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Versions: 00 01 02 03 04 05 RFC 2750

Internet Draft                                               Shai Herzog
Expiration: Oct. 1998                                          IPHighway
File: draft-ietf-rap-rsvp-ext-00.txt                           Apr. 1998

                   RSVP Extensions for Policy Control


Status of Memo

   This document is an Internet-Draft.  Internet-Drafts are working
   documents of the Internet Engineering Task Force (IETF), its areas,
   and its working groups.  Note that other groups may also distribute
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   To learn the current status of any Internet-Draft, please check the
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   This memo presents a set of extensions for supporting generic policy
   based admission control in RSVP. [Note 1]

   These extensions include the standard format of POLICY_DATA objects,
   a generic RSVP/Policy-Control interface, 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 [COPS].
[Note 1] This memo could be conceived as an extension to the RSVP
functional specifications [RSVPSP].

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Table of Contents

1     Introduction                                                    3

2     Policy Data Object Format                                       3

      2.1   Base Format   ........................................... 4

      2.2   Policy Data Options  .................................... 4

            2.2.1 RSVP Objects as Policy Options  ................... 5

            2.2.2 Other Options  .................................... 5

3     RSVP/Policy Control Interface                                   6

      3.1   Synchronous vs. Asynchronous Policy Control   ........... 6

      3.2   Policy Control Services  ................................ 7

      3.3   PC Success Codes  ....................................... 10

      3.4   RSVP's Policy Actions   ................................. 11

            3.4.1 Pending Results and Asynchronous Notification   ... 11

            3.4.2 Error Signaling   ................................. 11

            3.4.3 Policy Response   ................................. 12

      3.5   Default Handling of Policy Data Objects  ................ 12

4     Acknowledgment                                                  13

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1. Introduction

   RSVP, by its 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.  Historically,
   when RSVP Ver. 1 was developed, the knowledge and understanding of
   policy issues was in its infancy. As a result, Ver. 1 of the RSVP
   Functional Specifications[RSVPSP] left a place holder for policy
   support in the form of POLICY_DATA objects. However, it  deliberately
   refrained from specifying mechanisms, message formats, or providing
   insight into how policy enforcement should be carried out. This
   document is intended to fill in this void.

   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, in one
   atomic operation. The scope of this document is limited to these
   extensions; a discussion of accounting and access control policies
   for resource reservation protocols can be found in [Fwk] and a
   description of a router-server Policy Protocol for these extensions
   can be found in [COPS].

2. Policy Data Object Format

   The following replaces section A.13 in [RSVPSP].

   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 in compliance
   with local policies. [Note 2]

[Note 2] Core nodes can add policy objects to RSVP messages, even when
none was provided by senders or receivers.  Most likely, this would be
based on specific network topology properties (e.g., incoming port ID).

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   2.1 Base Format

      POLICY_DATA class=14

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

           |  Length                   | POLICY_DATA |      1      |
           |  Data Offset              | Flags       | 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).

           Flags: 8 bits

                0x01  PCF_Updt
                      A modified object, don't check against previous one
                0x02  PCF_Fragment
                      This is a fragment of a PD object

           Reserved: 8 bits

                Always 0.

           Option List

                The list of options and their usage is defined in
                Section 2.2.

           Policy Element List

                The contents of policy elements is opaque to RSVP and
                its internal format is only known to the Local Policy
                Module (LPM). (See Section 3).

                Policy Elements have the following format:

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

   2.2 Policy Data Options

      This section describes a set of options that may appear as options
      in POLICY_DATA objects. All policy options appear as RSVP objects;
      some use their valid original format while others appear as NULL

      2.2.1 RSVP Objects as Policy Options

         The following objects retain the same format specified in
         [RSVPSP] however, they gain different semantics when used
         inside POLICY_DATA objects.

         FILTER_SPEC object (list)

              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.

         RSVP_HOP Object(s)

              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.

              If an RSVP_HOP object follows either an INTEGRITY or
              RSVP_HOP objects it identifies the destination policy
              node. [Note 3]

              If a destination RSVP_HOP and the address of the receiving
              node do not match, the entire POLICY_DATA object is
[Note 3] This RSVP_HOP may be used to ensure the POLICY_DATA object is
delivered to the targeted policy node.  It may be used to emulate
unicast delivery in multicast Path messages.  It also helps prevent
using a policy object in other parts of the network (replay attack).

