Telecommunications and Internet Protocol Harmonization Over Networks (TIPHON); The procedure for determining IP addresses for routeing packets on interconnected IP networks that support public telephony

In telecommunication systems and therefore also in IP systems E.164 numbers (or dialled numbers related to E.164) are used by end users to identify the destination of a call.  In IP systems, when an end user is attached to a terminal, the E.164 name of this end user is temporarily associated with the IP address (transport address) of the terminal (endpoint).  Private numbering schemes use similar arrangements. This technical report defines the requirements for finding destinations (IP addresses of endpoints) on interconnected IP networks (systems) for calls originating on or transiting via IP telephony networks.  The final destination of the call may be either the IP network itself or on the SCN.  In this case the IP address needs to identify the POI to the SCN. Although the TR defines requirements for E.164 numbers, the same principles could be applied to any new naming system that might be introduced for telephony. The TR deals with obtaining IP-address (or Contact Addresses) for routing Call and Service Control Messages (including database queries) and Media Stream Packets. The TR covers the requirements for calls to all types of number structures within E.164, national and private networks and includes the support of number portability, mobility and roaming.

Harmonizacija telekomunikacij in internetnega protokola prek omrežij (TIPHON) - Postopki za določanje naslovov IP za usmerjanje paketov po medsebojno povezanih omrežjih IP za podporo javne telefonije

General Information

Status
Published
Publication Date
31-Mar-2004
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
01-Apr-2004
Due Date
01-Apr-2004
Completion Date
01-Apr-2004

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SLOVENSKI STANDARD
SIST-TP TR 101 326 V2.0.0:2004
01-april-2004
+DUPRQL]DFLMDWHOHNRPXQLNDFLMLQLQWHUQHWQHJDSURWRNRODSUHNRPUHåLM 7,3+21 
3RVWRSNL]DGRORþDQMHQDVORYRY,3]DXVPHUMDQMHSDNHWRYSRPHGVHERMQR
SRYH]DQLKRPUHåMLK,3]DSRGSRURMDYQHWHOHIRQLMH

Telecommunications and Internet Protocol Harmonization Over Networks (TIPHON); The

procedure for determining IP addresses for routeing packets on interconnected IP
networks that support public telephony
Ta slovenski standard je istoveten z: TR 101 326 Version 2.0.0
ICS:
33.020 Telekomunikacije na splošno Telecommunications in
general
SIST-TP TR 101 326 V2.0.0:2004 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST-TP TR 101 326 V2.0.0:2004
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SIST-TP TR 101 326 V2.0.0:2004
ETSI TR 101 326 V2.0.0 (2002-02)
Technical Report
Telecommunications and Internet Protocol
Harmonization Over Networks (TIPHON);
The procedure for determining IP addresses for
routeing packets on interconnected IP networks
that support public telephony
---------------------- Page: 3 ----------------------
SIST-TP TR 101 326 V2.0.0:2004
2 ETSI TR 101 326 V2.0.0 (2002-02)
Reference
RTR/TIPHON-04006 [2]
Keywords
architecture, functional, internet
ETSI
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Important notice
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Users of the present document should be aware that the document may be subject to revision or change of status.

Information on the current status of this and other ETSI documents is available at

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If you find errors in the present document, send your comment to:
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Copyright Notification
No part may be reproduced except as authorized by written permission.
The copyright and the foregoing restriction extend to reproduction in all media.
© European Telecommunications Standards Institute 2001.
All rights reserved.
ETSI
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SIST-TP TR 101 326 V2.0.0:2004
3 ETSI TR 101 326 V2.0.0 (2002-02)
Contents

Intellectual Property Rights................................................................................................................................4

Foreword.............................................................................................................................................................4

Introduction ........................................................................................................................................................4

1 Scope........................................................................................................................................................5

2 References................................................................................................................................................5

3 Definitions and abbreviations...................................................................................................................6

3.1 Definitions..........................................................................................................................................................6

3.2 Abbreviations.....................................................................................................................................................8

4 The choice of naming system...................................................................................................................8

4.1 Introduction to naming and addressing ..............................................................................................................8

4.1.1 Naming.........................................................................................................................................................8

4.1.2 Addressing....................................................................................................................................................9

4.1.3 IP addresses..................................................................................................................................................9

4.2 Naming schemes..............................................................................................................................................11

4.2.1 E.164...........................................................................................................................................................12

