40 Chapter 1: Design Overview
3
What performance and application requirements need to be obtained from WSOL?
·
Name of application
·
Type of application
·
Number of users
·
Protocol requirements
·
Approximate bandwidth requirements
4
What network management issues need to be addressed?
·
Identifying potential bottlenecks
5
What security concerns need to be addressed?
·
Technology weaknesses
·
Configuration weaknesses
·
Security policy weaknesses
Answers to Scenario 2
1
Is the full-mesh solution the best one for WSOL?
No. The disadvantage of the full-mesh topology centers on one primary issue: There are
too many physical links. If the routers are far apart, the link costs can quickly become
prohibitively expensive, because adding routers creates an exponential increase in the
number of links required.
Under a full-mesh solution, the number of permanent virtual circuits (PVCs) equals
[n (n1)]/2. If n = 7, the number of PVCs would equal 21 connections. With 21 PVCs, the
routers will not have enough ports to support this topology.
This number of connections would not be cost-effective for WSOL. In addition, routers
currently available would have density available for 21 port connections. Although this
full mesh provides a great deal of redundancy, it might prove prohibitively expensive to
implement.
2
What solution might work better?
A partial-mesh solution would be more effective for WSOL. A partial-mesh solution (see
Figure 1-16) could allow New York and Manhattan to operate in a full-mesh topology,
while the other station routes can be connected as a partial mesh. Providing complete
redundancy for WSOL could represent a stranded investment for WSOL's capital
investors. A partial mesh will provide enough redundancy to satisfy WSOL's business
87200333.book Page 40 Wednesday, August 22, 2001 2:18 PM