBX lines The first step in building a highly scalable UM solution is to provision PBX lines.
Organize channels After you have provisioned PBX-based voice channels, you can organize the channels as hunt groups.
Deploy IP gateways After you have organized your voice channels as hunt groups, you will need to deploy your IP gateways. The channels that you organized as hunt groups should end at the IP gateways that you will be deploying. IP gateways are used with a legacy PBX to convert the circuit-switched protocols found on a telephony network to IP-based packet-switched protocols.
Add more Unified Messaging servers to a dial plan If you must increase the number of calls that can be handled by Unified Messaging, you can install and configure additional Unified Messaging servers and add them to a dial plan. In most cases, IP gateways will use DNS to load balance between the existing Unified Messaging servers and the additional Unified Messaging servers.
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Network Traffic
Every incoming call that is received from an IP gateway will generate IP-based network traffic and will consume some amount of your available network bandwidth. Because all the IP-based calls are routed directly to your Unified Messaging servers from the IP gateways on your network and this IP-based network traffic consumes some available bandwidth, you should follow these recommendations and guidelines:
Perform an analysis of the network traffic to determine current usage patterns and find any potential issues. On most networks, bandwidth demand is not evenly distributed throughout business hours.
Put your PBXs physically close to your IP gateways.
Put your IP gateways and your Unified Messaging servers close together.
Put your Unified Messaging servers and IP gateways on the same subnet.
Put your Unified Messaging servers and IP gateways on the same virtual local area network (VLAN).
Put your Unified Messaging servers close to other computers that have Exchange 2007 server roles installed, including Mailbox, Hub Transport, and Client Access servers.
End your Wide Area Network (WAN) connections close to where your telephony equipment is located.
In branch office scenarios or over WAN connections, use the G.723.1 codec instead of the G.711u or G.711A codec to minimize the network traffic that is passed between your IP gateways and your Unified Messaging servers.
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Unified Messaging Servers
Generally, Unified Messaging scalability is determined by the number of concurrent calls. By default, a single Unified Messaging server can accept a maximum of 100 concurrent voice calls and 100 concurrent fax calls. These calls can be either incoming or outgoing and can be generated when a user leaves a voice mail message, when an Outlook Voice Access user accesses their Exchange 2007 mailbox, or by a user who uses the Play on Phone feature to listen to their voice messages. Although the number of concurrent calls is an important factor to consider when you build a scalable Unified Messaging infrastructure, you must also determine the best codec to use to encode the voice messages and the types and number of users who you have to support.
Number of concurrent calls Although, by default, a Unified Messaging server can accept 100 concurrent voice messages and 100 concurrent fax messages, a single Unified Messaging server can be configured to accept a maximum of 200 concurrent voice messages and 200 concurrent incoming fax messages. When you increase the number of concurrent connections on a single Unified Messaging server, more system resources are required than if you decrease the number of concurrent connections. It is especially important to decrease this setting on low-end, slower computers on which the Unified Messaging server is installed. Performance counters are available and the Get-UMActiveCalls cmdlet can also be used to monitor the current number of concurrent calls that are connected to a Unified Messaging server.
If the number of concurrent calls required by your organization is larger than the number that is supported by a single Unified Messaging server, you can scale horizontally and increase the capacity of concurrent calls by installing the Unified Messaging server role and then adding the Unified Messaging server to a dial plan.
Voice mail storage codec The term codec is a combination of the words coding and decoding and relates to digital data. A codec is a computer program or software that transforms digital data into an audio file format or streaming audio format.
In Exchange Unified Messaging, there are two general types of codecs: the codec that is used between IP gateways and the codec that is used to encode voice messages. The Windows Media Audio (WMA), Group System Mobile (GSM) 06.10, and G.711 Pulse Code Modulation (PCM) Linear audio codecs are used to create .wma and .wav audio files for voice messages. However, the file type that is used depends on the audio codec that is used to create the voice message audio file. In Exchange Unified Messaging, the .wma audio codec creates .wma audio files and the GSM 06.10 and G.711 PCM Linear audio codecs produce .wav audio files. Therefore, depending on the codec that is used, an audio file in .wma or .wav format is sent together with the e-mail message to the intended voice mail recipient. The size of Unified Messaging voice messages depends on the size of the attachment that holds the voice data. Additionally, the size of the attachment depends on the following factors:
The duration of the voice mail recording
The audio codec that is used
The audio file storage format
The following figure illustrates how the size of the audio file depends on the duration of the voice mail recording for the three audio codecs that you can use in Unified Messaging.
Notes
In this figure, the average length of a call-answered voice message is approximately 30 seconds.
