ftp.cc.uoc.gr
rfc3182
This is a purely informative rendering of an RFC that includes verified errata. This rendering may not be used as a reference.

The following 'Verified' errata have been incorporated in this document: EID 2958
Network Working Group                                           S. Yadav
Request for Comments: 3182                                   R. Yavatkar
Obsoletes: 2752                                                    Intel
Category: Standards Track                                     R. Pabbati
                                                                 P. Ford
                                                                T. Moore
                                                               Microsoft
                                                               S. Herzog
                                                    PolicyConsulting.Com
                                                                 R. Hess
                                                                   Intel
                                                            October 2001


                    Identity Representation for RSVP

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2001).  All Rights Reserved.

Abstract

   This document describes the representation of identity information in
   POLICY_DATA object for supporting policy based admission control in
   the Resource ReSerVation Protocol (RSVP).  The goal of identity
   representation is to allow a process on a system to securely identify
   the owner and the application of the communicating process (e.g.,
   user id) and convey this information in RSVP messages (PATH or RESV)
   in a secure manner.  We describe the encoding of identities as RSVP
   policy element.  We describe the processing rules to generate
   identity policy elements for multicast merged flows.  Subsequently,
   we describe representations of user identities for Kerberos and
   Public Key based user authentication mechanisms.  In summary, we
   describe the use of this identity information in an operational
   setting.

   This memo corrects an RSVP POLICY_DATA P-Type codepoint assignment
   error and a field size definition error in ErrorValue in RFC 2752.

1. 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 [RFC 2119].

2. Introduction

   RSVP [RFC 2205] is a resource reservation setup protocol designed for
   an integrated services Internet [RFC 1633].  RSVP is used by a host
   to request specific quality of service (QoS) from the network for
   particular application data streams or flows.  RSVP is also used by
   routers to deliver QoS requests to all nodes along the path(s) of the
   flows and to establish and maintain state to provide the requested
   service.  RSVP requests will generally result in resources being
   reserved in each node along the data path.  RSVP allows particular
   users to obtain preferential access to network resources, under the
   control of an admission control mechanism.  Permission to make a
   reservation is based both upon the availability of the requested
   resources along the path of the data and upon satisfaction of policy
   rules.  Providing policy based admission control mechanism based on
   user identity or application is one of the prime requirements.

   In order to solve these problems and implement identity based policy
   control it is required to identify the user and/or application making
   a RSVP request.

   This document proposes a mechanism for sending identification
   information in the RSVP messages and enables authorization decisions
   based on policy and identity.

   We describe the authentication policy element (AUTH_DATA) contained
   in the POLICY_DATA object.  User process can generate an AUTH_DATA
   policy element and gives it to RSVP process (service) on the
   originating host.  RSVP service inserts AUTH_DATA into the RSVP
   message to identify the owner (user and/or application) making the
   request for network resources.  Network elements, such as routers,
   authenticate request using the credentials presented in the AUTH_DATA
   and admit the RSVP message based on admission policy.  After a
   request has been authenticated, first hop router installs the RSVP
   state and forwards the new policy element returned by the Policy
   Decision Point (PDP) [POL-FRAME].

3. Policy Element for Authentication Data

3.1 Policy Data Object Format

   POLICY_DATA objects contain policy information and are carried by
   RSVP messages.  A detail description of the format of POLICY_DATA
   object can be found in "RSVP Extensions for Policy Control" [POL-
   EXT].

3.2 Authentication Data Policy Element

   In this section, we describe a policy element (PE) called
   authentication data (AUTH_DATA).  AUTH_DATA policy element contains a
   list of authentication attributes.

      +-------------+-------------+-------------+-------------+
      | Length                    | P-Type = Identity Type    |
      +-------------+-------------+-------------+-------------+
      // Authentication Attribute List                       //
      +-------------------------------------------------------+

   Length
      The length of the policy element (including the Length and P-Type)
      is in number of octets (MUST be a multiple of 4) and indicates the
      end of the authentication attribute list.

