In the first blog post in our series, we covered NetScaler App Delivery and Security service’s advanced GSLB capabilities and a use case for creating a disaster recovery site in a public cloud for your existing on-prem data center. In this post, we will dive into two additional use cases.

Even Distribution of Users Across Datacenters with Stickiness

Use Case 2: Round-robin distribution of users across sites spread globally, ensuring consecutive requests go to the same data center.

First, create a multi-site app with NetScaler App Delivery and Security service in GSLB active-active mode, evenly distributing traffic across sites. You also need to configure stickiness, which will ensure user sessions are persistent in a particular data center. Please note, you can find detailed guidance in our product documentation, and the following steps are specific to this use case.

Specify the Application Site Details

Add two or more sites for an active-active deployment.

Specify GSLB Parameters

Select Round Robin as the algorithm, as shown in Figure 1. Enable Stickiness with a time-to-live value of 120, as shown in Figure 2. This value controls the duration, in seconds, in which subsequent client requests to the multi-site app are sent to the same site.

Figure 1 (left): Select GSLB configuration (Round Robin); Figure 2 (right): Enable site persistence with NetScaler App Delivery and Security service stickiness settings

Figure 3: NetScaler App Delivery and Security service active-active deployment scenario with Round Robin algorithm with site stickiness

As shown in Figure 3, individual client DNS requests are served with the addresses of sites in a round-robin way across all the data centers. When the first site (the on-prem data center, in this case) goes down, clients are redirected to the next data center in the round-robin queue. Once the site is back up, client traffic continues to the currently selected site until the client stickiness time of 120 seconds is not expired. Over time, clients are distributed across all the healthy data centers.

Please note, you can control the distribution of traffic across your data centers by using weights for each site. For example, you can assign a weight of 90 to site 1 and a weight of 10 to site 2. Weights are proportional. Here, 90 percent of traffic is received by site 1 and 10 percent by site 2. You can change this to control the distribution of traffic to your data centers.

Optimal Site Selection with Advanced GSLB Capabilities

Use Case 3: Route users to the optimally performing site, regardless of location proximity.

In this use case, you are creating a multisite app with NetScaler App Delivery and Security service in GSLB active-active mode and with advanced GSLB capabilities so you can optimally route users to your site. Detailed guidance for this use case is available in our product documentation, and the steps that follow are specific this use case.

Specify Application Site Details

Add two or more sites for active-active deployment.

Specify GSLB Parameters

Select Optimal RTT as the algorithm, as shown in Figure 4. This option is only available for managed sites and user-defined sites with radar enabled. (Learn more in our product documentation.)

Figure 4 (left): Select GSLB configuration (Optimal RTT); Figure 5 (right): Penalty settings for sites with Optimal RTT GSLB configuration

You can penalize a site by adding additional latency (Figure 5). When you add a penalty to a site, its additional latency is added to the one already calculated as part of the real-user measurements.

Figure 6: NetScaler App Delivery and Security service active-active deployment scenario with Optimal RTT algorithm

When a site goes down, as shown in Figure 6, users are redirected to the next available optimal site. Once the site recovers, users are redistributed to their optimal site, which is determined dynamically.

Figure 7: Optimal site selection

As shown in Figure 7, even if a user’s physical location is closer to site 2, the user will be directed to site 1 if it has lower application latency (response time in milliseconds) when compared with site 2.

Geo-Based Traffic Steering

Create a multi-site application with Citrix App Delivery and Security service and configure geo-based site preference.

Specify the App Site Details

Add two or more sites for deployment. While adding a site, configure the geofencing for the site based on your preference.

Figure 8: Configure geofencing for site

As shown in Figure 8, all users accessing the application from the North American region will be served from a site located in San Francisco, per this configuration.

Learn More

In this blog series, we have looked at ways to ensure a fast and reliable user experience by balancing traffic across all your data sources — cloud and on-premises — with advanced GSLB as a service via NetScaler App Delivery and Security service.

Read Part 1 of our series, and try NetScaler App Delivery and Security Service today by logging into your cloud.citrix.com account and clicking Request Trial on the App Delivery and Security tile.