Network Working Group M. Lepinski, Ed. Internet-Draft BBN Intended status: Standards Track October 31, 2011 Expires: May 3, 2012 BGPSEC Protocol Specification draft-ietf-sidr-bgpsec-protocol-01 Abstract This document describes BGPSEC, an extension to the Border Gateway Protocol (BGP) that provides security for the AS-PATH attribute in BGP update messages. BGPSEC is implemented via a new optional non- transitive BGP path attribute that carries a digital signature produced by each autonomous system on the AS-PATH. Requirements Language 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 RFC 2119 [4]. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on May 3, 2012. Copyright Notice Copyright (c) 2011 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of Lepinski Expires May 3, 2012 [Page 1] Internet-Draft BGPSEC Protocol October 2011 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 Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. BGPSEC Negotiation . . . . . . . . . . . . . . . . . . . . . . 3 3. The BGPSEC_Path_Signatures Attribute . . . . . . . . . . . . . 5 4. Generating a BGPSEC Update . . . . . . . . . . . . . . . . . . 7 4.1. Originating a New BGPSEC Update . . . . . . . . . . . . . 8 4.2. Propagating a Route Advertisement . . . . . . . . . . . . 11 4.2.1. Propogating an Update without the Path_Signatures attribute . . . . . . . . . . . . . . . . . . . . . . 14 5. Processing a Received BGPSEC Update . . . . . . . . . . . . . 15 5.1. Validation Algorithm . . . . . . . . . . . . . . . . . . . 17 6. Algorithms and Extensibility . . . . . . . . . . . . . . . . . 21 6.1. Algorithm Suite Considerations . . . . . . . . . . . . . . 21 6.2. Extensibility Considerations . . . . . . . . . . . . . . . 21 7. Security Considerations . . . . . . . . . . . . . . . . . . . 22 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25 9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 26 9.1. Authors . . . . . . . . . . . . . . . . . . . . . . . . . 26 9.2. Acknowledgements . . . . . . . . . . . . . . . . . . . . . 27 10. Normative References . . . . . . . . . . . . . . . . . . . . . 27 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 28 Lepinski Expires May 3, 2012 [Page 2] Internet-Draft BGPSEC Protocol October 2011 1. Introduction This document describes BGPSEC, a mechanism for providing path security for Border Gateway Protocol (BGP) [1] route advertisements. That is, a BGP speaker who receives a valid BGPSEC update has cryptographic assurance that the advertised route has the following two properties: 1. The route was originated by an AS that has been explicitly authorized by the holder of the IP address prefix to originate route advertisements for that prefix. 2. Every AS listed in the AS_Path attribute of the update explicitly authorized the advertisement of the route to the subsequent AS in the AS_Path. This document specifies a new optional (non-transitive) BGP path attribute, BGPSEC_Path_Signatures. It also describes how a BGPSEC- compliant BGP speaker (referred to hereafter as a BGPSEC speaker) can generate, propagate, and validate BGP update messages containing this attribute to obtain the above assurances. BGPSEC relies on the Resource Public Key Infrastructure (RPKI) certificates that attest to the allocation of AS number and IP address resources. (For more information on the RPKI, see [7] and the documents referenced therein.) Any BGPSEC speaker who wishes to send BGP update messages to external peers (eBGP) containing the BGPSEC_Path_Signatures must have an RPKI end-entity certificate (as well as the associated private signing key) corresponding to the BGPSEC speaker's AS number. Note, however, that a BGPSEC speaker does not require such a certificate in order to validate update messages containing the BGPSEC_Path_Signatures attribute. 2. BGPSEC Negotiation This document defines a new BGP capability [3]that allows a BGP speaker to advertise to its neighbors the ability to send and/or receive BGPSEC update messages (i.e., update messages containing the BGPSEC_Path_Signatures attribute). This capability has capability code : TBD The capability length for this capability MUST be set to 3. The three octets of the capability value are specified as follows. Lepinski Expires May 3, 2012 [Page 3] Internet-Draft BGPSEC Protocol October 2011 Capability Value: 0 1 2 3 4 5 6 7 +---------------------------------------+ | Send | Receive | Reserved | Version | +---------------------------------------+ | AFI | +---------------------------------------+ | | +---------------------------------------+ The high order bit (bit 0) of the first octet is set to 1 to indicate that the sender is able to send BGPSEC update messages, and is set to zero otherwise. The next highest order bit (bit 1) of this octet is set to 1 to indicate that the sender is able to receive BGPSEC update messages, and is set to zero otherwise. The next two bits of the capability value (bits 2 and 3) are reserved for future use. The four low order bits (4, 5, 6 and 7) of the first octet indicate the version of BGPSEC for which the BGP speaker is advertising support. This document defines only BGPSEC version 0 (all four bits set to zero). Other versions of BGPSEC may be defined in future documents. A BGPSEC speaker MAY advertise support for multiple versions of BGPSEC by including multiple versions of the BGPSEC capability in its BGP OPEN message. If there does not exist at least one version of BGPSEC that is supported by both peers in a BGP session, then the use of BGPSEC has not been negotiated. (That is, in such a case, messages containing the BGPSEC_Path_Signatures MUST NOT be sent.) If version 0 is the only version of BGPSEC for which both peers (in a BGP session) advertise support, then the use of BGPSEC has been negotiated and the BGPSEC peers MUST adhere to the specification of BGPSEC provided in this document. (If there are multiple versions of BGPSEC which are supported by both peers, then the behavior of those peers is outside the scope of this document.) The second two octets contain the 16-bit Address Family Identifier (AFI) which indicates the address family for which the BGPSEC speaker is advertising support for BGPSEC. This document only specifies BGPSEC for use with two address families, IPv4 and IPv6. BGPSEC for use with other address families may be specified in future documents. Note that if the BGPSEC speaker wishes to use BGPSEC with two different address families (i.e., IPv4 and IPv6) over the same BGP session, then the speaker must include two instances of this capability (one for each address family) in the BGP OPEN message. Also note that a BGPSEC speaker SHOULD NOT advertise the capability Lepinski Expires May 3, 2012 [Page 4] Internet-Draft BGPSEC Protocol October 2011 of BGPSEC support for IPv6 unless it has also advertised support for IPv6 [2]. By indicating support for receiving BGPSEC update messages, a BGP speaker is, in particular, indicating that the following are true: o The BGP speaker understands the BGPSEC_Path_Signatures attribute (see Section 3). o The BGP speaker supports 4-byte AS numbers (see RFC 4893). Note that BGPSEC update messages can be quite large, therefore any BGPSEC speaker announcing the capability to receive BGPSEC messages SHOULD also announce support for the capability to receive BGP extended messages [5]. A BGP speaker MUST NOT send an update message containing the BGPSEC_Path_Signatures attribute within a given BGP session unless both of the following are true: o The BGP speaker indicated support for sending BGPSEC update messages in its open message. o The peer of the BGP speaker indicated support for receiving BGPSEC update messages in its open message. 