1

NGN Issues - Numbering and Addressing

Peter DarlingACIF NGN FOG No. 3

2

Numbering in Carrier Networks

• Carrier networks use E.164 numbers Allocated at the national level With the addition of a country code, provides a

unique global number

+61 3 5422 7503

• E.164 numbers serve as both network addresses and end user “names”

3

Internet Principles - Addressing

• A unique IP address is allocated for each end-point Because of limited address space in IPv4, IP

addresses are often allocated on a dynamic basis from an available pool allocated to the service provider

The greater address space available in IPv6 is designed to overcome this problem

• IP addresses are allocated globally, not at the national level

• IP addresses generally only have network significance

4

Internet Principles - Naming

• The Domain Name system is designed to provide a means for end-user access to required resources

• The system of Domain Name Servers translate the URL entered by a user into an IP address to be incorporated into each packet header

• The correct operation of the DNS is essential for the operation of the Internet

5

Internet Operation

• The user’s equipment prepares to send the first packet

• The initiating user provides the details of the desired destination e.g. www.acif.org.au

• A request for information goes to the root server for the Domain (.au in this case) and any subsequent domain name servers.

• The DNS returns the IP address of the desired destination (acif.org.au)192.148.121.105

6

NGN Issues

• Carrier services on the NGN are likely to have an E.164 number (e.g. telephony) This number will be used by

callers and when interworking with current networks

• End-points on the NGN and Internet will have IP addresses (and other addresses such as SIP addresses) These addresses will be be

needed for NGN connectivity

• There is a need to translate between the two addressing schemes

ISP

2G Mobile

“Carrier Grade” IP-based Networks

“Carrier Grade” IP-based Networks

“The Internet” (best-endeavours

network)

ISPISP

ISP

PSTN

ISP

7

ENUM

• The IETF has developed the ENUM specification to enable an E.164 number to be used to access the DNS system ENUM can be used to facilitate interworking

between telephony (and other carrier services) and IP services (including IP telephony and multimedia)

As a database, ENUM could also store other information about the owner of the E.164 number, such as the services (and their addresses) registered by the owner

• The IETF and ITU-T Study Group 2 are looking at the implementation of ENUM

8

ENUM supporting Interworking

Termination

----------------

Origination

IP Based Network Only

Both PSTN Only

IP Based Network

ENUM used for address translation and, to some extent, service priority

ENUM used to determine destination (based on service priority) and address translation

ENUM used to determine address translation

PSTN ENUM used for address translation

ENUM may be used

ENUM may or may not be used

From Internet Draft draft-ietf-enum-usage-scenarios-00

9

Call from PSTN to IP-Based Network

• Caller dials an E.164 number, using either local, national or international format

POTS Phone

PSTN Gateway

IP Based Network

SIP Server

SIP Client

POTS Phone

From Internet Draft draft-ietf-enum-usage-scenarios-00

Voice Path

Signalling Path

10

Call from PSTN to IP-Based Network

• The PSTN routes the call to the IP network gateway. This could be selected by either the number allocation to the IP service provider or a separate IP number range but what about number portability?

POTS Phone

PSTN Gateway

IP Based Network

SIP Server

SIP Client

POTS Phone

From Internet Draft draft-ietf-enum-usage-scenarios-00

Voice Path

Signalling Path

11

Call from PSTN to IP-Based Network

• The gateway translates the E.164 address (after conversion to full international number) to an ENUM format

• The gateway interrogates the DNS, which returns any service records associated with the E.164 number/URL

POTS Phone

PSTN Gateway

IP Based Network

SIP Server

SIP Client

DNS

From Internet Draft draft-ietf-enum-usage-scenarios-00

Voice Path

Signalling Path

12

Call from PSTN to IP-Based Network

• In this example, the record indicates that the wanted destination uses a SIP server

• The gateway interrogates the DNS for the IP address of the required SIP server

POTS Phone

PSTN Gateway

IP Based Network

SIP Server

SIP Client

DNS

From Internet Draft draft-ietf-enum-usage-scenarios-00

Voice Path

Signalling Path

13

Call from PSTN to IP-Based Network

• The call is routed via the IP-based network to the SIP server

POTS Phone

PSTN Gateway

IP Based Network

SIP Server

SIP Client

DNS

From Internet Draft draft-ietf-enum-usage-scenarios-00

Voice Path

Signalling Path

14

Call from PSTN to IP-Based Network

• The SIP Server routes the call to the SIP Client for the called user

• When the destination party answers/clears, this information is signalled back to the PSTN

POTS Phone

PSTN Gateway

IP Based Network

SIP Server

SIP Client

DNS

From Internet Draft draft-ietf-enum-usage-scenarios-00

Voice Path

Signalling Path

15

Other Information that may be Stored

• A range of “enumservice” can be defined, to store information associated with the owner of the E.164 number. These could include IP and SIP addresses for service delivery SMTP (email) addresses WWW URL Fax (IP or PSTN) Redirection addresses (temporary or permanent,

on IP or PSTN Personal information (name, address, account

details

16

Current ACA Discussion paper

• The ACA issued a Discussion Paper “Introduction of ENUM in Australia” in September 2002

• This paper concentrated on the Regulatory and Consumer issues from a database such as ENUM provides “consideration of existing regulatory provisions

which provide consumer protection, choice and protect the long-term interests of end-users”

• The paper addresses the important issues of security and authenticity

17

ENUM Issues• What is the requirement for routing calls to

destinations defined by E.164 numbers in IP-based network? Is the ENUM approach essential, and if so how can the two

different roles (routing aid and personal data-base be separated)

Is it desirable (the same questions apply)> If not required, what alternate approach can be used?

[The current difference between numbering for routing and operational purposes (CLI and IPND database) and optional number display may provide a precedent]

18

General Issues• At some future time there could be two main groups of

networks in operation, one circuit-switched, the other packet-switched. In such a case, there are advantages in a network architecture that crosses to the terminating section as soon as possible (minimising encoding/conversion, for example.

• Should/could there be separate number ranges for IP based multimedia services to assist routing (and provide user information? Could numbers be used to indicate service/QoS

requested/provided?

• If telephony service is provided on both groups of networks, how can number portability be supported whilst allowing network separation

• Should all calls be routed by an ENUM style database to support portability and optimum routing?