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 IPTEL Working Group                                            James Yu
 Internet Draft                                            NeuStar, Inc.
 Expires: September 18, 2004                              March 18, 2004
 
 
     New Parameters for the "tel" URI to Support Number Portability
                       <draft-ietf-iptel-tel-np-00.txt>
 
 
 Status of this Memo
 
    This document is an Internet-Draft and is in full conformance with
    all provisions of Section 10 of RFC2026.
 
    Internet-Drafts are working documents of the Internet Engineering
    Task Force (IETF), its areas, and its working groups. Note that
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    The list of current Internet-Drafts can be accessed at
    http://www.ietf.org/ietf/1id-abstracts.txt.
 
    The list of Internet-Draft Shadow Directories can be accessed at
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 Copyright Notice
 
    Copyright (C) The Internet Society (2004).  All rights reserved.
 
 
 ABSTRACT
 
    This document defines several new parameters in the "tel" Uniform
    Resource Locator (URL) to support number portability (NP) for
    geographical telephone numbers and freephone numbers.  The “rn”
    parameter carries the routing number for a ported geographical
    telephone number.  The presence of the “npdi” parameter indicates
    that NP database dip has been performed on a geographical telephone
    number.  The “cic” parameter identifies the freephone service
    provider for a freephone number.
 
 
 
 
 
 
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 1. Introduction
 
    Number portability (NP)[1] allows the telephony subscribers to keep
    their telephone numbers when they change service provider (service
    provider portability), move to a new location (location
    portability), or change the subscribed services (service
    portability).  The NP implementations in many countries presently
    support service provider portability for geographic telephone
    numbers and freephone numbers (e.g., 800 numbers in the North
    America).  It has been identified that NP has impacts on several
    works-in-progress at the IETF.  One impact is the need to carry the
    NP-related information in the “tel” URI[2] for protocols such as
    the Session Initiation Protocol (SIP)[3] and H.323[4] after the NP
    database dip has been performed.  Another impact is for a Voice
    over IP (VoIP) server to use the NP-related information in a
    received “tel” URI to determine routing.
 
    A routing number is associated with a geographical telephone number
    that has been ported out from a donor carrier to another carrier.
    A donor carrier is the initial carrier where a geographical
    telephone number was located before ever being ported.  A “non-
    ported” geographical telephone number does not have any routing
    number associated with it because the first N digits of the
    geographical telephone number can be used for routing.  A routing
    number can also be used to indicate the switch or network node that
    originates a call or service similar to the Jurisdiction
    Information Parameter in Signaling System Number 7 (SS7) Integrated
    Services Digital Network User Part (ISUP).
 
    The NP database dip indicator is used to inform the downstream
    servers or switches during call set up that there is no need to
    perform the NP database dip for a geographical telephone number
    again.
 
    A “Carrier Identification Code (CIC)” identifies the current
    freephone service provider for a freephone number.  This parameter
    can be used to carry the pre-subscribed or dialed long distance
    carrier information; however, that is outside the scope of this
    document.
 
    This document defines several new parameters in the "tel" Uniform
    Resource Locator (URL)[2] to support NP.  Section 2 lists the
    abbreviations used in this document.  Section 3 provides the syntax
    definition.  Section 4 describes the rules for a network node that
    deals with some or all of the defined parameters in a “tel” URI.
    Section 5 provides a few examples to show how those defined
    parameters are added to a “tel” URI after retrieving NP-related
    information from the NP database.
 
    The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
    "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in
    this document are to be interpreted as described in RFC2119[5].
 
