Global Server Load Balancing - Why it is Necessary

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Many organizations require their IT systems to be available 24/7, and some need to have their IT systems spread across different geographic regions like AMER, AMEA or APAC. In today’s hybrid world, application servers and other core server infrastructure often get deployed using a mix of traditional private data centers, public cloud platforms and private cloud infrastructure hosted by dedicated hosting companies.

This deployment model enables IT teams to deliver resilience and performance across their IT systems. Global server load balancing (GSLB) is a core component of achieving this resilience and performance across widely spread regions.

What is Global Server Load Balancing (GSLB)?

Global server load balancing is an advanced load balancing technique that helps deliver a consistent flow of network traffic between multiple data centers and cloud providers worldwide. With Global server load balancing systems in different regions, users can remain operational even if issues impact services in one geographic area.

For instance, if a cloud platform hosting one of your apps is unavailable in the AMER region, users can still use their applications and services via an EMEA or APAC location without making client configuration changes.

The Need for Global Server Load Balancing

Even modestly sized businesses now operate on regional and global scales. The need for global server load balancing extends beyond just the largest global multinational companies. Single markets, such as the EU, and large markets, like the USA, China and India, all boast large customer bases for businesses spread across vast geographic areas.

When a business has many users in a global region, its application infrastructure in that region could be taken offline due to technical issues or overwhelmed by the number of regional requests received.

Global server load balancing can route network traffic and user access requests between global data centers and cloud hosting locations based on user load. This allows the global server load balancing engine to spread the load across the available global resources and route requests to a remote data center further away if those servers are under a lower load and can respond more rapidly than a busy local server.

So, in the scenario where regional application delivery is overwhelmed by requests, the surplus access requests can be routed to another global region and application instance with the capacity to handle them. Users don’t need to change anything, as the GSLB software handles everything.

Benefits of GSLB

Global server load balancing delivers benefits across these areas:

Performance - Using GSLB across geographically spread sites means that each one gets monitored for performance issues, and traffic gets routed to other sites if a particular one is overloaded. Note that this is site routing based on the performance once the local load balancers at that site have spread the load across the server pool in the best way possible.

This routing of requests based on site performance helps deliver an optimal end-user application experience and delivers performance optimization with GSLB. It also means that IT teams don’t have to over-specify application delivery server infrastructure in a region for the rare occasions it is needed.

Scalability - The capability to distribute workload across various locations also enhances scalability. In scenarios where a specific site experiences a surge in traffic due to local events, it’s not necessary to increase the number of web servers in that area. Instead, excess traffic that the local servers cannot manage gets redirected to another location with available capacity.

This approach reduces the number of servers needed at each site over time, as organizations can manage traffic peaks at any site by using the collective resources of a worldwide server network. Consequently, this leads to more efficient use of existing infrastructure, improving return on investment and potentially reducing or avoiding the need for additional server investments at any given site.

Resilience - GSLB significantly simplifies business resilience and continuity through its support for disaster recovery failover mechanisms, including active-active and active-passive configurations across geographically dispersed sites and cloud services.

Regulatory Compliance - Many nations or international entities, such as the EU, impose data storage and transfer regulations. GSLB rules help with compliance by guaranteeing that users from specific regions connect only to servers in locations approved for their data storage. For instance, it connects EU-based users to EU servers rather than servers in the USA.

Key Features and Functionality

Global server load balancing builds on the core local load balancing functionality provided by load balancers. It is delivered at the infrastructure level by load-balancer server instances with additional software installed, enabling enhanced geographic load balancing functionality. GSLB builds on and enhances the load balancing functionality that shares access requests and connections across a local server pool to share them across multiple geographically spread server sites. These sites can be in the cloud or on-premises.

Global server load balancing on Progress Kemp LoadMaster extends the health-checking algorithms used to determine server health to perform advanced health checking at the site level. In this case, a site is any geographic location with server pools providing web and application servers for users or other systems. The health checking uses the Fully Qualified Domain Name (FQDN) for each site as the basis for traffic routing. If a site is unavailable or servers located within it are underperforming, then requests using that site’s FQDN are automatically routed to another site by rewriting the FQDN in the requests.

