OWA client protocol connectivity flow in Exchange 2013/2007 coexistence | 3/4 |18#23 5/5 (1) 16 min read

The current article is the third article of four articles series, on the subject of – “Exchange 2013/2007 coexistence environment and mail client protocol connectivity flow”.

In this article, we will review the client protocol connectivity flow of:
OWA Exchange 2007 clients in an Exchange 2013/2007 coexistence environment.

Client protocol connectivity flow - OWA Client

 

To be able to understand the different “Exchange clients” connectivity protocol flow in Exchange 2013/2007 coexistence environment, we will review five types of “relationships” that exist between Exchange 2007 client and the Exchange CAS 2013 server:

  • Autodiscover client – protocol connectivity flow (Part 2#4)
  • Outlook client – protocol connectivity flow (Part 2#4)
  • OWA client – protocol connectivity flow (Part 3#4)
  • ActiveSync client – protocol connectivity flow (Part 4#4)
  • Exchange web service client – protocol connectivity flow (Part 4#4)

Article Series Table of content | Click to Expand

Exchange coexistence environment | Article Series

The current section, is dedicated to the description of the OWA client protocol connectivity flow in Exchange 2013/2007 coexistence environment.

When reading the description of the different OWA client protocol connectivity scenarios and the details of each scene, you might experience a slight headache.

It’s ok, despite the risk of the “slight headache”, I think that it’s worth putting in the effort, to be able to understand the concept and the logic of the OWA client protocol connectivity flow in Exchange 2013/2007 coexistence environment.
The OWA connectivity flow complexity is too overwhelming

Two key features of the OWA mail client that Differentiate him from other Exchange clients

The client protocol connectivity flow of OWA mail client has two main characteristics that are different from another mail client such as: Outlook or ActiveSync mail clients.

  1. Exchange 2013/2007 coexistence environment
    Compared to most of the client protocol connectivity flow in which the Exchange CAS 2013 Proxy mail client request to their “legacy Exchange CAS server”, in a scenario of the Exchange 2007 OWA client, Exchange CAS 2013 will not Proxy the 2007 OWA client connection request but instead, send a redirection command to the 2007 OWA client.
  2. Specifying the hostname of the Exchange server manually
    Mail clients such as Outlook and ActiveSync, will use the Exchange Autodiscover services for locating the Exchange server name who will serve them. Regarding OWA mail client, the difference is that the user will need to manually type the URL address that includes the FQDN of the Exchange server name. In a scenario of multiple Public faces Exchange site, OWA mail clients from regional Public facing Exchange site can choose to use the “primary namespace” as the Exchange server name or the “regional namespace” as the Exchange server name. We will discuss this scenario in more details in the section OWA client protocol connectivity flow in a multiple Public facing Exchange site environment

OWA Mail client – Specifying manually the hostname of the Exchange server

The main difference between the OWA client versus another Exchange mail client such as Outlook or Mobile (ActiveSync) client is that, most of the time, OWA client will manually type the URL address of the Exchange server instead getting the name of the “Exchange server” from the Autodiscover process. In other words, the OWA client needs to know their Exchange server name versus other Exchange clients that use the Autodiscover process for “locating for them” the required Exchange server name.

In case of that “regional OWA user” such as: OWA user whom his mailbox is located on a “regional Exchange site” (Madrid site in our scenario), OWA user who needs to access their mailbox, can use one of the following naming convention’s options for the Exchange server host name:

  1. Using the primary namespace – in our scenario, the “primary namespace” that represents the “New York Public facing Exchange CAS” is: mail.o365info.com
    In case that a “Madrid OWA user” use the primary namespace as the Exchange server name (OWA URL), the “New York Public facing Exchange CAS” recognizes that the user is a “Madrid OWA users” and redirect him to the “Madrid Public facing Exchange CAS”.
  2. Using the regional namespace – in a scenario of “Madrid OWA user”, the OWA user can use the regional namespace as the Exchange server name (OWA URL). For example: europe.mail.o365info.com. In this scenario, the OWA Madrid user will access ”his Exchange server” directly.
Note – the scenario of: “regional OWA mail client” and the redirection process is not unique or related only to Exchange 2007 OWA client, but instead, to any Exchange OWA client that is involved in a scenario of multiple Public facing Exchange site and regional namespace.

