Comparing Amazon ALB and SAP Web Dispatcher for Load Balancing in SAP Systems

Load Balancing Solutions for SAP FIORI Access

Introduction

In modern SAP environments, load balancing plays a critical role in ensuring optimal performance, scalability, and security. With the transition from SAP GUI to web-based access via SAP FIORI, businesses need robust solutions to handle web traffic efficiently. Traditionally, SAP Web Dispatcher has been the go-to choice for distributing workloads. However, AWS offers the Amazon Application Load Balancer (ALB) as a cloud-native alternative with enhanced capabilities, better scalability, and seamless integration with AWS services.

This article compares SAP Web Dispatcher and Amazon ALB, outlining their features, differences, and key considerations when choosing a load balancing solution for SAP workloads.

Understanding Amazon Application Load Balancer (ALB)

Amazon ALB operates at Layer 7 (Application Layer) of the OSI model, offering advanced request routing based on listener rules. It intelligently directs traffic based on request parameters such as hostnames, paths, HTTP headers, and query strings.

Key Features of AWS ALB:

1. HTTPS Termination: Handles SSL offloading, reducing processing load on backend servers.

2. Session Persistence: Ensures user requests stay connected to the same backend server.

3. HTTP/2 Support: Enables efficient request multiplexing.

4. SNI (Server Name Indication): Routes HTTPS traffic intelligently.

5. Scalability & High Availability: Dynamically scales and integrates with AWS services like CloudFront, WAF, and CloudWatch.

AWS ALB is an AWS-managed service, ensuring minimal maintenance while benefiting from Amazon’s security infrastructure.

SAP Web Dispatcher: A Traditional Load Balancer for SAP

SAP Web Dispatcher is a reverse proxy designed for SAP workloads, ensuring secure communication between web clients and backend SAP servers. It distributes requests to SAP applications, balancing the load while enhancing security.

Key Features of SAP Web Dispatcher:

1. Load Distribution: Uses round-robin, weighted round-robin, and adaptive load balancing techniques.

2. Web Caching: Improves performance by storing frequently requested content.

3. Custom HTTP Headers & Request Manipulation: Allows modification of request parameters before forwarding.

4. Support for Web Sockets: Enables RFC communication over HTTP/WebSocket.

5. Configurable Scalability: Can be tuned for proactive or reactive scaling.

SAP Web Dispatcher requires manual patching and updates, increasing operational overhead.

Solution Overview

To derive the recommended solution, it is imperative for us to go through important sets of functionalities and their descriptions for a load balancer, in this case an SAP Web Dispatcher, and an Amazon ALB.

Same Functionality Between SAP Web Dispatcher and Amazon ALB

Functionality Description Application Load Balancer SAP Web Dispatcher HTTPS Termination Intercepts encrypted HTTPS traffic when a server receives data from a secure socket layer (SSL) connection in an SSL session. SSL termination or SSL offloading decrypts and verifies data on the load balancer instead of the application server. Yes Yes Session Persistence Session stickiness, a.k.a., session persistence, is a process in which a load balancer creates an affinity between a client and a specific network server for the duration of a session (i.e., the time a specific IP spends on a website). Yes Yes Support for HTTP/2 An HTTP/2 load balancer must be capable of understanding and effectively handling HTTP/2 traffic, which includes features like multiplexing multiple requests over a single connection, prioritization of requests, and header compression. Yes Yes Server Name Indication (SNI) An SNI (Server Name Indication) load balancer inspects the hostname requested in the TLS handshake and intelligently routes HTTPS traffic to the appropriate backend server hosting that website or service, rather than relying only on IP addresses and ports. Yes Yes Multiple Systems Routing Distributes incoming network traffic across multiple systems or servers based on certain routing criteria. This type of load balancer is commonly used in distributed systems or large-scale applications to achieve high availability, scalability, and reliability. Yes Yes HTTP Header-based Routing HTTP Header-based Routing load balancing refers to a method of distributing incoming HTTP requests across multiple backend servers or systems based on information contained within the HTTP headers of the incoming requests. Yes Yes HTTP Method-based Routing HTTP Method-based Routing load balancing is a method where incoming HTTP requests are distributed across multiple backend servers or systems based on the HTTP method (such as GET, POST, PUT, DELETE, etc.) used in the request. Yes Yes mTLS An mTLS load balancer is capable of terminating and initiating mutual TLS connections, requiring cryptographic certificates to authenticate both clients and backend servers. By enforcing encryption and mutual authentication, mTLS load balancers provide end-to-end security for sensitive applications. Yes Yes

