The autodiscover information part 04#36

of 19 | The Autodiscover information | Part 04#36
Written by Eyal Doron | o365info.com | Copyright © 2012-2015
The Autodiscover information | Part
04#36
Exchange Autodiscover is relating to “information” from three different
perspectives:
 Autodiscover is the tool that Exchange client use for getting about the
Exchange infrastructure.
 Autodiscover is the method in which Exchange CAS server provides
information to his Exchange clients.
 Autodiscover is the information itself.

In the following article, I would like to zoom in on the aspect of the Exchange CAS
server as the source for information and the Autodiscover process that enables the
Exchange client to retrieve the required information.
THE ARTICLE CONTENT
In this article, we continue our “first glimpse” at the Exchange Autodiscover
infrastructure.
We will review subjects such:
Q1: How to find the source of information?
Q2: What is the way that the client uses for locating the element that will provide
them the required “Autodiscover information”?
Q3: What does the Autodiscover respondent include?
Q4: When the server responds with an answer (Autodiscover response), what is the
content of this “answer”
Q5: How the Autodiscover information is created?
What is happening behind the scenes on the Exchange CAS server who need to
generate the Autodiscover response

Q6: What are the Exchange web based service?
What is the meaning of -“Exchange web services” and what are the available
Exchange web services
What is the “Exchange information”?
Exchange client, need a lot of information about the Exchange infrastructure.
If we want to use a metaphor for describing the “role” of the Exchange CAS server
as an information provider, we can relate to the Exchange CAS server as a “door to
the information.”

In the following diagram, we can get a general concept about the “type of
information” that provided by the Exchange server.

1. Exchange web based services
 The exchange provides many types of services to his client, most of this
“Exchange service” consider as web services.
Exchange client’s access the “Exchange web service”, by using a URL address
that includes the FQDN of the host (Exchange CAS server) that provides the
specific web service.
 The information about the available Exchange web services is “passed” to the
Exchange client as part of the Autodiscover process.
 Each time that the Exchange client needs to use a specific Exchange web
service, the client will use the information (the Autodiscover infrastructure)
that was sent by the Exchange CAS server.
 The Exchange CAS server is the information provider and, at the same time,
the elements that provide different web services.
2. Configuration settings required for creating a new Outlook mail profile.
The “other type of information” that is required for Exchange client such as Outlook,
is the configuration setting’s details, that are required for creating a new Outlook
mail profile.
The creation of a new Outlook mail profile and especially an Outlook Anywhere
profile, require a lot of configuration settings.
Theoretically, these details can be fulfilled manually by the user, but, in a modern
Exchange environment such as Exchange 2013 that uses a session ID, instead of
using the Exchange CAS server name, the option of -“creating a new Outlook mail
profile manually” is barely possible.

3. Other
Under the “other” section, we can add additional types of details and information
that provided to the Exchange clients.
Technically, there is no limitation or restriction to the amount of data, that can be
included in the “information package,” that is provided by the Exchange server.
The Autodiscover information that is provided by the Exchange CAS server can
include a new and updated type of information that was not provided by former
versions of Exchange servers.
The “catch” is that as long that the client knows how to “read” and relate to the data
that is included in the Autodiscover response it’s O.K.
Autodiscover process | Client versus server

If we want to encapsulate to one-sentence meaning of Exchange Autodiscover, we
can say that: it’s all about the relationships of client and server.
In the current article, and in the next articles of this series, we will use different
terms for describing this “client and server relationships”:
The client side
We can relate to the client as: “client”, as a “Mail client” or, as an “Exchange client”.
When we relate to the specific process of Autodiscover, we will relate to the
Exchange client as –“Autodiscover client”.
The server side
As mentioned, the Exchange architecture includes five types of server roles, but
99% of the time when we mention the term: “server” or “Exchange server” the
meaning is the Exchange server who holds the CAS (Client Access server) role.
When we relate to the Autodiscover process, the terms that will be used for
describing the “server-side side element” that provides the Autodiscover services
could be:

 Autodiscover Endpoint
 Destination server
 Destination host
 Potential Autodiscover Endpoint
 Final Autodiscover Endpoint.
The reason for using the term “Potential” is because, when the Autodiscover client
addresses the “destination host”, he doesn’t know if this is the “right host” that can
help him to complete the authentication process, provide the Autodiscover
information and so on.
In other words -the Autodiscover client “hope” that the Autodiscover Endpoint that
he tries to connect is the correct or the “last hope” in the Autodiscover process
round trip.

Autodiscover query and Autodiscover response
The Autodiscover includes many aspects such as a protocol that is used by the
client to locate their “source of information” (Exchange CAS server).
The other aspect is the part in which the Autodiscover reach the required
Autodiscover Endpoint successfully completes all the authentication and
identification steps and gets into the point and which the client asks for the
required information, and the server provide this information.

