--- 1/draft-ietf-lisp-alt-02.txt 2010-03-30 00:10:53.000000000 +0200 +++ 2/draft-ietf-lisp-alt-03.txt 2010-03-30 00:10:53.000000000 +0200 @@ -1,32 +1,31 @@ Network Working Group V. Fuller Internet-Draft D. Farinacci Intended status: Experimental D. Meyer -Expires: July 29, 2010 D. Lewis +Expires: September 30, 2010 D. Lewis Cisco - January 25, 2010 + March 29, 2010 LISP Alternative Topology (LISP+ALT) - draft-ietf-lisp-alt-02.txt + draft-ietf-lisp-alt-03.txt Abstract - This document describes a method of building an alternative, logical - topology for managing Endpoint Identifier to Routing Locator mappings - using the Locator/ID Separation Protocol. The logical network is - built as an overlay on the public Internet using existing - technologies and tools, specifically the Border Gateway Protocol and - the Generic Routing Encapsulation. An important design goal for - LISP+ALT is to allow for the relatively easy deployment of an - efficient mapping system while minimizing changes to existing - hardware and software. + This document describes a simple mapping database to be used by the + Locator/ID Separation Protocol (LISP) to find Endpoint Identifier + (EID) to Routing Locator (RLOC) mappings. Termed the Alternative + Logical Topology (ALT), the database is built as an overlay network + on the public Internet using the Border Gateway Protocol (BGP) and + the Generic Routing Encapsulation (GRE). Using these proven + protocols, the ALT can be built and deployed relatively quickly + without major changes to the existing routing infrastructure. 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. @@ -35,23 +34,24 @@ 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 July 29, 2010. + This Internet-Draft will expire on September 30, 2010. Copyright Notice + Copyright (c) 2010 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 @@ -53,797 +53,971 @@ (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. Requirements Notation . . . . . . . . . . . . . . . . . . . . 4 - 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5 - 3. Definition of Terms . . . . . . . . . . . . . . . . . . . . . 6 - 4. The LISP 1.5 model . . . . . . . . . . . . . . . . . . . . . . 8 - 4.1. Routeability of EIDs . . . . . . . . . . . . . . . . . . . 8 - 4.2. Connectivity to non-LISP sites . . . . . . . . . . . . . . 9 - 4.3. Caveats on the use of Data Probes . . . . . . . . . . . . 9 - 5. LISP+ALT: Overview . . . . . . . . . . . . . . . . . . . . . . 10 - 5.1. ITR traffic handling . . . . . . . . . . . . . . . . . . . 11 - 5.2. EID Assignment - Hierarchy and Topology . . . . . . . . . 11 - 5.3. LISP+ALT Router (or ALT router for short) . . . . . . . . 12 - 5.4. ITR and ETR in a LISP+ALT Environment . . . . . . . . . . 13 - 5.5. Use of GRE and BGP between LISP+ALT Routers . . . . . . . 13 - 6. EID Prefix Propagation and Map-Request Forwarding . . . . . . 14 - 6.1. Changes to ITR behavior with LISP+ALT . . . . . . . . . . 14 - 6.2. Changes to ETR behavior with LISP+ALT . . . . . . . . . . 14 - 7. BGP configuration and protocol considerations . . . . . . . . 16 - 7.1. Autonomous System Numbers (ASNs) in LISP+ALT . . . . . . . 16 - 7.2. Sub-Address Family Identifier (SAFI) for LISP+ALT . . . . 16 - 8. EID-Prefix Aggregation . . . . . . . . . . . . . . . . . . . . 17 - 8.1. Traffic engineering with LISP and LISP+ALT . . . . . . . . 17 - 8.2. Edge aggregation and dampening . . . . . . . . . . . . . . 18 - 9. Connecting sites to the ALT network . . . . . . . . . . . . . 19 - 9.1. ETRs originating information into the ALT . . . . . . . . 19 - 9.2. ITRs Using the ALT . . . . . . . . . . . . . . . . . . . . 19 - 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 21 - 11. Security Considerations . . . . . . . . . . . . . . . . . . . 22 - 11.1. Apparent LISP+ALT Vulnerabilities . . . . . . . . . . . . 22 - 11.2. Survey of LISP+ALT Security Mechanisms . . . . . . . . . . 23 - 11.3. Using existing BGP Security mechanisms . . . . . . . . . . 23 - 12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 24 - 13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 25 - 13.1. Normative References . . . . . . . . . . . . . . . . . . . 25 - 13.2. Informative References . . . . . . . . . . . . . . . . . . 25 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 26 + 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 + 2. Definition of Terms . . . . . . . . . . . . . . . . . . . . . 5 + 3. The LISP+ALT model . . . . . . . . . . . . . . . . . . . . . . 8 + 3.1. Routeability of EIDs . . . . . . . . . . . . . . . . . . . 8 + 3.1.1. Mechanisms for an ETR to originate EID-prefixes . . . 9 + 3.1.2. Mechanisms for an ITR to forward to EID-prefixes . . . 9 + 3.1.3. Map Server Model preferred . . . . . . . . . . . . . . 9 + 3.2. Connectivity to non-LISP sites . . . . . . . . . . . . . . 9 + 3.3. Caveats on the use of Data Probes . . . . . . . . . . . . 10 + 4. LISP+ALT: Overview . . . . . . . . . . . . . . . . . . . . . . 11 + 4.1. ITR traffic handling . . . . . . . . . . . . . . . . . . . 12 + 4.2. EID Assignment - Hierarchy and Topology . . . . . . . . . 12 + 4.3. Use of GRE and BGP between LISP+ALT Routers . . . . . . . 14 + 5. EID-prefix Propagation and Map-Request Forwarding . . . . . . 15 + 5.1. Changes to ITR behavior with LISP+ALT . . . . . . . . . . 15 + 5.2. Changes to ETR behavior with LISP+ALT . . . . . . . . . . 15 + 6. BGP configuration and protocol considerations . . . . . . . . 17 + 6.1. Autonomous System Numbers (ASNs) in LISP+ALT . . . . . . . 17 + 6.2. Sub-Address Family Identifier (SAFI) for LISP+ALT . . . . 17 + 7. EID-prefix Aggregation . . . . . . . . . . . . . . . . . . . . 18 + 7.1. Stability of the ALT . . . . . . . . . . . . . . . . . . . 18 + 7.2. Traffic engineering using LISP . . . . . . . . . . . . . . 18 + 7.3. Edge aggregation and dampening . . . . . . . . . . . . . . 19 + 7.4. EID assignment flexibility vs. ALT scaling . . . . . . . . 19 + 8. Connecting sites to the ALT network . . . . . . . . . . . . . 21 + 8.1. ETRs originating information into the ALT . . . . . . . . 21 + 8.2. ITRs Using the ALT . . . . . . . . . . . . . . . . . . . . 21 + 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23 + 10. Security Considerations . . . . . . . . . . . . . . . . . . . 24 + 10.1. Apparent LISP+ALT Vulnerabilities . . . . . . . . . . . . 24 + 10.2. Survey of LISP+ALT Security Mechanisms . . . . . . . . . . 25 + 10.3. Use of new IETF standard BGP Security mechanisms . . . . . 25 + 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 26 + 12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 27 + 12.1. Normative References . . . . . . . . . . . . . . . . . . . 27 + 12.2. Informative References . . . . . . . . . . . . . . . . . . 27 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 28 -1. Requirements Notation +1. Introduction - 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]. + This document describes the LISP+ALT mapping database, to be used by + LISP to find EID-to-RLOC mappings. The ALT network is built using + the Border Gateway Protocol (BGP, [RFC4271]), the BGP multi-protocol + extension [RFC4760], and the Generic Routing Encapsulation (GRE, + [RFC2784]) to construct an overlay nnetwork of devices (ALT Routers) + which operate on EID-prefixes and use EIDs as forwarding + destinations. -2. Introduction + ALT Routers advertise hierarchically-delegated segments of the EID + namespace (i.e., prefixes) toward the rest of the ALT; they also + forward traffic destined for an EID covered by one of those prefixes + toward the network element which is authoritative for that EID (i.e. + is the origin of the advertisement of the EID-to-RLOC mapping which + applies to that EID). Map Resolvers (MRs; see [LISP-MS]) and, in + some cases, Ingress Tunnel Routers (ITRs) use this overlay to send + mapping requests (using [LISP]) to the Egress Tunnel Routers (ETRs) + that hold the EID-to-RLOC mappings for a particular EID-prefix - This document describes a method of building an alternative logical - topology for managing Endpoint identifier to Routing Locator mappings - using the Locator/ID Separation Protocol [LISP]. This logical - topology uses existing technology and tools, specifically the Border - Gateway Protocol [RFC4271] and its multi-protocol extension - [RFC2858], along with the Generic Routing Encapsulation [RFC2784] - protocol to construct an overlay network of devices that advertise - EID-prefixes only. These Endpoint Identifier Prefix Aggregators hold - hierarchically-assigned pieces of the Endpoint Identifier space - (i.e., prefixes) and their next hops toward the network element which - is authoritative for Endpoint Identifier-to-Routing Locator mapping - for that prefix. Tunnel routers can use this overlay to make queries - against and respond to mapping requests made against the distributed - Endpoint Identifier-to-Routing Locator mapping database. Note the - database is distributed (as described in [LISP]) and is stored in the - ETRs. + It is important to note that the ALT does not distribute actual EID- + to-RLOC mappings. What it does provide is a forwarding path from an + ITR (or MR) which requires an EID-to-RLOC mapping to an ETR which + holds that mapping. The ITR/MR uses this path to send an ALT + Datagram (see Section 3) to an ETR which then responds with a Map- + Reply containing the needed mapping information. - Note that an important design goal of LISP+ALT is to minimize the - number of changes to existing hardware and/or software that are - required to deploy the mapping system. It is envisioned that in most - cases existing technology can be used to implement and deploy LISP+ - ALT. Since the deployment of LISP+ALT adds new devices to the - network, existing devices not need changes or upgrades. They can - function as they are to realize an underlying and robust physical - topology. + One design goal for LISP+ALT is to use existing technology wherever + possible. To this end, the ALT is intended to be built using off- + the-shelf routers which already implement the required protocols (BGP + and GRE); little, if any, LISP-specific modifications should be + needed for such devices to be deployed on the ALT. Note, though, + that organizational and operational considerations suggest that ALT + Routers be both logically and physically separate from the "native" + Internet packet transport system; deploying this overlay on those + routers which are already participating in the global routing system + and actively