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Versions: 00 01 02 03 04 05 06 RFC 2750

Internet Draft                                            Shai Herzog
Expiration: October 1999                                      IPHighway
File: draft-ietf-rap-rsvp-ext-06.txt
Updates RFC 2205




                  RSVP Extensions for Policy Control


                             April 8, 1999



Status of this Memo

  This document is an Internet-Draft and is in full conformance with
  all provisions of Section 10 of RFC2026.

  Internet-Drafts are working documents of the Internet Engineering
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Abstract

   This memo presents a set of extensions for supporting generic policy
   based admission control in RSVP. It should be perceived as an
   extension to the RSVP functional specifications [RSVP]

   These extensions include the standard format of POLICY_DATA objects,
   and a description of RSVP's handling of policy events.

   This document does not advocate particular policy control
   mechanisms;
   however, a Router/Server Policy Protocol description for these
   extensions can be found in [RAP, COPS, COPS-RSVP].





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Table of Contents


Abstract.............................................................1
Table of Contents....................................................2
1 Introduction.......................................................3
2 A Simple Scenario..................................................3
3 Policy Data Objects................................................4
3.1  Base Format.....................................................4
3.2  Options.........................................................5
3.3  Policy Elements.................................................7
3.4  Purging Policy State............................................7
4 Processing Rules...................................................8
4.1  Basic Signaling.................................................8
4.2  Default Handling for PIN nodes..................................8
4.3  Error Signaling.................................................8
5 IANA Considerations................................................9
6 Security Considerations............................................9
7 References........................................................10
8 Acknowledgments...................................................10
9 Author Information................................................10
Appendix A : Policy Error Codes.....................................11
Appendix B : INTEGRITY computation for POLICY_DATA objects..........12






























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1  Introduction

  RSVP, by definition, discriminates between users, by providing some
  users with better service at the expense of others. Therefore, it is
  reasonable to expect that RSVP be accompanied by mechanisms for
  controlling and enforcing access and usage policies. Ver. 1 of the
  RSVP Functional Specifications [RSVP] left a placeholder for policy
  support in the form of POLICY_DATA object.

  The current RSVP Functional Specification describes the interface to
  admission (traffic) control that is based "only" on resource
  availability. In this document we describe a set of extensions to
  RSVP for supporting policy based admission control as well. The
  scope of this document is limited to these extensions and does not
  advocate specific architectures for policy based controls.

  For the purpose of this document we do not differentiate between
  Policy Decision Point (PDP) and Local Decision Point (LDPs) as
  described in [RAP]. The term PDP should be assumed to include LDP as
  well.

2  A Simple Scenario

  It is generally assumed that policy enforcement (at least in its
  initial stages) is likely to concentrate on border nodes between
  autonomous systems.

  Figure 1 illustrates a simple autonomous domain with two boundary
  nodes (A, C) which represent PEPs controlled by PDPs. A core node
  (B) represents an RSVP capable policy ignorant node (PIN) with
  capabilities limited to default policy handling (Section 4.2).


                     PDP1                        PDP2
                      |                           |
                      |                           |
                    +---+         +---+         +---+
                    | A +---------+ B +---------+ C |
                    +---+         +---+         +---+
                     PEP2          PIN           PEP2

                   Figure 1: Autonomous Domain scenario

  Here, policy objects transmitted across the domain traverse an
  intermediate PIN node (B) that is allowed to process RSVP message
  but considered non-trusted for handling policy information.

  This document describes processing rules for both PEP as well as PIN
  nodes.



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3  Policy Data Objects

  POLICY_DATA objects are carried by RSVP messages and contain policy
  information. All policy-capable nodes (at any location in the
  network) can generate, modify, or remove policy objects, even when
  senders or receivers do not provide, and may not even be aware of
  policy data objects.

  The exchange of POLICY_DATA objects between policy-capable nodes
  along the data path, supports the generation of consistent end-to-
  end policies. Furthermore, such policies can be successfully
  deployed across multiple administrative domains when border nodes
  manipulate and translate POLICY_DATA objects according to
  established sets of bilateral agreements.

