Interoperation with the Circuit-Switched Telephone System

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1 1 Interoperation with the Circuit-Switched Telephone System ffl interoperation scenarios ffl mapping E.164 phone numbers to addresses ffl finding hop-off gateways: TR

2 2 Interoperation assumptions each phone needs to be reachable from the PSTN, without ffl dialing an! address possible IETF working group, ETSI Tiphon LDAP DNS multiple gateways from to PSTN ffl (almost) any gateway can call any! phone locate best / closest / cheapest attributes distributing and merging attributes! TR

3 3 DNS for number mapping ffl SCP may treat DNS as yet another database ffl use DNS NAPTR rewriting for local number portability (LNP) ffl find out which signaling services are supported Issues for any scheme: ffl rapid, secure, globally visible updates (e.g., for LNP) ffl ownership of addresses or neutral third party?

4 4 e164.arpa 1. convert to digits:! insert dots: reverse: append TLD: e164.arpa

5 5 Phone number rewriting ffl NAPTR (RFC 2168, being updated): originally for URN rewriting ffl flag: a for A RR, s for SRV RR e164.int. IN NAPTR "a" "sip+n2r" "" "sip:paf@swip.net". IN NAPTR "s" "potscall+n2r" "" _potscall._tcp.paf.swip IN NAPTR "a" "smtp+n2r" "" "mailto:paf@swip.net".

6 6 Local number portability ffl old number: , but has moved to a telcoy e164.int. IN NS ns.telcoy.net. ffl Telco Y allocates : $ORIGIN 6.4.e164.int. _potscall._tcp IN SRV

7 7 Translation from E.164 to S gets translated via Global Title Translation by the SCP finding DNS record: e164.int. IN SOA... IN NS... IN NAPTR "a" "sip+n2r" "" "sip:foobar@x.example.ne Then, call can only be made by S. The SCP routes the call to the correct gateway, using a mechanism currently not specified.

8 8 PSTN-to-Vo gateway location ffl currently, not specified use hop-off closest to destination or where doing number ffl translation? maybe get address via S OPTIONS and then determine best ffl hop-off point?

9 9 Gateway location protocol architecture ITAD 1 ITAD 2 GW 00 1 LS EU 01 0 TR ITAD 3

10 10 Gateway location protocol ffl inter-domain distribution of gateway properties ffl multiple signaling hops - aggregation! additional server aggregation of entries (e.g., Cologne/Bonn area , , ffl ,..! ) ffl but difficult in NANP: NJ has 201, 609, 732, 908, 973. ffl local calling areas may have a hundred exchange codes! ffl generally, use most specific match ffl policy filtering to restrict advertising prefixes

11 11 Gateway aggregation GW LS (49221, , 0.08DM) (4922, , 0.24 DM) Cologne (49, , 0.36 DM) Bornheim (49222, , 0.10DM) (4922, , 0.08 DM) Königswinter query S query S To: tel: S S Brühl voice data RTP Bonn Dortmund (49231, , 0.08 DM) (49, , 0.36 DM)

12 12 Attributes ß DestinationPhoneNumbers phone number prefix (+1201) NextHopSignalingServer direct H.323, S,...here AdvertisementPath BGP AS PATH, object path GatewayCapacity load balancing? SignalingProtocols H.323, S,... Pricing $/minute, setup charges, increment,... LastModifiedBy verifiable source of attribute NumSignalingHops min/max signaling (not media) hops AtomicAggregate aggregation indicator MultiExitDisc preference between multiple LS LS links

13 13 Attribute transitivity Optional: if not set, must be understood to process routing object; IndependentTransitive: propagate even if not understood; DependentTransitive: propagate if not understood, but don t touch next-hop; LastModifiedByFlag: covered by last-modified-by parameter. route objects always contain (DestinationPhoneNumbers, NextHopSignalingServer), where server is in ITAD of originating LS

14 14 Telephony Routing Information Protocol (TR) ffl from BGP-4: transport (TCP), message format (TLV) ffl from OSPF and SCSP: flooding ffl initially, exchange routing database when establishing connection ffl incremental updates (no refreshes) UPDATE advertised route signaling server price withdrawn route withdrawn route

15 15 TR LS peered with OPEN KEEPALIVE OPEN LS open handshake UPDATE KeepAlive (30s) NOTIFICATION error condition

16 16 Signaling: S to ISDN S INVITE 100 ISDN SETUP CALL PROC 183 PRACK 200 (PRACK) PROGress two way RTP 200 ACK one way voice CONNect CONNect ACK BYE 200 DISConnect RELease RELease COMplete

17 17 Signaling: S to ISUP NGW caller S ISUP INVITE sip: Trying IAM 183 Session Progress ACM duplex RTP media one way voice 200 OK ANM ACK BYE 200 OK REL RLC

18 18 References ffl P. Faltstrom, E.164 number and DNS, Internet Draft, October ffl A. Brown, E.164 Resolution, Internet Draft, October J. Rosenberg, H. Schulzrinne, Internet Telephony Gateway Location, ffl IEEE Infocom, San Francisco, March J. Rosenberg, H. Salama, M. Squire, Attributes for a Gateway Location ffl Protocol, Internet draft, June J. Rosenberg and H. Schulzrinne, A Framework for a Gateway Location ffl Protocol, Internet Draft, June J. Rosenberg, H. Salama, M. Squire, Telephony Routing Information ffl Protocol (TR), Internet Draft, October 1999.

TRIP, ENUM and Number Portability

TRIP, ENUM and Number Portability Nicklas Beijar Networking Laboratory, Helsinki University of Technology P.O. Box 3000, FIN-02015 HUT, Finland Nicklas.Beijar@hut.fi Abstract This paper describes the problem