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         INTEGRITY Object

              The INTEGRITY object provides guarantees that the object
              was not compromised. It follows the rules from [MD5],
              and is calculated over the SESSION object, POLICY_DATA
              object, and the message type field [Note 4]
               as if they formed one continuous in-order message,
              without any alignment.  This concatenation is designed to
              prevent copy and replay attacks of POLICY_DATA objects
              from other sessions, flows, message types or even other
              network locations.

              The RSVP_HOP and INTEGRITY options are mutually exclusive
              since the INTEGRITY object already contains the sending-
              system address.  If neither 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).

      2.2.2 Other Options

         All options that do not use a valid RSVP object format, should
         use the NULL RSVP object format with different CType values.
         This document defines only one such option, however, several
         other may be considered in future versions.  (e.g.,
         Fragmentation, NoChange, etc.).

         o    Policy Refresh Multiplier

              Some policies may have looser timing constraints than
              RSVP, and therefore may allow for lower refresh frequency.
              If the Policy Refresh Multiplier option is present, policy
              is refreshed only once in "Multiplier" RSVP refreshes, for
              "Duplicates" times.

              |             8             |    0        |     1       |
              | Multiplier  | Duplicates  | Reserve (0)               |

[Note 4] As it appears in RSVP's common header.

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              For example, for "Multiplier=16" and "Duplicates=3", the
              policy should be refreshed on RSVP's refreshes number

3. RSVP/Policy Control Interface

   Conceptually, this section belong to Section 3.10.3 titled
   "RSVP/Policy Control Interface" of the RSVP functional

   Policy control in RSVP is modeled as a set of functions which are
   provided by a separate component known as Local Policy Module.  The
   LPM controls the use of POLICY_DATA objects and provides
   authorization information to RSVP.

   3.1 Synchronous vs. Asynchronous Policy Control

      RSVP must routinely consult the LPM for policy decisions.  The
      consultation can follow one of two models: Synchronous or
      Asynchronous. In the Synchronous model, when RSVP calls a
      particular service, it must block until the call is completed.
      (even if it takes substantial time). In the Asynchronous model,
      the call never blocks; delayed results are communicated back to
      RSVP through an upcall.  The asynchronous model is harder to
      support, since RSVP must be able to halt incomplete tasks, save
      their context, and complete them later, when results become
      available, however, it has significantly better scaling

      Query results may be commonly delayed when policy decisions are
      performed by an external server (See [COPS]).  Consider a case
      where an average query takes 10ms; a synchronous RSVP/policy
      implementation would be roughly limited to less than 100 unicast
      flows and even much less for multicast flows.

      Since the two models provide the same functionality, and differ
      only in performance; each RSVP implementation is free to select
      the model best fitting its needs. RSVP may choose the synchronous
      model by specifying a NULL as a cdp parameter when calling a

   3.2 Policy Control Services

      o    Common Parameters

           The following is a list of common parameters (shared by
           several policy control functions.

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           session,  filter_spec_list and shr_ind

                The set of flows to which the POLICY_DATA object
                applies, and an indication whether they are shared.


                The peer policy node, as well as the local LIH
                connecting to it. The (rsvp_hop includes the local


                The direction and type of message that carried the
                POLICY_DATA object.

           resv_handle and  resv_flowspec

                Information regarding the current/desired level of
                reservation and traffic characteristics.

           cbp and  giveup_time

                A pointer (address) of the Control Block. RSVP provides
                this address when making service calls. This value is
                echoed back to RSVP with the completion notification
                upcall.  Giveup_time is the maximal period RSVP is
                willing to wait; If results are still unavailable after
                this period, RSVP should receive an upcall with failure
                results (and timer-expired error).

      o    Call: PC_InPolicy   (message_type, rsvp_hop, session,
                                shr_ind, filter_spec_list,
                                cbp, giveup_time)
                                -> RCode

