Part II: Next Generation - Converged Enterprise Network Architectures
Chapter 2 Enterprise Layer 2 and Layer 3 Design
Chapter 3 Enterprise Campus Architecture Design
Chapter 4 Enterprise Edge Architecture Design
Many businesses today rely on technology to achieve their strategic goals. Therefore, today’s enterprise networks are evolving to be more like a “service delivery” mechanism for different business services and applications, in particular real-time enterprise applications and services, over one converged infrastructure. Traditionally, these services used to be provisioned over a separate physical infrastructure, such as voice and video. In contrast, a converged network logically consolidates these physical networks into one unified physical network with multiple logical networks and allows for optimal connectivity between these various logical networks.
The typical question network designers may ask, “Is there any difference in how converged networks are designed today?”
In fact, this question is one of the key design questions. However, let’s first review the applications that today’s converged enterprise networks are carrying and the requirements and level of criticality of these applications.
It is obvious from the preceding table[6] that most of these applications are critical to the daily business activities. However, these advanced applications and technologies bring aggressive requirements from network performance and resiliency perspectives. Traditionally, the network used to be seen by the business as a cost center. Today’s converged network has been transformed from being seen as a cost center to being seen as a business enabler. As a result, the requirements to design a converged enterprise network are changing, as elucidated upon in the following examples:
Converged critical applications on one shared network (voice, video, and data).
High availability and fast converging. The downtime cost of a converged network is very high compared to a traditional network.
Low latency/low jitter for real-time communication services.
Scalable (hundreds of nodes, global scale).
System virtualization.
Mobility.
Integrated infrastructure security.
Maintenance with minimal impact (ideally zero).
The requirements of a today’s converged enterprise networks are driving the transformation of network design considerations and approaches.
Note
For the purpose of the CCDE exam, you must consider only the business drivers and requirements that are provided to you in each scenario. For example, do not assume cost saving, scalability, or high availability are always required if not mentioned as a requirement, design goal, or possible solution to optimize the design to overcome an existing issue or limitation.
This section discusses the various design principles and aspects of the next-generation converged enterprise network architectures. These network architectures use a modular design approach to divide the network into multiple functional areas that are referred to as modules or blacks (interchangeably). The modularity that is built in to the architecture allows flexibility and scalability in network design and facilitates the future deployment and operation of the network.
There can be different types of functional modules introduced as part of this architecture based on the business needs, size, and industry. This book discusses the most common and vital modules that can be found in almost every large-scale converged enterprise network. These modules are as follows:
Enterprise campus
Enterprise edge (WAN and Internet Blocks)
Enterprise data center (The data center is discussed in Chapter 8, “Data Center Network Design.”)
Chapter 2, “Enterprise Layer 2 and Layer 3 Design,” starts by discussing Layer 2 and Layer 3 network design considerations. It specifically discusses the implications with regard to the different infrastructure topologies that collectively construct the overall Layer 2 and Layer 3 converged enterprise network architecture. The subsequent chapters focus on the design considerations and options of each module of the enterprise network without compromising the holistic design approach. In other words, although each enterprise module is discussed separately, the best design option must always be selected based on both the top-down and holistic approaches. This avoids the designing of the enterprise network modules in isolation and ensures that the design is always driven by the business and application requirements.