Download True Number Portability and Advanced Call Screening in a SIP

True Number Portability
and Advanced Call
Screening in a SIP-Based
IP Telephony System
Ismail Dalgic, Michael Borella, Rick Dean,
Jacek Grabiec, Jerry Mahler, Guido Schuster,
and Ikhlag Sidhu 3Com Corporation
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Overview
Traditional PSTN (public switched
telephone network) features


CLASS (custom local area signaling service)
PBX (private branch exchange)
PDA Enhanced IP Telephony
SIP (session initiation protocol), Etherphone
and SIP-EtherPhone
System Integration --- Number Portability
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CLASS Features
Call blocking

The customer may specify one or more
numbers from which he or she does not want to
receive calls
Call trace

Allows a customer to trigger a trace of the
number of the most recent caller
Call return

Returns a call to the most recent caller. If the
most recent caller is busy, the returned call may
be queued until it can be completed
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CLASS Features
Caller ID

The caller’s number is automatically displayed
Caller ID blocking

Allows a caller to block the display of their
number in a callee’s caller ID device
Priority ringing

Different priority numbers have different rings
Call forwarding

A customer may cause calls to their number to
be automatically forwarded to another number
for a period of time
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PBX Features
PBX is usually used within a medium-tolarge-sized business for employee
telephony service
Call transfer

An established call may be transferred form one
number to another on the same PBX
Call forwarding

A PBX number can be programmed to
automatically transfer a call to another number
when the first number doesn’t answer or is busy
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PBX Features
Camp-on queuing

A call to a busy number can be queued, and the
PBX will ring them when the callee answers
Conference calling

Two or more parties can be connected to one
another by dialing into a conference bridge
number
Call parking

An established call at one number can be put on
hold and reestablished from another number
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PBX Features
Executive override

A privileged individual can break into an
established call and then the call becomes
three-way
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PDA Enhanced IP Telephony
True Portable

The PDA follows the user wherever he/she goes
Shifting intelligence from the network to
the telephones
Providing personal and location
information to the network by user’s PDA
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New Application and
Services of PDA
The PDA may act as a smart card,
providing authentication information for
making toll calls
The user may program the system
through the PDA. For example,

During the business hours the default location
to forward calls could be set to be the user’s
office, and during other hours his/her cellular
pager
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New Application and
Services of PDA
Download voicemail and play it back
offline


It will be useful if the user could not spend
much time on the phone
A traveler at an airport may download his/her
30 min worth of voicemail in a few min just
before taking a flight, and may listen to those
message during the flight
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Session Initiation
Protocol (SIP)
SIP is an application-layer control
protocol that can establish, modify and
terminate multimedia sessions or calls
Two major architectural elements

User agent (UA) : resides at SIP end stations
» User agent client (UAC): issuing INVITE request
» User agent server (UAS): accepting the call

Network server: three different types
» Redirect server
» Proxy server
» registrar server
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SIP Network Server
Registrar server

Used to record the SIP address (SIP URL) and
the associated IP address
Redirect server

It processes an INVITE message by sending
back the SIP address where the callee is
reachable
Proxy server


Stateful or stateless
forking or nonforking
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SIP Network Structure
SIP-based
station
Registration
Issuing
INTIVE
message
Registrar server
Redirect
Server (SIP
database)
Proxy server
Connected
SIP-based
station
Main SIP Server
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SIP-Etherphone
Etherphone


An Etherphone is a telephone that can be
plugged into an Ethernet port
Support IP using an IP address that is obtained
by Dynamic Host Configuration Protocol
( DHCP)
» If the location is changed, the IP address automatically
changed
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SIP-Etherphone
Tow major parts of Etherphone

Signaling stack
» Setup phase
» Manage phase
» Tear down phase

Media engine
» Sender: sampling and encoding the voice
» Receiver: performing the reverse operations and manage a
receiver buffer to compensate for network jitter
SIP-Etherphone has a serial port through
which a PDA can be attached
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The SIP System Architecture
SIP-based
Etherphones at
every desk,
with PDA
interface
Main SIP
server
SIP database
Local Area Network
PDA
Data network
office #2203
Move to
Router
(infrared, wireless)
office #2209
SIP-based
client
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PDA
The connection of SIP
network and PSTN
PSTN/SIP gateway


The gateway provides a connection between the
LAN and the PSTN
The gateway acts as a SIP UA on behalf of the
PSTN phones.
SIP-based LAN
Regular PSTN phone
Gateway
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True number portability
A caller can reach a particular person
rather than a particular phone
A person authenticates himself to the
SIP-Etherphone by synchronization their
PDA with the SIP-Etherphone
Multiple users can register with one SIPEtherphone by simply synchronizing one
after another
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Conclusions
Advantages



Shoppers can make purchases at a store simply
by tapping a few buttons on their PDAs, and
the money would be transferred from the PDA
to the merchant
Shoppers can also instantaneously receive
detailed information on location about the
products at the store
Presenters can remotely control computer
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presentations using their PDAs
Conclusions
Advanced call screening



Making use of the address book and date book
of the PDA to allow the assignment of priorities
for meetings and addresses
Blocking unwanted calls
Defining the particular behavior for particular
callers
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Conclusions
Such new applications will bring
great value by allowing mobile
users to save time and money.
Furthermore, users are to be more
connected at any location and avoid
unnecessary disturbance.
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