Introduction

The primary function of the Address Book Server and related services is to provide global address list information that is retrieved from Active Directory Domain Services and make it available to clients through one of the following services:

• Address Book File Download Service, where clients such as Office Communicator and devices such as Office Communicator Phone Edition download address book files, which enable the clients to perform local address book queries, and
  
  
• Address Book Web Query Service, where clients such as Office Communicator Mobile send address book queries via HTTPS to a web service running on the Web Components Server.
  
  

If individual clients accessed the Active Directory Domain Services directly, it could impact Active Directory (AD) and network performance due to excessive LDAP queries. To make address book updates faster and more efficient, the Address Book Server generates daily address book file and address book database updates that are leveraged by the Address Book File Download Service and Address Book Web Query Service respectively.

The secondary and optional function of the Address Book Server is to convert the format of phone numbers that may in a local format (e.g. 555-0101) into the RFC 3966/ITU E.164 standardized format (e.g. +1.425.555.0101).  This conversion is referred to as phone number normalization.  Phone numbers stored in Office Communications Server (OCS) user and contact objects can be normalized by Address Book Server so they can be easily used by the OCS clients. Although it is preferable for normalized phone numbers to be entered into Active Directory, AD does not perform any phone number normalization itself. The Address Book Server normalizes phone numbers for numbers read from the OCS’ Rtc database and then writes the normalized numbers into the address book files and address book database.

Among its daily tasks, the Address Book Server generates a set of compressed full files and delta files for use by the Address Book File Download Service. These files are stored in a standard NTFS folder. The advantage of the full file and delta file generation is that it minimizes the impact of the client download. When an Office Communicator 2007 R2 or Office Communicator Phone Edition 2007 R2 client logs on to its Enterprise pool or Standard Edition Server, it uses a configured  URL to the Web Components Server Address Book location. IIS (Web Components Server) then retrieves the AB file via the virtual directory pointing to the NTFS folder. By using this URL, the client retrieves a full file the first day it connects to the server and, under most conditions, delta files on subsequent days.

Relative to OCS 2007, a key architectural improvement for Address Book services in OCS 2007 R2 is the addition of an Address Book Web Query Service for mobile clients such as Communicator Mobile 2007 R2.   Rather than download potentially large address book files, Communicator Mobile R2 clients make on-demand address book queries to the Address Book Web Query Service.

NOTE: The Address Book logic described in the following sections applies to all OCS deployments except a few special environments with either a very large number of users or a relatively volatile Directory.    For such environments, OCS Address Book logic behaves differently in a small number of aspects, resulting in slight improvements in CPU and/or network efficiency.   Exceptions for special environments are called out separately in the sections below.