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Mike Whitehead
JANET & TELEPHONYaka Voice over IP
Tim Clark
Networkshop 2000
2
voice trafficon your network?
M
Are youscared of
Networkshop 2000
3M
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
4
The Telephone Networka one minute description
Effectively it’s just a network of 64 kbps switched circuits
Telephonenetwork
analogue phone
digital phone
digital line (ISDN)
analogue line
T
Networkshop 2000
5
The Telephone NetworkInside 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
Networkshop 2000
6
The Telephone NetworkSynchronous Digital Hierarchy
Switches pass data in fixed sized packets (cells) along links of different speeds
T
Networkshop 2000
7M
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
8M
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.
Networkshop 2000
9M
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
Networkshop 2000
10M
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
Networkshop 2000
11M
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
12M
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
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
14M
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
Networkshop 2000
15M
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
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?
T
Networkshop 2000
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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
T
Networkshop 2000
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
T
Networkshop 2000
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
T
Networkshop 2000
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
T
Networkshop 2000
21M
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
22M
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
23M
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
Networkshop 2000
24M
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
25
ATM network
2MbpsConstantBit Rate - CBR
30 channel privatenetwork using DPNSS
ATMG.703
ATMG.703
PABXG.703
PABXG.703
M
ATM between sites
Networkshop 2000
26M
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
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
T
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Distributed site PABX
node Peripheral
cabinets
Mitel SX2000
T
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Node to peripheral cabinet can be ATM
node
ATM network
Peripheral cabinets
Mitel SX2000T
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30
Node to Node - conventional 2 Mbps links
Mitel SX2000
node
2Mbps link
T
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Ideally would be:
node
155 Mbps
link
not Mitel SX2000T
ATM network
Networkshop 2000
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?
T
Networkshop 2000
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
T
Networkshop 2000
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)
T
Networkshop 2000
35
E-mail and voicemailE-mail user interface
T
Networkshop 2000
36
E-mail and voicemailVoicemail user interface
T
Networkshop 2000
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 [email protected] ? Without re-recording it on your PC!
T
Networkshop 2000
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?
T
Networkshop 2000
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
T
Networkshop 2000
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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.
T
Networkshop 2000
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
T
Networkshop 2000
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
T
Networkshop 2000
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
T
Networkshop 2000
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
T
Networkshop 2000
45M
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
46M
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
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.
T
Networkshop 2000
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Reliability - before Telephones
little to go wrong seen as important PABXes never “rebooted”
Data Networks not seen as vital temperamental “high tech” equipment
T
Networkshop 2000
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?
T
Networkshop 2000
50M
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
Networkshop 2000
51M
So why Voice over IP? Data networks must be ever more reliable Convergence growing:
Interoperability good Quality is good
Licensing is same for voice and data and many more IP is the protocol of choice
Networkshop 2000
52M
Organisation & Culture Who runs telephone services?
Often within administration or estates.
Staff have different backgrounds & culture Telecomms staff treasure their heritage Data network staff treat voice as “dirty”
Even end-users have different cultural approach to voice and data networks
Organisations merging the operations Must co-operate and converge
Networkshop 2000
53
how do you phone the Help Desk
When your PC becomes your phone ....
M
and it breaks down ...
?
Networkshop 2000
54M
Will it really happen? Technology is definitely converging What are the real drivers?
Probably not really the cost savings
Facilities are the big driver Key could be collaborative working
That’s what the telephone is good at That’s a great use for multimedia PCs
Networkshop 2000
55M
What to do next..... Understand how to run a voice service Persuade your organisation to prepare
Especially management issues
Get your networks ready Build in resilience and QoS Savings on PABX may pay for this!
When? Heroic to go wholly VoIP today Reprehensible to ignore it in 2 years time
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56
Time for Discussion
Networkshop 2000
57
Thank you for coming