ipw-13

8/3/2019 ipw-13

1/20

ITU IP & Telecoms Interworking Workshop, Jan 2000 1

Interworking Between Public DataInterworking Between Public Data

Networks and the InternetNetworks and the Internet

A numbering perspectiveA numbering perspective

ITU IP and Telecoms Interworking Workshop25-27January 2000

Submitted by Peter Hicks

Rapporteur ITU-T SG 7 Q3: Data Network Numbering

Tel: + 613 9253 6308, Fax: + 613 9253 6777

email: [email protected]

8/3/2019 ipw-13

2/20


SummarySummary

This presentation examines numbering andaddressing issues associated with the interworking ofPublic Data Networks and the Internet.

Interworking largely depends on being able to signalthe called terminals number or address

This presentation does not attempt to solve all thetechnical or implementation problems but highlightsthe key issues that will either allow or preventinterworking to occur in the future.

8/3/2019 ipw-13

3/20


Some IssuesSome Issues

Key requirement: Seamless interworking between terminals (DTEs) on

Public Data Networks (X.25, FR or ATM) & terminals (alsoknown as hosts) on IP routed networks or the Internet

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 dataunits (user data) are transferred.

IP connectionless

no call set up phase exists

Is single-stage dialling possible or is two stagecall setup required?

8/3/2019 ipw-13

4/20


Some Issues (cont)Some Issues (cont)

Can PDN terminals be identified by mnemonicaddress such as [email protected]

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?

What functionality is required in the gateway

between PDNs and the Internet Where is the gateway located

What QoS does the end-to-end connectionachieve (This is not a numbering issue)

8/3/2019 ipw-13

5/20


Numbering of Public Data NetworksNumbering of Public Data Networks Frame Relay networks numbered under either X.121 or

E.164 - identifies DTE point of attachment.

ATM networks numbered under E.164

- also can use NSAP formats for ATM end system addresses

The leading digits of an X.121 and an E.164 numberidentify the country where the network is located

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 builtin to the number; (flat number structure)

for networks numbered under E.164, a network ID code as perRec X.125 may be carried in a specific field of the signallingprotocol (not currently used for call set up)

8/3/2019 ipw-13

6/20


Call SetCall Set--up for Frame Relay & ATMup for Frame Relay & ATM

Call Setup message identifies the called terminal Called terminals point of attachment carried in the

called party information element (as per X.36, X.76 orQ.2931 signalling)

For Frame Relay the called terminal identified by:

X.121 or E.164 number or NSAP address

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)

X.25 allows the called terminal to be identified by analternative address which can be an IP address, amnemonic address or an NSAP

8/3/2019 ipw-13

7/20


Use of NSAP to identify called terminalUse of NSAP to identify called terminal

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

Hence capability exists to signal an IP address

However use of NSAPs to identify the called terminalrequires additional intelligence in the switch to whichthe calling terminal is connected

address resolution entity required

requires a large data base

8/3/2019 ipw-13

8/20


General Interworking ScenarioGeneral Interworking Scenario

Public Data Network

(X.25, FR, ATM)

INTERNETIWF

Point of attachment to public data network

defined by X.121 or E.164 number

Terminal identified by IP address

Term A

Term B

8/3/2019 ipw-13

9/20


Requirement is for Terminal A to be able to senddata to Terminal B and for Terminal B to be able tosend data to Terminal A at any time

initiated by either party Terminal A identified by X.121 or E.164 number

Terminal B identified by an IP address

Does Terminal A need to have an IP Address?

What protocol stack does Terminal A use?

What functionality is required in the IWF

address resolution or protocol translation

Notes onNotes onGeneral Interworking ScenarioGeneral Interworking Scenario

8/3/2019 ipw-13

10/20


Interworking via anInterworking via anInternet Service ProviderInternet 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

8/3/2019 ipw-13

11/20


Notes on Interworking via anNotes on Interworking via anInternet Service Provider (#1)Internet Service Provider (#1)

Case A: Terminal A sending data to Terminal B

Terminal A must subscribe to the service provided by anInternet Service Provider

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?

