Reverse Proxy For MS Exchange

This feature provides a L7 load balancing an reverse Proxy for Microsoft Exchange 2010,2013,2016
This feature is currently in beta mode and can be displayed on Artica v4.30 Service Pack instable 931

This feature is dormant and awaiting sponsors.( This means that it still exists in v4.50+ but needs to be consolidated. )
Demand from our customers on this feature is very limited.
To ensure real functionality, we need customers willing to test the product and offer us technical feedback.

Installing the feature

This feature is designed to handle 80/443/25/143/993 ports in order to forward requests to the Exchange servers back-ends.
In this case, when you will install this feature, all conflicts features will be automatically removed.

• On the left menu Your System / Features
• On the search field type "exch"
• Click on install on the install button

Configure the main service

On the left menu, choose "Ms Exch. Reverse-Proxy" and Parameters.

You should see that the status is on stopped. It is normal until you have not added any MS Exchange server you want to serve.

The most important parameter to define is the SSL certificate

• In order to serve the SSL protocol, set the SSL certificate to use under "SSL Certificate" drop-down list.
• Set the number of CPU(s) you want to use for the Reverse Proxy service.
• Define the Network interface to use for inbound connections in "Listen interface"
• Define the Network interface to use for outgoing connection in "Outgoing interface".
  This option allows you to define a real secure gateway by using 2 network cards.
  Each network interface are independent and TCP packets cannot be routed from Wan interface to LAN interface.
  This means only data using ports managed by the Reverse Proxy service can be forwarded to the LAN interface.
  If you did not have 2 network interfaces, just choose "All interfaces" in the drop-down field.
• The method defines how the reverse-proxy balance connections if you using multiple back-end Exchange servers:
• Lowest connection: 
  The server with the lowest number of connections receives the connection. 
  Round robin is performed within groups of servers of the same load to ensure that all servers will be used 
  This algorithm is dynamic, which means that server weights may be adjusted on the fly for slow starts for instance.
   
• Round-Robin: Each server is used in turns, according to their weights.
  This is the smoothest and fairest algorithm when the server's processing time remains equally distributed. 
  This algorithm is dynamic, which means that server weights may be adjusted on the fly for slow starts for instance. 
  It is limited by design to 4095 active servers per back-end. 
  Note that in some large farms, when a server becomes up after having been down for a very short time, it may sometimes take a few hundred requests for it to be reintegrated into the farm and start receiving traffic. 
  This is normal, though very rare. It is indicated here in case you would have the chance to observe it, so that you don't worry.
   
• Strict hashed ip: 
  The source IP address is hashed and divided by the total weight of the running servers to designate which server will receive the request. 
  This ensures that the same client IP address will always reach the same server as long as no server goes down or up. If the hash result changes due to the number of running servers changing, many clients will be directed to a different server.
  This algorithm is static by default, which means that changing a server’s weight on the fly will have no effect
   
• Click on Apply button.

Add your Microsoft Exchange back-ends

• On the left menu, choose "Backends" menu.
• Click on new Backend button

By default no back-end is added, the table is empty

• Back-end name: it is a label name used to be displayed in the configuration.
• Destination address: 
  The TCP/IP address of the back-end.
• Exchange Server: Set the version of your target MS Exchange server
• Weight: The "weight" parameter is used to adjust the server's weight relative to other servers. 
  All servers will receive a load proportional to their weight relative to the sum of all weights, so the higher the weight, the higher the load. 
  The default weight is 1, and the maximal value is 256. A value of 0 means the server will not participate in load-balancing but will still accept persistent connections. 
  If this parameter is used to distribute the load according to the server's capacity, it is recommended to start with values which can both grow and shrink, for instance between 10 and 100 to leave enough room above and below for later adjustments.
• Enable Exchange protocols you want to server with the Reverse-Proxy
• Click on Add button.

The back-ends table display status of each server and each protocol forwarded.

The Community Edition allows to add only one Exchange server. To load-balance several servers, you need to purchase an Enterprise Edition.