The individual charters of Exchange 2007 OWA Mail client in Exchange 2013/2007 coexistence environment

The process of serving Exchange 2007 OWA mail clients (Exchange users whom their mailbox hosted on Exchange 2007 Mailbox server), is different from the “other mail protocols” because Exchange 2013 “doesn’t know” how to proxy the OWA mail client requests.
Instead, the Exchange CAS 2013 will redirect the “Exchange 2007 OWA mail clients” to their Exchange 2007 CAS server.

This is the main reason for the using the “legacy namespace”. The “redirection message”, that the Exchange 2013 CAS server will send to the “Exchange 2007 OWA mail clients browser” includes the URL address of the Exchange 2007 CAS server who will be able to “serve” the Exchange 2007 OWA mail client requests.

The URL that the Exchange 2013 CAS server provide includes the FQDN (the “legacy namespace) that points to the Exchange 2007 CAS server.

Proxy Exchange 2007 OWA client requests

The concept of silent redirection and SSO

In the former sections, we have a review two different scenarios in which the Exchange 2013 CAS will redirect Exchange 2007 clients to their “destination Exchange CAS server”.

The redirection method that is used by the Exchange 2013 CAS CU2, include two major improvements that are related to the process of: redirecting OWA mail client.

The 2013 CAS CU2 Improvements are:

  1. Silent redirect
  2. SSO
Former version of Exchange CAS server and the OWA redirection method

Although the Exchange 2013 CU2 server version implements the “OWA redirection” process in an improved way, it’s important to emphasize that the “OWA redirection method”, is not a new Exchange method and that the OWA redirection method was included in former versions of Exchange server (as far as I know since the Exchange 2007 server version).

In a former version of Exchange server, the OWA redirection method that was implemented by the Exchange server for “redirecting OWA client” to their Exchange server, could be described as “passive”.

The “OWA redirection” was implemented by displaying a “message window”, which was sent by the Exchange server to the OWA client.

The “redirection information” was presented to the OWA user as a “clickable link”.

I describe this method as: “passive redirection”, because the only responsibility of the Exchange server was to display a message with the link to the OWA client.

The user’s responsibility is to:

  • “Understand” that the link that was presented in the message, is the link to the “right Exchange server”
  • That he needs to click on the link that will redirect him to his Exchange CAS server.

Additionally to the user requirement to “understand” that he needs to click on the link, OWA users, had an experience that can be described as: ”double login”.

Double login OWA users experience

The meaning is that: OWA users, had to re provide their user credentials again, to the “new destination Exchange server“ (the “destination” Exchange 2007 CAS).

Exchange 2013 CAS server version CU2 and the OWA redirection method

Exchange 2013 CAS server version CU2, includes two major features that significantly improve the “Exchange OWA client” experience:

  • A silent redirection (active redirection) – The Exchange 2013 CAS server knows how to send a redirection “command” to the Exchange 2007 OWA browser, that will redirect the OWA session to the “new URL address” (the legacy URL address of the Exchange 2007 CAS server).
  • SSO – Exchange 2013 CAS server knows how to “transfer” or “forward” (Proxy) the OWA user credentials to the “destination” Exchange 2007 CAS server.

The method which Exchange CAS 2013 use for redirecting OWA client described as: “silent” because, the OWA user is not involved throughout the process. The only thing that the OWA user “see” is a short flush on his browsers (the redirection process from the Exchange 2013 CAS OWA login page in the OWA login page from the destination Exchange server).

The “Exchange 2007 OWA client” is not aware of the complicated redirection process. From the “Exchange 2007 OWA client” point of view, this process is transparent.

Note – although we mention the Exchange 2013 CAS method of: silent redirection + SSO in the context of the Exchange 2007 OWA client, this method is implemented in any type of Exchange OWA client in a scenario of multiple Public facing Exchange sites.

Exchange 2013 CAS server Silent redirection and SSO

Q1: How actually the OWA client silent redirection process implemented?

