--- 1/draft-ietf-lisp-map-versioning-02.txt 2011-09-14 00:16:47.000000000 +0200 +++ 2/draft-ietf-lisp-map-versioning-03.txt 2011-09-14 00:16:47.000000000 +0200 @@ -1,52 +1,54 @@ Network Working Group L. Iannone Internet-Draft TU Berlin - Deutsche Telekom Intended status: Experimental Laboratories AG -Expires: January 6, 2012 D. Saucez +Expires: March 16, 2012 D. Saucez O. Bonaventure Universite catholique de Louvain - July 5, 2011 + September 13, 2011 LISP Map-Versioning - draft-ietf-lisp-map-versioning-02.txt + draft-ietf-lisp-map-versioning-03.txt Abstract - This document describes the LISP Map-Versioning mechanism, which - provides in-packet information about EID-to-RLOC mappings used to + This document describes the LISP (Locator/ID Separation Protocol) + Map-Versioning mechanism, which provides in-packet information about + Endpoint-ID to Routing Locator (EID-to-RLOC) mappings used to encapsulate LISP data packets. The proposed approach is based on associating a version number to EID-to-RLOC mappings and transport such a version number in the LISP specific header of LISP- encapsulated packets. LISP Map-Versioning is particularly useful to - inform communicating xTRs about modifications of the mappings used to + inform communicating Ingress Tunnel Routers (ITRs) and Egress Tunnel + Routers (ETRs) about modifications of the mappings used to encapsulate packets. The mechanism is transparent to legacy implementations, since in the LISP-specific header and in the Map - Records, bits used for Map-Versioning can be safely ignored by xTRs - that do not support the mechanism. + Records, bits used for Map-Versioning can be safely ignored by ITRs + and ETRs that do not support the mechanism. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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." - This Internet-Draft will expire on January 6, 2012. + This Internet-Draft will expire on March 16, 2012. Copyright Notice Copyright (c) 2011 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents @@ -64,38 +66,38 @@ 4. EID-to-RLOC Map-Version number . . . . . . . . . . . . . . . . 4 4.1. The Null Map-Version . . . . . . . . . . . . . . . . . . . 5 5. Dealing with Map-Version numbers . . . . . . . . . . . . . . . 6 5.1. Handling Destination Map-Version number . . . . . . . . . 7 5.2. Handling Source Map-Version number . . . . . . . . . . . . 8 6. LISP header and Map-Version numbers . . . . . . . . . . . . . 9 7. Map Record and Map-Version . . . . . . . . . . . . . . . . . . 10 8. Benefits and case studies for Map-Versioning . . . . . . . . . 11 8.1. Synchronization of different xTRs . . . . . . . . . . . . 11 8.2. Map-Versioning and unidirectional traffic . . . . . . . . 12 - 8.3. Map-Versioning and interworking . . . . . . . . . . . . . 12 + 8.3. Map-Versioning and interworking . . . . . . . . . . . . . 13 8.3.1. Map-Versioning and Proxy-ITRs . . . . . . . . . . . . 13 - 8.3.2. Map-Versioning and LISP-NAT . . . . . . . . . . . . . 13 - 8.3.3. Map-Versioning and Proxy-ETRs . . . . . . . . . . . . 13 - 8.4. RLOC shutdown/withdraw . . . . . . . . . . . . . . . . . . 14 - 8.5. Map-Version for lightweight LISP implementation . . . . . 14 - 9. Incremental deployment and implementation status . . . . . . . 15 - 10. Security Considerations . . . . . . . . . . . . . . . . . . . 15 + 8.3.2. Map-Versioning and LISP-NAT . . . . . . . . . . . . . 14 + 8.3.3. Map-Versioning and Proxy-ETRs . . . . . . . . . . . . 14 + 8.4. RLOC shutdown/withdraw . . . . . . . . . . . . . . . . . . 15 + 8.5. Map-Version for lightweight LISP implementation . . . . . 15 + 9. Incremental deployment and implementation status . . . . . . . 16 + 10. Security Considerations . . . . . . . . . . . . . . . . . . . 16 10.1. Map-Versioning against traffic disruption . . . . . . . . 16 - 10.2. Map-Versioning against reachability information DoS . . . 16 + 10.2. Map-Versioning against reachability information DoS . . . 17 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 17 - 13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17 - 13.1. Normative References . . . . . . . . . . . . . . . . . . . 17 - 13.2. Informative References . . . . . . . . . . . . . . . . . . 17 + 13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18 + 13.1. Normative References . . . . . . . . . . . . . . . . . . . 18 + 13.2. Informative References . . . . . . . . . . . . . . . . . . 