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Versions: 00                                                            
Network Working Group                                        D. Schwartz
Internet-Draft                                  XConnect Global Networks
Intended status:  Standards Track                                R. Mahy
Expires:  January 7, 2009                                    Plantronics
                                                                A. Duric
                                                                E. Lewis
                                                            July 7, 2008

              Consolidated Provisioning Problem Statement

Status of this Memo

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Copyright Notice

   Copyright (C) The IETF Trust (2008).


   This document describes the type of data provisioned among Voice
   Service Providers and underscores the need for clearly defined
   structures and interfaces to facilitate this provisioning.  This work

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   is in support of the service provider peering as defined by the

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Registry Data  . . . . . . . . . . . . . . . . . . . . . . . .  4
     3.1.  Index/Key Data . . . . . . . . . . . . . . . . . . . . . .  4
     3.2.  Resolution Data  . . . . . . . . . . . . . . . . . . . . .  5
   4.  Reachability vs. Routing . . . . . . . . . . . . . . . . . . .  6
   5.  Operations on the Registry Data  . . . . . . . . . . . . . . .  6
   6.  Other Atrributes . . . . . . . . . . . . . . . . . . . . . . .  7
   7.  Data Encoding  . . . . . . . . . . . . . . . . . . . . . . . .  7
   8.  Data Management  . . . . . . . . . . . . . . . . . . . . . . .  7
   9.  Data Propegation . . . . . . . . . . . . . . . . . . . . . . .  8
   10. Querying The Registry  . . . . . . . . . . . . . . . . . . . .  8
   11. Control  . . . . . . . . . . . . . . . . . . . . . . . . . . .  8
   12. Existing Technologies  . . . . . . . . . . . . . . . . . . . .  8
   13. Security Considerations  . . . . . . . . . . . . . . . . . . .  9
   14. IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  9
   15. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . .  9
   16. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     16.1. Normative References . . . . . . . . . . . . . . . . . . . 10
     16.2. Informational References . . . . . . . . . . . . . . . . . 10
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11
   Intellectual Property and Copyright Statements . . . . . . . . . . 12

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1.  Introduction

   VoIP Service Providers (VSPs) engage in peering relationships with
   other VSPs to create direct IP-to-IP interconnections.  These
   relationships provide network reach, greater technical capabilities
   and enhanced economic benefit beyond that available with the Public
   Switched Telephone Network (PSTN), while providing the security
   benefit perceived to exist in the PSTN.

   Because the business and operational management of hundreds or
   thousands of direct peering relationships is difficult, VSPs often
   enlist the help of peering exchanges to centralize (or assist
   [I-D.ietf-speermint-terminology] with) the management of the
   relationships.  One of the central functions of these peering
   exchanges is a registry of identifiers (often implemented as a
   private ENUM tree) based on telephone numbers.  This function is
   called the peering or numbering registry.  VSPs participating in the
   peering exchange must provision their identifiers into the peering
   registry to allow other VSPs with access to this registry to query
   and obtain the correct resolution for a given number.  Lack of clear
   standards for this provisioning step has given rise to many
   proprietary approaches that are rendering open provisioning
   cumbersome and error prone.

   VSP peering is not the only driver for this work, however.  It is
   quite common today for one VSP to receive number resolution data from
   both authoritative or regulatory sources (e.g. a national telephone
   number plan administrator) and commercial or private sources.  Since
   eventually all of the information resides locally, the VSP is
   interested in merging resolution data across potentially different
   local platforms so as to avoid multiple queries for each call.  Today
   this is virtually impossible to do in an efficient and standard
   manner due to the proprietary nature of the individual registry

   In addition, many registry network architectures dictate sub
   registries for overall resilience and performance.  The transfer of
   resolution data to the sub registries is not yet standardized and
   results in unnecessary hardware/software component lock in.

   This document attempts to describe the most common data that needs to
   be exchanged in the cases highlighted above with the ultimate goal
   being that of identifying the data structures and interfaces required
   to support the data exchange scenarios specified above.

