- Cisco has used the three-level hierarchical network design model for years. This older model (also referred to as the switch block model) provided a high-level idea of how a reliable network could be conceived but was largely conceptual, because it did not provide specific guidance.
- Cisco therefore developed a newer design model-the enterprise composite model-that is significantly more complex.
- This model attempts to address the major shortcomings of the hierarchical model by expanding the older version and making specific recommendations about how and where certain network functions should be implemented.
The enterprise composite model is broken up into three areas :
- Enterprise campus
- Enterprise edge
- Service provider edge
The Enterprise Campus module deals with the campus, defined as one or more buildings on a local area connected with a high speed network. The campus does not provide remote/Internet access. The campus is broken into functional areas, described below.
- Campus backbone (core layer)
- Building distribution
- Building access
- Management
- Server farm (for enterprise services)
The Enterprise Edge module connects the Enterprise Campuses, and other internal resources such as the WAN.
- E-Commerce
- Internet connectivity
- Remote access (dial-up and VPN)
- WAN (internal links)
The Service Provider edge is the demarcation to the Internet and other remote access services.
- Internet service provider (ISP)
- Public Switched Telephone Network (PSTN) for dialup
- Frame Relay, ATM, and PPP for private connectivity
