Converged Networks

Growing Complexibility of Network

Our digital world is changing. The ability to access the Internet and the corporate network is no longer confined to physical offices, geographical locations, or time zones. In today’s globalized workplace, employees can access resources from anywhere in the world and information must be available at any time, and on any device, as shown in Figure 1. These requirements drive the need to build next-generation networks that are secure, reliable, and highly available.

Figure 1.

These next generation networks must not only support current expectations and equipment, but must also be able to integrate legacy platforms. Figure 2 shows some common legacy devices that must often be incorporated into network design. Figure 3 illustrates some of the newer platforms (converged networks) that help to provide access to the network anytime, anywhere, and on any device.

Figure 2.

Figure 3.

Elements of a Converged Networks

To support collaboration, business networks employ converged solutions using voice systems, IP phones, voice gateways, video support, and video conferencing (Figure 1). Including data services, a converged network with collaboration support may include features such as the following:

·    Call control - Telephone call processing, caller ID, call transfer, hold, and conference

·         Voice messaging - Voicemail

·         Mobility - Receive important calls wherever you are

·         Automated attendant - Serve customers faster by routing calls directly to the right department or individual

Figure 1.

One of the primary benefits of transitioning to the converged network is that there is just one physical network to install and manage. This results in substantial savings over the installation and management of separate voice, video, and data networks. Such a converged network solution integrates IT management so that any moves, additions, and changes are completed with an intuitive management interface. A converged network solution also provides PC softphone application support, as well as point-to-point video, so that users can enjoy personal communications with the same ease of administration and use as a voice call.

The convergence of services onto the network has resulted in an evolution in networks from a traditional data transport role, to a super-highway for data, voice, and video communication. This one physical network must be properly designed and implemented to allow the reliable handling of the various types of information that it must carry. A structured design is required to allow management of this complex environment.

Borderless Switched Networks

With the increasing demands of the converged network, the network must be developed with an architectural approach that embeds intelligence, simplifies operations, and is scalable to meet future demands. One of the more recent developments in network design is illustrated by the Cisco Borderless Network architecture illustrated in Figure 1.

Figure 1.

The Cisco Borderless Network is a network architecture that combines several innovations and design considerations to allow organizations to connect anyone, anywhere, anytime, and on any device securely, reliably, and seamlessly. This architecture is designed to address IT and business challenges, such as supporting the converged network and changing work patterns.

The Cisco Borderless Network is built on an infrastructure of scalable and resilient hardware and software. It enables different elements, from access switches to wireless access points to work together and allow users to access resources from any place at any time, providing optimization, scalability, and security to collaboration and virtualization.

Hierarchy in the Borderless Switched Network

Creating a borderless switched network requires that sound network design principles are used to ensure maximum availability, flexibility, security, and manageability. The borderless switched network must deliver on current requirements and future required services and technologies. Borderless switched network design guidelines are built upon the following principles:

·         Hierarchical - Facilitates understanding the role of each device at every tier, simplifies deployment, operation, and management, and reduces fault domains at every tier

·         Modularity - Allows seamless network expansion and integrated service enablement on an on-demand basis

·         Resiliency - Satisfies user expectations for keeping the network always on

·         Flexibility - Allows intelligent traffic load sharing by using all network resources

These are not independent principles. Understanding how each principle fits in the context of the others is critical. Designing a borderless switched network in a hierarchical fashion creates a foundation that allows network designers to overlay security, mobility, and unified communication features. Two time-tested and proven hierarchical design frameworks for campus networks are the three-tier layer and the two-tier layer models, as illustrated in the figure.

The three critical layers within these tiered designs are the access, distribution, and core layers. Each layer can be seen as a well-defined, structured module with specific roles and functions in the campus network. Introducing modularity into the campus hierarchical design further ensures that the campus network remains resilient and flexible enough to provide critical network services. Modularity also helps to allow for growth and changes that occur over time.

Core Distribution Access

Access Layer

The access layer represents the network edge, where traffic enters or exits the campus network. Traditionally, the primary function of an access layer switch is to provide network access to the user. Access layer switches connect to distribution layer switches, which implement network foundation technologies such as routing, quality of service, and security.

To meet network application and end-user demand, the next-generation switching platforms now provide more converged, integrated, and intelligent services to various types of endpoints at the network edge. Building intelligence into access layer switches allows applications to operate on the network more efficiently and securely.

Distribution Layer

The distribution layer interfaces between the access layer and the core layer to provide many important functions, including:

Aggregating large-scale wiring closet networks

Aggregating Layer 2 broadcast domains and Layer 3 routing boundaries

Providing intelligent switching, routing, and network access policy functions to access the rest of the network

Providing high availability through redundant distribution layer switches to the end-user and equal cost paths to the core

Providing differentiated services to various classes of service applications at the edge of network

Core Layer

The core layer is the network backbone. It connects several layers of the campus network. The core layer serves as the aggregator for all of the other campus blocks and ties the campus together with the rest of the network. The primary purpose of the core layer is to provide fault isolation and high-speed backbone connectivity.

Figure 1 shows a three-tier campus network design for organizations where the access, distribution, and core are each separate layers. To build a simplified, scalable, cost-effective, and efficient physical cable layout design, the recommendation is to build an extended-star physical network topology from a centralized building location to all other buildings on the same campus.

Figure 1.

In some cases, because of a lack of physical or network scalability restrictions, maintaining a separate distribution and core layer is not required. In smaller campus locations where there are fewer users accessing the network or in campus sites consisting of a single building, separate core and distribution layers may not be needed. In this scenario, the recommendation is the alternate two-tier campus network design, also known as the collapsed core network design.

Figure 2 shows a two-tier campus network design example for an enterprise campus where the distribution and core layers are collapsed into a single layer.

Figure 2.