18 Appendix A. Estimation of time before Map-Version wrap-around . . 18 Appendix B. Document Change Log . . . . . . . . . . . . . . . . . 19 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 20 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 21 1. Introduction This document describes the Map-Versioning mechanism used to provide information on changes in the EID-to-RLOC mappings used in the LISP ([I-D.ietf-lisp]) context to perform packet encapsulation. The mechanism is totally transparent to xTRs not supporting such functionality. It is not meant to replace any existing LISP mechanism, but rather to complete them providing new functionalities. The basic mechanism is to associate a Map-Version number to each LISP @@ -126,21 +128,21 @@ This operation is two-fold. On the one hand, it enables the ETR receiving the packet to know if the ITR has the latest version number that any ETR at the destination EID site has provided to the ITR in a Map-Reply. If it is not the case the ETR can send to the ITR a Map- Request containing the updated mapping or soliciting a Map-Request from the ITR (both cases are already defined in [I-D.ietf-lisp]). In this way the ITR can update its cache. On the other hand, it enables an ETR receiving such a packet to know if it has in its EID-to-RLOC Cache the latest mapping for the source EID (in case of bidirectional - traffic). If it is not the case a Map-Request can be send. + traffic). If it is not the case a Map-Request can be sent. 2. Requirements Notation 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 [RFC2119]. 3. Definitions of Terms The present document uses terms already defined in main LISP @@ -236,25 +238,26 @@ The main idea of using Map-Version numbers is that whenever there is a change in the mapping (e.g., adding/removing RLOCs, a change in the weights due to TE policies, or a change in the priorities) or an ISP realizes that one or more of its own RLOCs are not reachable anymore from a local perspective (e.g., through IGP, or policy changes) the ISP updates the mapping also assigning a new Map-Version number. To each mapping, a version number is associated and changes each time the mapping is changed. Note that map-versioning does not introduce - any new problem concerning the coordination of different ETRs of a + new problems concerning the coordination of different ETRs of a domain. Indeed, ETRs belonging to the same LISP site must return for - a specific EID-prefix the same mapping. In principle this is - orthogonal to whether or not map-versioning is used. The ETR's - synchronization problem is out of the scope of this document. + a specific EID-prefix the same mapping, including the same Map- + Version number. In principle this is orthogonal to whether or not + map-versioning is used. The synchronization problem is out of the + scope of this document. In order to announce in a data-driven fashion that the mapping has been updated, Map-Version numbers used to create the outer IP header of the LISP-encapsulated packet are embedded in the LISP-specific header. This means that the header needs to contain two Map-Version numbers: o The Source Map-Version number of the EID-to-RLOC mapping in the EID-to-RLOC Database used to select the source RLOC. @@ -287,59 +290,64 @@ number can be done, where the following cases can arise: 1. The packets arrive with the same Destination Map-Version number stored in the EID-to-RLOC Database. This is the regular case. The ITR sending the packet has in its EID-to-RLOC Cache an up-to- date mapping. No further actions are needed. 2. The packet arrives with a Destination Map-Version number greater (i.e., newer) than the one stored in the EID-to-RLOC Database. Since the ETR is authoritative on the mapping, this means that - someone is not behaving correctly w.r.t. the specifications, thus - the packet carries a not valid version number and SHOULD be - silently dropped. + someone is not behaving correctly with respect to the + specifications, thus the packet carries a not valid version + number and SHOULD be silently dropped. 