--- 1/draft-ietf-lisp-map-versioning-00.txt 2011-03-11 12:14:21.000000000 +0100 +++ 2/draft-ietf-lisp-map-versioning-01.txt 2011-03-11 12:14:22.000000000 +0100 @@ -1,21 +1,21 @@ Network Working Group L. Iannone Internet-Draft TU Berlin - Deutsche Telekom Intended status: Experimental Laboratories AG -Expires: April 1, 2011 D. Saucez +Expires: September 12, 2011 D. Saucez O. Bonaventure Universite catholique de Louvain - September 28, 2010 + March 11, 2011 LISP Map-Versioning - draft-ietf-lisp-map-versioning-00.txt + draft-ietf-lisp-map-versioning-01.txt Abstract This document describes the LISP Map-Versioning mechanism, which provides in-packet information about 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 @@ -38,77 +38,80 @@ 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. - This Internet-Draft will expire on April 1, 2011. + This Internet-Draft will expire on September 12, 2011. Copyright Notice - Copyright (c) 2010 IETF Trust and the persons identified as the + 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 carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the BSD License. Table of Contents - 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 2. Requirements Notation . . . . . . . . . . . . . . . . . . . . 4 - 3. Definitions of Terms . . . . . . . . . . . . . . . . . . . . . 4 - 4. EID-to-RLOC Map-Version number . . . . . . . . . . . . . . . . 4 - 4.1. The special Map-Version 0 . . . . . . . . . . . . . . . . 5 - 5. Dealing with Map-Version numbers . . . . . . . . . . . . . . . 5 - 5.1. Handling Destination Map-Version number . . . . . . . . . 6 - 5.2. Handling Source Map-Version number . . . . . . . . . . . . 7 - 6. LISP header and Map-Version numbers . . . . . . . . . . . . . 8 - 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 + 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 + 2. Requirements Notation . . . . . . . . . . . . . . . . . . . . 5 + 3. Definitions of Terms . . . . . . . . . . . . . . . . . . . . . 5 + 4. EID-to-RLOC Map-Version number . . . . . . . . . . . . . . . . 5 + 4.1. The Null Map-Version . . . . . . . . . . . . . . . . . . . 6 + 5. Dealing with Map-Version numbers . . . . . . . . . . . . . . . 7 + 5.1. Handling Destination Map-Version number . . . . . . . . . 7 + 5.2. Handling Source Map-Version number . . . . . . . . . . . . 9 + 6. LISP header and Map-Version numbers . . . . . . . . . . . . . 10 + 7. Map Record and Map-Version . . . . . . . . . . . . . . . . . . 11 + 8. Benefits and case studies for Map-Versioning . . . . . . . . . 12 + 8.1. Synchronization of different xTRs . . . . . . . . . . . . 12 + 8.2. Map-Versioning and unidirectional traffic . . . . . . . . 13 8.3. Map-Versioning and interworking . . . . . . . . . . . . . 13 - 8.4. Graceful RLOC shutdown/withdraw . . . . . . . . . . . . . 13 - 8.5. Map-Version for lightweight LISP implementation . . . . . 13 - 9. Incremental deployment and implementation status . . . . . . . 14 - 10. Security Considerations . . . . . . . . . . . . . . . . . . . 14 - 10.1. Map-Versioning against traffic disruption . . . . . . . . 14 - 10.2. Map-Versioning against reachability information DoS . . . 15 - 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 - 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 15 - 13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16 - 13.1. Normative References . . . . . . . . . . . . . . . . . . . 16 - 13.2. Informative References . . . . . . . . . . . . . . . . . . 16 - Appendix A. Estimation of time before Map-Version wrap-around . . 17 - Appendix B. Document Change Log . . . . . . . . . . . . . . . . . 17 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18 + 8.3.1. Map-Versioning and Proxy-ITRs . . . . . . . . . . . . 14 + 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 . . . . . . . . 17 + 10.2. Map-Versioning against reachability information DoS . . . 17 + 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18 + 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 18 + 13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18 + 13.1. Normative References . . . . . . . . . . . . . . . . . . . 18 + 13.2. Informative References . . . . . . . . . . . . . . . . . . 18 + Appendix A. Estimation of time before Map-Version wrap-around . . 19 + Appendix B. Document Change Log . . . . . . . . . . . . . . . . . 