Cisco IP Telephony: Planning, Design, Implementation, Operation, and Optimization [Electronic resources] نسخه متنی

Designing a Cisco Unity System

As discussed in the preceding sections, XYZ uses Exchange 2000 as the e-mail system for all the users in Australia. The AD forest (domain controller/Global Catalog) is fully deployed and operational in Australia. A stable working AD domain and Exchange 2000 network is the key to the success of this Unified Messaging rollout.

For the purpose of this case study, the Unity system replaces the Octel voice-mail system in Sydney. In the San Jose location, the Octel voice-mail system will stay in place and integrate with the CallManager cluster in San Jose.

Because XYZ already has a stable infrastructure, the Unity design and deployment for XYZ does the following:

Uses the existing Windows 2000 domain infrastructure to house the Unity servers

Uses the existing Exchange 2000 messaging infrastructure to service as a back-end message store

Requires installation of Unity on a separate server and not on any of the existing AD/Exchange infrastructure

The hosting team within XYZ feels comfortable extending the scope of Exchange 2000 to accomplish a Unified Messaging setup. In addition, the additional MAPI connections to the server are not expected to cause issues. MAPI functions as the primary means by which Exchange and Outlook communicate with one another.

To XYZ, whether San Jose users are also using Exchange 2000 or are still using another e-mail infrastructure with plans to move to Exchange in the future before implementing Cisco Unity is unimportant, because San Jose users will continue to use their current Octel voice-mail system. The e-mail system that is used in San Jose is important only after San Jose users start to move to Unity/Unified Messaging. For now, the voice-mail environment is not affected if San Jose users are on Exchange 2000.

Message Store Options and Sizing

The Unity server can store the messages either in G.711 or G729a format. Selecting the codec format depends on the availability of hardware resources such as hard disk sizes and hardware transcoder devices if the IPT network that is deployed uses multiple codecs. Based on XYZ's requirements, G.711 is the choice of codec to store messages on the Unity server.

Before you size the hard disk, you need to study the use of the existing voice-mail system. Investigating the system statistics from the Octel messaging system in Sydney reveals that it is sufficient to provision the Sydney user mailboxes to store 1 hour's worth of voice messages. According to Table 7-1, G.711 uses 8 KB of hard disk space to record a 1-second voice message. To store voice messages of up to 1 hour (3600 seconds), you need approximately 3600 x 8 KB, which is 28.8 MB for each Exchange mailbox.

Note

If you cannot obtain the statistics from the existing voice-mail system or no voice-mail system existed before, use Table 7-1 to calculate the hard disk size required.

XYZ corporate policy is to retain the deleted voice messages for up to 7 days. To account for this, the storage requirements per user mailbox are expanded to 56 MB.

Taking into account the 550 employees that use the Unity system in Sydney, Melbourne, and Brisbane, the additional requirement for voice-mail storage increases to a minimum of approximately 56 MB x 550 = 30 GB. From the current standards regarding disk space, this is not an issue for XYZ, because it has performed decent sizing of its Exchange 2000 environment from the beginning.

To accommodate the additional storage requirements to store the voice messages, the Exchange system administrator of XYZ will expand the storage limits on an individual mailbox basis to reflect these previously mentioned requirements.

Using the class of service (CoS) feature in Unity, a user or group of users can get additional hours of storage to retain their voice mails. You can define a separate CoS with more hours and assign this CoS to the users who need extra storage.

Sizing Unity Ports and Sessions

The number of Unity ports in a system determines the number of simultaneous callers who can call into the Unity system. Because ports or sessions are licensed components in Unity, XYZ has to pay a license for each. Therefore, proper sizing of the Unity ports/session is important to avoid paying for unneeded ports/sessions.

There are two different approaches to doing port sizing. The first approach, adopted by XYZ, is to use a port-to-user ratio of 1:20 to determine the number of ports or sessions required on the Octel voice-mail system. Using the same approach, for 550 users (including the users at Melbourne and Brisbane), 28 ports are needed on the Unity server. In Unity, you also need a few ports exclusively reserved for lighting the MWI on the handsets of IP Phones and a few ports exclusively reserved for Outcall notification purposes. Therefore, after reserving two ports each for these purposes, XYZ requires a Unity system with 32 port/sessions.

In the second approach to port sizing the Unity system, the number of ports required depends on the following parameters:

Average calls per hour to the voice-mail system

Average length in seconds

If you have an existing voice-mail system, these parameters are available in the system reports. After you have these parameters, to calculate the number of ports required, use the following formula:

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As an example, assume that a customer has on average 200 calls per hour into the system with an average length of 4 minutes (240 seconds) for voice-mail messages. Based on this information, this customer requires a Unity system with 13 ports. Taking into consideration the additional ports that must be reserved for MWI and Outcall notifications and future expansion possibilities, the customer could deploy one primary Unity server with 20 ports and one standby Unity server with 20 ports for failover situations.