forwarding Internet traffic is not recommended. - The remainder of this document is organized as follows: Section 3 - provides the definitions of terms used in this document. Section 4 - outlines the basic LISP 1.5 model. Section 5 provides a basic - overview of the LISP Alternate Topology architecture, and Section 6 + The remainder of this document is organized as follows: Section 2 + provides the definitions of terms used in this document. Section 3 + outlines the basic LISP 1.5 model. Section 4 provides a basic + overview of the LISP Alternate Topology architecture, and Section 5 describes how the ALT uses BGP to propagate Endpoint Identifier - reachability over the overlay network. Section 8 describes the - construction of the ALT aggregation hierarchy, and Section 9 + reachability over the overlay network and Section 6 describes other + considerations for using BGP on the ALT. Section 7 describes the + construction of the ALT aggregation hierarchy, and Section 8 discusses how LISP+ALT elements are connected to form the overlay network. -3. Definition of Terms +2. Definition of Terms LISP+ALT operates on two name spaces and introduces a new network element, the LISP+ALT Router (see below). This section provides high-level definitions of the LISP+ALT name spaces, network elements, and message types. - The Alternative Logical Topology (ALT): The virtual overlay network - made up of tunnels between EID Prefix Aggregators. The Border - Gateway Protocol (BGP) runs between ALT routers and is used to - carry reachability information for EID prefixes. - - Legacy Internet: The portion of the Internet which does not run LISP - and does not participate in LISP+ALT. + Alternative Logical Topology (ALT): The virtual overlay network + made up of tunnels between LISP+ALT Routers. The Border Gateway + Protocol (BGP) runs between ALT Routers and is used to carry + reachability information for EID-prefixes. The ALT provides a way + to forward Map-Requests (and, if supported, Data Probes) toward + the ETR that "owns" an EID-prefix. As a tunneled overlay, its + performance is expected to be quite limited so use of it to + forward high-bandwidth flows of Data Probes is strongly + discouraged (see Section 3.3 for additional discussion). - LISP+ALT Router: The devices which run on the ALT. The ALT is a - static network built using tunnels between LISP+ALT routers. - These routers are deployed in a hierarchy in which routers at each - level in the this hierarchy are responsible for aggregating all - EID prefixes learned from those logically "below" them and - advertising summary prefixes to the routers logically "above" - them. All prefix learning and propagation between levels is done - using BGP. A LISP+ALT router at the lowest level, or "edge" of - the ALT, learns EID prefixes from its "client" ETRs. See - Section 4.1 for a description of how EID prefixes are learned at - the "edge" of the ALT. See also Section 7 for details on how BGP - is configured between the different network elements. + Legacy Internet: The portion of the Internet which does not run + LISP and does not participate in LISP+ALT. - The primary function of LISP+ALT routers is to provide a - lightweight forwarding infrastructure for LISP control-plane - messages (Map-Request and Map-Reply), and to transport data - packets when the packet has the same destination address in both - the inner (encapsulating) destination and outer destination - addresses ((i.e., a Data Probe packet). + ALT Router: The devices which run on the ALT. The ALT is a static + network built using tunnels between ALT Routers. These routers + are deployed in a roughly-hierarchical mesh in which routers at + each level in the topology are responsible for aggregating EID- + prefixes learned from those logically "below" them and advertising + summary prefixes to those logically "above" them. Prefix learning + and propagation between ALT Routers is done using BGP. An ALT + Router at the lowest level, or "edge" of the ALT, learns EID- + prefixes from its "client" ETRs. See Section 3.1 for a + description of how EID-prefixes are learned at the "edge" of the + ALT. See also Section 6 for details on how BGP is configured + between the different network elements. When an ALT Router + receives an ALT Datagram, it looks up the destination EID in its + forwarding table (composed of EID prefix routes it learned from + neighboring ALT Routers) and forwards it to the logical next-hop + on the overlay network. Endpoint ID (EID): A 32-bit (for IPv4) or 128-bit (for ipv6) value - used in the source and destination address fields of the first - (most inner) LISP header of a packet. A packet that is emitted by - a system contains EIDs in its headers and LISP headers are - prepended only when the packet reaches an Ingress Tunnel Router - (ITR) on the data path to the destination EID. + used to identify the ultimate source or destination for a LISP- + encapsulated packet. See [LISP] for details. - In LISP+ALT, EID-prefixes MUST BE assigned in a hierarchical - manner (in power-of-two) such that they can be aggregated by LISP+ - ALT routers. In addition, a site may have site-local structure in - how EIDs are topologically organized (subnetting) for routing - within the site; this structure is not visible to the global - routing system. + EID-prefix: A set of EIDs delegated in a power-of-two block. EID- + prefixes are routed on the ALT (not on the global Internet) and + are expected to be assigned in a hierarchical manner such that + they can be aggregated by ALT Routers. Such a block is + characterized by a prefix and a length. Note that while the ALT + routing system considers an EID-prefix to be an opaque block of + EIDs, an end site may put site-local, topologically-relevant + structure (subnetting) into an EID-prefix for intra-site routing. - EID-Prefix Aggregate: A set of EID-prefixes said to be aggregatable - in the [RFC4632] sense. That is, an EID-Prefix aggregate is - defined to be a single contiguous power-of-two EID-prefix block. - Such a block is characterized by a prefix and a length. + Aggregated EID-prefixes: A set of individual EID-prefixes that have + been aggregated in the [RFC4632] sense. - Routing Locator (RLOC): An IP address of an egress tunnel router - (ETR). It is the output of a EID-to-RLOC mapping lookup. An EID - maps to one or more RLOCs. Typically, RLOCs are numbered from - topologically-aggregatable blocks that are assigned to a site at - each point to which it attaches to the global Internet; where the - topology is defined by the connectivity of provider networks, - RLOCs can be thought of as Provider Aggregatable (PA) addresses. - Note that in LISP+ALT, RLOCs are not carried by LISP+ALT routers. + Map Server (MS): An edge ALT Router that provides a registration + function for non-ALT-connected ETRs, originates EID-prefixes into + the ALT on behalf of those ETRs, and forwards Map-Requests to + them. See [LISP-MS] for details. - EID-to-RLOC Mapping: A binding between an EID and the RLOC-set that - can be used to reach the EID. The term "mapping" refers to an - EID-to-RLOC mapping. + Map Resolver (MR): An edge ALT Router that accepts an Encapsulated + Map-Request from a non-ALT-connected ITR, decapsulates it, and + forwards it on to the ALT toward the ETR which owns the requested + EID-prefix. See [LISP-MS] for details. - EID Prefix Reachability: An EID prefix is said to be "reachable" if - one or more of its locators are reachable. That is, an EID prefix - is reachable if the ETR (or its proxy) that is authoritative for a - given EID-to-RLOC mapping is reachable. + Ingress Tunnel Router (ITR): A router which sends LISP Map- + Requests or encapsulates IP datagrams with LISP headers, as + defined in [LISP]. In this document, the term refers to any + device implementing ITR functionality, including a Proxy-ITR (see + [LISP-IW]). Under some circumstances, a LISP Map Resolver may + also originate Map-Requests (see [LISP-MS]). + + Egress Tunnel Router (ETR): A router which sends LISP Map-Replies + in response to LISP Map-Requests and decapsulates LISP- + encapsulated IP datagrams for delivery to end systems, as defined + in [LISP]. In this document, the term refers to any device + implementing ETR functionality, including a Proxy-ETR (see + [LISP-IW]). Under some circumstances, a LISP Map Server may also + respond to Map-Requests (see [LISP-MS]). + + Routing Locator (RLOC): A routable IP address for a LISP tunnel + router (ITR or ETR). Interchangeably referred to as a "locator" + in this document. An RLOC is also the output of an EID-to-RLOC + mapping lookup; an EID-prefix maps to one or more RLOCs. + Typically, RLOCs are numbered from topologically-aggregatable + blocks that are assigned to a site at each point where it attaches + to the global Internet; where the topology is defined by the + connectivity of provider networks, RLOCs can be thought of as + Provider Aggregatable (PA) addresses. Routing for RLOCs is not + carried on the ALT. + + EID-to-RLOC Mapping: A binding between an EID-prefix and the set of + RLOCs that can be used to reach it; sometimes referred to simply + as a "mapping". + + EID-prefix Reachability: An EID-prefix is said to be "reachable" if + at least one of its locators is reachable. That is, an EID-prefix + is reachable if the ETR that is authoritative for a given EID-to- + RLOC mapping is reachable. Default Mapping: A Default Mapping is a mapping entry for EID- prefix 0.0.0.0/0 (0::/0 for ipv6). It maps to a locator-set used for all EIDs in the Internet. If there is a more specific EID- prefix in the mapping cache it overrides the Default Mapping - entry. The Default Mapping route can be learned by configuration - or from a Map-Reply message. + entry. The Default Mapping can be learned by configuration or + from a Map-Reply message. - Default Route: A Default Route in the context of LISP+ALT is a EID- - prefix value of 0.0.0.0/0 (or 0::/0 for ipv6) which is advertised - by BGP on top of the ALT. The Default Route is used to create a - forwarding path for a packet to be sent into the ALT (and ALT - datagram) on a router which does not have a full ALT forwarding - database. + ALT Default Route: An EID-prefix value of 0.0.0.0/0 (or 0::/0 for + ipv6) which may be learned from the ALT or statically configured + on an edge ALT Router. The ALT-Default Route defines a forwarding + path for a packet to be sent into the ALT on a router which does + not have a full ALT forwarding