Exchange 2013 coexistence | Autodiscover infrastructure | Part 1/2 | 11#23

Page 1 of 21 | 11#23 | Exchange 2013 coexistence environment | Autodiscover

infrastructure | Part 1/2

Written by Eyal Doron | o365info.com | Copyright © 2012-2015

EXCHANGE 2013 COEXISTENCE

ENVIRONMENT | AUTODISCOVER

INFRASTRUCTURE | PART 1/2 | 11#23

In the following article, we will review the subject of Autodiscover infrastructure in

an Exchange 2013 CAS environment. In a modern Exchange environment, we can

say that the Autodiscover services consider the infrastructure for all the rest of the

different Exchange infrastructure.

The Exchange Autodiscover Architecture can consider as complex and

sophisticated, especially in an Exchange 2013 coexistence environment.

My point: we need to understand the fundamentals of Autodiscover infrastructure

in Exchange 2013 CAS to be able to understand the rest of the process and the

client protocol connectivity flow that will be reviewed in the next articles in the

current article series.

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My basic assumption is that: you (my reader) are familiar with the concept of

Exchange Autodiscover and what does the Autodiscover “do”. But a quick review of

the Autodiscover infrastructure will not kill anyone.

The article is the first of two, in which we will review the subject of: Autodiscover

infrastructure in an Exchange 2013 coexistence environment. The next article

is: Exchange 2013 coexistence environment | Autodiscover infrastructure | Part 2/2

Exchange Autodiscover service | The element,

the components and charters

Exchange clients, are completely depended upon the Exchange Autodiscover

services.

Let’s start with a few observations about the Exchange Autodiscover infrastructure:






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1. The element that provides the Autodiscover information to Exchange

clients.

The element that needs to “feed” the Exchange clients with the Autodiscover

information is: “Exchange CAS server”

2. Autodiscover dynamic data\information

The Autodiscover data\information is not a “static information”. Instead, the

Autodiscover considered as a dynamic information that is generated each time for

each of the Exchange clients.

3. The element that generates the Autodiscover information.

In former versions of Exchange: Exchange 2007 and Exchange 2010, the “element”

that was responsible for generating the Autodiscover information was the

Exchange the hold the Exchange CAS server role.





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In the Exchange 2013 environment, the element that generates the Autodiscover

information is the Exchange 2013 that holds the Exchange Mailbox role. Exchange

2013 CAS server is responsible for “delivering the Autodiscover information and

Exchange Mailbox server is responsible for “creating” the Autodiscover information.

4. Autodiscover content | Exchange coexistence environment

As mentioned, the Autodiscover information considers as a “dynamic data” because

the Autodiscover data are customized for each of the different types of Exchange

client version. For example, the Autodiscover information that is provided to the

Exchange 2007 clients (an Exchange client that his mailbox is hosted on Exchange

2007 Mailbox server) is different than the Autodiscover information that will be





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provided to the Exchange 2013 clients (an Exchange client that his mailbox is

hosted on Exchange 2013 Mailbox server).

5. Autodiscover content | External versus internal Exchange client

The Autodiscover information that Exchange CAS servers provide to his client,

depend on the “physical location” of the Exchange client. In case that the Exchange

CAS server recognizes that the Exchange client considered as “internal client”, the

Autodiscover information that will be provided to the Exchange client, will include

information about internal resources.

The meaning of “internal resources” is: FQDN and URL address that include

“internal names” of Exchange servers. Internal Exchange names are not “exposed”

to the public network or in other words, an external Exchange mail client cannot

“reach” these Exchange servers.

In case that the Exchange CAS server recognizes that the Exchange client considers

as “external client”, the Autodiscover information that will be provided to the client

will include information about external resources.

The meaning of “external resources” is: information about Public facing Exchange

CAS server\s. The information will include public FQDN + URL address.

6. Autodiscover content | different mail client (mail protocols)

The Autodiscover information, which Exchange CAS server provide to his client,

depends on the “type” of the Exchange client.

The meaning of the term: ”different mail client” is related to mail clients such as:

OWA mail client, Mobile (ActiveSync) mail client and Outlook mail client. Each of this

mail clients uses different communication protocol and uses the Exchange

Autodiscover in a different way.

For example: Outlook client use protocol such as: RPC, RPC over HTTP, and MAPI

over HTTP verse’s mobile Exchange client that uses the ActiveSync protocol.

The Autodiscover information that Exchange provides two “different type of

Exchange clients” is not identical. For example: the Autodiscover information that is

provided to mobile Exchange client (ActiveSync client) is different than the

Autodiscover information that is provided to the Outlook client.








