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Network Working Group                                         Russ White
Internet Draft                                                  (editor)
Expiration Date: October 2004                              Cisco Systems
File Name: draft-white-sobgparchitecture-00.txt               April 2004

Architecture and Deployment Considerations for Secure Origin BGP (soBGP)
                  draft-white-sobgparchitecture-00.txt

   Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   Internet Drafts are working documents of the Internet Engineering
   Task Force (IETF), its Areas, and its Working Groups. Note that other
   groups may also distribute working documents as Internet Drafts.

   Internet Drafts are draft documents valid for a maximum of six
   months.  Internet Drafts may be updated, replaced, or obsoleted by
   other documents at any time. It is not appropriate to use Internet
   Drafts as reference material or to cite them other than as a "working
   draft" or "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.

   Abstract

   There is a great deal of concern over the security of the Border
   Gateway Protocol, which is used to provide routing information to the
   Internet and other large internetworks. This draft provides an
   architecture for a secure distributed registry of routing information
   to address these concerns. The draft begins with an overview of the
   operation of this system, and then follows with various deployment
   scenerios, starting with what we believe will be the most common
   deployment option.












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1. Background

   There are two fundamental pieces of a routing system that need to be
   secured:


   o    Adjacencies between devices running the routing protocol

   o    Information carried within the routing protocol.

   While security between BGP [BGP] speakers has been addressed in a
   number of ways, including cryptographic authentication [BGP-MD5] and
   limiting the attack radius through TTL mechanisms [GTSH], security
   for the information carried within BGP is not considered a solved
   problem.

   This draft proposes a possible solution to securing the information
   within BGP, using the certificates and protocol extensions proposed
   in [SOBGP-BGPTRANSPORT], [SOBGP-CERTIFICATE], and [SOBGP-RADIUS].

   A large number of people contributed to this draft; we've tried to
   include all of them here (but might have missed a few): James Ng, Tim
   Gage, Alvaro Retana, Dave Cook, Brian Weis, and Iljitsch van Beijnum.


2. General Theory

   soBGP provides a secure registry mechanism against which a BGP
   speaker can check:


   o    The authorization of the AS listed as the originating AS in any
        received update to advertise reachability to the prefix listed
        in the update.

   o    The validity of the AS Path contained in the update.

   We use the term validity in reference to the AS Path, in this docu-
   ment, to indicate the plausibility of the AS Path listed. As shown in
   [PATH-CONSIDER], it isn't possible to communicate authorization
   through an AS Path; only the existence or nonexistance of the AS Path
   listed can be proven.

   soBGP operates by distributing a set of signed certificates,
   described in [SOBGP-CERTIFICATE], containing the information required
   to validate the two pieces of information given above. These certifi-
   cates MAY be distributed using the mechanisms described in [SOBGP-
   BGPTRANSPORT], or some other mechanism. Once these certificates have



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   been received and processed (signatures validated, etc, as described
   in [SOBGP-CERTIFICATE], they form a database containing:


   o    A listing of IP address blocks and the AS authorized to ori-
        ginate them.

   o    Policies related to specific prefixes and blocks of addresses.

   o    A list of autonomous systems connected to each autonomous system
        within the internetwork. This connection list is used to build a
        graph of AS interconnectivity within the internetwork, as
        described in the section Building the AS Connectivity Graph,
        below.

   This effectively forms a secure registry of routing information which
   can be used to check the validity of routing information received
   from BGP peers. This database is termed the "authorization database."
   No assumption about the location of the authorization database is
   made within this document.

   When soBGP is supported, a BGP speaker MUST have access to the
   authorization database. Possible methods of access include:


   o    Have a local copy of this authorization database, and perform
        the checkes described later in this document against that local
        database.

   o    Pass received routing information to a locally maintained server
        for validation against that server's copy of the authorization
        database.

   o    Accept filters built from a copy of the authorization database
        contained on a locally maintained server.

   As BGP updates are processed, a security preference is assigned to
   each prefix, as described further in the Security Preference section
   of this document. BGP update processing is described in the Receiving
   and Processing Updates section of this document.











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3. soBGP Operation

   Each section below provides detailed information on some aspect of
   soBGP operation.


3.1. The Security Preference

   Rather than simply noting a given prefix should be dropped (not
   trusted) or retained (trusted), soBGP extends the concept of locally
   generated and maintained policy in BGP by assigning each prefix a
   Security Preference. This allows the local operator to drop prefixes
   not meeting certain security criteria, while simply lowering their
   preference for prefixes meeting some security criteria. This allows
   operators some flexibility in their implementation of security poli-
   cies, especially as the security system is being tested, or while the
   security system isn't fully deployed.

