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INFORMATIONAL

Network Working Group                                       F. Andreasen
Request for Comments: 5503                                         Cisco
Obsoletes: 3603                                              B. McKibben
Category: Informational                                        CableLabs
                                                             B. Marshall
                                                                    AT&T
                                                              March 2009


Private Session Initiation Protocol (SIP) Proxy-to-Proxy Extensions for
   Supporting the PacketCable Distributed Call Signaling Architecture

Status of This Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

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   Copyright (c) 2009 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   Please review these documents carefully, as they describe your rights
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   Without obtaining an adequate license from the person(s) controlling
   the copyright in such materials, this document may not be modified
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   it for publication as an RFC or to translate it into languages other
   than English.











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Abstract

   In order to deploy a residential telephone service at a 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, RFC 3261, for
   supporting the exchange of customer information and billing
   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.

































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Table of Contents

   1. Applicability Statement .........................................4
   2. Introduction ....................................................4
   3. Trust Boundary ..................................................6
   4. Conventions Used in This Document ...............................7
   5. P-DCS-TRACE-PARTY-ID ............................................7
      5.1. Syntax .....................................................8
      5.2. Procedures at an Untrusted User Agent Client (UAC) .........9
      5.3. Procedures at a Trusted User Agent Client (UAC) ............9
      5.4. Procedures at an Untrusted User Agent Server (UAS) .........9
      5.5. Procedures at a Trusted User Agent Server (UAS) ............9
      5.6. Procedures at Proxy .......................................10
           5.6.1. Procedures at Originating Proxy ....................10
           5.6.2. Procedures at Terminating Proxy ....................11
   6. P-DCS-OSPS .....................................................11
      6.1. Syntax ....................................................11
      6.2. Procedures at an Untrusted User Agent Client (UAC) ........12
      6.3. Procedures at a Trusted User Agent Client (UAC) ...........12
      6.4. Procedures at an Untrusted User Agent Server (UAS) ........13
      6.5. Procedures at a Trusted User Agent Server (UAS) ...........13
      6.6. Procedures at Proxy .......................................14
   7. P-DCS-BILLING-INFO .............................................14
      7.1. Syntax ....................................................16
      7.2. Procedures at an Untrusted User Agent Client (UAC) ........18
      7.3. Procedures at a Trusted User Agent Client (UAC) ...........18
      7.4. Procedures at an Untrusted User Agent Server (UAS) ........18
      7.5. Procedures at a Trusted User Agent Server (UAS) ...........18
      7.6. Procedures at Proxy .......................................19
           7.6.1. Procedures at Originating Proxy ....................19
           7.6.2. Procedures at Terminating Proxy ....................20
           7.6.3. Procedures at Tandem Proxy .........................21
   8. P-DCS-LAES and P-DCS-Redirect ..................................21
      8.1. Syntax ....................................................23
      8.2. Procedures at an Untrusted User Agent Client (UAC) ........24
      8.3. Procedures at a Trusted User Agent Client (UAC) ...........24
      8.4. Procedures at an Untrusted User Agent Server (UAS) ........25
      8.5. Procedures at a Trusted User Agent Server (UAS) ...........25
      8.6. Procedures at Proxy .......................................26
           8.6.1. Procedures at Originating Proxy ....................26
           8.6.2. Procedures at Terminating Proxy ....................28
   9. Security Considerations ........................................29
   10. IANA Considerations ...........................................29
   11. Changes since RFC 3603 ........................................31
   12. Acknowledgments ...............................................32
   13. References ....................................................32
      13.1. Normative References .....................................32
      13.2. Informative References ...................................33



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1.  Applicability Statement

   The Session Initiation Protocol (SIP) [RFC3261] 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 [RFC2119] 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 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 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 Distributed Call Signaling (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.






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   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.  The extensions only appear on trusted network segments, are
   inserted upon entering a trusted network region, and are removed
   before leaving trusted network segments.

   Significant amounts of information are 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
   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 it
   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.




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   The addition of a SIP General Header Field allows for the capture of
   billing information and billing identification for the duration of
   the call.

   The billing extensions 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 for support of 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
   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.








