Networking: A Beginner's Guide
Internet web browsing
FTP and Telnet
Internet or external e-mail
Internet security services
Remote access to the LAN through a VPN or a modem pool
Fax into the LAN (manually distributed or automatically distributed)
Dynamic Host Configuration Protocol (DHCP) services
Centralized virus-protection services
Wide area network (WAN) services to other locations
Streaming Internet radio and other media
Voice over IP (VoIP)
For each service, you must answer a number of questions. First, you need to know
the storage and bandwidth requirements for each service, and any other impacts they
might have. For instance, a fax-in service might itself require a small amount of storage
space, but all the fax bitmaps that users will end up storing could have a large impact
on total storage needs.
Second, you need to know how the service is to be provided. Usually, this means
that you need to know which server will host the service. Some services require such
little overhead that you can easily host them on a server that does other jobs. A DHCP
server, which requires minimal resources, is a good example of such a service. On the
other hand, an e-mail system might require such high resources that you must plan to
host it on its own dedicated server.
Third, you need to know what users or groups of users need which services. This is
because, to minimize backbone traffic, you might need to break down the network into
smaller segments and locate frequently used services for a particular user population
on the same segment as the users use.
Security and Safety
The preceding considerations are all related to the bits and bytes required by different
parts of the network. Security and safety concern the company's need to keep information
secure--both inside and outside an organization--and to keep the company's data safe
from loss. You need to know how important these two issues are before attempting to set
down a network design on paper.
For both these considerations, a trade-off exists between cost and effectiveness. As
mentioned in earlier chapters, no network is ever totally secure and no data is ever totally
safe from loss. However, different companies and departments have different sensitivities
to these issues, indicating that more or less money should be spent on these areas.
Some applications might be perfectly well suited to keeping their data on a striped
RAID 0 array of disks, where the risk of loss is high (relative to other RAID levels),