Solutions to Chapter 4 - Communication Networks

Communication Networks (2 nd Edition)
Chapter 4 Solutions
Before a connection is made, a recorded message requests the credit card number for the call.
The user inputs the digits and the tones are converted to numbers and the message sent to a
database in the appropriate SCP. The credit card number is verified and may be used to check
for the authorization of funds. The results of the query are sent to the SCP. The appropriate
recorded message is sent back to the user. Based on the query, the call is accepted and a
connection made, or the call is denied.
52. Explain how the intelligent network can provide the following services:
Before a connection is made every call has its signaling information in the control plane routed
through an SCP that stores the destination phone's profile (that is, identifies the services that
have been subscribed).
a. Caller identification – A display on your phone gives the telephone number or name of the
incoming caller.
When the ring signal is sent to the destination phone, if it subscribes to caller ID, then the number
used for routing can also be forwarded, via the signaling network to the receiver phone. The
receiver phone must have the capability to interpret the signal.
b. Call forwarding – Allows you to have calls transferred from one phone to another where you
can be reached.
When the call request reaches the SCP and call forwarding is activated, the database is
referenced to find the forwarding number and the call is rerouted accordingly. Although the call
can be incrementally rerouted from this point, bandwidth may be conserved by rerouting the
connection again from the start to the forwarding number.
c. Call answer – Takes voice mail message if you are on the phone or do not answer the phone.
While the phone is ringing, the number of rings must be counted somewhere in the signaling
network. After a certain number of rings (specified by the user a priori and stored in an SCP
database), if the call is not answered, it is forwarded by a mechanism similar to call forwarding to
a voice mailbox center, which handles the caller accordingly.
In another scenario, when a user is on the phone and a call arrives (assuming no call waiting),
instead of generating a busy signal, the call is forwarded automatically to the voice mailbox.
d. Call waiting – If you are on the phone, a distinctive tone informs that you have an incoming
local or long-distance call. You can place your current call on hold, speak briefly to the
incoming party, and return to the original call.
Generally, if a line is free, a ring is sent to the dialer and receiver. If a line is busy, a busy signal
is sent back to the dialer. If call waiting is activated, a tone from the local switch is sent to the
receiving party (which briefly interrupts the current conversation).
The control plane treats this tone as a ring (that is, it sends a ring back to the dialing party and
voicemail and call forwarding may still be activated). If the user accepts the new call, the current
connection is “held” one hop upstream from the user at the local switch, and a second connection
is made from the dialing party to the user.
At this point, both calls share the line that makes up the last hop to the user. Thus, the user can
only talk to one party at a time. When one of the two connections is being used, the other is
maintained in its incomplete state while the caller is on hold.
Leon-Garcia/Widjaja 25