Network Working Group V. Fuller Internet-Draft D. Farinacci Intended status: Experimental cisco Systems Expires: March 8, 2010 September 4, 2009 LISP Map Server draft-ietf-lisp-ms-02.txt Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. 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. This Internet-Draft will expire on March 8, 2010. Copyright Notice Copyright (c) 2009 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 in effect on the date of publication of this document (http://trustee.ietf.org/license-info). Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Fuller & Farinacci Expires March 8, 2010 [Page 1] Internet-Draft LISP Map Server September 2009 Abstract This draft describes the LISP Map-Server (LISP-MS), a computing system which provides a simple LISP protocol interface as a "front end" to the Endpoint-ID (EID) to Routing Locator (RLOC) mapping database and associated virtual network of LISP protocol elements. The purpose of the Map-Server is to simplify the implementation and operation of LISP Ingress Tunnel Routers (ITRs) and Egress Tunnel Routers (ETRs), the devices that implement the "edge" of the LISP infrastructure and which connect directly to LISP-capable Internet end sites. Table of Contents 1. Requirements Notation . . . . . . . . . . . . . . . . . . . . 3 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Definition of Terms . . . . . . . . . . . . . . . . . . . . . 5 4. Basic Overview . . . . . . . . . . . . . . . . . . . . . . . . 6 5. Interactions With Other LISP Components . . . . . . . . . . . 7 5.1. ITR EID-to-RLOC Mapping Resolution . . . . . . . . . . . . 7 5.2. ETR/Map-Server EID Prefix Registration . . . . . . . . . . 7 5.3. Map-Server Processing . . . . . . . . . . . . . . . . . . 8 5.4. Map-Resolver Processing . . . . . . . . . . . . . . . . . 9 5.4.1. Anycast Map-Resolver Operation . . . . . . . . . . . . 10 6. Security Considerations . . . . . . . . . . . . . . . . . . . 11 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12 7.1. Normative References . . . . . . . . . . . . . . . . . . . 12 7.2. Informative References . . . . . . . . . . . . . . . . . . 12 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 13 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14 Fuller & Farinacci Expires March 8, 2010 [Page 2] Internet-Draft LISP Map Server September 2009 1. 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]. Fuller & Farinacci Expires March 8, 2010 [Page 3] Internet-Draft LISP Map Server September 2009 2. Introduction LISP [LISP] specifies an architecture and mechanism for replacing the addresses currently used by IP with two separate name spaces: EIDs, used within sites, and RLOCs, used on the transit networks that make up the Internet infrastructure. To achieve this separation, LISP defines protocol mechanisms for mapping from EIDs to RLOCs. In addition, LISP assumes the existence of a database to store and propagate those mappings globally. Several such databases have been proposed, among them: LISP-CONS [CONS], LISP-NERD, [NERD] and LISP+ ALT [ALT], with LISP+ALT being the system that is currently being implemented and deployed on the pilot LISP network. There are two types of operation for a LISP Map-Server: as a Map- Resolver, which accepts Map-Requests from an ITR and "resolves" the EID-to-RLOC mapping using the distributed mapping database, and as a Map-Server, which learns authoratative EID-to-RLOC mappings from an ETR and publish them in the database. A single device may implement one or both types of operation. Conceptually, LISP Map-Servers share some of the same basic configuration and maintenance properties as Domain Name System (DNS) [RFC1035] servers and caching resolvers. With this in mind, this specification borrows familiar terminology (resolver and server) from the DNS specifications. Fuller & Farinacci Expires March 8, 2010 [Page 4] Internet-Draft LISP Map Server September 2009 3. Definition of Terms Map-Server: a network infrastructure component which learns EID-to- RLOC mapping entries from an authoratative source (typically, an ETR, though static configuration or another out-of-band mechanism may be used). A Map-Server publishes these mappings in the distributed mapping database. Map-Resolver: a network infrastructure component which accepts LISP Encapsulated Map-Requests, typically from an ITR, quickly determines whether or not the destination IP address is part of the EID namespace; if it is not, a Negative Map-Reply