As such, GSLB is integrated with and relies on domain name system (DNS) functionality and will return the IP address of the server in a site that a connection should use. The end-user device (or other application services) then uses the newly supplied IP address to set up a connection and communicate with the application in the remote geographic location directly.

As with local site load balancing, GSLB can use multiple algorithms when determining how to route network traffic between sites. Algorithms used for GSLB routing and decision-making are round robin, weighted round robin, fixed weighting, real server load, location-based and proximity.

GSLB Algorithms

  • GSLB round robin load balancing can be used for all active sites and includes support for allocating weights to sites, plus supporting chained failover options for disaster recovery.
  • Location-based load balancing allows GSLB to direct a client to a site based on the client’s country or continent, as defined in policies.
  • Proximity takes location-based GSLB one step further and allows for longitude and latitude granularity in the location definition.
  • LoadMaster GSLB also offers a “Real Server Load” load balancing option that uses data center metrics provided by local LoadMaster instances to route client requests to the least busy site.

Our pages about GSLB and Kemp GEO contain general and technical overviews of LoadMaster GSLB.

Real-World Use Cases

Many organizations use global server load balancing, such as the GSLB in LoadMaster, to optimize global applications and provide other services to their staff and clients across broad geographic regions. One such organization is the Harris County District Attorney’s Office in Houston, Texas.

The Harris County District Attorney’s Office caters to a population of over four million people. To provide investigative and legal services effectively to this large community, it relies heavily on IT infrastructure for case management, services to constituents and tracking employee performance. These critical systems are required to be operational around the clock.

To provide continuous IT service delivery, they utilize two data center locations: a primary facility in Houston and a secondary, remote site managed by a hosting provider for failover capabilities. This backup site can offer all the primary site’s services in case of any disruptions that necessitate switching operations.

After thorough market research, the IT department of the Harris County DA Office chose the LoadMaster and its global server load balancing as the optimal solution to meet their specific needs. The team from Progress Professional Services collaborated with the DA Office’s IT staff to meticulously plan, select and implement the most suitable LoadMaster configuration to fulfill their requirements. Upon the project’s successful completion, Rurik Wilmot, the Senior Systems Administrator at Harris County, praised the Progress technical liaison for their deep expertise, approachability and readiness to assist during crucial times of making and testing changes in the production environment. Read more in this case study report.

There are more success stories on the LoadMaster Use Cases Pages.

Implementation Best Practices

Implementing global server load balancing requires careful strategic planning and a thorough understanding of GSLB technology and the specific application environments it will support. Here are some best practices (with LoadMaster as the load balancer and the GSLB solution):

  • Plan Carefully - Define your disaster recovery, performance or scaling needs. Assess your applications and the geographic spread of your users.
  • Don’t Forget DNS - Use a reliable DNS provider and strategically configure your network for proper IP addressing and secure communication.
  • Deploy Resilient LoadMaster Solutions - Install at least a pair of LoadMaster solutions in separate locations to deliver redundancy in GSLB. Configure LoadMaster GEO clustering and licensing, set up FQDNs and associate Virtual IPs.
  • Choose Your Algorithm - Pick a load balancing method (round robin, weighted, location-based, proximity, etc.) that best suits the applications needs.
  • Health Checks are Key - Thoroughly configure health checks to monitor servers and entire sites more accurately. Use different check types for robust coverage.
  • Resilience Matters - Plan for failover scenarios with backup sites and automatic failover mechanisms for more seamless service continuity.
  • Test and Monitor - Run simulations to test failover behavior and continually monitor your GSLB deployment to boost optimal performance.

Additionally, implementations of GSLB should meet the diverse needs of various application types. For example, the following app scenarios should have different setups:

  • E-commerce - Prioritize uptime and session persistence.
  • Streaming - Emphasize real-time performance.
  • Cloud - Use cloud-native features for flexibility.
  • Hybrid - Carefully integrate physical and cloud infrastructure.

Comparative Analysis

Global server load balancing doesn’t replace traditional server load balancing. As outlined above, it builds on the local load balancing done to distribute requests to a server pool in a data center or the cloud. The extension happens at the site level, which can be a data center or a regional cloud platform instance.