3. The BGPSEC_Path_Signatures Attribute The BGPSEC_Path_Signatures attribute is a new optional (non- transitive) BGP path attribute. This document registers a new attribute type code for this attribute : TBD The BGPSEC_Path_Signatures attribute has the following structure: BGPSEC_Path_Signatures Attribute +---------------------------------------------------------+ | Expire Time (8 octets) | +---------------------------------------------------------+ | Sequence of one or two Signature-List Blocks (variable) | +---------------------------------------------------------+ Expire Time contains a binary representation of a time as an unsigned integer number of (non-leap) seconds that have elapsed since midnight Lepinski Expires May 3, 2012 [Page 5] Internet-Draft BGPSEC Protocol October 2011 UTC January 1, 1970. The Expire Time indicates the latest point in time that the route advertised in the update message can possibly be considered valid (see Section 5 for details on validity of BGPSEC update messages). The BGPSEC_Path_Signatures attribute will contain one or two Signature-List Blocks, each of which corresponds to a different algorithm suite. Each of the Signature-List Blocks will contain a signature segment for each AS in the AS Path attribute. In the most common case, the BGPSEC_Path_Signatures attribute will contain only a single Signature-List Block. However, in order to enable a transition from an old algorithm suite to a new algorithm suite, it will be necessary to include two Signature-List Blocks (one for the old algorithm suite and one for the new algorithm suite) during the transition period. Signature-List Block +---------------------------------------------+ | Algorithm Suite Identifier (1 octet) | +---------------------------------------------+ | Signature-List Block Length (2 octets) | +---------------------------------------------+ | Sequence of Signature-Segments (variable) | +---------------------------------------------+ An algorithm suite consists of a digest algorithm and a signature algorithm. This version of BGPSEC only supports signature algorithms that produce a signatures of fixed length. Future registrations of algorithm suites for BGPSEC must specify the length of signatures produced by the algorithm suite. This specification creates an IANA registry of one-octet BGPSEC algorithm suite identifiers (see Section 8). The Signature-List Block Length is the total number of octets in all Signature-Segments (i.e., the total size of the variable-length portion of the Signature-List block.) A Signature-Segment has the following structure: Lepinski Expires May 3, 2012 [Page 6] Internet-Draft BGPSEC Protocol October 2011 Signature Segments +-------------------------------------------- + | pCount (1 octet) | +---------------------------------------------+ | Subject Key Identifier Length (1 octet) | +---------------------------------------------+ | Subject Key Identifier (variable) | +---------------------------------------------+ | Signature (fixed by algorithm suite) | +---------------------------------------------+ The pCount field contains an unsigned integer indicating the number of repetitions of the associated autonomous system number that the signature covers. This field enables a BGPSEC speaker to mimic the semantics of adding multiple copies of their AS to the AS-PATH without requiring the speaker to generate multiple signatures. The Subject Key Identifier Length contains the size (in octets) of the value in the Subject Key Identifier field of the Signature- Segment. The Subject Key Identifier contains the value in the Subject Key Identifier extension of the RPKI end-entity certificate that is used to verify the signature (see Section 5 for details on validity of BGPSEC update messages). The Signature contains a digital signature that protects the NLRI, the AS_Path and the BGPSEC_Path_Signatures attribute (see Sections 4 and 5 for details on generating and verifying this signature, respectively). The length of the Signature field is a function of the algorithm suite for a given Signature-List Block. The specification for each BGPSEC algorithm suite must provide the length of signatures constructed using the given algorithm suite. 4. Generating a BGPSEC Update Sections 4.1 and 4.2 cover two cases in which a BGPSEC speaker may generate an update message containing the BGPSEC_Path_Signatures attribute. The first case is that in which the BGPSEC speaker originates a new route advertisement (Section 4.1). That is, the BGPSEC speaker is constructing an update message in which the only AS to appear in the AS Path attribute is the speaker's own AS (normally appears once but may appear multiple times if AS prepending is applied). The second case is that in which the BGPSEC speaker receives a route advertisement from a peer and then decides to propagate the route advertisement to an external (eBGP) peer (Section 4.2). That is, the BGPSEC speaker has received a BGPSEC update Lepinski Expires May 3, 2012 [Page 7] Internet-Draft BGPSEC Protocol October 2011 message and is constructing a new update message for the same NLRI in which the AS Path attribute will contain AS number(s) other than the speaker's own AS. In the remaining case where the BGPSEC speaker is sending the update message to an internal (iBGP) peer, the BGPSEC speaker populates the BGPSEC_Path_Signatures attribute by copying the BGPSEC_Path_Signatures attribute from the received update message. That is, the BGPSEC_Path_Signatures attribute is copied verbatim. Note that in the case that a BGPSEC speaker chooses to forward to an iBGP peer a BGPSEC update message that has not been successfully validated (see Section 5), the BGPSEC_Path_Signatures attribute SHOULD NOT be removed. (See Section 7 for the security ramifications of removing BGPSEC signatures.) The information protected by the signature on a BGPSEC update message includes the AS number of the peer to whom the update message is being sent. Therefore, if a BGPSEC speaker wishes to send a BGPSEC update to multiple BGP peers, it MUST generate a separate BGPSEC update message for each unique peer AS to which the update message is sent. A BGPSEC update message MUST advertise a route to only a single NLRI. This is because a BGPSEC speaker receiving an update message with multiple NLRI is unable to construct a valid BGPSEC update message (i.e., valid path signatures) containing a subset of the NLRI in the received update. If a BGPSEC speaker wishes to advertise routes to multiple NLRI, then it MUST generate a separate BGPSEC update message for each NLRI. Note that in order to create or add a new signature to a Signature- List Block for a given algorithm suite, the BGPSEC speaker must possess a private key suitable for generating signatures for this algorithm suite. Additionally, this private key must correspond to the public key in a valid Resource PKI end-entity certificate whose AS number resource extension includes the BGPSEC speaker's AS number. Note also new signatures are only added to a BGPSEC update message when a BGPSEC speaker is generating an update message to send to