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There are several strategies and patterns employed by software architects and designers to make these complex systems easier to design, build, manage, and maintain.
Availability refers to how long your service is up and running without interruption. High availability, or highly available, refers to a service that’s up and running for a long period of time.
Resiliency refers to a system’s ability to stay operational during abnormal conditions.
These conditions include:
A load balancer distributes traffic evenly among each system in a pool. A load balancer can help you achieve both high availability and resiliency.
Azure Load Balancer is a load balancer service that Microsoft provides that helps take care of the maintenance for you. Load Balancer supports inbound and outbound scenarios, provides low latency and high throughput, and scales up to millions of flows for all Transmission Control Protocol (TCP) and User Datagram Protocol (UDP) applications. You can use Load Balancer with incoming internet traffic, internal traffic across Azure services, port forwarding for specific traffic, or outbound connectivity for VMs in your virtual network.
If all your traffic is HTTP, a potentially better option is to use Azure Application Gateway. Application Gateway is a load balancer designed for web applications. It uses Azure Load Balancer at the transport level (TCP) and applies sophisticated URL-based routing rules to support several advanced scenarios.
Here are some of the benefits of using Azure Application Gateway over a simple load balancer:
A content delivery network (CDN) is a distributed network of servers that can efficiently deliver web content to users. It is a way to get content to users in their local region to minimize latency. CDN can be hosted in Azure or any other location. You can cache content at strategically placed physical nodes across the world and provide better performance to end users.
DNS, or Domain Name System, is a way to map user-friendly names to their IP addresses.
Latency refers to the time it takes for data to travel over the network. Latency is typically measured in milliseconds. Factors such as the type of connection you use and how your application is designed can affect latency. But perhaps the biggest factor is distance.
Recall that Azure provides data centers in regions across the globe. One way to reduce latency is to provide exact copies of your service in more than one region. The following illustration shows an example of global deployment.
Traffic Manager uses the DNS server that’s closest to the user to direct user traffic to a globally distributed endpoint.
Traffic Manager doesn’t see the traffic that’s passed between the client and server. Rather, it directs the client web browser to a preferred endpoint. Traffic Manager can route traffic in a few different ways, such as to the endpoint with the lowest latency.
Azure Load Balancer distributes traffic within the same region to make your services more highly available and resilient. Traffic Manager works at the DNS level, and directs the client to a preferred endpoint. This endpoint can be to the region that’s closest to your user.
Load Balancer and Traffic Manager both help make your services more resilient, but in slightly different ways. When Load Balancer detects an unresponsive VM, it directs traffic to other VMs in the pool. Traffic Manager monitors the health of your endpoints. When Traffic Manager finds an unresponsive endpoint, it directs traffic to the next closest endpoint that is responsive.
You learned just a few ways Azure networking can help reduce latency and make your apps and services more highly available.