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   The following sections giving procedures for user agents therefore
   are subdivided into trusted user agents and untrusted user agents.
   Since UAs may support client and server functions, the UA sections
   include procedures for the User Agent Client (UAC) and User Agent
   Server (UAS).

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, [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.

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 User Agent
   Client (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 untrusted UAC also includes the



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   Target-Dialog header field, defined in [RFC4538], in the INVITE
   request in order to explicitly identify the call to be traced.  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
                           *1(SEMI timestamp-param) *(SEMI trace-param)
   timestamp-param      = "timestamp=" 1*DIGIT ["." 1*DIGIT]
   trace-param          = generic-param ; defined in RFC 3261

   This document adds the following entry to Table 2 of [RFC3261]:

   Header field         where proxy  ACK  BYE  CAN  INV  OPT  REG  PUB
   ------------         ----- -----  ---  ---  ---  ---  ---  ---  ---
   P-DCS-Trace-Party-ID   R    dmr    -    -    -    o    -    -    -
                                     SUB  NOT  REF  INF  UPD  PRA  MSG
                                     ---  ---  ---  ---  ---  ---  ---
                                      -    -    -    -    -    -    -

   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 timestamp-param contains the value of the time the UA determines
   it received the session initiation request of the call requested to
   be traced.  The timestamp-param is populated using the Network Time
   Protocol timestamp format defined in RFC 1305 [RFC1305] and used by
   the Simple Network Time Protocol [RFC4330].  The timestamp SHOULD be
   encoded in UTF-8 Format per [RFC3629].  The trace-param is a generic
   parameter for future extensions.

   An example of the P-DCS-Trace-Party-ID header is shown as follows:

   P-DCS-Trace-Party-ID: <sip:+12345678912@domain.com;user=phone>;
   timestamp=3434688831.2327





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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 trace
   request from the Untrusted User Agent Client is able to be initiated
   during the dialog or after the release of the dialog or call that is
   requested to be traced.  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 [RFC3603] version of
   the P-DCS-Trace-Party-ID did not include the timestamp-param
   parameter; however, the syntax is backwards compatible with
   [RFC3603].  A UAC compliant to this updated specification MUST insert
   the timestamp and the Target-Dialog header field defined in [RFC4538]
   if known to the UAC.

   In case of an anonymous malicious call, where the remote party is not
   known to the Untrusted UAC, the Untrusted UAC SHOULD indicate the
   user as anonymous in the P-DCS-Trace-Party-ID, for example, as
   follows: sip:anonymous@anonymous.invalid.

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 User Agent Server (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.

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 and associated trace parameters (if any) from the
   Target-Dialog header field 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.

   If the P-DCS-Trace-Party-ID header is not present in the initial
   INVITE request from a UAC, and the Request-URI of the INVITE has
   userinfo set to "call-trace" the UAS MUST reject the request.




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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 an untrusted endpoint.

   The terminating proxy is a proxy that sends the INVITE request to an
   untrusted 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 it 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 and trace parameters from the Target-Dialog
   header fields defined in [RFC4538]).

   The proxy records the caller URL and target dialog IDs on sessions
   directed toward the untrusted UAC if provisioned to do so by the
   network operator.  If the is P-DCS-Trace-Party-ID header is present
   in a valid request, and contains an anonymous caller indication in
   the name-addr parameter, the originating proxy MUST replace the
   anonymous URL with the verified identity of the caller of the session
   that is being traced if available and recorded by the proxy.
   Otherwise, the proxy does not replace the anonymous URL.

   If the origination proxy is provisioned to store URLs and target
   dialog IDs for incoming calls, and if the proxy detects that the URL
   and target dialog ID in a trace request does not match a recorded
   incoming dialog request, then the proxy MUST reject the trace call
   request.

   The origination proxy does not add the P-DCS-Trace-Party-ID header
   from a request that does not already contain the header.






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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.

