#cloud #microsoft #iam “An application is only as reliable as its least reliable component”

f5friday

It’s unlikely there’s anyone in IT today that doesn’t understand the role of load balancing to scale. Whether cloud or not, load balancing is the key mechanism through which load is distributed to ensure horizontal scale of applications. It’s also unlikely there’s anyone in IT that doesn’t understand the relationship between load balancing and high-availability (reliability). High-Availability (HA) architectures are almost always implemented using load balancing services to ensure seamless transition from one service instance to another in the event of a failure.

What’s often overlooked is that scalability and HA isn’t important just for applications. Services – whether application or network-focused – must also be reliable. It’s the old “only as strong as the weakest link in the chain” argument. An application is only as reliable as its least reliable component – and that includes services and infrastructure upon which that application relies. It is – or should be – ops first rule; the rule that guides design of data center architectures. 

This requirement becomes more and more obvious as emerging architectures combining the data center and cloud computing are implemented, particularly when federating identity and access services.  That’s because it is desirable to maintain control over the identity and access management processes that authenticate and authorize use of applications no matter where they may be deployed. Such an architecture relies heavily on the corporate identity store as the authoritative source of both credentials and permissions. This makes the corporate identity store a critical component in the application dependency chain, one that must necessarily be made as reliable as possible.

Which means you need load balancing.

A good example of how this architecture can be achieved is found in BIG-IP load balancing support for Microsoft’s Active Directory Federation Services (AD FS).

AD FS and F5 Load Balancing

Microsoft’s Active Directory Federation Services, (AD FS) sever role is an identity access solution that extends the single sign-on, (SSO) experience for directory-authenticated clients, (typically provided on the Intranet via Kerberos), to resources outside of the organization’s boundaries, such as cloud computing environments. To ensure high-availability, performance, and scalability the F5 BIG-IP Local Traffic Manager (LTM) can be deployed to load balance an AD FS server farm.

big-ip ad fs

There are several scenarios in which BIG-IP can load balance AD FS services.

1. To enable reliability of AD FS for internal clients accessing external resources, such as those hosted in Microsoft Office 365. This is the simplest of architectures and the most restrictive in terms of access for end-users as it is limited to only internal clients.

2. To enable reliability of AD FS and AD FS proxy servers, which provide external end-user SSO access to both internal federation-enabled resources as well as partner resources like Microsoft Office 365. This is a more flexible option as it serves both internal and external clients.

3. BIG-IP Access Policy Manager (APM) can replace the need for AD FS proxy servers required for external end-user SSO access, which eliminates another tier and enables pre-authentication at the perimeter, offering both the flexibility required (supporting both internal and external access) as well as a more secure deployment.

In all three scenarios, F5 BIG-IP serves as a strategic point of control in the architecture, assuring reliability and performance of services upon which applications are dependent, particularly those of authentication and authorization. Using BIG-IP APM instead of AD FS proxy servers both simplifies and makes more agile the architecture. This is because BIG-IP APM is inherently more programmable and flexible in terms of policy creation. BIG-IP APM, being deployed on the BIG-IP platform, can take full advantage of the context in which requests are made, ensuring that identity and access control go beyond simple credentials and take into consideration device, location, and other contextual-clues that enable a more secure system of authentication and authorization. High-availability – and ultimately scalability - is preserved for all services by leveraging the core load balancing and HA functionality of the BIG-IP platform.

All components in the chain are endowed with HA capabilities, making the entire application more resilient and able to withstand minor and major failures.

Using BIG-IP LTM for load balancing AD FS serves as an adaptable and extensible architectural foundation for a phased deployment approach. As a pilot phase, rolling out AD FS services for internal clients only makes sense, and is the simplest in terms of its implementation. Using BIG-IP as the foundation for such an architecture enables further expansion in subsequent phases, such as introducing BIG-IP APM in a phase two implementation that brings flexibility of access location to the table.

Further enhancements can then be made regarding access when context is included, enabling more complex and business-focused access policies to be implemented. Time-based restrictions on clients or location can be deployed and enforced, as is desired or needed by operations or business requirements.

Reliability is a Least Common Factor Problem

Reliability must be enabled throughout the application delivery chain to ultimately ensure reliability of each application. Scalability is further paramount for those dependent services, such as identity and access management, that are intended to be shared across multiple applications. While certainly there are many other load balancing services that could be used to enable reliability of these services, an extensible and highly scalable platform such as BIG-IP is required to ensure both reliability and scalability of shared services upon which many applications rely.

The advantage of a BIG-IP-based application delivery tier is that its core reliability and scalability services extend to any of the many services that can be deployed. By simplifying the architecture through application delivery service consolidation, organizations further enjoy the benefits of operational consistency that keeps management and maintenance costs reduced.

Reliability is a least common factor problem, and Ops First Rule should be applied when designing a deployment architecture to assure that all services in the delivery chain are as reliable as they can be.