 
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 2. Abbreviations
 
    ANSI   American National Standards Institute
    CIC    Carrier Identification Code (also cic)
    CIP    Carrier Identification Parameter
    FCI    Forward Call Indicator
    GAP    Generic Address Parameter
    IC     Identification Code
    IP     Internet Protocol
    IETF   Internet Engineering Task Force
    IP     Internet Protocol
    ISUP   Integrated Services Digital Network User Part
    JIP    Jurisdiction Information Parameter
    NP     Number Portability
    NPDB   Number Portability Database
    npdi   NP database dip indicator
    rn     Routing Number
    PSTN   Public Switched Telephone Network
    PNTI   Ported Number Translation Indicator
    SIP    Session Initiation Protocol
    SS7    Signaling System Number 7
    URL    Uniform Resource Locator
    VoIP   Voice over IP
 
 
 3. Syntax Definition
 
    The parameters defined for the “tel” URI to support NP has the
    following syntax:
 
    rn                      = *1(routing-number)
    npdi                    = *1(npdb-dip-indicator)
    cic                     = *1(carrier-id-code)
 
    routing-number          = "rn=" global-rn / local-rn
    global-rn               = "+" 1*phonedigit-hex
    local-rn                = 1*phonedigit-hex rn-context
    rn-context              = “;rn-context=” rn-descriptor
    rn-descriptor           = domainname / global-hex-digits
    global-hex-digits       = "+" 1*3(phonedigit) *phonedigit-hex
    npdi-dip-indicator      = "npdi"
    carrier-id-code         = "cic=" global-cic / local-cic
    global-cic              = "+" 1*phonedigit-hex
    local-cic               = 1*phonedigit-hex cic-context
    cic-context             = “;cic-context=” rn-descriptor
 
    The “routing-number,” “npdb-dip-indicator” or “carrier-id-code”
    each can appear in the “tel” URI at most once.
 
    For a “global-rn”, the routing number information after “+” MUST
    begin with a valid E.164[6] country code.
 
 
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    For a “local-rn”, the routing number in the “rn” parameter MUST be
    meaningful in terms of “rn-context”.  For example, if a national
    routing number is in the “rn” parameter, the “rn-context” MUST
    contain a valid E.164 country code after “+” if it is in the
    “global-hex-digits” format.
 
    For a “global-cic”, the CIC information after “+” MUST begin with a
    valid E.164 country code.
 
    For a “local-cic,” the CIC value in the “cic” parameter MUST be
    meaningful in terms of “cic-context”.  For example, if the national
    CIC value is in the “cic” parameter, the “cic-context” SHALL
    contain a valid E.164 country code after “+”if it is in the
    “global-hex-digits” format.
 
 
 4. Normative Rules
 
    This section discusses how a network node handles a received “tel”
    URI that contains one or more of the defined parameters or has
    accessed an NP database for a freephone number or geographical
    telephone number and needs to adds some of the defined parameters
    to a “tel” URI.
 
    In countries where there is no freephone number portability or
    geographical telephone number portability, the call routing can be
    based on the leading digits of the freephone number or geographical
    telephone number.  This document does not describe those scenarios.
 
    Please note that two accesses to the freephone databases are
    normally done for routing a call to a freephone number.  The first
    one is done by the originating network that queries a freephone
    database for the CIC information so that the call can be routed to
    the serving freephone service provider of the called freephone
    number.  When the call reaches the serving freephone provider, the
    second database access is performed to map the freephone number to
    a geographical telephone number and/or internal routing
    information.  This document does not address the case where
    internal routing information is returned.
 
    The first freephone database contains the CIC information for all
    the active freephone numbers while the second one usually contains
    mapping information only for those freephone numbers served by a
    freephone service provider.  Because the originating carrier may
    provide freephone service, its freephone database would contain the
    CIC information for all the active freephone numbers plus the
    mapping information for those freephone numbers it serves.  This
    document refers the two database accesses as “the first freephone
    database access” and “the second freephone database access.”
 
 
 
 
 
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 4.1 Handling “tel” URI with Defined Parameter or Parameters
 
    If the “tel” URI contains the “npdi” parameter, the network node
    SHALL NOT retrieve the NP-related information for geographical
    telephone numbers even if it is set to do so.
 
