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Versions: (RFC 3603) 00 01 02 03 04 05 06 07 RFC 5503

     SIPPING Working Group                                       W. Marshall
     Internet Draft                                                     AT&T
     Expires: December 2006                                     F. Andreasen
                                                                       Cisco
                                                                 B. McKibben
                                                                   CableLabs
                                                               June 17, 2006
     
     
     Private Session Initiation Protocol (SIP) Proxy-to-Proxy Extensions for
        Supporting the PacketCable Distributed Call Signaling Architecture
                    draft-andreasen-sipping-rfc3603bis-00.txt
     
     
     Status of this Memo
     
        By submitting this Internet-Draft, each author represents that
        any applicable patent or other IPR claims of which he or she is
        aware have been or will be disclosed, and any of which he or she
        becomes aware will be disclosed, in accordance with Section 6 of
        BCP 79.
     
        Internet-Drafts are working documents of the Internet Engineering
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        The list of Internet-Draft Shadow Directories can be accessed at
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        This Internet-Draft will expire on December 17, 2006.
     
     Abstract
     
        In order to deploy a residential telephone service at very large
        scale across different domains, it is necessary for trusted elements
        owned by different service providers to exchange trusted information
        that conveys customer-specific information and expectations about the
        parties involved in the call.  This document describes private
        extensions to the Session Initiation Protocol (SIP) (RFC3261) for
        supporting the exchange of customer information and billing
     
     
     
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        information between trusted entities in the PacketCable Distributed
        Call Signaling Architecture.  These extensions provide mechanisms for
        access network coordination to prevent theft of service, customer
        originated trace of harassing calls, support for operator services
        and emergency services, and support for various other regulatory
        issues.  The use of the extensions is only applicable within closed
        administrative domains, or among federations of administrative
        domains with previously agreed-upon policies where coordination of
        charging and other functions is required.
     
     Table of Contents
     
     
        1. Applicability Statement........................................3
        2. Introduction...................................................3
        3. Trust Boundary.................................................5
        4. Conventions used in this document..............................6
        5. P-DCS-TRACE-PARTY-ID...........................................7
           5.1. Syntax....................................................7
           5.2. Procedures at an Untrusted User Agent Client (UAC)........8
           5.3. Procedures at a Trusted User Agent Client (UAC)...........8
           5.4. Procedures at an Untrusted User Agent Server (UAS)........8
           5.5. Procedures at a Trusted User Agent Server (UAS)...........9
           5.6. Procedures at Proxy.......................................9
              5.6.1. Procedures at Originating Proxy......................9
              5.6.2. Procedures at Terminating Proxy......................9
        6. P-DCS-OSPS....................................................10
           6.1. Syntax...................................................10
           6.2. Procedures at an Untrusted User Agent Client (UAC).......11
           6.3. Procedures at a Trusted User Agent Client (UAC)..........11
           6.4. Procedures at an Untrusted User Agent Server (UAS).......11
           6.5. Procedures at a Trusted User Agent Server (UAS)..........12
           6.6. Procedures at Proxy......................................12
        7. P-DCS-BILLING-INFO............................................12
           7.1. Syntax...................................................14
           7.2. Procedures at an Untrusted User Agent Client (UAC).......16
           7.3. Procedures at a Trusted User Agent Client (UAC)..........16
           7.4. Procedures at an Untrusted User Agent Server (UAS).......16
           7.5. Procedures at a Trusted User Agent Server (UAS)..........16
           7.6. Procedures at Proxy......................................17
              7.6.1. Procedures at Originating Proxy.....................17
              7.6.2. Procedures at Terminating Proxy.....................18
              7.6.3. Procedures at Tandem Proxy..........................19
        8. P-DCS-LAES and P-DCS-REDIRECT.................................19
           8.1. Syntax...................................................20
           8.2. Procedures at an Untrusted User Agent Client (UAC).......21
           8.3. Procedures at a Trusted User Agent Client (UAC)..........21
     
     
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           8.4. Procedures at an Untrusted User Agent Server (UAS).......22
           8.5. Procedures at a Trusted User Agent Server (UAS)..........22
           8.6. Procedures at Proxy......................................23
              8.6.1. Procedures at Originating Proxy.....................23
              8.6.2. Procedures at Terminating Proxy.....................25
        9. Security Considerations.......................................26
        10. IANA Considerations..........................................26
        11. Change Log...................................................27
           11.1. Changes in -00 since RFC 3603...........................27
        12. To Do........................................................27
        13. References...................................................27
           13.1. Normative References....................................27
           13.2. Informative References..................................28
        14. Acknowledgements.............................................28
        Author's Addresses...............................................30
        Intellectual Property Statement..................................30
        Disclaimer of Validity...........................................31
        Copyright Statement..............................................31
        Acknowledgment...................................................31
     
     
     1. Applicability Statement
     
        The SIP extensions described in this document make certain
        assumptions regarding network topology, linkage between SIP and lower
        layers, and the availability of transitive trust.  These assumptions
        are generally not applicable in the Internet as a whole.  The use of
        these headers is only applicable within closed administrative
        domains, or among federations of administrative domains with
        previously agreed-upon policies where coordination of charging and
        other functions is required, as in for example the architecture
        presented in [DCSARCH].  Use outside such a domain could result in
        the leakage of potentially sensitive or private information.  User
        consent to the privacy implications of the policies in [DCSARCH] is
        strongly encouraged in those domains as well.
     
        Although RFC 2119 language is used in this document, the scope of the
        normative language is only for the area of applicability of the
        document and, like the technology, it does not apply to the general
        Internet.
     
     2. Introduction
     
        In order to deploy a SIP-based [RFC3261] residential telephone
        service at very large scale across different domains, it is necessary
        for trusted elements owned by different service providers to exchange
     
     
     
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        trusted information that conveys billing information and expectations
        about the parties involved in the call.
     
        There are many billing models used in deriving revenue from telephony
        services today.  Charging for telephony services is tightly coupled
        to the use of network resources.  It is outside the scope of this
        document to discuss the details of these numerous and varying
        methods.
     
        A key motivating principle of the DCS architecture described in
        [DCSARCH] is the need for network service providers to be able to
        control and monitor network resources; revenue may be derived from
        the usage of these resources as well as from the delivery of enhanced
        services such as telephony.  Furthermore, the DCS architecture
        recognizes the need for coordination between call signaling and
        resource management. This coordination ensures that users are
        authenticated and authorized before receiving access to network
        resources and billable enhanced services.
     
        DCS Proxies, as defined in [DCSARCH], have access to subscriber
        information and act as policy decision points and trusted
        intermediaries along the call signaling path.  Edge routers provide
        the network connectivity and resource policy enforcement mechanism
        and also capture and report network connectivity and resource usage
        information.  Edge routers need to be given billing information that
        can be logged with Record Keeping or Billing servers.  The DCS Proxy,
        as a central point of coordination between call signaling and
        resource management, can provide this information based on the
        authenticated identity of the calling and called parties.  Since
        there is a trust relationship among DCS Proxies, they can be relied
        upon to exchange trusted billing information pertaining to the
        parties involved in a call.  See [DCSARCH] for a description of the
        trust boundary and trusted versus untrusted entities.
     
        For these reasons, it is appropriate to consider defining SIP header
        extensions to allow DCS Proxies to exchange information during call
        setup.  It is the intent that the extensions would only appear on
        trusted network segments, should be inserted upon entering a trusted
        network region, and removed before leaving trusted network segments.
     