database. -4. The LISP 1.5 model +3. The LISP+ALT model - As documented in [LISP], the LISP 1.5 model uses the same basic - query/response protocol machinery as LISP 1.0. In particular, LISP+ - ALT provides two mechanisms for an ITR to obtain EID-to-RLOC mappings - (both of these techniques are described in more detail in - Section 9.2): + The LISP+ALT model uses the same basic query/response protocol that + is documented in [LISP]. In particular, LISP+ALT provides two types + of packet that an ITR can originate to obtain EID-to-RLOC mappings: - Data Probe: An ITR may send the first few data packets into the ALT - to minimize packet loss and to probe for the mapping; the - authoritative ETR will respond to the ITR with a Map-Reply message - when it receives the data packet over the ALT. Note that in this - case, the inner Destination Address (DA), which is an EID, is - copied to the outer DA and is routed over the ALT. + Map-Request: A Map-Request message is sent into the ALT to request + an EID-to-RLOC mapping. The ETR which owns the mapping will + respond to the ITR with a Map-Reply message. Since the ALT only + forwards on EID destinations, the destination address of the Map- + Request sent on the ALT must be an EID. See [LISP] for the format + of Map-Request and Map-Reply packets. - Map-Request: An ITR may also send a Map-Request message into the ALT - to request the mapping. As in the Data Probe case, the - authoritative ETR will respond to the ITR with a Map-Reply - message. Since the ALT only forwards on EID destinations, the DA - of the Map-Request sent in to the ALT MUST be an EID. See [LISP] - for the format of Map-Request and Map-Reply packets. + Data Probe: Alternatively, an ITR may encapsulate and send the first + data packet destined for an EID with no known RLOCs into the ALT + as a Data Probe. This might be done minimize packet loss and to + probe for the mapping. As above, the authoritative ETR for the + EID-prefix will respond to the ITR with a Map-Reply message when + it receives the data packet over the ALT. As a side-effect, the + encapsulated data packet is delivered to the end-system at the ETR + site. Note that the Data Probe's inner IP destination address, + which is an EID, is copied to the outer IP destination address so + that the resulting packet can be routed over the ALT. See + Section 3.3 for caveats on the usability of Data Probes. - ALT datagram: A Map-Request or Data Probe to be sent into or - forwarded on the ALT. + The term "ALT Datagram" is short-hand for a Map-Request or Data Probe + to be sent into or forwarded on the ALT. Note that while the outer + header Source Address of an ALT Datagram is currently expected to be + an RLOC, there may be situations (e.g. for experimentation with + caching in intermediate ALT nodes) where an EID would be used to + force a Map-Reply to be routed back through the ALT. -4.1. Routeability of EIDs +3.1. Routeability of EIDs - As with LISP 1.0, EIDs are routable and can be used, unaltered, as - the source and destination addresses in IP datagrams. Unlike in LISP - 1.0, LISP 1.5 EIDs are not routable on the public Internet; instead, - they are only routed over a separate, virtual topology referred to as - the LISP Alternative Virtual Network. This network is built as an - overlay on the public Internet using tunnels to interconnect LISP+ALT - routers. BGP is run over these tunnels to propagate the information - needed to route ALT datagrams. Importantly, while the ETRs are the - source(s) of the unaggregated EID prefix data, LISP+ALT uses existing - BGP mechanisms to aggressively aggregate this information. Note that - an ETR is not required to participate (or prevented from - participating) in LISP+ALT; an ETR may choose to communicate its - mappings to its serving LISP+ALT router(s) using subscription time - static configuration or through a dynamic mechanism such as that - described in [LISP-MS]. An ITR may similarly use a static EID - "default route" or other configuration as described in [LISP-MS] to - avoid the complexity of participating in the ALT. + A LISP EID has the same syntax as IP address and can be used, + unaltered, as the source or destination of an IP datagram. In + general, though, EIDs are not routable on the public Internet; LISP+ + ALT provides a separate, virtual network, known as the LISP + Alternative Logical Topology (ALT) on which a datagram using an EID + as an IP destination address may be transmitted. This network is + built as an overlay on the public Internet using tunnels to + interconnect ALT Routers. BGP runs over these tunnels to propagate + path information needed to forward ALT Datagrams. Importantly, while + the ETRs are the source(s) of the unaggregated EID-prefixes, LISP+ALT + uses existing BGP mechanisms to aggregate this information. -4.2. Connectivity to non-LISP sites +3.1.1. Mechanisms for an ETR to originate EID-prefixes + + There are three ways that an ETR may originate its mappings into the + ALT: + + 1. By registration with a Map Server as documented in [LISP-MS]. + This is the common case and is expected to be used by the + majority of ETRs. + + 2. Using a "static route" on the ALT. Where no Map-Server is + available, an edge ALT Router may be configured with a "static + EID-prefix route" pointing to an ETR. + + 3. Edge connection to the ALT. If a site requires fine- grained + control over how its EID-prefixes are advertised into the ALT, it + may configure its ETR(s) with tunnel and BGP connections to edge + ALT Routers. + +3.1.2. Mechanisms for an ITR to forward to EID-prefixes + + There are three ways that an ITR may send ALT Datagrams: + + 1. Through a Map Resolver as documented in [LISP-MS]. This is the + common case and is expected to be used by the majority of ITRs. + + 2. Using a "default route". Where a Map Resolver is not available, + an ITR may be configured with a static ALT Default Route pointing + to an edge ALT Router. + + 3. Edge connection to the ALT. If a site requires fine-grained + knowledge of what prefixes exist on the ALT, it may configure its + ITR(s) with tunnel and BGP connections to edge ALT Routers. + +3.1.3. Map Server Model preferred + + The ALT-connected ITR and ETR cases are expected to be rare, as the + Map Server/Map Resolver model is both simpler for an ITR/ETR operator + to use, and provides a more general service interface to not only the + ALT, but also to other mapping databases that may be developed in the + future. + +3.2. Connectivity to non-LISP sites As stated above, EIDs used as IP addresses by LISP sites are not routable on the public Internet. This implies that, absent a mechanism for communication between LISP and non-LISP sites, connectivity between them is not possible. To resolve this problem, - an "interworking" technology has been defined; see [Interworking] for + an "interworking" technology has been defined; see [LISP-IW] for details. -4.3. Caveats on the use of Data Probes +3.3. Caveats on the use of Data Probes It is worth noting that there has been a great deal of discussion and controversy about whether Data Probes are a good idea. On the one hand, using them offers a method of avoiding the "first packet drop" problem when an ITR does not have a mapping for a particular EID- prefix. On the other hand, forwarding data packets on the ALT would require that it either be engineered to support relatively high traffic rates, which is not generally feasible for a tunneled network, or that it be carefully designed to aggressively rate- limit - traffic to avoid congestion or DoS attacks. There are also other - issues involving latency or other differences between the ALT path - that initial a Data Probe would take and the path that subsequent - packets on the same flow would take once a mapping were in place on - an ITR. For these and other reasons use of Data Probes should be - considered experimental and should be disabled by default in all ITR - implementations. + traffic to avoid congestion or DoS attacks. There may also be issues + caused by different latency or other performance characteristics + between the ALT path taken by an initial Data Probe and the + "Internet" path taken by subsequent packets on the same flow once a + mapping is in place on an ITR. For these reasons, the use of Data + Probes is not recommended at this time; they should only be + originated an ITR when explicitly configured to do so and such + configuration should only be enabled when performing experiments + intended to test the viability of using Data Probes. -5. LISP+ALT: Overview +4. LISP+ALT: Overview - LISP+ALT is a hybrid push/pull architecture. Aggregated EID prefixes - are "pushed" among the LISP+ALT routers and, optionally, out to ITRs - (which may elect to receive the aggregated information, as opposed to - simply using a default mapping). Specific EID-to-RLOC mappings are - "pulled" by ITRs when they either send explicit LISP requests or data - packets on the alternate topology that result in triggered replies - being generated by ETRs. + LISP+ALT is a hybrid push/pull architecture. Aggregated EID-prefixes + are advertised among the ALT Routers and to those (rare) ITRs that + are directly connected via a tunnel and BGP to the ALT. Specific + EID-to-RLOC mappings are requested by an ITR (and returned by an ETR) + using LISP when it sends a request either via a Map Resolver or to an + edge ALT Router. - The basic idea embodied in LISP+ALT is to use BGP, running over - tunneled overlay network, to establish reachability required to route - ALT datagrams over an alternate logical topology (ALT). The ALT - BGPRoute Information Base (RIB) is comprised of EID prefixes and - associated next hops. LISP+ALT routers interconnect using eBGP and - propagate EID prefix updates, which are learned over eBGP connections - to authoritative ETRs, or by static configuration. ITRs may also - eBGP peer with one or more LISP+ALT to learn the best ALT router to - use to forward an ALT datagram for a particular prefix; in most - cases, an ITR will have a default EID mapping pointing to one or more - LISP+ALT routers. + The basic idea embodied in LISP+ALT is to use BGP, running on a + tunneled overlay network (the ALT), to establish reachability between + ALT Routers. The ALT BGP Route Information Base (RIB) is comprised + of EID-prefixes and associated next hops. ALT Routers interconnect + using BGP and propagate EID-prefix updates among themselves. EID- + prefix information is learned