an external peer (i.e., when the AS number of the peer is not equal to the BGPSEC speaker's own AS number). Therefore, a BGPSEC speaker who only sends BGPSEC update messages to peers within its own AS, it does not need to possess any private signature keys. 4.1. Originating a New BGPSEC Update In an update message that originates a new route advertisement (i.e., an update whose AS_Path contains a single AS number), the BGPSEC speaker creates one Signature-List Block for each algorithm suite Lepinski Expires May 3, 2012 [Page 8] Internet-Draft BGPSEC Protocol October 2011 that will be used. Typically, a BGPSEC speaker will use only a single algorithm suite. However, to ensure backwards compatibility during a period of transition from a 'current' algorithm suite to a 'new' algorithm suite, it will be necessary to originate update messages containing Signature-List Blocks for both the 'current' and the 'new' algorithm suites (see Section 6.1). The Resource PKI enables the legitimate holder of IP address prefix(es) to issue a signed object, called a Route Origination Authorization (ROA), that authorizes a given AS to originate routes to a given set of prefixes (see [6]). Note that validation of a BGPSEC update message will fail (i.e., the validation algorithm, specified in Section 5.1, returns 'Not Good') unless there exists a valid ROA authorizing the first AS in the AS PATH attribute to originate routes to the prefix being advertised. Therefore, a BGPSEC speaker SHOULD NOT originate a BGPSEC update advertising a route for a given prefix unless there exists a valid ROA authorizing the BGPSEC speaker's AS to originate routes to this prefix. The Expire Time field is set to specify a time at which the route advertisement specified in the update message will cease to be valid. Once the Expire Time has been reached, all BGPSEC speakers who have received the advertisement will treat it as invalid. The purpose of this field is to protect the BGPSEC speaker against attacks in which a malicious BGPSEC peer either replays a stale update message, or else fails to propagate the withdrawal for a prefix. It is therefore necessary for the originating BGPSEC speaker to issue a new BGPSEC update, for the given prefix, prior to reaching the Expire Time. Setting appropriate values for Expire Time and for the rate at which new updates are sent out for a given prefix is an operational choice that involves trade offs between the window of replay protection versus network and processing load. Therefore, these settings are discussed in more detail in BGPSEC Operational Considerations document [9]. When originating a new route advertisement, each Signature-List Block MUST consist of a single Signature-Segment. The following describes how the BGPSEC speaker populates the fields of the Signature-List Block (see Section 3 for more information on the syntax of Signature- List Blocks). The pCount field is typically set to the value 1. However, a BGPSEC speaker may set the pCount field to a value greater than 1. Setting the pCount field to a value greater than one has the same semantics as repeating an AS number multiple times in the AS-PATH of a non- BGPSEC update message (e.g., for traffic engineering purposes). However, even when the pCount field is set to a value greater than 1, Lepinski Expires May 3, 2012 [Page 9] Internet-Draft BGPSEC Protocol October 2011 the BGPSEC speaker still only places a single copy of its AS number in the AS-PATH attribute. This is because the BGPSEC validation algorithm (see Section 5) requires a one-to-one correspondence between signatures and AS numbers in the AS-PATH. That is, setting a pCount value greater than 1 achieves the same semantics as repetition, but requires the generation of only a single signatures. Whereas a BGPSEC update message with actual repetition in the AS-PATH attribute would fail validation unless the BGPSEC speaker generated multiple signatures (one for each copy of the AS number placed in the AS-PATH). The Subject Key Identifier field (see Section 3) is populated with the identifier contained in the Subject Key Identifier extension of the RPKI end-entity certificate used by the BGPSEC speaker. This Subject Key Identifier will be used by recipients of the route advertisement to identify the proper certificate to use in verifying the signature. The Subject Key Identifier Length field is populated with the length (in octets) of the Subject Key Identifier. The Signature field contains a digital signature that binds the NLRI, AS_Path attribute and BGPSEC_Path_Signatures attribute to the RPKI end-entity certificate used by the BGPSEC speaker. The digital signature is computed as follows: o Construct a sequence of octets by concatenating the Expire Time, Target AS Number, Origin AS Number, Algorithm Suite Identifier, pCount and NLRI. The Target AS Number is the AS to whom the BGPSEC speaker intends to send the update message. (Note that the Target AS number is the AS number announced by the peer in the OPEN message of the BGP session within which the update is sent.) The Origin AS number prepend to this sequence the Target AS (the AS to whom the BGPSEC speaker intends to send the update message) and the Origin AS Number refers to the AS of the BGPSEC speaker who is originating the route advertisement. Lepinski Expires May 3, 2012 [Page 10] Internet-Draft BGPSEC Protocol October 2011 Sequence of Octets to be Signed +---------------------------------------+ | Expire Time (8 octets) | +---------------------------------------+ | Target AS Number (4 octets) | +---------------------------------------+ | Origin AS Number (4 octets) | +---------------------------------------+ | Algorithm Suite Identifier (1 octet) | +---------------------------------------+ | pCount (1 octet) | +---------------------------------------+ | NLRI Length (1 octet) | +---------------------------------------+ | NLRI Prefix (variable) | +---------------------------------------+ o Apply to this octet sequence the digest algorithm (for the algorithm suite of this Signature-List) to obtain a digest value. o Apply to this digest value the signature algorithm, (for the algorithm suite of this Signature-List) to obtain the digital signature. Then populate the Signature Field with this digital signature. 4.2. Propagating a Route Advertisement When a BGPSEC speaker receives a BGPSEC update message containing a BGPSEC_Path_Signatures algorithm (with one or more signatures) from a (internal or external) peer, it may choose to propagate the route advertisement by sending to its (internal or external) peers by creating a new BGPSEC advertisement for the same prefix. A BGPSEC speaker MUST NOT generate an update message containing the BGPSEC_Path_Signatures attribute unless it has selected, as the best route to the given prefix, a route that it received in an update message containing the BGPSEC_Path_Signatures attribute. In particular, this means that whenever a BGPSEC speaker generates an update message with a BGPSEC_Path_Signatures attribute that it will possess a received update message for the same prefix that also contains a BGPSEC_Path_Signatures attribute. Additionally, whenever a BGPSEC speaker selects as the best route to a given prefix a route that it received in an update message containing the BGPSEC_Path_Signatures attribute, it is RECOMMENDED that if the BGPSEC speaker chooses to propagate the route that