1. Unified Messaging Users
There is actually not an Active Directory object for
unified messaging users. Rather, the unified messaging properties are
stored in the Active Directory user account and the Exchange 2010
mailbox. Voicemail messages and fax mail messages are stored in the
user’s mailbox.
These properties can be found in the Exchange
Management Console in the properties of the user’s account in the
Recipient Configuration, Mailbox folder. Within the user account
properties, the unified messaging settings are under the Mailbox
Features tab in the properties of the Unified Messaging feature. After
navigating to the Unified Messaging feature, click the properties
button to access the feature properties.
When enabling a user for unified messaging, the
associated UM mailbox policy and extension must be specified. The link
to the mailbox policy provides a one-to-one link to the UM dial plan.
The user’s mailbox quotas apply to both voicemail
messages and fax messages. If the user’s quota settings prevent the
user from receiving email (for example, the user’s mailbox is full),
unified messaging functionality will be affected. Callers attempting to
leave a message will not be allowed to do so and will be informed that
the user’s mailbox is full.
Note
Interestingly, if a user’s mailbox is almost full, a
caller will be allowed to leave a message for the user even if that
message will cause the mailbox to exceed its quota. For example,
consider a user who only has 25 KB before exceeding the quota and is
prevented from receiving messages. A caller can leave a minute long 100
KB voice message. However, the next caller would not be able to leave a
message for the user.
Exchange 2010 unified messaging includes
several features to control the size of voicemail messages to help
control the storage impacts.
2. UM Web Services
A component that is not represented in Active
Directory is the UM Web Services. This is a web service that is
installed on Exchange 2010 servers that have the Client Access role.
The service is used for the following:
This
service requires that at least one Exchange 2010 server run the Client
Access, Hub Transport, and Mailbox Server roles in addition to the
Unified Messaging role.
Audio Codecs and Voice Message Sizes
Codec is a contraction of coding and decoding
digital data. This is the format in which the audio stream is stored.
It includes both the number of bit rate (bits/sec) and compression that
is used.
One of the following codecs is used by the Unified Messaging server to encode the messages:
Windows Media Audio (WMA)—16-bit compressed
GSM 06.10 (GSM)—8-bit compressed
G.711 PCM Linear (G711)—16-bit uncompressed
Mpeg Audio Layer 3 (MP3)—16-bit compressed
The Exchange 2010 unified messaging default is MP3.
This is a change from Exchange 2007 where the default was WMA. Although
using WMA results in slightly smaller file sizes, most people prefer
the universal nature of MP3. This enables a much larger number of
mobile devices to play voicemail messages. The Audio Codec setting is
configured on the UM dial plan on the Settings tab.
Note
A dirty little secret is that the digital
compression results in loss of data. When the data is compressed and
decompressed, information is almost always lost. That is, bits of the
conversation or message can be lost. This is a trade-off that the codec
makes to save space. This is why the G.711 codec is available, which
doesn’t compress data and doesn’t lose data but at a heavy cost in
storage.
These are stored in the message as attachments using the following formats:
Windows Media Audio (.wma)—For the WMA codec
RIFF/WAV (.wav)—For GSM or G.711 codecs
Mpeg Audio Layer 3 (.mp3)—For the MP3 codec
The choice of the audio codec affects the audio quality and the size of the attached file. Table 1 shows the approximate size of data in the file attachment for each codec.
Table 1. Audio Size for Codec Options
| Codec Setting | Approximate Size of 10-Second Audio |
|---|
| WMA | 11,000 bytes |
| G.711 | 160,000 bytes |
| GSM | 16,000 bytes |
| MP3 | 19,500 bytes |
The
G.711 audio codec setting results in a greater than 10:1 storage
penalty when compared to the WMA audio codec setting. Although the GSM
audio codec setting results in approximately the same storage as the
WMA codec setting, this comes at a cost of a 50% reduction in audio
quality. MP3 provides similar audio quality to WMA at an acceptable
file size. The ubiquitous nature of the MP3 codec makes it the
preferred choice for Exchange 2010.
Note
The .wma file format has a larger header (about 7
KB) than the .wav format (about 0.1 KB). For small messages, GSM files
are smaller. However, after messages exceed 15 seconds, WMA files are
smaller than the GSM files.
Operating System Requirements
This section discusses the recommended minimum hardware requirements for Exchange 2010 servers.
Exchange 2010 unified messaging supports the following processors:
x64 architecture-based Intel Xeon or Intel Pentium family processor that supports Intel Extended Memory 64 technology
x64 architecture-based computer with AMD Opteron or AMD Athlon 64-bit processor that supports AMD64 platform
The Exchange 2010 unified messaging memory requirements are as follows:
2 GB of RAM minimum
4 GB of RAM recommended
The Exchange 2010 unified messaging disk space requirements are as follows:
A minimum of 1.2 GB of available disk space
Plus 500 MB of available disk space for each unified messaging language pack
200 MB of available disk space on the system drive
DVD drive
As features and complexity of the applications such
as Exchange 2010 have grown, the installation code bases have grown
proportionally. Luckily, so have the hardware specifications of the
average new system, which now typically includes a DVD drive.
Exchange 2010 unified messaging supports the following operating system and Windows components:
Windows Server 2008, x64 Standard Edition
Windows Server 2008, x64 Enterprise Edition
Windows Server 2008 R2, x64 Standard Edition
Windows Server 2008 R2, x64 Enterprise Edition
Exchange 2010 unified messaging requires the following components to be installed:
Out of the box, an Exchange 2010 Unified Messaging
server is configured for a maximum of 100 concurrent calls. This is
enough to support potentially thousands of users, given that the number
of calls and voice messages per day is a fraction of the number of
users and is spread out throughout the day.
