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This chapter is from the book

This chapter is from the book

Selecting WAN Services (2.2.4)

Many factors influence the choice of service provider. This topic discusses how the purpose of the WAN, the geographic scope of the WAN, and the traffic requirements all factor in when choosing service providers.

Choosing a WAN Link Connection (2.2.4.1, 2.2.4.2)

There are many important factors to consider when choosing an appropriate WAN connection. For a network administrator to decide which WAN technology best meets the requirements of their specific business, they must answer the following questions:

What Is the Purpose of the WAN?

Considerations include

  • Will the enterprise connect local branches in the same city area, connect remote branches, or connect to a single branch?
  • Will the WAN be used to connect internal employees, or external business partners and customers, or all three?
  • Will the enterprise connect to customers, connect to business partners, connect to employees, or some combination of these?
  • Will the WAN provide authorized users limited or full access to the company intranet?

What Is the Geographic Scope?

Considerations include

  • Is the WAN local, regional, or global?
  • Is the WAN one to one (single branch), one to many branches, or many to many (distributed)?

What Are the Traffic Requirements?

Considerations include

  • What type of traffic must be supported (data only, VoIP, video, large files, streaming files)? This determines the quality and performance requirements.
  • What volume of traffic type (voice, video, or data) must be supported for each destination? This determines the bandwidth capacity required for the WAN connection to the ISP.
  • What quality of service is required? This may limit the choices. If the traffic is highly sensitive to latency and jitter, eliminate any WAN connection options that cannot provide the required quality.
  • What are the security requirements (data integrity, confidentiality, and security)? These are important factors if the traffic is of a highly confidential nature, or if it provides essential services, such as emergency response.

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 here, 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.

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