


SIPCORE Working Group                                        C. Holmberg
Internet-Draft                                                  Ericsson
Intended status: Standards Track                                J. Jiang
Expires: June 6, 2017                                       China Mobile
                                                        December 3, 2016


Session Initiation Protocol (SIP) Via header field parameter to indicate
                             received realm
             draft-holmberg-dispatch-received-realm-12.txt

Abstract

   This specification defines a new Session Initiation Protocol (SIP)
   Via header field parameter, "received-realm", which allows a SIP
   entity acting as an entry point to a transit network to indicate from
   which adjacent upstream network a SIP request is received, using a
   network realm value associated with the adjacent network.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   Internet-Drafts are draft documents valid for a maximum of six months
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   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on June 6, 2017.

Copyright Notice

   Copyright (c) 2016 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   publication of this document.  Please review these documents
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   include Simplified BSD License text as described in Section 4.e of



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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  General . . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.2.  Use-Case: Transit Network Application Services  . . . . .   3
     1.3.  Use-Case: Transit Network Routing . . . . . . . . . . . .   3
   2.  Applicability . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Conventions . . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Definitions . . . . . . . . . . . . . . . . . . . . . . . . .   4
   5.  Via 'received-realm' header field parameter . . . . . . . . .   5
     5.1.  General . . . . . . . . . . . . . . . . . . . . . . . . .   5
     5.2.  Operator Identifier . . . . . . . . . . . . . . . . . . .   5
     5.3.  JWS Header  . . . . . . . . . . . . . . . . . . . . . . .   5
     5.4.  JWS Payload . . . . . . . . . . . . . . . . . . . . . . .   6
     5.5.  JWS Serialization . . . . . . . . . . . . . . . . . . . .   7
     5.6.  Syntax  . . . . . . . . . . . . . . . . . . . . . . . . .   7
       5.6.1.  General . . . . . . . . . . . . . . . . . . . . . . .   7
       5.6.2.  ABNF  . . . . . . . . . . . . . . . . . . . . . . . .   7
     5.7.  Example . . . . . . . . . . . . . . . . . . . . . . . . .   8
   6.  User Agent and Proxy behavior . . . . . . . . . . . . . . . .   8
     6.1.  General . . . . . . . . . . . . . . . . . . . . . . . . .   8
     6.2.  Behavior of a SIP entity acting as a network entry point    8
     6.3.  Behavior of a SIP entity consuming the received-network
           value . . . . . . . . . . . . . . . . . . . . . . . . . .   9
   7.  Example . . . . . . . . . . . . . . . . . . . . . . . . . . .   9
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
     8.1.  'received-realm' Via header field parameter . . . . . . .   9
     8.2.  JSON Web Token Claims Registration  . . . . . . . . . . .  10
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  11
   10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  11
   11. Change Log  . . . . . . . . . . . . . . . . . . . . . . . . .  11
   12. References  . . . . . . . . . . . . . . . . . . . . . . . . .  13
     12.1.  Normative References . . . . . . . . . . . . . . . . . .  13
     12.2.  Informative References . . . . . . . . . . . . . . . . .  14
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  14

1.  Introduction

1.1.  General

   When Session Initiation Protocol (SIP) [RFC3261] sessions are
   established between networks belonging to different operators, or
   between interconnected networks belonging to the same operator (or
   enterprise), the SIP requests associated with the session might
   traverse transit networks.



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   Such transit networks might provide different kinds of services.  In
   order to provide such services, a transit network often needs to know
   to which operator (or enterprise) the adjacent upstream network from
   which the SIP session initiation request is received belongs.

   This specification defines a new Session Initiation Protocol (SIP)
   Via header field parameter, "received-realm", which allows a SIP
   entity acting as an entry point to a transit network to indicate from
   which adjacent upstream network a SIP request is received, using a
   network realm value associated with the adjacent network.

   NOTE: As the adjacent network can be an enterprise network, an Inter
   Operator Identifier (IOI) cannot be used to identity the network, as
   IOIs are not defined for enterprise networks.

   The following sections describe use-cases where the information is
   needed.

1.2.  Use-Case: Transit Network Application Services

   The 3rd Generation Partnership Project (3GPP) TS 23.228
   [TS.3GPP.23.228] specifies how an IP Multimedia Subsystem (IMS)
   network can be used to provide transit functionality.  An operator
   can use its IMS network to provide transit functionality e.g., to
   non-IMS customers, to enterprise networks, and to other network
   operators.