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 a + 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 Map-Version numbers to each LISP + The basic mechanism is to associate a Map-Version number to each LISP EID-to-RLOC mapping and transport such a version number in the LISP- specific header. When a mapping changes, a new version number is assigned to the updated mapping. A change in an EID-to-RLOC mapping can be a change in the RLOCs set, by adding or removing one or more RLOCs, but it can also be a change in the priority or weight of one or more RLOCs. When Map-Versioning is used, LISP-encapsulated data packets contain the version number of the two mappings used to select the RLOCs in the outer header (i.e., both source and destination). These version @@ -120,53 +123,57 @@ When an ITR encapsulates a data packet, with a LISP header containing the Map-Version numbers, it puts in the LISP-specific header two version numbers: 1. The version number assigned to the mapping (contained in the EID- to-RLOC Database) used to select the source RLOC. 2. The version number assigned to the mapping (contained in the EID- to-RLOC Cache) used to select the destination RLOC. - This operation is two-fold. On the one hand it enables the ETR - receiving the packet to know if the ITR that sent it is using the - latest mapping for the destination EID. If it is not the case the - ETR can send to the ITR a Map-Request containing the updated mapping - or invoking 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 xTR receiving such a packet - to know if it has in its 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. + 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. 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 + specification [I-D.ietf-lisp]. Hereafter are defined only the terms + that are specific to the Map-Versioning mechanism. + Map-Version number: An unsigned 12-bits assigned to an EID-to-RLOC mapping, not including the value 0 (0x000). - Map-Version 0: The 12-bits value 0 (0x000) is not used as Map- - Version number. It is used to signal that no Map-Version number - is assigned to the EID-to-RLOC mapping. + Null Map-Version: The 12-bits null value of 0 (0x000) is not used as + Map-Version number. It is used to signal that no Map-Version + number is assigned to the EID-to-RLOC mapping. Source Map-Version number: Map-Version number of the EID-to-RLOC mapping used to select the source address (RLOC) of the outer IP - header. + header of LISP-encapsulated packets. Destination Map-Version number: Map-Version number of the EID-to- RLOC mapping used to select the destination address (RLOC) of the - outer IP header. + outer IP header of LISP-encapsulated packets. 4. EID-to-RLOC Map-Version number The EID-to-RLOC Map-Version number consists in an unsigned 12-bits integer. The version number is assigned in a per-mapping fashion, meaning that different mappings will have assigned a different version number, which is also updated independently. An update in the version number (i.e., a newer version) consist in incrementing by one the older version number. Appendix A contains a rough estimation of the wrap-around time for the Map-Version number. @@ -182,39 +189,56 @@ V1 < V2 : True if and only if V1 < V2 < (V1 + 2**(N-1)). V1 > V2 : True if and only if V1 > V2 > (V1 - 2**(N-1)). Using 12 bits, as defined in this document, and assuming a Map- Version value of 69, Map-Version numbers in the range [70; 69 + 2047] are greater than 69, while Map-Version numbers in the range [69 + 2048; (69 + 4095) mod 4096] are smaller than 69. - The initial Map-Version number of a new EID-to-RLOC mapping can be - randomly generated. However, it MUST NOT be zero (0x000) because it - has a special meaning (see Section 4.1). + The initial Map-Version number of a new EID-to-RLOC mapping SHOULD be + randomly generated. However, it MUST NOT be set to the Null Map- + Version value (0x000), because it has a special meaning (see + Section 4.1). -4.1. The special Map-Version 0 +4.1. The Null Map-Version The value 0x000 (zero) is not a valid Map-Version number indicating - the version of the EID-to-RLOC mapping. The only valid use of Map- - Version number equal to 0 is in the Map Records, which are part of - the Map-Request and Map-Reply messages (defined in [I-D.ietf-lisp]). - Map Records that have Map-Version number equal 0 indicate that there - is no Map-Version number associated with the mapping. This means - that LISP encapsulated packets, destined to the EID-Prefix the Map - Record refers to, MUST never contain Map-Version number (i.e., V bit - MUST always be 0). In other words, Map-Version number equal to 0 - signals to the ITR using the mapping that the Map-Versioning is not - supported, or even if supported it MUST NOT be used for that specific - EID-Prefix. Any value different from zero means that Map-Versioning - is supported and MAY be used. + the version of the EID-to-RLOC mapping. Such a value is used for + special purposes and is named the Null Map-Version number. + + The Null Map-Version MAY appear in the LISP specific header as either + Source Map-Version number (cf. Section 5.2) or Destination Map- + Version number (cf. Section 5.1). When the Source Map-Version number + is set to the Null