4.2.2 Internet "names".........................................................................................................................................12

4.2.3 Coding of names .........................................................................................................................................12

4.3 The relationship of naming to services.............................................................................................................13

4.4 The choice of naming for Tiphon.....................................................................................................................14

4.5 The relationship of the present document to ENUM........................................................................................15

4.6 The use of aliases .............................................................................................................................................18

4.7 Master IDs and personal numbering.................................................................................................................18

4.8 Relationship to back end services.....................................................................................................................18

5 Types of resolution and their order ........................................................................................................19

5.1 Introduction......................................................................................................................................................19

5.2 Search resolution..............................................................................................................................................21

5.3 Service resolution.............................................................................................................................................21

5.4 Routing resolution............................................................................................................................................22

6 Routing in SCNs.....................................................................................................................................22

6.1 Introduction......................................................................................................................................................22

6.2 Routeing numbers.............................................................................................................................................22

7 Resolutions in Tiphon Release 3 networks at the meta-protocol level...................................................23

8 Other issues............................................................................................................................................24

8.1 Firewalls...........................................................................................................................................................24

8.2 NATs................................................................................................................................................................25

9 Application to SIP and H.323.................................................................................................................25

9.1 Application to SIP.......................................................................................................................................25

9.2 Application to H.323...................................................................................................................................26

Annex A: Overview of SIP ....................................................................................................................28

Annex B: Overview of H.323.................................................................................................................30

History ..............................................................................................................................................................31

ETSI
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4 ETSI TR 101 326 V2.0.0 (2002-02)
Intellectual Property Rights

IPRs essential or potentially essential to the present document may have been declared to ETSI. The information

pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found

in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in

respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web

server (http://webapp.etsi.org/IPR/home.asp).

Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee

can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web

server) which are, or may be, or may become, essential to the present document.
Foreword

This Technical Report (TR) has been produced by ETSI Project Telecommunications and Internet Protocol

Harmonization Over Networks (TIPHON).
Introduction

The present document explains the procedures for routeing of public telephony calls to an IP network. Starting point are

the existing requirements in TS 101 324 [2] on numbering, and the numbering options for users on IP terminals as

identified in TR 101 327 [3]. Additional general requirements for E.164/IP resolution are identified. These requirements

may form the basis for a service capability description for call routeing.
The present document is based on the architecture developed in Tiphon WG2.
ETSI
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5 ETSI TR 101 326 V2.0.0 (2002-02)
1 Scope

The present document provides a collection of information and guidance relating to:

- the choice of naming schemes;
- the relationship of names to services;
- the role of the proposed ENUM system; and
- the resolution of names in the process of routing

for the routing of public telephone calls (i.e. calls where the called party is identified by an E.164 number) to a

terminating IP network or an IP network that supports a gateway back to an SCN. The calls may originate from or

transit public IP based or SCN based networks.

NOTE: This is intended to be approximately equivalent to the public telephone service defined in

ITU-T Recommendation E.105.

The present document is applicable to all networks that support the public telephony service and is therefore written on

the basis that the E.164 numbering scheme is used for calling and called party identification. Nevertheless the

underlying principles could also be applied with minor adaptation to private network numbering schemes.

The present document applies to calls to most types of number structures within E.164 [13], and includes the support of

carrier selection and number portability. It does not specifically address the support of mobility or roaming, although it

would apply to the routeing of a call to the home mobile network.

The types of IP network considered include but are not limited to TIPHON Release 3. Because the routing aspects of

the present document focus mainly on routing between networks for the support of a common service (public

telephony), the report has a different emphasis from the main emphasis of TIPHON Release 3, which is focused on the

provision of customized services to the customers of a single service provider.

The present document covers only the routeing between networks. It does not include the routeing inside a terminating

network.
2 References
For the purposes of this Technical Report (TR), the following references apply:

[1] ETSI TS 101 314: "Telecommunications and Internet Protocol Harmonization Over Networks

(TIPHON); Network architecture and reference configurations; TIPHON Release 2".

[2] ETSI TS 101 324: "Telecommunications and Internet Protocol Harmonization Over Networks

(TIPHON); Numbering; Scenarios 1, 2, 3 and 4".

[3] ETSI TR 101 327: "Telecommunications and Internet Protocol Harmonization Over Networks

(TIPHON); Guide to numbering options for public networks based on VoIP technology".