3. The packets arrive with a Destination Map-Version number smaller (i.e., older) than the one stored in the EID-to-RLOC Database. This means that the ITR sending the packet has an old mapping in its EID-to-RLOC Cache containing stale information. The ITR sending the packet has to be informed that a newer mapping is available. This is done with a Map-Request message sent back to the ITR. The Map-Request will either trigger a Map-Request back - using the SMR bit or it will piggyback the newer mapping. These - are not new mechanisms; how to SMR or piggyback mappings in Map- - Request messages is already described in [I-D.ietf-lisp], while - their security is discussed in [I-D.ietf-lisp-threats]. These - Map-Request messages should be rate limited (rate limitation - policies are also described in [I-D.ietf-lisp]). The feature - introduced by Map-Version numbers is the possibility of blocking - traffic from ITRs not using the latest mapping. Indeed, after a - certain number of retries, if the Destination Map-Version number - in the packets is not updated, the ETR MAY silently drop packets - with a stale Map-Version number. This because either the ITR is - refusing to use the mapping for which the ETR is authoritative or - (worse) it might be some form of attack. + using the Solicit-Map-Request (SMR) bit or it will piggyback the + newer mapping. These are not new mechanisms; how to SMR or + piggyback mappings in Map-Request messages is already described + in [I-D.ietf-lisp], while their security is discussed in + [I-D.ietf-lisp-threats]. These Map-Request messages should be + rate limited (rate limitation policies are also described in + [I-D.ietf-lisp]). The feature introduced by Map-Version numbers + is the possibility of blocking traffic not using the latest + mapping. Indeed, after a certain number of retries, if the + Destination Map-Version number in the packets is not updated, the + ETR MAY drop packets with a stale Map-Version number while + strongly reducing the rate of Map-Request messages. This because + either the ITR is refusing to use the mapping for which the ETR + is authoritative or (worse) it might be some form of attack. + Another case might be that the control-plane is experiencing + transient failures so the Map-Requests cannot reach that ITR. By + keeping sending Map-Requests at very low rate it is possible to + recover from this situation. The rule in the third case MAY be more restrictive. If the mapping has been the same for a period of time as long as the TTL (defined in [I-D.ietf-lisp]) of the previous version of the mapping, all packets arriving with an old Map-Version SHOULD be silently dropped right away without issuing any Map-Request. The reason that allows such action is the fact that if the new mapping with the updated version number has been unchanged for at least the same time as the TTL of the older mapping, all the entries in the caches of ITRs must have expired. Hence, all ITRs sending traffic should have refreshed the mapping according to [I-D.ietf-lisp]. If packets with old Map- Version number are still received, then either someone has not respected the TTL, or it is a form of spoof/attack. In both cases - this is not valid behavior w.r.t. the specifications and the packet - SHOULD be silently dropped. + this is not valid behavior with respect to the specifications and the + packet SHOULD be silently dropped. LISP-encapsulated packets with the V-bit set, when the original mapping in the EID-to-RLOC Database has version number set to the Null Map-Version value, MAY be silently dropped. As explained in Section 4.1, if an EID-to-RLOC mapping has a Null Map-Version, it means that ITRs, using the mapping for encapsulation, MUST NOT use Map-Version number in the LISP-specific header. For LISP-encapsulated packets with the V-bit set, when the original mapping in the EID-to-RLOC Database has version number set to a value @@ -364,46 +372,47 @@ (i.e., newer) than the one stored in the local EID-to-RLOC Cache. This means that ETR has in its cache a mapping that is stale and needs to be updated. A Map-Request SHOULD be sent to get the new mapping for the source EID. This is a normal Map-Request message sent through the mapping system and MUST respect the specifications in [I-D.ietf-lisp], including rate limitation policies. 