VoIP%20peering%20

1
VoIP peering a snapshot

• Henning Schulzrinne
• w/Charles Shen
• Dept. of Computer Science
• Columbia University
• http//www.cs.columbia.edu/hgs

2
Overview

• Review What is VoIP peering?
• Why VoIP peering?
• Scaling peering to millions of users
• Challenges for VoIP peering
• Beyond PSTN replacement
• Resources

3
What is VoIP peering?

• Definitions from IETF SPEERMINT Working Group
• Peering refers to the negotiation of
  reciprocal interconnection arrangements,
  settlement-free or otherwise, between
  operationally independent service providers.
  (draft-ietf-speermint-res-and-terminology-01)
• Layer 5 peering refers to interconnection of two
  service providers for the purposes of exchanging
  SIP signaling. Note that in the layer 5 peering
  case, there is no requirement for any intervening
  "Layer 5 Transit Network". Each service provider
  is expected to interconnect directly with other
  service providers, although a service provider is
  allowed to interconnect through another domain
  (ex a federation) to act on its behalf.
  (SPEERMINT, IETF 65)
• Cable Labs
• The notion of IP Service Peering (and VoIP
  Peering) extends the relationship between
  network operators above the IP layer, by handling
  the IP-based services and applications that can
  be exchanged.

4
Why VoIP peering?

• Near-term motivations
• avoid PSTN hops between VoIP service providers
• codify provider trust relationships
• bridge wait until global ENUM
• Longer term motivations
• no PSTN in the middle ?
• advanced signaling services
• no transcoding ? better audio quality
• wideband audio codecs
• video, IM,
• possibly increase in trust
• smaller number of players ? spam, spit ?

5
Why is VoIP peering needed?

• Non-reasons
• SIP providers can talk directly to each other if
  SIP URIs are available
• sipalice_at_example.com ? look up SIP server for
  example.com (NAPTR, SRV) and connect
• email-like ? no email peering
• L3 probably best to avoid triangle routing
• Reasons
• E.164 numbering who serves the customer with 1
  212 555 1234?
• absence of global ENUM ?
• interoperability
• billing

6
Session interconnect
E.164 number
peer discovery
ENUM lookup of NAPTR in DNS
SIP URI
aka call routing data (CRD) ? derived from ENUM
record
service location (lookup of NAPTR and SRV) in DNS
host name
addressing and session establishment
lookup of A and AAAA in DNS
IP address
routing protocols, ARP,
MAC address
7
Peering evolution
VoIP Service Providers interconnect via PSTN
using E.164 numbers for addressing
VSP
VSP
VSP
VSP
VSP
PSTN Plane
4315056416
Otmar Lendl, March 2006 (SPEERMINT)
8
Messy reality
Private Interconnection Network
Private Interconnection Network
sipoffice_at_enum.at
VSP
VSP
VSP
VSP
VSP
Public Internet
Closed SIP federation
PSTN Plane
Otmar Lendl, March 2006 (SPEERMINT)
9
Example Cable operators

• MSOs want to avoid PSTN traversal
• Call Management Server Signaling (CMSS) SIP

Jean-François Mulé, IETF 63
10
Peering decomposed model
domain A
domain B
draft-penno-message-flows-02
11
Peering collapsed model
??
??
B2BUA
domain A
domain B
draft-penno-message-flows-02
12
Peering authorization
P1
P2
INVITE

• On-demand
• email model
• as needed when exchanging SIP messages
• usually, mutual TLS authentication
• proposed SUBSCRIBE/NOTIFY key exchange
• Static
• established ahead of signaling
• e.g., TLS or IPsec
• proposed SUBSCRIBE/NOTIFY key exchange

100 Trying
SUBSCRIBE w/PeerAuth
401 Unauthorized
SUBSCRIBE w/auth
202 Accepted
NOTIFY w/P2key
INVITE
401 Unauthorized
INVITE P2Key
INVITE
100 Trying
draft-penno-message-flows-02
13
Role of ENUM in peering

• Core service look up provider for E.164 number
• ENUM models
• Public ENUM e164.arpa
• Private ENUM limited access to DNS records
  (e.g., by VPN)
• Carrier ENUM
• Options
• resolve to subscriber SIP URI
• 1 212 555 1234 ? sip12125551234_at_vsp.comuserpho
  ne
• resolve to neutral peering provider
• 1 212 555 1234 ? sip12125551234_at_peering.comuser
  phone
• peering.com proxy translates to actual provider
• resolve to carrier ENUM DNS server
• 1 212 555 1234 ? enum.vsp.com ? NAPTR query on
  enum.vsp.com
• service provider identifier (SPID)
• 1 212 555 1234 ? NXXX