IP packets encapsulated as Frame Relay or ATM userData and sent to the Internet Service Provider

Internet Service Provider routes IP packets into theInternet for forwarding to Terminal B

8/3/2019 ipw-13

12/20


Notes on Interworking via anNotes on Interworking via anInternet Service Provider (#2)Internet Service Provider (#2)

Case B: Terminal B sending data to Terminal A

What happens if Terminal As connection to the InternetService Provider is inactive

What is the IP address for Terminal A How does Terminal B know what Terminal As IP

address is - can use be made of Inverse ARP?

How does the Internet know the location of terminal A

if Terminal B receives an IP packet from Terminal A, doesthis imply that the reverse path and IP Address for Terminal

A is known

8/3/2019 ipw-13

13/20


Whats required for efficient routingWhats required for efficient routing

from the IP network to a terminal onfrom the IP network to a terminal onthe PDN?the PDN?

How is the PDN terminal identified

Does the terminal have a dual address ie, X.121 or E.164number plus an IP address

what mechanisms are there available for carrying anX.121 or E.164 number within the address block of an IPpacket

what extensions in IP addressing are needed to signalan X.121 or E.164 number

What additional functionality is required in gateway orborder routers that allows identification of the PDN

8/3/2019 ipw-13

14/20


I

N

T

E

R

N

E

T

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 routersExample showing interworking via gateway routers

if the IP terminal could signal an X.121 Addressif the IP terminal could signal an X.121 Address

X.121= 313991556144

Edge or Border Routers

X.121=3134 908087788

IP Terminals

8/3/2019 ipw-13

15/20


Is there a requirement for serviceIs there a requirement for serviceInterworking ?Interworking ?

PDN / IP Service Interworking

PDN IPIWFPDN

DTEIP

Terminal

The IP Terminal has no

knowledge that it is

talking to a PDN DTE.

PDU on PDN

encapsulationPDU on IP

encapsulation

The PDN Terminal has no

knowledge that it is

talking to a IP Terminal

8/3/2019 ipw-13

16/20


Typical ScenarioTypical Scenario

for Service Interworkingfor Service Interworking

Video

IPFR / ATM

IWFCentral

Host

VideoConference

ServerIP

terminal

LAN

R

LAN R

Private

NetworkFR /ATM

terminal

FR /ATM

terminal

8/3/2019 ipw-13

17/20


Service Interworking via a GatewayService Interworking via a Gateway

Public Data Network

( X.25, FR or ATM)

INTERNET

Terminal B identified

only by IP addressService Interworking

Gateway

FR or ATMConnection

FR, ATM or leased line

Connection toInternet Backbone

Term A

Term BEdge

Router

Edge

Router

Point of attachment to public data networkdefined by X.121 or E.164 number

Protocol translation

&

encapsulation

8/3/2019 ipw-13

18/20


FR or ATM / IP InterworkingFR or ATM / IP InterworkingProtocol StacksProtocol Stacks

Physical

IP

IP Terminal

Application

Interworking

Gateway

FR

or

ATM

Data PDU

Voice PDURFC Encap

Payload

IP

Physical Physical

?

Implemt

depend

FR

or ATM

UNI

FR/ATM DTE

FR

or

ATM

Data PDU

Voice PDURFC Encap

Application

Physical

?

Implemt

depend

8/3/2019 ipw-13

19/20


ConclusionsConclusions

The necessary code points within the FR signalling protocolsenable a calling terminal on the PDN to identify an IPterminal (by use of an NSAP) in the call setup message.

extensions required in ATM signalling (Rec Q.2931) to allowNSAP (embedded IP format ) to be supported

features such as X.25 alternative addressing would enablethe called party to be identified by a mnemonic address such

[email protected]

extensions required to FR and ATM signalling protocols

required to facilitate interworking as demonstrated in the use email

today

Two stage interworking from the PDN into the Internet isachievable today

8/3/2019 ipw-13

20/20


Conclusions (cont)Conclusions (cont)

Interworking from the IP world to the PDN appears to beconstrained by the fact that an IP packet can not readilycarry an X.121 or E.164 number to identify thedestination terminal on the PDN

will require extensions in IP addressing orfunctionality 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.121or E.164 number

Documents

ipw-13