  The following extends section A.13 in [RSVP].

3.1 Base Format

  POLICY_DATA class=14

  o   Type 1 POLICY_DATA object: Class=14, C-Type=1

      +-------------+-------------+-------------+-------------+
      |  Length                   | POLICY_DATA |      1      |
      +---------------------------+-------------+-------------+
      |  Data Offset              | 0 (reserved)              |
      +---------------------------+-------------+-------------+
      |                                                       |
      // Option List                                         //
      |                                                       |
      +-------------------------------------------------------+
      |                                                       |
      // Policy Element List                                 //
      |                                                       |
      +-------------------------------------------------------+

      Data Offset: 16 bits

          The offset in bytes of the data portion (from the first
          byte of the object header).

      Reserved: 16 bits

           Always 0.

      Option List: Variable length

          The list of options and their usage is defined in Section
          3.2.


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  Policy Element List: Variable length

          The contents of policy elements is opaque to RSVP. See more
          details in Section 3.3.

3.2 Options

  This section describes a set of options that may appear in
  POLICY_DATA objects. All policy options appear as RSVP objects but
  their semantic is modified when used as policy data options.

  FILTER_SPEC object (list) or SCOPE object

  These objects describe the set of senders associated with the
  POLICY_DATA object. If none is provided, the policy information is
  assumed to be associated with all the flows of the session. These
  two types of objects are mutually exclusive, and cannot be mixed.

  In Packed FF Resv messages, this FILTER_SPEC option provides
  association between a reserved flow and its POLICY_DATA objects.

  In WF or SE styles, this option preserves the original
  flow/POLICY_DATA association as formed by PDPs, even across RSVP
  capable PINs. Such preservation is required since PIN nodes may
  change the list of reserved flows on a per-hop basis, irrespective
  of legitimate Edge-to-Edge PDP policy considerations.

  Last, the SCOPE object should be used to prevent "policy loops" in a
  manner similar to the one described in [RSVP], Section 3.4. When PIN
  nodes are part of a WF reservation path, the RSVP SCOPE object is
  unable to prevent policy loops and the separate policy SCOPE object
  is required.

  Note: using the SCOPE option may have significant impact on scaling
  and size of POLICY_DATA objects.

  Originating RSVP_HOP

  The RSVP_HOP object identifies the neighbor/peer policy-capable node
  that constructed the policy object. When policy is enforced at
  border nodes, peer policy nodes may be several RSVP hops away from
  each other and the originating RSVP_HOP is the basis for the
  mechanism that allows them to recognize each other and communicate
  safely and directly.

  If no RSVP_HOP object is present, the policy data is implicitly
  assumed to have been constructed by the RSVP_HOP indicated in the
  RSVP message itself (i.e., the neighboring RSVP node is policy-
  capable).



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  Destination RSVP_HOP

  A second RSVP_HOP object may follow the originating RSVP_HOP object.
  This second RSVP_HOP identifies the destination policy node. This is
  used to ensure the POLICY_DATA object is delivered to targeted
  policy nodes. It may be used to emulate unicast delivery in
  multicast Path messages. It may also help prevent using a policy
  object in other parts of the network (replay attack).

  On the receiving side, a policy node should ignore any POLICY_DATA
  that includes a destination RSVP_HOP that doesn't match its own IP
  address.

  INTEGRITY Object

  Figure 1 (Section 2) provides an example where POLICY_DATA objects
  are transmitted between boundary nodes while traversing non-secure
  PIN nodes. In this scenario, the RSVP integrity mechanism becomes
  ineffective since it places policy trust with intermediate PIN nodes
  (which are trusted to perform RSVP signaling but not to perform
  policy decisions or manipulations).

  The INTEGRITY object option inside POLICY_DATA object creates direct
  secure communications between non-neighboring PEPs (and their
  controlling PDPs) without involving PIN nodes.

