Formiddagsseminar12. april 2002-Transparenter


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Formiddagsseminar12. april 2002-Transparenter

  1. 1. Voice Services over an IP Network By Dr. James G. Williams
  2. 2. 4 Basic Technologies for VoIP <ul><li>Signaling - Call Setup </li></ul><ul><li>Encoding - A/D and Quantising </li></ul><ul><li>Transport - Transmission and Switching/Routing </li></ul><ul><li>Gateway Control - Media Device Control </li></ul><ul><ul><li>Application Software </li></ul></ul><ul><ul><li>Session Software </li></ul></ul>
  3. 3. Standards <ul><li>Signaling - H.323 (ITU) AND SIP (IETF) </li></ul><ul><li>Encoding - G.711 PCM (64000 kbps), G.722 (ADPCM), G.726, G.727, etc. </li></ul><ul><li>Transport - RTP (Real-Time Transport Protocol = transport voice samples), RTCP (Real-Time Transport Control Protocol = feedback on Quality), RTSP (Real-Time Streaming Protocol) </li></ul><ul><li>Gateway Control - MGCP (Media Gateway Control Protocol), H.GCP, IPDC </li></ul>
  4. 4. 2 Major Scenarios <ul><li>Private Network, No PSTN but with or without Internet </li></ul><ul><li>Private Network with PSTN </li></ul>
  5. 5. Basic Components for VoIP H.232 Terminal (Telephone or PC) H.323 Gateway e.g. Cisco 3600 Private Network H.323 Gateway e.g. Cisco 3600 H.232 Terminal (Telephone or PC) Internet
  6. 6. Call Processing <ul><li>Caller goes off hook-detected by gateway application </li></ul><ul><li>Session issues dial tone </li></ul><ul><li>Session waits for dialed digits </li></ul><ul><li>Session matches dial plan pattern </li></ul><ul><li>Session maps called number to an IP host to route to destination (may be itself) </li></ul><ul><li>Session runs the H.323 protocol to establish a transmission and reception channel over the IP network </li></ul><ul><li>If RSVP used, RSVP reservations are attempted to achieve QoS </li></ul>
  7. 7. Call Processing <ul><li>The CODECS (Coders and Decoders) are activated with parameters (Samples analog voices converts to digital - G.711 samples 8000 times per second and produces 8000 8 bit bytes = 64000 bits) </li></ul><ul><li>If duration of voice in a packet is 20ms, then 50 (1280 bit) payload packets per second </li></ul><ul><li>Protocol stack is RTP - UDP - IP </li></ul>
  8. 8. Call Processing <ul><li>Any Call Progress indicators are cut through the voice path as soon as audio channel established </li></ul><ul><li>Signaling detected by voice ports after call setup are trapped by session layer and carried over the IP network by RTCP </li></ul><ul><li>When either end hangs up, connection is torn down (any RSVP resources) </li></ul>
  9. 9. The Business Plan <ul><li>What Offerings (services, products)? </li></ul><ul><li>Who are the customers? </li></ul><ul><li>Who is the competition? </li></ul><ul><li>How will the services be delivered? </li></ul><ul><li>What technologies can be utilized? </li></ul><ul><li>What is the cost of delivering service? </li></ul><ul><li>What resources are required to deliver and support the services? </li></ul>
  10. 10. The Business Plan <ul><li>What system architecture is required? </li></ul><ul><li>What processes, functions, procedures, etc. are needed? </li></ul><ul><li>What are the capacities and volumes of the resources needed? </li></ul><ul><li>What Financial Resources are Needed? </li></ul><ul><li>The Economic Model </li></ul>
  11. 11. Company Background <ul><li>Competitive Local Exchange Carrier (CLEC)/(Telephone Company) </li></ul><ul><li>3 Venture Capitalists - $62 Million </li></ul><ul><li>1 Finance Company - $ 120 Million </li></ul><ul><li>16 markets (cities) East Coast USA </li></ul><ul><li>8 Founders </li></ul><ul><li>Estimated 400 employees </li></ul>