14
ENUM in a Nutshell
1-734-913-4257

• Take an E.164 number
• Convert it to FQDN
• Query DNS for NAPTRs
• Apply resulting regexs to get list of URIs

7.5.2.4.3.1.9.4.3.7.1.e164.arpa.
e164.arpa.
1.e164.arpa.
4.3.7.1e164.arpa.
x.x.x.1.e164.arpa.
Ben Teitelbaum, John Todd, Dennis Baron ISN
Numbers Fast, Free, and Forever Yours March 16,
2006 Spring VON, San Jose, CA
15
Who serves an E.164 number?

• Find point of interconnection (PoI) for given
  E.164 number
• Peering provider can answer question locally
• Likely to have dozens of such peering exchanges
  and federations
• each provider will be a member of some subset of
  these
• Kludge originating provider asks all its peering
  providers in parallel
• via DNS ENUM lookup
• Possibly federate peering providers
• flood number information, pointing to peering
  ENUM
• multiple resolutions ? cant be DNS

16
Carrier (infrastructure) ENUM

• User ENUM
• entity or person having the right-to-use of an
  E.164 number has the sole discretion about the
  content of the associated domain and thus the
  zone content (draft-haberler-carrier-enum-02)
• end user as registrant
• Carrier (now, infrastructure) ENUM
• "carrier of record" (COR) as registrant
• Proposal branch under e164.arpa
• 4.9.7.1.carrier.e164.arpa or
• 4.9.7.carrier.1.e164.arpa

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Carrier ENUM

• COR registrant
• block holder allocated by National Regulatory
  Authority (NRA)
• "International Networks" (882) or "Universal
  Personal Telecommunications (UPT)" (878)
  allocated by ITU
• recipient of a port (service provider)
• has been contracted by a user to route a number
  assigned to a user directly (without COR being in
  the number assignment path)
• corporate network numbers
• 800/900 type numbers in many countries
• Include all E.164 numbers in block
• avoid ability to detect listed vs. unlisted
  numbers

18
Provider hiding

• Some providers worry about exposing their
  identity to competitors
• competitors could target customers for marketing
  efforts
• unclear if more than theoretical issue
• Solution
• send calls to peering provider SIP proxy, not
  directly to VSP proxy
• ENUM 12125551234_at_peering.com
• peering provider does database (or internal ENUM)
  lookup

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Challenge provisioning ENUM entries

• Dynamic DNS not suitable security, scaling
• Options
• bulk upload via ftp, HTTP,
• EPP (Extensible Provisioning Protocol) RFC 3730
• XML-based protocol designed originally for domain
  number management

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SPEERMINT discussion federations

• A federation is a group of VoIP service providers
  / enterprises which
• agree to receive calls from each other via SIP
• agree on a set of administrative rules for such
  calls (settlement, abuse-handling, ...), and
• agree on specific rules for the technical details
  of the interconnection
• Federations have a unique identifier
• TLS-based
• Public Internet, SIP over TLS, federation acts as
  X.509 Certification Authority.
• Private network
• Federation builds its own network members
  connect directly over this network.
• SIP hubs / transit networks
• Calls are routed via a central SIP proxy

Otmar Lendl, The Domain Policy DDDS
Application, IETF 65, March 2006
21
Domain Policy DDDS basics

• The domain is the key to the destination policy
• Use the DNS as rule store
• No special translation rules necessary
• Infrastructure is in place
• Example
• example.com. IN NAPTR 10 50 "U"
  "D2PSIPfed" "!.!http//sipxconnect.examp
  le.org/!" .
• Regarding SIP, example.com is a member of the
  federation identified by this URI.
• Non-terminal NAPTR for customer domains referring
  to provider domains
• Protocol agnostic
• SIP is just a special case

Otmar Lendl, The Domain Policy DDDS
Application, IETF 65, March 2006
22
Longer-term opportunities for peering

• Enterprise trunk backup management
• PSTN as primary, VoIP as backup (or vice versa)
• Spam/SPIT prevention
• accountable carriers
• trustable user identification (caller ID)
• exchange of abuse information
• Billing and settlements
• if per-call billing