   P-Type (Identity Type)
      Type of identity information contained in this Policy Element
      supplied as the Policy element type (P-type).  The Internet
      Assigned Numbers Authority (IANA) acts as a registry for policy
      element types for identity as described in the [POL-EXT].
      Initially, the registry contains the following P-Types for
      identity:

      2   AUTH_USER       Authentication scheme to identify users

      3   AUTH_APP        Authentication scheme to identify
                          applications

   Authentication Attribute List

      Authentication attributes contain information specific to
      authentication method and type of AUTH_DATA.  The policy element
      provides the mechanism for grouping a collection of authentication
      attributes.

3.3 Authentication Attributes

   Authentication attributes MUST be encoded as a multiple of 4 octets,
   attributes that are not a multiple of 4 octets long MUST be padded to
   a 4-octet boundary.

   +--------+--------+--------+--------+
   | Length          | A-Type |SubType |
   +--------+--------+--------+--------+
   | Value ...
   +--------+--------+--------+--------+

   Length
      The length field is two octets and indicates the actual length of
      the attribute (including the Length and A-Type fields) in number
      of octets.  The length does not include any bytes padding to the
      value field to make the attribute multiple of 4 octets long.

   A-Type
      Authentication attribute type (A-Type) field is one octet.  IANA
      acts as a registry for A-Types as described in the section 8,
      IANA Considerations.  Initially, the registry contains the
      following A-Types:

      1  POLICY_LOCATOR      Unique string for locating the
                             admission policy (such as X.500 DN
                             described in [RFC 1779]).

      2  CREDENTIAL          User credential such as Kerberos
                             ticket, or digital certificate.
                             Application credential such as
                             application ID.

      3  DIGITAL_SIGNATURE   Digital signature of the
                             authentication data policy element.

      4  POLICY_ERROR_OBJECT Detailed information on policy
                             failures.

   SubType
      Authentication attribute sub-type field is one octet.  Value of
      SubType depends on A-type.

   Value:
      The value field contains the attribute specific information.

3.3.1 Policy Locator

   POLICY_LOCATOR is used to locate the admission policy for the user or
   application.  Distinguished Name (DN) is unique for each User or
   application hence a DN is used as policy locator.

   +-------+-------+-------+-------+
   | Length        |A-Type |SubType|
   +-------+-------+-------+-------+
   | OctetString ...
   +-------+-------+-------+--------

   Length
      Length of the attribute, which MUST be >= 4.

   A-Type
      POLICY_LOCATOR

   SubType
      Following sub types for POLICY_LOCATOR are defined.  IANA acts as
      a registry for POLICY_LOCATOR sub types as described in the
      section 8, IANA Considerations.  Initially, the registry contains
      the following sub types for POLICY_LOCATOR:

      1  ASCII_DN            OctetString contains the X.500 DN as
                             described in the RFC 1779 as an ASCII
                             string.

      2  UNICODE_DN          OctetString contains the X.500 DN described
                             in the RFC 1779 as an UNICODE string.

      3  ASCII_DN_ENCRYPT    OctetString contains the encrypted X.500
                             DN.  The Kerberos session key or digital
                             certificate private key is used for
                             encryption.  For Kerberos encryption the
                             format is the same as returned from
                             gss_seal [RFC 1509].

      4  UNICODE_DN_ENCRYPT  OctetString contains the encrypted UNICODE
                             X.500 DN.  The Kerberos session key or
                             digital certificate private key is used for
                             encryption.  For Kerberos encryption the
                             format is the same as returned from
                             gss_seal [RFC 1509].

   OctetString
      The OctetString field contains the DN.

3.3.2 Credential

   CREDENTIAL indicates the credential of the user or application to be
   authenticated.  For Kerberos authentication method the CREDENTIAL
   object contains the Kerberos session ticket.  For public key based
   authentication this field contains a digital certificate.

