In addition to gathering information about the scope of the WAN, the administrator must also determine:
- Should the WAN use a private or public infrastructure? - A private infrastructure offers the best security and confidentiality, whereas the public Internet infrastructure offers the most flexibility and lowest ongoing expense. The choice depends on the purpose of the WAN, the types of traffic it carries, and available operating budget. For example, if the purpose is to provide a nearby branch with high-speed secure services, a private dedicated or switched connection may be best. If the purpose is to connect many remote offices, a public WAN using the Internet may be the best choice. For distributed operations, a combination of options may be the solution.
- For a private WAN, should it be dedicated or switched? - Real-time, high-volume transactions have special requirements that could favor a dedicated line, such as traffic flowing between the data center and the corporate head office. If the enterprise is connecting to a local single branch, a dedicated leased line could be used. However, that option would become very expensive for a WAN connecting multiple offices. In that case, a switched connection might be better.
- For a public WAN, what type of VPN access is required? - If the purpose of the WAN is to connect a remote office, a site-to-site VPN may be the best choice. To connect teleworkers or customers, remote-access VPNs are a better option. If the WAN is serving a mixture of remote offices, teleworkers, and authorized customers, such as a global company with distributed operations, a combination of VPN options may be required.
- Which connection options are available locally? - In some areas, not all WAN connection options are available. In this case, the selection process is simplified, although the resulting WAN may provide less than optimal performance. For example, in a rural or remote area, the only option may be VSAT or cellular access.
- What is the cost of the available connection options? - Depending on the option chosen, the WAN can be a significant ongoing expense. The cost of a particular option must be weighed against how well it meets the other requirements. For example, a dedicated leased line is the most expensive option, but the expense may be justified if it is critical to ensure secure transmission of high volumes of real-time data. For less demanding applications, a less expensive switched or Internet connection option may be more suitable.
Using the guidelines described above, as well as those described by the Cisco Enterprise Architecture, a network administrator should be able to choose an appropriate WAN connection to meet the requirements of different business scenarios.