it generate an update message containing the BGPSEC_Path_Signatures attribute. However, a BGPSEC speaker MAY propagate a route Lepinski Expires May 3, 2012 [Page 11] Internet-Draft BGPSEC Protocol October 2011 advertisement by generating a (non-BGPSEC) update message that does not contain the BGPSEC_Path_Signatures attribute. Note that if a BGPSEC speaker receives a route advertisement containing the BGPSEC_Path_Signatures attribute and chooses for any reason (e.g., its peer is a non-BGPSEC speaker) to propagate the route advertisement as a non-BGPSEC update message without the BGPSEC_Path_Signatures attribute, then it MUST follow the instructions in Section 4.2.1. Note that removing BGPSEC signatures (i.e., propagating a route advertisement without the BGPSEC_Path_Signatures attribute) has significant security ramifications. (See Section 7 for discussion of the security ramifications of removing BGPSEC signatures.) Therefore, when a route advertisement is received via a BGPSEC update message, propagating the route advertisement without the BGPSEC_Path_Signatures attribute is NOT RECOMMENDED. Furthermore, note that when a BGPSEC speaker propagates a route advertisement with the BGPSEC_Path_Signatures attribute it is attesting to the fact that: (1) it received a BGPSEC update message that advertised this route; and (2) it chose this route as its best path to the given prefix. That is, the BGPSEC speaker is not attesting to the validation state of the update message it received. (See Section 7 for more discussion of the security semantics of BGPSEC signatures.) If the BGPSEC speaker is producing an update message which contains an AS-SET (e.g., the BGPSEC speaker is performing proxy aggregation), then the BGPSEC speaker MUST NOT include the BGPSEC_Path_Signatures attribute. In such a case, the BGPSEC speaker must remove any existing BGPSEC_Path_Signatures in the received advertisement(s) for this prefix and produce a standard (non-BGPSEC) update message. To generate the BGPSEC_Path_Signatures attribute on the outgoing update message, the BGPSEC first copies the Expire Time directly from the received update message to the new update message (that it is constructing). Note that the BGPSEC speaker MUST NOT change the Expire Time as any change to Expire Time will cause the new BGPSEC update message to fail validation (see Section 5). If the received BGPSEC update message contains two Signature-List Blocks and the BGPSEC speaker supports both of the corresponding algorithms suites, then the BGPSEC speaker SHOULD generate a new update message that includes both of the Signature-List Blocks. If the received BGPSEC update message contains two Signature-List Blocks and the BGPSEC speaker only supports one of the two corresponding algorithm suites, then the BGPSEC speaker MUST remove the Signature- List Block corresponding to the algorithm suite that it does not understand. If the BGPSEC speaker does not support the algorithm suites in any of the Signature-List Blocks contained in the received Lepinski Expires May 3, 2012 [Page 12] Internet-Draft BGPSEC Protocol October 2011 update message, then the BGPSEC speaker MUST NOT propagate the route advertisement with the BGPSEC_Path_Signatures attribute. (See Section 4.2.1 for information on removing the BGPSEC_Path_Signatures attribute when propagating route advertisements.) Note that in the case where there are two Signature-List Blocks (corresponding to different algorithm suites) that the validation algorithm (see Section 5.1) deems a BGPSEC update message to be 'Good' if there is at least one supported algorithm suite (and corresponding Signature-List Block) that is deemed 'Good'. This means that a 'Good' BGPSEC update message may contain a Signature- List Block which is deemed 'Not Good' (e.g., contains signatures that the BGPSEC is unable to verify). Nonetheless, such Signature-List Blocks MUST NOT be removed. (See Section 7 for a discussion of the security ramifications of this design choice.) For each Signature-List Block corresponding to an algorithm suite that the BGPSEC speaker does support, the BGPSEC speaker then adds a new Signature-Segment to the Signature-List Block. This Signature- Segment is prepended to the list of Signature-Segments (placed in the first position) so that the list of Signature-Segments appears in the same order as the corresponding AS numbers in the AS-Path attribute. The BGPSEC speaker populates the fields of this new signature-segment as follows. The pCount is typically set to the value 1. A BGPSEC speaker may set the pCount field to a value greater than 1. (See Section 4.1 for a discussion of setting pCount to a value greater than 1.) A route server that participates in the BGP control path, but does not act as a transit AS in the data plane, may choose to set pCount to 0. This option enables the route server to participate in BGPSEC and obtain the associated security guarantees without increasing the effective length of the AS-PATH. (Note that BGPSEC speakers compute the effective length of the AS-PATH by summing the pCount values in the BGPSEC_Path_Signatures attribute, see Section 5.) However, when a route server sets the pCount value to 0, it still inserts its AS number into the AS-PATH, as this information is needed to validate the signature added by the route server. Note that the option of setting pCount to 0 is intended only for use by route servers that desire not to increase the effective AS-PATH length of routes they advertise. The pCount field SHOULD NOT be set to 0 in other circumstances. BGPSEC speakers SHOULD drop incoming update messages with pCount set to zero in cases where the BGPSEC speaker does not expect its peer to set pCount to zero (i.e., cases where the peer is not acting as a route server). The Subject Key Identifier field in the new segment is populated with the identifier contained in the Subject Key Identifier extension of Lepinski Expires May 3, 2012 [Page 13] Internet-Draft BGPSEC Protocol October 2011 the RPKI end-entity certificate used by the BGPSEC speaker. This Subject Key Identifier will be used by recipients of the route advertisement to identify the proper certificate to use in verifying the signature. The Subject Key Identifier Length field is populated with the length (in octets) of the Subject Key Identifier. The Signature field in the new segment contains a digital signature that binds the NLRI, AS_Path attribute and BGPSEC_Path_Signatures attribute to the RPKI end-entity certificate used by the BGPSEC speaker. The digital signature is computed as follows: o Construct a sequence of octets by concatenating the signature field of the most recent Signature-Segment (the one corresponding to AS from whom the BGPSEC speaker's AS received the announcement) with the pCount field inserted by the signer, and the Target AS (the AS to whom the BGPSEC speaker intends to send the update message). Note that the Target AS number is the AS number announced by the peer in the OPEN message of the BGP session within which the BGPSEC update message is sent. Sequence of Octets to be Signed +-----------------------------------------------------------+ | Most Recent Signature Field (fixed by algorithm suite) | +-----------------------------------------------------------+ | pCount Field of Signer (1 octet) | +-----------------------------------------------------------+ | Target AS Number (4 octets) | +-----------------------------------------------------------+ o Apply to this octet sequence the digest algorithm (for the algorithm suite of this Signature-List) to obtain a digest value. o Apply to this digest value the signature algorithm, (for the algorithm suite of this Signature-List) to obtain the digital signature. Then populate the Signature Field with this digital signature. 