   A summary of the CREDENTIAL attribute format is shown below.  The
   fields are transmitted from left to right.

   +-------+-------+-------+-------+
   | Length        |A-Type |SubType|
   +-------+-------+-------+-------+
   | OctetString ...
   +-------+-------+-------+--------

   Length
      Length of the attribute, which MUST be >= 4.

   A-Type
      CREDENTIAL

   SubType
      IANA acts as a registry for CREDENTIAL sub types as described in
      the section 8, IANA Considerations.  Initially, the registry
      contains the following sub types for CREDENTIAL:

      1  ASCII_ID       OctetString contains user or application
                        identification in plain ASCII text string.

      2  UNICODE_ID     OctetString contains user or application
                        identification in plain UNICODE text string.

      3  KERBEROS_TKT   OctetString contains Kerberos ticket.

      4  X509_V3_CERT   OctetString contains X.509 V3 digital
                        certificate [X.509].

      5  PGP_CERT       OctetString contains PGP digital certificate.

   OctetString
      The OctetString contains the user or application credential.

3.3.3 Digital Signature

   The DIGITAL_SIGNATURE attribute MUST be the last attribute in the
   attribute list and contains the digital signature of the AUTH_DATA
   policy element.  The digital signature signs all data in the
   AUTH_DATA policy element up to the DIGITAL_SIGNATURE.  The algorithm
   used to compute the digital signature depends on the authentication
   method specified by the CREDENTIAL SubType field.

   A summary of DIGITAL_SIGNATURE attribute format is described below.

   +-------+-------+-------+-------+
   | Length        |A-Type |SubType|
   +-------+-------+-------+-------+
   | OctetString ...
   +-------+-------+-------+--------

   Length
      Length of the attribute, which MUST be >= 4.

   A-Type
      DIGITAL_SIGNATURE

   SubType
      No sub types for DIGITAL_SIGNATURE are currently defined.  This
      field MUST be set to 0.

   OctetString
      OctetString contains the digital signature of the AUTH_DATA.

3.3.4 Policy Error Object

   This attribute is used to carry any specific policy control errors
   generated by a node when processing/validating an Authentication Data
   Policy Element.  When a RSVP policy node (local policy decision point
   or remote PDP) encounters a request that fails policy control due to
   its Authentication Policy Element, it SHOULD add a POLICY_ERROR_CODE
   containing additional information about the reason the failure
   occurred into the policy element.  This will then cause an
   appropriate PATH_ERROR or RESV_ERROR message to be generated with the
   policy element and appropriate RSVP error code in the message, which
   is returned to the request's source.

   The AUTH_DATA policy element in the PATH or RSVP message SHOULD not
   contain the POLICY_ERROR_OBJECT attribute.  These are only inserted
   into PATH_ERROR and RESV_ERROR messages when generated by policy
   aware intermediate nodes.

   +----------+----------+----------+----------+
   | Length              | A-Type   | SubType  |
   +----------+----------+----------+----------+
   | 0 (Reserved)        | ErrorValue          |
   +----------+----------+----------+----------+
   | OctetString ...
   +----------+----------+----------+----------+

   Length
      Length of the attribute, which MUST be >= 8.

   A-Type
      POLICY_ERROR_CODE

   SubType
      No sub types for POLICY_ERROR_CODE are currently defined.  This
      field MUST be set to 0.

   ErrorValue
      A 16-bit bit code containing the reason that the policy decision
      point failed to process the policy element.  IANA acts as a
      registry for ErrorValues as described in section 8, IANA
      Considerations.  Following values have been defined.

      1  ERROR_NO_MORE_INFO           No information is available.
      2  UNSUPPORTED_CREDENTIAL_TYPE  This type of credentials is
                                      not supported.