  12. 12. Company Background <ul><li>New Generation Network </li></ul><ul><ul><li>Broadband Services to Businesses </li></ul></ul><ul><ul><ul><li>Small to Medium (6 – 50 employees) </li></ul></ul></ul><ul><ul><ul><li>Underserved Markets </li></ul></ul></ul><ul><ul><li>DSL to the Premise (VoIP) </li></ul></ul><ul><ul><li>ATM backbone (VoATM) </li></ul></ul><ul><ul><li>All Digital Packet Switched Network to the PSTN </li></ul></ul><ul><ul><li>Offices in each city fully staffed </li></ul></ul><ul><ul><ul><li>Sales (15), Customer Care(3), Technicians(3) </li></ul></ul></ul>
  13. 13. Technology Architecture LSO with a 720 Port DSLAM (Digital Subscriber Line Access Multiplexer) 4 – 16 port IAD at Customer Premise Local Loop ILEC Central Office Telephone Fax PC/ Hub/ Router 45 – 155 Mbps PSAX ATM Router ATM Digital Switch Pathstar/5-ESS Springtide Router 1Central Office per market Internet PSTN 911 Center Voice Data GR303 LSO ILEC Central Office NOC Network Alarms and SNMP Packets Other Market PSAX NOC Data
  14. 14. Services <ul><li>Voice Services </li></ul><ul><ul><li>Local </li></ul></ul><ul><ul><li>Long Distance </li></ul></ul><ul><ul><li>Voice Mail </li></ul></ul><ul><ul><li>Features (Call Forward, Caller ID, etc.) </li></ul></ul><ul><ul><li>PBX and Keyset Support </li></ul></ul><ul><ul><li>Calling Cards </li></ul></ul><ul><li>Data Services </li></ul><ul><ul><li>Internet Access (386 kbps to 2.3 mbps) </li></ul></ul><ul><ul><li>VPN </li></ul></ul><ul><ul><li>Email Web Hosting </li></ul></ul>
  15. 15. Voice Requirements <ul><li>7X24 service availability </li></ul><ul><ul><li>IAD must have UPS </li></ul></ul><ul><ul><li>DSLAM must have UPS </li></ul></ul><ul><ul><li>PSAX must have UPS </li></ul></ul><ul><ul><li>Switch 7RE (5ESS) must have UPS </li></ul></ul><ul><ul><li>Need fault tolerant devices </li></ul></ul><ul><li>Network Operations Center (NOC) </li></ul><ul><ul><li>Access to every component via IP network </li></ul></ul><ul><ul><li>Uses SNMP (Simple Network Management Protocol) to configure and reconfigure devices via the MIB (Management Information Base) </li></ul></ul><ul><ul><li>Receives Alarm messages from devices based on threshold settings for triggers </li></ul></ul><ul><ul><li>Ability to test circuits (Lucent’s LoopCare) </li></ul></ul>
  16. 16. Voice Requirements <ul><li>Quality of Service (QoS) </li></ul><ul><ul><li>Latency is critical for voice, not data </li></ul></ul><ul><ul><li>Local loop bandwidth considerations </li></ul></ul><ul><ul><ul><li>Voice without compression requires 128Kb (64Kb for each direction) </li></ul></ul></ul><ul><ul><ul><li>Maximum bandwidth is determined by length of loop from LSO (SDSL = 18,000 ft. Max) and quality of the loop </li></ul></ul></ul><ul><ul><ul><li>No load coils and bridged taps permitted </li></ul></ul></ul><ul><li>Reliability </li></ul><ul><ul><li>Dial Tone always there </li></ul></ul><ul><ul><li>Same actions, same results </li></ul></ul>
  17. 17. Customer Path IAD ILEC Circuit (IDs, Vendor) IP Addresses, Voice VPI/VCI, Data VPI/VCI, Telephone Numbers, Host IP Addresses Host PC Telephone Stinger-DSLAM Shelf, Slot, Port, Voice VPI/VCI, Data VPI/VCI IOF Circuit Terminations, IDs, Type, Channels LSO Facility Customer Premise PSAX Slot, Port, Voice VPI/VCI, Data VPI/VCI Pathstar Port Voice VPI/VCI IP Addresses Springtide Port IP Address 3-COM ID Mail Accounts Central Office
  18. 18. Other Players <ul><li>ILEC (Incumbent Local Exchange Carrier) </li></ul><ul><ul><li>Own local loops </li></ul></ul><ul><ul><li>Own Telephone Numbers </li></ul></ul><ul><ul><li>Own the Customer </li></ul></ul><ul><li>IXC – Inter-exchange Carriers (Long Distance) </li></ul><ul><li>911 – Emergency Management Interface </li></ul><ul><li>CMDS (national database) </li></ul><ul><li>Caller ID (LIDB – national database) </li></ul><ul><li>Ported Numbers (national database) </li></ul><ul><li>800 Numbers (national database) </li></ul>