Map-version value it means that no map version + information is conveyed for the source site. This means that if a + mapping exists for the source EID in the EID-to-RLOC Cache, then the + ETR MUST NOT compare the received Null Map-Version with the content + of the EID-to-RLOC cache. When the Destination Map-version number is + set to the Null Map-version value it means that no map version + information is conveyed for the destination site. This means that + the ETR MUST NOT compare the value with the Map-Version number of the + mapping for the destination EID present in the EID-to-RLOC Database. + + The other use of the Null Map-Version number is in the Map Records, + which are part of the Map-Request, Map-Reply and Map-Register + messages (defined in [I-D.ietf-lisp]). Map Records that have a Null + Map-Version number indicate that there is no Map-Version number + associated with the mapping. This means that LISP encapsulated + packets, destined to the EID-Prefix the Map Record refers to, MUST + NOT contain Map-Version numbers (i.e., V bit MUST always be 0). In + other words, the Null Map-Version number signals to the ITR using the + mapping that the Map-Versioning is not supported, or even if + supported it MUST NOT be used for that specific EID-Prefix. Any + value different from zero means that Map-Versioning is supported and + MAY be used. The fact that the 0 value has a special meaning for the Map-Version number implies that, when updating a Map-Version number because of a change in the mapping, if the next value is 0 then Map-Version number MUST be incremented by 2 (i.e., set to 1, which is the next valid value). 5. Dealing with Map-Version numbers The main idea of using Map-Version numbers is that whenever there is @@ -223,233 +247,202 @@ 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. 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 A first one from the EID-to-RLOC mapping in the EID-to-RLOC - Database used to select the source RLOC, and called Source Map- - Version number. + o The Source Map-Version number of the EID-to-RLOC mapping in the + EID-to-RLOC Database used to select the source RLOC. - o A second one from the EID-to-RLOC mapping in the EID-to-RLOC Cache - used to select the destination RLOC, and called Destination Map- - Version number. + o The Destination Map-Version number of the EID-to-RLOC mapping in + the EID-to-RLOC Cache used to select the destination RLOC. By embedding both Source Map-Version number and Destination Map- - Version number an xTR receiving a LISP packet with Map-Version - number, can perform the following checks: + Version number an ETR receiving a LISP packet with Map-Version + numbers, can perform the following checks: 1. The ITR that has sent the packet has an up-to-date mapping in its cache for the destination EID and is performing encapsulation correctly. - 2. In case of bidirectional traffic, the mapping in the local xTR - cache for the source EID is up-to-date. + 2. In case of bidirectional traffic, the mapping in the local ETR + EID-to-RLOC cache for the source EID is up-to-date. - If one or both of the above conditions do not hold, the xTR can send + If one or both of the above conditions do not hold, the ETR can send a Map-Request either to make the ITR aware that a new mapping is available (see Section 5.1) or to update the mapping in the local cache (see Section 5.2). 5.1. Handling Destination Map-Version number When an ETR receives a packet, the Destination Map-Version number relates to the mapping for the destination EID for which the ETR is a - RLOC. This mapping is part of the ETR LISP Database. Since the ETR - is authoritative for the mapping, it has the correct and up-to-date - Destination Map-Version number. A check on this version number is - done, where the following cases can arise: + RLOC. This mapping is part of the ETR EID-to-RLOC Database. Since + the ETR is authoritative for the mapping, it has the correct and up- + to-date Destination Map-Version number. A check on this version + 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. - Further actions are needed. 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. + 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. 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. Further - actions are needed. The ITR sending the packet must 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.saucez-lisp-security]. These Map-Request messages should - be rate limited (rate limitation policies are also described in - [I-D.ietf-lisp]). The gain introduced by Map-Version Numbers is - that after a certain number of retries, if the Destination Map- - Version number in the packets is not updated, packet MAY be - silently dropped because either the ITR is refusing to use the - mapping for which the ETR is authoritative or it might be some - form of attack. + 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.saucez-lisp-security]. 