One document matched: draft-lee-e164-framework-00.txt
Internet Draft
Title: draft-lee-e164-framework-00.txt C. C. Lee
Date: November, 1998 M. Orsic
Lucent Technologies
A Framework for E.164 Number to IP Address Mapping
Status of this Memo
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Abstract
This internet draft describes a framework for mapping the E.164
number of internet telephony (IT) subscribers to an IP addresses so
that calls can be delivered to IT subscribers.
The draft describes:
- assumptions that the framework is based on
- goals that the framework is designed for
- functionality of network entities
Several scenarios are included to illustrate the procedure.
1.0 Introduction
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This internet draft describes a framework for mapping an E.164 number
[E.164] of an internet telephony (IT) subscriber to an IP address so
that calls can be delivered to the subscriber. Assigning E.164
numbers to IT subscribers not only makes it easier for traditional
phone users to call IT subscribers, but it will also allow service
providers to leverage the existing infrastructure to provide IT
services. It can also facilitate the convergence of wireline/wireless
services and emerging IT enhanced services. The assignment of E.164
numbers to IT subscribers and the IP address based routing in the
internet give rise to a fundamental need for mapping the E.164
numbers to IP addresses in the IT infrastructure.
The IT subscribers may gain access to the IP network by employing
wired-line, wireless (e.g. wireless LAN, cellular access), or cable-
modem connections. Roaming IT subscribers should be able to log onto
the IP network from any location, while the IT subscribers that use
fixed access will be connected to the IP network at fixed location.
Calls to IT subscribers may originate from PSTN wireline, wireless
subscribers, or from other IT subscribers. It is assumed in this
draft that when placing a call to an IT subscriber, the caller will
specify the E.164 as a called number.
The problem of IT gateway discovery for IP originated and PSTN
terminated calls based on the called subscriber's E.164 PSTN number
is currently being addressed by the IPTEL working group [GLP] and is
outside the scope of this draft.
The requirements needed to design a new protocol or to enhance an
existing protocol will have to be addressed after the mapping
framework has been determined. No attempts have been made to map the
functionality of servers involved in this framework to existing
servers in the internet or PSTN servers that are IP enabled. It will
be advantageous to enhance existing servers to realize this
framework. Candidates may include IP enabled Service Control Points,
IP enabled HLR/VLR, DNS, LDAP servers, Radius servers, and other
existing internet directory servers.
1.1 Terminal Status
When a call to an IT terminal is initiated, the called IT terminal
may be in one of three different states. Each state has a certain
level of readiness depending on the IP network to which the IT
terminal is connected.
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- When in a "idle" state, no calls can be delivered to the IT
terminal. The terminal may be powered off or it is powered on
but not connected to the IP network. At this state, no dynamic
IP address is assigned to the terminal and no IT calls can be
delivered to it.
- In a "standby" state, the IT terminal is powered on, connected
to the IP network and has an IP address assigned, but the IT
application is not running. In this state, no calls can be
delivered to the IT terminal.
There are several ways a transition from the "idle" state to the
"standby" state can occur. Users may connect to the network by
registration during which IP addresses are assigned to the
terminals. For wireless accessed terminals, the paging
mechanism may be used to trigger the transition. When the
mobile is paged with an indication of data serivce type, it may
initiate a registration process to get the terminal connected to
the IP network and obtain an IP address.
- In the "ready" state, the IT terminal is connected to the IP
network, has an IP address assigned, and the IT application has
been invoked. The terminal is ready to receive an incoming IT
call.
The transition from the "standby" state to the "ready" state may
be triggered manually by users or automatically by programs in
the terminals.
2.0 Acronym
DDS: Dynamic Directory Server
DNS: Domain Name Server
HLR: Home Location Register
IMSI: International Mobile Subscriber Identity
ISP: Internet Service Provider
IT: Internet Telephony
ITHS: Internet Telephony Home Server
LDAP: Lightweight Directory Access Protocol
MSC: Mobile Switching Center
NAI: Network Access Identifier
NAS: Network Access Server
RAS: Registration Authentication and Status
SCP: Service Control Point
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SIP: Session Initiation Protocol
VLR: Visitor Location Register
3.0 Framework Design Basis
The framework documented in this internet draft is designed based on
the following assumptions:
- E.164 numbers are managed by existing numbering management
administrations. Internationally, the ITU Telecommunication
Standard Board assigns country/service codes; and within a
geographic area, a national or regional numbering administration
has the responsibility of managing the numbering plan for the
countries assigned to the area. To have the E.164 number
allocation process managed by the existing numbering plan
administrations can expedite the allocation process, leading to
an earlier IT service deployment.