4.2.1. Propogating an Update without the Path_Signatures attribute As discussed earlier in Section 4.2, a BGPSEC speaker may receive a BGPSEC update message that contains the BGPSEC_Path_Signatures Attribute and propagate the associated route in a non-BGPSEC update message that does not contain the BGPSEC_Path_Signatures attribute. A BGPSEC speaker MUST remove the BGPSEC_Path_Signatures attribute Lepinski Expires May 3, 2012 [Page 14] Internet-Draft BGPSEC Protocol October 2011 when propagating a route advertisement to a peer that has not advertised support BGPSEC (see Section 2), when propagating a route advertisement that contains an AS-SET in the AS-PATH, or when the BGPSEC speaker does not support any algorithm suite used to generate signatures in the received update message. In all other cases, the BGPSEC speaker SHOULD NOT remove the BGPSEC_Path_Signatures attribute. When the BGPSEC speaker receives a BGPSEC update message that contains the BGPSEC_Path_Signatures Attribute and propagates the associated route in a non-BGPSEC update message, the BGPSEC MUST perform a transformation on the AS-PATH in the non-BGPSEC update message that it generates. The reason for this is that the AS-PATH attribute has slightly different semantics in a BGPSEC update message than it has in a non-BGPSEC update message. To generate the AS-PATH in the outgoing non-BGPSEC update message, the BGPSEC speaker performs the following steps for each AS number in the AS-PATH of the received BGPSEC update message. (Note that there is a one-to-one correspondence between the AS numbers in the AS-PATH of a BGPSEC update message and the Signature Segments in the Signature-List Block of the BGPSEC_Path_Signatures attribute. The follows step will make use of this correspondence.) o For each AS number in the AS-PATH of the received BGPSEC update message, locate the pCount value in the corresponding Signature Segment. o If the pCount value is equal to 0, then do not include the corresponding AS in the AS-PATH of the outgoing non-BGPSEC update message. o If the pCount value is greater than or equal to 1, insert into the AS-PATH of the outgoing update message a number of copies of the corresponding AS number equal to the pCount value. Other than the above transformation that is applied to the AS-PATH, no additional special behavior is required when removing BGPSEC signatures from BGPSEC update messages. That is, all other attributes in the outgoing non-BGPSEC update message are generated as they would normally be generated by the BGP speaker in a non-BGPSEC update message. 5. Processing a Received BGPSEC Update Validation of a BGPSEC update messages makes use of data from RPKI certificates and signed Route Origination Authorizations (ROA). In Lepinski Expires May 3, 2012 [Page 15] Internet-Draft BGPSEC Protocol October 2011 particular, to validate update messages containing the BGPSEC_Path_Signatures attribute, it is necessary that the recipient have access to the following data obtained from valid RPKI certificates and ROAs: o For each valid RPKI end-entity certificate containing an AS Number extension, the AS Number, Public Key and Subject Key Identifier are required o For each valid ROA, the AS Number and the list of IP address prefixes Note that the BGPSEC speaker could perform the validation of RPKI certificates and ROAs on its own and extract the required data, or it could receive the same data from a trusted cache that performs RPKI validation on behalf of (some set of) BGPSEC speakers. (The latter case in analogous to the use of the RPKI-RTR protocol [10] for origin validation.) To validate a BGPSEC update message containing the BGPSEC_Path_Signatures attribute, the recipient performs the validation steps specified in Section 5.1. The validation procedure results in one of two states: 'Good' and 'Not Good'. It is expected that the output of the validation procedure will be used as an input to BGP route selection. However, BGP route selection and thus the handling of the two validation states is a matter of local policy, and shall be handled using existing local policy mechanisms. It is expected that BGP peers will generally prefer routes received via 'Good' BGPSEC update messages over routes received via 'Not Good' BGPSEC update messages as well as routes received via update messages that do not contain the BGPSEC_Path_Signatures attribute. However, BGPSEC specifies no changes to the BGP decision process and leaves to the operator the selection of an appropriate policy mechanism to achieve the operator's desired results within the BGP decision process. BGPSEC validation need only be performed at eBGP edge. The validation status of a BGP signed/unsigned update MAY be conveyed via iBGP from an ingress edge router to an egress edge router. Local policy in the AS determines the specific means for conveying the validation status through various pre-existing mechanisms (e.g., modifying an attribute). As discussed in Section 4, when a BGPSEC speaker chooses to forward a (syntactically correct) BGPSEC update message, it SHOULD be forwarded with its BGPSEC_Path_Signatures attribute intact (regardless of the validation state of the update message). Based entirely on local policy settings, an egress router MAY trust the validation status conveyed by an ingress router or it Lepinski Expires May 3, 2012 [Page 16] Internet-Draft BGPSEC Protocol October 2011 MAY perform its own validation. Upon receiving a BGPSEC update message, a BGPSEC speaker SHOULD sum the pCount values within BGPSEC_Path_Signatures attribute to determine the effective length of the AS Path. The BGPSEC speaker SHOULD use this sum of pCount values in precisely the same way as it uses the length of the AS Path in non-BGPSEC update messages. 5.1. Validation Algorithm This section specifies an algorithm for validation of BGPSEC update messages. A conformant implementation MUST include an BGPSEC update validation algorithm that is functionally equivalent to the external behavior of this algorithm. First, the recipient of a BGPSEC update message performs a check to ensure that the message is properly formed. Specifically, the recipient performs the following checks: o Check to ensure that the entire BGPSEC_Path_Signatures attribute is syntactically correct (conforms to the specification in this document). o Check to ensure that the AS-Path attribute contains no AS-Set segments. o Check that each Signature-List Block contains one Signature- Segment for each AS in the AS-Path attribute. (Note that the entirety of each Signature-List Block must be checked to ensure that it is well formed, even though the validation process may terminate before all signatures are cryptographically verified.) If there are two Signature-List Blocks within the BGPSEC_Path_Signatures attribute and one of them is poorly formed (or contains the wrong number of Signature-Segments) , then the recipient should log that an error occurred, strip off that particular Signature-List Block and process the update message as though