   As a final note it is important to stress that while ENUM is not
   mentioned explicitly in this document so as not to bias the outcome,
   it is clear that in the minimum all the information present in a

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   NAPTR RR must be captured as the information therein has been well
   thought out and deviating from this may curtail future growth.
   Additionally, while E.164 numbering is not mentioned either for the
   same reason, it is clear that in almost all cases the prefixes that
   are being exchanged are in the e.164 format.

2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [RFC2119].

   Terms used or referred to elsewhere in the document (including in the

   DNS - Domain Name System [RFC1034]

   RR - Resource Record [RFC1034]

   TXT - DNS Text record [RFC1035]

   NAPTR - Naming Authority Pointer record [RFC3403]

   EPP - Extensible Provisioning Protocol [RFC3730]

   ENUM - E.164 to URI DDDS [RFC3761]

   URI - Uniform Resource Identifiers [RFC3986]

   TLS - Transaction Layer Security [RFC4366]

3.  Registry Data

   Registry Data consists of both Index or Key data and Resolution data.

3.1.  Index/Key Data

   The organization of registry data is based on specific phone numbers
   or phone number prefixes (which could represent blocks of phone
   numbers, regions, or theoretically whole countries).  For generality,
   we will use the term prefix to include complete phone numbers as
   well.  Prefixes are the index or key used for all registry
   manipulation and lookups.  Even though some of the numbers
   represented within these prefixes may not be globally reachable, the
   prefix itself needs to be globally normalized before it can be
   entered into a registry.  These globally normalized prefixes always

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   begin with a plus (+) and a telephone country code.  (Note that
   prefixes in some countries can contain hexadecimal digits).

   Since prefixes have variable lengths, a provisioning protocol must be
   able to enter data for a sub-prefix or super-prefix of an existing
   record.  For example, it must be possible to enter records about
   "+1202555" and "+12025551234" at the same time.  For lookups
   information about the most specific prefix will be returned.  This
   allows for some measure of aggregation.  Also, in order to provide
   maximal flexibility a provisioning protocol must provide a mechanism
   for specifying both minimum and maximum number of digits in a prefix.

3.2.  Resolution Data

   For each prefix, there is a variety of data that can be exchanged.
   The most important set of data identifies that a specific VSP is
   responsible for the prefix and in most cases the VSP provides a SIP
   URI through which this prefix can be reached.

   In complex cases, several VSPs may claim some form of responsibility
   for the same prefix.  We can use the term "last hop" VSP to describe
   the VSP closest to the end-user of a phone number.  The provider who
   was assigned a prefix by the national numbering authority is the
   "first hop" VSP.  The first hop VSP may have no way of knowing if the
   last hop VSP will include itself in the registry.  Therefore it is
   important that the querier can obtain both records and use the most
   specific one which contains reachability information.

   In many cases, commercial registries also contain information used
   for Local Number Portability.  Even if a prefix is not reachable for
   IP peering, it is useful to provide the "dipped" number and carrier
   code.  This information could be provided as a tel URI with the
   number portability attributes defined in RFC 4769 [RFC4769].
   Likewise it is very useful to know that a prefix is known not to
   exist anywhere.

   Like stated in the introduction it is imperative that the minimal set
   of resolution data contain all the information required for a DNS

   Additionally, as a future proofing mechanism it is recommended that
   resolution data include a catchall (similar to a DNS TXT RR) for data
   that is not currently present in any ENUM service definitions.

   One final note.  One of the common "rewrite" rules for the URI in
   NAPTR RRs for example is of the form "\1@somehost.company.example"
   where the "\1" refers to the telephone number being processed.  This
   kind of shorthand should be available when processing prefixes in

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4.  Reachability vs. Routing

   The goal of the registry is to provide sufficient information to
   identify a responsible VSP for a prefix.  The responsible VSP can
   provide a SIP URI that can be proxied or redirected as desired by the
   VSP.  It is important to note that the registry is expected to return
   the same responsibility data for all parties that query it.

   Routing information is also out of scope of the registry provisioning
   problem.  Once a responsible VSP is contacted, that VSP can use a
   variety of techniques to route that request.  For example, the VSP
   could use TRIP [3], a private database, or a SIP location server.
   Since this information is highly dynamic, it is inappropriate to
   provision in a registry.

