Hi I've been looking around but can't find a straight answer for this - can someone confirms how NSPI works in relation to AD/Exchange/Outlook in layman's terms? Would be really appreciated!

This explains NSPI on basic terms http://forums.msexchange.org/m_1800437071/printable.htm Also you can have a look this post http://www.eggheadcafe.com/software/aspnet/34126968/nspi-proxy-can-contact-gl.aspxRaj

Hi, NSPI is used by MAPI clients such as Outlook to request directory information. NSPI operates over RPC. For the older version of MAPI clients such as Outlook 98, NSPI Proxy is responsible for proxying the request to the GC. Outlook clients 2000 and later version use the referral service to get the GC and connect directly to the GC and bypass the Exchange server. Thanks Allen

Note that in Exchange 2010, the NSPI endpoint for clients is the Client Access Server or Client Access Sever Array and not the GC.

Thanks everyone for their replies. >NSPI is used by MAPI clients such as Outlook to request directory information. NSPI operates over RPC. For the older version of MAPI clients such as Outlook 98, >NSPI Proxy is responsible for proxying the request to the GC. >Outlook clients 2000 and later version use the referral service to get the GC and connect directly to the GC and bypass the Exchange server. Thanks - but how is it linked to the DSProxy process would you say? How are DSProxy and NSPI integrated with each other?

Prior to Exchange 2010, DSProxy runs on Exchange and is responsible for referring the mapi client to a GC for directory access. NSPI runs on the GC and provides the directory information (the GAL), to the mapi clients. http://technet.microsoft.com/en-us/library/how-global-catalog-servers-work(WS.10).aspx How the Global Catalog Works More info: http://msexchangeteam.com/archive/2005/11/04/413669.aspx

Thanks Andy. So, for prior to Exchange 2010: DSProxy runs on the Exchange mailbox servers and refers MAPI clients (e.g. Outlook) to a GC (chosen by DSAccess) for Directory services. NSPI actually runs on the GC and is responsible for providing the information to these MAPI clients. Exchange 2010: DSProxy runs on the Exchange CAS servers and refers MAPI clients (e.g. Outlook) to a GC (chosen by DSAccess) for Directory services. NSPI actually runs on the GC and is responsible for providing the information to these MAPI clients. Would I be correct? So is NSPI running in response to requests from MAPI clients for information, or does NSPI itself contact the MAPI client to provide information?

In Exchange 2010, mapi clients are not referred to the GC. They connect to the CAS for the NSPI endpoint. NSPI is just an interface. The mapi clients connect to for directory information.

Hi, In Exchange 2010, for directory information, Outlook connects to an NSPI endpoint on the Client Access Server, and NSPI then talks to the Active Directory via the Active Directory driver. The NSPI endpoint replaces the DSProxy component as we know from previous version of Exchange server. Thanks Allen

Thanks guys...just one final question and I'm done if that is cool :) When Outlook connects to Exchange, that is a MAPI connection. How about when Outlook connects to an NSPI endpoint on the CAS server (in the case of Exhange 2010) or the GC (pre-Exchange 2010) for Directory Info? Is that also MAPI or is the connection itself called NSPI?

NSPI is the interface/provider. In this scenario, MAPI is the application/protocol/api the client uses to connect to that interface.