This guide provides information about the Global server load balancing (GSLB) using NSX Advanced Load Balancer, which provides load balancing of applications across multiple geographically dispersed locations while providing centralized configuration, application monitoring, and analytics.

GSLB in NSX Advanced Load Balancer balances an application’s load across instances of the application that are deployed to multiple locations (typically, multiple data centers and/or public clouds). NSX Advanced Load Balancer or a third-party Application Delivery Controller (ADC) solution, manages application load at each of those locations.

GSLB is usually implemented to achieve the following application goals:

  • Provide optimal application experience to users/clients who are in geographically distributed areas

  • Offer resilience to loss of a data center or a network connection

  • Perform non-disruptive migration to or addition of another data center

GSLB Overview

GSLB includes the following functions::

  1. It selects the location (data center/cloud) to which the client's requests will be directed

  2. It monitors the health of the virtual services to select the best location (i.e., rule out unhealthy ones)

  3. It synchronizes configuration and state across GSLB sites so that function 1 and function2 can continue despite certain failures

When a client (typically a browser) performs a DNS query on Fully Qualified Domain Names (FQDNs), GSLB responds with the IP address (VIP) of the optimal application instance. The optimal address can and will change based on the load balancing algorithm, health of the application instances, and the location of the clients.

GSLB Use Cases

Here are a few use cases for NSX Advanced Load Balancer GSLB:

  • Optimal application experience for geographically distributed users

    • Applications are deployed in multiple data centers.

    • GSLB can redirect user request to the most optimal location.

  • Application high availability across data center

    • Applications are deployed in multiple data centers.

    • In case of a data center failure, application instances running in the remaining data center(s) can take over the user traffic.

  • Disaster recovery

    • Applications are deployed in two data centers.

    • While both are healthy, all traffic is directed to the primary DC.

    • If the primary DC fails, the global DNS directs all user traffic to the other.

  • Hybrid cloud with cloud bursting (shown below)

    • Applications are deployed across private and public clouds.

    • When/if an application experience an unusually high request load, NSX Advanced Load Balancer GSLB bursts to the public cloud site to absorb the load.

How NSX Advanced Load Balancer GSLB Works

As an example, refer to the following figure:

Figure 1. FQDN address resolution
  • The NSX Advanced Load Balancer is running in four locations (GSLB sites), three of which are on-premises, and one in Amazon Web Services (AWS). Each site has its own NSX Advanced Load Balancer Controller cluster (represented by a single Controller icon).

  • Application “A” has virtual services running in all four locations. These virtual services are identified by VS-A1 through VS-A4.

  • Three of the four locations (DC-1, DC-2, and AWS) have global DNS services (DNS-1, DNS-2, and DNS4) that are synchronized. They are all equally authoritative for the subdomain

  • The fourth site (DC-3) does not run a global DNS service.