        Significant amounts of information is retrieved by an originating DCS
        Proxy in its handling of a connection setup request from a user
        agent.  Such information includes location information about the
        subscriber (essential for emergency services calls), billing
        information, and station information (e.g., coin operated phone).  In
        addition, while translating the destination number, information such
     
     
     
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        as the local-number-portability office code is obtained and will be
        needed by all other proxies handling this call.
     
        For Usage Accounting records, it is necessary to have an identifier
        that can be associated with all the event records produced for the
        call.  The SIP Call-ID header field cannot be used as such an
        identifier since it is selected by the originating user agent, and
        may not be unique among all past calls as well as current calls.
        Further, since this identifier is to be used by the service provider,
        it should be chosen in a manner and in a format that meets the
        service provider's needs.
     
        Billing information may not necessarily be unique for each user
        (consider the case of calls from an office all billed to the same
        account).  Billing information may not necessarily be identical for
        all calls made by a single user (consider prepaid calls, credit card
        calls, collect calls, etc).  It is therefore necessary to carry
        billing information separate from the calling and called party
        identification.  Furthermore, some billing models call for split-
        charging where multiple entities are billed for portions of the call.
     
        The addition of a SIP General Header Field allows for the capture of
        billing information and billing identification for the duration of
        the call.
     
        It is the intent that the billing extensions would only appear on
        trusted network segments, and MAY be inserted by a DCS Proxy in
        INVITE and REFER requests and INVITE responses in a trusted network
        segment, and removed before leaving trusted network segments.
     
        In addition to support for billing, current residential telephone
        service includes the need for customer originated trace (of harassing
        or obscene calls), for operator services such as busy line
        verification and emergency interrupt (initiated by an operator from
        an Operator Services Position System (OSPS)), for emergency services
        such as 9-1-1 calls to a Public Service Access Point (PSAP) and the
        subsequent call handling, and support for Electronic Surveillance and
        Law Enforcement access as required by applicable legislation and
        court orders.  In all of these cases, additional information about
        the call and about the subscribers involved in the call needs to be
        exchanged between the proxies.
     
     3. Trust Boundary
     
        The DCS architecture [DCSARCH] defines a trust boundary around the
        various systems and servers that are owned, operated by, and/or
        controlled by the service provider.  These trusted systems include
     
     
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        the proxies and various servers such as bridge servers, voicemail
        servers, announcement servers, etc.  Outside of the trust boundary
        lie the customer premises equipment, and various application and
        media servers operated by third-party service providers.
     
        Certain subscriber-specific information, such as billing and
        accounting information, stays within the trust boundary.  Other
        subscriber-specific information, such as endpoint identity, may be
        presented to untrusted endpoints or may be withheld based on
        subscriber profiles.
     
        The User Agent (UA) may be either within the trust boundary or
        outside the trust boundary, depending on exactly what function is
        being performed and exactly how it is being performed. Accordingly,
        the procedures followed by a User Agent are different depending on
        whether the UA is within the trust boundary or outside the trust
        boundary.
     
        The following sections giving procedures for User Agents therefore
        are subdivided into trusted user agents and untrusted user agents.
     
     4. Conventions used in this document
     
        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 BCP 14, RFC 2119
        [RFC2119].
     
        The term "private-URL" used in this document refers to a SIP URI that
        is generated by a proxy, contains a "hostport" that identifies the
        proxy, and contains a "userinfo" string that is generated by the
        proxy.  The "userinfo" typically contains (or points to) information
        that is not to be disclosed outside the trusted domain of the
        proxies, such as billing account numbers, electronic surveillance
        indication, electronic surveillance parameters, and call redirection
        information.  Consequently, the information is either stored locally
        by the proxy, or encrypted with a private key known only to the proxy
        and encoded in a character string in the "userinfo" portion of the
        URL.  A checksum is included in the "userinfo" data to detect
        tampering.  The mechanism by which a proxy recognizes a "userinfo" as
        a private-URL and decodes and recovers the original information is
        local to the proxy and is not subject to standardization.  Some
        possible implementations include an initial magic cookie (e.g.,
        z9hG4Bk followed by the pointer/information), or use of a reserved
        "user" name (e.g., "private") with the optional "password" containing
        the pointer/information.
     
     
     
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     5. P-DCS-TRACE-PARTY-ID
     
        In the telephone network, calling identity information is used to
        support regulatory requirements such as the Customer Originated Trace
        service, which provide the called party with the ability to report
        obscene or harassing phone calls to law enforcement.  This service is
        provided independently of caller-id, and works even if the caller
        requested anonymity.  The calling party is here identified as the
        station originating the call.  In order for this service to be
        dependable, the called party must be able to trust that the calling
        identity information being presented is valid.  One way to achieve
        this is described in [RFC3325].
     
        To initiate a customer-originated-trace from an untrusted UAC, an
        additional header is defined for the INVITE request.  This header is
        called P-DCS-Trace-Party-ID, and does not appear in any other request
        or response.  The entity addressed by the Request-URI performs the
        service-provider-specific functions of recording and reporting the
        caller identity in the P-DCS-Trace-Party-ID for law enforcement
        action.  It then forwards the call to either an announcement server
        or to the service-provider's business office to collect further
        information about the complaint.  A trusted UAC does not use this
        header, as it initiates this action locally.
     
     5.1. Syntax
     
        The ABNF description of this header is (some terms used in this ABNF
        are defined in [RFC3261]):
     
           P-DCS-Trace-Party-ID = "P-DCS-Trace-Party-ID" HCOLON
                                         name-addr
     
        The ABNF production for name-addr in [RFC3261] includes uri-
        parameters, which allows for additional parameters to be defined
        (other-param). We here define the following other-param parameters to
        be used with P-DCS-Trace-Party-ID:
     
           trace-param       = called-param  ; defined in Section 7.1.
                             / remote-param ; defined in [TDIALOG]
                             / local-param ; defined in [TDIALOG]
                             / timestamp-param
           callid-param      = "call-id" EQUAL called ; called from [RFC3261]
     
           timestamp-
                    -param   = "timestamp" EQUAL 1*DIGIT ["." 1*DIGIT]
     
        This document adds the following entry to Table 2 of [RFC3261]:
     
     
     
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        Header field         where proxy  ACK  BYE  CAN  INV  OPT  REG
        ------------         ----- -----  ---  ---  ---  ---  ---  ---
        P-DCS-Trace-Party-ID   R     dr    -    -    -    o    -    -
     
                                          SUB  NOT  REF  INF  UPD  PRA
                                          ---  ---  ---  ---  ---  ---
                                           -    -    -    -    -    -
     
        The addr-spec contained in name-addr contains a URL that identifies
        the remote endpoint.  Addr-spec typically contains a tel: URL or SIP
        URI giving the identity of the remote endpoint, as provided in the
        signaling messages that established the session to be traced.
     
        The callid-param contains the identifier of the call to be traced. It
        is defined in section 12 of [RFC3261].
     
        The remote-param and local-param contain the dialog ID, as defined in
        [TDIALOG], of the call to be traced. Local and remote is here from
        the point of view of the entity issuing the request.
     
        The timestamp-param contains the time of the call to be traced.
     