The request or the query that he Exchange client sends, described as Autodiscover
request.
The “answer” of the server who includes the requested information described as
Autodiscover response.
In my mind, the Exchange CAS server is some kind of superman that came to save
the world in his hour of distress.
What does the Autodiscover response include?

The Autodiscover response that provided by the Exchange CAS server (the
Autodiscover Endpoint), is dynamically generated and sent to the Exchange client
(the Autodiscover client).
The Autodiscover response that’s sent to the Autodiscover client includes two main
parts:
1.Configuration settingsinstructions for Outlook + Outlook Anywhere mail profile
The task of creating a new Outlook mail profile can be considered as a complicated
task because the Outlook mail profile such as Outlook Anywhere mail profile,
includes many different parameters that relate to the protocol type, the
authentication protocol, the method to the server identification and the name of
the required Exchange CAS server.
In case that the Exchange infrastructure is based on Exchange 2013, the task of
“getting the name of the Exchange CAS server” become even more complicated
because in an Exchange 2013 environment, the mail client doesn’t use the

Exchange CAS server name but instead, use a session ID that is sent by the
Exchange CAS server.
2.Information about Exchange services
The other “type of information” that is included in the server Autodiscover responds
is an information about each of the available Exchange web services.
The information includes: the service name, the name of the Exchange server who
provides the service, and the URL that the Exchange client will need to use in case
he wanted to access a specific service.
How does the Autodiscover information is created?
The Autodiscover information that is provided by Exchange server considers as a
dynamic content that is “regenerated dynamically,” each time that an Exchange
client asks for the Autodiscover information.

The reason for the “dynamic nature” of the data is because Exchange infrastructure
and especially Office 365 and Exchange Online infrastructure could consider as very
dynamic.
The meaning of – “dynamic” is that in each mint or hour, there could be changes in
the Exchange infrastructure such as – Exchange CAS servers that are not available
for any more verses new Exchange CAS servers.
Other examples could be changes or updates of Exchange CAS servers that
provide a specific web service.

The Autodiscover response format
The “answer” (the Autodiscover responds) that the Exchange CAS server provides, is
implemented as data in XML format.
The Autodiscover process is based on a method, on which the Autodiscover client
request from the Exchange CAS server a specific file named
– autodiscover.xml or autodiscover.svc
Apparently, we can think that autodiscover.xml is a static file that is stored in the
Autodiscover folder on the Exchange CAS server but in reality, there is no such file.
The Autodiscover response that is sent as an “answer” (the request for the
autodiscover.xml file) is actually a dynamic content that is created on a real time
(based on the type of the mail client, the current Exchange infrastructure
information and so on).
Autodiscover infrastructure | Recap

After we have to review the basic components of Autodiscover, let’s recap some of
the concepts of Autodiscover infrastructure.
 The “element” the described as the “source of information” is the Exchange
CAS server. The main purpose of the Autodiscover process is to enable the
Exchange clients, to find the “right Exchange CAS server” that will be able to
provide them the required Autodiscover information.
 When we describe a subject that refers to the Exchange Autodiscover
infrastructure, we relate to the Exchange client as a – Autodiscover client and
relate to the Exchange CAS server as: Autodiscover Endpoint.
 The Autodiscover Endpoint (the Exchange CAS server) provides to the
Autodiscover clients the information using an XML file named:
autodiscover.xml
 The autodiscover.xml includes information that is needed for Exchange client
such as Outlook, for creating a new mail profile and additional information all
the available Exchange services that exist in the Exchange forestorganization.
 Exchange services are web-based services and for this reason, the
information about Exchange services is implemented by providing the URL of
the Exchange Online services.
Autodiscover – client versus server perspective

The Autodiscover infrastructure is built from two parts: the client side and the
server side.
The Autodiscover service in the “client side” enables to the Exchange client to
perform tasks such as:
 Decide about the preferred Autodiscover method.
 In an Active Directory environment – create a Query the local Active Directory
(using the LDAP protocol) and ask for a list of Autodiscover Endpoint (available
Exchange CAS servers).
 In a non-Active Directory environment – communicate the Autodiscover
Endpoint using HTTPS and HTTP protocol.
 Get the server certificate of the Autodiscover Endpoint and provide the user
credentials to the Autodiscover Endpoint.
 Get the autodiscover.xml and use the information included in the file for
creating a new Outlook mail profile or access the different Exchange services.
The Autodiscover service on the “server side,” is responsible for:
 “Listen” and registered updates in changes in the Exchange environment.

 Accept requests from Autodiscover client, provide them the public server
certificate, get the user credentials.
 Generate the autodiscover.xml file and provide the file to the Autodiscover
client.

The variation of the Outlook mail client
The Autodiscover response of the Exchange CAS server is based on a dynamic
process, in which the Exchange CAS server recognizes the version of the Outlook

client and, based on the specific Outlook version, generate a custom Autodiscover
responded.
For example, Exchange server will create a different “answer” (XML response) for
Outlook client version 2007 versus Outlook client version 2013.

The autodiscover information part 04#36

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The autodiscover information part 04#36