Azure Traffic Manager not routing to correct data center

1
votes

We have deployed our Azure web application to two separate data centers (one located in West Europe and the other located in South east Asia) for purely performance reasons. We have a configured a Traffic Manager to route requests between these two DC's based on performance. However, when users in Shanghai try to access the site, they are routed to the DC in West Europe when ideally they should have been routed to SE Asia DC. Due to this, users in Shanghai are not seeing the intended performance benefit. However, it works well from India and Europe i.e. they are routed to the closest DC. What could be the problem? Also, is there a way to test traffic manager's performance based routing to see if it working as expected?

UPDATE:

I requested the users in Shanghai to use azure speed test to know the closest DC. They see "It looks like your nearest Data Center is West Europe. There appears to be a CDN Node nearer your location". When we use the above site from India, it shows "It looks like your nearest Data Center is Southeast Asia". My questions are:

Based on the above lookups, TM seems to be routing correctly even though India is closer to West Europe than Shanghai? What is the additional information "There appears to be a CDN Node nearer your location" after data center that is displayed when looked up from Shanghai that is not shown from India? Could this "CDN Node" be making the Shanghai users to detect West Europe as the closest DC?

1
azure

1 Answers

2
votes

I think you are confusing two different concepts:

  1. Physical proximity vs. network proximity (ie. latency)
  2. CDN vs. WATM

A user's physical geographic proximity to a datacenter is only marginally related to which datacenter will be fastest. Around the world there are different peering agreements, interconnects, etc that can cause a geographically closer datacenter to have worse latency/bandwidth to a user than a geographically farther datacenter. This is why it is always important to test the latency from your users' location rather than just assuming by looking at a map. The azurespeedtest site you used is a great way to check the real-world performance of a user to an Azure datacenter, and the fact that it shows the same results as WATM means that WATM is performing correctly and your users are getting the fastest speeds possible.

CDN is a cache layer for static content and has lots of nodes throughout the world (see http://msdn.microsoft.com/library/azure/gg680302.aspx), and these nodes are in no way related to Azure datacenters. CDN also has nothing to do with WATM or which datacenter WATM would point a specific user to. If you have a lot of static content then you may want to consider adding a CDN endpoint in front of your site in order to cache the content closer to your users. See http://msdn.microsoft.com/en-us/library/azure/ee795176.aspx for more info.