Audio file size
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The sample bit rate (bit/sec) and compression properties for each audio codec that is used in Unified Messaging are as follows:
WMA – 16-bit – compressed file
G.711 – 16-bit – uncompressed file
GSM 06.10 – 8-bit – compressed file
If you use the WMA codec, we estimate that each Unified Messaging server can handle 60 to 75 concurrent IP-based calls. This estimate is based on the assumption that 14 percent of all the IP-based calls arrive during the single busiest hour of a day. Based on these two assumptions, and assuming that your users access their voice messages frequently by using Outlook Voice Access, we estimate that each Unified Messaging server can support between 2,000 and 10,000 users.
Generally, you should allow for the following number of concurrent calls per Unified Messaging server:
60 if the default dial plan codec is WMA
75 if the default dial plan codec is GSM
Types of users There are two types of users who access the Unified Messaging system: authenticated users and unauthenticated users. These two types of users consume Unified Messaging resources. When you build a scalable Unified Messaging environment, you must consider the effect that these users will have and the resources that each of these users will consume.
Authenticated Authenticated users are UM-enabled and can access their mailbox by using Outlook Voice Access. Authenticated users consume Unified Messaging server resources in several ways, including by directly calling in to a subscriber access number, logging on to their mailboxes, accessing their messages, calendar, contacts or the directory, and by using a Unified Messaging server to play voice messages over a telephone using the Play on Phone feature. They can also indirectly consume resources by transferring a call, sending a voice message, or calling a user's extension number and leaving a voice message or sending a fax.
Unauthenticated Users who call in to a Unified Messaging auto attendant or call in to a subscriber access number but do not log on to their mailbox are unauthenticated callers. However, Unified Messaging resources are used to service their requests. Every time that a caller calls in to a UM auto attendant or uses a subscriber access number but does not log on to their mailbox, they still consume resources by transferring a call, sending a voice message, transferring to another auto attendant, transferring to another telephone number, or listening to recorded audio prompts.
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IP Gateways and Unified Messaging Scalability
Unified Messaging relies on the ability of the IP gateway to translate TDM or telephony circuit-switched based protocols, such as Integrated Services Digital Network (ISDN) or QSIG, from a PBX to protocols based on VoIP or IP, such as SIP, RTP, or T.38 for real-time facsimile transport.
IP gateways are available from multiple manufacturers in sizes and models that range from 4 ports to 32 ports. You can deploy as many IP gateways as necessary to provide for capacity and fault tolerance. If the number of calls or ports that are required is larger than the number of calls or ports that are supported by a single IP gateway, you can scale horizontally and increase the number of calls that can be accepted or the number of ports by installing and configuring additional IP gateways, creating the UM IP Gateway object, and configuring the appropriate hunt groups to support your environment.
It is equally important to match the number of IP gateways that you have in your environment with the number of Unified Messaging servers that are available. For example, you should not configure 10 IP gateways that are each connected by using a T-1 line to a single Unified Messaging server. This would mean that the Unified Messaging server would have to support 240 concurrent incoming calls. You should consider this and scale your IP gateways to Unified Messaging servers appropriately.
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Unified Messaging Availability
Minimum uptime requirements may vary among organizations. However, every organization wants to achieve a high level of uptime, especially for their telephony system. An organization's telephony system is frequently business-critical and must be highly available to users. One of the factors that you must consider when you deploy a Unified Messaging system is the ability for the system to provide services for users when a key component such as a Unified Messaging server or an IP gateway becomes unavailable.
Unified Messaging servers In Exchange 2007, Unified Messaging is designed to run as a service and a worker process. This means that if the service is using lots of system resources or has become unresponsive, the worker process can be recycled. The UM worker process is responsible for dealing with outages in Mailbox servers, Hub Transport servers, and domain controllers. If, for example, a Mailbox server for a user is unavailable, the Unified Messaging server will continue to accept calls on behalf of the user. However, the user's custom greeting will not be played. Instead, a standard greeting will be used for calls to that user. Additionally, if the Hub Transport server is unavailable, the Unified Messaging server will continue to accept calls and queue the calls, depending on how you have configured the queuing limit, until the Hub Transport server is available. However, in a situation where all domain controllers are unavailable, the Unified Messaging server will be unable to accept calls.
Unified Messaging deployments can be made more flexible and more available by adding Unified Messaging servers to a single dial plan in an N+1 configuration. This means that if you need two Unified Messaging servers, you would install and configure an additional Unified Messaging server so that you would have a Unified Messaging server to replace a Unified Messaging server that is failing or must be taken offline.