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. - Note that the rule in case 3 can be even more restrictive. If the - mapping has been the same for a period of time as long as the TTL - (defined in LISP [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. Indeed, - if the new mapping with the updated version number has been stable - for at least the same time as the TTL of the older mapping, all the - entries in the caches of ITRs must have expired. If packets with old - Map-Version number are still received, the reason is that 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 MAY be silently dropped. + 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. - For LISP-encapsulated packets with the V-bit set, the Destination - Map-Version can never contain the special value 0. Indeed, as - explained in Section 4.1, if an EID-to-RLOC mapping has Map-Version - 0, it means that ITRs, using the mapping for encapsulation, MUST NOT - put Map-Version number in the LISP-specific header. An ETR receiving - a packet with the V-bit set but Destination Map-Version 0 SHOULD - silently drop the packet. + 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 + different from the Null Map-Version value, a Destination Map-Version + number equal to the Null Map-Version value means that the Destination + Map-Version number MUST be ignored. 5.2. Handling Source Map-Version number - When an xTR receives a packet, the Source Map-Version number relates + When an ETR receives a packet, the Source Map-Version number relates to the mapping for the source EID for which the ITR that sent the - packet is authoritative. If the xTR does not have an entry in the - LISP Cache for the source EID, then the Source Map-Version number can - be safely ignored. If the xTR has an entry in its LISP Cache for the - source EID, then a check is performed and the following cases can - arise: + packet is authoritative. If the ETR has an entry in its EID-to-RLOC + Cache for the source EID, then a check can be performed and the + following cases can arise: 1. The packet arrives with the same Source Map-Version number stored - in the LISP Cache. This is the correct regular case. The xTR - has in its cache an up-to-date copy of the mapping. No further - actions are needed. + in the EID-to-RLOC Cache. This is the correct regular case. The + ITR has in its cache an up-to-date copy of the mapping. No + further actions are needed. 2. The packet arrives with a Source Map-Version number greater - (i.e., newer) than the one stored in the local LISP Cache. This - means that xTR has in its cache a mapping that is stale and needs - to be updated. The packet is considered valid but further - actions are needed. In particular a Map-Request must 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 + (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 LISP Cache. Such - a case is not valid w.r.t. the specifications. Indeed, if the - mapping is already present in the LISP 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 LISP Cache - is the correct one; hence the packet is not valid and SHOULD be + (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. - Otherwise, if the xTR does not have an entry in its cache (e.g. - unidirectional traffic) the Source Map-Version can be safely ignored. + 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 special value 0, it means that the Source Map- - Version number MUST be ignored. + 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. 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). - The present document just specifies how to use the low-order 24-bits - of the first longword of the LISP-specific header when the V-bit is - set to 1. All other cases, including the bit fields of the rest of - the LISP-specific header and the whole LISP packet format are - specified in [I-D.ietf-lisp]. In the following example we include - all the headers of a LISP encapsulated packet just for the sake of - clarity. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - /|Version| IHL |Type of Service| Total Length | - / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - / | Identification |Flags| Fragment Offset | - / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - OH | Time to Live | Protocol = 17 | Header Checksum | - \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - \ | Source Routing Locator | - \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - \| Destination Routing Locator | - +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - / | Source Port = xxxx | Dest Port = 4341 | - UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - \ | UDP Length | UDP Checksum | - +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ / |N|L|E|V|I|flags| Source Map-Version |Destination Map-Version| LISP+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ \ | Instance ID/Locator Status Bits | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - /|Version| IHL |Type of Service| Total Length | - / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - / | Identification |Flags| Fragment Offset | - / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - IH | Time to Live | Protocol | Header Checksum | - \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - \ | Source EID | - \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - \| Destination EID | - +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - - V (1 bit): this is the Map-Version bit as defined in - [I-D.ietf-lisp]. When this bit is set to 1 the low-order 24-bits - of the first longword of the LISP header contain Map-Version - numbers. Source Map-Version number (12 bits): Map-Version of the mapping used by the ITR to select the RLOC present in the "Source Routing - Locator" field. Note that the mapping used for such a selection - is determined by the Source EID through a search in the LISP - Database of the ITR. + Locator" field. How to set on transmission and handle on + reception this value is described in Section 5.2. Destination Map-Version number (12 bits): Map-Version of the mapping used by the ITR to select the RLOC present in the "Destination - Routing Locator" field. Note that the mapping used for such a - selection is determined by the Destination EID, used as lookup key - in the LISP Cache of the ITR. + Routing Locator" field. How to set on transmission and handle on + reception this value is described in Section 5.1. - Not all of the LISP encapsulated packets need to carry version - numbers. When Map-Version numbers are carried the V-bit MUST be set - to 1. All legal combination of the flags, when the V-bit is set to - 1, are described in [I-D.ietf-lisp]. As a recall and in summary, - Map-Version cannot be used with the Echo-Nonce feature (E = 1) and - the Nonce feature (N = 1), since they use the same bitfield. + The present document just specifies how to use the low-order 24-bits + of the first longword of the LISP-specific header when the V-bit is + set to 1. All other cases, including the bit fields of the rest of + the LISP-specific header and the whole LISP packet format are + specified in [I-D.ietf-lisp]. Not all of the LISP encapsulated + packets need to carry version numbers. When Map-Version numbers are + carried the V-bit MUST be set to 1. All legal combinations of the + flags, when the V-bit is set to 1, are described in [I-D.ietf-lisp]. 7. Map Record and Map-Version To accommodate the proposed mechanism, the Map Records that are - transported on Map-Request/Map-Reply messages need to carry the Map- - Version number as well. For this purpose the 12-bits before the EID- - AFI field in the Record that describe a mapping is used. This is - defined in [I-D.ietf-lisp] and reported here as example. + transported on Map-Request/Map-Reply/Map-Register messages need to + carry the Map-Version number as well. For this purpose the 12-bits + before the EID-AFI field in the Record that describe a mapping is + used. This is defined in [I-D.ietf-lisp] and reported here as + example. 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 +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | Record TTL | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ R | Locator Count | EID mask-len | ACT |A| Reserved | e +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ c | Rsvd | Map-Version Number | EID-AFI | o +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ @@ -487,47 +480,50 @@ Map-Versioning does not require additional synchronization mechanism compared to the normal functioning of LISP without Map-Versioning. Clearly all the ETRs have to reply with the same Map-Version number, otherwise there can be an inconsistency that creates additional control traffic, instabilities, traffic disruptions. It is the same without Map-Versioning, with ETRs that have to reply with the same mapping, otherwise the same problems can arise. As an example, let's consider the topology of Figure 1 where ITR A.1 - of domain A is sending unidirectional traffic to the xTR B of domain - B, while xTR A.2 of domain A and xTR B of domain B exchange - bidirectional traffic. + of domain A is sending unidirectional traffic to the domain B, while + A.2 of domain A exchange bidirectional traffic with domain B. In + particular, ITR A.2 send traffic to ETR B and ETR A.2 receives + traffic from ITR B. +-----------------+ +-----------------+ | Domain A | | Domain B | | +---------+ | | - | | xTR A.1 |--- | | + | | ITR A.1 |--- | | | +---------+ \ +---------+ | - | | -------->| xTR