  19. 19. CLEC TO BA LOCAL Call Direction CLEC EO BA EO <ul><li>Usage Billing Concept </li></ul><ul><li>Reciprocal Compensation </li></ul><ul><li>BA Bills CLEC - Usage </li></ul><ul><li>Local charges for MOUs </li></ul><ul><li>TANDEM </li></ul><ul><ul><li>or </li></ul></ul><ul><ul><li>END OFFICE </li></ul></ul><ul><li>Factors Exchange </li></ul><ul><li>Required </li></ul><ul><li>CLEC to BA </li></ul><ul><li>PLU Factor </li></ul>Record Exchange Required NONE LOCAL/TOLL TRUNKS or <ul><li>BA Bills CLEC - Facilities </li></ul><ul><li>Tandem Switched Transport (TST) </li></ul><ul><li>Entrance Facility or Cross Connect </li></ul><ul><li>Direct Trunked Transport (DT) </li></ul><ul><li>Entrance Facility or Cross Connect </li></ul><ul><li>Channel Milage (EO to EO) </li></ul>TST DT
  20. 20. CLEC TO BA INTRALATA TOLL Call Direction CLEC EO BA EO <ul><li>Usage Billing Concept </li></ul><ul><li>Switched Access </li></ul><ul><li>BA Bills CLEC - Usage </li></ul><ul><li>Tandem Connection </li></ul><ul><li>Local Switching </li></ul><ul><li>Tandem Switching </li></ul><ul><li>Tandem Transport </li></ul><ul><ul><li>Fixed </li></ul></ul><ul><ul><li>Per Mile </li></ul></ul><ul><li>RIC </li></ul><ul><li>CCL </li></ul><ul><li>End Office Connection </li></ul><ul><li>Local Switching </li></ul><ul><li>RIC </li></ul><ul><li>CCL </li></ul><ul><li>Factors Exchange </li></ul><ul><li>Required </li></ul><ul><li>CLEC to BA </li></ul><ul><li>PLU Factor </li></ul>Record Exchange Required NONE or LOCAL/TOLL TRUNKS TST DT <ul><li>BA Bills CLEC - Facilities </li></ul><ul><li>Tandem Switched Transport (TST) </li></ul><ul><li>Entrance Facility or Cross Connect </li></ul><ul><li>Direct Trunked Transport (DT) </li></ul><ul><li>Entrance Facility or Cross Connect </li></ul><ul><li>Channel Milage (EO to EO) </li></ul>
  21. 21. BA TO CLEC LOCAL Call Direction CLEC EO BA EO <ul><li>Usage Billing Concept </li></ul><ul><li>Reciprocal Compensation </li></ul><ul><li>CLEC Bills BA - Usage </li></ul><ul><li>Local Termination charges </li></ul><ul><li>for MOUs in accordance with </li></ul><ul><li>CLEC tariff/agreement. </li></ul><ul><li>Factors Exchange </li></ul><ul><li>Required </li></ul><ul><li>BA TO CLEC </li></ul><ul><li>PLU Factor </li></ul>Record Exchange Required NONE or LOCAL/TOLL TRUNKS TST DT <ul><li>CLEC Bills BA - Facilities </li></ul><ul><li>Tandem Switched Transport (TST) </li></ul><ul><li>Entrance Facility </li></ul><ul><li>Direct Trunked Transport (DT) </li></ul><ul><li>Entrance Facility </li></ul>
  22. 22. BA TO CLEC INTRALATA TOLL Call Direction CLEC EO BA EO <ul><li>Usage Billing Concept </li></ul><ul><li>Switched Access </li></ul><ul><li>CLEC Bills BA - Usage </li></ul><ul><li>Switched Access Charges </li></ul><ul><li>for MOUs in accordance </li></ul><ul><li>with CLEC Tariff/Agreement. </li></ul><ul><li>Factors Exchange </li></ul><ul><li>Required </li></ul><ul><li>BA to CLEC </li></ul><ul><li>PLU Factor </li></ul>Record Exchange Required NONE or TST LOCAL/TOLL TRUNKS DT <ul><li>CLEC Bills BA - Facilities </li></ul><ul><li>Tandem Switched Transport (TST) </li></ul><ul><li>Entrance Facility </li></ul><ul><li>Direct Trunked Transport (DT) </li></ul><ul><li>Entrance Facility </li></ul>