     
     5.2. Procedures at an Untrusted User Agent Client (UAC)
     
        The UAC MUST insert a P-DCS-Trace-Party-ID header into the initial
        INVITE message for a customer-originated-trace request.  The UAC MUST
        use a SIP URI in the Request-URI with userinfo set to "call-trace"
        and hostport identifying the call tracing entity for the untrusted
        UA. The UAC MAY insert the callid-param, remote param, local param
        and timestamp if known to the UAC.
     
     
     5.3. Procedures at a Trusted User Agent Client (UAC)
     
        A trusted UAC performs the customer-originated-trace in a manner
        similar to the trusted UAS, described below.  A trusted UAC MUST NOT
        include this header in any request.
     
     
     5.4. Procedures at an Untrusted User Agent Server (UAS)
     
        This header MUST NOT appear in any response sent by a UAS.
     
     
     
     
     
     
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     5.5. Procedures at a Trusted User Agent Server (UAS)
     
        If the P-DCS-Trace-Party-ID header is present in the initial INVITE
        request from a UAC, and the Request-URI of the INVITE has userinfo
        set to "call-trace" and hostport set to the UAS, the UAS MUST perform
        the service-provider-specific functions of recording and reporting
        the caller identity for law enforcement action.  The UAS then MUST
        redirect the call, via a 3xx response, to either an announcement
        server or to the service-provider's business office to collect
        further information about the complaint.
     
        This header MUST NOT appear in any response sent by a UAS.
     
     5.6. Procedures at Proxy
     
        Two sets of proxy procedures are defined: (1) the procedures at an
        originating proxy, and (2) the procedures at a terminating proxy. The
        originating proxy is a proxy that received the INVITE request from a
        non-trusted endpoint.
     
        The terminating proxy is a proxy that sends the INVITE request to a
        non-trusted endpoint.
     
        A proxy that both receives the INVITE request from an untrusted
        endpoint, and sends the INVITE request to an untrusted endpoint,
        performs both sets of procedures.
     
     5.6.1. Procedures at Originating Proxy
     
        If the P-DCS-Trace-Party-ID header is present in the initial INVITE
        request from the UAC, and the Request-URI of the INVITE has userinfo
        other than "call-trace" and hostport set to other than a potentially
        provisioned call tracing entity, then the Proxy MAY reject the
        request, or MAY remove the P-DCS-Trace-Party-ID header from the
        request.  If the header is present in a valid request, and contains a
        private-URL that identifies the Proxy in the hostport, then the
        Originating Proxy SHOULD replace the private-URL with its original
        contents (i.e., the verified identity of the caller of the session
        that is being traced).
     
     5.6.2. Procedures at Terminating Proxy
     
        This header MUST NOT appear in any request or response sent by a
        terminating proxy to an untrusted endpoint.
     
     
     
     
     
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     6. P-DCS-OSPS
     
        Some calls have special call processing requirements that may not be
        satisfied by normal user agent call processing.  For example, when a
        user is engaged in a call and another call arrives, such a call might
        be rejected with a busy indication.  However, some PSTN operator
        services require special call processing.  In particular, the Busy
        Line Verification (BLV) and Emergency Interrupt (EI) services
        initiated by an operator from an Operator Services Position System
        (OSPS) on the PSTN network have such a need.  Similarly, emergency
        calls to a 9-1-1 Public Service Access Point (PSAP) may result in
        trunk signaling causing operator ringback using a howling tone or
        sustained ring on the originating line (country-specific variations
        may exist).
     
        In order to inform the SIP user agent that special treatment should
        be given to a call, we use a new P-DCS-OSPS header field, which may
        be set to a value indicating when a special type of call processing
        is requested.  We define three values in this header, namely "BLV"
        for busy line verification, "EI" for emergency interrupt, and "RING"
        for operator ringback (e.g., howling/sustained tone ring in the US).
     
        If the user agent decides to honor such a request, the response of
        the user agent to an INVITE with either "BLV" or "EI" will not be a
        busy indication.  Since "EI" and "RING" only occur on established
        dialogs, they may also appear in UPDATE requests.
     
     6.1. Syntax
     
        The ABNF description of the P-DCS-OSPS header is as follows (some
        terms used in this ABNF are defined in [RFC3261]):
     
           P-DCS-OSPS      = "P-DCS-OSPS" HCOLON OSPS-Tag
           OSPS-Tag        = "BLV" / "EI" / "RING" / token
     
         This document adds the following entry to Table 2 of [RFC3261]:
     
           Header field         where proxy  ACK  BYE  CAN  INV  OPT  REG
           ------------         ----- -----  ---  ---  ---  ---  ---  ---
           P-DCS-OSPS             R     dr    -    -    -    o    -    -
     
                                             SUB  NOT  REF  INF  UPD  PRA
                                             ---  ---  ---  ---  ---  ---
                                              -    -    -    -    o    -
     
        The OSPS-Tag value of "token" is defined for extensibility, and is
        reserved for future use.
     
     
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     6.2. Procedures at an Untrusted User Agent Client (UAC)
     
        The P-DCS-OSPS header MUST NOT be sent in a request from an untrusted
        UAC.
     
     6.3. Procedures at a Trusted User Agent Client (UAC)
     
        This header is typically only inserted by a Media Gateway Controller
        [DCSARCH] that is controlling a Media Gateway with special trunks to
        a PSTN OSPS system or PSAP.  This trunk group is usually referred to
        as a BLV-trunk group and employs special signaling procedures that
        prevent inadvertent use.  Calls originating at the PSTN OSPS system
        are sent over this trunk group, and result in an INVITE request with
        the P- DCS-OSPS header.
     
        This header MAY be sent in an INVITE request, and MUST NOT appear in
        any message other than those listed below.
     
        OSPS-Tag value "BLV" MUST NOT appear in any request or response other
        than an initial INVITE request establishing a new dialog.
     
        OSPS-Tag value "EI" MUST NOT appear in any request or response other
        than (1) a subsequent INVITE within a pre-existing dialog established
        with the OSPS-Tag value of "BLV", or (2) an UPDATE request within a
        pre-existing dialog established with the OSPS-Tag value of "BLV".
     
        OSPS-Tag value "RING" MUST NOT appear in any request or response
        other than (1) a subsequent INVITE within a pre-existing dialog
        established by a UAC to an operator or PSAP, or (2) an UPDATE request
        within a pre-existing dialog established by a UAC to an operator or
        PSAP.
     
     6.4. Procedures at an Untrusted User Agent Server (UAS)
     
        If the UAS receives an INVITE request with an OSPS-Tag of "BLV",
        dialog identification that matches an existing dialog, and the
        existing call was not established with the OSPS-Tag, it MUST reject
        the request with a 403-Forbidden error code.
     
        If the UAS receives an INVITE/UPDATE request with an OSPS-Tag value
        of "EI" or "RING", with dialog identification that does not match an
        existing dialog, it MUST reject the request with a 403-Forbidden
        response code.
     
        If the UAS receives an INVITE that contains an OSPS-Tag value of
        "BLV" and is not willing to cooperate in offering this service, it
        MUST reject the request with a 403-Forbidden response code.
     
     
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        The UAS SHOULD NOT reject an INVITE with a BLV OSPS-Tag due to a busy
        condition.  The UAS MUST NOT respond with a 3xx-Redirect response
        code to an INVITE with a BLV OSPS-Tag.  The UAS SHOULD NOT alert the
        user of the incoming call attempt if the BLV OSPS-Tag is present in
        the INVITE.
     