7. Exclusive Functionality Between SAP Web Dispatcher and ALB

Functionality Description Application Load Balancer SAP Web Dispatcher Load Balancing Algorithm A load balancing algorithm is a method or strategy used by load balancers to distribute incoming network traffic across multiple servers or resources in a balanced and efficient manner. Common algorithms include Round Robin, Least Connections, IP Hash, and Weighted Round Robin. Round-robin, Least-outstanding-Request, Automatic target weights Simple Round-robin, Weighted-round-robin, Adaptive Web Caching Caching capabilities to optimize the delivery of web content, improve scalability, and enhance the performance of web applications. Possible with Amazon CloudFront Yes Custom HTTP Headers The ability of the load balancer to add certain headers by default to all HTTP(S) requests and responses that it proxies between backends and clients. Possible with Amazon CloudFront Yes Request Manipulation Modifies or manipulates incoming HTTP requests before forwarding them to backend servers, including altering headers, parameters, payloads, or destination URLs to meet specific requirements. No Yes URL Filtering Involves defining rules or patterns to inspect the URLs of incoming requests and then making routing decisions based on those rules. This enables traffic direction to specific backend systems or services based on URL characteristics. Possible with AWS Web Application Firewall (WAF) Yes Support of Web Sockets for RFC Allows calling remote-enabled function modules (RFMs) over HTTP/WebSocket without requiring VPN connections. WebSocket is upgraded HTTP, allowing the use of reverse proxies, routers, etc., instead of SAProuter. Yes (ABAP-ABAP connections only, no multiplexing, potential performance penalty) Yes High-Availability (in-built) Ensures continuous operation and minimal downtime, even in the event of hardware failures, software glitches, or other disruptions, maintaining uninterrupted service availability. Yes No Scalability Dynamically adjusts resources or capacity to handle increasing traffic levels and growing demands on the system, ensuring optimal performance and resource utilization at all times. Adaptive (Non-configurable) Configurable (proactive/reactive) Native Integration with AWS Services Seamless integration with services like AWS CloudFront, AWS CloudWatch, Amazon Certificate Manager (ACM), and AWS Web Application Firewall (WAF). Yes No Maintenance and Operations Maintenance and operations related to load balancers, such as regular updates and patching, to ensure continued availability, performance, and security of applications and services. AWS Managed Customer-managed

8. Decision Matrix

Based on the functionalities, the following decision matrix can help determine the best load balancing solution for your SAP workloads on AWS:

For scenarios fully covered by the shared functionalities (as shown in Table 1.1), Amazon ALB is the preferred choice. For exclusive functionalities (as shown in Table 1.2) needed in specific cases, deploying ALB behind SAP Web Dispatchers can offer the best of both worlds. For non-critical workloads, the choice between ALB and Web Dispatcher depends on operational convenience and specific requirements.

Conclusion

Choosing the right load balancing solution for SAP workloads depends on specific business requirements. AWS ALB offers cloud-native scalability, security, and seamless AWS integration, making it a preferred choice for modern SAP deployments. Meanwhile, SAP Web Dispatcher provides advanced SAP-specific routing and caching, making it useful for SAP-centric environments.

For businesses moving towards SAP on AWS, leveraging AWS ALB ensures cost optimization, automation, and reduced operational overhead. In contrast, SAP Web Dispatcher remains relevant for legacy SAP environments requiring custom request manipulation.

By understanding the strengths of each solution, businesses can strategically optimize their SAP architecture to enhance performance, security, and cost-efficiency.

Exploring The Power Of SAP Technology, companies can ensure seamless cloud adoption and enhanced operational resilience.

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