  23. 23. CLEC TO AN IXC Call Direction CLEC EO <ul><li>Usage Billing Concept </li></ul><ul><li>Switched Access </li></ul><ul><li>Meet Point Billing </li></ul><ul><li>Multiple Bill/Multiple Tariff </li></ul><ul><li>BA Bills IXC - Usage </li></ul><ul><li>Tandem Switching </li></ul><ul><li>Portion of Transport </li></ul><ul><li>CLEC Bills IXC - Usage </li></ul><ul><li>Switched Access Charges </li></ul><ul><li>for MOUs in accordance </li></ul><ul><li>with CLEC tariff/agreement. </li></ul><ul><li>CLEC Bills BA - Usage </li></ul><ul><li>Not Applicable </li></ul>Factors Exchange Required IXC to CLEC - FGD Factors <ul><li>Record Exchange </li></ul><ul><li>Required </li></ul><ul><li>CLEC makes originating </li></ul><ul><li>record </li></ul><ul><li>CLEC to BA </li></ul><ul><li>EMR 115002 </li></ul>IXC SUBTENDING OZZ/CIC FGD/B <ul><li>BA Bills CLEC - Facilities </li></ul><ul><li>Tandem Switched Transport (TST) </li></ul><ul><li>Entrance Facility or Cross Connect </li></ul>
  24. 24. IXC TO A CLEC Call Direction CLEC EO Factors Exchange Required IXC to CLEC - FGD Factors <ul><li>Usage Billing Concept </li></ul><ul><li>Switched Access </li></ul><ul><li>Meet Point Billing </li></ul><ul><li>Multiple Bill/Multiple Tariff </li></ul><ul><li>BA Bills IXC - Usage </li></ul><ul><li>Tandem Switching </li></ul><ul><li>Portion of Transport </li></ul><ul><li>CLEC Bills IXC - Usage </li></ul><ul><li>Switched Access Charges </li></ul><ul><li>for MOUs in accordance with </li></ul><ul><li>CLEC tariff/agreement. </li></ul><ul><li>CLEC Bills BA - Usage </li></ul><ul><li>Not Applicable </li></ul><ul><li>Record Exchange </li></ul><ul><li>Required </li></ul><ul><li>BA to CLEC </li></ul><ul><li>EMR 110101 </li></ul><ul><li>CLEC to BA </li></ul><ul><li>EMR 115002 </li></ul>FGD/B IXC SUBTENDING OZZ/CIC <ul><li>BA Bills CLEC - Facilities </li></ul><ul><li>Tandem Switched Transport (TST) </li></ul><ul><li>Entrance Facility or Cross Connect </li></ul>
  25. 25. CLEC TO CLEC LOCAL Call Direction CLEC EO CLEC EO Factors Exchange Required Record Exchange Required 11-01-01 to NYSP NYSP bills Originiating CLEC for Transit Service Charges <ul><li>BA Bills Originating CLEC - Usage </li></ul><ul><li>Transit Service Charges </li></ul><ul><li>Recovery of Local Termination charges </li></ul><ul><li>for MOUs paid by BA to Terminating CLEC. </li></ul><ul><li>Terminating CLEC Bills BA - Usage </li></ul><ul><li>Local Termination charges </li></ul><ul><li>for MOUs in accordance with </li></ul><ul><li>Terminating CLEC tariff/agreement </li></ul><ul><li>Usage Billing Concept </li></ul><ul><li>Transit Service </li></ul>LOCAL/TOLL TRUNKS (Originating) (Terminating)
  26. 26. CLEC TO ITC LOCAL/INTRALATA Call Direction ITC EO CLEC EO Factors Exchange Required NONE <ul><li>Record Exchange </li></ul><ul><li>Required </li></ul><ul><li>BA to ITC </li></ul><ul><li>- 110101 </li></ul><ul><li>ITC to BA </li></ul><ul><li>- 115002 </li></ul>LOCAL/TOLL TRUNKS ITC subtends a BA Access Tandem FGC-LIKE TRUNKS MP <ul><li>Usage Billing Concept </li></ul><ul><li>Transit Service </li></ul><ul><li>Meet Point Billing </li></ul><ul><li>BA Bills CLEC - Usage </li></ul><ul><li>Tandem Switching </li></ul><ul><li>Tandem Transport </li></ul><ul><li>- Fixed </li></ul><ul><li>- Per mile from SWC to MP </li></ul><ul><li>Independent Bills CLEC - Usage </li></ul><ul><li>Charges for MOUs in accordance </li></ul><ul><li>with tariff/agreement. </li></ul>CLEC and Independent must have billing agreement.
  27. 27. CLEC TO ITC LOCAL/INTRALATA TOLL Call Direction ITC EO CLEC EO <ul><li>Usage Billing Concept </li></ul><ul><li>Special Access </li></ul><ul><li>BA Bills CLEC - Usage </li></ul><ul><li>Channel Termination </li></ul><ul><li>Channel Mileage </li></ul><ul><li>- Fixed </li></ul><ul><li>- Per mile from SWC to MP </li></ul><ul><li>ITC Bills CLEC - Usage </li></ul><ul><li>Charges for MOUs in </li></ul><ul><li>accordance with CLEC </li></ul><ul><li>tariff/agreement. </li></ul>Factors Exchange Required NONE Record Exchange Required NONE MP Direct Trunk - ITC and CLEC could utilize 2-way. CLEC and Independent must have billing agreement.