        If an INVITE with OSPS-Tag of "BLV" is accepted (e.g., meeting all
        QoS pre-conditions, etc.), the UAS MUST send an audio stream on this
        connection to the address and port given in the SDP of the INVITE.
        The UAS MAY perform a mixing operation between the two ends of an
        existing active call and send the resulting media stream to the
        address and port indicated.  Alternatively, the UAS MAY send a copy
        of the local voice stream, and (if no activity on the local voice
        stream) send a copy of the received voice stream of an existing call.
        If the state of the UAS is idle, the UAS SHOULD send a stream of
        silence packets to OSPS.  If the state of the UAS is ringing or
        ringback, the UAS SHOULD send a ringback stream to OSPS.
     
        If an INVITE/UPDATE with OSPS-Tag of "EI" is accepted, the UAS MUST
        enable communication between the UAC and the local user.  The UAS MAY
        put any existing call on hold, or initiate an ad-hoc conference.
     
        If an INVITE/UPDATE with OSPS-Tag of "RING" is accepted, the UAS MUST
        perform operator ringback in accordance with local procedures, e.g.,
        generate a 3-second howling tone or a sustained ring, depending on
        the state of the user equipment.
     
     6.5. Procedures at a Trusted User Agent Server (UAS)
     
        The procedures at a trusted UAS MUST be identical to those described
        in 6.4.
     
     6.6. Procedures at Proxy
     
        In the DCS architecture, the OSPS is considered a trusted UAC.  If a
        proxy receives a P-DCS-OSPS header in a request from an untrusted
        source, it MUST either remove the header or reject the request with a
        403-Forbidden response.
     
        A proxy that implements a call-forwarding service MUST NOT respond to
        an INVITE request with a 3xx response, if the request contained the
        P-DCS-OSPS header.
     
     7. P-DCS-BILLING-INFO
     
        There are many billing models used in deriving revenue from telephony
        services today.  Charging for telephony services is tightly coupled
     
     
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        to the use of network resources.  It is outside the scope of this
        document to discuss the details of these numerous and varying
        methods.
     
        Proxies have access to subscriber information and act as policy
        decision points and trusted intermediaries along the call signaling
        path.  Edge routers provide the network connection and resource
        policy enforcement mechanism and also capture and report network
        connection and resource usage information.  Edge routers need to be
        given billing information that can be logged with Record Keeping or
        Billing servers.  The proxy, as a central point of coordination
        between call signaling and resource management, can provide this
        information based on the authenticated identity of the calling and
        called parties.  Since there is a trust relationship among proxies,
        they can be relied upon to exchange trusted billing information
        pertaining to the parties involved in a call.
     
        For Usage Accounting records, it is necessary to have an identifier
        that can be associated with all the event records produced for the
        call.  The SIP Call-ID header field cannot be used as such an
        identifier since it is selected by the originating user agent, and
        may not be unique among all past calls as well as current calls.
        Further, since this identifier is to be used by the service provider,
        it should be chosen in a manner and in a format that meets the
        service provider's needs.
     
        Billing information may not necessarily be unique for each user
        (consider the case of calls from an office all billed to the same
        account).  Billing information may not necessarily be identical for
        all calls made by a single user (consider prepaid calls, credit card
        calls, collect calls, etc).  It is therefore necessary to carry
        billing information separate from the calling and called party
        identification.  Furthermore, some billing models call for split-
        charging where multiple entities are billed for portions of the call.
     
        The addition of a SIP General Header Field allows for the capture of
        billing information and billing identification for the duration of
        the call.
     
        It is the intent that the billing extensions would only appear on
        trusted network segments, and MAY be inserted by a proxy or trusted
        UA in INVITE requests in a trusted network segment, and removed
        before leaving trusted network segments.  The P-DCS-Billing-Info
        header extension is used only on requests and responses between
        proxies and trusted User Agents.  It is never sent to, nor sent by,
        an untrusted UA.
     
     
     
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     7.1. Syntax
     
        The DCS-Billing-Info header is defined by the following ABNF (some
        terms used in this ABNF are defined in [RFC3261]):
     
        P-DCS-Billing-Info      = "P-DCS-Billing-Info" HCOLON
                                   Billing-Correlation-ID "/" FEID
                                   *(SEMI Billing-Info-param)
        Billing-Correlation-ID  = 1*48(HEXDIG)
        FEID                    = 1*16(HEXDIG) "@" host
        Billing-Info-param      = RKS-Group-ID-param / Charge-param /
                                  Calling-param / Called-param /
                                  Routing-param / Loc-Routing-param /
                                  JIP-param / generic-param
        RKS-Group-ID-param      = "rksgroup" EQUAL RKS-Group-ID
        RKS-Group-ID            = token
        Charge-param            = "charge" EQUAL Acct-Charge-URI
        Acct-Charge-URI         = LDQUOT addr-spec RDQUOT
        Calling-param           = "calling" EQUAL Acct-Calling-URI
        Acct-Calling-URI        = LDQUOT addr-spec RDQUOT
        Called-param            = "called" EQUAL Acct-Called-URI
        Acct-Called-URI         = LDQUOT addr-spec RDQUOT
        Routing-param           = "routing" EQUAL Acct-Routing-URI
        Acct-Routing-URI        = LDQUOT addr-spec RDQUOT
        Loc-Routing-param       = "locroute" EQUAL Acct-Loc-Routing-URI
        Acct-Loc-Routing-URI    = LDQUOT addr-spec RDQUOT
     
        JIP-param               =  "jip" EQUAL jip
        jip                     = LDQUOT 1*phonedigit-hex jip-context RDQUOT
        jip-context             = ";jip-context=" jip-descriptor
        jip-descriptor          = global-hex-digits
        global-hex-digits       = "+" 1*3 (phonedigit) *phonedigit-hex
        phonedigit              = DIGIT / [ visual-separator ]
        phonedigit-hex          = HEXDIG / "*" / "#" / [ visual-separator ]
        visual -
               - separator      = "-" / "." / "(" / ")"
     
        This document adds the following entry to Table 2 of [RFC3261]:
     
        Header field         where proxy  ACK  BYE  CAN  INV  OPT  REG
        ------------         ----- -----  ---  ---  ---  ---  ---  ---
        P-DCS-Billing-Info         admr    -    -    -    o    -    -
     
     
     
                                          SUB  NOT  REF  INF  UPD  PRA
                                          ---  ---  ---  ---  ---  ---
                                           -    -    -    -    -    -
     
     
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        The P-DCS-Billing-Info extension contains an identifier that can be
        used by an event recorder to associate multiple usage records,
        possibly from different sources, with a billable account.  It further
        contains the subscriber account information, and other information
        necessary for accurate billing of the service.  This header is only
        used between proxies and trusted User Agents.
     
        The Billing-Correlation-ID is specified in [PCEM] as a 24-byte binary
        structure, containing 4 bytes of NTP timestamp, 8 bytes of the unique
        identifier of the network element that generated the ID, 8 bytes
        giving the time zone, and 4 bytes of monotonically increasing
        sequence number at that network element.  This identifier is chosen
        to be globally unique within the system for a window of several
        months.  This MUST be encoded in the P-DCS-Billing-Info header as a
        hexadecimal string of up to 48 characters.  Leading zeroes MAY be
        suppressed.
     
