Exchange 2000/2003 FE/BE topology step by step
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Environment
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AD domain: strongline.local
DNS domain: strongline.net
Exchange sites: site1 and site2
Exchange smtp domain: site1.com and site2.com
Users has either @site1.com or @site2.com email address

Objectives
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Users can access their emails by http://mail.site1.com or http://mail.site2.com
or http://mail.strongline.net/site1 or http://mail.strongline.net/site2

Steps
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1. Supposed that you have install all Exchange back-end servers ready
S1-Ex.strongline.local
S2-Ex.strongline.local

users can access their email internaly by Outlook, OWA (http://S1-Ex/Exchange or http://s2-ex)

2. Now install a new Exchange server (2000 Enterprise Edition or 2003 server) into either site1 or site2, it doesn't matter, check the box "it is a front-end server". In our example, the server will be named FE-Ex.strongline.local, it's public name will be mail.strongline.net

At this point, if all your users have a common email address, say @strongline.net, and @strongline.net is your default recipient policy, then
* internally, you can just type in http://FE-Ex to get your email. Of course you can create a CNAME record "mail" pointing to "FE-Ex" so you can just type in http://mail
* externally, you can type in http://mail.strongline.net
But remember in our example, users have either @site1.com or @site2.com address. So we will have to do a little more tweaking job

3. Create virtual directories for URL http://mail.strongline.net/site1 and http://mail.strongline.net/site2
- In Exchange System Manager, expand your FE server, Protocols, HTTP, right click, new virtual directory. Set Exchange Path to "Mailbox for site1.com" and "site2.com" respectively.
- Do the same on all back-end servers that contain mailboxes for site1.com/site2.com

Now you should be able to access your email via http://mail.strongline.net/site1 and http://mail.strongline.net/site2

4. Create HTTP virtual servers for URL http://mail.site1.com and http://mail.site2.com
- In Exchange System Manager, expand your FE server, Protocols, HTTP, right click, new virtual servers. Give it a proper name, select the correct IP address. Click on Advanced button, Add, Select IP address, type in "mail.site1.com" in Host Name box, OK. Select "mailboxes for site1.com".
- Create another HTTP virtual server for site2.com.
- Do the same on all back-end servers that contain mailboxes for site1.com/site2.com

Now you should be able to access your email via http://mail.site1.com and http://mail.site2.com

5. There are couple more things such as authentication, disabling un-neccessary services on FE server, and so on have to be done, please refer to http://www.microsoft.com/technet/
prodtechnol/exchange/2003/library/febetop.mspx
for more information.

I was too lazy to add couple new posts about Offline Address Books and Recipient Update Service that were planned long time ago.

I am not doing that today, even today is really quite and nice day - thanks to the Thanksgiving holiday in the States! I have not customer to call me today so far...

Probably some time after Chrismas...

Ethernet_II, 802.3, 802.2 vs. SNAP

There are four types of ethernet frame type:
Ether_II,
802.3,
802.2,
SNAP

Ether_II: has a field named "protocal", which specifys the upper layer(network layer)protocal(e.g. IP, IPX, etc.)

802.3: without a "protocal" field but has a "length"

802.2: Since the 802.3 Ethernet frame cannot by itself identify the upper-layer (Network)protocol, it obviously needs some help. The IEEE defined the 802.2LLC specifications to provide this function and more. an 802.2 frame is an 802.3 frame with the LLC information in the data field of the header. 802.2 frame is identified by "Dest. SAP" and "Source SAP" fields, these two fields specifys the upper layer protocal

SNAP: The SNAP frame has its own protocol field to identify the upper-layer protocol.This is really a way to allow an Ethernet_II Ether-Type field to be usedin an 802.3 frame. SNAP frame is identified by its "Dest. SAP" and "Source SAP" fields, always have the value of "0xAA" - SNAP, the upper layer protocal has already been specified in "protocal" field

In short words:
originally we have Ether_II or 802.3(created by Novell, with no Type field, then accepted by IEEE), then IEEE introduced 802.2 and SNAP to modify 802.3 so 802.3 can identify upper level protocol. when we say 802.2 frame, we mean a 802.3 frame with 802.2 header; when we say SNAP frame, we mean on top of 802.3, we have SNAP header. In the meantime, SNAP is a
special 802.2 frame with certain values on SSAP, DSAP, and Command fields.