[4] ETSI TR 101 287: "Services and Protocols for Advanced Networks (SPAN); Terms and

Definitions".

[5] ETSI TR 102 081: "Network Aspects (NA); Number Portability Task Force (NPTF); Signalling

requirements to support number portability".

[6] ETSI TR 101 697: "Number Portability Task Force (NPTF); Guidance on choice of network

solutions for service provider portability for geographic and non-geographic numbers".

[7] ETSI TR 101 119: "Network Aspects (NA); High level description of number portability".

[8] ETSI TR 101 118: "Network Aspects (NA); High Level Network Architecture and Solutions to

support Number Portability".
ETSI
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[9] ETSI TR 101 122: "Network Aspects (NA); Numbering and addressing for Number Portability".

[10] ETSI EG 201 367: "Intelligent Network (IN); Number Portability Task Force (NPTF); IN and

Intelligence Support for Service Provider Number Portability".

[11] ITU-T Recommendation H.225.0: "Call signalling protocols and media stream packetization for

packet-based multimedia communication systems".
NOTE: See annex G: "Communication between Administrative Domains".

[12] ITU-T Recommendation Q.769.1: "Signalling system No. 7 - ISDN user part enhancements for the

support of number portability".

[13] ITU-T Recommendation E.164: "The international public telecommunication numbering plan".

[14] ITU-T Recommendation E.105: "International Telephone Service".

[15] ISO 3166: "Codes for the representation of names of countries and their subdivisions".

[16] ITU-T Recommendation E.191: "B-ISDN addressing".

[17] ETSI ETR 316: "Broadband Integrated Services Digital Network (B-ISDN); Numbering and

addressing in B-ISDN".
[18] IETF RFC 2543: "SIP: Session Initiation Protocol".
[19] IETF RFC 2131: "Dynamic Host Configuration Protocol".
[20] IETF RFC 1715: "The H Ratio for Address Assignment Efficiency".
[21] IETF RFC 1035: "Domain names - implementation and specification".

[22] ITU-T Recommendation H.323: "Framework and wire-protocol for multiplexed call signalling

transport".
[23] ITU-T Recommendation H.248: "Gateway control protocol".
[24] IETF RFC 2871: "A Framework for Telephony Routing over IP".
[25] IETF RFC 2327: "SDP: Session Description Protocol".

[26] ITU-T Recommendation Q.931: "ISDN user-network interface layer 3 specification for basic call

control".

[27] ETSI TS 101 878: "Telecommunications and Internet Protocol Harmonization Over Networks

(TIPHON) Release 3; Service Capability Definition; Service Capabilities for a simple call".

3 Definitions and abbreviations
3.1 Definitions

For the purposes of the present document, the following terms and definitions apply:

address: string or combination of digits and symbols which identifies the specific termination points of a

connection/session and is used for routeing

called number: normally, name written as a numerical string identifying the called party or called terminal

ETSI
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7 ETSI TR 101 326 V2.0.0 (2002-02)

contact ID: intermediate identifier for the destination of the next point of resolution, i.e. the destination of the next hop

for the signalling messages

NOTE: The form of the Contact ID may vary and may or may not depend on the protocol and the technology

used in the transport plane.
destination network: network to which a call is currently being routed

NOTE: For service resolutions that take place before the home network is reached, the destination network is the

home network. For service resolutions performed by the home network (e.g. call forwarding or the

support of roaming) this is the visited network.

E.164 number: number conforming to the numbering plan and structure specified in ITU-T Recommendation E.164

NOTE: See ITU-T Recommendation E.164 [13].
ENUM: telephone number mapping
NOTE: IETF working group.

home network name: network on which the customer's service application is provided whether by the network

operator or a separate service provider, e.g. the network on which the customer has a subscription

NOTE: This is in most cases the network through which the customer is assigned its E.164 number.

internet named telephony: service that supports conversational voice and uses Internet names for the identification of

the called party

name: combination of alpha, numeric or symbols that is used to identify end-users

NOTE: A name may be portable between Service Providers.

public telephony: service that conforms to ITU-T Recommendation E.105, i.e. it supports conversational voice and

uses E.164 numbers for the identification of the called party

NOTE: From the perspective of the present document, the only point of significance is the use of E.164 numbers.

The issue of whether any quality requirements should be applied to public telephony or whether E.164

numbers should be allocated only to services that achieve a certain threshold of quality is outside the

scope of the present document. See ITU-T Recommendation E.105 [14].