  28. 28. Internet, Intranet, Extranet Pre-Sale System (BroadStreet) Order Management System (Arbor/OM) Provisioning (Dset, BA) Billing ( Arbor / BP ) Financial Accounting System Payroll (Payroll One) Human Resource System (Employease ) Web Site E911, PIC/CARE Number Portability Other Interfaces (Arbor/BP) Customer Care (Arbor/BP) Help Desk Trouble Ticket (Remedy) System Components
  29. 29. Arbor/BP Customer Care Customer Inquiry Customer Account Maintenance Pre-Sale System Analysis Prospects, LSOs, Employees, Inventory, Maps, Regulatory, Competition, etc. Financial Accounting System GL, AR, AP, Assets, Purchasing, etc. ILEC, IXC Revenue and Payments Services Rates Discounts Formats Arbor//BP Billing Payroll Human Resources Sales System Order Data Arbor/OM Installation Configuration Provision E-Bonding ILECs, CLECS, IXCs Contract, Letter Notifications Customer, Sales Customer Usage ILEC, IXC BillDats Software Databases Customer Intelligence Commissions Network Monitoring Fault Management Arbor/OM Remedy Trouble Ticket Maintenance Tools LoopCare Charges, Inventory, Times Back Office System Flow 03/16/2000
  30. 30. SUN SOLARIS O.S. OM Arbor/BP BillDats Sybase DB Presale & Sales ILEC Provisioning ILEC & Quintessent Network Fault Management (NFM) HPUX O.S. LoopCare Windows 2000 O.S. Remedy Help Desk Remedy Trouble Ticketing Financial & Asset Management Web Server (IIS) Mail Server (Exchange) Trading Partners System Interface (EDI, CORBA) Desktop Applications Gis System BroadStreet Employees BroadStreet Customers Public Validation Quintessent Oracle DBMS Informix DBMS Oracle DBMS Web Server iPlanet DSL line Qualification BackOffice Software Architecture Software Architecture SQLServer
  31. 31. BackOffice Support Architecture Windows 2000 Servers Web Server Mail Server Remedy Help Desk Financials Desk Top Apps E911 Internet Intranet Extranet Arbor/OM and Arbor/BP Servers Ordering and Provisioning Data Capture Gateway Server Oracle DBMS Customer Care Order Entry Product Configuration ILEC/LSR PIC/Care Pre-Order Journals Payments Invoicing NOC and Provisioning Servers Oracle DBMS NFM LoopCare Navis Remedy Trouble Ticket Cajun View Remote Network Devices LNP LIDB Sprint Mgt 911 Service Requests Mediation Servers ILECs Verizon, Etc. 5ESS Switches MSAG Data Updates Inventory IPs, Tele No. IADs, Stinger Circuits Sprint LD 3COM Messaging CMDS SQL Server DBMS DBMS
  32. 32. Provisioning Support Order Management Order Queue Provisioning Interface For Stinger,PSAX and Switch Stinger Table Data –w- Pre-configured Path Data Update PSAX Table Update Circuits Table Update Switch Table Update 3-COM Table Update Calling Cards Provisioning Interface for The IAD Update IAD Table Database
  33. 33. Intranet/Extranet VoIP <ul><li>Voice/IP is not expensive, but the initial outlay will depend largely on where and to what extent the technology is deployed. </li></ul><ul><li>Some sites only want voice/IP for local telephony with all externals calls still going over the public switched telephone network (PSTN) or over a private voice network. </li></ul><ul><li>But more commonly, voice/IP is deployed externally with the existing on-site telephone infrastructure left intact. In this case, a gateway is needed to route a call over a wide area IP network. </li></ul>
  34. 34. Voice Over IP <ul><li>A major technical question is where and how best to deploy the gateway function. This will depend on factors such as the size of the site, number of sites, location of sites, etc. </li></ul><ul><li>While there are serious questions over voice/IP reliability and quality, analyst Gartner Group predicts that these are likely to fade this year. </li></ul>
  35. 35. Voice over IP <ul><li>At present, the quality of voice/IP almost never exceeds the PSTN and suffers from variability, even over private IP networks. </li></ul><ul><li>Technology and standards to provide an end-to-end connection and offer guaranteed bandwidth without interference from other network traffic are only just coming into place. </li></ul>
  36. 36. Voice over IP <ul><li>Voice/IP is being more widely deployed over private IP-based intranets </li></ul><ul><li>Can save money by routing conventional calls from existing phones over the IP backbone. </li></ul><ul><li>When virtual private networks are used to carry IP-based voice - the quality is similar to GSM cellular, but may not be deemed reliable enough for talking to customers. </li></ul>
  37. 37. Voice Over IP <ul><li>London-based marketing agency Rainier implemented voice/IP for toll bypass using its virtual private IP network for calls between its London office and offices in Boston and San Francisco. </li></ul><ul><li>Voice/IP has cut Rainier's transatlantic voice communications bill by 75% compared with BT's rates. </li></ul><ul><li>The delay, about 15 to 30 seconds, is the time it takes to set up the fixed path through the end-to-end network, including the component provided by the ISP. </li></ul>