      3  INSUFFICIENT_PRIVILEGES      The credentials do not have
                                      sufficient privilege.

      4  EXPIRED_CREDENTIAL           The credential has expired.

      5  IDENTITY_CHANGED             Identity has changed.

   OctetString
      The OctetString field contains information from the policy
      decision point that MAY contain additional information about the
      policy failure.  For example, it may include a human-readable
      message in the ASCII text.

4. Authentication Data Formats

   Authentication attributes are grouped in a policy element to
   represent the identity credentials.

4.1 Simple User Authentication

   In simple user authentication method the user login ID (in plain
   ASCII or UNICODE text) is encoded as CREDENTIAL attribute.  A summary
   of the simple user AUTH_DATA policy element is shown below.

   +--------------+--------------+--------------+--------------+
   | Length                      | P-type = AUTH_USER          |
   +--------------+--------------+--------------+--------------+
   | Length                      |POLICY_LOCATOR| SubType      |
   +--------------+--------------+--------------+--------------+
   | OctetString (User's Distinguished Name) ...
   +--------------+--------------+--------------+--------------+
   | Length                      |CREDENTIAL    | ASCII_ID     |
   +--------------+--------------+--------------+--------------+
   | OctetString (User's login ID) ...
   +--------------+--------------+--------------+--------------+

4.2 Kerberos User Authentication

   Kerberos [RFC 1510] authentication uses a trusted third party (the
   Kerberos Distribution Center - KDC) to provide for authentication of
   the user to a network server.  It is assumed that a KDC is present
   and both host and verifier of authentication information (router or
   PDP) implement Kerberos authentication.

   A summary of the Kerberos AUTH_DATA policy element is shown below.

   +--------------+--------------+--------------+--------------+
   | Length                      | P-type = AUTH_USER          |
   +--------------+--------------+--------------+--------------+
   | Length                      |POLICY_LOCATOR|   SubType    |
   +--------------+--------------+--------------+--------------+
   | OctetString (User's Distinguished Name) ...
   +--------------+--------------+--------------+--------------+
   | Length                      | CREDENTIAL   | KERBEROS_TKT |
   +--------------+--------------+--------------+--------------+
   | OctetString (Kerberos Session Ticket) ...
   +--------------+--------------+--------------+--------------+

4.2.1. Operational Setting using Kerberos Identities

   An RSVP enabled host is configured to construct and insert AUTH_DATA
   policy element into RSVP messages that designate use of the Kerberos
   authentication method (KERBEROS_TKT).  Upon RSVP session
   initialization, the user application contacts the KDC to obtain a
   Kerberos ticket for the next network node or its PDP.  A router when
   generating a RSVP message contacts the KDC to obtain a Kerberos

   ticket for the next hop network node or its PDP.  The identity of the
   PDP or next network hop can be statically configured, learned via
   DHCP or maintained in a directory service.  The Kerberos ticket is
   sent to the next network node (which may be a router or host) in a
   RSVP message.  The KDC is used to validate the ticket and
   authentication the user sending RSVP message.

4.3 Public Key based User Authentication

   In public key based user authentication method digital certificate is
   encoded as user credentials.  The digital signature is used for
   authenticating the user.  A summary of the public key user AUTH_DATA
   policy element is shown below.

   +--------------+--------------+--------------+--------------+
   | Length                      | P-type = AUTH_USER          |
   +--------------+--------------+--------------+--------------+
   | Length                      |POLICY_LOCATOR|   SubType    |
   +--------------+--------------+--------------+--------------+
   | OctetString (User's Distinguished Name) ...
   +--------------+--------------+--------------+--------------+
   | Length                      | CREDENTIAL   |   SubType    |
   +--------------+--------------+--------------+--------------+
   | OctetString (User's Digital Certificate) ...
   +--------------+--------------+--------------+--------------+
   | Length                      |DIGITAL_SIGN. | 0            |
   +--------------+--------------+--------------+--------------+
   | OctetString (Digital signature) ...
   +--------------+--------------+--------------+--------------+

4.3.1. Operational Setting for public key based authentication

   Public key based authentication assumes following:

      -  RSVP service requestors have a pair of keys (private key and
         public key).

