Transitioning the PSTN to IP

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Henning Schulzrinne

IETF86

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The retirement of the circuit-switched network

• What is happening and why does it matter?
• What are the technical challenges we need to address?
• reliability & quality
• public safety (“911”, “112”)
• numbering & trustable identifiers
• universal service
• service stagnation 🡪 beyond voice?
• copper loops 🡪 competition, legacy services
• It’s technical + economics + policy

IETF86

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US-centric, but similar elsewhere

FCC’s Technology Transition Policy Task Force

• The Task Force’s work will be guided by the insight that, technological changes do not alter the FCC’s core mission, including protecting consumers, ensuring public safety, enhancing universal service, and preserving competition.
• The Task Force will conduct a data-driven review and provide recommendations to modernize the Commission’s policies in a process that encourages continued investment and innovation in these new technologies, empowers and protects consumers, promotes competition, and ensures network resiliency and reliability.

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The three transitions

IETF86

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VoIP, VoLTE

When?

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TDM

switching

(core)

VoIP

access

fixed 4G

2013

no single transition date!

numbering

E.164

human-visible

hidden

“wireless network is 99% wired”

The transition of the PSTN

• User behavior changes
• more text, less voice
• video conferencing for personal & business use (telepresence)
• landline 🡪 mobile
• OTT VoIP (for international calls)
• Core network technology changes
• IMS
• SIP trunking
• Access and end system changes
• large PBX all VoIP
• voice as app
• WebRTC

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Available access speeds

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100 Mb/s+

20 Mb/s

5 Mb/s

2 Mb/s

1 Mb/s

18%

80%

95%

97%

100%

avg. sustained

throughput

of households

marginal VOIP

10 Gb/s

common now – future capability

1 Gb/s

10 Mb/s

99% by 2023?

Access transitions (US)

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fiber

4G

copper

coax

unlicensed

wireless

⊕

networks go hybrid:

last 500-3000 ft

Landline 🡪 mobile

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Lines are disappearing, but maintenance costs are constant

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$2.72

per-line monthly

maintenance

cost

$17.57

voice revenue/line: $50

dis

voice only

(DSL: 20 M)

JSI Capital Advisors projection

Switches are ageing

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1979

Nortel DMS-100

http://www.phworld.org/switch/ntess.htm

PSTN: The good & the ugly

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What are some of the “keeper” attributes?

• Universality
• reachability 🡪 global numbering & interconnection
• media 🡪 HD audio, video, text
• availability 🡪 universal service regardless of
• geography
• income
• disability
• affordability 🡪 service competition + affordable standalone broadband

• Public safety
• citizen-to-authority: emergency services (911)
• authority-to-citizen: alerting
• law enforcement
• survivable (facilities redundancy, power outages)
• Quality
• media (voice + …) quality
• assured identity: telephone numbers
• assured privacy (CPNI)
• accountable reliability

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initial list – not exhaustive

Universal service

• Eligible Telecommunications Carriers
• Carrier of Last Resort (COLR)
• Universal Service Fund

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For the purpose of regulating interstate and foreign commerce in communication by wire and radio so as to make available, so far as possible, to all the people of the United States, without discrimination on the basis of race, color, religion, national origin, or sex, a rapid, efficient, Nation-wide, and world-wide wire and radio communication service with adequate facilities at reasonable charges, for the purpose of the national defense, for the purpose of promoting safety of life and property through the use of wire and radio communications, … (47 USC § 151, 1934)

One Policy, One System, Universal Service

T. Vail

(1907)

Numbers: Disappearance of the old constraints

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The number is part of the problem

• Geographically assigned (“area codes”)
• except for VoIP and cellular (US)
• Separate numbering for SMS, voice, wireless, …
• Only traditional carriers can obtain numbers
• Complex local number portability
• limited wireless 🡺 wireline porting (“wire centers”)’
• Service tied to number 🡪 makes 3^rd party services difficult

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It’s just a number

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Communication identifiers

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Numbers vs. DNS & IP addresses

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Number usage

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FCC 12-46

Area codes (NPAs)

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634

Phone numbers for machines?

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212 555 1212

< 2010

500 123 4567

533, 544

now: one 5XX code a year…

(8M numbers)

see Tom McGarry, Neustar

500 123 4567

(and geographic numbers)

10 billion available

5 mio.

64 mio.

12% of adults

311,000

Future numbers

• Should numbers be treated as names?
• see “Identifier-Locator split”
• “multi-homing”
• Should numbers have a geographic component?
• Is this part of a region’s cultural identity?

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Caller ID spoofing

• Easily available on (SIP) trunks – can be legitimate
• Used for vishing, robocalling, swatting, anonymity breaking, …
• Caller ID Act of 2009: Prohibit any person or entity from transmitting misleading or inaccurate caller ID information with the intent to defraud, cause harm, or wrongfully obtain anything of value.
• Also: phantom traffic rules

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Robocalling

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“pink carriers”

Security (trustworthiness)

• Practically, mostly about identity, not content
• Old model: “trust us, we’re the phone company”
• Need cryptographically-verifiable information
• Is the caller authorized to use this number?
• not necessarily “ownership”
• Has the caller ID name been verified?
• cf. TLS

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Who assures identity?