        The Financial-Entity-ID (FEID) is specified in [PCEM] as an 8-byte
        structure, containing the financial identifier for that domain,
        followed by a domain name.  FEID can be associated with a type of
        service and could be assigned to multiple domains by the same
        provider.  A domain could contain multiple assigned FEIDs.  This 8-
        byte structure MUST be encoded in the P-DCS-Billing-Info header as a
        hexadecimal string of up to 16 characters.  Trailing zeroes MAY be
        suppressed.  "Host" contains the domain name.
     
        The RKS-Group-ID specifies a record keeping server (or group of
        cooperating servers) for event messages relating to this call.  It is
        used to control certain optimizations of procedures when multiple
        event message streams are being sent to the same Record Keeping
        Server.
     
        Additional parameters contain the information needed for generation
        of event message records.  Acct-Charge-URI, Acct-Calling-URI, Acct-
        Called-URI, Acct-Routing-URI, and Acct-Location-Routing-URI are each
        defined as URLs; they should all contain tel: URLs with E.164
        formatted addresses.  These fields are further defined in [PCEM]
        under the element identifiers "Charge_Number" (element ID 16),
        "Calling_Party_Number" (element ID 4), "Called_Party_Number" (element
        ID 5), "Routing Number" (element ID 25), and
        "Location_Routing_Number" (element ID 22).
     
        The JIP-param contains the calling jurisdiction information, or
        numbering plan area, of the network in the which the call originated.
        The field is further defined in [PCEM] under the element identifier
        "Jurisdiction_Information_Parameter" (element ID 82).
     
     
     
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     7.2. Procedures at an Untrusted User Agent Client (UAC)
     
        This header is never sent to an untrusted UAC, and is never sent by
        an untrusted UAC.
     
     7.3. Procedures at a Trusted User Agent Client (UAC)
     
        The UAC MUST generate the Billing-Correlation-ID for the call, and
        insert it into the P-DCS-Billing-Info header in the initial INVITE
        message sent to the terminating proxy, along with the charging
        information for the call.  The UAC MUST include its FEID, and the
        RKS-Group-ID for the Record-Keeping-Server being used by the UAC. If
        the UAC performed a Local Number Portability (LNP) query, it MUST
        include the Routing Number and Location Routing Number returned by
        the query.
     
        If the response to the initial INVITE is a 3xx-Redirect, the UAC
        generates a new initial INVITE request to the destination specified
        in the Contact: header, as per standard SIP.  If a UAC receives a
        3xx-Redirect response to an initial INVITE, the new INVITE generated
        by the UAC MUST contain the P-DCS-Billing-Info header from the 3xx-
        Redirect response.  If the UAC is acting as a B2BUA, instead of
        generating a new INVITE it MAY generate a private-URL and place it in
        the Contact header of a 3xx-Redirect response sent to the originating
        endpoint.  This private-URL MUST contain (or contain a pointer to)
        the P-DCS-Billing-Info value, which indicates the charging
        arrangement for the new call, and an expiration time very shortly in
        the future, to limit the ability of the originator to re-use this
        private-URL for multiple calls.
     
        A UAC that includes a Refer-to header in a REFER request MUST include
        a P-DCS-Billing-Info header in the Refer-to's URL.  This P-DCS-
        Billing-Info header MUST include the accounting information of the
        initiator of the REFER.
     
     7.4. Procedures at an Untrusted User Agent Server (UAS)
     
        This header is never sent to an untrusted UAS, and is never sent by
        an untrusted UAS.
     
     7.5. Procedures at a Trusted User Agent Server (UAS)
     
        The UAS MUST include a P-DCS-Billing-Info header in the first
        reliable 1xx (except 100) or 2xx response to an initial INVITE
        message.  This P-DCS-Billing-Info header MUST include the Billing-
        Correlation-ID generated by the UAS, the FEID of the UAS, and the
        RKS-Group-ID of the Record-Keeping-Server being used by the UAS.  The
     
     
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        UAS MAY change the values of Acct-Charge-URI if it wishes to override
        the billing information that was present in the INVITE (e.g., for a
        toll-free call).  The decision to do this and the contents of the new
        Acct-Charge-URI MUST be determined by service provider policy
        provisioned in the UAS.  If the UAS performed a LNP query, it MUST
        include the Routing Number and Location Routing Number returned by
        the query.
     
        The UAS MUST add a P-DCS-Billing-Info header to a 3xx-redirect
        response to an initial INVITE, giving the accounting information for
        the call forwarder, for the call segment from the destination to the
        forwarded-to destination.
     
     7.6. Procedures at Proxy
     
        Three sets of proxy procedures are defined: (1) the procedures at an
        originating proxy, (2) the procedures at a terminating proxy, and (3)
        the procedures at a tandem proxy.
     
        The originating proxy is a proxy that received the INVITE request
        from a non-trusted endpoint.
     
        The terminating proxy is a proxy that sends the INVITE request to a
        non-trusted endpoint.
     
        A proxy that is neither an originating proxy, nor a terminating
        proxy, is a tandem proxy.
     
        For purposes of mid-call changes, such as call transfers, the proxy
        that receives the request from a non-trusted endpoint is considered
        the initiating proxy; the proxy that sends the request to a non-
        trusted endpoint is considered the recipient proxy.  Procedures for
        the initiating proxy are included below with those for originating
        proxies, while procedures for the recipient proxy are included with
        those for terminating proxies.
     
        A proxy that both receives the INVITE request from an untrusted
        endpoint, and sends the INVITE request to a non-trusted endpoint,
        performs both sets of procedures.
     
     7.6.1. Procedures at Originating Proxy
     
        The originating proxy MUST generate the Billing-Correlation-ID for
        the call, and insert it into the P-DCS-Billing-Info header in the
        initial INVITE message sent to the terminating proxy, along with the
        charging information for the call.  The originating proxy MUST
        include its FEID, and the RKS-Group-ID for the Record-Keeping-Server
     
     
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        being used by the originating proxy.  If the originating proxy
        performed a LNP query, it MUST include the Routing Number and
        Location Routing Number returned by the query.  Any P-DCS-Billing-
        Info header present from an untrusted UA MUST be removed.
     
        If the Request-URI contains a private-URL, and the decoded username
        contains billing information, the originating proxy MUST generate a
        P-DCS-Billing-Info header with that decrypted information. Otherwise,
        the originating proxy MUST determine the accounting information for
        the call originator, and insert a P-DCS-Billing-Info header including
        that information.
     
        If the response to the initial INVITE is a 3xx-Redirect, received
        prior to a 18x, the originating proxy generates a new initial INVITE
        request to the destination specified in the Contact: header, as per
        standard SIP.  If an originating proxy receives a 3xx-Redirect
        response to an initial INVITE prior to a 18x response, the INVITE
        generated by the proxy MUST contain the P-DCS-Billing-Info header
        from the 3xx-Redirect response.
     
        If the response to the initial INVITE is a 3xx-Redirect, received
        after a 18x, the originating proxy generates a private-URL and places
        it in the Contact header of a 3xx-Redirect response sent to the
        originating endpoint.  This private-URL MUST contain (or contain a
        pointer to) the P-DCS-Billing-Info value, which indicate the charging
        arrangement for the new call, and an expiration time very shortly in
        the future, to limit the ability of the originator to re-use this
        private-URL for multiple calls.
     
        An originating proxy that processes a REFER request from an untrusted
        UA MUST include a P-DCS-Billing-Info header in the Refer-to's URL.
        This P-DCS-Billing-Info header MUST include the accounting
        information of the initiator.
     