23
ENUM performance

• Busy hour traffic estimate
• 0.1 Erlang ? 2 calls/hour/user
• 100 mio users ? roughly 55,000 calls/second ?
  lookup rate
• Post-dial delay bounds few seconds
• includes signaling latency
• DNS unlikely to be a significant contributor
  (except if packet loss)
• DNS server platform
• OS Linux version 2.6.11
• 1 or 2 Intel Pentium 4 CPU 3.00GHz, 1 GB memory
• DNS servers
• BIND
• PowerDNS (PDNS)
• Open Source Authoritative Nameserver
• Used by 50 of .de and 20 rest of the world,
  including e164.org.
• Runs on Linux, FreeBSD, NetBSD, OpenBSD, Solaris
• Serves data from MySQL, PostgreSQL, LDAP, BIND
  zone files,
• Nominum ANS

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Preliminary Black Box Test
ENUM server
Client 5
Client 1
Client 4
Client 2
Client 3
25
Black-box Comparison Results
IRT BIND 9.3.2 Nominum BIND 9.3.0 IRT PDNS BIND Nominum PDNS BIND IRT PDNS MySQL Nominum PDNS MySQL Nominum ANS
10 M Records Load Pass Pass Pass Fail Pass Not Tested Pass
Queries per Second 521 143 9,208 N/A 2,051 Not Tested 43,135
Average Latency (s) 0.190 0.618 0.011 N/A 0.048 Not Tested 0.0016

• All columns denoted as Nominum are from the
  Nominum white paper ENUM Scalability and
  Performance Testing.
• The last column, Nominum ANS is tested with 200M
  records, all the rest are tested with 10M
  records.
• PDNS test uses its default settings.

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PDNS response time record exists
27
PDNS Throughput record exists
28
Throughput PDNS and caching
29
Throughput BIND
30
Throughput - ANS
31
ITAD Subscriber Numbers (ISN)

• 4257260
• ITADs
• Defined by Telephony Routing over IP (TRIP)
  RFC3219
• Globally unique
• Lots of them (256 through 232-1)
• IANA is already set up to allocate
• ISN resolution works just like ENUM

Internet Telephony Administrative Domain (ITAD)
locallyassigned
Ben Teitelbaum et al, March 2006
32
ISN in a Nutshell
4257260

• Take an ISN
• Convert it to FQDN
• Query DNS for NAPTRs
• Apply resulting regexs to get list of URIs

7.5.2.4.260.freenum.org.
freenum.org.
260.freenum.org.
Note We are working to ensure that the ISN root
zone will be administered on behalf of the ISN
user community by a neutral, non-profit
organization. Following the trial, the root may
or may not be freenum.org.
Ben Teitelbaum, John Todd, Dennis Baron ISN
Numbers Fast, Free, and Forever Yours March 16,
2006 Spring VON, San Jose, CA
33
ISN vs ENUM vs SIP AOR
ISN ENUM SIP AOR
Example 7031260 1-734-352-7031 ben_at_internet2.edu
Familiarity Huh? Phone numbers Email address
Delegating Authority IANA ITU, national government, ICANN, TLD registrars
Address Structure localdomain Hierarchical / geographical local_at_domain
Portability With domain owners cooperation Varies by country??? With domain owners cooperation
Fragmentation One space Public ENUM multiple private ENUMs One space
Ben Teitelbaum, John Todd, Dennis Baron ISN
Numbers Fast, Free, and Forever Yours March 16,
2006 Spring VON, San Jose, CA
34
Conclusion

• Peering as crucial next step for large-scale VoIP
• weaning off the PSTN
• needed to get beyond black-phone service
• ENUM as core peering service
• needed as long as phone numbers are in use
• slow transition from private to public ENUM
• Peering is ENUM
• security associations
• privacy protections (for carrier and users)
• billing and settlements?
• Peering issues
• provisioning of E.164 records
• which peer?
• Need for high-performance service architecture

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Resources

• ENUM RFC 3761
• carrier ENUM draft-haberler-carrier-enum-02
• tel URIs RFC 3966
• IETF SPEERMINT working group
• definitions and terminology draft-ietfs-speermint
  -reqs-and-terminology-01
• message flows draft-penno-message-flows-02
• CableLabs VoIP Peering RFI
• GSMA GRX/IPX Requirements
• ECMA/TISPAN Next-Gen Corporate-Core
  Interconnection Requirements
• SIP Forum IP PBX / Service Provider
  Interoperability
• ISNs http//www.internet2.edu/sip.edu/isn/