           RSVP calls PC_InPolicy for all incoming messages; However, it
           is acceptable for implementations to turn off policy
           processing for messages other than Path and Resv, when they
           don't carry any POLICY_DATA objects. [Note 5]
[Note 5] It is highly desirable to authorize Tear and Error messages
even when they don't carry policy objects.  However, since the risk from

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           The LPM verifies any incoming policy objects (if included)
           and provides an authorization decision. [Note 6]

           If the incoming message is authorized, RSVP continues its
           normal processing. If it is rejected, RSVP drops the message
           entirely (as if it was never received), and sends the
           appropriate error message (with a policy failure error code).
           With RSVP's soft-state management, the consequences of
           dropping the incoming message is that the existing state
           (Path or Resv) begins to age and would eventually time-out.
           [Note 7]

           Reservations may also be authorized with a warning which
           marks them as preemptable.  A preemptable reservation may be
           canceled at any time by admission control to make room for
           another more important reservation.  (See "TC_Preempt()" and
           the discussion of service preemption in [RSVPSP].)

           Parameter refresh-period has the same value and semantics as
           in RSVP.

      o    Call: PC_OutPolicy  (message_type, rsvp_hop_list, session,
                                shr_ind, filter_spec_list,
                                max_pd, avail_pd,
                                cbp, giveup_time,
                                -> RCode

           Before RSVP finalizes an any outgoing RSVP message it calls
           PC_OutPolicy() to prepare outgoing objects for the a
           specified flow.  RSVP specifies the desired maximal object
           size ("max_pd"), and the available space within the current
           RSVP control message ("avail_pd"). [Note 8]
relaxed authorization is limited to denial of service for a single flow,
the decision is left at the discretion of local administrators.

[Note 6] To prevent code duplication, PC_AuthCheck() may be called

[Note 7] An incoming messages may fail authorization simply because it
lacks a particular policy object which was lost in transit.  This
approach is consistent with RSVP's state management rules.

[Note 8] "avail_pd" must be at least the size of a POLICY_DATA object
without a data portion or the call would fail.

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            The filter_spec_list includes the set of filters
           corresponding to the reserved sources.

           When the filter_spec_list includes multiple filters (either
           because of a shared reservation or an aggregated policy over
           multiple FF) individual outgoing hops may be associated with
           different sets of filter_specs.  RSVP must build the
           filter_spec_list as a union of all filter_spec lists over all
           outgoing hops. (All reserved sources) The LPM computes
           individual per-hop filter_spec lists as the intersection of
           this list with the set of sources upstream to a specific
           previous hop.  (Previous-hop information is obtained from
           incoming Path messages.)  A NULL filter_spec_list represents
           "all" sources (i.e., WF).

           The call returns a list of outgoing POLICY_DATA objects for
           each rsvp_hop.

      o    Call: PC_AuthCheck  (message_type, session,
                                shr_ind, filter_spec_list,
                                resv_desc list,
                                cbp, giveup_time)
                                -> RCode

           Parameter resv_desc provides a list of reservation
           descriptions.  This description is made of three components:
           lih, resv_handle, and  resv_flowspec.

           In the upstream direction (e.g., Resv) authorization may need
           to be checked on multiple LIHs (all reservations for a flow).
           In such cases, status queries can be perform separately for
           each LIH, once for all LIHs, or anything in between.
           full_list_indication must be set at the last of
           PC_AuthCheck() query of the series. [Note 9]

           Authorization can be verified on both the Path and Resv
           directions.  When the message_type is an upstream type (Resv,
           Resv Tear, Path Err) the lih is assumed to be an outgoing
           interface and reservation status is checked. However, when
[Note 9] When policies are interdependent across LIHs (as when the cost
is shared among downstream receivers), full_list_ind notifies the server
that the list of reserved LIH is complete and that it can safely compute
the status of these reservations.

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           the message_type is an downstream type (Path, Path Tear, Resv
           Err), the lih is assumed to be an incoming interface and
           Path-sending authorization is checked.