B | | - | | -------->| | | - | +---------+ / +---------+ | - | | xTR A.2 |<-- | | + | | ------->| ETR B | | + | | ------->| | | + | +---------+ / | | | + | | ITR A.2 |--- -----| ITR B | | + | | | / +---------+ | + | | ETR A.2 |<----- | | | +---------+ | | | | | | +-----------------+ +-----------------+ Figure 1 - Obviously in the case of Map-Versioning both xTRs of domain A must - use the same value otherwise the xTR of domain B will start to send - Map-Requests. + Obviously in the case of Map-Versioning both ITR A.1 and ITR A.2 of + domain A must use the same value otherwise the ETR of domain B will + start to send Map-Requests. The same problem can, however, arise without Map-Versioning. For - instance if the two xTRs of domain A send different Loc Status Bits. - In this case either the traffic is disrupted, if the xTR B trusts the - Locator Status Bits, or if xTR B does not trusts the Locator Status + instance, if the two ITRs of domain A send different Loc Status Bits. + In this case either the traffic is disrupted, if the ETR B trusts the + Locator Status Bits, or if ETR B does not trusts the Locator Status Bits it will start sending Map-Requests to confirm the each change in the reachability. So far, LISP does not provide any specific synchronization mechanism, but assumes that synchronization is provided by configuring the different xTRs consistently. The same applies for Map-Versioning. If in the future any synchronization mechanism is provided, Map- Versioning will take advantage of it automatically since it is included in the Record format, as described in Section 7. @@ -554,44 +550,108 @@ destination version number in the LISP header since the Source Map- Version number is in ITR's database, while the Destination Map- Version number is in ITR's cache. For what concerns the ETR, it simply checks only the Destination Map- Version number in the same way as described in Section 5, ignoring the Source Map-Version number. 8.3. Map-Versioning and interworking - Map-Versioning works in the context of interworking between LISP and - IPv4 and IPv6 ([I-D.ietf-lisp-interworking]) in the following way. + Map-Versioning is compatible with the LISP interworking between LISP + and non-LISP sites as defined in [I-D.ietf-lisp-interworking]. LISP + interworking defines three techniques to make LISP sites and non-LISP + sites, namely Proxy-ITR, LISP-NAT, and Proxy-ETR. Hereafter it is + described how Map-Versioning relates to these three mechanisms. - The case of proxy-ITR encapsulating packet for LISP sites is - basically the same as the unidirectional traffic case presented in - the previous section. The same rules can be applied. The only - difference that arises is the fact that a proxy-ITR does not have any - mapping, since it just encapsulate packets arriving from non-LISP - site, thus it has no Source Map-Version. In this case, the proxy-ITR - will just put the special value 0 (zero) as Source Map-Version +8.3.1. Map-Versioning and Proxy-ITRs + + The purpose of the Proxy-ITR (PITR) is to encapsulate traffic + originating in a non-LISP site in order to deliver the packet to one + of the ETRs of the LISP site (cf. Figure 3). This case is very + similar to the unidirectional traffic case described in Section 8.2, + hence similar rules apply. + + +----------+ +-------------+ + | LISP | | non-LISP | + | Domain A | | Domain B | + | +-------+ +-----------+ | | + | | ETR A |<-------| Proxy ITR |<-------| | + | +-------+ +-----------+ | | + | | | | + +----------+ +-------------+ + + Figure 3 + + The main difference is that a Proxy-ITR does not have any mapping, + since it just encapsulate packets arriving from non-LISP site, thus + cannot provide a Source Map-Version. In this case, the proxy-ITR + will just put the Null Map-Version value as Source Map-Version number, while the receiving ETR will ignore the field. -8.4. Graceful RLOC shutdown/withdraw + With this setup the LISP Domain A is able to check whether or not the + PITR is using the latest mapping. If this is not the case the + mapping for LISP Domain A on the PITR can be updated using one of the + mechanisms defined in [I-D.ietf-lisp] and + [I-D.ietf-lisp-interworking]. + +8.3.2. Map-Versioning and LISP-NAT + + The LISP-NAT mechanism is based on address translation from non- + routable EIDs to routable EIDs and does not involve any form of + encapsulation. As such Map-Versioning does not apply in this case. + +8.3.3. Map-Versioning and Proxy-ETRs + + The purpose of the Proxy-ETR (PETR) is to decapsulate traffic + originating in a LISP site in order to deliver the packet to the non- + LISP site (cf. Figure 4). One of the main reasons of deploy PETRs is + to bypass uRPF (Unicast Reverse Path Forwarding) checks on the + provider edge. + + +----------+ +-------------+ + | 