Routeing Number (RN): within TIPHON, specific number that is used by the networks to route the call

NOTE: The Routeing Number conveys information in a form more readily usable by the network (e.g. to route

calls to a ported number).
routeing: set of instructions on how to reach a destination
Second Level Domain name (SLD): part of the names in the DNS below the TLD

NOTE: Under the country code TLDs, there is a wide variation in the structure, in some countries the structure is

very flat, in others there is substantial structural organization. In some country domains the second levels

are generic categories (such as, AC, CO, GO, and RE), in others they are based on political geography,

and in still others, organization names are listed directly under the country code.

Top Level Domain name (TLD): part of name structure in the Domain Name System (DNS) under the control of the

Internet Corporation for Assigned Names and Number (ICANN)

NOTE: In the DNS naming of hosts (computers) there is a hierarchy of names. The root of system is unnamed.

Below the root, there is a set of what are called "top-level domain names" (TLDs). They include the

generic TLDs (EDU, COM, NET, ORG, GOV, MIL, and INT and new ones that are under creation), and

the two letter country codes such as .UK, .DE and .JP from ISO-3166 [15].

transit network: network between two networks, e.g. between the originating network and the terminating network

NOTE: A transit network is not always present in a call, but in some calls there may be more than one transit

network present.
ETSI
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8 ETSI TR 101 326 V2.0.0 (2002-02)
3.2 Abbreviations
For the purposes of the present document, the following abbreviations apply:
ACK ACKnowledge
ALG Application Layer Gateway
CR Call Routing
DHCP Dynamic Host Configuration Protocol
DNS Domain Name Server
ICANN Internet Corporation for Assigned Names and Number
ID IDentifier
IETF Internet Engineering Task Force
IP Internet Protocol
ISDN Integrated Services Digital Network
ISP Internet Service Provider
ISUP ISDN User Part
ITU International Telecommunication Union
LAN Local Area Network
NAT Network Address Translators
NOA Nature Of Address
PSTN Public Switched Telephone Number
RN Routeing Number
RTP Real Time Protocol
SC Service Control
SCN Switched Circuit Network
SDP Session Description Protocol
SIP Session Initiation Protocol
SLD Second Level Domain
SMS Short Message Service
TCP Transmission Control Protocol
TLD Top Level Domain
TRIP Telephony Routing over IP Protocol
TSAP Transport layer Service Access Point
UAC User Agent Client
UAS User Agent Server
UCI Universal Communications Identifier
UDP User Datagram Protocol
UPT Universal Personal Telephony
URL Uniform Resource Locator
VoIP Voice over the Internet Protocol
4 The choice of naming system
4.1 Introduction to naming and addressing
4.1.1 Naming

A name is a "combination of characters and is used to identify end users (character may include numbers, letters and

symbols)".
NOTE: According to ITU-T Recommendation E.191 [16].

An end user is "a logical concept which may refer to a person, a persona (e.g. work, home etc.), a piece of equipment

(e.g. NTE, phone etc.), an interface, a service (e.g. freephone), an application (e.g. video on demand), or a location".

ETSI
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A name is distinct in function from an address, which " identifies the specific termination points of a connection and is

used for routeing". Addresses are essential for communication as the end points always have to be identified in a way

that can be used for routing, but names are not essential. Names are added for some services to make it easier for users

to identify the distant end-point or to provide an identification system that is independent of the structure of the

networks or the current location of the entity to be communicated with.
4.1.2 Addressing

An address is defined as "a string or combination of digits and symbols that identifies the specific termination points of

a connection and is used for routeing". An address is a specification of the location of the entity in terms of network

structure. It includes information about the location within the network and may also include the identity of the network

itself and its location in the topology of interconnected networks. An address identifies the interface at which the

connection is to be delivered without regard to whether the connection continues beyond that interface. It contains

location information and in telecommunications this is expressed in terms of the network structure in order to achieve as

high as possible a degree of aggregation that reduces the complexity of routing tables in switches or routers.

NOTE 1: According to ETR 316 [17].

Addresses differ from names in that addresses contain explicit network information and this information is what makes

them usable for routing. In order to route a call or a packet, the called name must be translated into an address that

identifies the location in network terms and so can be used in the routing process. When a name is ported from one

location or one service provider to another, the address associated with the name changes.