   The transit network operator can provide application services to the
   networks for which it is providing transit functionality.  Transit
   application services are typically not provided on a per user basis,
   as the transit network does not have access to the user profiles of
   the networks for which the application services are provided.
   Instead, the application services are provided per served network.

   When a SIP entity that provides application services (e.g., an
   Application Server) within a transit network receives a SIP request,
   in order to apply the correct services, it needs to know the adjacent
   upstream network from which the SIP request is received.

1.3.  Use-Case: Transit Network Routing

   A transit network operator normally interconnects to many different
   operators, including other transit network operators, and provides
   transit routing of SIP requests received from one operator network
   towards the destination.  The destination can be within an operator
   network to which the transit network operator has a direct
   interconnect, or within an operator network that only can be reached
   via one or more interconnected transit operators.



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   For each customer, i.e., interconnected network operator, for which
   the transit network operator routes SIP requests towards the
   requested destination, a set of transit routing polices are defined.
   These policies are used to determine how a SIP request shall be
   routed towards the requested destination to meet the agreement the
   transit network operator has with its customer.

   When a SIP entity that performs the transit routing functionality
   receives a SIP request, in order to apply the correct set of transit
   routing policies, it needs to know from which of its customers, i.e.,
   adjacent upstream network, the SIP request is received.

2.  Applicability

   The mechanism defined in this specification MUST only be used by SIP
   entities that are able to verify from which adjacent upstream network
   a SIP request is received.

   The mechanism for verifying from which adjacent upstream network a
   SIP request is received is outside the scope of this specification.
   Such mechanism might be based for instance on receiving the SIP
   request on an authenticated Virtual Private Network (VPN), receiving
   the SIP request on a specific IP address, or on a specific network
   access.

3.  Conventions

   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].

4.  Definitions

   SIP entity: SIP User Agent (UA), or SIP proxy, as defined in RFC
   3261.

   Adjacent upstream SIP network: The adjacent SIP network in the
   direction from which a SIP request is received.

   Network entry point: A SIP entity on the border of network, which
   receives SIP requests from adjacent upstream networks.

   Inter Operator Identifier (IOI): A globally unique identifier to
   correlate billing information generated within the IP Multimedia
   Subsystem (IMS).

   JWS: JSON Web Signature, as defined in [RFC7515].



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5.  Via 'received-realm' header field parameter

5.1.  General

   The Via 'received-realm' header field parameter value is represented
   as a combination of an operator identifier, whose value represents
   the adjacent network, and a serialized JSON Web Signature (JWS)
   [RFC7515].  The JWS Payload consists of the operator identifier and
   other SIP information element values.

   The procedures for encoding the JWS and calculating the signature are
   defined in [RFC7515].  As the JWS Payload information is found in
   other SIP information elements, the JWS Payload is detached from the
   serialized JWS conveyed in the header field parameter, as described
   in Appendix F of [RFC7515].  The operator identifier and the
   serialized JWS are separated using a colon character.

5.2.  Operator Identifier

   The Operator Identifier is a token value that represents the adjacent
   operator.  The scope of the value is only within the network that
   inserts the value.

   The Operator Identifier value is case-insensitive.

5.3.  JWS Header

   The following header parameters MUST be included in the JWS.

   o  The "typ" parameter MUST have a "JWT" value.

   o  The "alg" parameter MUST have the value of the algorithm used to
      calculate the JWS.

   NOTE: Operators need to agree on the set of supported algorithms for
   calculating the JWT signature.

   NOTE: The "alg" parameter values for specific algorithms are listed
   in the IANA JSON Web Signature and Encryption Algorithms sub-registry
   of the JSON Object Signing and Encryption (JOSE) registry.  Operators
   need to use algorithms for which an associated "alg" parameter value
   has been registered.  The procedures for defining new values are
   defined in [RFC7518].








