PBX
to IPT Migration
By
S.K. Tsui
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The PBX (Public Branch Exchange) phone system
that we are currently using is over 18 years old and has already
reached its end-of-life cycle. There is a great potential risk
of system breakdown due to hardware failure which may impact
the majority of the university community. It is therefore necessary
to replace the PBX system as soon as possible.
Voice over IP (VoIP) is a digital technology that
allows voice and video calls to be conducted over a public or
private IP network using a combination of computers and IP phones
at both ends (as opposed to the PBX phone system using analogue
technology to carry voice-only calls over a public or private
telephone network using a combination of telephones and fax
machines at both ends). Through the appropriate digital gateway,
the digital IP telephony (IPT) System is able to communicate
seamlessly with an analogue PBX phone systems over the analogue
telephone network and vice versa.
Based on the VoIP technologies, the IPT system
not only allows voice, data and video to share the same network
cable (hence reducing cabling and support cost), but also offers
many features normally not found or cannot be implemented under
the conventional PBX system such as broadcast or targeted delivery
of digital news in voice, text and/or images. As such, the university
has decided to gradually phase out the existing PBX system and
adopt the IPT technologies in all new buildings and offices.
The CityU IPT System
The CityU IP Phone project started in 2002 by
replacing in Festival Walk Office (FW) 300 phone lines subscribed
from the commercial phone service provider with IP phones and
installing 450 new IP phones in Phase I of the Student Hostel.
In the Fall of 2003, another 140 phones in student rooms of
Jockey Club House and To Yuen Building were upgraded to IP phones.
Since 2004, the coverage of IPT has been gradually extending
to new staff offices, public phones, and Phase II of the Student
Residence. Up to now, we have more than 3200 IP phones installed
in the Student Residence, and 1500 IP phones in Main Campus
and remote offices.
The IPT system is composed of a Cisco Unified
Communications Manager Cluster, a Unity Voice Mail System, Voice
Gateways and IP phone sets inter-connected through Cisco routers
and switches. The IPT core equipments and core network are built
with full redundancy and highest priority is given to voice
traffic to ensure best quality and reliability. The following
picture depicts the architecture of the IPT on the campus network
and its linkage with the existing PBX system :
Features and Advantages of IP Phones
In addition to the basic phone features, one can
enjoy more sophisticated functions and advantages in the IPT system
that are not available in the conventional phone system. Below
lists some of the features and advantages of the IPT.
Features and functions:
- Call forwarding
- Call pickup group
- Call waiting
- Call Transfer
- Caller ID Display
- Conference call
- Configurable Ring Type
- Microphone mute
- Online corporate directory
- Personal phone book
- Speakerphone
- View missed calls
- View placed calls
- View received calls
- Voice mail
Advantages:
- IP Phones can be relocated to anywhere on the network without
reconfiguration
- Share cabling and management cost with the data network
- Telephone number is associated with an IP phone, not a location
- Can push message onto a single, a group, and groups of IP
phones
- Personal phone profile of an IP phone can be exported to and
inherited by other IP phones
- Seamlessly integrate with WiFi and Video IP Phones
- Enhance learning and communication by setting up highly-collaborative
meetings, training sessions, and presentations using voice,
video, or web conferencing provided by the IPT system
- Able to access web information from an IP Phone using keypad
or speech
- Allow simple transactional requests (e.g., request for information)
to be raised through an IP phone using keypad or speech
- Remain reachable by having ubiquitous access to voice, email,
and fax messages from an IP phone or a PC anywhere on the Internet
- Much easier to cater for or meet future phone needs as the
capacity of IPT system is scalable while “add and change” is
easy
Migrating to IPT System
As the IPT has been proven to be reliable and versatile,
CityU is planning to migrate all the existing 4,000 analog devices
in the main campus such as phones, fax, etc. on the PBX to the
IPT in the near future.
The CSC will contact each department individually
for the schedule and details of the migration. It is expected
that the migration will be completed within 1 year.
Impact to Existing PBX Users
The University has acquired the prefix 3442 for
the IPT system. Renumbering is therefore required whenever a PBX
device is migrated to the IPT system. Unless there is a conflict,
all new phone numbers will assume the format of <3442><last
four digits of old phone number>. For example, 2788-7658 will
be changed to 3442-7658.University has acquired the prefix 3442
for the IPT system. Renumbering is therefore required whenever
a PBX phone is replaced by an IP phone. Unless there is a conflict,
all new phone numbers will assume the format of <3442><last
four digits of old phone number>. For example, 2788-7658 will
be changed to 3442-7658.
New Cisco IP phone sets will be provided to users
to replace the old analog phones in the migration. For legacy
devices and machines that must run on PBX system (e.g. fax, personal
alarm system, etc.), specially designed voice gateways are used
to enabling them to run on the IPT system transparently.
To minimize impact on the phone service during migration,
special arrangement in setting up an inter-trunk to link up the
PBX and IPT systems is made. As a result, a user on either phone
system can make call by just dialing the recipient’s 4-digit extension
number regardless of which phone system the recipient’s phone number
actually belongs to. In addition, a 3-month call forward service
or playing an announcement to inform the caller of your new phone
number will be provided by default.
If you want to know more about the migration, please
contact the
CSC Help Desk.
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