  38. 38. Voice Over IP <ul><li>One problem with using intranets or virtual private networks to carry voice is that it can become unacceptable during peak periods. </li></ul><ul><li>The ideal solution would be to route calls over the PSTN at such times, if only you could tell in advance that the quality of service available over the IP network was inadequate. </li></ul><ul><li>Networking and telecoms systems vendor Nortel Networks has developed a technique for monitoring the condition of an IP network for this situation. </li></ul><ul><li>A company's Meridian private branch exchanges (PBXs) can assess the likely quality of the IP network on an ongoing basis by transmitting test packets and measuring the transit delays. </li></ul><ul><li>While this delay is kept within acceptable bounds, the network is deemed acceptable for voice/IP. But if the delay falls outside the bounds, calls are re-routed over the PSTN. </li></ul>
  39. 39. Voice Over IP <ul><li>VoIP has the potential to deliver new applications and features not so easy to support over the PSTN. </li></ul><ul><li>Web-enabled call centres, where voice/IP will enable voice calls to be opened up within an existing Internet session. </li></ul><ul><li>Currently, some sites have 'call me' buttons, but the call-backs run on a separate line over the PSTN which is not useful if only one line exists and is already busy during an Internet session. </li></ul><ul><li>Voice/IP will also enrich existing telephony by making sophisticated call-handling features more readily accessible. </li></ul><ul><li>Modern PBXs have for years come with a huge sophistication of features which are largely inaccessible because the LCD display on handsets is not a useful interface </li></ul>
  40. 40. Voice Over IP <ul><li>Service providers may offer caller identification as a feature </li></ul><ul><li>IP signaling, perhaps combined with caller identification, can also be used to facilitate sophisticated call conferencing of the kind previously only available as a specialist service. </li></ul><ul><li>Larger conferences usually require a mediator to control admissions to the conference and introduce new participants to the others. </li></ul><ul><li>The use of IP signaling combined with the PC interface makes it easy to perform these functions. </li></ul>
  41. 41. VoIP Applications <ul><li>On-site IP telephony allowing internal calls to be made over IP-based Lans. </li></ul><ul><li>Corporate toll bypass where voice calls are made over internal IP networks or virtual private IP networks. </li></ul><ul><li>Voice over the Net between two multimedia-equipped PCs. </li></ul><ul><li>Fax over the Net. The cost is very cheap, and quality is less of an issue because communication is not real time and loss of bandwidth simply delays transmission </li></ul><ul><li>IP-based public phone services. Carriers can cut costs by consolidating voice and data over single IP core networks and can deliver new features not possible over the PSTN such as advanced conferencing </li></ul><ul><li>Call-centre IP telephony. This is a variant of voice/IP, but is a distinct application </li></ul><ul><li>Voice messaging over the Internet. The Net can become a medium for unified messaging. </li></ul><ul><li>Video-over-IP. This field unto itself is raising a variety of unique technical issues. </li></ul>
  42. 42. Voice Over IP Gateways
  43. 43. VoIP Gateways Increase in Functionality
  44. 44. Softswitch
  45. 45. SoftSwitch
  46. 47. VoIP Quality <ul><li>Bandwidth and transit delay affect voice quality during transmission over any communications link. </li></ul><ul><li>Circuit-switched voice and cellular GSM, the voice is sampled and converted into bits at the rate of 64Kbps. Each sample represents an approximation of the sound during its sampling period, in this case, 1/8000 of a second. </li></ul><ul><li>On the PSTN, an end-to-end path is set up, and this imposes a slight delay which is barely noticeable except over satellite links. This delay is very consistent and has no effect on quality. As the bandwidth is fixed, quality does not vary during the conversation. </li></ul><ul><li>With voice/IP , the digital bits obtained from the sampling process are first packed into IP packets before being transmitted, and this imposes a slight up-front delay. But this is not an issue unless the voice is packed and then unpacked into bit streams during transmissions. </li></ul>
  47. 48. VoIP Quality <ul><li>IP networks do not normally provide a fixed end-to-end path for a whole session nor a guaranteed bandwidth. </li></ul><ul><li>This is mitigated by stamping the packets with the time they were sent and using buffers to hold them for a second or so at the receiving end, so that they can be assembled in the right order and with the right timing. </li></ul><ul><li>But the delay can only be minimal or else the packet will be too late to be of any use. Even when there are no serious delays and IP packets have a fixed path, bandwidth can be reduced when there is a surge in traffic leading to degraded quality. </li></ul><ul><li>Instead, everything slows down, and some packets have to be discarded to ensure that at least a reduced number can arrive on time. The result is that there are fewer bits to represent the sound at the receiving end and quality degrades. </li></ul><ul><li>The only way to solve these problems is to set up fixed paths through the network for the duration of a conversation and allocate a fixed amount of bandwidth to it. You create a tunnel through the network shielded from other traffic. </li></ul><ul><li>This reduces the efficiency of the IP network because this tunnel is then reserved purely for the voice and cannot be re-allocated to other traffic even during periods of silence, until the parties hang up. </li></ul>