    If the “tel” URI contains the “cic” parameter whose CIC value is
    different from the one this network node is associated with, this
    network node SHALL NOT retrieve the NP-related information for the
    geographical telephone number or perform the first freephone
    database access for the freephone number in the “tel” URI.
 
    For the “cic” and “rn” parameters and either a freephone number or
    geographical telephone number, the order of processing is to look
    for the “cic” parameter first for call routing.  If the CIC
    information is not useful or the “cic” parameter does not exist,
    then the next step is to look for the “rn” parameter.  If the
    information in the “rn” parameter is not useful or the “rn”
    parameter does not exist, then the freephone number or geographical
    telephone number is used.
 
    When looking for the “cic” parameter and that parameter exists in
    the “tel” URI:
 
    - The network node SHALL ignore the “cic” parameter if it
      identifies a carrier or service provider associated with that
      node, or if that parameter contains a code for indicating that a
      geographic number is supplied (e.g., +1-0110 means “local,
      translated geographical telephone number provided”).  The network
      node SHALL remove the “cic” parameter and look for the “rn”
      parameter for making the routing decision.
 
    - Otherwise, the network node SHALL make the routing decision based
      on the CIC.  The network node SHALL NOT remove the “cic”
      parameter unless it is handing over the call to the carrier or
      service provider identified by the CIC and the local policies
      require it to remove the “cic” parameter.   How the call is
      actually routed based on the CIC value in the “cic” parameter is
      outside the scope of this document.
 
    When looking for the “rn” parameter and that parameter exists in
    the “tel” URI:
 
    - The network node SHALL ignore the “rn” parameter if the routing
      number points to this network node or a network this network node
      is in (e.g., in some countries the routing number gets the call
      to the serving carrier network where another NP database access
      is required to locate the serving switch), this network node
      SHALL remove the “rn” parameter and look for the freephone number
      or geographical telephone number for making the routing decision.
 
    - Otherwise, the network node SHALL make the routing decision based
      on the routing number in the “rn” parameter.  How the call is
 
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      actually routed based on the routing number in the “rn” parameter
      is outside the scope of this document.
 
    When the “cic” or “rn” parameter is not used for routing, the
    network node uses the freephone number or geographical telephone
    number for making routing decision.  It may access the NP database
    if it is set to do so or may route the call to a designated network
    node that will access the NP database or may route the call based
    on the local routing table.  How the call is handled at this stage
    is outside the scope of this document.  See Section 4.2 for rules
    in adding the defined parameter or parameters to the “tel” URI if
    the network node is set to access the NP database.
 
 
 4.2 Adding Defined Parameter or Parameters to the “tel” URI
 
    There are two cases in terms of NP database access.  One is for a
    geographical telephone number and the other is for a freephone
    number.  They are discussed in Sections 4.2.1 and 4.2.2 for a “tel”
    URI that is used for routing.
 
    Section 4.2.3 discusses a special case where the “rn” parameter is
    added to a “tel” URI that is associated with the first network node
    that handles the call request from the caller.  Section 4.3.4
    discusses the addition of the defined parameter or parameters to
    the “tel” URI due to protocol conversion.
 
 
 4.2.1 Retrieving NP-related information for a geographical telephone
       number
 
    When a network node accesses an NP database for a geographical
    telephone number:
 
    - If the network node retrieves a routing number, it SHALL add the
      “rn” parameter to the “tel” URI to carry the routing number
      information in the “global-rn” or “local-rn” format and SHALL add
      the “npdi” parameter.
 
    - If the network node does not retrieve a routing number (e.g., for
      a non-ported geographical telephone number), it SHALL add the
      “npdi” parameter to the “tel” URI.
 
    The network node SHALL follow the rules described in Section 4.1
    for using the information in the “tel” URI to make the routing
    decision.
 
