microsoft team foundation server load balancing

#MICROSOFT TEAM FOUNDATION SERVER LOAD BALANCING OFFLINE#

When the offline responder is invoked, the affected protocol (or server) is removed from service. Managed Availability includes an offline responder. Unfortunately, this lack of knowledge around target URL (or the content of the request), introduces complexities around health probes.Įxchange 2016 includes a built-in monitoring solution, known as Managed Availability. The load balancer can use a variety of means to select the target server from the load balanced pool, such as, round-robin (each inbound connection goes to the next target server in the circular list) or least-connection (load balancer sends each new connection to the server that has the fewest established connections at that time). Since session affinity is not used by the load balancer, this means that the load balancer has no knowledge of the target URL or request content.All the load balancer uses is layer 4 information, the IP address and the protocol/port (TCP 443): However, there is a concern with this architectural change. Instead of proxying the request at step 6, MBX will redirect the request to the Mailbox server hosting the active copy of the user’s database, as the telephony devices support redirection and need to establish their SIP and RTP sessions directly with the Unified Messaging components on the Mailbox server.įigure 1: Exchange 2016 Client Access Protocol Architecture If the protocol leveraged by the client is IMAP or POP, then the protocol used between the Mailbox servers is IMAP or POP. If the client leverages the HTTP protocol, then the protocol used between Mailbox servers is HTTP (secured via SSL using a self-signed certificate). The protocol used in step 6 depends on the protocol used to connect to MBX. This means that all sessions, regardless of their origination point (i.e., MBX servers in the load balanced array), end up at the same place, the Mailbox server hosting the active database copy.This is vastly different in releases prior to Exchange 2013 – for example, in Exchange 2010, if all requests from a specific client did not go to the same endpoint, the user experience was negatively affected. In the event that the active database copy is moved to a different Mailbox server, MBX closes the sessions to the previous server and establishes sessions to the new server. For a given protocol session, the Client Access services located on the Mailbox server now maintains a 1:1 relationship with the Mailbox server hosting the user’s data.

Step 5 is the fundamental change that enables the removal of session affinity at the load balancer.

The Client Access services located on the MBX server proxies the request to the Mailbox server hosting the active copy.

The Client Access services located on the MBX server queries an Active Manager instance that is responsible for the database to determine which Mailbox server is hosting the active copy.The Client Access services located on the MBX server makes a decision on whether to proxy the request or redirect the request to another MBX infrastructure (within the same forest).Mailbox location information (e.g., database information, ExternalURL values, etc.).Mailbox version (for this discussion, we will assume an Exchange 2016 mailbox).The Client Access services located on the MBX server authenticates the request and performs a service discovery by accessing Active Directory to retrieve the following information:.The load balancer assigns the session to a MBX server in the load balanced pool.A client resolves the namespace to a load balanced virtual IP address.From a protocol perspective, the following will happen: To understand this statement better, and see how this impacts your designs, we need to look at how MBX2016 functions. Like Exchange 2013, Exchange 2016 does not require session affinity at the load balancing layer.

Microsoft team foundation server load balancing