But in a true sense, GSLB extends traditional load balancing from a single-site solution to a global solution. Each organization’s definition of global will depend on its worldwide user footprint and where it needs to host and deliver services.

Challenges and Solutions

Implementing GSLB can be complicated in some scenarios which present unique challenges. Each challenge requires strategic solutions to overcome. The challenges include complex configuration, DNS integration difficulty, performance optimization across regions, compliance with data sovereignty laws and security concerns.

To address complex configuration issues, organizations can standardize configurations using templates and seek vendor support for streamlined setup. To integrate GSLB with DNS systems, utilize automated DNS management tools within GSLB solutions for a smoother integration.

Intelligent routing is necessary to deliver optimal application performance for a global user base. Implementing routing policies based on latency, server health, and geography can achieve this. To comply with local data protection regulations, configure GSLB to adhere to data residency laws, ensuring that traffic gets directed accordingly.

Expanding global reach increases exposure to security threats. To mitigate these risks, use encryption, deploy web application firewalls (WAF) and maintain strict access control.

Addressing these challenges with targeted solutions can help organizations effectively deploy GSLB. This will enhance global availability, performance and compliance while maintaining security.

Future Trends in GSLB

The usage of GSLB will continue to grow in importance, and the ways that the technology gets used will also change to accommodate the changing infrastructure landscape.

“It’s difficult to make predictions, especially about the future,” as the Danish folk saying goes, but here are some areas where GSLB could impact and change its usage pattern over the next few years.

  • The Cloud Transformation
  • ⁃ Deeper Cloud Integration - GSLB should become even more tightly integrated with cloud platforms (AWS, Azure, GCP), using cloud-native concepts for load balancing, auto-scaling and resilience.
    ⁃ Multi/Hybrid-Cloud Awareness - GSLB solutions will become standard for managing traffic across public, private and hybrid cloud environments.

  • Edge Computing Growth
  • ⁃ Distributed GSLB - GSLB will evolve to support distributed decision-making at the edge, allowing faster routing and lower latency for users accessing applications running on edge networks.

  • Increased Use of Machine Learning
  • ⁃ Intelligent Routing - GSLB will use artificial intelligence and machine learning for more sophisticated traffic steering based on real-time user behavior, network conditions and application health.
    ⁃ Predictive Analytics - Machine learning will enable GSLB systems to perform predictive failure analysis and proactive load balancing to avoid outages.

  • Focus on User Experience
  • - Performance-Centric Metrics - GSLB decision-making when routing requests will place greater emphasis on real-world user experience metrics like page load times and application responsiveness.
    - Content-Aware Routing - GSLB may consider the type of content requested, optimizing delivery for specific media formats or device types.

  • Enhanced Security
  • - Integrated Threat Protection - GSLB solutions will incorporate deeper security features, such as distributed denial-of-service (DDoS) mitigation and enhanced WAF capabilities.
    - Zero Trust Frameworks - GSLB will likely play a role in Zero Trust security models, facilitating secure access for geographically dispersed users.

To summarize, GSLB necessity will evolve into a more dynamic and intelligent solution, more seamlessly integrating cloud, AI and edge technologies. User experience and security will become central to its role in the ever-changing application delivery landscape.


GSLB offers numerous advantages, including superior performance for users accessing applications across diverse geographic hosting locations and reduced latency as users get directed to the nearest data center or cloud service. This setup facilitates high availability by distributing server infrastructure across multiple sites. However, this flexibility and the ensuing benefits add complexities in managing and coordinating data exchanges among various hosting locations while confirming if users consistently connect to the site, providing the optimal application experience. Global server load balancing streamlines the management of complex network infrastructure.

Learn more about Global Server Load Balancing in LoadMaster implementation via our datasheet and Global Server Load Balancing (GSLB) web page. You can also start a free trial of LoadMaster and contact us to discuss your application delivery needs.

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Doug Barney

Doug Barney was the founding editor of Redmond Magazine, Redmond Channel Partner, Redmond Developer News and Virtualization Review. Doug has also served as Executive Editor of Network World, Editor in Chief of AmigaWorld and Editor in Chief of Network Computing.