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   Example:

   {
           "typ":"JWT",
           "alg":"HS256"
   }


5.4.  JWS Payload

   The following claims MUST be included in the JWS Payload:

   o  The "sip_from_tag" claim has the value of the From 'tag' header
      field parameter of the SIP message.

   o  The "sip_date" claim has the value of the Date header field in the
      SIP message, encoded in JSON NumericDate format [RFC7519].

   o  The "sip_callid" claim has have value of the Call-ID header field
      in the SIP message.

   o  The "sip_cseq_num" claim has the numeric value of the CSeq header
      field in the SIP message.

   o  the "sip_via_branch" claim has value of the Via branch header
      field parameter of the Via header field, in the SIP message, to
      which the received-realm header field parameter is attached.

   o  the "sip_via_opid" claim has value of the operator identifier part
      of the Via received-realm header field parameter of the Via header
      field, in the SIP message, to which the received-realm header
      field parameter is attached.


   Example:

   {
           "sip_from_tag":"1928301774",
           "sip_date":1472815523,
           "sip_callid":"a84b4c76e66710@pc33.atlanta.com",
           "sip_cseq_num":"314159",
           "sip_via_branch":"z9hG4bK776asdhds",
           "sip_via_opid":"myoperator"
   }







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5.5.  JWS Serialization

   As the JWS Payload is not carried in the received-realm parameter, in
   order to make sure that the sender and the receiver construct the JWS
   Payload object in the same way, the JSON representation of the JWS
   Payload object it MUST be computed as follows:

   o  All claims MUST be encoded using lower case characters.

   o  The claims MUST be in the same order as listed in [Section 5.4].

   o  All claims except "sip_date" MUST be encoded as StringOrURI JSON
      string value [RFC7519].

   o  The "sip_date" claim MUST be encoded as a JSON NumericDate value
      [RFC7519].

   o  The JWS Payload MUST follow the rules for the construction of the
      thumbprint of a JSON Web Key (JWK) as defined in [RFC7638]
      Section 3 Step 1 only.


 Example:

 NOTE: Line breaks for display purpose only

 {"sip_from_tag":"1928301774","sip_date":1472815523,
 "sip_callid":"a84b4c76e66710@pc33.atlanta.com","sip_cseq_num":"314159",
 "sip_via_branch":"z9hG4bK776asdhds","sip_via_opid":"myoperator"}


5.6.  Syntax

5.6.1.  General

   This section describes the syntax extensions to the ABNF syntax
   defined in [RFC3261], by defining a new Via header field parameter,
   "received-realm".  The ABNF defined in this specification is
   conformant to RFC 5234 [RFC5234].  "EQUAL", "LDQUOT", "RDQUOT" and
   "ALPHA" are defined in [RFC3261].  "DIGIT" is defined in [RFC5234].

5.6.2.  ABNF









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   via-params     =/ received-realm
   received-realm = "received-realm" EQUAL LDQUOT op-id COLON jws RDQUOT
   op-id          = token
   jws            = header ".." signature
   header         = 1*base64-char
   signature      = 1*base64-char
   base64-char    = ALPHA / DIGIT / "/" / "+"

   EQUAL, COLON, token, LDQUOT, RDQUOT, ALPHA and DIGIT
   as defined in [RFC3261].

   NOTE: The two adjacent dots in the jws part is due to the detached
   payload being replaced by an empty string [RFC7515].


5.7.  Example


     Via: SIP/2.0/UDP pc33.example.com;branch=z9hG4bK776;
     received-realm="myoperator:eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1N..
     dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW1gFWFOEjXk"

     NOTE: Line breaks for display purpose only


6.  User Agent and Proxy behavior

6.1.  General

   This section describes how a SIP entity, acting as an entry point to
   a network, uses the "received-realm" Via header field parameter.

6.2.  Behavior of a SIP entity acting as a network entry point

   When a SIP entity, acting as a network entry point, forwards a SIP
   request, or initiates a SIP request on its own (e.g., a PSTN
   gateway), the SIP entity adds a Via header field to the SIP request,
   according to the procedures in RFC 3261 [RFC3261].  In addition, if
   the SIP entity is able to assert the adjacent upstream network, and
   if the SIP entity is aware of a network realm value defined for that
   network, the SIP entity can add a "received-realm" Via header field
   parameter, conveying the network realm value as the operator
   identifier (Section 5.2) part of the header field parameter, to the
   Via header field added to the SIP request.

   In addition the SIP entity MUST also calculate a JWS (Section 5.4)
   and add the calculated JWS Header and JWS Signature as the jws part
   of the Via header field parameter.