Exchange Autodiscover and Exchange 2013

coexistence environment

From the information that we are reviewing in the former section, it’s clear that the

“job” of providing Autodiscover information is not simply because, there are many

elements and factors that are involved in the Autodiscover infrastructure.

In an Exchange 2013 coexistence environment, we add an additional element to

this complex environment because in an Exchange coexistence environment, there

a couple of Exchange CAS servers that are able to provide Autodiscover

information\services.

So now, we need to understand how Exchange 2013 “fits” into the Autodiscover

infrastructure and what are the required changes or updates that need to be

implemented in an Exchange 2013 coexistence environment.





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To be able to clarify that the subject of Autodiscover infrastructure and Exchange

2013 coexistence environment, let’s divide the Exchange infrastructure into two

parts:

1. Public Exchange infrastructure and Autodiscover services

2. Internal Exchange infrastructure and Autodiscover services

The concept of: Exchange 2013 CAS as an

Autodiscover focal point

To be able to understand better the Autodiscover infrastructure in an Exchange

environment, it’s important to understand the concept which I described as:

“Exchange Autodiscover focal point”. The meaning of this concept is that the

Exchange 2013 CAS needs to be configured as the “main Autodiscover point” or the

“primary Autodiscover point” relates to the realm of:

1. The type of Exchange clients – the Exchange 2013 CAS will need to be configured

as an Autodiscover Endpoint and serve, all the types of Exchange client that

exists in Exchange 2013 CAS such as: Exchange 2013 client, Exchange 2010 client

and Exchange 2007 clients.

2. External and internal Exchange client – Exchange 2013 CAS will need to be

configured as an Autodiscover Endpoint and serve External and internal

Exchange clients.








The content of the Autodiscover file

Throughout this article and the rest of the article in this article series, we will

mention many time terms such as: Autodiscover information, Autodiscover

response, etc.

The important thing that we will need to understand is that the Autodiscover

information that is provided by the Exchange CAS server to “his” Autodiscover client

is not a “static file” but instead the opposite.





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The Autodiscover “answer” that the Exchange CAS server provides is generated

each time in a unique way for each of the separated Autodiscover client requests.

We can say that the Exchange CAS server is tailoring the Autodiscover Suit based on

the very specific measurements of his Autodiscover client.

The Autodiscover “answer” that the Exchange CAS 2013 provides to the

Autodiscover client depends on two major factors:

1. The Exchange client version

The meaning of the term “Exchange client version”, is the Exchange mailbox server

version for host the mailbox of a specific Exchange client user. For example, when

we use the term: Exchange 2007 client, the meaning is Exchange client that his

mailbox is hosted on the Exchange 2007 mailbox server.

The information that appears in the “Autodiscover answer” that is sent to the

Autodiscover client, will be customized to the specific version of the Exchange

client.

In the following diagram, we can see that the Exchange CAS 2013 is generating a

custom Autodiscover answer for each of the different Autodiscover clients. For

example, the content with the Autodiscover information that is provided to the





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Exchange 2007 client is different than the content of the Autodiscover information

that is provided to the Exchange 2013 clients.

2. The Exchange client “physical location”

The term “Exchange client physical location” relate to the location from which the

Exchange CAS server address or connect the Exchange CAS server.

The main classification for Exchange client “location” is: internal Exchange

infrastructure versus public Exchange infrastructure. The “roles” that apply to these

two separated Exchange environments are different, the charter of the

communication channel between the Exchange client, and his Exchange CAS server

is different and the Autodiscover information that will be provided to the internal

Exchange client is different from the Autodiscover information that will be provided

to external Exchange client.

An additional classification that we can use that relates to “internal Exchange

clients” is the Exchange site or the Active Directory site in which they are physically

located.





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For example: in a scenario of multiple Exchange sites, the Autodiscover information

that the Exchange CAS server provides includes a specific “Exchange site

information”. For example, in case that the Autodiscover client is an Exchange client

from Madrid site, the Autodiscover information that will be provided to the

Exchange client, will include information (URL address, host name, etc.) of Exchange

resources that are located at the Madrid site.

3. The Exchange server version

The Autodiscover content, depend on the version of the Exchange server who

provides the Autodiscover information.

For example: Exchange CAS 2013 is more “advanced” than the former version of

Exchange CAS servers and the Autodiscover information that he provides to his

clients, include additional parameters and connection methods.

For example, Exchange CAS 2013 provides additional “section” in the Autodiscover

information that described as: EXHTTP





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For these reasons, it’s important that all the Exchange clients (the different versions

of Exchange clients) will address only the Exchange CAS 2013 for Autodiscover

information and additionally, that the Outlook client software version, will be

updated to enable the Outlook client to “understand” the new language” that the

Exchange CAS 2013 use.

