Thursday, May 19, 2016

Understanding Exchange Server 2016 Architecture

MS Exchange Server is one of the most commonly used server by multiple organizations to support several business requirements. The latest version is Microsoft Exchange Server 2016 that has come up with new set of technologies, features, and services to Exchange Server. The main motive has been focused on supporting people and organizations with the work habits evolving from communication focus to collaboration focus. It has been aimed to help in lowering the total cost of ownership irrespective of the services on-premises or off-premises. The blog will be discussing about the Exchange Server 2016 Architecture in details.

Architecture of Exchange Server 2016

Exchange Server 2016 comes with single building block architecture that provides email services for deployments ranging from small to large-scale organizations.
Exchange Server 2016 Architecture

Components of Exchange Server 2016 Architecture

  1. Server Communication Architecture
    Exchange Server 2016 and its variant versions communicate between one another through protocol layer, as cross communication is not allowed. This architecture of communication is defined as ‘every server is an island’ with the benefits discussed below:
    • Low Inter-server communications
    • Isolated failures
    • Each server has integrated design
    • Version-aware communications
      Protocol Layer Communication between Exchange 2016 Servers
  2. Server Role Architecture
    Exchange Server makes use of two servers:
    • Mailbox Servers
      1. Consists of transport services to route mail.
      2. Consists of mailbox databases that process, render, & store data.
      3. It contains Client Access Services that accept client connections for all protocols. These frontend services are used for routing/proxy connections to corresponding backend services on Mailbox server as clients do not connect directly to backend services.
      4. It provides unified messaging (UM) services for voice mail & other telephony features.
      5. Exchange Admin Center (EAC) & Exchange Management Shell are used to manage mailbox servers.
    • Edge Transport Servers
      1. Handle all external flow for the Exchange Organization.
      2. These servers are installed in the perimeter network & subscribed to internal Exchange organization. The EdgeSync synchronization process makes recipient and other configuration information available to Edge Transport Server as mail enters & leaves the Exchange organization.
      3. Antispam & Mail flow rules are provided as mail enters & leaves the Exchange organization.
      4. Exchange Management Shell is used to manage Edge Transport servers.
  3. High Availability Architecture
    It comes in two sections as below:
    • Mailbox High Availability
      1. Database Availability Group (DAG) is the functional element of high availability & site resilience framework that is built into Exchange 2016.
      2. DAG contains group of mailbox servers hosting set of databases and provide automatic, database-level recovery from network/database/server failures.
      3. DAG has been improved in 2016 than Exchange 2013.
    • Transport High Availability
      1. It has feature called Shadow Redundancy that makes redundant copies of all messages in transit.
      2. Safety Net feature is also present that makes redundant copies of all delivered messages.
      3. DAG supports transport high availability boundary to achieve site resilience by spanning a DAG across multiple Active Directory sites.
      4. Transport high ability is best effort for message redundancy as Exchange Server 2016 attempts to guarantee message redundancy keeping multiple copies of messages during & after delivery.
  4. Client Access Protocol Architecture
    The client access services are used for accepting all forms of client connections. These front-end services proxy these connections to the backend services on the destination Mailbox server. Clients do not connect to backend services directly.
    Client Access Protocol Architecture

    Protocol used by client determines the protocol that will be used to proxy the request to backend services on destination mailbox server. E.g. If client uses HTTP, mailbox server uses HTTP to proxy the request.
    In case of telephony requests, mailbox server redirects the request to mailbox server that holds the active copy of user’s mailbox instead of proxying the request. Telephony devices need to establish their SIP & RTP sessions directly with UM services on mailbox server.

Improvements in Exchange 2016 Architecture

  • Server Role Consolidation
    In Exchange 2016, Client Access Server Role is installed automatically as part of mailbox server role unlike earlier versions that allows installation of Client Access Server & Mailbox Server role on separate computers. This multi-role Exchange Server architecture provides benefits like:
    1. All the Exchange Servers in the environment can be same i.e. same hardware, same configuration etc., which simplifies hardware purchasing, management, & maintenance of Exchange Servers.
    2. Need of fewer physical Exchange servers leads to lower ongoing maintenance costs, fewer Exchange server licenses, reduced power requirements etc.
    3. Better scalability as the workload is distributed across large number of physical machines. Load on remaining multi-role servers during failure only increases incrementally ensuring other functions are not affected.
    4. Improved Resiliency as a multi-role Exchange Server can survive huge number of Client Access role or failures.
  • Improved Search Feature
    1. Local Search instance is able to read data from local mailbox database copy.
    2. Passive search instances does not need to co-ordinate with their active counterparts to perform index updates.
    3. Bandwidth Requirements between active & passive copy has been reduced by 40% compared to earlier versions of Exchange Server.
    4. Search can perform multiple asynchronous disk reads prior to a user completing a search item.
    5. Cache is filled with relevant information that provides sub-second search query latency for online clients like Outlook on Web.
  • Office Online Server Preview for Outlook
    1. In Exchange 2016, Outlook on the web uses Office Online Server Preview to provide rich preview & editing capabilities for documents unlike WebReady Document viewing provided in earlier versions.
    2. This feature provides a consistent document experience with products like SharePoint and Skype for Business.
    3. Office Online Server Preview needs to be deployed in on-premises environment if it is not present earlier.
  • MAPI over HTTP is the default for Outlook connections
    MAPI over HTTP was introduced in Exchange 2013 Service Pack 1 to improve traditional Outlook (RPC to HTTP) connection method. In Exchange 2016, MAPI over HTTP is enabled by default and other features like ability to enable/disable MAPI over HTTP per user and to advertise it or not to external clients.


The blog has been discussing to make users understand about the Architecture of Exchange Server 2016. Each components of the Exchange Server Architecture has been described in details along with the changes provided by Exchange Server 2016 as compared to its earlier versions.


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