Internet telephony service providers will obtain blocks of E.164
numbers from numbering plan administrations for their
subscribers.
- For scalability purpose, subscriber-related data may be
partitioned and distributed among multiple servers of the same
type. These servers may be owned by individual service providers
or by trusted third party service providers.
- An IT subscriber with a specific E.164 number will ordinarily
subscribe to the service of one IT service provider. The service
provider or a trusted third provider will maintain the data
related to that subscriber, including the IP address that the
subscriber can currently be reached.
If the subscriber uses the same E.164 number for the same
service from more than one provider, other criteria need to be
used for determining which service provider's subscriber
database to be consulted for call delivery. It is emphasized
that the service provider whose database was queried needs not
carry the call.
4.0 Design Goals
The design goals of the framework are described as follows:
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- Because some, and gradually more, of internet service
subscribers will be assigned IP addresses dynamically even if
they access the network from fixed locations, the framework
needs to support the mapping to a dynamically assigned IP
address. For subscribers with static IP addresses assigned, a
subset of the framework may be used for the mapping.
- The framework should allow the call originator to use an
internet telephony service provider that is different from the
one subscribed to by the call recipient.
- The framework should allow for enhanced services to be provided
in conjunction with the framework. For example, to provide a
"least cost" service, a "bidding" server may be consulted before
the mapping to find the least cost service provider for carrying
the call.
- The framework should allow for including more information into
the query than just the phone number or prefix and the security
information; and more output in the response than just the IP
address for contact. The response may contain such information
as the call receiving status of the destination equipment, call
restrictions, or information to be placed into subsequent SIP or
H.323 message (e.g. authorization information).
- The framework should allow for information to be exchanged for
subsequent collection of fees incurred.
- The framework should allow for scalability to support high
capacity.
- The framework should allow for PSTN/IT convergence, including
wired access and wireless access for subscribers.
- The framework should support service mobility for roaming IT
subscribers. When a roaming IT subscriber accesses the internet
from a location different than the home location, the same
services offered on the home network should be available to the
roaming IT subscriber on the visited network.
- The framework should allow service providers, who prefer to
maintain otherwise separate network infrastructures for
different services, to deploy a common infrastructure for
similar types of mapping. In this case, the type of mapping
requested will qualify the request.
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5.0 Architecture Framework
Figure 1 shows the proposed E.164 number to IP address mapping
framework. This arrangement is modeled after the location management
and call delivery aspect of the wireless network architecture. The
wireless network has addressed and solved the problem of delivering a
call to a mobile subscriber whose point of attachment (i.e. dynamic
address) to the network changes from time to time.
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.
Internet . PSTN
.
______ .
| | .
| IT | . _____
|Subscr|. . |Wired|
|______| . ____._____ |Phone|
call . | | . |_____|
recipient . | IT | . call
.____ ____ | Gateway |. originator
| | | | | or |
|DDS |..|ITHS|..| |
|____| |____| | IT |
. | Call |.
______ . |Processing| . _________
| | . .| Proxy | . | |
| IT |. . |__________| |WLS Phone|
|Subscr| . . |_________|
|______| . . call
call ________ . originator
recipient | | .
|IT Subsc| .
|________| .
call originator .
.
.
Internet . PSTN
.
Figure 1: Architecture Framework for E.164 Number to IP Address Mapping
The major function of the Internet Telephony Home Server (ITHS) is to
store static data for individual IT subscribers. The proposed
Dynamic Directory Server (DDS) stores subscribers' dynamic data. The
IT Gateway or the IT Call Processing Proxy is the requester for
address mapping. The main function of the ITHS working in conjunction
with DDS will be to find the IP address of the terminating IT
subscriber or its proxy where terminating call request shall be sent.
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There will be multiple ITHSs and DDSs in the network infrastructure.
The ITHS and the DDS can be geographically distributed and the DDS
may be located at the point of registration.
Note that if no mobility is involved and capacity is not an issue,
the ITHS and the DDS may be collocated or reside on the same
hardware.
5.1 Functionality of Internet Telephony Home Register
When a call is to be delivered to an IT subscriber, the ITHS of the
called IT subscriber is consulted for the call delivery.
