| The central-site WAN connection
is a critical focal point for a company. Other sites and users
access this site for information. Because many users access this
site in a variety of ways, it is important that your central-site
solution has a modular design that can accommodate many different
types of WAN connections coming in from remote locations, as shown
in the Figure.
The technologies and features used to connect
company campuses over a WAN are developed to optimize the WAN
bandwidth, minimize the cost, and maximize the effective service to
end users. You should choose the WAN architecture that
provides the most cost-effective bandwidth and a technology that
optimizes service to end users. With that in mind, central-site
considerations include the following:
- Multiple access connections --
Multiple users connect to the central site by using different
media, so central-site considerations must include multiple
media options and simultaneous access from multiple users.
- Cost -- Keep the costs low
while maintaining an adequate level of service. For example,
because some WAN charges are based on usage, such as ISDN, 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 Password
Authentication Protocol (PAP) and Challenge Handshake
Authentication Protocol (CHAP) can identify the remote entity to
prevent unauthorized network connection.
- 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 backing up links
using the same service provider.
- Scalability -- Build a
network that will grow with the business.
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