1. ITU IP & Telecoms Interworking Workshop, Jan 2000 1 Interworking Between Public Data Networks and the Internet A numbering perspective ITU IP and Telecoms Interworking Workshop 25-27January 2000 Submitted by Peter Hicks Rapporteur ITU-T SG 7 Q3: Data Network Numbering Tel: + 613 9253 6308, Fax: + 613 9253 6777 email: p.hicks@trl.telstra.com.au

2. ITU IP & Telecoms Interworking Workshop, Jan 2000 2 Summary l This presentation examines numbering and addressing issues associated with the interworking of Public Data Networks and the Internet. l Interworking largely depends on being able to signal the called terminals number or address l This presentation does not attempt to solve all the technical or implementation problems but highlights the key issues that will either allow or prevent interworking to occur in the future.

3. ITU IP & Telecoms Interworking Workshop, Jan 2000 3 Some Issues l Key requirement: – Seamless interworking between terminals (DTEs) on Public Data Networks (X.25, FR or ATM) & terminals (also known as hosts) on IP routed networks or the Internet l PDN Protocols (X.25, Frame Relay, ATM) are connection oriented – PVC or SVC is established between the originating terminal and the destination terminal before protocol data units (user data) are transferred. l IP connectionless – no call set up phase exists l Is single-stage dialling possible or is two stage call setup required?

4. ITU IP & Telecoms Interworking Workshop, Jan 2000 4 Some Issues (cont) l Can PDN terminals be identified by mnemonic address such as j.blogs@acme.com.au l How will PDN terminals be identified – X.121 or E.164 number only – X.121 or E.164 number plus an IP address – IP address only – is dual numbering/addressing required? l What functionality is required in the gateway between PDNs and the Internet l Where is the gateway located l What QoS does the end-to-end connection achieve (This is not a numbering issue)

5. ITU IP & Telecoms Interworking Workshop, Jan 2000 5 Numbering of Public Data Networks l Frame Relay networks numbered under either X.121 or E.164 - identifies DTE point of attachment. l ATM networks numbered under E.164 - also can use NSAP formats for ATM end system addresses l The leading digits of an X.121 and an E.164 number identify the country where the network is located l Network Identification – within an X.121 number, the Data Network Identification Code (DNIC) uniquely identifies a specific network – E.164 numbers generally do not have a network ID code built in to the number; (flat number structure) – for networks numbered under E.164, a network ID code as per Rec X.125 may be carried in a specific field of the signalling protocol (not currently used for call set up)

6. ITU IP & Telecoms Interworking Workshop, Jan 2000 6 Call Set-up for Frame Relay & ATM l Call Setup message identifies the called terminal l Called terminals point of attachment carried in the called party information element (as per X.36, X.76 or Q.2931 signalling) l For Frame Relay the called terminal identified by: – X.121 or E.164 number or NSAP address l For ATM the called terminal may be identified by: – E.164 number or NSAP address – only certain NSAP formats supported (embedded E.164, ICD, DCC) l X.25 allows the called terminal to be identified by an alternative address which can be an IP address, a mnemonic address or an NSAP

7. ITU IP & Telecoms Interworking Workshop, Jan 2000 7 Use of NSAP to identify called terminal l NSAP Formats (see Rec X.213 Annex A) include: – embedded X.121 number – embedded E.164 number – ICD (International Code Designator) Format – DCC (Data Country Code) Format – embedded IP address l Hence capability exists to signal an IP address l However use of NSAPs to identify the called terminal requires additional intelligence in the switch to which the calling terminal is connected – address resolution entity required – requires a large data base

8. ITU IP & Telecoms Interworking Workshop, Jan 2000 8 General Interworking Scenario Public Data Network (X.25, FR, ATM ) INTERNET IWF Point of attachment to public data network defined by X.121 or E.164 number Terminal identified by IP address Term A Term B

9. ITU IP & Telecoms Interworking Workshop, Jan 2000 9 l Requirement is for Terminal A to be able to send data to Terminal B and for Terminal B to be able to send data to Terminal A at any time l initiated by either party l Terminal A identified by X.121 or E.164 number l Terminal B identified by an IP address l Does Terminal A need to have an IP Address? l What protocol stack does Terminal A use? l What functionality is required in the IWF – address resolution or protocol translation Notes on General Interworking Scenario General Interworking Scenario

10. ITU IP & Telecoms Interworking Workshop, Jan 2000 10 Interworking via an Internet Service Provider Public Data Network ( X.25, FR or ATM ) INTERNET Terminal B identified only by IP address Internet Service Provider FR or ATM Connection FR, ATM or leased line Connection to Internet Backbone Term A Term B Edge Router Edge Router Edge Router Point of attachment to public data network defined by X.121 or E.164 number