is immediately returned. Otherwise, the Map-Resolver finds the appropriate EID-to-RLOC mapping by consulting the distributed mapping database system. Encapsulated Map-Request: a LISP Map-Request with an additional LISP header prepended. Sent to UDP destination port 4341. The "outer" addresses are globally-routeable IP addresses, also known as RLOCs. Used by an ITR when sending to a Map-Resolver and by a Map-Server when sending to an ETR. Negative Map-Reply: a LISP Map-Reply that contains an empty locator-set. Returned in response to a Map-Request of the destination EID does not exist in the mapping database. Typically, this means that the "EID" being requested is an IP address connected to a non-LISP site. Map-Register message: a LISP message sent by an ETR to a Map-Server to register its associated EID prefixes. In addition to the set of EID prefixes to register, the message includes one or more RLOCs to be be used by the Map-Server when forwarding Map-Requests (re-formatted as Encapsulated Map-Requests) received through the database mapping system. For definitions of other terms, notably Map-Request, Map-Reply, Ingress Tunnel Router (ITR), and Egress Tunnel Router (ETR), please consult the LISP specification [LISP]. Fuller & Farinacci Expires March 8, 2010 [Page 5] Internet-Draft LISP Map Server September 2009 4. Basic Overview A Map-Server is a device which publishes EID-prefix information on behalf of ETRs and connects to the LISP distributed mapping database system to help answer LISP Map-Requests seeking the RLOCs for those EID prefixes. To publish its EID-prefixes, an ETR periodically sends Map-Register messages to the Map-Server. A Map-Register message contains a list of EID-prefixes plus a set of RLOCs that can be used to reach the ETR when a Map-Server needs to forward a Map-Request to it. On the LISP pilot network, which is expected to be a model for deployment of LISP on the Internet, a Map-Server connects to LISP+ALT network and acts as a "last-hop" ALT router. Intermediate ALT routers forward Map-Requests to the Map-Server that advertises a particular EID-prefix and the Map-Server forwards them to the owning ETR, which responds with Map-Reply messages. The LISP Map-Server design also includes the operation of a Map- Resolver, which receives Encapsulated Map-Requests from its client ITRs and uses the distributed mapping database system to find the appropriate ETR to answer those requests. On the pilot network, a Map-Resolver acts as a "first-hop" ALT router. It has GRE tunnels configured to other ALT routers and uses BGP to learn paths to ETRs for different prefixes in the LISP+ALT database. The Map-Resolver uses this path information to forward Map-Requests over the ALT to the correct ETRs. A Map-Resolver may operate in either a non-caching mode, where it simply de-capsulates and forwards the Encapsulated Map-Requests that it receives from ITRs, or in caching mode, where it saves information about those Map-Reqeusts, originates new Map- Requests to the correct ETR, accepts and caches the Map-Replies, and finally forwards the Map-Replies to the original ITRs. Note that a single device can implement the functions of both a Map- Server and a Map-Resolver. As is the case with the DNS, however, operational simplicity argues for keeping those functions separate. Fuller & Farinacci Expires March 8, 2010 [Page 6] Internet-Draft LISP Map Server September 2009 5. Interactions With Other LISP Components 5.1. ITR EID-to-RLOC Mapping Resolution An ITR is configured with the address of a Map-Resolver. This address is a "locator" or RLOC in that it must be routeable on the underlying core network; it must not need to be resolved through LISP EID-to-RLOC mapping as that would introduce a circular dependancy. When using a Map-Resolver, an ITR does not need to connect to any other database mapping system. In particular, the ITR need not connect to the LISP+ALT infrastructure or implement the BGP and GRE protocols that it uses. An ITR sends an Encapsulated Map-Request to a configured Map-Resolver when it needs an EID-to-RLOC mapping that is not found in its local map-cache. Using the Map-Resolver greatly reduces both the complexity of the ITR implementation the costs associated with its operation. In response to an Encapsulated Map-Request, the ITR can expect one of the following: o A negative LISP Map-Reply if the Map-Resolver can determine that the requested EID does not exist. The ITR saves EID prefix returned in