it arrived with a single Signature-List Block. If the BGPSEC_Path_Signatures attribute contains a syntax error that is not local to one of two Signature-List Blocks, then the recipient should log that an error occurred and drop the update message containing the error. Similarly, if an update message contains both the BGPSEC_Path_Signatures attribute and an AS-Path attribute that contains an AS-Set segment, then the recipient should log that an error occurred and drop the update message containing the error. Second, the BGPSEC speaker verifies that the update message has not yet expired. To do this, locate the Expire Time field in the Lepinski Expires May 3, 2012 [Page 17] Internet-Draft BGPSEC Protocol October 2011 BGPSEC_Path_Signatures attribute, and compare it with the current time. If the current time is later than the Expire Time, the BGPSEC update is 'Not Good' and the validation algorithm terminates. Third, the BGPSEC speaker verifies that the origin AS is authorized to advertise the prefix in question. To do this, consult the valid ROA data to obtain a list of AS numbers that are associated with the given IP address prefix in the update message. Then locate the last (least recently added) AS number in the AS-Path. If the origin AS in the AS-Path is not in the set of AS numbers associated with the given prefix, then BGPSEC update message is 'Not Good' and the validation algorithm terminates. Finally, the BGPSEC speaker examines the Signature-List Blocks in the BGPSEC_Path_Signatures attribute. Any Signature-List Block corresponding to an algorithm suite that the BGPSEC speaker does not support is not considered in validation. If there does not exist a Signature-List Block corresponding to an algorithm suite that the BGPSEC speaker supports, then the BGPSEC speaker MUST treat the update message in the same manner that the BGPSEC speaker would treat an update message that arrived without a BGPSEC_Path_Signatures attribute. For each remaining Signature-List Block (corresponding to an algorithm suite supported by the BGPSEC speaker), the BGPSEC speaker iterates through the Signature-Segments in the Signature-List block, starting with the most recently added segment (and concluding with the least recently added segment). Note that there is a one-to-one correspondence between Signature-Segments and AS numbers in the AS- Path attribute, and the following steps make use of this correspondence. o (Step I): Locate the public key needed to verify the signature (in the current Signature-Segment). To do this, consult the valid RPKI end-entity certificate data and look for an SKI that matches the value in the SKI field of the Signature-Segment. If no such SKI value is found in the valid RPKI data then mark the entire Signature-List Block as 'Not Good' and proceed to the next Signature-List Block. Similarly, if the SKI exists but the AS Number associated with the SKI does NOT match the AS Number (in the AS-Path attribute) which corresponds to the current Signature- Segment, then mark the entire Signature-List Block as 'Not Good' and proceed to the next Signature-List Block. o (Step II): Compute the digest function (for the given algorithm suite) on the appropriate data. If the segment is not the (least recently added) segment corresponding to the origin AS, then the digest function should be computed on the following sequence of Lepinski Expires May 3, 2012 [Page 18] Internet-Draft BGPSEC Protocol October 2011 octets: Sequence of Octets to be Hashed +-------------------------------------------------+ | Signature Field in the Next Segment (variable) | +-------------------------------------------------+ | pCount Field in the Current Segment (1 octet) | +-------------------------------------------------+ | AS Number of Subsequent AS (4 octets) | +-------------------------------------------------+ The 'Signature Field in the Next Segment' is the Signature field found in the Signature-Segment that is next to be processed (that is, the next most recently added Signature- Segment). The 'pCount Field in the Current Segment' is the pCount field found in the Signature- Segment that is currently being processed. For the first segment to be processed (the most recently added segment), the 'AS Number of Subsequent AS' is the AS number of the BGPSEC speaker validating the update message. Note that if a BGPSEC speaker uses multiple AS Numbers (e.g., the BGPSEC speaker is a member of a confederation), the AS number used here MUST be the AS number announced in the OPEN message for the BGP session over which the BGPSEC update was received. For each other Signature-Segment, the 'AS Number of Subsequent AS' is the AS that corresponds to the Signature-Segment added immediately after the one being processed. (That is, find the AS number corresponding to the Signature-Segment currently being processed and the 'AS Number of Subsequent AS' is the next AS number that was added to the AS-Path attribute.) Alternatively, if the segment being processed corresponds to the origin AS, then the digest function should be computed on the following sequence of octets: Lepinski Expires May 3, 2012 [Page 19] Internet-Draft BGPSEC Protocol October 2011 Sequence of Octets to be Hashed +----------------------------------------+ | Expire Time (8 octets) | -----------------------------------------+ | AS Number of Subsequent AS (4 octets) | +----------------------------------------+ | Origin AS Number (4 octets) | +----------------------------------------+ | Algorithm Suite Identifier (1 octet) | +----------------------------------------+ | pCount (1 octet) | +----------------------------------------+ | NLRI Length (1 octet) | +----------------------------------------+ | NLRI Prefix (variable) | +----------------------------------------+ The NLRI Length, NLRI Prefix, Expire Time, and Algorithm Suite Identifier are all obtained in a straight forward manner from the NLRI of the update message or the BGPSEC_Path_Signatures attribute being validated. The pCount field is taken from the Signature- Segment currently being processed. The Origin AS Number is the same Origin AS Number that was located in Step I above. (That is, the AS number corresponding to the least recently added Signature-Segment.) The 'AS Number of Subsequent AS' is the AS Number added to the AS- Path immediately after the Origin AS Number. (That is, the second AS Number that was added to the AS Path.) o (Step III): Use the signature validation algorithm (for the given algorithm suite) to verify the signature in the current segment. That is, invoke the signature validation algorithm on the following three inputs: the value of the Signature field in the current segment; the digest value computed in Step II above; and the public key obtained from the valid RPKI data in Step I above. If the signature validation algorithm determines that the signature is invalid, then mark the entire Signature-List Block as 'Not Good' and proceed to the next Signature-List Block. If the signature validation algorithm determines that the signature is valid, then continue processing Signature-Segments (within the current Signature-List Block). If all Signature-Segments within a Signature-List Block pass validation (i.e., all segments are processed and the Signature-List Block has not yet been marked 'Not Good'), then the Signature-List Lepinski Expires May 3, 2012 [Page 20] Internet-Draft BGPSEC Protocol October 2011 Block is marked as 'Good'. If at least one Signature-List Block is marked as 'Good', then the validation algorithm terminates and the BGPSEC update message is deemed to be 'Good'. (That is, if a BGPSEC update message contains two Signature-List Blocks then the update message is deemed 'Good' if the first Signature-List block is marked 'Good' OR the second Signature-List block is marked 'Good'.) 