• Web:
• plain-text 🡪 rely on DNS, path integrity
• requires on-path intercept
• X.509 certificate: email ownership
• no attributes
• EV (“green”) certificate
• PSTN
• caller ID
• display name: CNAM database, based on caller ID

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Strawman “Public” PSTN database

• Now: LIDB & CNAM, LERG, LARG, CSARG, NNAG, SRDB, SMS/800 (toll free), do-not-call, …
• Future:

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carrier code or SIP URLs

type of service (800, …)

owner

public key

…

1 202 555 1234

extensible set of fields

multiple interfaces (legacy emulation)

multiple providers

DB

HTTPS

VoIP interconnection, public safety, universal access

IETF86

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VoIP Interconnection

• “VoIP interconnection” ≠ IP peering
• Are there technical stumbling blocks?
• SIP features?
• Media codecs & conversion?
• Separation application layer & transport
• $0.001 / minute for IP transport ($0.10/GB) 🡪 location not relevant

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Cisco

Public Safety (NG911 & NG112)

• Transition to NG911 & NG112 underway
• NGxxx = all-IP (SIP + RTP) emergency calling
• Key issues:
• Indoor location for wireless
• location accuracy of 50/150m may not be sufficient
• need apartment-level accuracy, including floor
• Civic (Apt. 9C, 5 W Glebe), not geo
• Cost, scaling and transition

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IETF86

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More than point-to-point voice

• VoIP = Voice + Video + Vords (text)
• 🡪 Real-time communication as base-level service?
• Accommodate new media codecs (e.g., AMR)
• See also “advanced communication systems” in U.S. Communications and Video Accessibility Act (CVAA)
• Just point-to-point? or multipoint?
• Services beyond call forwarding 🡪 web API model
• e.g., for robocall prevention

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Reliability

• 5 nines 🡪 5 minutes/year unavailable
• How do we measure reliability & QoS?
• E.g., FCC Measuring Broadband America project?
• 🡪 IETF LMAP
• Can we improve power robustness?
• Circuit-switched: -48V @ 20-50 mA (~ 1 W)
• e.g., DOCSIS modem consumes ~7W (idle)
• Li-Ion battery = 2.5 Wh/$ 🡺 3$/hour of standby time
• Can we simplify multihoming to make new PSTN more reliable than old?
• e.g., cable + 4G

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IETF86

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Conclusion

• Three simultaneous technology transitions:
• copper 🡪 fiber, wired 🡪 wireless, circuit 🡪 packet
• But no cut-over date
• Need to “grow up” quickly
• no more second network for reporting & fixing things
• universal service 🡪 Internet access for everyone
• single network 🡪 suitable for demanding services
• life-and-safety network
• The Internet – your life will depend on it…

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Backup

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Cost vs. distance

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Interstate switched access minutes

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Evolution of VoIP

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“amazing – the phone rings”

“does it do

call transfer?”

“How can I make it stop ringing?”

1996-2000

2000-2003

2004-2005

catching up

with the digital PBX

long-distance calling,

ca. 1930

going beyond

the black phone

2006-

“Can it really replace the phone system?”

replacing the

global phone system

Telephone Social Policies

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Phone numbers: hoarding

• How to prevent hoarding?
• By pricing
• DNS-like prices ($6.69 - $10.69/year for .com)
• takes $100M to buy up (212)…
• 1626: 60 guilders
• e.g., USF contribution proposals
• $8B/year, 750 M numbers 🡪 $10.60/year
• but significant trade-offs
• By demonstrated need
• see IP address assignment
• 1k blocks
• difficult to scale to individuals

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15c/month

100 million .COM

Robocalls – the enablers

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• Robocalling
• Cheap VoIP

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• Number spoofing

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• Cheap labor

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Copper loops

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DSL loop lengths

high-speed DSL

Copper loops 🡪 large-scale data competition (“unbundled network elements”)

Interconnection

• PSTN: general interconnection duty
• requires physical TDM trunks and switch ports
• VoIP:
• VPN-like arrangements
• MPLS
• general Internet
• may require fewer points-of-interconnect
• only relatively small number of IXPs
• transition to symmetric billing (cellular minutes, flat-rate) rather than caller-pays

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FCC USF/ICC reform

• Technical problem
• where and how
• just voice?
• Money problem
• who pays for what (conversion, transport, …)

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Federal Communications Commission FCC 11-161 �

42. IP-to-IP Interconnection. We recognize the importance of interconnection to competition and the associated consumer benefits.  We anticipate that the reforms we adopt will further promote the deployment and use of IP networks, and seek comment in the accompanying FNPRM regarding the policy framework for IP-to-IP interconnection.  We also make clear that even while our FNPRM is pending, we expect all carriers to negotiate in good faith in response to requests for IP-to-IP interconnection for the exchange of voice traffic

John Barnhill, GenBand

QoS is not just an Internet problem…

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NECA ExParte 05/21/2012

7400 test calls to 115 locations

Rural call completion

• Problems:
• manual error tracing
• complicated least-cost routing arrangements
• termination charge incentives
• Requirements for new PSTN:
• automated call flow tracing
• end-to-end call quality evaluation (🡪 MBA)

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