Answers to Chapter 2 Q&A Section 399
5
In routing, what is meant by the term availability?
Availability describes whether a WAN service is offered in a given area and whether it can
be selected for use. For instance, if ISDN is not offered in a location, it is not available,
even though it is a valid choice.
6
In routing, what is meant by the term reliability?
Reliability is the term for how often a WAN service must be available. For instance, do
you require a backup link in the case of a primary link failure? Does DDR suffice for a
particular application? These questions should be asked when evaluating reliability from
a design perspective.
7
Backup is a consideration when looking at which of the following criteria: availability,
reliability, traffic patterns, or QoS?
Backup is a consideration when looking at reliability.
8
What WAN connection method affords the most control for the consumer?
Leased lines offer the most control for the consumer because they never produce a busy
signal. In addition, the only data that travel over the link are the customer's data.
9
Name two important issues in the selection of a product for a SOHO.
Cost and availability are important issues. Cost is always a factor to the smaller office, and
availability dictates what service is possible.
10
What WAN methods offer the least control to the customer?
Asynchronous communications and dialup do not provide a method to circumvent a busy
condition. If the remote location is not answering, the calling location has no way to break
into the location. It is important to remember that the concept of control is not local, but
remote, and the customer will want to control the far end availability. With a leased line,
the consumer owns both ends of the facility and they can't be used for other purposes.
With a dial-up facility, the user can only make a call and hope the other end answers.
11
What product would you select for a central office facility that had to support three to five
branch offices using Frame Relay circuits from 64256 Kbps and that had 2030
occasional dial-up users?
The best choice is the 3600 series router. For instance, the 3640 router with a PRI and a
Mica modem bank would satisfy the occasional dial-up users and enable the Frame Relay
connections.
12
What router would be appropriate for a SOHO user who is using ISDN and who is very
cost-conscious?
The 700 series router would be appropriate.