TRIP, ENUM and Number Portability

1. TRIP, ENUM and Number Portability Nicklas Beijar Nicklas.Beijar@hut.fi

2. Contents • TRIP, ENUM and Number Portability • Current situation • Problem description • TRIP • ENUM • Scenarios • Number portability • Conclusions

3. Current situation • Terminal location • End terminal located with signaling protocol and DNS • ”user@host”, ”user@server” • Mapping from name (E.164, URL, e-mail) to address (IP address) • Mapping stored in location server (gatekeeper, signaling server) • Manually configured or obtained through registration • Directory servers (ULS, ILS) • E.164 numbers selected for IP Telephony by TIPHON • Can be entered with numeric keypad • Users don’t need to know if the receiver is a IP or PSTN subscriber

4. Current situation • Gateway location • Similar to terminal location, number@gateway • Gateway selected manually by caller or by signaling server • New selection if gateway is unavailable • Number portability • Change service provider, location or service type without changing • telephone number • IP Telephony -> number portability between PSTN and IP • Currently available in the PSTN only • Mapping from directory number to routing number (or routing prefix) • Routing number has hierarchy • Mapping performed by Intelligent Network (IN)

5. Problems • Given a phone number corresponding to a specific host on the IP network, determine the IP address of the host. •  Terminal location problem • Given a phone number corresponding to a terminal on the PSTN, determine the IP address of a gateway capable of completing calls to that phone. Gateway location problem

6. Problems • Mappings are not distributed between signaling servers and • location servers • E.164 numbers cannot be used globally • Users must select gateway manually • Which gateways are available and suitable for this call?

7. Gateway selection criteria • Location • Business relationships • Policies • Features • Signaling protocol • Codec • Service • Capacity

8. TRIP • Telephony Routing over IP • IETF protocol, still at draft stage • Distributes routing information between location servers • Information about gateways and the numbers reachable • through them • Routes to gateways and signaling servers • Modeled after BGP-4 • Gateway selection driven by policies • Interdomain protocol between Internet Telephony Administrative • Domains (ITAD) • Interdomain synchronization based on SCSP and OSPF • Information transported as attributes of the UPDATE message • Expandable

9. Name Description Withdrawn routes List of telephone numbers that are no longer available. Reachable routes List of reachable telephone numbers. Next hop server The next signaling server on the path towards the destination. Advertisement path The path that the route advertisement has traveled. Routed path The path that the signaling messages will travel. Atomic aggregate Indicates that the signaling may traverse ITADs not listed in the routed path attribute. Local preference The intra-domain preference of the location server. Multi exit disc The inter-domain preference of the route if several links are used. Communities For grouping destinations in groups with similar properties. ITAD topology For advertising the ITAD topology to other servers in the same ITAD. Authentication Authentication of selected attributes. TRIP attributes

10. Structure of a TRIP node

11. TRIP for gateways • TRIP-GW • Exports routing information from gateways to location server • New attributes • Circuit capacity • DSP capacity • Lightweight • Send-only mode • No databases • Compatibible with TRIP

12. ENUM • tElephone NUmbering Mapping • RFC 2916 • Maps E.164 numbers into Uniform Resource Identifiers (URI) • The URIs represent different ways to contact a host • SIP, H.323, TEL, email, ... • Uses the Domain Name System (DNS) • E.164 number rewritten as a domain name: +358-9-4515303 -> 3.0.3.5.1.5.4.9.8.5.3.e164.arpa

13. Example NAPTR records $ORIGIN 3.0.3.5.1.5.4.9.8.5.3.e164.arpa. IN NAPTR 10 10 “u” “sip+E2U” “!^.*$!sip:nbeijar@tct.hut.fi!” . IN NAPTR 100 10 “u” “mailto+E2U” “!^.*$!mailto:nbeijar@tct.hut.fi!” . IN NAPTR 100 10 “u” “tel+E2U” “!^.*$!tel:+35894515303!” .

14. Example reachme service Sample top level delegations from ITU: 3.3.e164.arpa IN NS ns.FR.phone.net. ;France 8.5.3.e164.arpa IN NS ns.FI.phone.net. ;Finland Sample national delegations: 5.4.9.8.5.3.e164.arpa. IN NS ns.ServiceProviderX.net. Sample service provider’s configuration: 1.5.4.9.8.5.2.e164.arpa. DNAME 1.5.4.9.8.5.2.ns.hut.fi. Sample service registrar configuration: *.1.5.4.9.8.5.2.ns.hut.fi. IN NAPTR 100 10 ”u” ”ldap+E2U”\ “$!ldap://ldap.hut.fi/cn=\1!” .

15. Call from IP-based network to PSTN Voice path Voice path ENUM query DNS DNS LS Location server query (LDAP) IP IP - - based based SIP SIP SIP Client SIP Client Network Network Server Server POTS POTS Gateway Gateway PSTN PSTN Phone Phone

16. Call from PSTN to IP-based network POTS POTS Gateway Gateway PSTN PSTN Phone Phone IP IP - - based based SIP SIP SIP Client SIP Client Network Network Server Server DNS DNS Voice path Voice path ENUM query Server Server

17. Number portability • Scenarios for hybrid PSTN-IP networks: • The number moves within the PSTN. • The number moves between PSTN and IP. • The number moves within the IP network. • ENUM allows the mapping to be modified at different levels • Another gateway may be more suitable •  In most cases, information in ALL protocols must be updated

18. Conclusions • TRIP solves the gateway location problem • Distributes routing information between location servers • ENUM solves the terminal location problem • Provides mapping between names to addresses • E.164 numbers • In the PSTN, number portability implemented with IN • Number portability can be implemented with TRIP and ENUM • Still missing • Automatic updating of infomation between TRIP, ENUM and IN • Gateway location for the PSTN  CTRIP