In this article, let’s have a quick overview of routing methods that are supported by Azure traffic manager.

There are six different routing methods that are supported by Azure traffic manager. The routing methods determine which endpoint would be returned by Azure traffic manager. Let’s have a look at each of those strategies.

Priority

In this routing method, Azure traffic manager maintains a list of prioritized endpoints. In that list, every endpoint has priority and status. If all endpoints are correctly functioning, the traffic is always redirected to the primary endpoint.

If primary endpoint is not available, the traffic manager decides next best-performing highest priority endpoint and traffic is redirected to that endpoint.

Weighted

Azure traffic manager maintains a list of weighted list of endpoints. Every endpoint has a weight associated with it. Azure traffic manager always returns best performing endpoint with highest weight.

If every endpoint has same weight, it will evenly distribute traffic across all the endpoints.

The weight can be ranging from 1 to 1000. If weight is not specified, Azure traffic manager will assume 1 to be its weight.

This method can be very helpful for gradually upgrading the applications.

Performance

Traffic Manager maintains an Internet Latency Table to track the round-trip time between IP address ranges and each Azure datacenter.

The traffic manager than takes the source IP and looks it up in this latency table. Then it figures out the data center which is “closest”. The term “closest” does not mean that the endpoint is geographically closest. Azure traffic manager returns the endpoint which has lowest latency for that IP address range.

Geographic

In this routing method, the Azure traffic manager maintains a list of endpoints and geographical regions for which these endpoints are applicable. Each endpoint is associated with set of geographical locations. The geographical region can be “world” (any region), regional grouping (e.g. Africa, Middle east, etc), any country or region, OR any state or province.

When a region or a set of regions is assigned to an endpoint, any requests from those regions gets routed only to that endpoint. Traffic Manager uses the source IP address of the DNS query to determine the region from which a user is querying from – usually this is the IP address of the local DNS resolver doing the query on behalf of the user.

Examples include complying with data sovereignty mandates, localization of content & user experience and measuring traffic from different regions.

If the endpoint is stopped or disabled, then Azure traffic manager does not return any URL.

Multivalue

The Multivalue traffic-routing method allows you to get multiple healthy endpoints in a single DNS query response. This enables the caller to do client-side retries with other endpoints in the event of a returned endpoint being unresponsive

Subnet

Select Subnet traffic-routing method to map sets of end-user IP address ranges to a specific endpoint within a Traffic Manager profile. When a request is received, the endpoint returned will be the one mapped for that request’s source IP address. 

I hope you find this information useful. Let me know your thoughts.