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 Public Switched
   Telephone Network (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, with a field that
   may be set to a value indicating when a special type of call
   processing is requested.  We define three values in this header
   field, 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











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   This document adds the following entry to Table 2 of [RFC3261]:

     Header field         where proxy  ACK  BYE  CAN  INV  OPT  REG  PUB
     ------------         ----- -----  ---  ---  ---  ---  ---  ---  ---
     P-DCS-OSPS             R     dr    -    -    -    o    -    -    -
                                       SUB  NOT  REF  INF  UPD  PRA  MSG
                                       ---  ---  ---  ---  ---  ---  ---
                                        -    -    -    -    o    -    -

   The OSPS-Tag value of "token" is defined for extensibility, and is
   reserved for future use.

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 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 preexisting dialog established
   with the OSPS-Tag value of "BLV", or (2) an UPDATE request within a
   preexisting 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 preexisting dialog
   established by a UAC to an operator or PSAP, or (2) an UPDATE request
   within a preexisting dialog established by a UAC to an operator or
   PSAP.








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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, it MUST reject
   the request with a 403 (Forbidden) response.

   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 that was established with the OSPS-Tag value of
   "BLV", it MUST reject the request with a 403 (Forbidden) response.

   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.

   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
   quality-of-service (QoS) pre-conditions, etc.), the UAS MUST send an
   audio stream on this connection to the address and port given in the
   Session Description Protocol (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 there is 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.




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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
   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





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   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.

   The billing extensions only appear on trusted network segments, and
   MAY be inserted by a proxy or trusted UA in INVITE and SUBSCRIBE
   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 UAs.
   It is never sent to an untrusted UA.  It is expected that untrusted
   UAs do not send this header.



































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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  PUB
   ------------         ----- -----  ---  ---  ---  ---  ---  ---  ---
   P-DCS-Billing-Info         admr    -    -    -    o    -    -    -

                                     SUB  NOT  REF  INF  UPD  PRA  MSG
                                     ---  ---  ---  ---  ---  ---  ---
                                      -    -    -    -    -    -    -







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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 UAs.

   The Billing-Correlation-ID, BCID, 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-Loc-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 which the call originated.
   The field is further defined in [PCEM] under the element identifier
   "Jurisdiction_Information_Parameter" (element ID 82).  An older
   [RFC3603] compliant implementation may not use the JIP-param.




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7.2.  Procedures at an Untrusted User Agent Client (UAC)

   This header is never sent to an untrusted UA.  It is expected that
   untrusted UAs do not send this header.

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 or
   SUBSCRIBE message sent to the terminating entity, 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 available to the UAC, the UAC MUST include the JIP-
   param.

   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 field, 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 field
   values from the 3xx-Redirect response.  If the UAC is acting as a
   back-to-back user agent (B2BUA), instead of generating a new INVITE
   it MAY generate a private-URL and place it in the Contact header
   field 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 or
   SUBSCRIBE message.  This P-DCS-Billing-Info header MUST include the
   Billing-Correlation-ID generated by the UAS, the FEID of the UAS, and



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   the RKS-Group-ID of the Record-Keeping server being used by the UAS.
   The 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 an 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 or
   SUBSCRIBE request from an untrusted endpoint.

   The terminating proxy is a proxy that sends the INVITE or SUBSCRIBE
   request to an untrusted 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 an untrusted 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 request from an untrusted endpoint,
   and sends the request to an untrusted 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 or SUBSCRIBE message sent to the terminating entity,
   along with the charging information for the call.  The originating
   proxy MUST include its FEID and the RKS-Group-ID for the



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   Record-Keeping server being used by the originating proxy.  If the
   originating proxy performed an LNP query, it MUST include the Routing
   Number, Location Routing Number, and JIP-param 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 non-100 provisional response, the originating proxy
   generates a new initial INVITE request to the destination specified
   in the Contact header field, as per standard SIP.  If an originating
   proxy receives a 3xx-Redirect response to an initial INVITE prior to
   a non-100 provisional 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 non-100 provisional response, 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
   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.

