Business Considerations For Exchange Design

      Business Requirements For Exchange Implementation




This guide will not target on the core technical aspects of exchange , rather concentrate on the business model which is vital and important while designing any solution.


I am keeping this guide as a solution and later go into technical details as necessary. This guide will be useful for anyone who wish to design their infrastructure , either new or modify the existing infrastructure.


User Modes


Possible Modes of User Requirement


  • Cached Exchange Mode : used for low-bandwidth environments
  • OWA : outlook web access
  • OMA : outlook Mobile access , receiving emails on mobile



Design Modes


Exchange falls into 2 design modes


  • Physical Mode
  • Logical Mode



Under physical mode we decide placement of the exchange server , its proximity , placement etc..


Under logical mode , exchange highly depends on the AD so AD infrastructure should be sound.


PS : Design Active directory keeping Exchange in design.




Infrastructure Considerations


Even before jumping to install the exchange and work on it , there are very major considerations one has to understand such as


Company detailed architecture diagram :

One should understand the architecture of the company , only when a complete solution can be designed, if you miss any of the part then you will end up doing messy stuff. So as a First Aid box , every Architect, Systems engineer , Administrator should have the detailed architecture diagram .


This blue print should give

  • Number of geographical spanned locations of your organization
  • Number of branch offices configured
  • Number of regional offices configured
  • Connectivity information between these locations
  • Number of servers installed on each location , including mixed mode servers.
  • Mobile users
  • Wireless users
  • Routers , switches details.






Connectivity :

This would be the next step after you have basic architecture diagram of your company , you have to concentrate of the connectivity and few basic checks would be

  • How are the devices at each location has internet connectivity
  • Internet connectivity provider information
  • Bandwidth information , you need to get bandwidth information for every site.
  • Leased Line information
  • MPLS VPN information
  • MPLS LogicalLeased line information
  • DSL connectivity information


I have listed the connection methods which are widely used today. So now you would have detailed understanding about the architecture and the bandwidth information handy.



Network Information :

This falls as my 3rd option which is very important with respect to design perspective. You have to understand the network layout of your organization which gives you more understanding of servers placement and security implementation. Some of the key points would be

  • Perimeter network
  • Wireless network
  • Bastion host
  • Placement of routers
  • Placement of firewall


I would say most of the network design consideration would fall into this model. Such as do you want to design wireless network , do you want to design bastion host , DMZ network are one of the major design considerations even before you bring in the servers.


So understanding about connection / bandwidth , we can judge what type of routers / networks to be configured.




Data Center :

This would constitute information about the cabling , rack space, power , logistics etc. Understanding these would give you detailed understanding of placements of the routers and switches or any hardware devices in the organization.



After understanding the above design aspects , one can move ahead and start designing for the exchange server.


Active Directory Considerations:

Every datacenter uses exchange server, and organizations are very much dependent on the exchange servers and the only reason is exchange is easy to manage, secured , integrates with AD. So one remembers Alt+s  easily !.


After understanding the network , perimeter information , hardware information , you have to plan AD which is not an friendly component of Microsoft. AD by the name makes people to think , think and think , its vast and complex. So you need to understand how is your AD forest implemented , you need to think if you need a new forest to install Exchange or can existing AD forest accomplish this. So the next step would be to note down

  • Number of forests
  • Number of domains
  • Number of sites in each domain
  • Subnet configuration
  • Users information


Understand the number of domain controllers, Global catalog servers deployed in each domain in a forest , this information is useful in managing the GAL and used for exchange server objects replication.




As a personal experience I have seen that administrators try to implement latest software an example would be if Exchange 2010 is introduced in market , they want to implement but fail to evaluate

  • Is there a real need for the new software implementation
  • Does current network infrastructure is feasible
  • Migration cost
  • Planning and implementation



I will be continuing this article focusing on AD planning for Exchange in my future posts.