11. ITU IP & Telecoms Interworking Workshop, Jan 2000 11 Notes on Interworking via an Internet Service Provider (#1) Notes on Interworking via an Internet Service Provider (#1) Case A: Terminal A sending data to Terminal B l Terminal A must subscribe to the service provided by an Internet Service Provider l Terminal A sets up SVC or PVC connection to Internet Service Provider. – Edge router of the ISP identified by X.121 number – IP address is allocated to terminal A by the ISP » Can this address be permanent or use made of DHCP? l IP packets encapsulated as Frame Relay or ATM user Data and sent to the Internet Service Provider l Internet Service Provider routes IP packets into the Internet for forwarding to Terminal B

12. ITU IP & Telecoms Interworking Workshop, Jan 2000 12 Notes on Interworking via an Internet Service Provider (#2) Case B: Terminal B sending data to Terminal A l What happens if Terminal As connection to the Internet Service Provider is inactive l What is the IP address for Terminal A l How does Terminal B know what Terminal As IP address is - can use be made of Inverse ARP? l How does the Internet know the location of terminal A – if Terminal B receives an IP packet from Terminal A, does this imply that the reverse path and IP Address for Terminal A is known

13. ITU IP & Telecoms Interworking Workshop, Jan 2000 13 Whats required for efficient routing from the IP network to a terminal on the PDN? l How is the PDN terminal identified – Does the terminal have a dual address ie, X.121 or E.164 number plus an IP address – what mechanisms are there available for carrying an X.121 or E.164 number within the address block of an IP packet – what extensions in IP addressing are needed to signal an X.121 or E.164 number l What additional functionality is required in gateway or border routers that allows identification of the PDN

14. ITU IP & Telecoms Interworking Workshop, Jan 2000 14 INTERNETINTERNET Interworking Gateway Routers Network DNIC 3134 Network DNIC 2288 Network DNIC 5052 Network DNIC 3139 IPv6 Network Layer X.121= 3134 908 949 5369 X.121=3134 908080136 X.121=22889089495369 X.121= 2288 914 308 3270 X.121=505292536308 X.121= 505291556144 In order that IP data packets can be efficiently routed to end system terminals connected to public data networks, the Gateway Routers connected to the various public data networks could advertise the DNIC to the border routers on the Internet: e.g. DNIC = 2288, The gateway routers would then need to establish the necessary connections to the PDN terminals based on the full X.121 number. PDN - X.25 or Frame Relay IPv6 Network Layer Example showing interworking via gateway routers if the IP terminal could signal an X.121 Address X.121= 313991556144 Edge or Border Routers X.121=3134 908087788 IP Terminals

15. ITU IP & Telecoms Interworking Workshop, Jan 2000 15 Is there a requirement for service Interworking ? PDN / IP Service Interworking PDNIP IWF PDN DTE IP Terminal The IP Terminal has no knowledge that it is talking to a PDN DTE. PDU on PDN encapsulation PDU on IP encapsulation The PDN Terminal has no knowledge that it is talking to a IP Terminal

16. ITU IP & Telecoms Interworking Workshop, Jan 2000 16 Typical Scenario for Service Interworking Video IP FR / ATM IWF Central Host Video Conference Server IP terminal LAN R R Private Network FR /ATM terminal FR /ATM terminal

17. ITU IP & Telecoms Interworking Workshop, Jan 2000 17 Service Interworking via a Gateway Service Interworking via a Gateway Public Data Network ( X.25, FR or ATM ) INTERNET Terminal B identified only by IP address Service Interworking Gateway FR or ATM Connection FR, ATM or leased line Connection to Internet Backbone Term A Term B Edge Router Edge Router Point of attachment to public data network defined by X.121 or E.164 number Protocol translation & encapsulation

18. ITU IP & Telecoms Interworking Workshop, Jan 2000 18 FR or ATM / IP Interworking Protocol Stacks Physical IP IP Terminal Application Interworking Gateway FR or ATM Data PDU Voice PDU RFC Encap Payload IP Physical ? Implemt depend FR or ATM UNI FR/ATM DTE FR or ATM Data PDU Voice PDU RFC Encap Application Physical ? Implemt depend

19. ITU IP & Telecoms Interworking Workshop, Jan 2000 19 Conclusions l The necessary code points within the FR signalling protocols enable a calling terminal on the PDN to identify an IP terminal (by use of an NSAP) in the call setup message. – extensions required in ATM signalling (Rec Q.2931) to allow NSAP (embedded IP format ) to be supported – features such as X.25 alternative addressing would enable the called party to be identified by a mnemonic address such j.blogs@acme.com.au » extensions required to FR and ATM signalling protocols » required to facilitate interworking as demonstrated in the use email today l Two stage interworking from the PDN into the Internet is achievable today

20. ITU IP & Telecoms Interworking Workshop, Jan 2000 20 Conclusions (cont) l Interworking from the IP world to the PDN appears to be constrained by the fact that an IP packet can not readily carry an X.121 or E.164 number to identify the destination terminal on the PDN l will require extensions in IP addressing or functionality to signal an X.121 or E.164 number – No such functionality in IPv4 – May be able to use IPV6 address extensions options to carry an OSI NSAP which contained the embedded X.121 or E.164 number