Information Technology Reference
In-Depth Information
of failure in the design, either by software features or hardware-based resiliency. Re-
dundancy is critical in providing high levels of availability for the enterprise. Some
technologies have built-in techniques that enable them to be highly available. For
technologies that do not, other techniques can be used, such as using additional
WA N c i r c u i t s o r b a c k u p p o w e r s u p p l i e s .
Support for growth:
Often, enterprises want to provide for growth in their WAN ar-
chitectures, considering the amount of effort and time required to connect additional
sites. High-growth WAN technologies can reduce the amount of effort and cost in-
volved in network expansions. WAN technologies that do not provide growth require
significantly more effort, time, and cost to add new branches or remote offices.
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Operational expenses:
Private line and traditional ATM/Frame Relay tend to have
higher recurring expenses than Internet-based IP VPNs. Public networks such as the
Internet can be used for WAN services to reduce cost, but there are some trade-offs
with reliability and security compared to private or ATM/Frame Relay-type trans-
ports. Moreover, public networks make it more difficult to provide advanced tech-
nologies such as real-time voice and video.
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Operational complexity:
The expertise of the technical staff who are required to
maintain and support MAN and WAN technologies varies. Most enterprises have the
internal IT knowledge to handle most traditional MAN and WAN upgrades without
the need for much training. However, some of the advanced technologies usually re-
served for SPs may require additional training for the IT staff if the support is brought
in-house. Depending on the technology and the design, you have opportunities to re-
duce the complexity through network management.
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Cost to implement:
In most cases, the implementation cost is a major concern. Dur-
ing the design process, it is important to evaluate the initial and recurring costs along
with the design's benefits. Sometimes an organization can migrate from legacy con-
nectivity to new technology with minimal investment in terms of equipment, time,
and resources. In other cases, a network migration can require a low initial cost in
terms of equipment and resources but can provide recurring operational savings and
greater flexibility over the long term.
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Network segmentation support:
Segmentation provides for Layer 2/3 logical sep-
arations between networks instead of physically separate networks. Advantages in-
clude reduced costs associated with equipment, maintenance, and carrier charges. In
addition, separate security polices can be implemented per department or by func-
tional area of the network to restrict access as needed.
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Support for voice and video:
There is an increasing demand for the support of voice
over MAN and WA N technologies. Some WA N providers offer Cisco QoS-Certified
IP VPNs, which can provide the appropriate levels of QoS needed for voice and video
deployments. In cases where Internet or public network connections are used, QoS
cannot always be assured. When voice and video are required for small offices, tele-
workers, or remote agents, 768-kbps upstream bandwidth or greater is recommended.
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