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Mike Whitehead JANET & TELEPHONY aka Voice over IP Tim Clark.

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Presentation on theme: "Mike Whitehead JANET & TELEPHONY aka Voice over IP Tim Clark."— Presentation transcript:

1 Mike Whitehead JANET & TELEPHONY aka Voice over IP Tim Clark

2 Networkshop voice traffic on your network? M Are you scared of

3 Networkshop M What is Voice Traffic? uIs Voice traffic special? uOr just another network application like any other? uWill it require a radical change in networking technology and practice?

4 Networkshop The Telephone Network a one minute description Effectively its just a network of 64 kbps switched circuits Telephone network analogue phone digital phone digital line (ISDN) analogue line T

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

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

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

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

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

10 Networkshop M What is IP Telephony? uBetween sites l aka Toll Bypass l Keep the PABX and use the MAN/WAN uWithin sites l aka The Full Monty l replace the PABX with LAN/MAN & PCs uDemonstrations at the Exhibition

11 Networkshop M Voice as a bitstream uEncoding 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, 40Kbps1ms coding time G.728 CELP (LD Code excited linear prediction) –16Kbps2.5ms coding time G.729 CS-ACELP Quality similar to 32Kbps ADPCM –8Kbps10ms coding time G Multirate Coder –5.3, 6.3Kbps30ms coding time

12 Networkshop M What are the problems? uDelay caused by: l Encoding time - can be 30ms l Network delay - say 100ms uVariable Delay = Jitter uCongestion -> Dropped packets uDelay causes problems l Echo - l Talker overlap

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

14 Networkshop M H.323 uFamily H.320 (ISDN), H.324 (POTS), etc. uH.323 runs over non-guaranteed packet switched network (e.g. IP) uGateways to other systems uVoice (G.711 mandatory), video optional uMultimedia, multipoint, multicast support uGatekeepers l Bandwidth control, address translation l Routing and billing control

15 Networkshop M Quality of Service uPhones do this with circuit switching uNeed to ensure l enough bandwidth from end to end l enough bandwith at start of call l enough available throughout the call

16 Networkshop 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 u How? T

17 Networkshop Homes & Small Businesses uSubscriber Loop uThe last few kilometres of the run uExisting cable is not the ideal medium for broadband communication uBut it is expensive to replace T

18 Networkshop Digital Subscriber Loop uTechniques for making the most of the existing twisted pair l retaining its use for ordinary analogue telephony too uNot cat 5 twisted pair but rusty old copper uNot a new approach - but recent jargon ulatest techniques are sophisticated T

19 Networkshop ADSL Asymmetric Digital Subscriber Loop uAsymmetric - different speed up and down uBT is rolling it out uCable companies interested too uOther companies want BTs local loop uPrices of the technology will fall l it is mass market T

20 Networkshop ADSL What does it mean for us? uDelivery to home, SMEs and small outposts uNot and end-to-end service - but telephone exchange to subscriber uSo we cant treat it as a new type of modem service uEstablish relationships with telcos uOn campus residences l alternative to cat 5 T

21 Networkshop M Video Conferencing uEssentially a telephone call with pictures! uGreedy bandwidth l Broadcast video needs oodles uUse compression as with voice l M-JPEG over ATM uses 10-20MB l ISDN-2 offers 128Kbps

22 Networkshop M Video Conferencing uTelephony based video conferencing: ISDN uData network based video conferencing: l Carried over ATM and IP uOffer different services uProvide different qualities uNeed gateways to interwork

23 Networkshop M Video Conferencing uIf your network can carry video l a very high bandwith application uSurely it can carry voice l much less bandwidth hungry uThough voice far more susceptible to jitter

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

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

26 Networkshop M ATM between sites uUses standard ATM circuit l Constant Bit Rate 2Mbps uPABX sees standard interface l E1 G.703 2Mbps - 30 channels l Can run standard DPNSS - private trunks uSimple standards - no compression uPermanent 2Mbps bandwidth assigned

27 Networkshop ATM: intra-campus PABXes uSingle site, but distributed PABX uOnce it was thought ATM would be the unifying technology for voice and data uBut: uPABX move to ATM not as fast as had been hoped uMeanwhile data networks using alternative technologies - like Gigabit Ethernet T

28 Networkshop Distributed site PABX node Peripheral cabinets Mitel SX2000 T

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

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

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

32 Networkshop Intra-campus PABXes uData Network mixed technology l Fast Ether, Gigabit Ether l ATM - especially to remote campuses uPABX manufacturers are using PC servers as PABXes uData Network switch manufacturers are interfacing to telephones uIs IP the new unifying protocol? T