  This option can be used at the discretion of PDPs, and is computed
  in a manner described in Appendix B.

  Policy Refresh TIME_VALUES (PRT)

  The Policy Refresh TIME_VALUES (PRT) option is used to slow policy
  refresh frequency for policies that have looser timing constraints
  relative to RSVP. If the PRT option is present, policy refreshes can
  be withheld as long as at least one refresh is sent before the
  policy refresh timer expires. A minimal value for PRT is R; lower
  values are assumed to be R (neither error nor warning should be
  triggered).

  To simplify RSVP processing, time values are not based directly on
  the PRT value, but on a Policy Refresh Multiplier N computed as
  N=Floor(PRT/R). Refresh and cleanup rules are derived from [RSVP]
  Section 3.7 assuming the refresh period for PRT POLICY DATA is R'
  computed as R'=N*R.  In effect, both the refresh and the state
  cleanup are slowed by a factor of N).

  The refresh multiplier applies to no-change periodic refreshes only
  (rather than updates). For example, a policy being refreshed at time
  T, T+N, T+2N,... may encounter a route change detected at T+X. In
  this case, the event would force an immediate policy update and
  would reset refresh times to T+X, T+X+N, T+X+2N,...

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  When network nodes restart, RSVP messages between PRT policy
  refreshes may be rejected since they arrive without necessary
  POLICY_DATA objects.  This error situation would clear with the next
  periodic policy refresh or with a policy update triggered by ResvErr
  or PathErr messages.

  This option is especially useful to combine strong (high overhead)
  and weak (low overhead) authentication certificates as policy data.
  In such schemes the weak certificate can support admitting a
  reservation only for a limited time, after which the strong
  certificate is required.

  This approach may reduce the overhead of POLICY_DATA processing.
  Strong certificates could be transmitted less frequently, while weak
  certificates are included in every RSVP refresh.

3.3 Policy Elements

  The content of policy elements is opaque to RSVP; their internal
  format is understood by policy peers e.g. an RSVP Local Decision
  Point (LDP) or a Policy Decision Point (PDP) [RAP]. A registry of
  policy element codepoints and their meaning is maintained by [IANA-
  CONSIDERATIONS] (also see Section 5).

  Policy Elements have the following format:

  +-------------+-------------+-------------+-------------+
  |  Length                   |   P-Type                  |
  +---------------------------+---------------------------+
  |                                                       |
  // Policy information  (Opaque to RSVP)                //
  |                                                       |
  +-------------------------------------------------------+

3.4 Purging Policy State

  Policy state expires in the granularity of Policy Elements
  (POLICY_DATA objects are mere containers and do not expire as such).

  Policy elements expire in the exact manner and time as the RSVP
  state received in the same message (see [RSVP] Section 3.7).  PRT
  controlled state expires N times slower (see Section 3.2).

  Only one policy element of a certain P-Type can be active at any
  given time. Therefore, policy elements are instantaneously replaced
  when another policy element of the same P-Type is received from the
  same PDP (previous or next policy RSVP_HOP). An empty policy element
  of a certain P-Type is used to delete (rather than a replace) all
  policy state of the same P-Type.


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4  Processing Rules

  These sections describe the minimal required policy processing rules
  for RSVP.

4.1 Basic Signaling

  This draft mandates enforcing policy control for Path, Resv,
  PathErr, and ResvErr messages only. PathTear and ResvTear are
  assumed not to require policy control based on two main
  presumptions. First, that Integrity verification [MD5] guarantee
  that the Tear is received from the same node that sent the installed
  reservation, and second, that it is functionally equivalent to that
  node holding-off refreshes for this reservation.

4.2 Default Handling for PIN nodes

  Figure 1 illustrates an example of where policy data objects
  traverse PIN nodes in transit from one PEP to another.

