Chapter 2. Network Traffic Patterns: Application Layer

In the design of network architectures, it is essential to understand the applications used and the resulting network traffic injected into the environment. There are many classes of networked applications. This chapter focuses on Web-based applications that are predominant in the data center. Most Web-based applications can be partitioned into the following functional tiers:

• Presentation Tier

• Web Tier

• Application Tier

• Naming Services Tier

• Data Tier

In this chapter we will explore the main components of a typical enterprise Services on Demand network architecture and some of the more important underlying issues that impact network architecture design decisions. We describe in detail the Web tier and Application tier, pointing out issues that impact design decisions for availability, performance, manageability, security, and scalability. We then describe some example architectures that were actually deployed in industry. Topics include:

• "Services on Demand Architecture" on page 18 describes the overall architecture from a software perspective, showing the applications that generate the network traffic.

• "Multi-Tier Architecture and Traffic Patterns" on page 20 describes the mapping process from the logical architecture to the physical realization onto the network architecture. It also describes the inter-tier traffic patterns and the reasons behind the network traffic.

• "Web Services Tier" on page 23 describes the most important tier, which is present in all Web-based architectures. This section provides detailed insights into the applications that run on this tier and directly impact the network architecture.

• "Application Services Tier" on page 26 describes the Application tier and the relationship to the Web services tier. This section provides detailed insights into the applications that run on this tier and directly impact the network architecture.

• "Architecture Examples" on page 29 provides examples of various architectures based design trade offs and the reasons behind them. It's important to note that it is the application characteristics that influence the design of the network architecture.

• "Example Solution" on page 34 describes an actual tested and implemented multi-tier architecture, using the design concepts and principles described in this chapter.