When you add multiple servers to a single dial plan, the IP gateway will try to connect to a Unified Messaging server that is listed in the configuration on the IP gateway by IP address, or by fully qualified domain name (FQDN) for TLS deployments. If the Unified Messaging server is unavailable, the IP gateway will try to connect to the Unified Messaging server again after 5 seconds. If there is no response from the Unified Messaging server, the IP gateway will try to connect to the next Unified Messaging server in the list that is configured on the IP gateway.
IP gateways If you want to create redundancy to provide for IP gateway availability, you should add multiple IP gateways in an N+1 configuration. This means that, if you need two IP gateways, you would install and configure an additional IP gateway so that you would have an IP gateway to replace an IP gateway that is failing or must be taken offline.
You must configure your PBX so that it will send the incoming calls that it has received to different IP gateways. After you configure the PBX, the PBX will detect a failure or no signal or that a port is not answering calls. This will enable the PBX to redirect calls to an IP gateway that can answer incoming calls.
The IP gateways that are supported by Unified Messaging can be configured to route calls to Unified Messaging servers in a round-robin manner. To enable an IP gateway, you must configure each IP gateway with the IP addresses for your Unified Messaging servers that will be answering calls from the IP gateway. These are the Unified Messaging servers that are associated with the same dial plan as the UM IP Gateway object that logically represents the IP gateway. This will enable all the UM IP gateways to forward incoming calls to the Unified Messaging servers that are associated with the same dial plan. Then, if an IP gateway fails, the PBX will send the call to an IP gateway that can answer the call. The IP gateway, in turn, will forward the call to a Unified Messaging server within the same dial plan. If the call is sent to a Unified Messaging server that is not available, the IP gateway will try to contact the Unified Messaging server again. If it is unsuccessful in contacting the Unified Messaging server, it will then use the next Unified Messaging server in the list that is configured on the IP gateway to answer the call. However, not all supported IP gateways can be configured to support both load balancing and to be able to detect if a server has been taken offline or is failing.
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Load Balancing in Unified Messaging
Exchange 2007 Unified Messaging deployments can be made more flexible by deploying multiple Unified Messaging servers to a single dial plan to balance the load of incoming calls. The IP gateways that are supported by Unified Messaging can be configured to route calls in a round-robin manner to balance the load between multiple Unified Messaging servers that are within a dial plan.
Round robin is a method for distributing the workload among multiple servers. However, round robin does not by itself enable an IP gateway to detect a server failure. If one of the Unified Messaging servers fails and if the IP gateway cannot detect that a Unified Messaging server is unavailable, the IP gateway will continue to send incoming calls to the Unified Messaging server until you detect the failure and remove the server from the dial plan. After you remove the Unified Messaging server from the dial plan, you should also remove the IP address or FQDN for the Unified Messaging server from the configuration on the IP gateway.
Unified Messaging does not use round-robin DNS or Network Load Balancing (NLB) to distribute incoming calls. Round-robin DNS can be used on multi-homed computers and can be used to distribute the load for other services, but not for Unified Messaging. NLB is used with other services to distribute client requests and to automatically detect whether a server is unavailable, and then to redistribute other client requests to the remaining server. However, it also cannot be used with Unified Messaging. The only way to distribute or balance the load between Unified Messaging servers in a dial plan is to configure the IP gateway to use the IP addresses or FQDNs of the Unified Messaging servers in the dial plan. The IP gateway will use the list to distribute the load across all the Unified Messaging servers in the dial plan and can also detect a server failure if the IP gateway supports this functionality.
Another way to load balance your Unified Messaging deployment is to configure PBX hunt groups to connect to multiple IP gateways and then configure the hunt groups to load balance across the IP gateways.
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Conclusion
This white paper outlines the general information that you must have to plan your Unified Messaging deployment for Exchange Server 2007. After you have read White Paper: Unified Messaging Technical Overview and this white paper, you should be prepared to plan your Unified Messaging deployment.
Informations supplémentaires
For more information about the technical concepts for Unified Messaging, see White Paper: Unified Messaging Technical Overview.
For more information about how to deploy Unified Messaging, see White Paper: Deploying Exchange 2007 Unified Messaging - Part 2.
For more information about how to manage Unified Messaging, see White Paper: Managing Exchange 2007 Unified Messaging - Part 3.
For more information about educating users for Unified Messaging, see White Paper: Educating Information Workers About Unified Messaging - Part 4.
For more information about how to test and troubleshoot your Unified Messaging deployment, see White Paper: Testing and Troubleshooting Unified Messaging - Part 5.
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