5.  Operations on the Registry Data

   WBelow is a list of logical operations on the registry data.  Please
   note that as stated above a provisioning protocol MUST apply these
   operations equally to individual prefixes as well as prefix blocks.

   Add:  Add (responsible VSP) data about a new prefix to the registry.

   Delete:  Remove a prefix from the registry.  Semantically it means
   that the prefix no longer exists anywhere.

   Port-out:  A port-out is similar to a delete, but could be logged
   differently.  The semantics are that the prefix still exists, but
   that the previous VSP is no longer responsible for it.

   Port-In:  A port-in is similar to an add, but the semantics are that
   the prefix was previously assigned to a different provider.

   Transfer:  A transfer is a port-out and port-in operation performed
   atomically.  This operation insures that lookups do not fail for the
   transferred prefix during the transfer.

   Renumber:  A renumber operation occurs when a specific prefix is
   completely changed, but the data corresponding to the prefix has not
   changed.  This typically happens when a prefix is lengthened.  For
   example, when France moved from an 8-digit to a 10-digit dial plan,
   the corresponding globally normalized prefix for a Parisian phone
   number had a 1 inserted between the country code and the old prefix.
   Renumbering could also accomplish prefix shortening (although this is

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   quite unlikely to occur) or prefix splitting (in the past United
   States area codes where split when they were exhausted).

   Modify:  A modify operation occurs when some other attribute of a
   prefix is modified (for example the target URI used for

6.  Other Atrributes

   All the registry records will need to include some kind of validity
   information.  The provisioning protocol can indicate that a record is
   not valid before one date and time and no longer valid after another
   date and time.

   In addition to responsibility data, we have identified the following
   extra attributes as important or interesting:

   Regardless of which protocol is used, issues that should be addressed

   Number type (unknown, IP, PSTN, both)

   PSTN carrier code (for numbers with no IP reachability)

   Fee category (free, landline, mobile, pay)

   Media types supported (voice, video, message)

   There MUST be a mechanism for an audit trail as issues of ownership
   are bound to surface and a clearly defined mechanism for tracking
   changes to registry data is essential.

7.  Data Encoding

   Since data may need to traverse administrative domain boundaries some
   thought needs to be given to the rendering of the messages in
   transmission.  The encoding mechanism MUST be robust and easy to
   design and troubleshoot with a strong bias towards an existing and
   widely recognized standard.

8.  Data Management

   Due to the entrenchment of legacy software development processes
   (e.g.  SOAP/XML, WSDL, TLS) it is of utmost importance that whatever
   emerges from this WG should be easy to implement with existing

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9.  Data Propegation

   The transport layer is strictly point-to-point, with no caching or

10.  Querying The Registry

   The definition of the registry query mechanism is out of scope for
   the PEPPERMINT activity.  However, it is helpful to know what
   mechanisms are in popular use to understand the necessary properties
   for a provisioning interface.  At present, there are two well-known
   methods used by VSPs to query a peering registry.  These are ENUM
   [RFC3761] and SIP [RFC3261].

   ENUM is simply a method of using DNS.  It allows a VSP to query a
   registry with a telephone number, an E.164 number in most cases, and
   retrieve a list of URIs, each with a specific preference order.

   When SIP is used for the query mechanism, the numbering registry
   functions as a SIP redirect proxy [RFC3261] .  The input to this
   mechanism is a URI or more importantly the UserInfo part of the URI
   containing the number to be queried.  The response returned by the
   proxy is either an error code indicating the absence of information
   about the number queried or a redirect response (3XX) containing 1
   (or more) Contact Headers representing available routing options.

11.  Control

   Since it may be possible to both push and pull data it is imperative
   that a throttling mechanism exist to control the flow of data
   exchange at all levels.

12.  Existing Technologies

   there has been some consideration to EPP extensions for ENUM
   [RFC4114], and why it has not been adopted and why a requirements
   document is now being produced to cover what would seemingly be
   addressed by that solution.

