364 Chapter 11: Selecting Technologies and Devices for Enterprise Networks
For some organizations, scalability is a key design goal. The selected WAN solution must
have enough headroom for growth. As discussed in this chapter, some WAN technologies
are more scalable than others.
Another key design goal for many organizations is to save money on the cost of WAN and
remote-access circuits. Optimization techniques that reduce costs play an important role in
most WAN and remote-access designs. Methods for merging separate voice, video, and
data networks into a combined, cost-effective WAN also play an important role. These
methods must handle the diverse QoS requirements of different applications.
As organizations have become more mobile and geographically dispersed, remote-access
technologies have become an important ingredient of many enterprise network designs.
Enterprises use remote-access technologies to provide network access to telecommuters,
employees in remote ofﬁces, and mobile workers who travel.
An analysis of the location of user communities and their applications should form the basis
of your remote-access design. It is important to recognize the location and number of full-
and part-time telecommuters, the extent that mobile users access the network, and the
location and scope of remote ofﬁces. Remote ofﬁces include branch ofﬁces, sales ofﬁces,
manufacturing sites, warehouses, retail stores, regional banks in the ﬁnancial industry, and
regional doctors’ ofﬁces in the health-care industry. Remote ofﬁces are also sometimes
located at a business partner’s site (for example, a vendor or supplier).
Typically, remote workers use such applications as e-mail, web browsing, sales order-entry,
and calendar applications to schedule meetings. Other, more bandwidth-intensive applica-
tions include downloading software or software updates, exchanging ﬁles with corporate
servers, providing product demonstrations, managing the network from home, videocon-
ferencing, and attending online classes.
Part-time telecommuters and mobile users who access the network less than 2 hours per
day can use an analog modem line. Users who access the network for more than 2 hours
a day need a faster and more convenient technology, however. Analog modems take a long
time to connect and tend to have high latency and low speeds. (The highest speed available
for analog modems today is 56 Kbps.) For customers who have requirements for higher
speeds, lower latency, and faster connection-establishment times, analog modems can be
replaced with small ofﬁce/home ofﬁce (SOHO) routers that support ISDN, a cable modem,
or a DSL modem. The following sections discuss these options and provide information on
PPP, a protocol typically used with remote-access and other WAN technologies.