      -  Private key is secured with the user.

      -  Public keys are stored in digital certificates and a trusted
         party, certificate authority (CA) issues these digital
         certificates.

      -  The verifier (PDP or router) has the ability to verify the
         digital certificate.

   RSVP requestor uses its private key to generate DIGITAL_SIGNATURE.
   User Authenticators (router, PDP) use the user's public key (stored
   in the digital certificate) to verify the signature and authenticate
   the user.

4.4 Simple Application Authentication

   The application authentication method encodes the application
   identification such as an executable filename as plain ASCII or
   UNICODE text.

   +----------------+--------------+--------------+--------------+
   | Length                        | P-type = AUTH_APP           |
   +----------------+--------------+--------------+--------------+
   | Length                        |POLICY_LOCATOR| SubType      |
   +----------------+--------------+--------------+--------------+
   | OctetString (Application Identity attributes in
   |              the form of  a Distinguished Name) ...
   +----------------+--------------+--------------+--------------+
   | Length                        | CREDENTIAL   | ASCII_ID     |
   +----------------+--------------+--------------+--------------+
   | OctetString (Application Id, e.g., vic.exe)
   +----------------+--------------+--------------+--------------+

5. Operation

   +-----+                                                  +-----+
   | PDP |-------+                                          | PDP |
   +-----+       |             ...................          +-----+
                 |             :                 :          |
               +--------+      :     Transit     :        +-------+
          +----| Router |------:     Network     : -------| Router|--+
          |    +--------+      :                 :        +-------+  |
          |        |           :.................:             |     |
          |        |                                           |     |
     Host A        B                                           C     D

     Figure 1: User and Application Authentication using AUTH_DATA PE

   Network nodes (hosts/routers) generate AUTH_DATA policy elements,
   contents of which are depend on the identity type used and the
   authentication method used.  These generally contain authentication
   credentials (Kerberos ticket or digital certificate) and policy
   locators (which can be the X.500 Distinguished Name of the user or
   network node or application names).  Network nodes generate AUTH_DATA
   policy element containing the authentication identity when making the
   RSVP request or forwarding a RSVP message.

   Network nodes generate user AUTH_DATA policy element using the
   following rules:

   1. For unicast sessions the user policy locator is copied from the
      previous hop.  The authentication credentials are for the current
      network node identity.

   2. For multicast messages the user policy locator is for the current
      network node identity.  The authentication credentials are for the
      current network node.

   Network nodes generate application AUTH_DATA policy element using the
   following rules:

   1. For unicast sessions the application AUTH_DATA is copied from the
      previous hop.

   2. For multicast messages the application AUTH_DATA is either the
      first application AUTH_DATA in the message or chosen by the PDP.

6. Message Processing Rules

6.1 Message Generation (RSVP Host)

   An RSVP message is created as specified in [RFC 2205] with following
   modifications.

   1. RSVP message MAY contain multiple AUTH_DATA policy elements.

   2. Authentication policy element (AUTH_DATA) is created and the
      IdentityType field is set to indicate the identity type in the
      policy element.

      -  DN is inserted as POLICY_LOCATOR attribute.

      -  Credentials such as Kerberos ticket or digital certificate are
         inserted as the CREDENTIAL attribute.

   3. POLICY_DATA object (containing the AUTH_DATA policy element) is
      inserted in the RSVP message in appropriate place.  If INTEGRITY
      object is not computed for the RSVP message then an INTEGRITY
      object SHOULD be computed for this POLICY_DATA object, as
      described in the [POL_EXT], and SHOULD be inserted as a Policy
      Data option.

6.2 Message Reception (Router)

   RSVP message is processed as specified in [RFC 2205] with following
   modifications.

   1. If router is not policy aware then it SHOULD send the RSVP message
      to the PDP and wait for response.  If the router is policy unaware
      then it ignores the policy data objects and continues processing
      the RSVP message.