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6.3.  Behavior of a SIP entity consuming the received-network value

   When a SIP entity receives a Via 'received-network' header field
   parameter, and intends to perform actions based on the header field
   parameter value, it MUST first re-calculate the JWS and check whether
   the result matches the JWS received.  If there is not a match, the
   SIP entity MUST discard the received 'received-network' header field
   parameter.  The SIP entity MAY take also take additional actions
   (e.g., rejecting the SIP request) based on local policy.

7.  Example


 Operator 1    T_EP                                 T_AS

 - INVITE ------>
   Via: SIP/2.0/UDP IP_UA
                 -- INVITE ---------------------------->
                    Via: SIP/2.0/UDP IP_TEP;branch=z9hG4bK776;
                     received-realm="myoperator:eyJ0eXAiOiJKV1QiLA0KICJh
                     bGciOiJIUzI1N..dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW
                     1gFWFOEjXk"
                    Via: SIP/2.0/UDP IP_UA; received=IP_UA

                 <- 200 OK ----------------------------
                    Via: SIP/2.0/UDP IP_TEP;branch=z9hG4bK776;
                     received-realm="myoperator:eyJ0eXAiOiJKV1QiLA0KICJh
                     bGciOiJIUzI1N..dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW
                     1gFWFOEjXk"
                    Via: SIP/2.0/UDP IP_UA; received=IP_UA

 <- 200 OK------
    Via: SIP/2.0/UDP IP_UA; received=IP_UA


8.  IANA Considerations

8.1.  'received-realm' Via header field parameter

   This specification defines a new Via header field parameter called
   received-realm in the "Header Field Parameters and Parameter Values"
   sub-registry as per the registry created by [RFC3968].  The syntax is
   defined in Section 5.6.  The required information is:








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                                                  Predefined
   Header Field            Parameter Name         Values      Reference
   ----------------------  ---------------------  ----------  ---------
   Via                     received-realm         No          RFCXXXX


8.2.  JSON Web Token Claims Registration

   This specification defines new JSON Web Token claims in the "JSON Web
   Token Claims" sub-registry as per the registry created by [RFC7519].

      Claim Name: "sip_from_tag"

      Claim : SIP From tag header field parameter value

      Change Controller: IESG

      Specification Document(s): RFC XXXX, RFC 3261

      Claim Name: "sip_date"

      Claim Description: SIP Date header field value

      Change Controller: IESG

      Specification Document(s): RFC XXXX, RFC 3261

      Claim Name: "sip_callid"

      Claim Description: SIP Call-Id header field value

      Change Controller: IESG

      Specification Document(s): RFC XXXX, RFC 3261

      Claim Name: "sip_cseq_num"

      Claim Description: SIP CSeq numeric header field parameter value

      Change Controller: IESG

      Specification Document(s): RFC XXXX, RFC 3261

      Claim Name: "sip_via_branch"

      Claim Description: SIP Via branch header field parameter value

      Change Controller: IESG



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      Specification Document(s): RFC XXXX, RFC 3261

9.  Security Considerations

   As the received-realm Via header field parameter can be used to
   trigger applications, it is important to ensure that the parameter
   has not been added to the SIP message by an unauthorized SIP entity.

   The received-realm Via header field parameter is inserted, signed,
   verified and consumed within an operator network.  The operator MUST
   discard parameters received from another network, and the parameter
   MUST only be inserted by SIP entities that are able to verify from
   which adjacent upstream network a SIP request is received.

   The operator also needs to take great care in ensuring that the key
   used to calculate the JWS signature value is only known by the
   network entities signing and adding the JWS signature to the
   received-realm Via header field parameter of a SIP message, and to
   network entities verifying and consuming the parameter value.

   The operator MUST use a key management policy that protects agains
   unauthorised access to the stored keys within nodes where they keys
   associated with the JWS signature are stored, and that protects
   against crypto analysis attacks using captured data sent on the wire.

   A SIP entity MUST NOT use the adjacent network information if there
   is a mismatch between the JWS signature received in the SIP header
   field and the JWS signature calculated by the receiving entity.

   Generic security considerations for JWS are defined in [RFC7515].

10.  Acknowledgments

   Thanks to Adam Roach and Richard Barnes for providing comments and
   feedback on the document.  Francis Dupoint performed the Gen-ART
   review.