from ETRs at the "edge" of the ALT + either through the use of the Map Server interface (the commmon + case), static configuration, or by BGP-speaking ETRs. + + An ITR uses the ALT to learn the best path for forwarding an ALT + Datagram destined to a particular EID-prefix. An ITR will normally + use a Map Resolver to send its ALT Datagrams on to the ALT but may, + in unusual circumstances, use a static ALT Default Route or connect + to the ALT using BGP. Note that while this document specifies the use of Generic Routing Encapsulation (GRE) as a tunneling mechanism, there is no reason that - an ALT cannot be built using other tunneling technologies. In cases - where GRE does not meet security, management, or other operational - requirements, it is reasonable to use another tunneling technology - that does. References to "GRE tunnel" in later sections of this - document should therefore not be taken as prohibiting or precluding - the use of other, available tunneling mechanisms. Note also that two - LISP+ALT routers that are directly adjacent (with no layer-3 router - hops between them) need not use a tunnel between them; in this case, - BGP may be configured across the interfaces that connect to their - common subnet and that subnet is considered to be part of the ALT - topology. Use of techniques, such as "eBGP multihop", to forward ALT - datagrams through routers that do not participate in ALT routing, is - not recommended. + parts of the ALT cannot be built using other tunneling technologies, + particularly in cases where GRE does not meet security, management, + or other operational requirements. References to "GRE tunnel" in + later sections of this document should therefore not be taken as + prohibiting or precluding the use of other tunneling mechanisms. + Note also that two ALT Routers that are directly adjacent (with no + layer-3 router hops between them) need not use a tunnel between them; + in this case, BGP may be configured across the interfaces that + connect to their common subnet and that subnet is then considered to + be part of the ALT topology. Use of techniques such as "eBGP + multihop" to connect ALT Routers that do not share a tunnel or common + subnet is not recommended as the non-ALT Routers in between the ALT + Routers in such a configuration may not have information necessary to + forward ALT Datagrams destined to EID-prefixes exchanged across that + BGP session. - In summary, LISP+ALT uses BGP to propagate EID-prefix update - information to facilitate forwarding an ALT datagram to the ETR that - holds the EID-to-RLOC mapping for that EID-prefix. This reachability - is carried as IPv4 or IPv6 NLRI without modification (since an EID - prefix has the same syntax as IPv4 or IPv6 address prefix). LISP+ALT - routers eBGP peer with one another, forming the ALT. A LISP+ALT - router near the edge learns EID prefixes originated by authoritative - ETRs. This may be via eBGP with the ETRs, by static configuration, - or through some other dynamic mechanism such as that defined in - [LISP-MS]. A LISP+ALT router may also be configured to aggregate EID - prefixes received from ETRs or from other LISP+ALT routers that are - topologically "downstream" from it. + In summary, LISP+ALT uses BGP to build paths through ALT Routers so + that an ALT Datagram sent into the ALT can be forwarded to the ETR + that holds the EID-to-RLOC mapping for that EID-prefix. This + reachability is carried as IPv4 or ipv6 NLRI without modification + (since an EID-prefix has the same syntax as IPv4 or ipv6 address + prefix). ALT Routers establish BGP sessions with one another, + forming the ALT. An ALT Router at the "edge" of the topology learns + EID-prefixes originated by authoritative ETRs. Learning may be + though the Map Server interface, by static configuration, or via BGP + with the ETRs. An ALT Router may also be configured to aggregate + EID-prefixes received from ETRs or from other LISP+ALT routers that + are topologically "downstream" from it. -5.1. ITR traffic handling +4.1. ITR traffic handling When an ITR receives a packet originated by an end system within its site (i.e. a host for which the ITR is the exit path out of the site) - and the destination for that packet is not known in the ITR's mapping - cache, the ITR encapsulates the packet in a LISP header, copying the - inner destination address (EID) to the outer destination address - (RLOC), and transmits it through a GRE tunnel to a LISP+ALT router in - the ALT (see also [LISP-MS] for non-ALT-connected ITRs, noting that - an ITR cannot send Data Probes to a Map-Server). This "first hop" - LISP+ALT router uses EID-prefix routing information learned from - other LISP+ALT routers via BGP to guide the packet to the ETR which - "owns" the prefix. Upon receipt by the ETR, normal LISP processing - occurs: the ETR responds to the ITR with a LISP Map-Reply that lists - the RLOCs (and, thus, the ETRs to use) for the EID prefix. The ETR - also de-encapsulates the packet and transmits it toward its - destination. + and the destination EID for that packet is not known in the ITR's + mapping cache, the ITR creates either a Map-Request for the + destination EID or the original packet encapsulated as a Data Probe + (see Section 3.3 for caveats on the usability of Data Probes). The + result, known as an ALT Datagram, is then sent to an ALT Router (see + also [LISP-MS] for non-ALT-connected ITRs, noting that Data Probes + cannot be sent to a Map-Resolver). This "first hop" ALT Router uses + EID-prefix routing information learned from other ALT Routers via BGP + to guide the packet to the ETR which "owns" the prefix. Upon receipt + by the ETR, normal LISP processing occurs: the ETR responds to the + ITR with a LISP Map-Reply that lists the RLOCs (and, thus, the ETRs + to use) for the EID-prefix. For Data Probes, the ETR also + decapsulates the packet and transmits it toward its destination. Upon receipt of the Map-Reply, the ITR installs the RLOC information for a given prefix into a local mapping database. With these mapping - entries stored, additional packets destined to the given EID prefix - are routed directly to a viable ETR without use of the ALT, until - either the entry's TTL has expired, or the ITR can otherwise find no - reachable ETR. Note that a valid mapping (not timed-out) may exist - that contains no reachable RLOCs (i.e. all paths to that ETR are - down); in this case, packets destined to the EID prefix are dropped, - not routed through the ALT. - - Traffic routed over the ALT therefore consists of: - - o EID prefix Map-Requests, and + entries stored, additional packets destined to the given EID-prefix + are routed directly to an RLOC without use of the ALT, until either + the entry's TTL has expired, or the ITR can otherwise find no + reachable ETR. Note that a current mapping may exist that contains + no reachable RLOCs; this is known as a Negative Cache Entry and it + indicates that packets destined to the EID-prefix are to be dropped. - o data packets destined for those EID prefixes while the ITR awaits - map replies + Full details on Map-Request/Map-Reply processing may be found in + [LISP]. -5.2. EID Assignment - Hierarchy and Topology + Traffic routed on to the ALT consists solely of ALT Datagrams, i.e. + Map-Requests and Data Probes (if supported). Given the relatively + low performance expected of a tuneled topology, ALT Routers (and Map + Resolvers) should aggressively rate-limit the ingress of ALT + Datagrams from ITRs and, if possible, should be configured to not + accept packets that are not ALT Datagrams. - EID-prefixes will be allocated to a LISP site by Internet Registries. - Multiple allocations may not be in power-of-2 blocks. But when they - are, they will be aggregated into a single, advertised EID-prefix. - The ALT network is built in a tree-structured hierarchy to allow - aggregation at merge points in the tree. Building such a structure - should minimize the number of EID-prefixes carried by LISP+ALT nodes - near the top of the hierarchy. +4.2. EID Assignment - Hierarchy and Topology - Since the ALT will not need to change due to subscription or policy - reasons, the topology can remain relatively static and aggregation - can be sustained. Because routing on the ALT uses BGP, the same - rules apply for generating aggregates; in particular, a LISP+ALT - router should only be configured to generate an aggregate if it is - configured with BGP sessions to all of the originators of components - (more-specifics prefixes) of that aggregate; not all of the - components of need to be present for the aggregate to be originated - (some may be holes in the covering prefix and some may be down) but - the aggregating router must be configured to learn the state of all - of the components. + EID-prefixes are expected to be allocated to a LISP site by Internet + Registries. Where a site has multiple allocations which are aligned + on a power-of-2 block boundary, they should be aggregated into a + single EID-prefix for advertisement. The ALT network is built in a + roughly hierarchical, partial mesh which is intended to allow + aggregation where clearly-defined hierarchical boundaries exist. + Building such a structure should minimize the number of EID-prefixes + carried by LISP+ALT nodes near the top of the hierarchy. - As an example, consider ETRs that are originating EID prefixes for - 10.1.0.0/24, 10.1.64.0/24, 10.1.128.0/24, and 10.1.192.0/24. An ALT - router should only be configured to generate an aggregate for - 10.1.0.0/16 if it has BGP sessions configured with all of these ETRs, - in other words, only if it has sufficient knowledge about the state - of those prefixes to summarize them. + Routes on the ALT do not need to respond to changes in policy, + subscription, or underlying physical connectivity, so the topology + can remain relatively static and aggregation can be sustained. + Because routing on the ALT uses BGP, the same rules apply for + generating aggregates; in particular, a ALT Router should only be + configured to generate an aggregate if it is configured with BGP + sessions to all of the originators of components (more-specific + prefixes) of that aggregate. Not all of the components of need to be + present for the aggregate to be originated (some may be holes in the + covering prefix and some may be down) but the aggregating router must + be configured to learn the state of all of the components. - Under what circumstances the ALT router