  A PIN node is required at a minimum to forward the received
  POLICY_DATA objects in the appropriate outgoing messages according
  to the following rules:

  o    POLICY_DATA objects are to be forwarded as is, without any
       modifications.

  o    Multicast merging (splitting) nodes:

       In the upstream direction:

          When multiple POLICY_DATA objects arrive from downstream, the
          RSVP node should concatenate all of them (as a list of the
          original POLICY_DATA objects) and forward them with the
          outgoing (upstream) message.

       On the downstream direction:

          When a single incoming POLICY_DATA object arrives from
          upstream, it should be forwarded (copied) to all downstream
          branches of the multicast tree.

  The same rules apply to unrecognized policies (sub-objects) within
  the POLICY_DATA object. However, since this can only occur in a
  policy-capable node, it is the responsibility of the PDP and not
  RSVP.

4.3 Error Signaling

  Policy errors are reported by either ResvErr or PathErr messages
  with a policy failure error code in the ERROR_SPEC object. Policy
  error message must include a POLICY_DATA object; the object contains

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  details of the error type and reason in a P-Type specific format
  (See Section 3.3).

  If a multicast reservation fails due to policy reasons, RSVP should
  not attempt to discover which reservation caused the failure (as it
  would do for Blockade State). Instead, it should attempt to deliver
  the policy ResvErr to ALL downstream hops, and have the PDP (or LDP)
  decide where messages should be sent. This mechanism allows the PDP
  to limit the error distribution by deciding which "culprit" next-
  hops should be informed. It also allows the PDP to prevent further
  distribution of ResvErr or PathErr messages by performing local
  repair (e.g. substituting the failed POLICY_DATA object with a
  different one).

  Error codes are described in Appendix Appendix A.

5  IANA Considerations

  RSVP Policy Elements (P-Types)

  Following the policies outlined in [IANA-CONSIDERATIONS],numbers 0-
  49151 are allocated as standard policy elements by IETF Consensus
  action, numbers in the range 49152-53247 are allocated as vendor
  specific (one per vendor) by First Come First Serve, and numbers
  53248-65535 are reserved for private use and are not assigned by
  IANA.

6  Security Considerations

  This draft describes the use of POLICY_DATA objects to carry policy-
  related information between RSVP nodes. Two security mechanisms can
  be optionally used to ensure the integrity of the carried
  information. The first mechanism relies on RSVP integrity [MD5] to
  provide a chain of trust when all RSVP nodes are policy capable. The
  second mechanism relies on the INTEGRITY object within the
  POLICY_DATA object to guarantee integrity between non-neighboring
  RSVP PEPs (see Sections 2 and 3.2).

















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7  References

  [RAP]  Yavatkar, R., et al., "A Framework for Policy Based Admission
         Control",IETF <draft-ietf-rap-framework-02.txt>, Jan., 1999.

  [COPS] Boyle, J., Cohen, R., Durham, D., Herzog, S., Raja,n R.,
         Sastry, A., "The COPS (Common Open Policy Service) Protocol",
         IETF <draft-ietf-rap-cops-05.txt>, Jan. 1999.

  [COPS-RSVP] Boyle, J., Cohen, R., Durham, D., Herzog, S., Raja,n R.,
         Sastry, A., "COPS Usage for RSVP", IETF <draft-ietf-rap-cops-
         rsvp-04.txt>, Feb. 1999.

  [RSVP] Braden, R. ed., "Resource ReSerVation Protocol (RSVP) -
         Functional Specification.", IETF RFC 2205, Proposed Standard,
         Sep. 1997.

  [MD5]  Baker, F., Lindell B., Talwar, M. "RSVP Cryptographic
         Authentication" Internet-Draft, <draft-ietf-rsvp-md5-08.txt>,
         Feb. 1999.

  [IANA-CONSIDERATIONS]  Alvestrand, H. and T. Narten, "Guidelines for
         Writing an IANA Considerations Section in RFCs", RFC 2434,
         October 1998.