Unfortunately the distinction between name and address is not followed consistently and entities that are names, or

closer to names than addresses, are often spoken of as addresses. A Uniform Resource Locator (URL) pointing to a

company's web page is often called an Internet address, but is actually based on a domain name.

NOTE 2: Often the word "address" is used to mean "containing location information" but this is not sufficient for

the purposes of the distinction between names and address in telecommunications. Here the critical issue

is whether the location information is specified in terms of network structure. For example, An E.164

number may contain location information if numbering is related to geographical areas, but such a

number may be a name rather than an address if the structure that provides the location information does

not relate explicitly to network structure. This would be the case for example if there is number

portability between competing networks.

NOTE 3: Where a communications system is structured in terms of layers with each layer offering a service to the

layer immediately above and using the services of the layer immediately below, the identities offered to

the layers tend to have the properties of names. Yet when viewed from the layer above, the same

identifiers have the properties of addresses. This difference in perspective may explain why the term

"address" is used for email and SIP (see IETF RFC 2543, [18]) identifiers e.g. "email address" and SIP

"address".
4.1.3 IP addresses

IP addresses are allocated to interfaces, but different communication streams using different protocols may share the

same interface. These streams are differentiated using port numbers which are carried in the protocol (e.g. TCP, UDP or

RTP) that runs on top of IP. The combination of an IP address and a port number uniquely identifies the source or

destination of a stream of packets flowing between two end points. Each application protocol has a "well known" fixed

port number assigned to it plus a range of port numbers for dynamic assignment to communication streams.

IP addresses are divided, in principle, into two parts:
- the identity of the network (the network part);

- the identity of the interface attached to the network (the host address, which is the destination of the IP packet).

IP address allocations are normally made through ISPs to end networks. The allocations to ISPs are made in blocks and

are organized as far as practicable to be aggregatable so that traffic on a particular route is likely to have addresses in

contiguous blocks. This is important to reduce the size of the routeing tables in routers where several contiguous blocks

that share the same route require only one entry. The size of these routeing tables is a potential bottleneck in the growth

of the Internet as router technology is only just keeping ahead of the traffic growth.

ETSI
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ISPs normally allocate blocks of addresses to end networks. Where the end networks have permanently connected

terminals e.g. PCs connected to a LAN, the addresses may be allocated permanently to the terminals.

Conversely where terminals are likely to be disconnected frequently and where dial-up access is used, IP addresses are

normally allocated dynamically, e.g. using the Dynamic Host Configuration Protocol (DHCP) (see RFC 2131 [19]).

Addresses are allocated from a pool only while the customer is logged-on. After logging-off the same address will be

allocated to another user.

There are two versions of IP protocols, whose address formats differ significantly:

- IPv4, a 32-bit address, which is used throughout the Internet but which is considered to be in increasingly short

supply and whose allocations are being controlled carefully.

- IPv6, a 128-bit address, which is just starting to be used and should provide more than adequate capacity for the

future if it is administered effectively.

IPv4 is the version of the IP protocol in general use. Use of IPv6 is only just beginning. Because the address lengths are

different, the two addresses are not compatible and a long process of migration is beginning.

There are two main drivers for moving to IPv6:
- Avoiding problems when IPv4 addresses reach exhaustion.

- Obtaining benefits from features that IPv6 offers that are not available in IPv4.

There is however a disadvantage. The IPv4 header has a variable length with the minimum being 192 bits. The IPv6

header has a fixed length of 320 bits, with the possibility of additional extension headers that are normally used only by

the end nodes. The fixed header length simplifies the packet handling in routers but the increased length reduces the

efficiency of transmission unless header compression is applied.

UDP has a 64 bit header and TCP a 224 bit header. Therefore the maximum reduction in efficiency is 33 %

(100 x (1 - ((192 + 64) / (320 + 64)))) for a zero length packet. However for speech for a 4 kbit/s speech codec with a

packetization delay of 40 ms the speech packet would have a length of 4 000 x 0,04 = 160 bits and the efficiency

reduction would be 24 %. For data using TCP the minimum reduction for a zero length packet would be 21 %. Thus the

reduction in efficiency is greater for speech than data.

A significant uncertainty is the speed with which IPv6 will be introduced generally in the Internet world. Here there are

two extremes and a continuum of possibilities between them.
- The first extreme is that ISPs will perceive
...

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