actually generates the + Under what circumstances the ALT Router actually generates the aggregate is a matter of local policy: in some cases, it will be statically configured to do so at all times with a "static discard" route. In other cases, it may be configured to only generate the aggregate prefix if at least one of the components of the aggregate is learned via BGP. - This implies that two ALT routers that share an overlapping set of + An ALT Router must not generate an aggregate that includes a non- + LISP-speaking hole unless it can be configured to return a Negative + Map-Reply with action="Natively-Forward" (see [LISP]) if it receives + an ALT Datagram that matches that hole. If it receives an ALT + Datagram that matches a LISP-speaking hole that is currently not + reachable, it should return a Negative Map-Reply with action="drop". + Negative Map-Replies should be returned with a short TTL, as + specified in [LISP-MS]. Note that an off-the-shelf, non-LISP- + speaking router configured as an aggregating ALT Router cannot send + Negative Map-Replies, so such a router must never originate an + aggregate that includes a non-LISP-speaking hole. + + This implies that two ALT Routers that share an overlapping set of prefixes must exchange those prefixes if either is to generate and export a covering aggregate for those prefixes. It also implies that an ETR which connects to the ALT using BGP must maintain BGP sessions - with all of the ALT routers that are configured to originate an - aggregate which covers that prefix. See also [LISP-MS] for an + with all of the ALT Routers that are configured to originate an + aggregate which covers that prefix and that each of those ALT Routers + must be explicitly configured to know the set of EID-prefixes that + make up any aggregate that it originates. See also [LISP-MS] for an example of other ways that prefix origin consistency and aggregation - are maintained. + can be maintained. + + As an example, consider ETRs that are originating EID-prefixes for + 10.1.0.0/24, 10.1.64.0/24, 10.1.128.0/24, and 10.1.192.0/24. An ALT + Router should only be configured to generate an aggregate for + 10.1.0.0/16 if it has BGP sessions configured with all of these ETRs, + in other words, only if it has sufficient knowledge about the state + of those prefixes to summarize them. If the Router originating + 10.1.0.0/16 receives an ALT Datagram destined for 10.1.77.88, a non- + LISP destination covered by the aggregate, it returns a Negative Map- + Reply with action "Natively-Forward". If it receives an ALT Datagram + destined for 10.1.128.199 but the configured LISP prefix + 10.1.128.0/24 is unreachable, it returns a Negative Map-Reply with + action "drop". Note: much is currently uncertain about the best way to build the ALT network; as testing and prototype deployment proceeds, a guide to how to best build the ALT network will be developed. -5.3. LISP+ALT Router (or ALT router for short) - - A LISP+ALT Router has the following functionality: - - 1. It runs, at a minimum, the eBGP part of the BGP protocol. - - 2. It supports a separate RIB which uses next-hop GRE tunnel - interfaces for forwarding ALT datagrams. - - 3. It can act as a "proxy-ITR" to support non-LISP sites. - - 4. It can act as an ETR, or as a recursive or re-encapsulating ITR - to reduce mapping tables in site-based LISP routers. - -5.4. ITR and ETR in a LISP+ALT Environment - - An ITR using LISP+ALT may have additional functionality as follows: - - 1. If it is also acting as a LISP+ALT Router, it sends ALT datagrams - on the BGP best path computed GRE tunnel for each EID prefix. - - 2. When acting solely as a ITR, it sends ALT datagrams directly to a - configured LISP+ALT router. - - An ETR using LISP+ALT may also behave slightly differently: - - 1. If it is also acting as a LISP+ALT router, it advertises its - configured EID-prefixes into BGP for distribution through the - ALT. - - 2. It receives ALT datagrams only from its "upstream" LISP+ALT - routers over the GRE tunnel(s) configured to it/them. It - responds with Map-Replies for the EID prefixes that it "owns". - -5.5. Use of GRE and BGP between LISP+ALT Routers +4.3. Use of GRE and BGP between LISP+ALT Routers - The ALT network is built using GRE tunnels between LISP+ALT routers. - eBGP sessions are configured over those tunnels, with each LISP+ALT - router acting as a separate AS "hop" in a Path Vector for BGP. For - the purposes of LISP+ALT, the AS-path is used solely as a shortest- - path determination and loop-avoidance mechanism. Because all next- - hops are on tunnel interfaces, no IGP is required to resolve those - next-hops to exit interfaces. + The ALT network is built using GRE tunnels between ALT Routers. BGP + sessions are configured over those tunnels, with each ALT Router + acting as a separate AS "hop" in a Path Vector for BGP. For the + purposes of LISP+ALT, the AS-path is used solely as a shortest-path + determination and loop-avoidance mechanism. Because all next-hops + are on tunnel interfaces, no IGP is required to resolve those next- + hops to exit interfaces. - LISP+ALT's use of GRE and BGP reduces provider Operational Expense - (OPEX) because no new protocols need to be either defined or used on - the overlay topology. Also, since tunnel IP addresses are local in - scope, no coordination is needed for their assignment; any addressing - scheme (including private addressing) can be used for tunnel - addressing. + LISP+ALT's use of GRE and BGP facilities deployment and operation of + LISP because no new protocols need to be defined, implemented, or + used on the overlay topology; existing BGP/GRE tools and operational + expertise are also re-used. Tunnel address assignment is also easy: + since the addresses on an ALT tunnel are only used by the pair of + routers connected to the tunnel, the only requirement of the IP + addresses used to establish that tunnel is that the attached routers + be reachable by each other; any addressing plan, including private + addressing, can therefore be used for ALT tunnels. -6. EID Prefix Propagation and Map-Request Forwarding +5. EID-prefix Propagation and Map-Request Forwarding - As described in Section 9.2, an ITR may send either a Map-Request or - a data probe to find a given EID-to-RLOC mapping. The ALT provides - the infrastructure that allows these requests to reach the - authoritative ETR. + As described in Section 8.2, an ITR sends an ALT Datagram to a given + EID-to-RLOC mapping. The ALT provides the infrastructure that allows + these requests to reach the authoritative ETR. - Note that, under normal circumstances, Map-Replies are not sent over + Note that under normal circumstances Map-Replies are not sent over the ALT - an ETR sends a Map-Reply to the source RLOC learned from the original Map-Request. There may be scenarios, perhaps to - encourage caching of EID-to-RLOC mappings by ALT routers, where Map- + encourage caching of EID-to-RLOC mappings by ALT Routers, where Map- Replies could be sent over the ALT or where a "first-hop" ALT router might modify the originating RLOC on a Map-Request received from an - ITR to force the Map-Reply to be sent to it; these cases will not be - supported by initial LISP+ALT implementations but may be subject to - future experimentation. + ITR to force the Map-Reply to be returned to the "first-hop" ALT + Router. These cases will not be supported by initial LISP+ALT + implementations but may be subject to future experimentation. - LISP+ALT routers propagate mapping information for use by ITRs (when - sending ALT datagrams) using eBGP [RFC4271]. eBGP is run on the - inter-LISP+ALT router links, and possibly between an edge ("last - hop") LISP+ALT router and an ETR or between an edge ("first hop") - LISP+ALT router and an ITR. The ALT eBGP RIB consists of aggregated - EID prefixes and their next hops toward the authoritative ETR for - that EID prefix. + ALT Routers propagate path information via BGP ([RFC4271]) that is + used by ITRs to send ALT Datagrams toward the appropriate ETR for + each EID-prefix. BGP is run on the inter-ALT Router links, and + possibly between an edge ("last hop") ALT Router and an ETR or + between an edge ("first hop") ALT Router and an ITR. The ALT BGP RIB + consists of aggregated EID-prefixes and their next hops toward the + authoritative ETR for that EID-prefix. -6.1. Changes to ITR behavior with LISP+ALT +5.1. Changes to ITR behavior with LISP+ALT - When using LISP+ALT, an ITR sends ALT datagrams to one of its - "upstream" LISP+ALT routers; these are sent only to obtain new EID- - to-RLOC mappings - RLOC probe and cache TTL refresh Map-Requests are - not sent on the ALT. As in basic LISP, it should use one of its - RLOCs as the source address of these queries; it should explicitly - not use a tunnel interface as the source address as doing so will - cause replies to be forwarded over the tunneled topology and may be - problematic if the tunnel interface address is not explicitly routed + As previously described, an ITR will usually use the Map Resolver + interface and will send its Map Requests to a Map Resolver. When an + ITR instead connects via tunnels and BGP to the ALT, it sends ALT + Datagrams to one of its "upstream" ALT Routers; these are sent only + to obtain new EID-to-RLOC mappings - RLOC probe and cache TTL refresh + Map-Requests are not sent on the ALT. As in basic LISP, it should + use one of its RLOCs as the source address of these queries; it + should not use a tunnel interface as the source address as doing so + will cause replies to be forwarded over the tunneled topology and may + be problematic if the tunnel interface address is not routed throughout the ALT. If the ITR is running BGP with the LISP+ALT - router(s), it selects the appropriate LISP+ALT router based on the - BGP information received. If it is not running BGP, it uses static - configuration to select a LISP+ALT router; in the general case, this - will effectively be an "EID-prefix default route". + router(s), it selects the appropriate ALT Router based on the BGP + information received. If it is not running BGP, it uses a + statically-configued ALT Default Route to select an ALT Router. -6.2. Changes to ETR behavior with LISP+ALT +5.2. Changes to ETR behavior with LISP+ALT - If an ETR connects using BGP to one or more LISP+ALT router(s), it - simply announces its EID-prefix to those LISP+ALT routers. Note that - when an ETR generates a Map-Reply message to