   While the amount by which the Security Preference is increased or
   decreased for any operation described in this draft is locally signi-
   ficant to the autonomous system. All devices processing routes
   against soBGP information MUST use the same mechanisms and values of
   the Security Preference to ensure consistent routing within the auto-
   nomous system.

   If the Security Preference is set to a value precluding a route from
   further consideration in the decision process, the route should be
   discarded at that point, rather than continuing with the decision
   process.

   The Security Preference value may be used to select among different
   routes for the same prefix; the higher value MUST be preferred. Any
   of the following methods may be used:

   A    Consider the Security Preference prior to calculating the degree
        of preference [BGP] for a prefix.

   B    Assign the value of the Security Preference to any of the attri-
        butes used in the Decision Process [BGP]. Care must be taken
        with attributes for which the lower value is preferred.

   C    Use a Cost Community [COST] and its associated methods to con-
        sider the Security Preference at any step in the Decision Pro-
        cess [BGP] without overloading other attributes. Care must be
        taken as the lowest value in a Cost Community is preferred.

   The method selected MUST be consistent through the local Autonomous
   System.



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3.2. Building the AS Connectivity Graph

   Each ASPolicyCert advertised by a member of the internetwork contains
   a list of the autonomous systems the advertising AS is connected to,
   along with possible policy information about that connection. From
   this information, a graph of AS connectivity within the internetwork
   is built.

   Any AS can be used as the starting point for building this graph,
   thus multiple disconnected graphs (representing section of the inter-
   network running soBGP and providing interconnection information) are
   possible. If every AS within the internetwork is providing intercon-
   nection information, one graph can be built containing all the
   internetwork's interconnections.

   The process of creating this graph is:


   o    Examine the list of connected autonomous systems advertised by
        the current AS.

   o    Examine the ASPolicyCert of each AS the current AS is advertis-
        ing as connected, and determine if that AS is advertising a con-
        nection back to the current AS. This is termed the two way con-
        nectivity check.

   o    If the two way connectivity check passes, the connection SHOULD
        be added to the interconnection graph, and marked as trustable.

   o    If the two way connectivity check fails, the connection MAY be
        added to the interconnection graph, but marked so a lower secu-
        rity preference will be assigned to AS_PATHs traversing this
        link.

   o    Repeat this process for each ASPolicyCert in the authorization
        database.

        The resulting graph is called the internetwork graph.


3.3. Validating Routing Information

   For each prefix within a given BGP UPDATE message:


   o    The local authorization database is examined, and the AuthCert
        with the longest prefix length encompassing the range of
        addresses described by the prefix is chosen.



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   o    If there is no entry in the local authorization database which
        encompasses the range of addresses described by the prefix, then
        the route is said to be unverified, and should be handled
        according to local policy (either discarded, or have its secu-
        rity preference lowered). The rest of this process is ignored in
        these cases.

   o    The second hop in the AS_PATH attribute is examined.

      o    If the second hop in the AS_PATH is advertised as connected
           by the originating AS, the Security Preference for this pre-
           fix SHOULD be increased.

      o    If the second hop in the AS_PATH is not advertised as con-
           nected by the originating AS, the Security Preference for
           this prefix SHOULD be decreased.

      o    If the second hop in the AS_PATH is not advertised as con-
           nected by the originating AS and the originator's policy
           indicates the second hop MUST be validated, the prefix should
           be removed from further consideration.

   o    The AS_PATH attribute is compared to the internetwork graph.

      o    If the AS_PATH described is contained within the internetwork
           graph, the Security Preference SHOULD be increased.

      o    If the AS_PATH described is not contained within the inter-
           network graph, the Security Preference SHOULD be decreased.

      o    If the AS_PATH traverses a connection which is only described
           by one of the two autonomous systems, this is a one way con-
           nection. Local policy may be used to determine if the secu-
           rity preference should be increased in this case.

      o    If the AS_PATH described is not contained within the inter-
           network graph, and the originator indicated the AS_PATH MUST
           be checked, the prefix should be removed from further con-
           sideration.

   o    The AuthCert chosen at the first step is examined.

      o    If the authorized AS in the AuthCert matches the originating
           AS in the AS_PATH, the Security Preference SHOULD be
           increased.

      o    If the authorized AS in the AuthCert does not mathc the ori-
           ginating AS in the AS_PATH, the Security Preference SHOULD be



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           set low enough to cause the route to be discarded.

   o    Other policies contained in the local authorization database
        should be applied as directed by the policy.


