JANET & TELEPHONY aka Voice over IP

1. JANET & TELEPHONYaka Voice over IP Mike Whitehead Tim Clark

2. voice trafficon your network? Are you scared of M Networkshop 2000

3. What is Voice Traffic? • Is Voice traffic special? • Or just another network application like any other? • Will it require a radical change in networking technology and practice? Networkshop 2000 M

4. The Telephone Networka one minute description Effectively it’s just a network of 64 kbps switched circuits analogue phone analogue line Telephone network digital line (ISDN) digital phone Networkshop 2000 T

5. The Telephone NetworkInside the network 64 kbps 2 Mbps 30 x 34 Mbps 8 x Time Division Multiplexing using the old PDH scheme to carry multiple circuits down a single higher speed circuit Networkshop 2000 T

6. The Telephone NetworkSynchronous Digital Hierarchy Switches pass data in fixed sized packets (cells) along links of different speeds Networkshop 2000 T

7. Convergence • Data networks are becoming • more reliable • more affordable • more flexible • Data networks can carry voice traffic • in theory if not in practice • Telephone cabling can carry data networks • Now well beyond the simple MODEM level • Technologies like xDSL bring usable bandwidth. Networkshop 2000 M

8. Convergence • IP Telephony and other ways of getting voice over the Data Network • Carrying Voice over data networks • Variety of technologies • Direct use of ATM for dedicated voice circuits is one extreme • Use of standard IP transactions over the Internet at the other extreme. • In between, are enhancements to existing circuits such as Quality of Service extensions. M Networkshop 2000

9. What is Convergence? • Payload convergence • e.g. Voice typically uses Layer 1 but can now use Layer 3 for voice and for data • Protocol convergence • e.g. data over ATM networks, voice over data (VoIP) • Physical convergence • e.g. using the same cabling for voice and data • Device convergence • e.g. PABX with computer features (CTI, Voice Mail) • e.g. Router with telephone capabilities M Networkshop 2000

10. What is IP Telephony? • Between sites • aka “Toll Bypass” • Keep the PABX and use the MAN/WAN • Within sites • aka “The Full Monty” • replace the PABX with LAN/MAN & PCs • Demonstrations at the Exhibition M Networkshop 2000

11. Voice as a bitstream • Encoding and Compression Standards: • G.711 PCM sampling 8,000 per sec, 8bit coding • 56 or 64Kbps 0.75ms coding time • G.726 ADPCM (Adaptive Differential PCM) 4 bits • 16. 24, 32, 40Kbps 1ms coding time • G.728 CELP (LD Code excited linear prediction) • 16Kbps 2.5ms coding time • G.729 CS-ACELP Quality similar to 32Kbps ADPCM • 8Kbps 10ms coding time • G.723.1 Multirate Coder • 5.3, 6.3Kbps 30ms coding time Networkshop 2000 M

12. What are the problems? • Delay caused by: • Encoding time - can be 30ms • Network delay - say 100ms • Variable Delay = Jitter • Congestion -> Dropped packets • Delay causes problems • Echo - • Talker overlap Networkshop 2000 M

13. Overcoming the problems • Delay: • Solutions involve interpolation & holdback • Prioritisation - Layer 2 Standards available: • 802.1p - offers expedited traffic • by priority tagging • 802.1q - provides the tagging on VLANs • Layer 3 standards (IP) • ToS = Type of Service • old but little used until now M Networkshop 2000

14. H.323 • Family H.320 (ISDN), H.324 (POTS), etc. • H.323 runs over non-guaranteed packet switched network (e.g. IP) • Gateways to other systems • Voice (G.711 mandatory), video optional • Multimedia, multipoint, multicast support • Gatekeepers • Bandwidth control, address translation • Routing and billing control M Networkshop 2000

15. Quality of Service • Phones do this with circuit switching • Need to ensure • enough bandwidth from end to end • enough bandwith at start of call • enough available throughout the call Networkshop 2000 M

