RAP Working Group R. Hess, Ed. Internet Draft Intel Updates: 2205, 2750 S. Herzog Expires December 2001 IPHighway June 2001 RSVP Extensions for Policy Control draft-ietf-rap-new-rsvp-ext-00.txt Status of this Memo This document is an Internet-Draft and is subject to all provisions of Section 10 of RFC2026. 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 working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html The distribution of this memo is unlimited. This memo is filed as , and expires December 31, 2001. Please send comments to the author. Copyright Notice Copyright (C) The Internet Society (2001). All Rights Reserved. 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]. This memo address a security hole in RFC 2750 whereby POLICY_DATA objects are vulnerable to replay attacks. Expires December 2001 [Page 1] Internet Draft RSVP Extensions for Policy Control June 2001 Table of Contents 1. Introduction.................................................... 2 2. A Simple Scenario............................................... 3 3. Policy Data Objects............................................. 3 3.1. Base Format................................................... 4 3.2. Options....................................................... 4 3.2.1. FILTER_SPEC (List).......................................... 5 3.2.2. SCOPE....................................................... 5 3.2.3. Originating RSVP_HOP........................................ 5 3.2.4. Destination RSVP_HOP........................................ 6 3.2.5. INTEGRITY................................................... 6 3.2.6. Policy Refresh TIME_VALUES (PRT)............................ 6 3.3. Policy Elements............................................... 7 3.4. Purging Policy State.......................................... 8 4. Processing Rules................................................ 8 4.1. Basic Signaling............................................... 8 4.2. Default Handling for PIN Nodes................................ 8 4.3. Error Signaling............................................... 9 5. IANA Considerations............................................. 9 6. Security Considerations......................................... 9 7. References......................................................10 8. Acknowledgements................................................11 9. Author Information..............................................11 Appendix A: Policy Error Codes.....................................12 Full Copyright Statement ..........................................13 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. Version 1 of the RSVP functional specification [RSVP] left a placeholder for policy support in the form of a POLICY_DATA object. The current RSVP functional specification [RSVP] describes an 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 (LDP) as described in [RAP]. The term PDP should be assumed to include LDP as well. Expires December 2001 [Page 2] Internet Draft RSVP Extensions for Policy Control June 2001 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 Policy Enforcement Points (PEPs) controlled by PDPs. A core node (B) represents an RSVP capable, policy ignorant node (PIN) with capabilities limited to default policy handling. 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 messages but is considered non-trusted for handling policy information. This document describes processing rules for both PEP and PIN nodes. 3. Policy Data Objects POLICY_DATA objects are carried in RSVP messages and contain policy information. All policy-capable RSVP nodes at any location in the network can generate, modify, or remove policy objects, even when the senders or the 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]. Expires December 2001 [Page 3] Internet Draft RSVP Extensions for Policy Control June 2001 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 // | | +-------------+-------------+-------------+-------------+ Length: 16 bits The total length of the POLICY_DATA object in bytes. Must always be a multiple of 4. Data Offset: 16 bits The offset in bytes of the Policy Element List from the first byte of the object header. Reserved: 16 bits Unused at this time. This field MUST be set to 0. Option List: Variable length The list of options and their usage are defined in Section 3.2. Policy Element List: Variable length The contents of policy elements are opaque to RSVP. Further details are provided in Section 3.3. 