   2. Reject the message if the response from the PDP is negative.

   3. Continue processing the RSVP message.

6.3 Authentication (Router/PDP)

EID 2958 (Verified) is as follows:

Section: 6.3

Original Text:

6.3 Authentication (Router/PDP)

[..]

   2. Verify user credential

[..]

      -  Kerberos: Send the Kerberos ticket to the KDC to obtain the
         session key.  Using the session key authenticate the user.

Corrected Text:

Kerberos: Extract the session key from the ticket. Use the session key to authenticate the user.
Notes:
The corrected text is only an example. The most important point is that Kerberos doesn't require the server to contact the KDC, all the information is already in the kerberos authenticator and ticket sent by the client.

See this email exchange from 2001 :-) http://psg.com/lists/rap/rap.2001/msg00269.html where the same issue is raised by Hannes Tschofenig and confirmed by one of the RFC authors, R. Hess.
1. Retrieve the AUTH_DATA policy element. Check the PE type field and return an error if the identity type is not supported. 2. Verify user credential - Simple authentication: e.g., Get user ID and validate it, or get executable name and validate it. - Kerberos: Send the Kerberos ticket to the KDC to obtain the session key. Using the session key authenticate the user. - Public Key: Validate the certificate that it was issued by a trusted Certificate Authority (CA) and authenticate the user or application by verifying the digital signature. 7. Error Signaling If PDP fails to verify the AUTH_DATA policy element then it MUST return policy control failure (Error Code = 02) to the PEP. The error values are described in [RFC 2205] and [POL-EXT]. Also PDP SHOULD supply a policy data object containing an AUTH_DATA Policy Element with A-Type=POLICY_ERROR_CODE containing more details on the Policy Control failure (see section 3.3.4). The PEP will include this Policy Data object in the outgoing RSVP Error message. 8. IANA Considerations Following the policies outlined in [IANA-CONSIDERATIONS], Standard RSVP Policy Elements (P-type values) are assigned by IETF Consensus action as described in [POL-EXT]. P-Type AUTH_USER is assigned the value 2. P-Type AUTH_APP is assigned the value 3. Following the policies outlined in [IANA-CONSIDERATIONS], authentication attribute types (A-Type) in the range 0-127 are allocated through an IETF Consensus action, A-Type values between 128-255 are reserved for Private Use and are not assigned by IANA. A-Type POLICY_LOCATOR is assigned the value 1. A-Type CREDENTIAL is assigned the value 2. A-Type DIGITAL_SIGNATURE is assigned the value 3. A-Type POLICY_ERROR_OBJECT is assigned the value 4. Following the policies outlined in [IANA-CONSIDERATIONS], POLICY_LOCATOR SubType values in the range 0-127 are allocated through an IETF Consensus action, POLICY_LOCATOR SubType values between 128-255 are reserved for Private Use and are not assigned by IANA. POLICY_LOCATOR SubType ASCII_DN is assigned the value 1, SubType UNICODE_DN is assigned the value 2, SubType ASCII_DN_ENCRYPT is assigned the value 3 and SubType UNICODE_DN_ENCRYPT is assigned the value 4. Following the policies outlined in [IANA-CONSIDERATIONS], CREDENTIAL SubType values in the range 0-127 are allocated through an IETF Consensus action, CREDENTIAL SubType values between 128-255 are reserved for Private Use and are not assigned by IANA. CREDENTIAL SubType ASCII_ID is assigned the value 1, SubType UNICODE_ID is assigned the value 2, SubType KERBEROS_TKT is assigned the value 3, SubType X509_V3_CERT is assigned the value 4, SubType PGP_CERT is assigned the value 5. Following the policies outlined in [IANA-CONSIDERATIONS], ErrorValues in the range 0-32767 are allocated through an IETF Consensus action, ErrorValues between 32768-65535 are reserved for Private Use and are not assigned by IANA. ErrorValue ERROR_NO_MORE_INFO is assigned the value 1, UNSUPPORTED_CREDENTIAL_TYPE is assigned the value 2, INSUFFICIENT_PRIVILEGES is assigned the value 3, EXPIRED_CREDENTIAL is assigned the value 4, and IDENTITY_CHANGED is assigned the value 5. 