16. SuperJANET 4 - The forces for change “The network must respond to the migration of the learning process from its traditional base in the classroom, lecture theatre and laboratory, and into the home and the workplace” - UKERNA / JISC, December 1999 • How? Networkshop 2000 T

17. Homes & Small Businesses • Subscriber Loop • The last few kilometres of the run • Existing cable is not the ideal medium for broadband communication • But it is expensive to replace Networkshop 2000 T

18. Digital Subscriber Loop • Techniques for making the most of the existing twisted pair • retaining its use for ordinary analogue telephony too • Not cat 5 twisted pair but “rusty old copper” • Not a new approach - but recent jargon • latest techniques are sophisticated Networkshop 2000 T

19. ADSLAsymmetric Digital Subscriber Loop • Asymmetric - different speed up and down • BT is rolling it out • Cable companies interested too • Other companies want BT’s local loop • Prices of the technology will fall • it is mass market Networkshop 2000 T

20. ADSLWhat does it mean for us? • Delivery to home, SMEs and small outposts • Not and end-to-end service - but telephone exchange to subscriber • So we can’t treat it as a new type of modem service • Establish relationships with telcos • On campus residences • alternative to cat 5 Networkshop 2000 T

21. Video Conferencing • Essentially a telephone call with pictures! • Greedy bandwidth • Broadcast video needs oodles • Use compression as with voice • M-JPEG over ATM uses 10-20MB • ISDN-2 offers 128Kbps Networkshop 2000 M

22. Video Conferencing • Telephony based video conferencing: ISDN • Data network based video conferencing: • Carried over ATM and IP • Offer different services • Provide different qualities • Need gateways to interwork Networkshop 2000 M

23. Video Conferencing • If your network can carry video • a very high bandwith application • Surely it can carry voice • much less bandwidth hungry • Though voice far more susceptible to jitter M Networkshop 2000

24. The Role of ATM • Use of ATM for crude interlinking of PABX • using 2Mbps circuit traffic (Mike) • Use of ATM by PABXes themselves • with Mitel as an example (Tim) Networkshop 2000 M

25. ATM between sites 30 channel private network using DPNSS PABX G.703 ATM ATM network G.703 2Mbps ATM Constant Bit Rate - CBR PABX G.703 G.703 Networkshop 2000 M

26. ATM between sites • Uses standard ATM circuit • Constant Bit Rate 2Mbps • PABX sees standard interface • E1 G.703 2Mbps - 30 channels • Can run standard DPNSS - private trunks • Simple standards - no compression • Permanent 2Mbps bandwidth assigned Networkshop 2000 M

27. ATM: intra-campus PABXes • Single site, but distributed PABX • Once it was thought ATM would be the unifying technology for voice and data • But: • PABX move to ATM not as fast as had been hoped • Meanwhile data networks using alternative technologies - like Gigabit Ethernet Networkshop 2000 T

28. Distributed site PABX node Peripheral cabinets Mitel SX2000 Networkshop 2000 T

29. Node to peripheral cabinet can be ATM node ATM network Peripheral cabinets Mitel SX2000 Networkshop 2000 T

30. Node to Node - conventional 2 Mbps links node 2Mbps link Mitel SX2000 Networkshop 2000 T

31. Ideally would be: node 155 Mbps link ATM network not Mitel SX2000 Networkshop 2000 T

32. Intra-campus PABXes • Data Network mixed technology • Fast Ether, Gigabit Ether • ATM - especially to remote campuses • PABX manufacturers are using PC servers as PABXes • Data Network switch manufacturers are interfacing to telephones • Is IP the new unifying protocol? Networkshop 2000 T

33. E-mail and voicemail1. Voicemail • Now more like E-mail than an answering machine • Voicemail servers are “ordinary” computers they often • store messages on disks in the same format as “ordinary computers” • communicate using standard LAN protcols • Sometimes even allow desktop PCs access as clients Networkshop 2000 T