3.2. Options This section describes the set of options that may appear in the Option List field of a POLICY_DATA object. All policy options described in this document are RSVP objects (defined in [RSVP, MD5]), but when used as a policy option, their semantics have been modified as described below. Expires December 2001 [Page 4] Internet Draft RSVP Extensions for Policy Control June 2001 3.2.1. FILTER_SPEC (List) The FILTER_SPEC option is defined to be identical to RSVP's FILTER_SPEC object as defined in [RSVP], Section A.9, with the following semantic changes. This option describes the set of senders associated with the POLICY_DATA object. If none is provided and if the SCOPE option is also absent, the policy information is assumed to be associated with all the flows of the RSVP session. This option is mutually exclusive of the SCOPE option; one or the other but not both MAY be included in the Option List of a POLICY_DATA object. In Packed FF Resv messages, the 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 policy ignorant RSVP nodes. Such preservation is required since PINs may change the list of reserved flows on a per-hop basis, irrespective of legitimate edge-to-edge PDP policy considerations. 3.2.2. SCOPE The SCOPE option is defined to be identical to RSVP's SCOPE object as defined in [RSVP], Section A.6, with the following semantic changes. This option also describes the set of senders associated with the POLICY_DATA object. If none is provided and if the FILTER_SPEC option is also absent, the policy information is assumed to be associated with all the flows of the RSVP session. This option is mutually exclusive of the FILTER_SPEC option; one or the other but not both MAY be included in the Option List of a POLICY_DATA object. The SCOPE option 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 found in the RSVP message is insufficient to prevent policy loops; hence, a separate policy SCOPE option is required. Note: Use the SCOPE option may have significant impact on the scaling and the size of POLICY_DATA objects. 3.2.3. Originating RSVP_HOP The Originating RSVP_HOP option is defined to be identical to RSVP's RSVP_HOP object as defined in [RSVP], Section A.2, with the following semantic changes. This option identifies the neighbor/peer policy aware RSVP node that constructed the POLICY_DATA object. When policy is enforced at border nodes, peer policy nodes may be several RSVP hops away from Expires December 2001 [Page 5] Internet Draft RSVP Extensions for Policy Control June 2001 each other. The Originating RSVP_HOP provides the basis for a mechanism that allows policy aware RSVP nodes to communicate directly with each other. If no Originating RSVP_HOP option is present, the policy data is implicitly assumed to have been constructed by the RSVP_HOP indicated in the RSVP message itself and that, furthermore, the said node is policy-capable. 3.2.4. Destination RSVP_HOP The Destination RSVP_HOP option is defined to be identical to RSVP's RSVP_HOP object as defined in [RSVP], Section A.2, with the following semantic changes. This option identifies the destination policy node. This is used to ensure that the POLICY_DATA object is delivered to the targeted policy node. It may be used to emulate unicast delivery in multicast Path messages. The Destination RSVP_HOP option MAY be included in the Option List of a POLICY_DATA object. When it is included, it MUST follow the Originating RSVP_HOP option. If no Originating RSVP_HOP option is present, then the Destination RSVP_HOP option MUST NOT be included. A policy node SHOULD ignore any POLICY_DATA objects it receives that include a Destination RSVP_HOP that doesn't match its own IP address. 3.2.5. INTEGRITY 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 option inside a POLICY_DATA object creates direct and secure communications between non-neighboring PEPs (and their controlling PDPs) without involving PIN nodes. This option can be used at the discretion of PDPs. Its use is described in [POLICY-MD5]. 3.2.6. Policy Refresh TIME_VALUES (PRT) The Policy Refresh TIME_VALUES (PRT) option is defined to be identical to RSVP's TIME_VALUES object as defined in [RSVP], Section A.4., with the following semantic changes. The PRT option is used to slow the policy refresh frequency for policies that have looser timing constraints relative to RSVP. If Expires December 2001 [Page 6] Internet Draft RSVP Extensions for Policy Control June 2001 the PRT option is present, policy refreshes can be withheld provided a minimum of one refresh is sent before the policy refresh timer expires. The minimum value for PRT is R, R defined as the value found in the TIME_VALUES object of a RSVP message. Lower values for PRT 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. The net effect is that the refresh and the state cleanup are slowed by a factor of N. The Policy Refresh Multiplier applies to no-change periodic refreshes only, not to 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+N, T+X+2N, ... When network nodes