  48. 49. VoIP Security <ul><li>Security - a high priority for and company or university who relies on its computer networks for quick access to private or sensitive materials. </li></ul><ul><ul><li>Currently encryption and authentication of user access is only a recommendation by H.323. What this means is that any H.323 aware user can tap into any conversation on the system. And an employee or any outside person can monitor every conversation with access without ever having to leave his or her desk. </li></ul></ul><ul><li>Another security issue arises if a corporation uses VoIP technology for a remote access location. </li></ul><ul><ul><li>This is one of the main uses for partial VoIP implementation today, but it is also a serious security risk because of problems with firewalls. Currently H.323’s firewall negotiation mechanisms require direct access into the corporate network. A blatant violation of most corporations’ security requirements is the call-set up of H.323. </li></ul></ul>
  49. 50. Making VoIP Work <ul><li>Making Voice over IP function efficiently in a corporate enterprise network requires adequate bandwidth allocation and management. </li></ul><ul><ul><li>For each call to be sent across an IP network, 17Kbps is needed of the total bandwidth. If properly designed and operated a company’s network can use a 56 or 64 KBPS link to simultaneously share several voice calls and data traffic without any delays or problems. </li></ul></ul><ul><li>Whereas when using the Internet, Providers such as America on Line (AOL) handle too much Internet traffic and rout transmissions too many times to provide a clear and precise connection. </li></ul><ul><li>In larger organizations where a large amount of data is carried across a network, Voice over IP would need a separate infrastructure in order to be utilized. </li></ul><ul><ul><li>Especially in companies where up to 50 phone lines can be used simultaneously an Intranet type of infrastructure will be needed to process the calls with PSPN quality. </li></ul></ul>
  50. 51. VoIP and Convergence <ul><li>Voice, fax, data and multimedia traffic are transmitted over a single multipurpose network </li></ul><ul><li>These advantages include: </li></ul><ul><ul><li>lower recurring transmission charges, </li></ul></ul><ul><ul><li>reduced long-term network ownership costs, and </li></ul></ul><ul><ul><li>the ability to deploy a wide range of powerful voice enabled applications. </li></ul></ul><ul><li>The disadvantages are: </li></ul><ul><ul><li>technology professionals are concerned with the quality of voice calls on the data network </li></ul></ul><ul><ul><li>the stability of voice-over-IP (VoIP) solutions, and </li></ul></ul><ul><ul><li>the consequences of being prematurely &quot;locked-in&quot; to a given vendor’s architecture. </li></ul></ul><ul><ul><li>A lack of expertise and experience with VoIP technology </li></ul></ul><ul><li>By using an intelligent multi-path gateway switch that links the PBX, the data network and the public switched telephone network (PSTN), companies can effectively &quot;hedge their bets&quot; even as they move ahead with their initial VoIP deployments. </li></ul>
  51. 52. VoIP Implementations <ul><li>PBX-based gateways </li></ul><ul><ul><li>The leading manufacturers of PBX equipment are all introducing their own solutions to the VoIP challenge. </li></ul></ul><ul><ul><li>These vendors have minimal experience in IP-centric data networking. </li></ul></ul><ul><ul><li>Without strong expertise in connectionless, non-determinate protocols, it is unclear if they will be able to address the issues of voice signal quality in the IP world. </li></ul></ul><ul><ul><li>A drawback to this approach is that it is tied to highly proprietary PBX platforms with no real record in open technical standards. </li></ul></ul><ul><li>Router-based gateways </li></ul><ul><ul><li>Manufacturers of routers and other data networking hardware are also attacking the VoIP market and have healthy marketshare. </li></ul></ul><ul><ul><li>Their expertise in IP technology should also help them in solving voice quality problems using the IP quality-of-service (QoS) techniques. </li></ul></ul><ul><ul><li>Their unfamiliarity with voice technology and call management hamper their ability to deliver corporate-class telephony solutions. </li></ul></ul>
  52. 53. VoIp Implementations <ul><li>PC-based gateways </li></ul><ul><ul><li>Several vendors are bringing stand-alone gateways to market. These products offer a router- and PBX-independent solution, since they are not tied to a particular manufacturer’s platform. These smaller, more nimble vendors exhibit a greater ability to rapidly adopt – and even help define – emerging standards. </li></ul></ul><ul><li>Alternative to the above </li></ul><ul><ul><li>The multi-path switch. These devices are specifically designed to address the issues unanswered by the product categories described above – including voice quality, network reliability, and vendor independence </li></ul></ul>