the Map-Reply in its cache, marking it as non-LISP- capable and knows not to attempt LISP encapsulation for destinations matching it. o A LISP Map-Reply from the ETR that owns the EID-to-RLOC mapping or possibly from a Map-Server answering on behalf of the ETR. Note that the stateless nature of non-caching Map-Resolver forwarding means that the Map-Reply may not be from the Map-Resolver to which the Encapsulated Map-Request was sent unless the target Map- Resolver offers caching (Section 5.4). Note that an ITR may use a Map-Resolver while also participating in another mapping database mechanism. For example, an ITR that runs LISP+ALT can also send Encapsulated Map-Requests to a Map-Resolver. When doing this, an ITR should prefer querying an ETR learned through the ALT network as LISP+ALT provides better information about the set of define EID prefixes. Such a configuration is expected to be very rare, since there is little benefit to using a Map-Resolver if an ITR is already using a mapping database system. 5.2. ETR/Map-Server EID Prefix Registration An ETR publishes its EID prefixes on a Map-Server by sending LISP Map-Register messages. A Map-Register message is authenticated using Fuller & Farinacci Expires March 8, 2010 [Page 7] Internet-Draft LISP Map Server September 2009 an IPSec Authentication Header (AH) as defined in [RFC2402], with SHA-1 or SHA-256 as the authentication HMAC. Prior to sending a Map- Register message, the ETR and Map-Server must be configured with a secret shared-key. In addition, a Map-Server will typically perform additional verification checks, such as matching any EID-prefix listed in a Map-Register message against a list of prefixes for which the ETR is known to be an authoritative source. Map-Register messages are sent periodically from an ETR to a Map- Server with a suggested interval between messages of one minute. A Map-Server should time-out and remove an ETR's registration if it has not received a valid Map-Register message within the past three minutes. When first contacting a Map-Server after restart or changes to its EID-to-RLOC database mappings, an ETR may initially send Map- Register messages at an increased frequency, up to one every 20 seconds. This "quick registration" period is limited to five minutes in duration. An ETR which uses a Map-Server to publish its EID-to-RLOC mappings does not need to participate further in the mapping database protocol(s). On the pilot network, for example, this means that the ETR does not need to implement GRE or BGP, which greatly simplifies its configuration and reduces its cost of operation. Note that use of a Map-Server does not preclude an ETR from also connecting to the mapping database (i.e. it could also connect to the LISP+ALT network) but doing so doesn't seem particularly useful as the whole purpose of using a Map-Server is to avoid the complexity of the mapping database protocols. 5.3. Map-Server Processing The operation of a Map-Server, once it has EID-prefixes registered by its client ETRs, is quite simple. In response to a Map-Request (received over the ALT on the pilot network), the Map-Server verifies that the destination EID matches an EID-prefix for which it has one or more registered ETRs, then re-encapsulates and forwards the now- Encapsulated Map-Reqeust to a matching ETR. It does not otherwise alter the Map-Request so any Map-Reply sent by the ETR is returned to the RLOC in the Map-Request, not to the Map-Server. Unless also acting as a Map-Resolver, a Map-Server should never receive Map- Replies; any such messages should be discarded without response, perhaps accompanied by logging of a diagnostic message if the rate of Map-Replies is suggestive of malicious traffic. Fuller & Farinacci Expires March 8, 2010 [Page 8] Internet-Draft LISP Map Server September 2009 5.4. Map-Resolver Processing In response to an Encapsulated Map-Request, a Map-Resolver de- capsulates the message then checks its local database of mapping entries (statically configured, cached, or learned from associated ETRs). If it finds a matching entry, it returns a non-authoratative LISP Map-Reply with the known mapping. If the Map-Resolver does not have the mapping entry and if it can determine that the requested IP address does not match an EID-prefix in the mapping database, it immediately returns a negative LISP Map- Reply, one which contains an EID prefix and an empty locator-set. To minimize the number of negative cache entries needed by