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INLS184Architectures and Issues in

Real Time Conferencing Protocols

Tyler Miller-Johnson

University of North Carolina at Chapel Hill

April 6, 2004

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4Exercise – Exploring Standards

• What is a standard ?

• What is the purpose of a standard ?

• Name 3 standards.

• What characteristics are desirable in a standards body ?

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4Exercise: What is a standard ?

• De facto• De jour• Proprietary• Agreed upon set of rules, set by authoritative

body• Set of rules to maintain consistency across an

industry• Accepted common system of procedures to

provide a uniform method of design and/or operation

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4Exercise: What is the purpose

of a standard ?• Avoid inefficiency

• Ensure interoperability

• Guide and ensure development

• Quality

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4Exercise: Examples of standards

• Traffic signs• Electricity• Food labels• IEEE 802.11b/g• Address an envelope• Phone conversation• RJ-45• TCP/IP• Metric system• IEEE 1394• ISO 9600• MARC for cataloging

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4Exercise: What characteristics are

desirable in a standards body ?

• Open• Non partial• Non proprietary• Simple• Respected• Rational• Knowledgeable• Uniform

• Quick• Thorough• Multiple

manufactures• Represent users of

the system• Widely accessible

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4Case Study:

Standardized Addressing Modes• URL Based Dialing

– Uses DNS to resolve address of call server– Uses endpoint registration to resolve endpoint address– Example h323:tyler@gk.unc.edu

• ENUM– Uses DNS to translate a phone number into an URL– Phone numbers under municipal control– Example +1.(919) 843-7004 becomes:

• 4.0.0.7.3.4.8.9.1.9.1.e164.arpa• <h323:tyler@gk.unc.edu>

• What are the social, GUI, market and technical consequences of this choice?

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4Comparing Standards Bodies

ITU / IETF

• International Telecommunications Union– Inter-governmental

organization under the umbrella of the United Nations (www.itu.int)

– Covers multiple topic and networks

– US Representation through US State Department

– Annual Cost• Associate: $7000• Sector: $40,000

• Internet Engineering Task Force– International community

of network designers, operators, vendors, and researchers chartered under ISOC (the Internet Society)

– Focused on Internet– No governmental

oversight– Annual Cost

• Individual: $0• ISOC Corporate:

variable with graduated benefits

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4What Are Real Time Communications?

• Applications– Voice Over IP

• IP Telephony• Interactive Audio

Conferencing• Modem Over IP• Fax Over IP

– Video Conferencing– Instant Messaging– Presence

• Standards– H.323

• Voice• Video

– SIP• Voice• Presence• Instant Messaging• Video

– XMPP• Instant Messaging

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4

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4What Could You Do With This

Technology ?

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4Typical H.323 Stack

H.323

IP

UDP

RTP

RTCP

TCP/UDP TCP UDPUDP TCP

Audio

Codecs

G.711

G.723.1

G.729

..

Video

Codecs

H.261

H.263

H.264

..V.150 T.120

TCP/UDP

T.38

H.225.0

Call

Signaling

H.245H.225.0

RAS

Terminal Control and ManagementData

ApplicationsMedia Control

Multimedia Applications, User Interface

* source: Paul Jones, ITU-T H.323 Rapporteur SIP

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4Basic Architectural Elements

• Registration• Call Setup• Media Flow

• Smart endpoints– H.323, SIP

• Dumb endpoints– H.248, PSTN

Call ServerGateway MCU

AudioVideo

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4Firewall / NAT Issues

• NAT hides destination address• Communication out, but not in• Application Level Gateways

– Protocol Aware– Encryption breaks

Call ServerGateway MCU

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Security

Knock, Knock.

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Who’s There ?

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4Security Elements

• Authentication– Proving someone’s identity

• Authorization– What are they allowed to do?

• Privacy– Encryption of media– Encryption of call signaling

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4Regulatory Issues

• HIPPA requires privacy. CALEA requires wiretapping.• Service provider has no access to media• Media and call signaling may be encrypted• Service providers may become ubiquitous• Service providers may not fall under regulations (i.e. in another country)• “Help, I’ve fallen and I can’t get up !” – 911• How do we tax?

Call ServerGateway MCU

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4Our Thinking Is All Wrong !

• Old– End users need access to central resources– End users are ‘clients’– IT must protect itself against end user abuse– Home domain is the world

• New– End users need access to each other– End users are servers and service providers– End users need to authenticate each other– The world is a large and complex place, but we

want to live there!

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4E2M Security(user ID / password)

• Pros– Ensures nobody steals

service provider’s resources

– Ensures you pay your bill

• Cons– Doesn’t allow you to

access resources in other realms

– Doesn’t provide caller ID– Doesn’t recognize true

people to people nature of application

Call Server

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4E2E Security

(X.509 certificates - PKI)

• Pros– Confirms your identity to

the called party– Works across realms

• Cons– Requires common

authentication across reams

– Other applications don’t use this approach

– Administrative cost to identity verification

Incoming Call From:

Dr. Thomas GrayRadiology

<OK> Duke University<OK> Internet2

Call Server

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4How Does Federation Help ?

• E2E security features• Still implement your own authentication methods• Recognizes the world is a messy place

Call Server

Incoming Call From:

Dr. Thomas GrayRadiology

<OK> Duke University<OK> Internet2

Duke UNC

Internet2

Federation

Provider A Provider B

FCC

Federation

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4This Changes Everything

• Access to many service providers• Not necessarily required to pre-establish accounts• Call signaling and networks can be un-secured

Incoming Call From:Sarah McAllister

<OK> VISA 123456<OK> Provider A<OK> FCC

DukeHospital

UNCHospital

Federation

Provider A Provider B

FCC

Federation

MCUProvider

VoIPProvider

VoIPProvider

PTAFundraiser