return to a querying - ITR, it sends it to the ITR's source-RLOC (i.e., on the underlying - Internet topology, not on the ALT; this avoids any latency penalty - (or "stretch") that might be incurred by routing over the ALT). + As previously described, an ETR will usually use the Map Server + interface (see [LISP-MS]) and will register its EID-prefixes with its + configured Map Servers. When an ETR instead connects using BGP to + one or more ALT Routers, it announces its EID-prefix(es) to those ALT + Routers. Note that when an ETR generates a Map-Reply message to + return to a querying ITR, it sends it to the ITR's source-RLOC (i.e., + on the underlying Internet topology, not on the ALT; this avoids any + latency penalty (or "stretch") that might be incurred by routing over + the ALT). -7. BGP configuration and protocol considerations +6. BGP configuration and protocol considerations -7.1. Autonomous System Numbers (ASNs) in LISP+ALT +6.1. Autonomous System Numbers (ASNs) in LISP+ALT The primary use of BGP today is to define the global Internet routing topology in terms of its participants, known as Autonomous Systems. - LISP+ALT specifies the use of BGP to create a global EID-to-RLOC - mapping database which, while related to the global routing database, - serves a very different purpose and is organized into a very - different hierarchy. Because LISP+ALT does use BGP, however, it uses - ASNs in the paths that are propagated among LISP+ALT routers. To - avoid confusion, it needs to be stressed that that these LISP+ALT - ASNs use a new numbering space that is unrelated to the ASNs used by - the global routing system. Exactly how this new space will be - assigned and managed will be determined during experimental + LISP+ALT specifies the use of BGP to create a global overlay network + (the ALT) for finding EID-to-RLOC mappings. While related to the + global routing database, the ALT serves a very different purpose and + is organized into a very different hierarchy. Because LISP+ALT does + use BGP, however, it uses ASNs in the paths that are propagated among + ALT Routers. To avoid confusion, it needs to be stressed that that + these LISP+ALT ASNs use a new numbering space that is unrelated to + the ASNs used by the global routing system. Exactly how this new + space will be assigned and managed will be determined during the deployment of LISP+ALT. - Note that the LISP+ALT routers that make up the "core" of the ALT - will not be associated with any existing core-Internet ASN because - topology, hierarchy, and aggregation boundaries are completely - separate from and independent of the global Internet routing system. + Note that the ALT Routers that make up the "core" of the ALT will not + be associated with any existing core-Internet ASN because the ALT + topology is completely separate from, and independent of, the global + Internet routing system. -7.2. Sub-Address Family Identifier (SAFI) for LISP+ALT +6.2. Sub-Address Family Identifier (SAFI) for LISP+ALT As defined by this document, LISP+ALT may be implemented using BGP without modification. Given the fundamental operational difference - between propagating global Internet routing information (the current, - dominant use of BGP) and managing the global EID-to-RLOC database - (the use of BGP proposed by this document), it may be desirable to - assign a new SAFI [RFC2858] to prevent operational confusion and - difficulties, including the inadvertent leaking of information from - one domain to the other. At present, this document does not require - the assignment of a new SAFI but the authors anticipate that - experimentation may suggest the need for one in the future. + between propagating global Internet routing information (the current + dominant use of BGP) and creating an overlay network for finding EID- + to-RLOC mappings (the use of BGP proposed by this document), it may + be desirable to assign a new SAFI [RFC4760] to prevent operational + confusion and difficulties, including the inadvertent leaking of + information from one domain to the other. Use of a separate SAFI + would make it easier to debug many operational problems but would + come at a significant cost: unmodified, off-the-shelf routers which + do not understand the new SAFI could not be used to build any part of + the ALT network. At present, this document does not request the + assignment of a new SAFI; additional experimentation may suggest the + need for one in the future. -8. EID-Prefix Aggregation +7. EID-prefix Aggregation The ALT BGP peering topology should be arranged in a tree-like fashion (with some meshiness), with redundancy to deal with node and link failures. A basic assumption is that as long as the routers are - up and running, the underlying topology will provide alternative - routes to maintain BGP connectivity among LISP+ALT routers. + up and running, the underlying Internet will provide alternative + routes to maintain BGP connectivity among ALT Routers. - Note that, as mentioned in Section 5.2, the use of BGP by LISP+ALT - requires that information can only be aggregated where all active - more-specific prefixes of a generated aggregate prefix are known. - This implies, for example, that if a given set of prefixes is used by - multiple, ALT networks, those networks must interconnect and share - information about all of the prefixes if either were to generate an - aggregate prefix that covered all of them. This is no different than - the way that BGP route aggregation works in the existing global - routing system: a service provider only generates an aggregate route - if it is configured to learn to all prefixes that make up that - aggregate. + Note that, as mentioned in Section 4.2, the use of BGP by LISP+ALT + requires that information only be aggregated where all active more- + specific prefixes of a generated aggregate prefix are known. This is + no different than the way that BGP route aggregation works in the + existing global routing system: a service provider only generates an + aggregate route if it is configured to learn to all prefixes that + make up that aggregate. -8.1. Traffic engineering with LISP and LISP+ALT +7.1. Stability of the ALT It is worth noting that LISP+ALT does not directly propagate EID-to- - RLOC mappings. What it does is provide a mechanism for a LISP ITR to - find the ETR that holds the mapping for a particular EID prefix. - This distinction is important for several reasons. First, it means - that the reachability of RLOCs is learned through the LISP ITR-ETR - exchange so "flapping" of state information through BGP is not likely - nor can mapping information become "stale" by slow propagation - through the ALT BGP mesh. Second, by deferring EID-to-RLOC mapping - to an ITR-ETR exchange, it is possible to perform site-to-site - traffic engineering through a combination of setting the preference - and weight fields and by returning more-specific EID-to-RLOC - information in LISP Map-Reply messages. This is a powerful mechanism - that can conceivably replace the traditional practice of routing - prefix deaggregation for traffic engineering purposes. Rather than - propagating more-specific information into the global routing system - for local- or regional-optimization of traffic flows, such more- - specific information can be exchanged, through LISP (not LISP+ALT), - on an as-needed basis between only those ITRs/ETRs (and, thus, site - pairs) that need it; should a receiving ITR decide that it does not - wish to store such more-specific information, it has the option of - discarding it as long as a shorter, covering EID prefix exists. Not - only does this greatly improve the scalability of the global routing - system but it also allows improved traffic engineering techniques by - allowing richer and more fine-grained policies to be applied. + RLOC mappings. What it does is provide a mechanism for an ITR to + commonicate with the ETR that holds the mapping for a particular EID- + prefix. This distinction is important when considering the stability + of BGP on the ALT network as compared to the global routing system. + It also has implications for how site-specific EID-prefix information + may be used by LISP but not propagated by LISP+ALT (see Section 7.2 + below). -8.2. Edge aggregation and dampening + RLOC prefixes are not propagated through the ALT so their + reachability is not determined through use of LISP+ALT. Instead, + reachability of RLOCs is learned through the LISP ITR-ETR exchange. + This means that link failures or other service disruptions that may + cause the reachability of an RLOC to change are not known to the ALT. + Changes to the presence of an EID-prefix on the ALT occur much less + frequently: only at subscription time or in the event of a failure of + the ALT infrastructure itself. This means that "flapping" (frequent + BGP updates and withdrawals due to prefix state changes) is not + likely and mapping information cannot become "stale" due to slow + propagation through the ALT BGP mesh. - Note also that normal BGP best common practices apply to the ALT - network. In particular, first-hop ALT routers will aggregate EID - prefixes and dampen changes to them in the face of excessive updates. - Since EID prefix assignments are not expected to change with anywhere - as frequently BGP prefix reachability on the Internet, such dampening - should be very rare and might be worthy of logging as an exceptional - event. It is again worth noting that the ALT carries only EID - prefixes, along with BGP-generated paths to the ETRs that source - those prefixes as advertisements travel over the logical topology; - this set of information is considerablly less volatile than the - actual EID-to-RLOC mappings. +7.2. Traffic engineering using LISP -9. Connecting sites to the ALT network + Since an ITR learns an EID-to-RLOC mapping directly from the ETR that + owns it, it is possible to perform site-to-site traffic engineering + by setting the preference and/or weight fields, and by including + more-specific EID-to-RLOC information in Map-Reply messages. -9.1. ETRs originating information into the ALT + This is a powerful mechanism that can conceivably replace the + traditional practice of routing prefix deaggregation for traffic + engineering purposes. Rather than propagating more-specific + information into the global routing system for local- or regional- + optimization of traffic flows, such more-specific information can be + exchanged, through