8  Acknowledgments

  This document incorporates inputs from Lou Berger, Bob Braden,
  Deborah Estrin, Roch Guerin, Timothy O'Malley, Dimitrios Pendarakis,
  Raju Rajan, Scott Shenker, Andrew Smith, Raj Yavatkar, and many
  others.


9  Author Information

  Shai Herzog, IPHighway
  Parker Plaza, 16th Floor
  400 Kelby St.
  Fort-Lee, NJ 07024
  (201) 585-0800
  herzog@iphighway.com














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Appendix A : Policy Error Codes

  This Appendix extends the list of error codes described in Appendix
  B of [RSVP].

  Note that Policy Element specific errors are reported as described
  in Section 4.3 and cannot be reported through RSVP (using this
  mechanism). However, this mechanism provides a simple, less secure
  mechanism for reporting generic policy errors. Most likely the two
  would be used in concert such that a generic error code is provided
  by RSVP, while Policy Element specific errors are encapsulated in a
  return POLICY_DATA object (as in Section 4.3).

  ERROR_SPEC class = 6

  Error Code = 02: Policy Control failure

  Error Value: 16 bit

  0 = ERR_INFO    : Information reporting
  1 = ERR_WARN    : Warning
  2 = ERR_UNKNOWN : Reason unknown
  3 = ERR_REJECT  : Generic Policy Rejection
  4 = ERR_EXCEED  : Quota or Accounting violation
  5 = ERR_PREEMPT : Flow was preempted
  6 = ERR_EXPIRED : Previously installed policy expired (not
  refreshed)
  7 = ERR_REPLACED: Previous policy data was replaced & caused
  rejection
  8 = ERR_MERGE   : Policies could not be merged (multicast)
  9 = ERR_PDP     : PDP down or non functioning
  10= ERR_SERVER  : Third Party Server (e.g., Kerberos) unavailable
  11= ERR_PD_SYNTX: POLICY_DATA object has bad syntax
  12= ERR_PD_INTGR: POLICY_DATA object failed Integrity Check
  13= ERR_PE_BAD  : POLICY_ELEMENT object has bad syntax
  14= ERR_PD_MISS : Mandatory PE Missing (Empty PE is in the PD
  object)
  15= ERR_NO_RSC  : PEP Out of resources to handle policies.
  16= ERR_RSVP    : PDP encountered bad RSVP objects or syntax
  17= ERR_SERVICE : Service type was rejected
  18= ERR_STYLE   : Reservation Style was rejected
  19= ERR_FL_SPEC : FlowSpec was rejected (too large)

  Values between 2^15 and 2^16-1 can be used for site and/or vendor
  error values.






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Appendix B : INTEGRITY computation for POLICY_DATA objects

Computation of the INTEGRITY option is based on the rules set forth in
[MD5], with the following modifications:

Section 4.1:

     Rather than computing digest for an RSVP message, a digest is
     computed for a POLICY_DATA object in the following manner:

     (1)  The INTEGRITY object is inserted in the appropriate place in
          the POLICY_DATA object, and its location in the message is
          remembered for later use.

     (2)  The PDP, at its discretion, and based on destination PEP/PDP
          or other criteria, selects an Authentication Key and the hash
          algorithm to be used.

     (3)  A copy of RSVP SESSION object is temporarily appended to the
          end of the PD object (for the computation purposes only,
          without changing the length of the POLICY_DATA object). The
          flags field of the SESSION object is set to 0. This
          concatenation is considered as the message for which a digest
          is to be computed.

     (4)  The rest of the steps in Section 4.1 ((4)..(9)) remain
          unchanged when computed over the concatenated message.

     Note: When the computation is complete, the SESSION object is
     ignored and is not part of the POLICY_DATA object.

Other Provisions:

The processing of a received POLICY_DATA object as well as a challenge-
response INTEGRITY object inside a POLICY_DATA object is performed in
the manner described in [MD5]. This processing is subject to the
modified computation algorithm as described in the beginning of this
appendix (for Section 4.1 of [MD5]).














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