 
 4.2.2 Retrieving NP-related information for a freephone number
 
    When a network node performs the first or second freephone database
    access for a freephone number:
 
 
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    - If the network node retrieves a CIC that identifies a carrier or
       service provider associated with that network node, or indicates
       that a geographic number is supplied (e.g., “+1-0110” means
       “local, translated geographical telephone number provided”), it
       would have retrieved a geographical telephone number.  The
       network node SHALL NOT add the “cic” parameter and SHALL replace
       the freephone number in the “tel” URI with the retrieved
       geographical telephone number in either the “global-number” or
       “local-number” format.
 
      Some freephone databases may not return the geographical
      telephone number but internal routing information in a
      proprietary format (e.g., switch ID and trunk group ID).  That
      case is outside the scope of this document.
 
    - If the network node retrieves a CIC that belongs to another
      freephone service provider, the network node SHALL add the “cic”
      parameter to the “tel” URI that contains the CIC in the “global-
      cic” or “local-cic” format.
 
      The originating carrier may have business agreements with a
      freephone service provider to return the geographical telephone
      number in addition to the CIC.  When a geographical telephone
      number is returned, the network node SHALL replace the freephone
      number in the “tel” URI with the returned geographical telephone
      number in either the “global-number” or “local-number” format.
 
    - If the network node retrieves a geographical telephone number
      that is the typical case for the second freephone database
      access, the network node SHALL replace the freephone number in
      the “tel” URI with the retrieved geographical telephone number in
      either the “global-number” or “local-number” format.
 
    When a geographical telephone number is returned in the response,
    it is possible that the NP-related information for that
    geographical telephone number could also be returned.  In that
    case, the network node SHALL add the “npdi” parameter and SHALL add
    the “rn” parameter to contain the routing number in either the
    “global-rn” or “local-rn” format only when the routing number is
    available.
 
    The network node SHALL follow the rules described in Section 4.1
    for using the information in the “tel” URI to make the routing
    decision.
 
 
 4.2.3 Adding location information about the caller
 
    In SS7 ISUP, the JIP identifies the switch that originates the call
    and the information in it may be used by the serving carrier to
    determine the call charge to the caller or by the involved carriers
    to determine the settlement amount between them.
 
 
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    A network node that is the first to handle the call request from
    the caller MAY include the “rn” parameter to the “tel” URI
    associated with the caller, if one exists.
 
 
 4.2.4 Adding the defined parameter or parameters due to protocol
       conversion
 
    A Public Switched Telephone Network (PSTN) gateway needs to convert
    between SS7 ISUP and the VoIP protocol such as SIP or H.323.  This
    type of network node SHALL add the corresponding information from
    the ISUP to the defined parameters to the “tel” URI for routing and
    the “tel” URI associated with the caller and vice versa.  Since
    ISUP support for NP depends on the supporting country, the
    following discussion applies to a situation when a network node is
    to map the NP information in the American National Standards
    Institute (ANSI) ISUP to the NP-related parameters in the “tel”
    URI.
 
    For a ported geographical telephone number, the network node SHALL
    convert the routing number in the ISUP Called Party Number
    parameter to a routing number in either the “global-rn” or “local-
    rn” format and carry it in the "rn" parameter for a “tel” URI that
    is used for routing.   The network node SHALL convert the phone
    number that is marked as the "ported number" in the ISUP Generic
    Address Parameter (GAP) to a phone number in either the “global-
    number” or “local-number” format[2] and put it after "tel:" in the
    “tel” URI that is used for routing.
 
    For a non-ported geographical telephone number, the network node
    SHALL convert the phone number in the ISUP Called Party Number
    parameter to a phone number in either the “global-number” or
    “local-number” format and put it after "tel:" in the “tel” URI that
    is used for routing.   No “rn” will appear in the “tel” URI.
 
    The network node SHALL include the “npdi” parameter in the “tel”
    URI that is used for routing when the Ported Number Translation
    Indicator (PNTI) bit in the Forward Call Indicator (FCI) parameter
    is set to "1."
 