   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
   or SUBSCRIBE 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



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   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 resulting P-DCS-Billing-Info header MUST be
   determined by service provider policy provisioned in the terminating
   proxy.  If the terminating proxy performed an 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 indicates 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 an 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
   [RFC2119] 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 fields MAY also contain the associated BCID for the
   event stream as well as additional address and port for delivery of
   call content and associated cccid.  The BCID is used to correlate a
   series of events associated with a single call or session.  The cccid
   is used to identify an intercepted call content to an intercepted



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   call.  The P-DCS-LAES header is only used between proxies and trusted
   UAs.  The P-DCS-LAES header defined here is not backwards compatible
   with that defined in [RFC3603], which is deprecated by the document.
   This version of the P-DCS-LAES header adds a cccid parameter to
   support the intercept of content, and deletes security key
   information.  This version does not mandate the use of the BCID.

   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 UAs.

   Note that there is overlap in function between the P-DCS-Redirect
   header and the History-Info header specified in RFC 4244.  The
   original P-DCS-Redirect came to existence in RFC 3603 before the
   History-Info.  Therefore, the P-DCS-Redirect header is continued here
   for backwards compatibility with existing implementations.

   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.






















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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 [RFC5234]):

      P-DCS-LAES        = "P-DCS-LAES" HCOLON Laes-sig
                           *(SEMI Laes-param)
      Laes-sig          = hostport
      Laes-param        = Laes-content / Laes-cccid
                          Laes-bcid / generic-param
      Laes-content      = "content" EQUAL hostport

      Laes-bcid         = "bcid" EQUAL 1*48(HEXDIG)
      Laes-cccid        = "cccid" EQUAL 1*8(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  PUB
     ------------         ----- -----  ---  ---  ---  ---  ---  ---  ---
     P-DCS-LAES                  adr    -    -    -    o    -    -    -
     P-DCS-Redirect              adr    -    -    -    o    -    -    -

                                       SUB  NOT  REF  INF  UPD  PRA  MSG
                                       ---  ---  ---  ---  ---  ---  ---
                                        -    -    -    -    -    -    -
                                        -    -    -    -    -    -    -

   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.  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 MAY be present.  The
   BCID is included per network operator configuration to support events
   reported as defined in [PCEM].  The Laes-cccid field MAY be present
   when the Laes-content field is present.  The Laes-cccid is included



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   per network operator configuration for networks where entities
   receiving the intercepted contents may act a media relay functions to
   other surveillance functions that are the source of the content
   surveillance request.  The design of multiple surveillance entities
   that receive call content is beyond the scope of this document.

   The P-DCS-Redirect header contains redirection information.  The
   Called-ID indicates the original destination requested by the user
   (e.g., number dialed originally), the redir-uri-param indicates the
   entity performing the redirection, and the Redir-count indicates the
   number of redirections that have occurred.  For example, if A calls
   B, who forwards to C, who forwards to D, then, when C forwards to D,
   the Called-ID will be A, redir-uri-param will be C, and count will be
   2.

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, MAY include
   this information in the Authorization for Quality of Service [PCDQOS]
   or MAY signal this information to the device performing the intercept
   (e.g., a Media Gateway).  Otherwise, intercept access points are
   instructed to perform call content and/or call data intercept by
   mechanisms that are outside the scope of this document.

   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 MAY include this
   information in the Authorization for Quality of Service, or MAY
   signal this information to the device performing the intercept (e.g.,
   a Media Gateway).  Otherwise, intercept access points are instructed
   to perform call content and/or call data intercept by mechanisms that
   are outside the scope of this document.

   If a 3xx-Redirect response to the initial INVITE request is received,
   and if a P-DCS-LAES header is present in the 3xx response, the UAC
   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 most recent redirecting party, 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



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   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 UAC MAY also include a P-DCS-Redirect header.  The
   P-DCS-LAES header MAY include the Laes-bcid parameter set to a value
   that uniquely identifies the call, 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 MAY
   include the Laes-cccid parameter set to a value that uniquely
   identifies the intercepted audio stream if call content is to be
   intercepted.

   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 MAY
   include this information in the authorization for Quality of Service
   [PCDQOS].  Otherwise, intercept access points are instructed to
   perform call content and/or call data intercept by mechanisms that
   are outside the scope of this document.

