RPC over HTTP Interactions on the Back-End Servers

  • Article

 

Microsoft® Office Outlook® requires access to three types of back-end servers:

  • Mailbox servers

  • Public folder servers

  • Global catalog servers

Mailbox Servers

Mailbox servers store user mailboxes, including any mailboxes that a user must access as a delegate. The Microsoft Exchange Information Store service listens for incoming RPC requests on port 6001.

Public Folder Servers

Public folder servers store public folder data. Public folder servers include both the home public folder servers of users and any servers that hold replicas of the data to which Outlook may be redirected.

Public folder servers store free/busy data. Public folder servers that store free/busy data must be accessible to Outlook so that users can view other users' free/busy data.

Public folder servers store the Outlook offline address book. Public folder servers that store offline address book data must be accessible to Outlook so that users can download the offline address book.

Global Catalog Servers

Outlook does not connect directly to global catalog servers when you use RPC over HTTP, so you do not have to add global catalog servers to the list of servers that the RPC proxy server can access. Instead, the users’ mailbox server forwards directory RPC requests to the global catalog servers. However, because of product version changes in the RPC protocol that are designed to support RPC over HTTP, these servers must also meet the requirements for RPC over HTTP.

DSProxy

Directory Service Proxy (DSProxy) is an internal component of the Exchange system attendant. It provides an address book service to Outlook clients. When RpcProxy.dll forwards an RPC request to port 6002 or port 6004, DSProxy receives that request.

Note

For more information about RpcProxy.dll, see RPC over HTTP Interactions on the RPC Proxy Server.

An RPC request to the referral service port (6002) of DSProxy requests a referral to a global catalog server.

A client computer cannot connect to a global catalog server directly over the Internet. Therefore, the referral service of DSProxy replies to the request with the local Exchange server on which DSProxy is running. The client uses the local Exchange server on which DSProxy is running, instead of the global catalog server. The client computer then uses the DSProxy proxy service port (6004) on the local Exchange server for requests for directory information. The local Exchange server forwards the request to the global catalog server.

Note

In Exchange Server 2003 with no service packs installed, the referral service of DSProxy cannot distinguish between an RPC over TCP request and an RPC over HTTP request. If the Exchange back-end server has Exchange Server 2003 installed with no service packs, you should not publish the referral service port (6002) in the ValidPorts registry entry on the RPC proxy server. When Outlook tries to contact the referral service of DSProxy, it fails because you did not publish the referral service port on the RPC proxy server. Outlook then tries to contact the proxy service of DSProxy on the Exchange server. The proxy service forwards the request to a global catalog server.

For more information about Exchange Server 2003 and the Active Directory® directory service, see "Exchange Server 2003 and Active Directory" in the Exchange Server 2003 Technical Reference Guide (https://go.microsoft.com/fwlink/?LinkId=47891).