You can read additional information about this subject in the article: When, if and

how do you modify Outlook Providers?

4. The Exchange client type

Additional factors that affects the content if the Autodiscover information that

Exchange CAS server provide is the “type” of the Exchange client. Technically, all the

Exchange client types: Outlook, ActiveSync and OWA, use the Autodiscover

infrastructure, but the “main Autodiscover client” is Outlook and second is the

ActiveSync Exchange client.

When Exchange CAS server recognizes that the Exchange client is Outlook or a

“Mobile client” (ActiveSync), the Autodiscover information that the Exchange CAS

server generates is different because each of these clients, needs a different

parameters, etc.





http://blogs.technet.com/b/exchange/archive/2008/09/29/3406352.aspx

http://blogs.technet.com/b/exchange/archive/2008/09/29/3406352.aspx

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External and internal Exchange client |

Exchange 2013 CAS as Autodiscover Endpoint

1. Public Exchange infrastructure the concept of: “central Autodiscover

point” in Public Exchange environment, is not a new concept.

The realization of this concept is as follows: even if the Exchange public

infrastructure, consists of multiple Public facing Exchange sites, the Autodiscover

service will always be “pointed” into a single focal point.

In other words, although in theory, each of the Public facing Exchange sites, can

provide Autodiscover services, the Autodiscover will be based on a central concept





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in which one specific Public facing Exchange CAS server or to be more accurate, one

specific Public facing Exchange CAS server, will be responsible for providing the

Autodiscover services for all the Exchange clients from the different Exchange sites.

Note – there is an exception to the concept of “Exchange Autodiscover focal point”

in a public environment in a scenario of GeoDns that is based upon a multiple

“Autodiscover points”. The Exchange clients (the Autodiscover client) will be pointed

to their Public facing Exchange CAS server based on their geographical location.





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2. Internal Exchange infrastructure in an Exchange 2013 coexistence

environment.

The concept of “Exchange Autodiscover focal point” is implemented also, on the

internal Exchange environment in a scenario of the Exchange 2013 coexistence

environment. In an Exchange coexistence environment, we are using two or three

different Exchange server versions. Although since Exchange 2007 version, each of

the Exchange server “know” how to use the Autodiscover infrastructure, there a

major difference between each of the Exchange server versions (Exchange 2007,

2010 and 2013).

This “deference” relates to many “parts” and also to the Autodiscover architecture

and implementation. To be able to “unified” the different Exchange versions,

another concept which I derived as: “backward compatibility” is implemented. The

“backward compatibility” concept is implemented by using the ”newer Exchange

server version” as an Autodiscover focal point.

For example, in an Exchange site that uses an Exchange 2013 coexistence

environment which includes Exchange 2007 servers and Exchange 2010 servers,

the Autodiscover infrastructure will be “pointed” to the Exchange 2013 CAS server.





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Public Exchange infrastructure and

Autodiscover services

To be able to demonstrate the concept of Exchange Autodiscover in a Public

environment, let’s use the following scenario: An organization that has three Public

facing Exchange sites.

Site 1 and site 3 are “Public facing Exchange sites” and site 2 is an internal

Exchange site (non-public site).

The organization Public domain name is: o365info.com

The public Autodiscover record is: autodiscover.o365info.com

General concept of Autodiscover client protocol connectivity flow

When an external Exchange user looks for an Autodiscover Endpoint (Public facing

Exchange CAS server), the Autodiscover record (autodiscover.o365info.com), will

point the Exchange clients to the Public facing Exchange CAS server in site 1.

Scenario 1: User mailbox hosted on Exchange Mailbox servers is site 1.

The Autodiscover information that Exchange CAS server in site 1 will provide,

includes the information about the “site 1 public Exchange infrastructure” (URL

address with the public FQDN of the Public facing Exchange CAS server in site

1).Each of the Exchange client requests, will be accepted by the Public facing

Exchange CAS server in site 1 and will be proxied by the public facing Exchange

CAS server to “internal Exchange infrastructure” such as the Exchange Mailbox

server in site 1.

Scenario 2: User mailbox hosted on Exchange Mailbox servers is site 2

because, site 2, is not a Public facing Exchange site (Intranet site), the

Autodiscover information that Exchange CAS server in site 1 will provide, includes

the information about the “site 1 public Exchange infrastructure” (URL address

with the public FQDN of the Public facing Exchange CAS server in site 1).

Each of the Exchange client requests will be accepted by the Public facing

Exchange CAS server in site 1 and, will be proxied by Public facing Exchange CAS

server to the internal\private Exchange infrastructure in site 2.