A1: The “OWA redirection process”, is implemented by “cooperation” of the Exchange CAS 2013 and the client browser. Exchange CAS 2013 sends an HTTP redirection command that includes the “new URL address”. The client browser accepts the redirection command and addresses the “destination URL address”
New York Public facing Exchange CAS server send instructions

OWA connectivity flow | Exchange 2007 client | Scenarios

Scenario 1: External 2007 OWA client | User mailbox located at the New York site.

Scenario charters: an external Exchange 2007 OWA client, need to get access to his mailbox.

  • Exchange user type: Exchange 2007 client (Exchange user whom his mailbox is hosted on the Exchange 2007 mailbox server).
  • Exchange mailbox server location: the Exchange 2007 Mailbox server which hosts the user mailbox, is located on the New York site.
  • The New York site includes two public Exchange CAS servers: Exchange 2013 CAS and Exchange 2007 CAS.

The OWA protocol connectivity flow, will be implemented as follows:

  1. The “New York Exchange 2007 OWA client”, type the following URL addresses https://mail.o365info.com/owa
    The URL address that the OWA client use, includes the FQDN: mail.o365info.com which points to the Public facing CAS2013 server in New York site (Number 1).
  2. The external OWA client, provide his user credentials.
  3. CAS2013 uses the user credentials and performs the Active Directory lookup. CAS2013 determines that:
    • The user mailbox version is: 2007
    • That the local site include a Public facing Exchange 2007CAS server
    • That the URL address of the Public facing Exchange 2007 CAS server is: https://legacy.mail.o365info.com/owa
  4. The Exchange CAS2013 will implement two different procedures:
    1. Initiate silent redirect process – the “New York Public facing Exchange 2013” sends a redirection command to the “external Exchange 2007 OWA client browser” that includes the FQDN of the “Public facing Exchange 2007 CAS server”: legacy.mail.o365info.com (Number 2).
    2. Initiate SSO process – the “New York Public facing Exchange 2013” implements the process of SSO, by forwarding (proxy) the Exchange 2007 OWA user credentials, to the “Public facing Exchange 2007 CAS server” (Number 8).
  5. The “external Exchange 2007 OWA mail client browser, “gets” the redirection command from the CAS2013 and, starts a new HTTPS session with the ” Public facing Exchange 2007 CAS server” (Number 3).
  6. The Public facing Exchange 2007 CAS server (legacy.mail.o365info.com) will then facilitate the request and retrieve the necessary data from the Exchange 2007 Mailbox server (Number 5).
  7. The Exchange 2007 Mailbox server, provides the required user mailbox content to the CAS2007 (Number 6).
  8. The CAS2007 sends the information to the “external Exchange 2007 OWA client” (Number 7).

Exchange 2013-2007 coexistence - External Exchange OWA clients - Legacy namespace

Scenario 2: Exchange 2007 OWA client | User mailbox located at the Los Angles site.

Scenario charters: an external Exchange 2007 Outlook client, need to access his mailbox.

Note – To simplify the step’s description, we will relate only to the “external OWA 2007 client” but the same logic and flow are implemented also to the “internal OWA client”.
  • Exchange user type: Exchange 2007 client (Exchange user whom his mailbox is hosted on the Exchange 2007 mailbox server).
  • The Exchange 2007 user mailbox, is hosted on the Los Angles site (the Exchange 2007 Mailbox server located on the Los Angles site).
  • The Exchange 2007 Mailbox server who hosts the user mailbox and the Public facing Exchange 2013 CAS server are not at the same Active Directory site.
  • The New York site, have a “local” Exchange 2007 CAS.

In this scenario, the same logic will be maintained. Exchange CAS 2013 server redirects the Exchange 2007 OWA client to the Public facing Exchange 2007 CAS server.
The “New York Public facing Exchange 2007 CAS server” authenticates the user, performs an Active Directory lookup and determines that the user mailbox is located at the Los Angles site.

  • The “New York Public facing Exchange 2007 CAS server” will proxy the request to the “internal Los Angles Exchange 2007 CAS server” (Number 3).
  • Los Angles Exchange 2007 CAS server” will proxy the request to the “Los Angles Exchange 2007 Mailbox server” (Number 4).

