Intro

Azure Traffic Manager is a DNS-based traffic load balancer. This service allows you to distribute traffic to your public facing applications across the global Azure regions. 

Documentation

• Traffic Manager documentation

• Understand Azure Load Balancing - Read here to determine which Azure load balancer makes sense

Tips and Tidbits

• DNS-based traffic load balancer that enables you to distribute traffic optimally to services across global Azure regions, while providing high availability and responsiveness.

• Traffic Manager uses DNS to direct the client requests to the appropriate service endpoint based on a traffic-routing method.

  • Clients connect to the selected endpoint directly.

  • Traffic Manager is not a proxy or a gateway.

  • Traffic Manager does not see the traffic passing between the client and the service.

• Traffic Manager works at the DNS level which is at the Application layer (Layer-7).

• It uses DNS to determine the nearest Azure datacenter to which external traffic should be routed.

• Because Traffic Manager is a DNS-based load-balancing service, it load-balances only at the domain level.

  • For that reason, it can't fail over as quickly as Front Door, because of common challenges around DNS caching and systems not honoring DNS time-to-live values (TTLs).

• Traffic manager also provides health monitoring for every endpoint.

• A recursive DNS service, sometimes called a 'local DNS' service, does not host DNS domains directly.

  • Rather, the client off-loads the work of contacting the various authoritative DNS services across the Internet needed to resolve a DNS name.

  • The recursive DNS service caches the DNS responses it receives.

• The DNS resolver on the client device also caches the result.

  • Caching enables subsequent DNS queries to be answered more quickly by using data from the cache rather than querying other name servers.

  • The duration of the cache is determined by the 'time-to-live' (TTL) property of each DNS record.

• Traffic Manager selects an endpoint based on the configured traffic-routing method.

• Traffic Manager supports a range of traffic-routing methods to suit different application needs.

• Once the endpoint is selected the clients then connect directly to the appropriate service endpoint.

Traffic Manager Routing Methods

• Traffic routing methods

• Azure Traffic Manager supports six traffic-routing methods to determine how to route network traffic to the various service endpoints.

• For any profile, Traffic Manager applies the traffic-routing method associated to it to each DNS query it receives.

• The traffic-routing method determines which endpoint is returned in the DNS response.

Priority routing

• Select this routing method when you want to have a primary service endpoint for all traffic.

  • You can provide multiple backup endpoints in case the primary or one of the backup endpoints is unavailable.

• When a Traffic Manager profile is configured for priority routing it contains a prioritized list of service endpoints.

  • Traffic Manager sends all traffic to the primary (highest-priority) endpoint first. If the primary endpoint is not available, Traffic Manager routes the traffic to the second endpoint, and so on.

  • Availability of the endpoint is based on the configured status (enabled or disabled) and the ongoing endpoint monitoring.

  • The Priority traffic routing method allows you to easily implement a failover pattern.

Open

Weighted routing

• Select this routing method when you want to distribute traffic across a set of endpoints based on their weight.

• Set the weight the same to distribute evenly across all endpoints

Open

Performance routing

• Select the routing method when you have endpoints in different geographic locations, and you want end users to use the "closest" endpoint for the lowest network latency.

• The Performance routing method is designed to improve the responsiveness by routing traffic to the location that is closest to the user.

• The closest endpoint is not necessarily measured by geographic distance. Instead Traffic Manager determines closeness by measuring network latency.

Open

Geographic routing

• Select this routing method to direct users to specific endpoints (Azure, External, or Nested) based on where their DNS queries originate from geographically.

  • With this routing method, it enables you to be compliant with scenarios such as data sovereignty mandates, localization of content & user experience and measuring traffic from different regions.

• When a Traffic Manager profile is configured for Geographic routing, each endpoint associated with that profile needs will have a set of geographic locations assigned to it.

  • Any requests from those regions gets routed only to that endpoint.

  • Some planning is required when you create a geographical endpoint.

  • A location cannot be in more than one endpoint.

• based on the geographic location their DNS query originates from.

  • IP address used to determine the region isn't the client's IP address, but rather the IP address of the recursive DNS service.

• enables you to be in compliance with data sovereignty mandates, localization of content & user experience and measuring traffic from different regions.

A geographic region can be at following levels of granularity

• World– any region

• Regional Grouping – for example, Africa, Middle East, Australia/Pacific etc.

• Country/Region – for example, Ireland, Peru, Hong Kong SAR etc.

• State/Province – for example, USA-California, Australia-Queensland, Canada-Alberta etc. (note: this granularity level is supported only for states / provinces in Australia, Canada, and USA).

Open

MultiValue

• Select this routing method for Traffic Manager profiles that can only have IPv4/IPv6 addresses as endpoints.

• When a query is received for this profile, all healthy endpoints are returned.

Subnet

• Select this routing method to map sets of end-user IP address ranges to a specific endpoint.

• When a request is received, the endpoint returned will be the one mapped for that request’s source IP address.

Load Balancing

• Understand Azure load balancing - Pay attention to the global vs regional use and the type of traffic.

