Cisco Enterprise Edge Network Design Methodology

Reviewing the Enterprise Edge Network Design Methodology

To facilitate the design of effective networks, Cisco Systems has developed a process that allows the network designer has to evaluate and design each module in the network, and determine the effectiveness of the design. The Red Composite business model discussed in Chapter 1, "Introduction to Cisco Network Service Architectures”, allows network designers to design the functional area of the company Edge of modular components that are scalable enough to meet the changing business needs. By implementing a step methodology - step, network designers can create a cutting edge design company that effectively meets your business needs for performance, scalability and availability.

This section identifies functional modules in the Enterprise Edge and lists the criteria to be met and what you need to meet. The step of the methodology - design step for the company Edge presented below, followed by a discussion of traffic analysis within this particular functional area of Composite Network Model Enterprise.

Enterprise Edge Design

The Enterprise Edge functional area is comprised of E-Commerce, Internet Connectivity, Remote Access/Virtual Private Network, and WAN modules, each with its own unique design requirements. As shown in Figure 3-1, each module of the Enterprise Edge functional area connects to the Edge Distribution module of the Enterprise Campus functional area on one side, and it connects to a module of the Service Provider Edge on the other side.

Figure 3-1. Enterprise Edge Functional Area of the Enterprise Composite Network Model

The Enterprise Edge modules perform these functions:

    E-Commerce— Enables enterprises to deploy e-commerce applications and take advantage of the Internet. All e-commerce transactions pass through a series of intelligent services to provide performance, scalability, and availability within the overall e-commerce network design.

    Internet Connectivity— Provides internal users with connectivity to Internet services. Internet users can access the information on publicly available servers. Additionally, this module accepts VPN traffic from remote users and remote sites and forwards it to the Remote Access and VPN module.

    Remote Access and VPN— This module terminates dial-in connections received through the Public Switched Telephone Network (PSTN) and upon successful authentication, it grants dial-in users access to the network. Furthermore, the Remote Access and VPN module terminates VPN traffic forwarded by the Internet Connectivity module from remote users and remote sites, and initiates VPN connections to remote sites through the Internet Connectivity module.

    WAN— Routes traffic between remote sites and the central site using dedicated media or circuits. The WAN module supports any WAN technology, including leased lines, Frame Relay, Asynchronous Transfer Mode (ATM), optical, and cable. The WAN module might also use Integrated Services Digital Network (ISDN) or PSTN dial-on-demand for occasional access and availability.

Typical Requirements for the Enterprise Edge

The features and functionalities of the Enterprise Edge functional area must be identified before its design can commence. The typical, and at the same time, important requirements that the Enterprise Edge functional area must fulfill are

    Functionality— An enterprise network must support the applications and data flows required within the required timeframes. Typical enterprise-wide applications include online transaction processing (OLTP) systems, decision support systems (DSS), e-mail, information sharing, and many other functions. Applications and data might require special peak-time processing, or they might require steady processing throughout a day.

    Performance— Includes three primary metrics: responsiveness, throughput, and utilization. Each Enterprise Edge link and device will be measured in terms of how well it meets all three of the performance metrics.

    Scalability— The Enterprise Edge functional area must provide scalability for future growth in the number of users and in the amount of data and applications that the network might support.

    Availability— Users perceive that the network is down, regardless of where a failure might occur. A typical standard for most enterprise data networks is 99.9% availability.

    Manageability— The Enterprise Edge module must be manageable across the entire infrastructure.

    Cost effectiveness— Cost effectiveness is a key concern for most enterprises, given limited budgets. The network designer's goal is to design the network for maximum efficiency given affordability limitations. Affordability for the Enterprise Edge functional area includes one-time costs for equipment, as well as ongoing tariffs or service charges.

Table 3-1 describes how Enterprise Edge modules meet enterprise needs for functionality, performance, scalability, availability, manageability, and cost effectiveness; and the importance of each component in meeting that need. Each need is ranked in terms of its relative importance, where Critical is highest in relative importance, followed by Important and Normal (no elements in Table 3-1 are marked as Normal). For example, functionality is critical (that is, absolutely required) to the E-Commerce module, while scalability is important (desirable) to the E-Commerce module.

Table 3-1. How the Enterprise Edge Functional Area Modules Fulfill Enterprise Needs

Enterprise Edge Design Methodology

Cisco has developed a step-by-step methodology that you can use to design the Enterprise Edge functional area. The design is based on application Characteristics and involves selecting topology, an Internet service provider (ISP), data-link layer and physical layer technologies, specific Cisco devices, routing protocols, and perhaps special features. This methodology is comprised of eight steps, each of which must be completed in turn:
Step 1.Characterize applications for the Enterprise Edge functional area. The important application characteristics are minimum bandwidth needed, plus delay, jitter, and loss tolerance.

Step 2.Select and diagram the WAN topology. The WAN topology is designed based on the geography and data-sharing requirements.

Step 3.Select an ISP and negotiate price and features. Each ISP will offer different services, rates, and quality guarantees. After you select a service provider, you can complete the remaining steps based on the features available to you.

Step 4.Select a data-link layer WAN, remote access, or Internet technology for each link on the enterprise network. The data-link layer technology selection is based on application requirements and the features a service provider has to offer.

Step 5.Select a physical layer WAN, remote access, or Internet technology for each link on the enterprise network. Based on the data-link layer technology selection and the services offered by the service provider, you can select the physical layer technology.

Step 6.Select specific WAN, remote access, and Internet features for each link on the enterprise network. WAN features are based on application requirements and the features a service provider has to offer.

Step 7.Select specific Cisco network devices and hardware and software options at each location, and create a network topology diagram. Based on the specific requirements at each location, select specific Cisco network devices that meet specified criteria.

Step 8.Select routing protocols and Internet Protocol (IP) addressing for the Enterprise Edge functional area. Similar to the Enterprise Campus functional area, you will select routing protocols and an IP addressing strategy for the Enterprise Edge functional area.

Analyzing Network Traffic Patterns

Assessing and analyzing network traffic patterns typically found in the Enterprise Edge functional area is an important part of network design. The applications that are shared between any two or more sites on the network must be characterized. The gathered information will then be useful to determine the performance, scalability, and requirements for each WAN, remote access, or Internet link. A table that looks similar to Table 3-2 can aid in characterizing the applications at each network campus location. Give special attention to the information that must be recorded in each column.

 

The types of data that applications process, access, and transfer vary in volume and, hence, in bandwidth demands. Table 3-3 shows a sample of typical volumes of various kinds of data that applications process.

The first of the main modules comprising the Enterprise Edge functional area is the WAN module. The effective design methodology and techniques related to this module are discussed next.