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 + 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. + 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. In the current LISP specifications the set of RLOCs must always be maintained ordered and consistent with the content of the Loc Status Bits (see section 6.5 of [I-D.ietf-lisp]). With Map-Versioning such type of mechanisms can be avoided. When a new RLOC is added to a @@ -651,24 +711,27 @@ 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- Request. The assumption is that the mapping distribution system is sufficiently secure that Map-Request and Map-Reply messages and their content can be trusted. Security issues concerning specific mapping - distribution system are out of the scope of this document. Note also - that in the case of Map-Versioning the attacker should "guess" a - valid version number that triggers a Map-Request, as described in - Section 5, otherwise the packet is simply dropped. + distribution system are out of the scope of this document. In the + case of Map-Versioning the attacker should "guess" a valid version + number that triggers a Map-Request, as described in Section 5, + otherwise the packet is simply dropped. Nevertheless, guessing a + version number that generates a Map-Request is easy, hence it is + important to follow the rate limitations policies described in + [I-D.ietf-lisp] in order to avoid DoS attacks. Note that a similar level of security can be obtained with Loc Status Bits, by simply making mandatory to verify any change through a Map- Request. However, in this case Locator Status Bits loose their meaning, because, it does not matter anymore which specific bits has changed, the xTR will query the mapping system and trust the content of the received Map-Reply. Furthermore there is no way to perform filtering as in the Map-Versioning in order to drop packets that do not carry a valid Map-Version number. In the case of Locator Status Bits, any random change can trigger a Map-Request (unless rate @@ -705,52 +768,52 @@ 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-08 (work in progress), August 2010. + draft-ietf-lisp-10 (work in progress), March 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-04 - (work in progress), April 2010. + Alternative Topology (LISP+ALT)", draft-ietf-lisp-alt-06 + (work in progress), March 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-01 (work in progress), - August 2010. + draft-ietf-lisp-interworking-02 (work in progress), + March 2011. [I-D.ietf-lisp-ms] Fuller, V. and D. Farinacci, "LISP Map Server", - draft-ietf-lisp-ms-05 (work in progress), April 2010. + draft-ietf-lisp-ms-07 (work in progress), March 2011. [I-D.saucez-lisp-security] Saucez, D., Iannone, L., and O. Bonaventure, "LISP - Security Threats", draft-saucez-lisp-security-01 (work in - progress), July 2010. + Security Threats", draft-saucez-lisp-security-03 (work in + progress), March 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 granularity of seconds and assuming as worst-case that a new version is issued each second, it takes slightly more than 1 hour before the version wraps around. Note that the granularity of seconds is in line with the rate limitation policy for Map-Request messages, as proposed in the LISP main specifications ([I-D.ietf-lisp]). @@ -775,34 +838,48 @@ | 32 | 8171 Years | 136 Years | | 30 | 2042 Years | 34 Years | | 24 | 31 Years | 194 Days | | 16 | 45 Days | 18 Hours | | 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 3: Estimation of time before wrap-around + Figure 5: Estimation of time before wrap-around Appendix B. Document Change Log - o Posted September 2010. + o Version 01 Posted March 2011. - o Added Section "Definitions of Terms". + * Changed the wording from "Map-Version number 0" to "Null Map- + Version. - o Editorial polishing of all sections. + * Clarification of the use of the Null Map-Version value as + Source Map-Version Number and Destination Map-Version Number. - o Added clarifications in section "Dealing with Map-Version numbers" - for the case of the special Map-Version number 0. + * Extended the section describing Map-Versioning and LISP + Interworking co-existence. - o Rename of draft-iannone-mapping-versioning-02.txt. + * Reduce packet format description to avoid double definitions + with the main specs. + + o Version 00 Posted September 2010. + + * Added Section "Definitions of Terms". + + * Editorial polishing of all sections. + + * Added clarifications in section "Dealing with Map-Version + numbers" for the case of the special Map-Version number 0. + + * Rename of draft-iannone-mapping-versioning-02.txt. Authors' Addresses Luigi Iannone TU Berlin - Deutsche Telekom Laboratories AG Ernst-Reuter Platz 7 Berlin Germany Email: luigi@net.t-labs.tu-berlin.de