Exchange ActiveSync / Mobile messaging queries

Posted on 2013-01-19
Last Modified: 2013-02-05
Our environment is Exchange 2010 SP1 and BES 5.0.2

We are looking at upgrading to BES10 later once it's released and also other mobile email products to cater for iPhone users.

I understand that BES10 and most mobile email applications are going to use ActiveSync to synchronise email, rather than MAPI.

I'm not familiar with AS did some reading up although still had some questions:

i. With BES, the standard advise was that the latency between the BES server and the mailbox server should be minimised, certainly no more than 35ms. Does ActiveSync have the same limitations, would we still need to place the BES account this close to the mailbox? Certainly, that's what we'd do, but I was wondering what the latency requirements for ActiveSync were.

ii. ActiveSync is described as being true "push" email in the same way Blackberry currently is. Ignoring Blackberry for the moment, how does an ActiveSync client currently have email pushed to it? With MAPI, there was the MAPI notification system that sent a UDP packet which meant that the client would initiate a response to the server requesting the does ActiveSync work on mobile devices? How does Exchange know it's there in the first place and when to send a message to it? Is the connection "always on" as in MAPI?

iii. Would it be correct to say that ActiveSync is just a protocol, and independent vendors can choose to implement their own variation of it? So how an Exchange native ActiveSync client like Windows Mobile behaves, could be completely different to a 3rd party one?
Question by:cpancamo

Expert Comment

ID: 38797084
Good day to you. Here are some answers to your questions:

1) ActiveSync is typicaly a little more forgivving, because ActiveSync runs on the Exchange CAS Role, and in many cases it's connections are proxied through an ISA or TMG Server/Array in the DMZ, and there is typically some RPC latency between CAS and Database servers, in larger environments, over 100MS.
2)ActiveSync clients connect differently, and more cleanly then MAPI clients, because the ONLY establish an HTTP/HTTPS connection when receiving new messsages. The client can be configured on the mobile device/IPAD, or whatever the case to either download new messages(or SYNC) on a given interval(like every 5 minutes) Or they will maintain a constaint HTTP/HTTPS connection to the CAS server to downlaod new messages as the come in.
3) ActiveSync is more like a suite of protocols, and different vendors can implement their own flavor of it. The only major requirements are, as mentioned before an HTTP/HTTPS connection is served on the front-end, and RPC(or MAPI, depending on Exchange version) is available on the back end.
NOTE: In your environment, RIM would recommend you upgrade to Exchange Service Pack 2, especially before moving to BES10.  I was able to upgrade the Exchange Service pack and run BES 5.0.2 for a while with no issues in my customer's environment. Also, keep in mind, in Exchange 2010, MAPI connections are handled by the CAS server ONLY. Connection to the Databases is handed off to the CAS server.  Please reply back if you need further clarification.

Author Comment

ID: 38797319
Thanks, only need clarification on the first point

1) ActiveSync is typicaly a little more forgivving, because ActiveSync runs on the Exchange CAS Role, and in many cases it's connections are proxied through an ISA or TMG Server/Array in the DMZ, and there is typically some RPC latency between CAS and Database servers, in larger environments, over 100MS.

So, in the case of BES10, we have the BES server, the CAS server and the mailbox server.

BES <> CAS server will be ActiveSync (which runs on the CAS). And then CAS <> Mailbox server is MAPI.

But how close does the BES need to be to the CAS server, seeing as we are using ActiveSync? In the days when BES used MAPI, it had to be in the same site (max 30ms away), but not sure how this works with ActiveSync (i,.e. the BES <> CAS connection using ActiveSync). I assume they still need to be close, but not sure how close or why?
LVL 37

Accepted Solution

Jamie McKillop earned 500 total points
ID: 38801299

The BES server doesn't need to be close to your CAS server. Activesync will work over high latency connections. The BES server is simply proxying your activesync connections, so the connection should be at least as good from BES to CAS as from mobile device to CAS.


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