    The network node SHALL include the "cic" parameter in either the
    “global-cic” or “local-cic” format in the “tel” URI that is used
    for routing when the ISUP Carrier Identification Parameter (CIP) is
    present.
 
    The network node SHALL include the “rn” parameter in the “tel” URI
    associated with the caller information when the ISUP JIP is
    present.
 
    Mapping NP-related parameters in a “tel” URI to the NP-related
    information in the ISUP message depends on the national ISUP
    implementation and is outside the scope of this document.
 
 
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 5. Examples
 
    A. A “tel” URI, tel:+1-800-123-4567, contains a freephone number
       “+1-800-123-4567.”  Assume that this freephone number is served
       by a freephone service provide with a CIC “+1-6789.”   After
       retrieving the NP-related information, the “tel” URI would be
       set to
 
          tel:+1-800-123-4567;cic=+1-6789
 
    B. A “tel” URI, tel:+1-800-123-4567;cic=+1-6789, is handled by a
       network node in the serving freephone service provider’s
       network.  Assume that the freephone number is mapped to a
       geographical telephone number “+1-202-533-1234.”  After
       retrieving the NP-related information, the “tel” URI would be
       set to
 
          tel:+1-202-533-1234
 
    C. A “tel” URI, tel:+1-202-533-1234, contains a geographical
       telephone number “+1-202-533-1234.”  Assume that this
       geographical telephone number is ported and is associated with a
       routing number “1-202-544-0000.”   After retrieving the NP-
       related information, the “tel” URI would be set to
 
          tel:+1-202-533-1234;rn=+1-202-544-0000;npdi
 
    D. A “tel” URI, tel:+1-202-533-6789, contains a geographical
       telephone number “+1-202-533-6789.”  Assume that this
       geographical telephone number is not ported.   After accessing
       the NP database, the “tel” URI would be set to
 
          tel:+1-202-533-6789;npdi
 
 
 6. Security Considerations
 
    In addition to those security implications discussed in the revised
    “tel” URI[2], there are new security implications associated with
    the defined parameters.
 
    If the value of the “rn” or “cic” in the “tel” URI is changed
    illegally when the signaling message carrying the “tel” URI is en
    route to the destination entity, the signaling message or call may
    be routed to the wrong network or network node causing the call
    setup to be rejected.
 
    If the “npdi” is illegally inserted into the “tel” URI when the
    signaling message carrying the “tel” URI is en route to the
    destination entity, the call may be routed to the wrong network or
    network node causing the call setup to be rejected.  It is less a
    problem if the “npdi” is illegally removed.  An additional NPDB
 
 
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    query may be performed to retrieve the routing number information
    and have the “npdi” included again.
 
    Protocols carrying the “tel” URI MAY need to ensure message
    integrity during the message transfer between two communicating
    network nodes so as to detect any unauthorized changes to the
    content of the “tel” URI and other information.
 
 
 7. IANA Considerations
 
    The fourteen parameters defined in this document are to be
    registered with IANA as the new parameters to the “tel” URI[2].
 
    1. Parameter name – rn
       Applicability – used to carry a routing number
       Mandatory or optional – optional
       Restrictions on syntax – see Section 3
       Reference to a specification – defined in this document
 
    2. Parameter name – npdi
       Applicability – its presence indicates that NPDB dip for a
       geographical telephone number has been performed
       Mandatory or optional – optional
       Restrictions on syntax – see Section 3
       Reference to a specification – defined in this document
 
    3. Parameter name – cic
       Applicability – used to carry a Carrier ID Code
       Mandatory or optional – optional
       Restrictions on syntax – see Section 3
       Reference to a specification – defined in this document
 
    4. Parameter name – routing-number
       Applicability – used to carry a routing number
       Mandatory or optional – optional
       Restrictions on syntax – see Section 3
       Reference to a specification – defined in this document
 
    5. Parameter name – global-rn
       Applicability – used to carry an international routing number
       with a leading “+”
       Mandatory or optional – optional
       Restrictions on syntax – see Section 3
       Reference to a specification – defined in this document
 