     7.6.2. Procedures at Terminating Proxy
     
        The terminating proxy MUST NOT send the P-DCS-Billing-Info header to
        an untrusted destination.
     
        The terminating proxy MUST include a P-DCS-Billing-Info header in the
        first reliable 1xx (except 100) or 2xx response to an initial INVITE
        message.  This P-DCS-Billing-Info header MUST include the Billing-
        Correlation-ID generated by the terminating proxy, the FEID of the
        terminating proxy, and the RKS-Group-ID of the Record-Keeping-Server
        being used by the terminating proxy.  The terminating proxy MAY
        change the values of Acct-Charge-URI if it wishes to override the
        billing information that was present in the INVITE (e.g., for a toll-
     
     
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        free call).  The decision to do this and the contents of the
        resulting P-DCS-Billing-Info header MUST be determined by service
        provider policy provisioned in the terminating proxy.  If the
        terminating proxy performed a LNP query, it MUST include the Routing
        Number and Location Routing Number returned by the query.
     
        The terminating proxy MUST add P-DCS-Billing-Info headers to a 3xx-
        redirect response to an initial INVITE, giving the accounting
        information for the call forwarder, for the call segment from the
        destination to the forwarded-to destination.
     
        A proxy receiving a mid-call REFER request that includes a Refer-to
        header generates a private-URL and places it in the Refer-to header
        sent to the endpoint.  This private-URL MUST contain the P-DCS-
        Billing-Info value, which indicate the charging arrangement for the
        new call, and an expiration time very shortly in the future, to limit
        the ability of the endpoint to re-use this private-URL for multiple
        calls.
     
     
     7.6.3. Procedures at Tandem Proxy
     
        If the tandem proxy performed a LNP query, it MUST insert the Routing
        Number and Location Routing Number returned by the query into the P-
        DCS-Billing-Info header in the first reliable 1xx/2xx/3xx (except
        100) response.
     
     8. P-DCS-LAES and P-DCS-REDIRECT
     
        NOTE:  According to RFC 2804 [RFC2804], the IETF supports
        documentation of lawful intercept technology if it is necessary to
        develop it.  The following section provides such documentation.  The
        RFC 2119 language, as stated above, describes the requirements of the
        specification only if implemented, and strictly within the
        applicability domain described above.  See RFC 2804 for description
        of issues regarding privacy, security, and complexity in relation to
        this technology.
     
        The P-DCS-LAES extension contains the information needed to support
        Lawfully Authorized Electronic Surveillance.  This header contains
        the address and port of an Electronic Surveillance Delivery Function
        for delivery of a duplicate stream of event messages related to this
        call.  The header may also contain an additional address and port for
        delivery of call content.  Security key information is included to
        enable pairs of Delivery Functions to securely exchange surveillance
        information.  This header is only used between proxies and trusted
        User Agents.
     
     
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        The P-DCS-Redirect extension contains call identifying information
        needed to support the requirements of Lawfully Authorized Electronic
        Surveillance of redirected calls.  This header is only used between
        proxies and trusted User Agents.
     
        Use of P-DCS-LAES and P-DCS-Redirect is controlled by a combination
        of legislation, regulation, and court orders, which MUST be followed.
        In certain cases inclusion of these headers will be mandated, and
        therefore MUST be present in the requests and responses indicated. In
        other cases inclusion of these headers will be forbidden, and
        therefore MUST NOT be present in the request and responses indicated.
        In the sub-sections that follow, use of "SHOULD" is intended to
        capture these conflicting situations, e.g., a P-DCS-LAES header
        SHOULD be included in an initial INVITE means either that it MUST be
        included or that it MUST NOT be included, based on the applicable
        court orders.
     
     8.1. Syntax
     
        The formats of the P-DCS-LAES and P-DCS-Redirect headers are given by
        the following ABNF (some terms used in this ABNF are defined in
        [RFC3261] and [RFC2234]):
     
           P-DCS-LAES        = "P-DCS-LAES" HCOLON Laes-sig
                                *(SEMI Laes-param)
           Laes-sig          = hostport
           Laes-param        = Laes-content / Laes-bcid
                               Laes-cccid / generic-param
           Laes-content      = "content" EQUAL hostport
     
           Laes-bcid         = "bcid" EQUAL 1*48 (HEXDIG)
           Laes-cccid        = "cccid" EQUAL 1*48 (HEXDIG)
     
           P-DCS-Redirect    = "P-DCS-Redirect" HCOLON Called-ID
                               *(SEMI redir-params)
           Called-ID         = LDQUOT addr-spec RDQUOT
           redir-params      = redir-uri-param / redir-count-param /
                               generic-param
           redir-uri-param   = "redirector-uri" EQUAL Redirector
           Redirector        = LDQUOT addr-spec RDQUOT
           redir-count-param = "count" EQUAL Redir-count
           Redir-count       = 1*DIGIT
     
        This document adds the following entry to Table 2 of [RFC3261]:
     
           Header field         where proxy  ACK  BYE  CAN  INV  OPT  REG
           ------------         ----- -----  ---  ---  ---  ---  ---  ---
     
     
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           P-DCS-LAES                  adr    -    -    -    o    -    -
           P-DCS-Redirect              adr    -    -    -    o    -    -
     
                                             SUB  NOT  REF  INF  UPD  PRA
                                             ---  ---  ---  ---  ---  ---
                                              -    -    -    -    -    -
                                              -    -    -    -    -    -
     
        The values of Laes-sig and Laes-content are addresses of the
        Electronic Surveillance Delivery Function, and used as the
        destination address for call-identifying information and call-
        content, respectively.  [PCSEC]. Laes-bcid contains a correlation ID
        that is used to link a sequence of intercepted call processing events
        related to a single call. Laes-cccid contains an identifier of the
        intercepted call content. The Laes-bcid field MUST always be present.
        The Laes-cccid field MUST be present when the Laes-content field is
        present.
     
        The P-DCS-Redirect header contains redirection information.  The
        redir-uri-param indicates the original destination requested by the
        user (e.g., dialed number), the Redirector indicates the new
        destination, and the Redir-count indicates the number of redirections
        that have occurred.
     
     8.2. Procedures at an Untrusted User Agent Client (UAC)
     
        This header MUST NOT be sent to an untrusted UAC, and MUST NOT be
        sent by an untrusted UAC.
     
     8.3. Procedures at a Trusted User Agent Client (UAC)
     
        The UAC checks for an outstanding lawfully authorized surveillance
        order for the originating subscriber, and, if present, includes this
        information in the Authorization for Quality of Service [PCDQOS] or
        signals this information to the device performing the intercept
        (e.g., a Media Gateway).
     
        If the P-DCS-LAES header is present in the first reliable 1xx (except
        100), 2xx or 3xx response (indicating surveillance is required on the
        terminating subscriber, but that the terminating equipment is unable
        to perform that function), the UAC MUST include this information in
        the Authorization for Quality of Service, or MUST signal this
        information to the device performing the intercept (e.g., a Media
        Gateway).
     
        If a 3xx-Redirect response is received to the initial INVITE request,
        and if a P-DCS-LAES header is present in the 3xx response, the UAC
     
     
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        SHOULD include that header unchanged in the reissued INVITE. The UAC
        SHOULD also include a P-DCS-Redirect header containing the original
        dialed number, the new destination number, and the number of
        redirections that have occurred.  Although it is technically possible
        for the originating equipment to perform this surveillance (or add to
        its existing surveillance of the call), the design of the
        surveillance system has the terminating equipment performing the
        surveillance for all the intermediate forwardings.
     