11.  Change Log

   [RFC EDITOR NOTE: Please remove this section when publishing]

   Changes from draft-holmberg-dispatch-received-realm-11

   o  Editorial change based on IESG review.

   Changes from draft-holmberg-dispatch-received-realm-10

   o  Changes based on IESG review.



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   o  Changes based on SecDIR review.

   o  Changes based on IANA Service Operator review.

   Changes from draft-holmberg-dispatch-received-realm-09

   o  Reference to RFC 2104 removed.

   Changes from draft-holmberg-dispatch-received-realm-08

   o  Editorial fixed based on Gen-ART review.

   o  Editorial fixes based on comments from IANA Service Operator
      review.

   o  - Quotes removed from sip_date value.

   Changes from draft-holmberg-dispatch-received-realm-07

   o  Editorial changes.

   Changes from draft-holmberg-dispatch-received-realm-06

   o  Changes based on AD review by Ben Campbell:

   o  - operator-id added to JSON Payload

   Changes from draft-holmberg-dispatch-received-realm-05

   o  Editorial fixes.

   Changes from draft-holmberg-dispatch-received-realm-04

   o  JSON serialization procedure added.

   Changes from draft-holmberg-dispatch-received-realm-03

   o  ABNF correction.

   Changes from draft-holmberg-dispatch-received-realm-02

   o  JWT replaced with JWS.

   o  Appendix F of RFC 7515 applied.

   Changes from draft-holmberg-dispatch-received-realm-01

   o  Define received-realm parameter value as a JSON Web Token (JWT).



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   Changes from draft-holmberg-dispatch-received-realm-00

   o  New version due to expiration of previous version.

   Changes from draft-holmberg-received-realm-04

   o  Changed IETF WG from sipcore do dispatch.

   o  HMAC value added to the parameter.

   Changes from draft-holmberg-received-realm-03

   o  New version due to expiration.

   Changes from draft-holmberg-received-realm-02

   o  New version due to expiration.

   Changes from draft-holmberg-received-realm-01

   o  New version due to expiration.

   Changes from draft-holmberg-received-realm-00

   o  New version due to expiration.

12.  References

12.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC3261]  Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
              A., Peterson, J., Sparks, R., Handley, M., and E.
              Schooler, "SIP: Session Initiation Protocol", RFC 3261,
              DOI 10.17487/RFC3261, June 2002,
              <http://www.rfc-editor.org/info/rfc3261>.

   [RFC5234]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", STD 68, RFC 5234,
              DOI 10.17487/RFC5234, January 2008,
              <http://www.rfc-editor.org/info/rfc5234>.






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   [RFC7515]  Jones, M., Bradley, J., and N. Sakimura, "JSON Web
              Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May
              2015, <http://www.rfc-editor.org/info/rfc7515>.

   [RFC7519]  Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
              (JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015,
              <http://www.rfc-editor.org/info/rfc7519>.

   [RFC7638]  Jones, M. and N. Sakimura, "JSON Web Key (JWK)
              Thumbprint", RFC 7638, DOI 10.17487/RFC7638, September
              2015, <http://www.rfc-editor.org/info/rfc7638>.

12.2.  Informative References

   [RFC3968]  Camarillo, G., "The Internet Assigned Number Authority
              (IANA) Header Field Parameter Registry for the Session
              Initiation Protocol (SIP)", BCP 98, RFC 3968,
              DOI 10.17487/RFC3968, December 2004,
              <http://www.rfc-editor.org/info/rfc3968>.

   [RFC7518]  Jones, M., "JSON Web Algorithms (JWA)", RFC 7518,
              DOI 10.17487/RFC7518, May 2015,
              <http://www.rfc-editor.org/info/rfc7518>.

   [TS.3GPP.23.228]
              3GPP, "IP Multimedia Subsystem (IMS); Stage 2", 3GPP
              TS 23.228 14.1.0, September 2016.

Authors' Addresses

   Christer Holmberg
   Ericsson
   Hirsalantie 11
   Jorvas  02420
   Finland

   Email: christer.holmberg@ericsson.com


   Yi Jiang
   China Mobile
   No.32 Xuanwumen West Street
   Beijing  Xicheng District 100053
   P.R. China

   Email: jiangyi@chinamobile.com





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