3. The packet arrives with a Source Map-Version number smaller (i.e., older) than the one stored in the local EID-to-RLOC Cache. - Such a case is not valid w.r.t. the specifications. Indeed, if - the mapping is already present in the EID-to-RLOC Cache, this - means that an explicit Map-Request has been sent and a Map-Reply - has been received from an authoritative source. Assuming that - the mapping system is not corrupted anyhow, the Map-Version in - the EID-to-RLOC Cache is the correct one and the packet MAY be - silently dropped. + Such a case is not valid with respect to the specifications. + Indeed, if the mapping is already present in the EID-to-RLOC + Cache, this means that an explicit Map-Request has been sent and + a Map-Reply has been received from an authoritative source. + Assuming that the mapping system is not corrupted anyhow, the + Map-Version in the EID-to-RLOC Cache is the correct one and the + packet MAY be silently dropped. If the ETR does not have an entry in the EID-to-RLOC Cache for the source EID (e.g., in case of unidirectional traffic) then the Source Map-Version number can be safely ignored. For LISP-encapsulated packets with the V-bit set, if the Source Map- Version number is the Null Map-Version value, it means that the Source Map-Version number MUST be ignored. 6. LISP header and Map-Version numbers In order for the versioning approach to work, the LISP specific header has to carry both Source Map-Version number and Destination Map-Version number. This is done by setting the V-bit in the LISP - specific header. When the V-bit is set the low-order 24-bits of the - first longword (which usually contains the nonce) are used to - transport both source and destination Map-Version numbers. In - particular the first 12 bits are used for Source Map-Version number - and the second 12 bits for the Destination Map-Version number. + specific header as defined in [I-D.ietf-lisp] Section 5.3. When the + V-bit is set the low-order 24-bits of the first longword (which + usually contains the nonce) are used to transport both source and + destination Map-Version numbers. In particular the first 12 bits are + used for Source Map-Version number and the second 12 bits for the + Destination Map-Version number. Hereafter is the example of LISP header carrying version numbers in the case of IPv4-in-IPv4 encapsulation. The same setting can be used for any other case (IPv4-in-IPv6, IPv6-in-IPv4, and IPv6-in-IPv6). 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ / |N|L|E|V|I|flags| Source Map-Version |Destination Map-Version| LISP+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ @@ -608,41 +616,42 @@ | LISP | | non-LISP | | Domain A | | Domain B | | +-------+ +-----------+ | | | | ITR A |------->| Proxy ETR |------->| | | +-------+ +-----------+ | | | | | | +----------+ +-------------+ Figure 4 - A Proxy-ETR does not have any mapping, since it just decapsulate + A Proxy-ETR does not have any mapping, since it just decapsulates packets arriving from LISP site. In this case, the ITR will just put the Null Map-Version value as Destination Map-Version number, while the receiving Proxy-ETR will ignore the field. With this setup the Proxy-ETR is able to check whether or not the mapping has changed. If this is the case the mapping for LISP Domain A on the PETR can be updated using one of the mechanisms defined in [I-D.ietf-lisp] and [I-D.ietf-lisp-interworking]. 8.4. RLOC shutdown/withdraw Map-Versioning can be even used to perform a graceful shutdown or withdraw of a specific RLOC. This is achieved by simply issuing a new mapping, with an updated Map-Version number, where the specific RLOC to be shut down is withdrawn or announced as unreachable (R bit in the Map Record, see [I-D.ietf-lisp]), but without actually turning it off. - Once no more traffic is received by the RLOC, because all sites have - updated the mapping, it can be shut down safely. + Once no more traffic is received by the RLOC, it can be shut down + gracefully, because at least all sites actively using the mapping + have updated it. It should be pointed out that for frequent up/down changes such a mechanism should not be used since this can generate excessive load on the Mapping System. 8.5. Map-Version for lightweight LISP implementation The use of Map-Versioning can help in developing a lightweight implementation of LISP. This comes with the price of not supporting Loc-Status-Bit, which are useful in some contexts. @@ -685,30 +694,31 @@ information is already included in the Map Record. Map-Versioning is currently implemented in OpenLISP [I-D.iannone-openlisp-implementation]. Note that the reference document for LISP implementation and interoperability tests remains [I-D.ietf-lisp]. 