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Windows Azure Traffic Manager: Using Performance Load balancing method for multiple services in the same DC

Windows Azure Traffic Manager: Using Performance Load balancing method for multiple services in the same DC

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As you may know Windows Azure Traffic Manager (WATM) BETA is available. Windows Azure Traffic Manager is a load balancing solution that enables the distribution of incoming traffic among different hosted services in your Windows Azure subscription, regardless of their physical location. Traffic routing occurs as a the result of policies that you define and that are based on one of the following criteria:

  • Performance – traffic is forwarded to the closest hosted service in terms of network latency
  • Round Robin – traffic is distributed equally across all hosted services
  • Failover – traffic is sent to a primary service and, if this service goes offline, to the next available service in a list

 

More Info: http://msdn.microsoft.com/en-us/gg197529

 

Here is a scenario in which Windows Azure Traffic Manager (WATM) is used with “Performance” load balancing method:

 

For example, there are total 4 services hosted in 3 difference. Because there are 4 services in 3 DC so definitely 2 services will be in one same DC. The following table shows the distribution:

 

Entry #

Hosted Services

Data Center (DC)

Health Status

 Instances

#1

service1.cloudapp.net

North Central US

OK

1

#2

service2.cloudapp.net

East Asia

OK

1

#3

service3.cloudapp.net

East Asia

OK

1

#4

service4.cloudapp.net

North Europe

OK

1

 

Traffic Manager Policy: mywatmpolicy.ctp.trafficmgr.com

 

which hosted service will be returned to client?

 

For above scenario in which same services in hosted in multiple DC, “performance” load balancing method is best as it is used for geo-distributed scenario.

 

In above scenario where two same services are hosted in same DC are no supported in Windows Azure Traffic Manager (WATM) CTP. In above example, only one hosted service (either #2 or #3) will get all traffic disregarding the order they are displayed in the UI.

 

Suggestion: Instead of creating additional hosted services in the same region, you must increase the number of instances of just one hosted service in the region.

 

Entry #

Hosted Services

Data Center (DC)

Health Status

 Instances

#1

service1.cloudapp.net

North Central US

OK

1

#2

service2.cloudapp.net

East Asia

OK

2

#3

service4.cloudapp.net

North Europe

OK

1

 

 

You may ask, if the limitation to have more than one hosted service in the same DC is not currently supported applied only to "Performance". So yes, this limitation is only for performance method of WATM however, there are no limitations for round robin, all hosted services are treated equally regardless their region. If you choose "Round Robin" setting in WATM, then you can use more than one Hosted Service in the same region and configure with WATM.

 

 

If you have multiple hosted service in the same DC with WATM Performance setting then there are a few things you must know:

  1. Only one hosted service will get all traffic and other(s) will have none
  2. You will have no control over which one (out of many) hosted service will get the traffic, from the UI

 

 

 

 

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  • Do you know why TM resolves not the nearest service's IP for some clients? For example, a client is located in Europe, but TM resolves service.trafficmanager.net to service1.cloudapp.net (North Central US) instead of service4.cloudapp.net (Europe) but for this same client reaching service4.cloudapp.net works noticeably faster. I guess this could have something to do with how DNS server at client's ISP network is configured, right? If so, using a custom traffic manager at the application level would work more accurately (or a combination of these two approaches)...

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