        A UAC that includes a Refer-to header in a REFER request, when the
        originating subscriber has an outstanding lawfully authorized
        surveillance order, SHOULD include a P-DCS-LAES header attached to
        the Refer-to.  The P-DCS-LAES header SHOULD include the address and
        port of the local Electronic Surveillance Delivery Function for a
        copy of the call's event messages, SHOULD include the address and
        port of the local Electronic Surveillance Delivery Function for the
        copy of call content if call content is to be intercepted, and SHOULD
        include a random string for use as a security key between the
        Delivery Functions.
     
        The trusted UAC MUST NOT send the P-DCS-LAES and P-DCS-Redirect
        headers to an untrusted entity.
     
     
     8.4. Procedures at an Untrusted User Agent Server (UAS)
     
        This header MUST NOT be sent to an untrusted UAS, and MUST NOT be
        sent by an untrusted UAS.
     
     8.5. Procedures at a Trusted User Agent Server (UAS)
     
        The UAS checks for an outstanding lawfully authorized surveillance
        order for the terminating subscriber, or presence of the P-DCS-LAES
        header in the INVITE request.  If either is present, the UAS includes
        this information in the authorization for Quality of Service
        [PCDQOS].
     
        If the terminating equipment is unable to perform the required
        surveillance (e.g., if the destination is a voicemail server), the
        UAS SHOULD include a P-DCS-LAES header in the first reliable non-100
        response requesting the originating proxy to perform the
        surveillance.  The P-DCS-LAES header SHOULD include the address and
        port of the local Electronic Surveillance Delivery Function for a
        copy of the call's event messages, SHOULD include the address and
        port of the local Electronic Surveillance Delivery Function for the
        copy of call content if call content is to be intercepted, and SHOULD
     
     
     
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        include a random string for use as a security key between the
        Delivery Functions.
     
        If the response to the initial INVITE request is a 3xx-Redirect
        response, and there is an outstanding lawfully authorized
        surveillance order for the terminating subscriber, the UAS SHOULD
        include a P-DCS-LAES header in the 3xx-Redirect response, with
        contents as described above.
     
        The trusted UAS MUST NOT send the P-DCS-LAES and P-DCS-Redirect
        headers to an untrusted entity.
     
     8.6. Procedures at Proxy
     
        Two sets of proxy procedures are defined: (1) the procedures at an
        originating proxy, and (2) the procedures at a terminating proxy. The
        originating proxy is a proxy that received the INVITE request from a
        non-trusted endpoint.
     
        The terminating proxy is a proxy that sends the INVITE request to a
        non-trusted endpoint.
     
        For purposes of mid-call changes, such as call transfers, the proxy
        that receives the request from a non-trusted endpoint is considered
        the initiating proxy; the proxy that sends the request to a non-
        trusted endpoint is considered the recipient proxy.  Procedures for
        the initiating proxy are included below with those for originating
        proxies, while procedures for the recipient proxy are included with
        those for terminating proxies.
     
        A proxy that both receives the INVITE request from an untrusted
        endpoint, and sends the INVITE request to a non-trusted endpoint,
        MUST NOT generate P-DCS-LAES nor P-DCS-Redirect headers.
     
        A proxy that is neither an originating proxy nor a terminating proxy
        SHOULD pass the P-DCS-Laes and P-DCS-Redirect headers in requests and
        responses.
     
     8.6.1. Procedures at Originating Proxy
     
        The Originating Proxy MUST remove any P-DCS-LAES and P-DCS-Redirect
        headers in requests or responses to or from an untrusted proxy or
        untrusted UA.
     
        The originating proxy checks for an outstanding lawfully authorized
        surveillance order for the originating subscriber, and, if present,
        includes this information in the Authorization for Quality of Service
     
     
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        [PCDQOS] or signals this information to the device performing the
        intercept (e.g., a Media Gateway).
     
        If the P-DCS-LAES header is present in the first reliable 1xx (except
        100), 2xx or 3xx response (indicating surveillance is required on the
        terminating subscriber, but that the terminating equipment is unable
        to perform that function), the originating proxy MUST include this
        information in the Authorization for Quality of Service, or MUST
        signal this information to the device performing the intercept (e.g.,
        a Media Gateway).
     
        If the Request-URI in an initial INVITE request contains a private-
        URL, the originating proxy MUST decrypt the userinfo information to
        find the real destination for the call, and other special processing
        information.  If electronic surveillance information is contained in
        the decrypted userinfo, the originating proxy SHOULD generate a P-
        DCS-LAES header with the surveillance information.
     
        If a 3xx-Redirect response is received to the initial INVITE request
        prior to a 18x, and if a P-DCS-LAES header is present in the 3xx
        response, the originating proxy SHOULD include that header unchanged
        in the reissued INVITE.  The originating proxy SHOULD also include a
        P-DCS-Redirect header containing the original dialed number, the new
        destination number, and the number of redirections that have
        occurred.
     
        If a 3xx-Redirect response is received to the initial INVITE request
        after a 18x, the originating proxy generates a private-URL and places
        it in the Contact header of a 3xx-Redirect response sent to the
        originating endpoint.  If a P-DCS-LAES header is present in the 3xx
        response, this private-URL MUST contain (1) the electronic
        surveillance information from the 3xx-Redirect response, (2) the
        original destination number, (3) the identity of the redirecting
        party, and (4) the number of redirections of this call.
     
        An originating proxy that processes a REFER request [RFC3515] from an
        untrusted UA, when the originating subscriber has an outstanding
        lawfully authorized surveillance order, becomes a B2BUA for that
        request.  It SHOULD reissue the request with a P-DCS-LAES header
        added to the Refer-to's URL.  The P-DCS-LAES header SHOULD include
        (1) the address and port of the local Electronic Surveillance
        Delivery Function for a copy of the call's event messages, (2) the
        address and port of the local Electronic Surveillance Delivery
        Function for the copy of call content if call content is to be
        intercepted, and (3) a random string for use as a security key
        between the Delivery Functions.
     
     
     
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        An initiating proxy that sends a mid-call REFER request including a
        Refer-to header, when the initiating subscriber has an outstanding
        lawfully authorized surveillance order, SHOULD include a P-DCS-LAES
        header in the Refer-to's URL.
     
        The originating proxy MUST NOT send the P-DCS-LAES and P-DCS-Redirect
        headers to an untrusted entity.
     
     8.6.2. Procedures at Terminating Proxy
     
        The Terminating Proxy MUST remove any P-DCS-LAES and P-DCS-Redirect
        headers in requests or responses to or from an untrusted proxy or UA.
     
        The terminating proxy checks for an outstanding lawfully authorized
        surveillance order for the terminating subscriber.  If present, the
        terminating proxy includes this information in the authorization for
        Quality of Service [PCDQOS].
     
        The terminating proxy MUST NOT send the P-DCS-LAES and P-DCS-Redirect
        headers to an untrusted entity, either as headers in the request or
        response, or as headers attached to URIs in the request or response.
     
        If the terminating equipment is unable to perform the required
        surveillance (e.g., if the destination is a voicemail server), the
        terminating proxy SHOULD include a P-DCS-LAES header in the first
        reliable 1xx/2xx/3xx (except 100) response requesting the originating
        proxy to perform the surveillance.  The P-DCS-LAES header SHOULD
        include the address and port of the local Electronic Surveillance
        Delivery Function for a copy of the call's event messages, SHOULD
        include the address and port of the local Electronic Surveillance
        Delivery Function for the copy of call content if call content is to
        be intercepted, and SHOULD include a random string for use as a
        security key between the Delivery Functions.
     