   There are two reasons for EPP not being adopted.  One is that it
   isn't compatible with legacy participants.  The other reason is that
   it requires more implementation work.

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   Legacy participants have an existing base of software development
   built around SOAP/XML and WSDL, and are familiar with TLS.
   Approaches to ENUM registry interfaces that use these tools will
   blend more easily into the software products already in use to manage
   telephone numbers.

   The use of SOAP permits automatic generation of software to handle
   the client side of the exchange.  Domain name registries had to
   provide software tool kits to give to registrars to match this
   functionality.  When a change is made to EPP, there will be a lot of
   software exchanged.

   From experience with both EPP and SOAP based approaches to registry
   software, the SOAP based approach is much easier on the software
   engineering process.  The difference between the approaches is not
   seen in a protocol analysis, but in an analysis of software

13.  Security Considerations

   Security is to be implemented in the applications exchanging data,
   the requirements here are meant to say that relevant security data
   will be exchanged in the building of the transport.  Specifically,
   data integrity, authentication and secrecy.  (Please note that all
   three of these can be provided by using TLS, with the certificate
   handshake being used by the application to complete the security

14.  IANA Considerations


15.  Acknowledgements

   Many of the points of information in this document are summarizations
   of objectives and statements made by individuals on the PEPPERMINT
   and SPEERMINT mailing lists.  We would also like to acknowledge
   Jeremy Barkan and Otmar Lendl for providing insightful inputs to the
   original draft.  Information on the PEPPERMINT mailing list can be
   found at http://www.ietf.org/mailman/listinfo/peppermint.

16.  References

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16.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC3261]  Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
              A., Peterson, J., Sparks, R., Handley, M., and E.
              Schooler, "SIP: Session Initiation Protocol", RFC 3261,
              June 2002.

16.2.  Informational References

   [RFC1034]  Mockapetris, P., "Domain names - concepts and facilities",
              STD 13, RFC 1034, November 1987.

   [RFC1035]  Mockapetris, P., "Domain names - implementation and
              specification", STD 13, RFC 1035, November 1987.

   [RFC3403]  Mealling, M., "Dynamic Delegation Discovery System (DDDS)
              Part Three: The Domain Name System (DNS) Database",
              RFC 3403, October 2002.

   [RFC3730]  Hollenbeck, S., "Extensible Provisioning Protocol (EPP)",
              RFC 3730, March 2004.

   [RFC3761]  Faltstrom, P. and M. Mealling, "The E.164 to Uniform
              Resource Identifiers (URI) Dynamic Delegation Discovery
              System (DDDS) Application (ENUM)", RFC 3761, April 2004.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, January 2005.

   [RFC4114]  Hollenbeck, S., "E.164 Number Mapping for the Extensible
              Provisioning Protocol (EPP)", RFC 4114, June 2005.

   [RFC4366]  Blake-Wilson, S., Nystrom, M., Hopwood, D., Mikkelsen, J.,
              and T. Wright, "Transport Layer Security (TLS)
              Extensions", RFC 4366, April 2006.

   [RFC4769]  Livingood, J. and R. Shockey, "IANA Registration for an
              Enumservice Containing Public Switched Telephone Network
              (PSTN) Signaling Information", RFC 4769, November 2006.

              Malas, D. and D. Mayer, "SPEERMINT Terminology",
               draft-ietf-speermint-terminology-15.txt, November 2007.

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Authors' Addresses

   David Schwartz
   XConnect Global Networks
   Malcha Technology Park
   Building # 1
   Jerusalem  90961

   Phone:  +972 52 347 4656
   Email:  dschwartz@xconnect.net
   URI:    www.kayote.com

   Rohan Mahy

   Email:  rohan@ekabal.com
   URI:    www.plantronics.com

   Alan Duric

   Email:  alan.duric@telio.no
   URI:    www.telio.no

   Edward Lewis
   46000 Center Oak Plaza
   Building # 1
   Sterling, VA  20166

   Phone:  +1-571-434-5468
   Email:  ed.lewis@neustar.biz
   URI:    www.neustar.biz

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Full Copyright Statement

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