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