   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 1xx
   (except 100), 2xx, or 3xx response requesting the originating proxy
   to perform the surveillance.  The P-DCS-LAES header MAY include the
   Laes-bcid parameter with a value that uniquely identifies the call,
   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






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   content is to be intercepted, and MAY include the Laes-cccid
   parameter set to a value that uniquely identifies the intercepted
   audio stream if call content is to be intercepted.

   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 receives the INVITE request
   from an untrusted endpoint.

   The terminating proxy is a proxy that sends the INVITE request to an
   untrusted endpoint.

   For purposes of mid-call changes, such as call transfers, the proxy
   that receives the request from an untrusted endpoint is considered
   the initiating proxy; the proxy that sends the request to an
   untrusted 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 an untrusted 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,
   MAY include this information in the Authorization for Quality of



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   Service [PCDQOS] or MAY signal this information to the device
   performing the intercept (e.g., a Media Gateway).  Otherwise,
   intercept access points are instructed to perform call content and/or
   call data intercept by mechanisms that are outside the scope of this
   document.

   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 MAY include
   this information in the Authorization for Quality of Service, or MAY
   signal this information to the device performing the intercept (e.g.,
   a Media Gateway).  Otherwise, intercept access points are instructed
   to perform call content and/or call data intercept by mechanisms that
   are outside the scope of this document.

   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 and (if necessary) a P-DCS-REDIRECT header with the
   surveillance information.

   If a 3xx-Redirect response to the initial INVITE request is received
   prior to a non-100 provisional response, 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 most recent redirecting party, and the number of
   redirections that have occurred.

   If a 3xx-Redirect response to the initial INVITE request is received
   after a non-100 provisional response, 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.  It MAY also include a P-DCS-Redirect
   header.  The P-DCS-LAES header SHOULD include (1) the address and
   port of the local Electronic Surveillance Delivery Function for a



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   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.  The P-DCS-LAES header
   MAY include (1) the Laes-bcid parameter set to a value that uniquely
   identifies the call, and (2) the Laes-cccid parameter set to a value
   that uniquely identifies the intercepted audio stream if call content
   is to be intercepted.

   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 MAY include this information in the authorization
   for Quality of Service [PCDQOS].  Otherwise, intercept access points
   are instructed to perform call content and/or call data intercept by
   mechanisms that are outside the scope of this document.

   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 MAY include
   the Laes-bcid parameter set to a value that uniquely identifies the
   call, 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 MAY include the Laes-cccid
   parameter set to a value that uniquely identifies the audio stream if
   call content is to be intercepted.






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   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 and P-DCS-Redirect information from the attached
   header fields.

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 and trusted UAs 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

   The following changes to the Session Initiation Protocol (SIP)
   Parameters registry have been made by IANA.

   The Header Fields registry has been updated as follows:

     Header Name        compact    Reference
     -----------------  -------    ---------
     P-DCS-Trace-Party-ID          [RFC5503]
     P-DCS-OSPS                    [RFC5503]
     P-DCS-Billing-Info            [RFC5503]
     P-DCS-LAES                    [RFC5503]
     P-DCS-Redirect                [RFC5503]





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   The following entries in the Header Field Parameters and Parameter
   Values registry have been updated:

   Header Field                  Parameter Name               Values
   Reference
   ----------------------------  ---------------------------  ----------

   P-DCS-Billing-Info            called                       No
   [RFC5503]
   P-DCS-Billing-Info            calling                      No
   [RFC5503]
   P-DCS-Billing-Info            charge                       No
   [RFC5503]
   P-DCS-Billing-Info            locroute                     No
   [RFC5503]
   P-DCS-Billing-Info            rksgroup                     No
   [RFC5503]
   P-DCS-Billing-Info            routing                      No
   [RFC3603]
   P-DCS-LAES                    content                      No
   [RFC5503]
   P-DCS-Redirect                count                        No
   [RFC5503]
   P-DCS-Redirect                redirector-uri               No
   [RFC5503]

   The following entry in the Header Field Parameters and Parameter
   Values registry has been marked "OBSOLETED":

   Header Field                  Parameter Name               Values
   Reference
   ----------------------------  ---------------------------  ----------
   P-DCS-LAES                    key (OBSOLETED)              No
   [RFC3603][RFC5503]

















