Windows Azure Traffic Manager (5) Traffic Manager overview

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The author silently looked at the previous written traffic manager content, has been almost 3 years ago the article. Now that Azure traffic manager has a new feature, it's time to look at the relevant content during the weekend, and take a note to summarize this.

First 1th, the author does not agree that the traffic manager written on the Azure official website is load balanced:

Traffic manager is considered to be the most intelligent DNS resolution (smart DNS). The user's request is routed to the appropriate node server according to a certain rule ( performance, cyclic method, failover ).

  Traffic Manager can help customers:

- provides the availability of critical applications. When we use a DNS hosting public cloud service, all the compute nodes where the azure load balancer resides are in the same datacenter. If the data center goes down, the Azure public cloud service goes down. We can use Azure traffic Manager for high availability across datacenters.

- provides responsiveness to high-performance applications. Suppose we deploy cloud-based applications that are user-facing across the country and require good user responsiveness. If I only deployed the app to the Azure Shanghai Datacenter, the speed of user access in the north could be impacted. With azure traffic Manager, we can route the user's request to the nearest Azure datacenter, such as a user request from the north to the Beijing Data center, and a user request from the south to the Shanghai data Center.

- perform upgrades and service maintenance in the event of a non-stop machine. Traffic Manager backend endpoint need to be upgraded, you can temporarily disable the endpoint in Traffic manager management. Wait until the endpoint upgrade is complete and re-enable it in Traffic manager. This ensures that the client maintains and upgrades the Azure cloud service without downtime.

-Traffic allocation for large, complex deployments. Azure traffic Manager is nested so that one traffic manager can be added as endpoint to another traffic manager. Provides a more load-carrying deployment. (up to 10 layers can be nested)

  How Traffic Manager works:

When configuring the Traffic Manager profile, the settings specified will provide traffic Manager with the information needed to determine which endpoint should service the request based on the DNS query. Actual endpoint traffic is not routed through traffic Manager.

Illustrates the specific way of working:

user traffic points to the company domain name : Client request information using the company domain name. The goal is to resolve the DNS name to an IP address. The corporate domain must be retained through normal Internet domain name registrations that are maintained outside of traffic Manager. In Figure 1, the sample company domain is www.contoso.com.

company domain name points to the traffic manager domain name : The DNS resource record for the corporate domain points to the Traffic manager domain name that is maintained in Azure traffic manager. This is accomplished using a CNAME resource record that maps the company domain name to the traffic Manager domain name. In this example, the traffic Manager domain name is contoso.trafficmanager.net.

Traffic Manager Domain name and profile : The Traffic Manager Domain name is part of the Traffic Manager configuration file. The user's DNS server sends a new DNS query for the Traffic Manager domain name ( contoso.trafficmanager.netin this example), which is received by the traffic manager DNS name server.

Traffic Manager Profile rule processed : Traffic Manager uses the specified load balancing method and monitoring state to determine which Azure endpoint should service the request.

endpoint domain name sent to the user : Traffic manager returns a CNAME record that maps the traffic manager domain name to the domain name of the endpoint. The user's DNS server resolves the endpoint domain name to its IP address and sends the address to the user.

user Invoke Endpoint : The user invokes the endpoint directly using the IP address of the returned endpoint.

Because the corporate domain and the resolved IP address are cached on the client computer, the user will continue to interact with the selected endpoint until the endpoint's local DNS cache expires. In particular, it is important to note that the duration of the DNS client cache DNS host entries is the time-to-live (TTL) of these entries. Retrieving host entries from the DNS client cache bypasses the traffic Manager configuration file, and if the endpoint becomes unavailable before the TTL expires, you may experience connection delays. If the TTL of the DNS host entry in the cache expires, and the client computer needs to resolve the company domain name again, the computer sends a new DNS query. Depending on the load balancing method applied and the health of the endpoint at the time of the request, the client computer may receive IP addresses from different endpoints.

How to implement Traffic Manager

Deploy an Azure cloud service, Azure Web site, or other endpoint to a production environment. When you create a traffic Manager profile, you must associate it with a subscription. Then, in the production environment, add the endpoints that belong to the same subscription for the cloud service and the standard tier site. If an endpoint is in a staging environment and not in an Azure production environment or in the same subscription, you cannot add it as an external endpoint.

determines the name of the traffic Manager domain. consider using a name with a unique prefix for the domain. The second half of the field (that is,   trafficmanager.net ) is fixed.

determines the monitoring configuration to use. regardless of which load-balancing method is used, traffic Manager monitors endpoints to ensure they are online. After you configure monitoring settings, traffic Manager does not direct traffic to endpoints that the monitoring system determines to be offline, unless it detects that all endpoints are offline or cannot detect the state of any of the endpoints contained in the configuration file.

determines the load balancing method to use. The has three different load-balancing methods. Take the time to understand which method best meets your requirements. You can change the method at any time later. Also note that each method requires a slightly different configuration step.

Create the configuration file and configure the settings. The can use the REST API, Windows PowerShell, or the management portal to create a traffic manager profile and configure settings to test the traffic manager profile. test that your profile and domain are working as expected.

using the example in Figure 1, change the DNS resource record on the server to include the following line to point the company domain name to the traffic Manager domain name:

    www.contoso.com in CNAME contoso.trafficmanager.net

Reference:https://msdn.microsoft.com/zh-cn/library/azure/hh744833.aspx

Windows Azure Traffic Manager (5) Traffic Manager overview