           Authorization checks are usually triggered by the arrival of
           a new message; these are handled transparently by the input
           processing call PC_InPolicy(). In a synchronous, when an
           upcall mechanism is not supported, RSVP must verify the
           status of reservations before refreshing them.

      o    Call: PC_Init       (K, upcall,... )
                                -> RCode

           This call initializes the LPM and sets specific RSVP/policy
           configuration parameters.  K is the soft-state multiplier for
           refresh-period (see [RSVPSP]) and upcall registers a routine
           that may be called by the LPM to notify RSVP on policy
           changes. (See next item)

      o    Call: upcall        (event_type, cbp, message_type,
                                lih, rsvp_hop list, session,
                                shr_ind, filter_spec_list,

           Event_type determines the original call type (if applicable).
           cbp is an echo of the cbp provided by RSVP when making the
           original call. RSVP may use this pointer to locate the
           original context of the call.

           RCode uses the same values specified in this document, as it
           would for the original calls. Notice that the upcall
           parameters are a superset of the parameters used by all the
           non-blocking PC calls.

      o    Call: PC_DelState   (message_type, rsvp_hop,
                                session, filter_spec_list,
                                -> RCode

           This call affects all the state associated with a particular
           multicast (or unicast) branch. It is used for route changes,
           blockade state other instantaneous state change performed by
           RSVP.  When applicable parameters are NULL, an aggregate of
           the state is affected (across all values of the NULL-ed
           parameter).  For example, PC_DelState(NULL, session, NULL,
           NULL, PC_delete) would purge all the policy state associated
           with "session".

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           Parameter "op_type" is the requested type of state change:

           PC_Delete :        Purge state.
           PC_Block  :        Blockade (ignore) state
           PC_Unblock:        Unblock state.

   3.3 PC Success Codes

      The return code (RCode) provides policy feedback to RSVP, it is
      made of three separate return variables: [Note 10]

      o    Function return value:

           0: Success

                The call was completed successfully.  For PC_AuthCheck()
                and  PC_InPolicy() it also signals the authorization of
                the RSVP operation (e.g., Reservation, Path, Tear, etc.)
                RSVP need not check the PC_flags or PC_errno.

           1: Pending

                The requested results are delayed.  Should these results
                become available or the giveup_time expires, the
                notification upcall would signal RSVP.

           2: Warning

                Same as success except that there is a non-fatal warning
                and RSVP must check the PC_flags for further

           3: Policy failure

                Policy authorization for the RSVP operation has failed.
                RSVP should invoke its standard error reporting
                mechanism (PathErr or ResvErr).

      o    "PC_errno":
[Note 10] This is only an initial list, we expect that part to change as
policy control matures.

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           An external variable (similar to the "errno" in Unix) which
           provides specific error (reason) code.

      o    "PC_flags":

           An external variable with flags that advise RSVP about
           required operations:

           0x01  PC_RC_ModState

                The incoming POLICY_DATA object contains an update.
                RSVP must immediately initiate update forwarding

           0x02  PC_RC_Resp

                RSVP must immediately initiate a message. The type of
                requested message is placed in the PC_errno variable and
                corresponds to message type values in the RSVP common

           0x04  PC_RC_Preempt

                Only for Resv incoming objects. RSVP should inform the
                local admission control that the reservation is of lower
                priority and can be preempted, if necessary.

   3.4 RSVP's Policy Actions

      The PC success codes, and especially "PC_Flags" advise RSVP about
      appropriate required actions. This section describes these actions
      in greater detail.

      3.4.1 Pending Results and Asynchronous Notification

         For various reasons the LPM may need to consult an external
         entity (e.g., server) for partial policy processing.  (For a
         description of a router/server protocol see [COPS]).  For
         efficiency reasons, RSVP must not be forced to wait idly while
         external policy processing takes place.  Instead, A
         configurable option permits calls to PC_AuthCheck() or
         PC_OutPolicy() to terminate with a "pending" return value
         whenever results are delayed (for any reason).

         The following steps take place when RSVP receives a pending
         return value:

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         o    RSVP halts the current operation, saves its state (linked
              to the cbp), and moves to the next task.

         o    Once results are available or the giveup_time expires
              [Note 11]

              the LPM "wakes up" RSVP by calling the notification

         o    The wakeup call provides results, context, and the cbp
              (see Section 3.2).

         o    RSVP resumes the previously halted operation and uses the
              provided context parameters as if they were returned by
              the original (previously pending) call.

