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MERLIN LEGEND Communications System Release 6.1
Network Reference
555-661-150
Issue 1
August 1998
Call-Handling Scenarios
Page 2-12Networking Guidelines
2
Security 2
This topic summarizes security issues that are discussed in more detail in Chapter
4, “Security.”
Some security issues have been mentioned in the previous topics, including the
reasons that ARS codes are not included in the non-local dial plan. In addition,
keep the following considerations in mind:
■ The ARS access code is permitted only for incoming calls on private
network trunks. It is blocked from incoming PSTN calls.
■ All tandem trunks must be assigned to pools and each pool must contain
the same types of trunks.
■ Users must not be given dial access, Pool button access, or DSS button
access to pools of networked trunks. Instead, they use these facilities via
UDP and/or ARS calling. Routing details are included in the scenarios later
in this chapter.
■ Despite the trunk-to-trunk transfer restriction, a person using any type of
telephone can transfer the following types of calls:
— A call on a tandem trunk transferred to a non-local dial plan extension
— A call on an outside PSTN facility transferred to a non-local dial plan
extension
— A call on a tandem trunk transferred to an outside PSTN line/trunk
However, if an extension is prohibited from making trunk-to-trunk transfers,
the user cannot transfer an outside call on a PSTN trunk to another PSTN
trunk.
SECURITYlALERT:
!
An outside call can arrive at an extension on a private network
system (System A) and be transferred to an extension on another
private network system (System B). The person receiving the transfer
on System B can then transfer the call to a local PSTN trunk despite
any restrictions that are in effect.
NOTE:
PassageWay
®
Telephony Services clients cannot perform transfers
across the private network. Instead, the users must transfer calls
using a telephone. For an example, see “Scenario 5: Large System
Hub” on page 88.
■ Calling restrictions such as Toll and outward restrictions, Allowed/
Disallowed Lists for extensions, and Night Service restrictions are not
applied to UDP calls. Only the extension’s FRL can block completion of
UDP calls.