 
 
 
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    6. Parameter name – local-rn
       Applicability – used to carry a routing number in the format
       defined by “rn-context”
       Mandatory or optional – optional
       Restrictions on syntax – see Section 3
       Reference to a specification – defined in this document
 
    7. Parameter name – rn-context
       Applicability – used to define a routing number in the “local-
       rn” format
       Mandatory or optional – optional
       Restrictions on syntax – see Section 3
       Reference to a specification – defined in this document
 
    8. Parameter name – rn-descriptor
       Applicability – used to define a number in the “local-rn” format
       or other applicable formats such as the “local-cic” format
       Mandatory or optional – optional
       Restrictions on syntax – see Section 3
       Reference to a specification – defined in this document
 
    9. Parameter name – global-hex-digits
       Applicability – used to define an international number with a
       leading “+” where hex-decimal digit is allowed after a valid
       E.164 country code
       Mandatory or optional – optional
       Restrictions on syntax – see Section 3
       Reference to a specification – defined in this document
 
    10.
       Parameter name – npdi-dip-indicator
       Applicability – its presence indicates that NPDB dip for a
       geographical telephone number has been performed
       Mandatory or optional – optional
       Restrictions on syntax – see Section 3
       Reference to a specification – defined in this document
 
    11.
       Parameter name – carrier-id-code
       Applicability – used to carry a Carrier ID Code
       Mandatory or optional – optional
       Restrictions on syntax – see Section 3
       Reference to a specification – defined in this document
 
    12.
       Parameter name – global-cic
       Applicability – used to carry a Carrier ID Code with a leading
       “+”
       Mandatory or optional – optional
       Restrictions on syntax – see Section 3
 
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       Reference to a specification – defined in this document
 
    13.
       Parameter name – local-cic
       Applicability – used to carry a Carrier ID Code in the format
       described by “cic-context”
       Mandatory or optional – optional
       Restrictions on syntax – see Section 3
       Reference to a specification – defined in this document
 
    14.
       Parameter name – cic-context
       Applicability – used to define a Carrier ID Code in the “local-
       cic” format
       Mandatory or optional – optional
       Restrictions on syntax – see Section 3
       Reference to a specification – defined in this document
 
 
 8. Normative References
 
    [1] M. Foster, T. McGarry and J. Yu, RFC3482, "Number Portability
         in the GSTN: An Overview," February 2003.
 
    [2] H. Schulzrinne and A. Vaha-Sipila, "The tel URI for Telephone
         Calls," draft-ietf-iptel-rfc2806bis-04.txt, February 15, 2004.
 
    [3] J. Rosenberg, et al., RFC3261, "SIP: Session Initiation
         Protocol," June 2002.
 
    [4] ITU-T Recommendation H.323, "Packet-Based Multimedia
         Communications Systems," November 2000.
 
    [5] Scott Bradner, RFC2119," Key words for use in RFCs to Indicate
         Requirement Levels," March 1997.
 
    [6] ITU-T Recommendation E.164, "The international public
         telecommunication numbering plan," May 1997.
 
 9. Acknowledgements
 
    The author would like to thank Penn Pfautz, Jon Peterson, Jonathan
    Rosenberg, Henning Schulzrinne, Antti Vaha-Sipila, Flemming
    Andreasen and Mike Hammer for their discussions and comments.
 
 
 
 
 
 
 
 
 
 
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 10. Author's Address
 
     James Yu
     NeuStar, Inc.
     46000 Center Oak Plaza
     Sterling, VA 20166
     U.S.A.
     Phone: +1-571-434-5572
     Email: james.yu@neustar.biz
 
 
 
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 Acknowledgement
 
    Funding for the RFC Editor function is currently provided by the
    Internet Society.
 
 
 
 
 
 James Yu              Expired on September 18, 2004          [Page 13]
 

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