Exchange 2013-2007 coexistence - External OWA clients - Legacy namespace Intranet

OWA client protocol connectivity flow in a multiple Public facing Exchange site environment

In the following section, we will review the OWA client protocol connectivity flow of an external OWA Madrid user who tries to access his mailbox and use the primary namespace as the URL address.

When the OWA Madrid user uses the primary namespace (https://mail.o365info.com/owa), the Host name will be resolved to the IP address of the “New York Public facing Exchange CAS server”.

When the “New York Public facing Exchange CAS server” recognizes that the user considers as a “Madrid user” and that – this OWA client should access “his Public facing Exchange CAS server”, the “New York Public facing Exchange CAS” will implement a method which described as: silent redirection + SSO.

Note – the method of silent redirection and SSO is not related only to a scenario of Exchange 2007 OWA client, but, to any other type of external OWA client such as Exchange 2013 OWA clients.

The external OWA scenarios

In the next section, we will demonstrate OWA flow scenarios in which “OWA Madrid user” (user that his mailbox is hosted at Madrid site will use the primary namespace as the URL address: https://mail.o365info.com/owa

In the following diagram, we can see that the Exchange public infrastructure includes two Public facing Exchange sites: the New York site and the Madrid site. Each of the Exchange site has a Public facing Exchange CAS server.

  • The public name of the “New York Public facing Exchange CAS” is: mail.o365info.com
  • The public name of the “Madrid Public facing Exchange CAS” is: europe.mail.o365info.com

Exchange 2013-2007 coexistence - External Exchange OWA clients - Regional namespace

“Regional OWA users” (Madrid user in our scenario) can choose to use one of the optional URL address.

The Madrid Public facing Exchange CAS server is represented by a dedicated namespace (regional namespace): europe.mail.o365info.com

In case that external OWA Madrid user is familiar with the “Madrid regional namespace”, he can use the URL address: https://europe.mail.o365info.com/owa

The additional option that the OWA Madrid user can use is: using the primary namespace which will “lead him” to the “New York Public facing Exchange CAS”.

In this case the OWA Madrid user can use the URL address: https://mail.o365info.com/owa

When the “New York Public facing Exchange CAS” gets the connection request from the “OWA Madrid user”, he will implement a method was described as: “silent redirection” which will redirect the OWA Madrid user, to “his Madrid Public facing Exchange CAS server”.

Exchange 2013-2007 coexistence - External Exchange OWA clients - The optional URL address

Scenario 3: OWA client | User mailbox located on the Madrid site | Regional namespace |destination site = Public facing

Scenario charters: an external Exchange OWA 2007 client, need to access his mailbox.

  • The Exchange 2007 user mailbox, is hosted on the Madrid site (the Exchange 2007 Mailbox server located on the Madrid site).
  • The “Madrid Exchange site” considers as: Public facing Exchange site.
  • The external OWA user uses the primary namespace as the URL address of the Exchange server (https://mail.o365info.com/owa).
  • The regional namespace that was “allocated” to the Madrid site is: europe.mail.o365info.com

In the current scenario, an “OWA Madrid user” use the URL address: https://mail.o365info.com/owa for access his mailbox.

The OWA protocol connectivity flow will be implemented as follows:

  1. Madrid Exchange 2007 OWA client, type the following URL addresses https://mail.o365info.com/owa
    The FQDN: mail.o365info.com points to the “New York Public facing Exchange CAS server” (Number 1).
  2. The external OWA client, provide his user credentials.
  3. CAS2013 uses the user credentials and performs the Active Directory lookup. CAS2013 determines that:
    • The user mailbox version is: 2007
    • The Exchange 2007 mailbox server that host the user mailbox, is located at the Madrid site
    • The remote site (Madrid site) is a Public facing Exchange site
    • That the “OWA address” of the “Madrid Public facing Exchange CAS server” is: https://europe.mail.o365info.com/owa
  4. The Exchange CAS2013 will implement two different procedures:
    1. Initiate silent redirect process – the “New York Public facing Exchange 2013” sends a redirection command to the “Madrid Exchange 2007 OWA client browser” that includes the FQDN of the “Europe Exchange 2007 Public facing Exchange CAS”: europe.mail.o365info.com (Number 2).
    2. Initiate SSO process – the “New York Public facing Exchange 2013” implements the process of SSO, by forwarding (proxy) the Exchange 2007 user credentials, to the “Europe Exchange 2007 Public facing Exchange CAS” (Number 8).
  5. The “Madrid Exchange 2007 OWA mail client browser, “gets” the redirection command from the CAS2013 and, starts a new HTTPS session with the “Madrid Exchange 2007 Public facing Exchange CAS” (Number 3).
  6. The Madrid Exchange 2007 Public facing Exchange CAS (europe.mail.o365info.com) will then facilitate the request and retrieve the necessary data from the Exchange 2007 Mailbox server (Number 5).
  7. The Madrid Exchange 2007 Mailbox server, provides the required user mailbox content to the Madrid CAS2007 (Number 6).
  8. The Madrid CAS2007 sends the information to the “external Exchange 2007 OWA client” (Number 7).