LISP (not LISP+ALT), on an as-needed basis between + only those ITRs/ETRs (and, thus, site pairs) that need it. Should a + receiving ITR decide that it does not wish to store such more- + specific information, it has the option of discarding it as long as a + shorter, covering EID-prefix exists. Such an exchange of "more- + specifics" between sites facilitates traffic engineering, by allowing + richer and more fine-grained policies to be applied without + advertising additional prefixes into either the ALT or the global + routing system. - EID prefix information is originated into the ALT by two different + Note that these new traffic engineering capabilities are an attribute + of LISP and are not specific to LISP+ALT; discussion is included here + because the BGP-based global routing system has traditionally used + propagation of more-specific routes as a crude form of traffic + engineering. + +7.3. Edge aggregation and dampening + + Normal BGP best common practices apply to the ALT network. In + particular, first-hop ALT Routers will aggregate EID prefixes and + dampen changes to them in the face of excessive updates. Since EID- + prefix assignments are not expected to change as frequently as global + routing BGP prefix reachability, such dampening should be very rare, + and might be worthy of logging as an exceptional event. It is again + worth noting that the ALT carries only EID-prefixes, used to + construct BGP paths to their owning ETRs; it does not carry + reachability about RLOCs. In addition, EID-prefix information may be + aggregated as the topology and address assignment hierarchy allow. + Since the topology is all tunneled and can be modified as needed, + reasonably good aggregation should be possible. In addition, since + most ETRs are expected to connect to the ALT using the Map Server + interface, Map Servers will implement a natural "edge" for the ALT + where dampening and aggregation can be applied. For these reasons, + the set of prefix information on the ALT can be expected to be both + better aggregated and considerably less volatile than the actual EID- + to-RLOC mappings. + +7.4. EID assignment flexibility vs. ALT scaling + + There are major open questions regarding how the ALT will be deployed + and what organization(s) will operate it. In a simple, non- + distributed world, centralized administration of EID prefix + assignment and ALT network design would facilitate a well- aggregated + ALT routing system. Business and other realities will likely result + in a more complex, distributed system involving multiple levels of + prefix delegation, multiple operators of parts of the ALT + infrastructure, and a combination of competition and cooperation + among the participants. In addition, re-use of existing IP address + assignments, both "PI" and "PA", to avoid renumbering when sites + transition to LISP will further complicate the processes of building + and operating the ALT. + + A number of conflicting considerations need to be kept in mind when + designing and building the ALT. Among them are: + + 1. Target ALT routing state size and level of aggregation. As + described in Section 7.1, the ALT should not suffer from some of + the performance constraints or stability issues as the Internet + global routing system, so some reasonable level of deaggregation + and increased number of EID prefixes beyond what might be + considered ideal should be acceptable. That said, measures, such + as tunnel rehoming to preserve aggregation when sites move from + one mapping provider to another and implementing aggregation at + multiple levels in the hierarchy to collapse de-aggregation at + lower levels, should be taken to reduce unnecessary explosion of + ALT routing state. + + 2. Number of operators of parts of the ALT and how they will be + organized (hierarchical delegation vs. shared administration). + This will determine not only how EID prefixes are assigned but + also how tunnels are configured and how EID prefixes can be + aggregated between different parts of the ALT. + + 3. Number of connections between different parts of the ALT. Trade- + offs will need to be made among resilience, performance, and + placement of aggregation boundaries. + + 4. EID prefix portability between competing operators of the ALT + infrastructure. A significant benefit for an end-site to adopt + LISP is the availability of EID space that is not tied to a + specific connectivity provider; it is important to ensure that an + end site doesn't trade lock-in to a connectivity provider for + lock-in to a provider of its EID assignment, ALT connectivity, or + Map Server facilities. + + This is, by no means, and exhaustive list. + + While resolving these issues is beyond the scope of this document, + the authors recommend that existing distributed resource structures, + such as the IANA/Regional Internet Registries and the ICANN/Domain + Registrar, be carefully considered when designing and deploying the + ALT infrastructure. + +8. Connecting sites to the ALT network + +8.1. ETRs originating information into the ALT + + EID-prefix information is originated into the ALT by three different mechanisms: - eBGP: An ETR usually participates in the LISP+ALT overlay network by - running eBGP to one or more LISP+ALT router(s) over tunnel(s). - The ETR advertises reachability for its EID prefixes over these - eBGP connection(s). The LISP+ALT router(s) that receive(s) these - prefixes then propagate(s) them into the ALT. Here the ETR is - simply an eBGP peer of LISP+ALT router(s) at the edge of the ALT. - Where possible, a LISP+ALT router that receives EID prefixes from - an ETR via eBGP should aggregate that information. + Map Server: In most cases, a site will configure its ETR(s) to + register with one or more Map Servers (see [LISP-MS]), and does + not participate directly in the ALT. - Configuration: One or more LISP+ALT router(s) may be configured to - originate an EID prefix on behalf of the non-BGP-speaking ETR that + BGP: For a site requiring complex control over their EID-prefix + origination into the ALT, an ETR may connect to the LISP+ALT + overlay network by running BGP to one or more ALT Router(s) over + tunnel(s). The ETR advertises reachability for its EID-prefixes + over these BGP connection(s). The edge ALT Router(s) that + receive(s) these prefixes then propagate(s) them into the ALT. + Here the ETR is simply an BGP peer of ALT Router(s) at the edge of + the ALT. Where possible, an ALT Router that receives EID-prefixes + from an ETR via BGP should aggregate that information. + + Configuration: One or more ALT Router(s) may be configured to + originate an EID-prefix on behalf of the non-BGP-speaking ETR that is authoritative for a prefix. As in the case above, the ETR is - connected to LISP+ALT router(s) using GRE tunnel(s) but rather - than BGP being used, the LISP+ALT router(s) are configured with - what are in effect "static routes" for the EID prefixes "owned" by - the ETR. The GRE tunnel is used to route Map-Requests to the ETR. - Note that the LISP+ALT router could also serve as a proxy for its - TCP-connected ETRs. + connected to ALT Router(s) using GRE tunnel(s) but rather than BGP + being used, the ALT Router(s) are configured with what are in + effect "static routes" for the EID-prefixes "owned" by the ETR. + The GRE tunnel is used to route Map-Requests to the ETR. - Note: in both cases, an ETR may have connections to to multiple - LISP+ALT routers for the following reasons: + Note: in all cases, an ETR may register to multiple Map Servers or + connect to multiple ALT Routers for the following reasons: - * redundancy, so that a particular ETR is still reachable through - the ALT even if one path or tunnel is unavailable. + * redundancy, so that a particular ETR is still reachable even if + one path or tunnel is unavailable. * to connect to different parts of the ALT hierarchy if the ETR - "owns" multiple EID-to-RLOC mappings for EID prefixes that - cannot be aggregated by the same LISP+ALT router (i.e. are not + "owns" multiple EID-to-RLOC mappings for EID-prefixes that + cannot be aggregated by the same ALT Router (i.e. are not topologically "close" to each other in the ALT). -9.2. ITRs Using the ALT - - In order to source Map-Requests to the ALT or to route a Data Probe - packet over the ALT, each ITR participating in the ALT establishes a - connection to one or more LISP+ALT routers. These connections can be - either eBGP or TCP (as described above). +8.2. ITRs Using the ALT - In the case in which the ITR is running eBGP, the peer LISP+ALT - routers use these connections to advertise highly aggregated EID- - prefixes to the peer ITRs. The ITR then installs the received - prefixes into a forwarding table that is used to to send LISP Map- - Requests to the appropriate LISP+ALT router. In most cases, a LISP+ - ALT router will send a default mapping to its client ITRs so that - they can send request for any EID prefix into the ALT. + In the common configuration, an ITR does not need to know anything + about the ALT, since it sends Map-Requests to one of its configured + Map-Resolvers (see [LISP-MS]). There are two exceptional cases: - In the case in which the ITR is connected to some set of LISP+ALT - routers without eBGP, the ITR sends Map-Requests to any of its - connected LISP+ALT routers. + Static default: If a Map Resolver is not available but an ITR is + adjacent to an ALT Router (either over a common subnet or through + the use of a tunnel), it can use an ALT Default Route route to + cause all ALT Datagrams to be sent that ALT Router. This case is + expected to be rare. - An ITR may also choose to send the first few data packets over the - ALT to minimize packet loss and reduce mapping latency. In this - case, the data packet serves as a mapping probe (Data Probe) and the - ETR which receives the data packet (over the ALT) responds with a - Map-Reply is sent to the ITR's source-RLOC using the underlying - topology. Note that the use of Data Probes is discouraged at this - time (see Section 4.3). + Connection to ALT: A site with complex Internet connectivity needs + may need more fine-grained distinction between traffic to LISP- + capable and non-LISP-capable sites. Such a site may configure + each of its ITRs to connect directly to the ALT, using a tunnel + and BGP connection. In this case, the ITR will receive EID-prefix + routes from its BGP connection to the ALT Router and will LISP- + encapsulate and send