[CentOS] recommendations/suggestions - geographically spread network based on Centos

Good day all,

I was wondering if I could pick some admin heads here as I have a HUGE  
project I have been tasked with.....

I am asking here since I will be basing everything on Centos, and want  
it to all play nice together. If anyone feels this is straying off  
topic, please just reply off list. I do not want to be the cause of  
one of those threads.

I have 3 offices, 1 in Canada, 2 in Mexico. We are currently  
investigating connectivity options (still no results yet), but I  
suspect one of the mexican sites will be very limited.

I need to setup the typical office setup, but need to get the  
following figured out. I personally do not have experience in this  
type of network (all my past experience comes from a centralized  
office, one location, or a multi office with services all based in  
their respective locations).

So because The connectivity is probably limited (in our mexican  
offices), I will need to take that into consideration (obviously).
Our head office has a 10mb full duplex fiber feed, but we also have  
equipment in data centers.

What I need in the end is:

- exchange like functions IE Global address book, shared calenders,  
etc (looking at scalix, or could keep my existing email server - very  
happy with it, and just setup a LDAP server and a CalDAV server -  
still investigating this one though).
- Funambol with various connectors to push email and calendars to  
blackberries and iphones.
- vpn (openvpn) - mostly just the head office though
- collaborative / project management environment (looking at alfresco  
- sharepoint alternative)
- monitoring (nagios)
- helpdesk (glpi with ocs for inventory management)
- file sharing (samba)
- remote file backups (probably just rsync into a dedicated backup  
machine in a data center)
- access to all services (probably - still waiting back from the  
higher ups) from all locations

So my first thought is that my preference it to keep as much at a data  
center as possible due to security, temperature control, connection  
reliability, etc. Due to my inexperience with some of these products,  
(IE Scalix,etc) I am kind of wondering what the best way or topology  
is to do this is.

So at a brief first thought I kind of envisioned this:

- scalix,  Funambol, alfresco, nagios (also one in my office as  
backup), backup box collocated in the data center providing it can be  
locked down adequately, and still provide the needed services to all 3  
offices.
- in each office a samba file server, vpn server.

Due to the probable connectivity issue with the remote offices (one is  
literally in the desert at a work site), I did not think a constant  
inter-office VPN was the way to go, Or even securing the main data  
center services with VPN (unless I could build it right for speed).

However I guess I could lock down the data center services with VPN,  
and create a constant connection between head office and the data  
center, and allow the other offices to connect via individual vpn  
connections as needed.

Thoughts? Just looking for a general broad overview, or some software  
recommendations if anyone from experience has a recommendation that is  
possibly better than the software I had outlined here.

Dnk



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