Exchange 2013-2007 coexistence - External OWA clients -Multiple Public facing

Exchange 2013 coexistence | Article series index

The Exchange 2013 coexistence article series index page

0/23

Exchange 2013 coexistence environment and client protocol connectivity flow | The prefix

1/23

The importance of Exchange 2013 CAS in Exchange 2013 coexistence environment | Part 1/2

2/23

The importance of Exchange 2013 CAS in Exchange 2013 coexistence environment | Part 2/2

3/23

Exchange Public infrastructure | Public versus non Public facing Exchange site

4/23

Exchange Public infrastructure | Public versus non Public facing Exchange site

5/23

Exchange web services in an Exchange 2013 coexistence environment | Part 1/2

6/23

Exchange web services in an Exchange 2013 coexistence environment | Part 2/2

7/23

Exchange 2013 coexistence environment and the Exchange legacy infrastructure

8/23

The checklist for preparing your Exchange 2007 infrastructure for Exchange 2013 coexistence

9/23

The checklist for preparing your Exchange 2010 infrastructure for Exchange 2013 coexistence

10/23

Exchange 2013 coexistence environment | Autodiscover infrastructure | Part 1/2

11/23

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

12/23

Basic concepts of Outlook connectivity in Exchange 2013 coexistence environment | Part 1/2

13/23

Exchange 2013 coexistence environment and Outlook infrastructure | Part 2/2

14/23

Manage legacy Exchange URL address using a PowerShell script

15/23

Client protocol connectivity flow in Exchange 2013/2007 coexistence environment | Introduction and basic concepts| 1/4

16/23

Autodiscover and Outlook client protocol connectivity flow in Exchange 2013/2007 coexistence environment | 2/4

17/23

OWA client protocol connectivity flow in Exchange 2013/2007 coexistence environment | 3/4

18/23

ActiveSync and Exchange web service client protocol connectivity flow in Exchange 2013/2007 coexistence environment | 4/4

19/23

Client protocol connectivity flow in Exchange 2013/2010 coexistence environment | Introduction and basic concepts| 1/4

20/23

Autodiscover and Outlook client protocol connectivity flow in Exchange 2013/2010 coexistence environment | 2/4

21/23

OWA client protocol connectivity flow in Exchange 2013/2010 coexistence environment | 3/4

22/23

ActiveSync and Exchange web service client protocol connectivity flow in Exchange 2013/2010 coexistence environment | 4/4

23/23

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One Response to “OWA client protocol connectivity flow in Exchange 2013/2007 coexistence | 3/4 |18#23”

  1. Hi Sir,
    I just want to verify one issue,

    I used Quest(Dell) tool to migrate AD user from one forest to another forest, exchange2013 server only in source forest,and set the source account disabled,
    then after migration, target account exchange service(owa/activesync/outlook) woking fine.
    but for some reason, if I enable source account manually, then both source/target user can not use owa service,
    as showing “tokenmungingexception”, i found the solution to change the target account from linked mailbox to user mailbox, but as migration is still ongoing, and we follow the exchange forest architecture, we do not know whether it’s exchange2013 architecture changed or not, as in same scenario exchange2007 and exchange2010 working fine even both source/target account enabled. it’s very strange why it only impact the owa service in exchange2013.
    Could you help me? it’s actually not the migration tool(Quest migration manager) issue.
    thanks
    Guo Gang

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