Offline Address Book – Understanding

Offline Address Book – Understanding

Let’s first go back to our good old days from where the OAB concepts originated,

The offline address book is a snapshot of the Active Directory service information that is available in the global address list. Therefore, some information is available in the global address list that is not available in the offline address book. The offline address book does not contain the following items that are available in the global address list:

• Custom properties in Active Directory that an administrator has added (for example, the Employee ID of each employee)
• Organization hierarchy information
• Group membership information

Outlook must be able to access the server to obtain this
information. Therefore, if you are in cached mode and if you are working online(that is, your connection status indicates “Connected”), Outlook uses both the offline address book and the global address list to provide a complete listing of user information.  If you are in cached mode and if your connection status shows either “Disconnected” or “Offline,”you can see only the information thatis available in the offline address book.

Exchange 2003 days, Definition as per TechNet (So nothing i need to talk from my perspective 🙂 )

Offline Address Book provides offline access to directory information from the global address list (GAL) and from other address lists, each night, Exchange generates new offline address book files and places them in a special public folder, known as a system folder, for Outlook to download. The offline address book files are compressed before they are added to the offline address book system folders so that the download to Outlook is minimal. Outlook is scheduled to check periodically for new offline address book files in these system folders, and download the required files.

Exchange Server and Active Directory work together to maintain the offline address book, keeping it synchronized with changes that may be made in the directory.

Generated OAB will be stored in the public folders for the users to download. System attendant service was responsible for the generation process.

Components involved in the generation process are,

1.        Microsoft Exchange System Attendant
2.        Microsoft Exchange Information Store  
3.        Directory servers
4.        Recipient Update Service.

System attendant call the Oabgen.dll

In turn the oabgen (MAPI Application) read the Active directory and creates OAB Version 2, OAB Version 3a, and OAB Version 4 folders.

Exchange 2k3 Offline address lists are stored in two locations

1. The Active Directory

2. The Microsoft Exchange Public Folder Information Store.

Exchange 2k7/E2k10 Offline address lists can be stored in three
locations

1. The Active Directory

2. The Microsoft Exchange Public Folder Information
Store.

3. File Structure \\MBX Server \ExchangeOAB\GUID

Exchange 2013, those are stored in Arbitration mailbox and CAS

As there are numerous articles on the internet which talks about the Distribution part, Below are few for your ref,

This article is from the OAB Guru DGoldman,

http://blogs.msdn.com/b/dgoldman/archive/2006/08/25/how-exchange-2007-oab-files-are-replicated-to-a-client-access-server-for-download.aspx

Post in ur queries, lets learn from each other 🙂

Ganesh G

OAB Changes -Exchange 2013

Just a Quick look at the changes made in Exchange 2013 with respect to the Offline address book, 

Older versions of exchange had One Generation server (Mailbox server), But this is discontinued in Exchange 2013, Instead Organization mailbox or Arbitration mailboxes are brought into picture.

1. Arbitration mailbox are capable of Provisioning the OAB,
2. Only OAB Version 4 is available,
3. Outlook 2K7 SP3 RU10 and above are supported client versions to access OAB from Exchange 2013
4. Mailbox assistance service is responsible for generating the OAB
5. Offline address book is Stored in Arbitration mailbox
6. Command to get the list of arbitration mailbox which is capable to be involved in the OAB function,

 

Get-mailbox -arbitration | where {$_.PersistedCapabilities -Like “*oab*”}

 

1. “OrganizationCapabilityOABGen” marks it as a generation
2. No FDS – File Distribution service is used in CAS to pull the OAB files
3. FDS Schedule is not flexible enough
4. No more generation server

 

Quick work flow,

 

How it works in Exchange 2013 :

 

• Outlook receives OAB URL from Autodiscover and reaches designated CAS 2013 through OAB URL.
• Performs initial authentication for OAB.
• Queries Active Directory and determines the closest Organization Mailbox for the requesting user.
• Queries Active Directory again to determine the mailbox database hosting the Organization Mailbox.
• Queries the Active Manager to determine the mailbox server where the mailbox database is active (mounted).
• Proxies the request to the Mailbox server identified in step 4.
• Retrieves OAB files and passes them to the client.

 Key points to note:

During the First Request from the client

Arbitration mailbox copies the oab in to the CAS fodler,

Going further all the connections are made to the path where the oab is placed in CAS,

Then in case of rebuild use

 

Update-offlineaddressbook

 

Set-mailbox <Mailbox identifier> -arbitration -oab $true (Create a new arbitration mailbox)

 

Specify a oab for a mailbox

Set-mailbox “mbx name” -Offlineaddressbook <Oab name>

“MSexchangeuSeoab” attribute to be set

 

More detailed information is available in the below links, Feel free to post in your queries here i will try my best to answer your questions, Have a good one !

http://blogs.technet.com/b/exchange/archive/2012/10/26/oab-in-exchange-server-2013.aspx

http://exchangemaster.wordpress.com/2013/04/02/beware-full-oab-downloads-after-installing-1st-exchange-2013-server-in-existing-0710-environment/