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   The following entries in the Header Field Parameters and Parameter
   Values registry have been created:

   Header Field                  Parameter Name               Values
   Reference
   ----------------------------  ---------------------------  ----------
   P-DCS-Billing-Info            jip                          No
   [RFC5503]
   P-DCS-LAES                    bcid                         No
   [RFC5503]
   P-DCS-LAES                    cccid                        No
   [RFC5503]
   P-DCS-Trace-Party-ID          timestamp                    No
   [RFC5503]

11.  Changes since RFC 3603

   o  A timestamp parameter is added to the P-DCS-Trace-Party-ID header
      when available.  Procedures on the use of the Target-Dialog header
      used together with the P-DCS-Trace-Party-ID are added.

   o  The JIP parameter is added to the P-DCS-Billing-Info header when
      available.

   o  The BCID billing correlation identifier and cccid (call content
      channel identifier) are added to the P-DCS-LAES header.

   o  P-DCS-Billing-Info header is applied to the SUBSCRIBE method.

   o  P-DCS-REDIRECT header is applied to the REFER method.

   o  The use of QoS authorization to establish content intercept is
      made optional in order not to preclude alternative content
      intercept provisioning mechanisms.

   o  PUBLISH and MESSAGE methods are added to the SIP method
      applicability matrices throughout.

   o  Correction is made to Table 2 to add m=modify.

   o  IANA considerations are updated.

   o  Corrections are made to timestamp format, and references are
      updated.







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12.  Acknowledgments

   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, Brian Lindsay.  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; Lucent
   Cable Communications; and Miguel Garcia, Ericsson.

   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; David Hancock (D.Hancock@
   Cablelabs.com) and 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.

13.  References

13.1.  Normative References

   [RFC1305]  Mills, D., "Network Time Protocol (Version 3)
              Specification, Implementation", RFC 1305, March 1992.

   [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.

   [RFC3515]  Sparks, R., "The Session Initiation Protocol (SIP) Refer
              Method", RFC 3515, April 2003.



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   [RFC3629]  Yergeau, F., "UTF-8, a transformation format of ISO
              10646", STD 63, RFC 3629, November 2003.

   [RFC4330]  Mills, D., "Simple Network Time Protocol (SNTP) Version 4
              for IPv4, IPv6 and OSI", RFC 4330, January 2006.

   [RFC4538]  Rosenberg, J., "Request Authorization through Dialog
              Identification in the Session Initiation Protocol (SIP)",
              RFC 4538, June 2006.

   [RFC5234]  Crocker, D. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", STD 68, RFC 5234, January 2008.

13.2.  Informative References

   [DCSARCH]  Marshall, W., Osman, M., Andreasen, F., and D. Evans,
              "Architectural Considerations for Providing Carrier Class
              Telephony Services Utilizing SIP-based Distributed Call
              Control Mechanisms", January 2003.

   [PCDQOS]   Cable Television Laboratories, Inc., "PacketCable 1.5
              Specifications, Dynamic Quality of Service", August 2005.

   [PCEM]     Cable Television Laboratories, Inc., "PacketCable 1.5
              Specifications, Event Messages", December 2005.

   [PCSEC]    Cable Television Laboratories, Inc., "PacketCable 1.5
              Specifications, Security", January 2005.

   [RFC2804]  IAB and IESG, "IETF Policy on Wiretapping", RFC 2804,
              May 2000.

   [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.

   [RFC3603]  Marshall, W. and F. Andreasen, "Private Session Initiation
              Protocol (SIP) Proxy-to-Proxy Extensions for Supporting
              the PacketCable Distributed Call Signaling Architecture",
              RFC 3603, October 2003.










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Authors' Addresses

   Flemming Andreasen
   Cisco
   Edison, NJ
   USA

   EMail: fandreas@cisco.com


   Bernie McKibben
   CableLabs
   Louisville, CO
   USA

   EMail: B.McKibben@cablelabs.com


   Bill Marshall
   AT&T
   Florham Park, NJ
   USA

   EMail: wtm@research.att.com



























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