restart, RSVP messages between PRT policy refreshes may be rejected since they arrive without the 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 when combining 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. a 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) // | | +-------------+-------------+-------------+-------------+ Expires December 2001 [Page 7] Internet Draft RSVP Extensions for Policy Control June 2001 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 replace) all policy state of the same P-Type. 4. Processing Rules These sections describe the minimal required policy processing rules for RSVP. 4.1. Basic Signaling This memo 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] guarantees 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 on 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. Expires December 2001 [Page 8] Internet Draft RSVP Extensions for Policy Control June 2001 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 of 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. A Policy error message must include a POLICY_DATA object; the object contains 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 of the "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 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 memo raises the following security issues. o POLICY_DATA integrity and node authentication Corrupted or spoofed POLICY_DATA objects could lead to theft of service by unauthorized parties or to denial of service caused by locking up network resources. RSVP protects against such Expires December 2001 [Page 9] Internet Draft RSVP Extensions for Policy Control June 2001 attacks with a PEP peer to PEP peer authentication mechanism using an encrypted hash function. The mechanism is supported by INTEGRITY options that may appear in any POLICY_DATA object. These options use a keyed cryptographic digest technique, which assumes that PEP peers share a secret. Although this mechanism is part of the base POLICY_DATA specification, it is described in a companion document [POLICY-MD5]. Widespread use of the POLICY_DATA integrity mechanism will require the availability of the long-sought key management and distribution infrastructure for routers. Until that infrastructure becomes available, manual key management will be required to secure POLICY_DATA integrity. o User authentication Policy control will depend upon positive authentication of the user and/or application responsible for each reservation request. Policy data may therefore include cryptographically protected user certificates. This is described in a companion document [IDENTITY-REP]. Protection against the aforementioned attacks is provided by establishing a chain of trust, using the PEP peer to PEP peer INTEGRITY option described earlier. 7. References [COPS] Boyle, J., Cohen, R., Durham, D., Herzog, S., Raja, R. and Sastry, A., "The COPS (Common Open Policy Service) Protocol", RFC 2748, January 2000. [COPS-RSVP] Boyle, J., Cohen, R., Durham, D., Herzog, S., Raja, R. and Sastry, A., "COPS Usage for RSVP", RFC 2749, January 2000. [IANA-CONSIDERATIONS] Alvestrand, H. and Narten, T., "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 2434, October 1998. [IDENTITY-REP] Hess, R., Ed., Yadav, S., Yavatkar, R., Pabbati, R., Ford, P., Moore, T., Herzog, S., "Identity Representation for RSVP", work in progress, draft-ietf-rap-rsvp-newidentity-02.txt, May 2001. [MD5] Baker, F., Lindell, B. and Talwar, M., "RSVP Cryptographic Authentication", RFC 2747, January 2000. Expires December 2001 [Page 10] Internet Draft RSVP Extensions for Policy Control June 2001 [POLICY-MD5] Hess, R., "Cryptographic Authentication for RSVP POLICY_DATA Objects", work in progress, draft-ietf-rap-auth-policy-data-00.txt, June 2001. [RAP] Yavatkar, R., Pendarakis, D. and Guerin, R., "A Framework for Policy Based Admission Control", RFC 2753, January 2000. [RSVP] Braden, R., Ed., Zhang, L., Berson, S., Herzog, S. and Jamin, S., "Resource ReSerVation Protocol (RSVP) - Functional Specification", RFC 2205, September 1997. 8. Acknowledgements 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. Authors' Information Rodney Hess Intel Corp, BD1 28 Crosby Dr Bedford, MA 01730 EMail: rodney.hess@intel.com Shai Herzog IPHighway, Inc. 55 New York Avenue Framingham, MA 01701 Phone: (508) 620-1141 EMail: herzog@iphighway.com Expires December 2001 [Page 11] Internet Draft RSVP Extensions for Policy Control June 2001 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. Expires December 2001 [Page 12] Internet Draft RSVP Extensions for Policy Control June 2001 Full Copyright Statement Copyright (C) The Internet Society (2001). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. 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