• The following table summarizes the Azure load balancing services by these categories:

Traffic Manager endpoint monitoring

• Traffic Manager endpoint monitoring

• Azure Traffic Manager includes built-in endpoint monitoring and automatic endpoint failover.

  • This feature helps you deliver high-availability applications that are resilient to endpoint failure, including Azure region failures

  • When the monitoring protocol is set as HTTP or HTTPS, the Traffic Manager probing agent makes a GET request to the endpoint using the protocol, port, and relative path given. An endpoint is considered healthy if probing agent receives a 200-OK response, or any of the responses configured in the Expected status code ranges.

Nested Traffic Manager profiles

• Each Traffic Manager profile can only specify one traffic-routing method.

• However, you may have scenarios that require more complicated traffic routing than the routing that can be provided by a single Traffic Manager profile.

• In these situations, you can combine traffic routing methods by using nested Traffic Manager profiles to gain the benefits of multiple traffic-routing methods.

• Nested profiles enable you to override the default Traffic Manager behavior to support larger and more complex traffic-routing configurations for your application deployments.

Open

see Nested Traffic Manager profiles.

• Each Traffic Manager profile specifies a single traffic-routing method.

• Suppose that you deployed an application in the following Azure regions: West US, West Europe, and East Asia.

• You use Traffic Manager's 'Performance' traffic-routing method to distribute traffic to the region closest to the user.

• You want to use the 'weighted' traffic-routing method to direct a small percentage of traffic to your test deployment.

Open

• In this configuration, traffic directed via the parent profile distributes traffic across regions normally.

• Within West Europe, the nested profile distributes traffic to the production and test endpoints according to the weights assigned.

• 'MinChildEndpoints' determines the minimum number of available endpoints in the child profile.

Traffic Manager endpoints

• Azure Traffic Manager enables you to control how network traffic is distributed to application deployments running in your different datacenters.

  • You configure each application deployment as an endpoint in Traffic Manager.

  • When Traffic Manager receives a DNS request, it chooses an available endpoint to return in the DNS response.

  • Traffic manager bases the choice on the current endpoint status and the traffic-routing method.

Traffic Manager supports three types of endpoints:

• Azure endpoints - Use this type of endpoint to load-balance traffic to a cloud service, web app, or public IP address in the same subscription within Azure.

• External endpoints - Use this type of endpoint to load balance traffic for IPv4/IPv6 addresses, FQDNs, or for services hosted outside Azure. These services can either be on-premises or with a different hosting provider.

• Nested endpoints - Use this type of endpoint to combine Traffic Manager profiles to create more flexible traffic-routing schemes to support the needs of larger, more complex deployments. With Nested endpoints, a child profile is added as an endpoint to a parent profile. Both the child and parent profiles can contain other endpoints of any type, including other nested profiles.

Configuring endpoint monitoring

• Azure Traffic Manager includes built-in endpoint monitoring and automatic endpoint failover.

• HTTPS monitoring doesn't verify whether your TLS/SSL certificate is valid; it only checks that the certificate is present.

• Custom Header settings: This configuration setting helps you add specific HTTP headers to the health checks that Traffic Manager sends to endpoints under a profile.

  • The custom headers can be specified at a profile level to be applicable for all endpoints in that profile and / or at an endpoint level applicable only to that endpoint.

  • You can use custom headers for health checks of endpoints in a multi-tenant environment.

  • That way it can be routed correctly to their destination by specifying a host header.

  • You can also use this setting by adding unique headers that can be used to identify Traffic Manager originated HTTP(S) requests and processes them differently.

  • You can specify up to eight header:value pairs separated by a comma. Example - header1:value1, header2:value2
    
    

• For HTTP or HTTPS monitoring protocol, a common practice on the endpoint side is to implement a custom page within your application - for example, /health.aspx.

  • Using this path for monitoring, you can perform application-specific checks, such as checking performance counters or verifying database availability.

  • Based on these custom checks, the page returns an appropriate HTTP status code.

Configure a custom domain name in Azure App Service with Traffic Manager integration

• Configure a custom domain name in Azure App Service with Traffic Manager integration

• When you use Azure Traffic Manager to load balance traffic to Azure App Service, the App Service app can be accessed using <traffic-manager-endpoint>.trafficmanager.net.

• You can assign a custom domain name, such as http://www.contoso.com , with your App Service app in order to provide a more recognizable domain name for your users.

• To map a custom DNS name to an app that's integrated with Azure Traffic Manager, the web app's App Service plan must be in Standard tier or higher.

• Create the CNAME mapping

  • Sign in to the website of your domain provider.

  • Find the page for managing DNS records.

  • Create a CNAME map from a non-root custom domain name (such as www.contoso.com) to the Traffic Manager domain name (contoso.trafficmanager.net) that's integrated with your app.

• Since Traffic Manager only supports custom domain mapping with CNAME records, and because DNS standards don't support CNAME records for mapping root domains (for example, http://contoso.com ), Traffic Manager doesn't support mapping to root domains.

•