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VoIP peering – a snapshot

VoIP peering – a snapshot. Henning Schulzrinne w/Charles Shen Dept. of Computer Science Columbia University http://www.cs.columbia.edu/~hgs. Overview. Review: What is VoIP peering? Why VoIP peering? Scaling peering to millions of users Challenges for VoIP peering Beyond PSTN replacement

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VoIP peering – a snapshot

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  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 • sip:alice@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 sip:office@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  sip:12125551234@vsp.com;user=phone • resolve to neutral peering provider • +1 212 555 1234  sip:12125551234@peering.com;user=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. sip:bdr@internet2.edu mailto:bdr@internet2.edu sip:bobr_621@att.sbc.com 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  can’t 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

  17. 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@peering.com • peering provider does database (or internal ENUM) lookup

  19. 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

  20. 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" "D2P+SIP:fed" "!^.*$!http://sipxconnect.example.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

  24. Preliminary Black Box Test ENUM server Client 5 Client 1 Client 4 Client 2 Client 3

  25. Black-box Comparison Results • 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.

  26. 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) • 4257*260 • 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. sip:bdr@internet2.edu mailto:bdr@internet2.edu sip:bobr_621@att.sbc.com ISN in a Nutshell 4257*260 • 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 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

  35. 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/

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