Unity Server Hardware

Various Cisco-certified hardware platforms are available to run the Unity software. Selection of the hardware depends on the following factors:

Number of ports or sessions

Number of users

Number of TTS sessions

Message store location

An external message store requires less hard drive capacity on the Unity server.

A message store on the Unity server requires more hard drive capacity.

Number of slots required on the Unity system

Data protection requirements

Refer to the following URL to obtain the complete Cisco Unity Supported Platforms List:

http://www.cisco.com/en/US/products/sw/voicesw/ps2237/products_data_sheets_lis147

XYZ is opting for the higher-end servers because they offer more redundancy. The MCS-7845I has a dual power supply, and each of the power supplies is on isolated, redundant circuits that can handle a minimum of 350W.

Because the Sydney office is a regional hub site, it has good backup processes in place and usually stores the backups on a network backup server. That is why the servers do not need a DAT tape drive to perform backups.

Data Protection

System administrators commonly implement redundant array of inexpensive disks (RAID) to provide a reliable, redundant means of protecting critical data on a server. RAID is a method whereby information is spread across several disks, using techniques such as disk striping (RAID level 0) and disk mirroring (RAID level 1) to achieve redundancy, lower latency, and higher bandwidth for reading and writing and recoverability from hard-disk crashes. Six different types of RAID configurations are "available", RAID 1 is the most inexpensive method to protect the data.

At XYZ, Unity servers will use a RAID 1 array to protect the data, because voice-mail messages are essential to users and often contain sensitive and important information.

Exchange Software Licensing

The prerequisite for the Unified Messaging rollout in this case study is a fully established and working AD forest and Exchange 2000 organization. For Unified Messaging deployment using Unity, Cisco does not ship licenses to use Microsoft Exchange server software or Client Access Licenses (CALs) for accessing the Microsoft Exchange server.

Count the Microsoft Exchange 2000 server software and CAL against the corporate software licensing agreement that XYZ has with Microsoft. XYZ's corporate messaging team should verify this with the vendor management office to ensure full licensing.

If numerous Unity servers and bridges are connected to the network, a specific naming convention has to be put in place that clearly identifies the function and location of the server. This is just a naming convention and should be used only to make future troubleshooting tasks easier.

Unity Software Licensing

With the design steps covered so far, enough information is available to decide on the required number of Unity licenses. Each Unity server will have its license configured as follows. XYZ must submit a license request to Cisco Systems with the MAC address of each server in the node.

Unity version 4.0.3

600 Unified Messaging for Exchange user licenses

32 ports per server

600 VMI or Unity Inbox user licenses

16 RealSpeak TTS sessions

16 additional language licenses if not all subscribers on the Sydney Unity will use the same language

Unity Bridge 4 port license

Failover enabled (Product ID: UNITY-FOVRSVR33-UP)

Note

You obtain these license files directly from Cisco Systems. Go to the Cisco Unity Licensing FAQ site to learn how to obtain the licenses for the Unity system:

http://www.cisco.com/en/US/products/sw/voicesw/ps2237/products_qanda_item09186a0080094ce5.shtml

Refer to the following URL to get more information on how licensing works in Unity:

http://www.cisco.com/en/US/products/sw/voicesw/ps2237/products_white_paper09186a008019c743.shtml

The Cisco Unity license ties to the MAC address for the network interface card (NIC) in the Cisco Unity server that Cisco Unity will be run on. To find the MAC address on the Unity server after installing the operating system but before installing Cisco Unity, follow these steps:

Extending the Schema for Unity and Unity Bridge

As discussed in the "Microsoft Active Directory and Exchange" section earlier in this chapter, extending the AD schema is an important and mandatory task prior to installing Unity or the Unity Bridge. The extension of the AD schema allows a proper installation and integration of the Unity and Bridge systems.

Active Directory supports the use of LDAP Data Interchange Format (LDIF) scripts to extend the schema. Therefore, you need to run on the AD DC the executable called ADSchemaSetup.exe, located on the Unity installation DVD/CD-ROM, and the LDIF script files. Although there are two DCs, one in San Jose and one in Sydney, there is only one common schema. When you run the ADSchemaSetup.exe program, shown in Figure 7-6, the schema is extended and Unity-specific attributes are added into the AD. When you run ADSchemaSetup.exe, check the

Exchange 2000 or Exchange 2003 Directory Monitor and

Exchange 2000 or Exchange 2003 Bridge Connector check boxes to extend the schema required by Unity and the Unity Bridge.

Follow the guidelines exactly as addressed in the

Cisco Unity Installation Guide (discussed next) and

Cisco Unity Bridge Installation Guide , both of which are available on