The IT subscriber's static data stored in the ITHS may include:
- subscriber identifier information, E.164 number, network access
identifier (NAI) [NAI], etc
- billing related information, e.g. tokens
- security related information, and
- the IP address or a pointer to the DDS where the IT subscriber
is currently registered
5.2 Functionality of Dynamic Directory Server
The major function of the DDS is to store the dynamic data for
individual IT subscribers. The IT subscriber's data stored in the DDS
may include:
- subscriber identifier information, including network access
identifier,
- for wireless subscribers, paging information used by the paging
system to request that the IT terminal registers with a local IP
network,
- subscribers IP address stored at the registration time
- current status for receiving IT calls
- capability of equipment a subscriber uses currently,
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- other call delivery related information, such as session key and
other security related information, and
- pointers to ITHS.
5.3 Basic Scenario
5.3.1 Subscriber Registration
The registration procedure may be initiated by the IT terminal or it
may be requested by the network, upon incoming call arrival, by
employing the paging mechanism.
- A message to request for registration is received from the
terminal. The subscriber is authenticated, and a temporary IP
address is assigned to the terminal. The network access server
will inform the DDS of the IP address if the subscriber has
subscribed to IT services.
- The DDS stores the IP address to user identifier association in
its database.
- The DDS sends a message to inform the ITHS of the identifier of
the DDS where the subscriber is currently registered. The
address of the ITHS is obtined based on the NAI of the
subscriber.
For fixed accessed subscribers, this and the next steps need not
be performed for every registration.
- The ITHS stores the NAI to DDS identifier association in its
database.
5.3.2 PSTN to IT Subscriber Call Delivery
The scenario described below illustrates a call to a IT subscriber
that originated from a PSTN subscriber.
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- The IT gateway receives a call from the PSTN. The IT Gateway,
finds the location of the ITHS for the respective IT subscriber
by consulting a translation table, internally or externally.
- The IT Gateway sends the E.164-to-IP-address mapping request to
the ITHS and specifies the type of information desired.
- The ITHS receives the request that indicates an IT terminating
call and informs the DDS of the incoming call and requests IP
address information.
- Based on the IT terminal status, the DDS either pages the IT
terminal triggering the registration procedure or the requested
information is already available. Upon completion of the
registration procedure, the DDS retrieves the IP address and
other information requested from its data store, forms a
response, and sends it back to the ITHS.
- The ITHS retrieves other information requested by the IT
Gateway, sends a response to the IT Gateway together with the IP
address.
Now the gateway can start call setup procedures to the destination
subscriber as per H.323 version 2 [H323], Session Initiation Protocol
[SIP], or other protocols.
6.0 Security Considerations
Security is vital for the framework to be implemented in the internet
environment. This may include
- mutual authentication of the query source and the response
source for each transaction,
- non-repudiation of response. This is most important when cost
related information is exchanged in the messages. The non-
repudiation for query may also be needed depending on business
arrangement among service providers,
- query authorization,
- response data integrity, and
- message confidentiality if data carried includes security
sensitive information, such as a session key
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The security requirements should be communicated to the
Authentication Authorization and Accounting Working Group.
7.0 Reference
- [E.164] ITU-T, E.164, "The International Public
Telecommunication Numbering Plan", 5/1997
- [NAI] Aboba, Beadles, "Network Access Identifier", Internet-
Draft, draft-ietf-roamops-nai-11.txt, July 1998
- [H323] ITU-T, H.323, "Packet-based multimedia communications
systems", 2/1998
- [SIP] Handley, Schulzrinne, Schooler, Rosenberg, "SIP: Session
Initiation Protocol", Internet-Draft, draft-ietf-mmusic-sip-
09.txt, 9/1998
- [GLP] Rosenberg, Schulzrinne, A Framework for a Gateway Location
Protocol", draft-ietf-iptel-gwloc-framework-01.txt , 10/1998
- Faltstrom, "Where to terminate a phone call", Internet Draft,
draft-faltstrom-e164-00.txt
Author's Address
Milo Orsic
Lucent Technologies
263 Shuman Blvd
Naperville, IL 60566
Phone: (630) 713 5161
Email: orsic@lucent.com
Chinmei Lee
Lucent Technologies
263 Shuman Blvd
Naperville, IL 60566
Phone: (630) 713 7256
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EMail: chinmeilee@lucent.com
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