When you wish to protect VMs or web apps across regions, for example, East US and West US, you cannot use Azure Load Balancer. Instead, we can use Azure Traffic Manager. Azure Traffic Manager is essentially a DNS router.
This means that unlike Load Balancer, which directs the flow of IP traffic from one address to another, Traffic Manager works by resolving a DNS entry, such as a web address, so a different backend IP address is used, as in the following diagram:
Figure 8.17 – Azure Traffic Manager
This enables us to direct users to the closest server available. Thus, traffic is distributed based on the user location. If a particular region becomes unavailable, then all traffic will be directed to a healthy region.
With Azure Traffic Manager, we have several different options available for defining how to direct traffic and the two just mentioned. They are as follows:
- Weighted: Each endpoint is given a weight between 1 and 1,000. Endpoints are randomly assigned but send more traffic to the higher-weighted endpoints.
- Priority: Defines a list of endpoints in priority order. All traffic goes to one point until that point degrades; traffic then gets routed to the next highest priority.
- Performance: Uses an internet latency table to send traffic to the fastest endpoint for the user.
- Geographic: Directed to endpoints based on the user’s geographic location.
- Multivalue: Traffic Manager sends multiple healthy endpoints to the client. The client can then try each endpoint in turn and is responsible for determining which is the best to use.
- Subnet: Route based on a user’s subnet. Useful for directing corporate users (that is, those whereby you can pre-determine which network they are on, such as an office location).
Application Gateway
Azure Application Gateway is a web traffic load balancer that can manage traffic to web applications. This web traffic load balancer operates at the application layer (Layer 7 in the OSI network reference stack).
It offers web load balancing, which is for HTTP(S) only. Traditional load balancers operate at the transport layer (Layer 4 in the OSI network reference stack) and route traffic – based on the source IP address and a port number – to a destination IP address and a port number. With Azure Application Gateway, traffic can be routed based on the incoming URL as well. For instance, if /pictures is part of the incoming URL, traffic can be routed to a particular set of servers that have been configured explicitly for pictures. If /audio is part of the incoming URL, the traffic is routed to another set of servers, configured specifically for audio files. The following diagram shows the workflow of Azure Application Gateway:
Figure 8.18 – Azure Application Gateway
Leave a Reply