6. Algorithms and Extensibility 6.1. Algorithm Suite Considerations Note that there is currently no support for bilateral negotiation between BGPSEC peers to use of a particular (digest and signature) algorithm suite using BGP capabilities. This is because the algorithm suite used by the sender of a BGPSEC update message must be understood not only by the peer to whom he is directly sending the message, but also by all BGPSEC speakers to whom the route advertisement is eventually propagated. Therefore, selection of an algorithm suite cannot be a local matter negotiated by BGP peers, but instead must be coordinated throughout the Internet. To this end, a mandatory algorithm suites document will be created which specifies a mandatory-to-use 'current' algorithm suite for use by all BGPSEC speakers. Additionally, the document specifies an additional 'new' algorithm suite that is recommended to implement. It is anticipated that in the future the mandatory algorithm suites document will be updated to specify a transition from the 'current' algorithm suite to the 'new' algorithm suite. During the period of transition (likely a small number of years), all BGPSEC update messages SHOULD simultaneously use both the 'current' algorithm suite and the 'new' algorithm suite. (Note that Sections 3 and 4 specify how the BGPSEC_Path_Signatures attribute can contain signatures, in parallel, for two algorithm suites.) Once the transition is complete, use of the old 'current' algorithm will be deprecated, use of the 'new' algorithm will be mandatory, and a subsequent 'even newer' algorithm suite may be specified as recommend to implement. Once the transition has successfully been completed in this manner, BGPSEC speakers SHOULD include only a single Signature-List Block (corresponding to the 'new' algorithm). 6.2. Extensibility Considerations This section discusses potential changes to BGPSEC that would require substantial changes to the processing of the BGPSEC_Path_Signatures Lepinski Expires May 3, 2012 [Page 21] Internet-Draft BGPSEC Protocol October 2011 and thus necessitate a new version of BGPSEC. Examples of such changes include: o A new type of signature algorithm that produces signatures of variable length o A new type of signature algorithm for which the number of signatures in the Signature-List Block is not equal to the number of ASes in the AS-PATH (e.g., aggregate signatures) o Changes to the data that is protected by the BGPSEC signatures (e.g., protection of attributes other than AS-PATH) In the case that such a change to BGPSEC were deemed desirable, it is expected that a subsequent version of BGPSEC would be created and that this version of BGPSEC would specify a new BGP Path Attribute, let's call it BGPSEC_PATH_SIG_TWO, which is designed to accommodate the desired changes to BGPSEC. In such a case, the mandatory algorithm suites document would be updated to specify algorithm suites appropriate for the new version of BGPSEC. At this point a transition would begin which is analogous to the algorithm transition discussed in Section 6.2. During the transition period all BGPSEC speakers SHOULD simultaneously include both the BGPSEC_PATH_SIGNATURES attribute and the new BGPSEC_PATH_SIG_TWO attribute. Once the transition is complete, the use of BGPSEC_PATH_SIGNATURES could then be deprecated, at which point BGPSEC speakers SHOULD include only the new BGPSEC_PATH_SIG_TWO attribute. Such a process could facilitate a transition to a new BGPSEC semantics in a backwards compatible fashion. 7. Security Considerations For discussion of the BGPSEC threat model and related security considerations, please see [8]. A BGPSEC speaker who receives a valid BGPSEC update message, containing a route advertisement for a given prefix, is provided with the following security guarantees: o The origin AS number corresponds to an autonomous system that has been authorized by the IP address space holder to originate route advertisements for the given prefix. o For each subsequent AS number in the AS-Path, a BGPSEC speaker authorized by the holder of the AS number selected the given route as the best route to the given prefix. Lepinski Expires May 3, 2012 [Page 22] Internet-Draft BGPSEC Protocol October 2011 o For each AS number in the AS Path, a BGPSEC speaker authorized by the holder of the AS number intentionally propagated the route advertisement to the next AS in the AS-Path. That is, the recipient of a valid BGPSEC Update message is assured that the AS-Path corresponds to a sequence of autonomous systems who have all agreed in principle to forward packets to the given prefix along the indicated path. (It should be noted BGPSEC does not offer a precise guarantee that the data packets would propagate along the indicated path; it only guarantees that the BGP update conveying the path indeed propagated along the indicated path.) Furthermore, the recipient is assured that this path terminates in an autonomous system that has been authorized by the IP address space holder as a legitimate destination for traffic to the given prefix. Note that although BGPSEC provides a mechanism for an AS to validate that a received update message has certain security properties, the use of such a mechanism to influence route selection is completely a matter of local policy. Therefore, a BGPSEC speaker can make no assumptions about the validity of a route received from an external BGPSEC peer. That is, a compliant BGPSEC peer may (depending on the local policy of the peer) send update messages that fail the validity test in Section 5. Thus, a BGPSEC speaker MUST completely validate all BGPSEC update messages received from external peers. (Validation of update messages received from internal peers is a matter of local policy, see Section 5). Note that there may be cases where a BGPSEC speaker deems 'Good' (as per the validation algorithm in Section 5.1) a BGPSEC update message that contains both a 'Good' and a 'Not Good' Signature-List Block. That is, the update message contains two sets of signatures corresponding to two algorithm suites, and one set of signatures verifies correctly and the other set of signatures fails to verify. In this case, the protocol specifies that if the BGPSEC speaker propagates the route advertisement received in such an update message then the BGPSEC speaker SHOULD add its signature to each of the Signature-List Blocks using both the corresponding algorithm suite. Thus the BGPSEC speaker creates a signature using both algorithm suites and creates a new update message that contains both the 'Good' and the 'Not Good' set of signatures (from its own vantage point). To understand the reason for such a design decision consider the case where the BGPSEC speaker receives an update message with both a set of algorithm A signatures which are 'Good' and a set of algorithm B signatures which are 'Not Good'. In such a case it is possible (perhaps even quite likely) that some of the BGPSEC speaker's peers (or other entities