        If the response to the initial INVITE request is a 3xx-Redirect
        response, and there is an outstanding lawfully authorized
        surveillance order for the terminating subscriber, the terminating
        proxy SHOULD include a P-DCS-LAES header in the 3xx-Redirect
        response, with contents as described above.
     
        A proxy receiving a mid-call REFER request [RFC3515] that includes a
        Refer-to header with a P-DCS-LAES header attached becomes a B2BUA for
        this request.  It MUST generate a private-URL and place it in the
        Refer-to header sent to the endpoint.  This private-URL MUST contain
        the P-DCS-LAES information from the attached header.
     
     
     
     
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     9. Security Considerations
     
        QoS gate coordination, billing information, and electronic
        surveillance information are all considered to be sensitive
        information that MUST be protected from eavesdropping and furthermore
        require integrity checking.  It is therefore necessary that the
        trusted UAs and proxies take precautions to protect this information
        from eavesdropping and tampering.  Use of IPsec or TLS between
        Proxies is REQUIRED.  A minimum mandatory-to-implement IPsec
        configuration for the DCS architecture is given by [PCSEC].  Also
        REQUIRED is mutual authentication (1) between Proxies and (2) between
        trusted UAs and Proxies, both of which MAY be implemented with
        administratively pre-shared keys, or through consultation with
        another trusted third party.  If IPsec is to be used, the
        specification of the security policies and procedures of the
        administrative domain where these headers are applicable (and all
        connections between administrative domains in the federation) MUST
        define an interoperable set of options.
     
     10. IANA Considerations
     
        This document defines a number of SIP extension headers, which have
        been included in the registry of SIP headers defined in [RFC3261].
        Registration information for new headers is as follows:
     
        Header Field Name:   P-DCS-Trace-Party-ID
           RFC Number:       3603
           Compact Form:     none
     
        Header Field Name:   P-DCS-OSPS
           RFC Number:       3603
           Compact Form:     none
     
        Header Field Name:   P-DCS-Billing-Info
           RFC Number:       3603
           Compact Form:     none
     
        Header Field Name:   P-DCS-LAES
           RFC Number:       3603
           Compact Form:     none
     
        Header Field Name:   P-DCS-Redirect
           RFC Number:       3603
           Compact Form:     none
     
     
     
     
     
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     11. Change Log
     
     11.1. Changes in -00 since RFC 3603
     
        o  The P-DCS-Trace-Party-ID header has been extended to include the
           trace-param parameter.
     
        o  The P-DCS-Billing-Info header has been extended to include the
           Jip-param parameter in the Billing-Info-Param.
     
        o  The P-DCS-LAES header has been extended to include the Laes-bcid
           and Laes-cccid parameters. The Laes-key parameter has been
           deprecated.
     
        o  Added missing "SEMI" in P-DCS-REDIRECT header.
     
     
     
     12. To Do
     
        o  Update method tables to include missing methods (PUBLISH and
           MESSAGE).
     
        o  Update procedures for P-DCS-Billing-Info to cover the new Jip-
           param parameter.
     
        o  Update procedures for P-DCS-LAES and P-DCS-REDIRECT to cover the
           new Laes-bcid and Laes-cccid parameters and the removal of the
           Laes-Key parameter. Also verify consistency with updated
           PacketCable procedures.
     
        o  Add various nit updates.
     
     
     
     13. References
     
     13.1. 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.
     
     
     
     
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        [RFC2234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
                  Specifications: ABNF", RFC 2234, November 1997.
     
        [RFC3515] Sparks, R., "The Session Initiation Protocol (SIP) Refer
                  Method", RFC 3515, April 2003.
     
        [RFC2804] IAB and IESG, "IETF Policy on Wiretapping", RFC 2804, May
                  2000.
     
        [TDIALOG] J. Rosenberg, "Request Authorization through Dialog
                  Identification in the Session Initiation Protocol (SIP)",
                  Work in Progress, December 2005.
     
     13.2. Informative References
     
        [DCSARCH] DCS Group, "Architectural Considerations for Providing
                  Carrier Class Telephony Services Utilizing SIP-based
                  Distributed Call Control Mechanisms", Work in Progress.
     
        [PCDQOS]  PacketCable Dynamic Quality of Service Specification, pkt-
                  sp-dqos-i07-030815, August 2003.
     
        [PCSEC]   PacketCable Security Specification, pkt-sp-sec-i09-030728,
                  July 2003.
     
        [PCEM]    PacketCable Event Message Specification, pkt-sp-em-i07-
                  030815, August 2003.
     
        [RFC3325] Jennings, C., Peterson, J. and M. Watson, "Private
                  Extensions to the Session Initiation Protocol (SIP) for
                  Asserted Identity within Trusted Networks", RFC 3325,
                  November 2002.
     
     14. Acknowledgements
     
        The Distributed Call Signaling work in the PacketCable project is the
        work of a large number of people, representing many different
        companies.  The authors would like to recognize and thank the
        following for their assistance: John Wheeler, Motorola; David
        Boardman, Daniel Paul, Arris Interactive; Bill Blum, Jon Fellows, Jay
        Strater, Jeff Ollis, Clive Holborow, Motorola; Doug Newlin, Guido
        Schuster, Ikhlaq Sidhu, 3Com; Jiri Matousek, Bay Networks; Farzi
        Khazai, Nortel; John Chapman, Bill Guckel, Michael Ramalho, Cisco;
        Chuck Kalmanek, Doug Nortz, John Lawser, James Cheng, Tung- Hai
        Hsiao, Partho Mishra, AT&T; Telcordia Technologies; and Lucent Cable
        Communications.
     
     
     
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        Previous versions further acknowledged, as co-authors, several people
        for providing the text of this document.  They are:
     
          Bill Marshall (wtm@research.att.com) and K. K. Ramakrishnan
          (kkrama@research.att.com), AT&T; Ed Miller
          (edward.miller@terayon.com), Terayon; Glenn Russell
          (G.Russell@Cablelabs.com), CableLabs; Burcak Beser
          (burcak@juniper.net) Juniper Networks, Mike Mannette
          (Michael_Mannette@3com.com) and Kurt Steinbrenner
          (Kurt_Steinbrenner@3com.com), 3Com; Dave Oran (oran@cisco.com) and
          Flemming Andreasen (fandreas@cisco.com), Cisco Systems; John
          Pickens (jpickens@com21.com), Com21; Poornima Lalwaney
          (poornima.lalwaney@nokia.com), Nokia; Jon Fellows
          (jfellows@coppermountain.com), Copper Mountain Networks; Doc Evans
          (n7dr@arrisi.com) Arris, and Keith Kelly (keith@netspeak.com),
          NetSpeak.
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
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     Author's Addresses
     
        Bill Marshall
        AT&T
        Florham Park, NJ  07932
        EMail: wtm@research.att.com
     
     
        Flemming Andreasen
        Cisco
        Edison, NJ
        EMail: fandreas@cisco.com
     
        Bernie McKibben
        CableLabs
        Louisville, CO
        B.McKibben@cablelabs.com
     
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     Disclaimer of Validity
     
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        Copyright (C) The Internet Society (2006).
     
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