      3.4.2 Error Signaling

         Policy errors are reported by either ResvErr or PathErr
         messages with a policy failure error code (specified in
         [RSVPSP]).  Policy error message must include a POLICY_DATA
         object; the object contains details of the error type and
         reason.  If none is provided, the error message should not be

         If a multicast reservation fails, 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.  The LPM would limit the
         error distribution by providing outgoing objects only to
         "culprit" next-hops; if the LPM performs local repair [Note 12]
          it can prevent the further distribution of ResvErr or PathErr

         The LPM should internally implement blockade state style
         mechanism for similar reasons as RSVP (preventing an
         unauthorized reservation from forcing other valid reservations
         to fail).  This document does not define this mechanism and
         assumes it would be policy-implementation specific.

[Note 11] If results are still unavailable at giveup_time, the answer is
assumed to be failure (for AuthCheck) or no output (for OutPolicy).

[Note 12] Local repair can be performed by substituting the failed
POLICY_DATA object with a different one.

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      3.4.3 Policy Response

         The LPM can initiate an immediate outgoing RSVP message (Path,
         Resv, etc.) by setting the flag PC_RC_Response and providing
         the number of the requested RSVP message in the PC_errno
         variable. [Note 13]

         This mechanism is useful when the appropriate RSVP message is
         either scheduled for a significantly later time, or not at all.
         When the PC_RC_Response flag is set, RSVP, should schedule the
         requested outgoing message as if its refresh timer has expired;
         for non-refreshed messages like ResvErr, RSVP should act as if
         they were just received.

         This mechanism allows policies that require an immediate
         confirmation by scheduling a reverse-direction message with a
         confirmation POLICY_DATA object.

   3.5 Default Handling of Policy Data Objects

      It is generally assumed that policy enforcement (at least in its
      initial stages) is likely to concentrate on border nodes between
      autonomous systems. Consequently, policy objects transmitted at
      one edge of an autonomous cloud may traverse intermediate non-
      policy-capable RSVP nodes.  The minimal requirement from a non-
      policy-capable RSVP node is to forward POLICY_DATA objects
      embedded in the appropriate outgoing messages, as-is (without
      modifications) according to the following rules:

      o    POLICY_DATA objects are to be forwarded as is, in the same
           type of RSVP messages in which they arrived.

      o    Multicast merging (splitting) nodes:

           In the upstream direction:

                Applicable incoming POLICY_DATA objects are
                concatenated, and the list is forwarded with the
                upstream message.

           On the downstream direction:

                A copy of all applicable incoming objects is forwarded
[Note 13] The value of the PC_errno corresponds to message type values
in the RSVP common header.

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                with each downstream message.

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

4. Acknowledgment

   This document incorporates inputs from Lou Berger, Bob Braden,
   Deborah Estrin, Roch Guerin, Dimitrios Pendarakis, Raju Rajan, and
   Scott Shenker.  It also reflects feedback from many other RSVP


[MD5]  F. Baker.  RSVP Cryptographic Authentication "Internet-Draft",
    draft-ietf-rsvp-md5-05.txt, Aug. 1997.

[RSVPSP]  R. Braden, L. Zhang, S. Berson, S. Herzog, and S. Jamin,
    Resource ReSerVation Protocol (RSVP) Version 1 Functional
    Specification. RFC 2205, Sep. 1997.

[COPS]  J. Boyle, R Cohen, D. Durham, S. Herzog, R. Rajan, A. Sastry.
    The COPS (Common Open Policy Service) Protocol
    "Internet-Draft", draft-ietf-rap-cops-01.txt, Mar. 1998.

[Fwk]  R. Yavatkar, D. Pendarakis, R. Guerin.
    A Framework for Policy-based Admission Control
    "Internet-Draft", draft-ietf-rap-framework-00.txt, Nov. 1997.

Author's Address

Shai Herzog
2055 Gateway Place, Suite 400
San Jose, CA 95110

Phone: (408) 390-3045
Email: herzog@iphighway.com

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