dce project 1999 - internet telephony1 internet telephony %introduction %what is it? %history %ip...
TRANSCRIPT
DCE Project 1999 - Internet Telephony 1
Internet Telephony
Introduction
What is it?
History
IP Telephony v. PSTN
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IP Telephony v PSTN
Calls broken to pieces and sent to
destination Better use of
network capacity
Data Network 80% reliable
Downtime is 4 hours per month (Data Communications)
Dedicated circuit
for each call
Telephone
Network 99.999%
reliable
Downtime
measured in
seconds per year
Regulation
Data Packet Switched Circuit Switched
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Voice Gateways
Physical interfacePlaced between PSTN and IP
NetworkHandles
signaling to and from telephone networkreception of telephone numbersconversion of tel nos to IP addressesvoice processing
reception of voice signalcompression(to reduce bandwidth and
delay impact from Network) and packetization
echo cancellationsilence suppression
No of gateways crucial - around 500 in existence
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IP Telephony Network
Gatekeeper
GatewayGateway
Gateway
RT
RT
PSTNPSTNISDN
RT
RT
IP Network
Gateway : Bridge between PSTN & IP NetworksGatekeeper : Admission control for network
Bandwidth control and managementAddress translation (E.164 <-> IP address)Call Management
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IP Telephony Services
Encompassesphone-to-phonephone-to-PCPC-to-PCfax-to-faxvideo conferencingdesktop collaboration
Software such asMicrosoft NetMeetingDeltaThree’s DotDialerIDT’s Net2Phone
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Standards
Why do we need them?The benefits of
standardisation• Interoperability• billing, settlement and reconciliation• uniformity for carriers• marketability
Currently • no standards for signaling• no standard agreement on
accounting records or billing
These issues being handled through maturing standards such as ITU’s
• H.323• Tiphon
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H.323-The Vendors Choice?
H.323 recommends G.723• compresses voice to 5.3 or 6.3 kbit/s
Some using GSM algorithm• compresses to 13.3 kbit/s, appears
to provide superior quality to G.723
Tiphon• based on H.323
• specifies network architecture, numbering, supplementary services integration
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Security
Initially somewhat overlooked, now being raised by carriers and business users
Security Issues• User and data authentication• Data privacy (integrity,
confidentiality)• Access control• Policy management
Security Measures• Encryption
– SSL (secure sockets layer) – TLS (transport layer security)
• Tunnelling– Layer 2 Tunnelling Protocol (L2TP)– establish a secure tunnel between
gateways or gatekeepers
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Encryption
SSL, TLS on transport level, suitable for Gatekeeper-to-gatekeeper, but not if unreliable, connectionless UDP transports the voice
IETF IPsec working group describes security architecture for IP protocol that makes it suitable for secure VPN
authenticates usersencrypts payloadtracks who has changed packet
Incorporated in H.323 V2 via H.235 also called H Secure
Encryption ProblemsPolitical/military issues (limits on keys etc)Hardware issues (processing power)
Dealing with security issues US Chamber of commerce announced automatic
approvals for financial institutions Therefore encryption more readily available??
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Effect on the Traditional Communications
Companies
Telecommunications or
information service?
Telecommunications Act
1996promote competitionfacilitate new
telecommunications technologies
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Economics
Cost savings dependent on the provider and location
Calls between London and Tokyo around 30 cents per minute ($1 per minute for POTS)
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The Future
Market predicted to grow to $560 million by end of 1999
By 2002, 3% of US long-distance traffic, 5% of European long-distance traffic, 14% of US international traffic and 11% of European international traffic
Not economic but service benefit
Used with video and data sharing for multi-media communications