an ITR, the Map-Resolver should return the least-specific prefix which both matches the original query and does not match any EID-prefix known to exist in the LISP-capable infrastructure. If the Map-Resolver does not have sufficient information to know whether the EID exists, it needs to forward the Map-Request to another device which has more information about the EID being requested. This is done in one of two ways: 1. A non-caching Map-Resolver simply forwards the unencapsulated Map-Request, with the original ITR RLOC as the source, on to the distributed mapping database. On the pilot network, the Map- Resolver is connected to the ALT network and sends the Map- Request to the next ALT hop learned from its ALT BGP neighbors. The Map-Resolver does not send any response to the ITR; since the source RLOC is that of the ITR, the ETR or Map-Server which receives the Map-Request over the ALT and responds will do so directly to the ITR. 2. A caching Map-Resolver queues information from the Encapsulated Map-Request, including the ITR RLOC and the original nonce. It then modifies the Map-Request to use its own RLOC, generates a "local nonce" (which is also saved in the request queue entry), and forwards the Map-Request as above. When the Map-Resolver receives a Map-Reply, it looks in its request queue to match the reply nonce to a "local nonce" entry then de-queues the entry and uses the saved original nonce and ITR RLOC to re-write those fields in the Map-Reply before sending to the ITR. The request queue entry is also deleted and the mapping entries from the Map- Reply are saved in the Map-Resolver's cache. Fuller & Farinacci Expires March 8, 2010 [Page 9] Internet-Draft LISP Map Server September 2009 5.4.1. Anycast Map-Resolver Operation A Map-Resolver can be set up to use "anycast", where where the same address is assigned to multiple Map-Resolvers and is propagated through IGP routing, to facilitate the use of a topologically-close Map-Resolver each ITR. Note that Map-Server associations with ETRs should NOT use anycast addresses as doing so could cause unpredictable forwarding of Map-Requests to the ETRs. Fuller & Farinacci Expires March 8, 2010 [Page 10] Internet-Draft LISP Map Server September 2009 6. Security Considerations Using the 2-way nonce exchange documented in [LISP] can be used to avoid ITR spoofing attacks. To publish an authoratative EID-to-RLOC mapping, an ETR uses the IPsec AH to authenticate itself to a Map-Server. A pair-wise shared key is used with SHA-1 or SHA-256. A key-chaining scheme may also be employed to facilitate re-keying as needed. ESP is not used, since the mapping data is considered to be public and does not need to be encrypted for transport. Fuller & Farinacci Expires March 8, 2010 [Page 11] Internet-Draft LISP Map Server September 2009 7. References 7.1. Normative References [RFC1035] Mockapetris, P., "Domain names - implementation and specification", STD 13, RFC 1035, November 1987. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2402] Kent, S. and R. Atkinson, "IP Authentication Header", RFC 2402, November 1998. 7.2. Informative References [ALT] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "LISP Alternative Topology (LISP-ALT)", draft-ietf-lisp-alt-01.txt (work in progress), March 2009. [CONS] Farinacci, D., Fuller, V., and D. Meyer, "LISP-CONS: A Content distribution Overlay Network Service for LISP", draft-meyer-lisp-cons-03.txt (work in progress), November 2007. [LISP] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "Locator/ID Separation Protocol (LISP)", draft-ietf-lisp-04.txt (work in progress) (work in progress), September 2009. [NERD] Lear, E., "NERD: A Not-so-novel EID to RLOC Database", draft-lear-lisp-nerd-04.txt (work in progress), January 2008. Fuller & Farinacci Expires March 8, 2010 [Page 12] Internet-Draft LISP Map Server September 2009 Appendix A. Acknowledgments The authors would also like to thank the operational community for feedback on the previous mapping database mechanisms. Special thanks are due to Noel Chiappa for his extensive work on caching with LISP-CONS, some of which will be used by Map-Resolvers. Fuller & Farinacci Expires March 8, 2010 [Page 13] Internet-Draft LISP Map Server September 2009 Authors' Addresses Vince Fuller cisco Systems Tasman Drive San Jose, CA 95134 USA Email: vaf@cisco.com Dino Farinacci cisco Systems Tasman Drive San Jose, CA 95134 USA Email: dino@cisco.com Fuller & Farinacci Expires March 8, 2010 [Page 14]