Scenario 3: User mailbox hosted on Exchange Mailbox servers is site 3.

Because site 3, is a Public facing Exchange site, the Autodiscover information that

Exchange CAS server in site 1 will provide, includes the information about the

“site 3 public Exchange infrastructure” (URL address with the public FQDN of the








Public facing Exchange CAS server in site 3).The “site 3 Exchange client” gets the

Autodiscover information, which includes the URL address with the public FQDN

of the Public facing Exchange CAS server in site 3. From now on, the “site 3

Exchange client” will address directly the Public facing Exchange CAS server in

site 3.

Note – there are exceptions to this description such as ActiveSync clients.





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Exchange CAS 2013 – the Successor of legacy

Exchange CAS servers

In an Exchange 2013 coexistence environment, the Exchange 2013 CAS server

serves as an Autodiscover Endpoint for all the different Exchange clients.

Exchange CAS 2013 server will “replaces’” or “Inherits” the role of the legacy

versions of Exchange CAS server, such as: Exchange 2007 CAS, or Exchange 2010

CAS.

The reason for this “replacement” is because the Exchange CAS 2013 server is can

handle Autodiscover request from all the different Exchange clients: native

Exchange 2013 Autodiscover client and at the same time, Exchange CAS 2013

server, will “know what do” with an Autodiscover request of legacy Exchange clients

such as: Exchange 2007 and Exchange 2010 clients.

The opposite is not true, meaning: Exchange 2007, 2010 CAS server will not handle

correctly an Autodiscover request of “advanced Exchange clients” such as Exchange

2013 clients.





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To be able to demonstrate the concept of Public facing Exchange 2013 CAS in

Exchange 2013 coexistence environment, let’s use the following scenario: A

company, which has one Public facing Exchange sites.

Note – in the current scenario, we will demonstrate the Autodiscover connectivity

flow by using a scenario of a company that has only one Public facing Exchange

sites. I avoid from using the charters of the former scenario (a scenario in which the

company has multiple Public facing Exchange sites) to simplify the logic and the

understanding if the Autodiscover connectivity flow in a public environment + an

Exchange environment that described as Exchange 2013 coexistence environment.

The company Exchange site is based on Exchange 2013 coexistence

environment, which includes the following Exchange server versions: Exchange

2007, Exchange 2010 and Exchange 2013.

The organization Public domain name is: o365info.com

The public Autodiscover record is: autodiscover.o365info.com

The legacy Exchange 2007 namespace is: legacy.mail.o365info.com

When an external Exchange user looks for an Autodiscover Endpoint (Public facing

Exchange CAS server), the Autodiscover record (autodiscover.o365info.com), will

point the Exchange clients to the Exchange 2013 Public facing Exchange CAS server.

In most of the “best-practice implementation” of Exchange 2013 coexistence

environment, the Autodiscover information that is provided to Exchange 2010

clients, and Exchange 2013 clients are identical.

The Autodiscover information process and infrastructure that is implemented with

an Exchange 2007 client are different because the Autodiscover information will

include “pointers” to the Exchange 2007 infrastructure that will be “represented” by

the legacy namespace.








Scenario 1: Exchange 2013/2010 client (User mailbox hosted on Exchange

2013 or Exchange 2010 Mailbox server).

When the Public facing Exchange 2013 CAS server recognizes that the Autodiscover

client is Exchange 2013/2010 client, the Autodiscover information that the Exchange

2013 CAS provides, includes the “public URL address” of the different Exchange

services that in our scenario, point to the same Public facing Exchange 20123 CAS

server.

For example: the Exchange web services URL address that will appear in the

Autodiscover information will be: https://mail.o365info.com/EWS/Exchange.asmx





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Scenario 2: Exchange 2007 client (User mailbox hosted on Exchange 2007

Mailbox server).

When the Public facing Exchange 2013 CAS server recognizes that the Autodiscover

client is an Exchange 2007 client, the Autodiscover information that the Exchange

2013 CAS provides, includes URL address that will point the Exchange 2007 clients

to the Public facing Exchange 2007 CAS server.

The Exchange 2007 client, “gets the Autodiscover information” that includes the URL

address with the legacy public FQDN of the Public facing Exchange 2007 CAS server

and when the Exchange 2007 client (such as Outlook client), needs to use a specific

Exchange web service, the Exchange 2007 client will use the public legacy

namespace of the Exchange 2007 CAS.

For example: the Exchange web services URL address that will appear in the

Autodiscover information will be: https://mail.o365info.com/EWS/Exchange.asmx

The Exchange 2013 coexistence article series index page





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Exchange 2013 coexistence | Autodiscover infrastructure | Part 1/2 | 11#23