9. Security Considerations The purpose of this memo is to describe a mechanism to authenticate RSVP requests based on user identity in a secure manner. RSVP INTEGRITY object is used to protect the policy object containing user identity information from security (replay) attacks. Combining the AUTH_DATA policy element and the INTEGRITY object results in a secure access control that enforces authentication based on both the identity of the user and the identity of the originating node. Simple authentication does not contain credential that can be securely authenticated and is inherently less secured. The Kerberos authentication mechanism is reasonably well secured. User authentication using a public key certificate is known to provide the strongest security. 10. Acknowledgments We would like to thank Andrew Smith, Bob Lindell and many others for their valuable comments on this memo. 11. References [ASCII] Coded Character Set -- 7-Bit American Standard Code for Information Interchange, ANSI X3.4- 1986. [IANA-CONSIDERATIONS] Alvestrand, H. and T. Narten, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 2434, October 1998. [POL-EXT] Herzog, S., "RSVP Extensions for Policy Control", RFC 2750, January 2000. [POL-FRAME] Yavatkar, R., Pendarakis, D. and R. Guerin, "A Framework for Policy-based Admission Control RSVP", RFC 2753, January 2000. [RFC 1510] Kohl, J. and C. Neuman, "The Kerberos Network Authentication Service (V5)", RFC 1510, September 1993. [RFC 1704] Haller, N. and R. Atkinson, "On Internet Authentication", RFC 1704, October 1994. [RFC 1779] Killie, S., "A String Representation of Distinguished Names", RFC 1779, March 1995. [RFC 2205] Braden, R., Zhang, L., Berson, S., Herzog, S. and S. Jamin, "Resource ReSerVation Protocol (RSVP) - Version 1 Functional Specification", RFC 2205, September 1997. [RFC 2209] Braden, R. and L. Zhang, "Resource ReSerVation Protocol (RSVP) - Version 1 Message Processing Rules", RFC 2209, September 1997. [RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC 2751] Herzog, S., "Signaled Preemption Priority Policy Element", RFC 2751, January 2000. [UNICODE] The Unicode Consortium, "The Unicode Standard, Version 2.0", Addison-Wesley, Reading, MA, 1996. [X.509] Housley, R., Ford, W., Polk, W. and D. Solo, "Internet X.509 Public Key Infrastructure Certificate and CRL Profile", RFC 2459, January 1999. [X.509-ITU] ITU-T (formerly CCITT) Information technology - Open Systems Interconnection - The Directory: Authentication Framework Recommendation X.509 ISO/IEC 9594-8 12. Authors' Addresses Satyendra Yadav Intel, JF3-206 2111 NE 25th Avenue Hillsboro, OR 97124 EMail: Satyendra.Yadav@intel.com Raj Yavatkar Intel, JF3-206 2111 NE 25th Avenue Hillsboro, OR 97124 EMail: Raj.Yavatkar@intel.com Ramesh Pabbati Microsoft 1 Microsoft Way Redmond, WA 98054 EMail: rameshpa@microsoft.com Peter Ford Microsoft 1 Microsoft Way Redmond, WA 98054 EMail: peterf@microsoft.com Tim Moore Microsoft 1 Microsoft Way Redmond, WA 98054 EMail: timmoore@microsoft.com Shai Herzog PolicyConsulting.Com 200 Clove Rd. New Rochelle, NY 10801 EMail: herzog@policyconsulting.com Rodney Hess Intel, BD1 28 Crosby Drive Bedford, MA 01730 EMail: rodney.hess@intel.com 13. 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