1.3 Identifying Site Requirements and Solutions
1.3.3 Branch-office considerations
A branch office, commonly referred to as a remote site, uses WAN connections to a central site or to other remote sites. The remote site typically has fewer users than the central site, and so needs a smaller-size WAN connection. 

Because remote-site traffic is typically sporadic, the network designer must determine whether it is more cost-effective to offer a permanent or dialup solution.

Telecommuters may also require access to the remote site through a different media. Therefore, the remote site must have a mix of equipment, but typically not as much as the central site. Typical WAN solutions for remote site to central site connections are:

  • Leased line
  • Frame Relay
  • X.25
  • ISDN
  • XDSL (digital subscriber line) -- This technology enables delivery of high-speed data, voice, and multimedia over conventional telephone wires.

Typical considerations for a remote-site WAN connection follow:

  • Multiple access connections -- Multiple users connect to the central site by using different media. Therefore, branch-office site considerations must include various media options and support for simultaneous access from multiple users.
  • Cost -- Keep the costs low while maintaining an adequate level of service. For example, because some WAN charges, such as ISDN, are based on usage, it is important that companies have a solution that can implement features that will optimize bandwidth and minimize WAN costs. Features such as DDR and compression ensure that WAN costs are kept to a minimum. In another example, because leased lines are generally charged on a fixed basis, you may want to consider this service only if the line can sustain a certain link utilization level.
  • Access control -- Company information must be restricted, allowing users access only to areas in the network that they are authorized to access. For example, access lists can filter out unauthorized data flow between offices and PPP network links, whereas PAP and CHAP can identify the remote entity to prevent unauthorized network connections.
  • Quality of service -- It is important to prioritize traffic over the link and manage traffic flow so that bursty traffic does not slow mission-critical traffic.
  • Redundancy and backup -- Because a link may fail or high link utilization may occur at certain peak usage times during the day, it is important to back up the connection to the central office. Avoid using backup links provided by the same service vendor that provides the primary links.
  • Authentication -- The remote site must be able to authenticate itself to the central site.
  • Availability -- Service providers may not offer certain WAN services in some regions. This consideration generally becomes critical as sites are set up in more remote locations.