further 'downstream' in the BGP topology) do not support algorithm A. Therefore, if the BGPSEC speaker were to remove Lepinski Expires May 3, 2012 [Page 23] Internet-Draft BGPSEC Protocol October 2011 the 'Not Good' set of signatures corresponding to algorithm B, such entities would treat the message as though it were unsigned. By including the 'Not Good' set of signatures when propagating a route advertisement, the BGPSEC speaker ensures that 'downstream' entities have as much information as possible to make an informed opinion about the validation status of a BGPSEC update. Note also that during a period of partial BGPSEC deployment, a 'downstream' entity might reasonably treat unsigned messages different from BGPSEC updates that contain a single set of 'Not Good' signatures. That is, by removing the set of 'Not Good' signatures the BGPSEC speaker might actually cause a downstream entity to 'upgrade' the status of a route advertisement from 'Not Good' to unsigned. Finally, note that in the above scenario, the BGPSEC speaker might have deemed algorithm A signatures 'Good' only because of some issue with RPKI state local to his AS (for example, his AS might not yet have obtained a CRL indicating that a key used to verify an algorithm A signature belongs to a newly revoked certificate). In such a case, it is highly desirable for a downstream entity to treat the update as 'Not Good' (due to the revocation) and not as 'unsigned' (which would happen if the 'Not Good' Signature-List Blocks were removed). A similar argument applies to the case where a BGPSEC speaker (for some reason such as lack of viable alternatives) selects as his best route to a given prefix a route obtained via a 'Not Good' BGPSEC update message. (That is, a BGPSEC update containing only 'Not Good' Signature-List Blocks.) In such a case, the BGPSEC speaker should propagate a signed BGPSEC update message, adding his signature to the 'Not Good' signatures that already exist. Again, this is to ensure that 'downstream' entities are able to make an informed decision and not erroneously treat the route as unsigned. It may also be noted here that due to possible differences in RPKI data at different vantage points in the network, a BGPSEC update that was deemed 'Not Good' at an upstream BGPSEC speaker may indeed be deemed 'Good' at another BGP speaker downstream. Therefore, it is important to note that when a BGPSEC speaker signs an outgoing update message, it is not attesting to a belief that all signatures prior to its are valid. Instead it is merely asserting that: 1. The BGPSEC speaker received the given route advertisement with the indicated NLRI and AS Path; 2. The BGPSEC speaker selected this route as the best route to the given prefix; and Lepinski Expires May 3, 2012 [Page 24] Internet-Draft BGPSEC Protocol October 2011 3. The BGPSEC speaker chose to propagate an advertisement for this route to the peer (implicitly) indicated by the 'Target AS' The BGPSEC update validation procedure is a potential target for denial of service attacks against a BGPSEC speaker. To mitigate the effectiveness of such denial of service attacks, BGPSEC speakers should implement an update validation algorithm that performs expensive checks (e.g., signature verification) after less expensive checks (e.g., syntax checks). The validation algorithm specified in Section 5.1 was chosen so as to perform checks which are likely to be expensive after checks that are likely to be inexpensive. However, the relative cost of performing required validation steps may vary between implementations, and thus the algorithm specified in Section 5.1 may not provide the best denial of service protection for all implementations. Finally, the mechanism of setting the pCount field to zero is included in this specification to enable route servers in the control path to participate in BGPSEC without increasing the effective length of the AS-PATH. However, entities other than route servers could conceivably use this mechanism (set the pCount to zero) to attract traffic (by reducing the effective length of the AS-PATH) illegitimately. This risk is largely mitigated if every BGPSEC speaker drops incoming update messages that set pCount to zero but come from a peer that is not a route server. However, note that a recipient of a BGPSEC update message in which an upstream entity that is two or more hops away set pCount to zero is unable to verify for themselves whether pCount was set to zero legitimately. 8. IANA Considerations IANA is requested to create a registry of BGPSEC algorithm suite identifiers. This registry shall contain four fields, a one octet Algorithm Suite Identifier, the name of the suite's digest algorithm, the name of the suite's signature algorithm, and a specification pointer containing a reference to the formal specification of the algorithm suite. That is, entries in the registry have the following form: Lepinski Expires May 3, 2012 [Page 25] Internet-Draft BGPSEC Protocol October 2011 Algorithm Suite Digest Signature Specification Identifier Algorithm Algorithm Pointer +-----------------+--------------+----------------+---------------+ | | | | | +-----------------+--------------+----------------+---------------+ The entries in this registry shall be managed by IETF consensus. 9. Contributors 9.1. Authors Rob Austein Dragon Research Labs sra@hactrn.net Steven Bellovin Columbia University smb@cs.columbia.edu Randy Bush Internet Initiative Japan randy@psg.com Russ Housley Vigil Security housley@vigilsec.com Matt Lepinski BBN Technologies lepinski@bbn.com Stephen Kent BBN Technologies kent@bbn.com Warren Kumari Google warren@kumari.net Lepinski Expires May 3, 2012 [Page 26] Internet-Draft BGPSEC Protocol October 2011 Doug Montgomery USA National Institute of Standards and Technology dougm@nist.gov Kotikalapudi Sriram USA National Institute of Standards and Technology kotikalapudi.sriram@nist.gov Samuel Weiler Cobham weiler+ietf@watson.org 9.2. Acknowledgements The authors would like to thank Luke Berndt, Sharon Goldberg, Ed Kern, Chris Morrow, Doug Maughan, Pradosh Mohapatra, Russ Mundy, Sandy Murphy, Keyur Patel, Mark Reynolds, Heather Schiller, Jason Schiller, John Scudder, Ruediger Volk and David Ward for their valuable input and review. 10. Normative References [1] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A Border Gateway Protocol 4", RFC 4271, January 2006. [2] Bates, T., Chandra, R., Katz, D., and Y. Rekhter, "Multiprotocol Extensions for BGP-4", RFC 4760, January 2007. [3] Scudder, J. and R. Chandra, "Capabilities Advertisement with BGP-4", RFC 5492, February 2009. [4] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [5] Patel, K., Ward, D., and R. Bush, "Extended Message support for BGP", March 2011. [6] Lepinski, M., Kent, S., and D. Kong, "A Profile for Route Origin Authorizations", February 2011. [7] Lepinski, M. and S. Kent, "An Infrastructure to Support Secure Internet Routing", February 2011. [8] Kent, S., "Threat Model for BGP Path Security", June 2011. Lepinski Expires May 3, 2012 [Page 27] Internet-Draft BGPSEC Protocol October 2011 [9] Bush, R., "BGPsec Operational Considerations", October 2011. [10] Bush, R. and R. Austein, "The RPKI/Router Protocol", October 2011. Author's Address Matthew Lepinski (editor) BBN 10 Moulton St Cambridge, MA 55409 US Phone: +1 617 873 5939 Email: mlepinski@bbn.com Lepinski Expires May 3, 2012 [Page 28]