  53. 54. VoIP SLA <ul><li>Service level agreements (SLAs) are also a major hindrance for uptake as they tend to be immature, making it harder for vendors and carriers to overcome potential customers' quality of service and security concerns. </li></ul><ul><li>Phil Smith, business development director for Cisco, which is investing heavily in VoIP technologies, agreed. &quot;It's fair comment to say that there is a lot of work to do to educate the market, and we're out there trying to do that,&quot; he said. </li></ul><ul><li>&quot;SLAs are a particularly tricky area because of the sheer number of different players involved in the process of providing VoIP services, but I'm sure that as the market evolves, these will be resolved.&quot; </li></ul><ul><li>Analyst group Frost & Sullivan estimates sales of VoIP gateways at $260m in 2001, set to reach $2.9bn in 2006. </li></ul>
  54. 55. QoS Standards <ul><li>Support for QoS routing can be viewed as consisting of three major components: </li></ul><ul><li>1. Obtain the information needed to compute QoS paths and select a path capable of meeting the QoS requirements of a given request, </li></ul><ul><li>2. Establish the path selected to accommodate a new request, </li></ul><ul><li>3. Maintain the path assigned for use by a given request. </li></ul>
  55. 56. RFC 2676 – QoS Routing <ul><li>QoS Routing Mechanisms and OSPF Extensions </li></ul><ul><ul><li>The assumption is that a flow with QoS requirements specifies the requirements in some fashion that is accessible to the routing protocol. </li></ul></ul><ul><ul><li>This could correspond to the arrival of an RSVP [RZB+97] PATH message, whose TSpec is passed to routing together with the destination address. </li></ul></ul><ul><ul><li>After processing such a request, the routing protocol returns the path that it deems the most suitable given the flow's requirements. </li></ul></ul><ul><ul><li>Depending on the scope of the path selection process, this returned path could range from simply identifying the best next hop, i.e., a hop-by-hop path selection model, to specifying all intermediate nodes to the destination, i.e., an explicit route model. </li></ul></ul><ul><ul><li>In addition to the problem of selecting a QoS path and possibly reserving the corresponding resources, one should note that the successful delivery of QoS guarantees requires that the packets of the associated &quot;QoS flow&quot; be forwarded on the selected path. </li></ul></ul>
  56. 57. Metrics <ul><li>Link available bandwidth: </li></ul><ul><ul><li>The link physical bandwidth or some fraction thereof that has been set aside for QoS flows. Since for a link to be capable of accepting a new flow with given bandwidth requirements, at least that much bandwidth must be still available on the link, the relevant link metric is, therefore, the (current) amount of available </li></ul></ul><ul><li>Link propagation delay: </li></ul><ul><ul><li>This quantity is meant to identify high latency links, e.g., satellite links, which may be unsuitable for real-time requests. </li></ul></ul><ul><ul><li>This quantity also needs to be advertised as part of extended LSAs, although timely dissemination of this information is not critical as this parameter is unlikely to change (significantly) over time. </li></ul></ul><ul><li>Hop-count: </li></ul><ul><ul><li>This quantity is used as a measure of the path cost to the network. A path with a smaller number of hops (that can support a requested connection) is typically preferable, since it consumes fewer network resources. </li></ul></ul>
  57. 58. VoIP Standards <ul><li>H.323 suite of protocols for interworking with H.323 endpoints. </li></ul><ul><ul><li>This allows the system to seamlessly integrate H.248/Megaco-based systems with H.323-based voice-over-IP (VoIP) systems. H.323 is also used to communicate between third-party softswitches. </li></ul></ul><ul><li>SIP for interworking with SIP endpoints. </li></ul><ul><ul><li>This allows the system to seamlessly integrate H.248/Megaco-based systems with SIP-based VoIP systems. SIP is also used to communicate between third-party softswitches. </li></ul></ul><ul><li>H.248 Megaco device control protocols to support the distributed VoIP call control architecture needed to scale up for carrier-class deployments. </li></ul><ul><li>SS7 ISUP for seamless PSTN signaling integration. </li></ul><ul><li>SS7 TCAP for seamless integration with intelligent network-based services. </li></ul>
  58. 59. Reminder : H.323 Network Elements H.323 MCU H.323 Terminal H.323 Gatekeeper H.323 Gateway H.323 Terminal H.323 Terminal PSN CSN V.70 Terminal H.324 Terminal Speech Terminal H.322 Terminal Speech Terminal H.320 Terminal H.321 Terminal GSTN GQOS LAN N-ISDN B-ISDN
  59. 60. Media Gateway Control Protocol MGCP <ul><li>MGCP is designed as an internal protocol within a distributed system that appears to the outside as a single VoIP gateway. </li></ul><ul><li>It is composed of a Call Agent, that may or may not be distributed over several computer platforms, and of a set of gateways, including at least one &quot;media gateway&quot; </li></ul><ul><li>Media Gateway performs the conversion of media signals between circuits and packets, and at least one &quot;signalling gateway&quot; when connecting to an SS7 controlled network. </li></ul><ul><li>In a typical configuration, this distributed gateway system will interface on one side with one or more telephony (i.e. circuit) switches, and on the other side with H.323 conformant systems. </li></ul>