33 Networkshop and voic 1. Voic uNow more like than an answering machine uVoic servers are ordinary computers they often l store messages on disks in the same format as ordinary computers l communicate using standard LAN protcols uSometimes even allow desktop PCs access as clients T

34 Networkshop and voic 2. uMany useful facilities developed: l Distribution Lists l Automatic filtering l …etc. uMIME allows audio attachments uMore intuitive user interface l (perhaps) T

35 Networkshop and voic user interface T

36 Networkshop and voic Voic user interface T

37 Networkshop and voic ripe for convergence uBut it is only just starting to happen. uHow many have a voic box which telephone callers can leave messages in? uHow many of you could forward a message from that voic box to ? l Without re-recording it on your PC! T

38 Networkshop Policy uPolicy itself is more a matter for the Network Strategy workshop uBut: the opportunities and obstacles which regulatory and charging policies present often pose technical challenges uWhat are they? T

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

40 Networkshop Charging 1. IP uTraditionally - pay for leased line / bandwidth uWithout usage based charging: l runaway costs l or cap the supply uPay per byte would seem the way uBut with IP you cant tell who caused a particular packet to flow. T

41 Networkshop Charging 2. Telephony uCharge by circuit occupancy l i.e. calls charged by time uRunning costs not as strongly related to use as charges suggest uHigh standing charge socially unacceptable uCan stifle Internet access by phone uRapid changes taking place T

42 Networkshop Telephony over SuperJANET I, II and III uGreater difference between local and long distance charges uPotential for huge savings uBut: l regulatory issues made it difficult l providers terms made it impossible l UKERNA had no remit uIt didnt happen T

43 Networkshop Telephony over SuperJANET4 uOperational requirement states: The supplier must place no restriction on UKERNAs use of the facilities provided uDifferential between local and long distance call charges narrowed l So major incentive gone T

44 Networkshop Telephony over SuperJANET4 uSuperJANET4 is an IP network l no major additional infrastructure needed on SuperJANET if we use voice over IP. uGradual change: l voic / l video conferencing (video phone calls) l IP voice traffic will just happen T

45 Networkshop M Telecommunications Licensing uAll telecommunications need a licence l Telecommunications Act 1984 uWidely applicable l Voice and data traffic are both regulated uYou can operate under standard licences l SPL = Self Provision Licence l TSL = Telecommunications Service Licence uMost MANs and HEI networks violate rules

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

47 Networkshop Policy, Regulation and Charging Technological Impact uSwift changes in policy (e.g. Charges) make sudden demands on the technology. uWhat was impractical, becomes practical, and vice versa. uSo some technology which is out of favour today may be in favour tomorrow. uKeep abreast of what technology can deliver to meet changes in policy. T

48 Networkshop Reliability - before uTelephones l little to go wrong l seen as important l PABXes never rebooted uData Networks l not seen as vital l temperamental high tech equipment T

49 Networkshop Reliability - now uPABX runs software - it does go down uData network equipment often more reliable than before (but there is more of it) uData network outages have larger impact than before uHave we got convergence of reliability and importance too? T

50 Networkshop M So why Voice over IP? uWhy run two systems? l Two networks, cables and staff? uAvoid (high) call charges uMultimedia PCs make good phones l Featurephones are expensive l Standard handsets lousy for PABX features l but features via a GUI are much easier uUnified messaging (Voice mail & ) uCollaborative working growing

51 Networkshop M So why Voice over IP? uData networks must be ever more reliable uConvergence growing: l Interoperability good l Quality is good uLicensing is same for voice and data uand many more uIP is the protocol of choice

52 Networkshop M Organisation & Culture uWho runs telephone services? l Often within administration or estates. uStaff have different backgrounds & culture l Telecomms staff treasure their heritage l Data network staff treat voice as dirty uEven end-users have different cultural approach to voice and data networks uOrganisations merging the operations uMust co-operate and converge

53 Networkshop how do you phone the Help Desk When your PC becomes your phone.... M and it breaks down... ?

54 Networkshop M Will it really happen? uTechnology is definitely converging uWhat are the real drivers? l Probably not really the cost savings uFacilities are the big driver uKey could be collaborative working l Thats what the telephone is good at l Thats a great use for multimedia PCs

55 Networkshop M What to do next..... uUnderstand how to run a voice service uPersuade your organisation to prepare l Especially management issues uGet your networks ready l Build in resilience and QoS l Savings on PABX may pay for this! uWhen? l Heroic to go wholly VoIP today l Reprehensible to ignore it in 2 years time

56 Networkshop Time for Discussion

57 Networkshop Thank you for coming

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