10. Security Considerations - Map-Versioning does not introduce any new security issue concerning - both the data-plane and the control-plane. On the contrary, as - described in the following, if Map-Versioning may be used also to - update mappings in case of change in the reachability information - (i.e., instead of the Locator Status Bits) it is possible to reduce - the effects of some DoS or spoofing attacks that can happen in an + Map-Versioning does not introduce any security issue concerning both + the data-plane and the control-plane. On the contrary, as described + in the following, if Map-Versioning may be used also to update + mappings in case of change in the reachability information (i.e., + instead of the Locator Status Bits) it is possible to reduce the + effects of some DoS or spoofing attacks that can happen in an untrusted environment. - A thorough security analysis of LISP is documented in - [I-D.ietf-lisp-threats]. + Robusteness of the Map-Versioning mechanism leverages on a trusted + Mapping Distribution System. A thorough security analysis of LISP is + documented in [I-D.ietf-lisp-threats]. 10.1. Map-Versioning against traffic disruption An attacker can try to disrupt ongoing communications by creating LISP encapsulated packets with wrong Locator Status Bits. If the xTR blindly trusts the Locator Status Bits it will change the encapsulation accordingly, which can result in traffic disruption. This does not happen in the case of Map-Versioning. As described in Section 5, upon a version number change the xTR first issues a Map- @@ -765,47 +775,47 @@ This work has been partially supported by the INFSO-ICT-216372 TRILOGY Project (www.trilogy-project.org). 13. References 13.1. Normative References [I-D.ietf-lisp] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "Locator/ID Separation Protocol (LISP)", - draft-ietf-lisp-14 (work in progress), June 2011. + draft-ietf-lisp-15 (work in progress), July 2011. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. 13.2. Informative References [I-D.iannone-openlisp-implementation] Iannone, L., Saucez, D., and O. Bonaventure, "OpenLISP Implementation Report", draft-iannone-openlisp-implementation-01 (work in progress), July 2008. [I-D.ietf-lisp-alt] Fuller, V., Farinacci, D., Meyer, D., and D. Lewis, "LISP - Alternative Topology (LISP+ALT)", draft-ietf-lisp-alt-07 - (work in progress), June 2011. + Alternative Topology (LISP+ALT)", draft-ietf-lisp-alt-08 + (work in progress), September 2011. [I-D.ietf-lisp-interworking] Lewis, D., Meyer, D., Farinacci, D., and V. Fuller, "Interworking LISP with IPv4 and IPv6", draft-ietf-lisp-interworking-02 (work in progress), June 2011. [I-D.ietf-lisp-ms] Fuller, V. and D. Farinacci, "LISP Map Server", - draft-ietf-lisp-ms-09 (work in progress), June 2011. + draft-ietf-lisp-ms-11 (work in progress), August 2011. [I-D.ietf-lisp-threats] Saucez, D., Iannone, L., and O. Bonaventure, "LISP Threats Analysis", draft-ietf-lisp-threats-00 (work in progress), July 2011. Appendix A. Estimation of time before Map-Version wrap-around The present section proposes an estimation of the wrap-around time for the proposed 12 bits size for the Map-Version number. Using a @@ -839,20 +849,37 @@ | 15 | 22 Days | 9 Hours | | 14 | 11 Days | 4 Hours | | 13 | 5.6 Days | 2.2 Hours | | 12 | 2.8 Days | 1.1 Hours | +---------------+---------------------+----------------------+ Figure 5: Estimation of time before wrap-around Appendix B. Document Change Log + o Version 03 Posted September 2011. + + * Added reference in Section 7 toward the main lisp documents + specifying the section, as requested by Jari Arkko. + + * Fixed all typos and editorial issues pointed out by Jari Arkko. + + * Added clarification in Section 8.4 as requested by Jari Arkko. + + * Extentend all acronyms in the abstract as requested by Jari + Arkko. + + * Clarified silent drop polocy in Section 5.2 as requested by + both Richard Barnes and Jari Arkko. + + * Fixed typos pointed out by Richard Barnes. + o Version 02 Posted July 2011. * Added text in Section 5 about ETR synchronization, as suggested by Alia Atlas. * Modified text in Section 8.5 concerning lightweight LISP implementation, as suggested by Alia Atlas. * Deleted text concerning old versions of [I-D.ietf-lisp-ms] and [I-D.ietf-lisp-alt] in Section 7, as pointed out by Alia Atlas.