34. E-mail and voicemail2. E-mail • Many useful facilities developed: • Distribution Lists • Automatic filtering • …etc. • MIME allows audio attachments • More intuitive user interface • (perhaps) Networkshop 2000 T

35. E-mail and voicemailE-mail user interface Networkshop 2000 T

36. E-mail and voicemailVoicemail user interface Networkshop 2000 T

37. E-mail and voicemailripe for convergence • But it is only just starting to happen. • How many have a voicemailbox which telephone callers can leave messages in? • How many of you could forward a message from that voicemailbox to T.Clark@warwick.ac.uk ? • Without re-recording it on your PC! Networkshop 2000 T

38. Policy • Policy itself is more a matter for the Network Strategy workshop • But: the opportunities and obstacles which regulatory and charging policies present often pose technical challenges • What are they? Networkshop 2000 T

39. Charging • Challenges arise due to the way which IP networks on the one hand, and telephony on the other, have approached charging • As the technologies merge, the differences present both opportunities and obstacles Networkshop 2000 T

40. Charging1. IP • Traditionally - pay for leased line / bandwidth • Without usage based charging: • runaway costs • or cap the supply • Pay per byte would seem the way • But with IP you can’t tell who caused a particular packet to flow. Networkshop 2000 T

41. Charging2. Telephony • Charge by circuit occupancy • i.e. calls charged by time • Running costs not as strongly related to use as charges suggest • High standing charge socially unacceptable • Can stifle Internet access by phone • Rapid changes taking place Networkshop 2000 T

42. Telephony overSuperJANET I, II and III • Greater difference between “local” and “long distance” charges • Potential for huge savings • But: • regulatory issues made it difficult • providers’ terms made it impossible • UKERNA had no remit • It didn’t happen Networkshop 2000 T

43. Telephony over SuperJANET4 • Operational requirement states: “The supplier must place no restriction on UKERNA’s use of the facilities provided” • Differential between “local” and “long distance” call charges narrowed • So major incentive gone Networkshop 2000 T

44. Telephony over SuperJANET4 • SuperJANET4 is an IP network • no major additional infrastructure needed on SuperJANET if we use voice over IP. • Gradual change: • voicemail / e-mail • video “conferencing” (video phone calls) • IP voice traffic will just happen Networkshop 2000 T

45. Telecommunications Licensing • All telecommunications need a licence • Telecommunications Act 1984 • Widely applicable • Voice and data traffic are both regulated • You can operate under standard licences • SPL = Self Provision Licence • TSL = Telecommunications Service Licence • Most MANs and HEI networks violate rules Networkshop 2000 M

46. Licensing Issues • Current situation • Problems recognised by Oftel & DTI • no enforcement • (perhaps voice traffic could precipitate it) • EU directives require issues to be addressed • JISC, UK MANs group, etc. working on it • Oftel assisting • DTI have plans for new class licences for education Networkshop 2000 M

47. Policy, Regulation and ChargingTechnological Impact • Swift changes in policy (e.g. Charges) make sudden demands on the technology. • What was impractical, becomes practical, and vice versa. • So some technology which is out of favour today may be in favour tomorrow. • Keep abreast of what technology can deliver to meet changes in policy. Networkshop 2000 T

48. Reliability - before • Telephones • little to go wrong • seen as important • PABXes never “rebooted” • Data Networks • not seen as vital • temperamental “high tech” equipment Networkshop 2000 T

49. Reliability - now • PABX runs software - it does “go down” • Data network equipment often more reliable than before (but there is more of it) • Data network outages have larger impact than before • Have we got convergence of reliability and importance too? Networkshop 2000 T

50. So why Voice over IP? • Why run two systems? • Two networks, cables and staff? • Avoid (high) call charges • Multimedia PCs make good phones • Featurephones are expensive • Standard handsets lousy for PABX features • but features via a GUI are much easier • Unified messaging (Voice mail & email) • Collaborative working growing M Networkshop 2000