ALT Datagrams through the tunnel to the ALT + Router. Traffic to other destinations may be forwarded (without + LISP encapsulation) to non-LISP next-hop routers that the ITR + knows. - In general, an ITR will establish connections only to LISP+ALT - routers at the "edge" of the ALT (typically two for redundancy) but - there may also be situations where an ITR would connect to other - LISP+ALT routers to receive additional, shorter path information + In general, an ITR that connects to the ALT does so only to to ALT + Routers at the "edge" of the ALT (typically two for redundancy). + There may, though, be situations where an ITR would connect to + other ALT Routers to receive additional, shorter path information about a portion of the ALT of interest to it. This can be - accomplished by establishing GRE tunnels between the ITR and the set - of LISP+ALT routers with the additional information. This is a - purely local policy issue between the ITR and the LISP+ALT routers in + accomplished by establishing GRE tunnels between the ITR and the + set of ALT Routers with the additional information. This is a + purely local policy issue between the ITR and the ALT Routers in question. -10. IANA Considerations + As described in [LISP-MS], Map-Resolvers do not accept or forward + Data Probes; in the rare scenario that an ITR does support and + originate Data Probes, it must do so using one of the exceptional + configurations described above. Note that the use of Data Probes is + discouraged at this time (see Section 3.3). + +9. IANA Considerations This document makes no request of the IANA. -11. Security Considerations +10. Security Considerations LISP+ALT shares many of the security characteristics of BGP. Its security mechanisms are comprised of existing technologies in wide - operational use today. Securing LISP+ALT is much simpler than - securing BGP. - - Compared to BGP, LISP+ALT routers are not topologically bound, - allowing them to be put in locations away from the vulnerable AS - border (unlike eBGP speakers). + operational use today, so securing the ALT should be mostly a matter + of applying the same technology that is used to secure the BGP-based + global routing system (see Section 10.3 below). -11.1. Apparent LISP+ALT Vulnerabilities +10.1. Apparent LISP+ALT Vulnerabilities - This section briefly lists of the apparent vulnerabilities of LISP+ - ALT. + This section briefly lists the known potential vulnerabilities of + LISP+ALT. Mapping Integrity: Can an attacker insert bogus mappings to black- - hole (create a DoS) or intercept LISP data-plane packets? + hole (create Denial-of-Service, or DoS attack) or intercept LISP + data-plane packets? - LISP+ALT router Availability: Can an attacker DoS the LISP+ALT - routers connected to a given ETR? without access to its mappings, - a site is essentially unavailable. + ALT Router Availability: Can an attacker DoS the ALT Routers + connected to a given ETR? If a site's ETR cannot advertise its + EID-to-RLOC mappings, the site is essentially unavailable. - ITR Mapping/Resources: Can an attacker force an ITR or LISP+ALT - router to drop legitimate mapping requests by flooding it with - random destinations that it will have to query for. Further study - is required to see the impact of admission control on the overlay - network. + ITR Mapping/Resources: Can an attacker force an ITR or ALT Router to + drop legitimate mapping requests by flooding it with random + destinations for which it will generate large numbers of Map- + Requests and fill its mapping cache? Further study is required to + see the impact of admission control on the overlay network. EID Map-Request Exploits for Reconnaissance: Can an attacker learn - about a LISP destination sites' TE policy by sending legitimate - mapping requests messages and then observing the RLOC mapping - replies? Is this information useful in attacking or subverting - peer relationships? Note that LISP 1.0 has a similar data-plane - reconnaissance issue. + about a LISP site's TE policy by sending legitimate mapping + requests and then observing the RLOC mapping replies? Is this + information useful in attacking or subverting peer relationships? + Note that any public LISP mapping database will have similar data- + plane reconnaissance issue. - Scaling of LISP+ALT router Resources: Paths through the ALT may be - of lesser bandwidth than more "direct" paths; this may make them - more prone to high-volume denial-of-service attacks. For this - reason, all components of the ALT (ETRs and ALT routers) should be - prepared to rate-limit traffic (ALT datagrams) that could be + Scaling of ALT Router Resources: Paths through the ALT may be of + lesser bandwidth than more "direct" paths; this may make them more + prone to high-volume denial-of-service attacks. For this reason, + all components of the ALT (ETRs and ALT Routers) should be + prepared to rate-limit traffic (ALT Datagrams) that could be received across the ALT. - UDP Map-Reply from ETR: Since Map-Replies packets are sent directly - from the ETR to the ITR's RLOC, the ITR's RLOC may be vulnerable - to various types of DoS attacks. + UDP Map-Reply from ETR: Since Map-Replies are sent directly from the + ETR to the ITR's RLOC, the ITR's RLOC may be vulnerable to various + types of DoS attacks (this is a general property of LISP, not an + LISP+ALT vulnerability). -11.2. Survey of LISP+ALT Security Mechanisms + More-specific prefix leakage: Because EID-prefixes on the ALT are + expected to be fairly well-aggregated and EID-prefixes propagated + out to the global Internet (see [LISP-IW] much more so, accidental + leaking or malicious advertisement of an EID-prefix into the + global routing system could cause traffic redirection away from a + LISP site. This is not really a new problem, though, and its + solution can only be achieved by much more strict prefix filtering + and authentication on the global routing system. + +10.2. Survey of LISP+ALT Security Mechanisms Explicit peering: The devices themselves can both prioritize - incoming packets as well as potentially do key checks in hardware + incoming packets, as well as potentially do key checks in hardware to protect the control plane. Use of TCP to connect elements: This makes it difficult for third parties to inject packets. - Use of HMAC Protected TCP Connections: HMAC is used to verify + Use of HMAC Protected BGP/TCP Connections: HMAC is used to verify message integrity and authenticity, making it nearly impossible for third party devices to either insert or modify messages. Message Sequence Numbers and Nonce Values in Messages: This allows - for devices to verify that the mapping-reply packet was in - response to the mapping-request that they sent. + an ITR to verify that the Map-Reply from an ETR is in response to + a Map-Request originated by that ITR (this is a general property + of LISP; LISP+ALT does not change this behavior). -11.3. Using existing BGP Security mechanisms +10.3. Use of new IETF standard BGP Security mechanisms - LISP+ALT's use of BGP allows for the ALT to take advantage of BGP + LISP+ALT's use of BGP allows the ALT to take advantage of BGP security features designed for existing Internet BGP use. - For example, should either sBGP [I-D.murphy-bgp-secr] or soBGP + For example, should either S-BGP [I-D.murphy-bgp-secr] or soBGP [I-D.white-sobgparchitecture] become widely deployed it expected that LISP+ALT could use these mechanisms to provide authentication of EID- to-RLOC mappings, and EID origination. -12. Acknowledgments +11. Acknowledgments - Many of the ideas described in this document were developed during - detailed discussions with Scott Brim and Darrel Lewis, who made many - insightful comments on earlier versions of this document. Additional - thanks are due to Hannu Flinck and Amit Jain who offered many helpful - suggestions for the -02 version. + The authors would like to specially thank J. Noel Chiappa who was a + key contributer to the design of the LISP-CONS mapping database (many + ideas from which made their way into LISP+ALT) and who has continued + to provide invaluable insight as the LISP effort has evolved. Others + who have provided valuable contributions include John Zwiebel, Hannu + Flinck, Amit Jain, John Scudder, and Scott Brim. -13. References +12. References -13.1. Normative References +12.1. Normative References - [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate - Requirement Levels", BCP 14, RFC 2119, March 1997. + [LISP] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, + "Locator/ID Separation Protocol (LISP)", + draft-ietf-lisp-06.txt (work in progress), January 2010. + + [LISP-MS] Fuller, V. and D. Farinacci, "LISP Map Server", + draft-ietf-lisp-ms-04.txt (work in progress), + October 2009. [RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P. Traina, "Generic Routing Encapsulation (GRE)", RFC 2784, March 2000. - [RFC2858] Bates, T., Rekhter, Y., Chandra, R., and D. Katz, - "Multiprotocol Extensions for BGP-4", RFC 2858, June 2000. - [RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway Protocol 4 (BGP-4)", RFC 4271, January 2006. [RFC4632] Fuller, V. and T. Li, "Classless Inter-domain Routing (CIDR): The Internet Address Assignment and Aggregation Plan", BCP 122, RFC 4632, August 2006. -13.2. Informative References + [RFC4760] Bates, T., Chandra, R., Katz, D., and Y. Rekhter, + "Multiprotocol Extensions for BGP-4", RFC 4760, + January 2007. + +12.2. Informative References [I-D.murphy-bgp-secr] Murphy, S., "BGP Security Analysis", draft-murphy-bgp-secr-04 (work in progress), November 2001. [I-D.white-sobgparchitecture] White, R., "Architecture and Deployment Considerations for Secure Origin BGP (soBGP)", draft-white-sobgparchitecture-00 (work in progress), May 2004. - [Interworking] - Lewis, D., Meyer, D., Farinacci, D., and V. Fuller, + [LISP-IW] Lewis, D., Meyer, D., Farinacci, D., and V. Fuller, "Interworking LISP with IPv4 and ipv6", - draft-ietf-lisp-interworking-01.txt (work in progress), - January 2010. - - [LISP] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, - "Locator/ID Separation Protocol (LISP)", - draft-ietf-lisp-06.txt (work in progress), January 2010. - - [LISP-MS] Fuller, V. and D. Farinacci, "LISP Map Server", - draft-ietf-lisp-ms-04.txt (work in progress), - October 2009. + draft-ietf-lisp-interworking-02.txt (work in progress), + February 2010. Authors' Addresses Vince Fuller Cisco Tasman Drive San Jose, CA 95134 USA Email: vaf@cisco.com