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True Number Portability and Advanced Call Screening in a SIP-Based IP Telephony System

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. Overview. Traditional PSTN (public switched telephone network) features

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True Number Portability and Advanced Call Screening in a SIP-Based IP Telephony System

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  1. 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

  2. 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

  3. 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

  4. 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

  5. PBX Features • PBX is usually used within a medium-to-large-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

  6. 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

  7. PBX Features • Executive override • A privileged individual can break into an established call and then the call becomes three-way

  8. 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

  9. 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

  10. 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

  11. 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

  12. 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

  13. SIP Network Structure SIP-based station Registrar server Registration Connected Redirect Server (SIP database) Issuing INTIVE message Proxy server SIP-based station Main SIP Server

  14. 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

  15. 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

  16. The SIP System Architecture SIP database PDA Move to (infrared, wireless) (infrared, wireless) PDA PDA SIP-based Etherphones at every desk, with PDA interface Main SIP server Local Area Network Data network office #2203 Router SIP-based client office #2209

  17. 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

  18. 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 SIP-Etherphone by simply synchronizing one after another

  19. 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 presentations using their PDAs

  20. 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

  21. 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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