3.4. Validating Received BGP UPDATES

   As BGP UPDATES are received, they may be processed in one of several
   ways:


   o    Each prefix may be validated according to the process outlined
        in Validating Routing Information before they are installed in
        the ADj-RIB-IN.

   o    Each prefix may be validated according to the process outlined
        in Validating Routing Information after they are installed in
        the Adj-RIB-In, but before they are considered in the BGP Best
        Path calculation.

   o    Each prefix may be validated according to the process outlined
        in Validating Routing Information after they are run through the
        Best Path algorithm, but before they are installed in the local
        RIB.

   o    Routes may be installed in the local RIB, and then validated
        using the process outlined in Validating Routing Information.
        Once validation is accomplished, adjustments to the local RIB
        and routes advertised to BGP peers may need to be adjusted.


3.5. Aggregation

   Aggregation is a difficult problem with any method which attempts to
   verify the origin of any given prefix, since aggregation removes the
   relationship between prefixes originated and originators. Prefixes
   may only be aggregated by an entity which is otherwise authorized to
   advertise the aggregated prefix.


3.6. Requirements for Systems Running soBGP

   This section describes requirements for autonomous systems running
   soBGP, requirements for BGP speakers forming external adjacencies
   from within such autonomous systems, and devices exchanging soBGP
   certificates.




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   o    Any peering session along the border of an autonomous system
        running soBGP SHOULD be authenticated through some means such as
        [BGP-MD5], IPsec ([ESP], [AH]), or through some other current,
        effective means of protecting BGP sessions from being hijacked,
        or otherwise abused.

   o    Any peering session along which soBGP certificates are exchanged
        SHOULD be authenticated through some means such as [BGP-MD5],
        IPsec ([ESP, [AH]), or through some other current, effective
        means of protecting BGP sessions from being hijacked, or other-
        wise abused.

   o    The AS_PATH of any routing information received from any BGP
        peer outside the autonomous system MUST be checked to validate
        the next hop AS is the AS the update was received from. If the
        next hop AS in any received update does not match the configured
        AS the route is learned from, the update MUST be discarded.


4. soBGP Deployment

   This section begins by describing what we believe to be the most
   practical deployment of this secure registry of routing information.
   Following sections describe some other deployment options that may
   prove useful in some situations, or may prove to be more practical
   than the deployment outlined in this section.


4.1. Deploying soBGP on Distributed Registry Servers

   This deployment scenerio works within three constraints:


   o    It may not be not desirable to combine routing and cryptographic
        processing of soBGP certificates on the same device.

   o    The system should be distributed, using as few centralized
        resources as possible.

   o    Trust relationships should be based on existing business and
        working relationships, rather than building new relationships
        specifically for securing the routing system.

   Assume we have a small internetwork, as shown below:

     S1 - - - - - - - - - - -S2 - - - -S3

     10.1.1.0/24---A---B-----C---D-----E---F



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   | AS65000              | AS65001 | AS65002


   In this network, we assume each AS has an soBGP server locally within
   their AS, marked as S1, S2, and S3, above. These servers are inter-
   connected in a way similar to eBGP peering between AS65000, AS65001,
   and AS65002; S1 and S2 are using the mechanisms described in [SOBGP-
   BGPEXT] to distribute the certificates described in [SOBGP-
   CERTIFICATE] between them.

   Each server then processes the certificates as described in [SOBGP-
   CERTIFICATE], and either provides a set of filters or a mechanism
   through which the eBGP peering routers can authenticate routing
   information, such as described in [SOBGP-RADIUS]. This deployment
   technique provides BGP route validation that is:


   o    Fully Distributed: Local server (or set of servers) which builds
        the required databases based on received certificates, and dis-
        tributes certificates throughout the routing system.

   o    Locally Controlled: Each local server (or set of server) is
        maintained and managed by autonomous systems participating in
        the internetwork.

   o    Based on Existing Business Relationships: Peering autonomous
        systems also peer their soBGP servers, so the system uses exist-
        ing business relationships to provide the deployment and long
        term maintenance of the system.

   o    Very Little Impact on the Existing Routing System: The current
        processing and distribution of routing information through [BGP]
        isn't impacted in any way.  The only additional requirements on
        existing equipment are to compare the routing information to the
        database results provided by the local servers (i.e., receiving
        and processing filter lists, or through [SOBGP-RADIUS]).


4.2. Certificate Processing on Edge Peering Routers

   soBGP can also be deployed entirely within BGP speakers at the edge
   of an Autonomous System (AS).

   +-(eBGP)-+           +-(eBGP)-+
   |        |           |        |
   v        v           v        V

   A--------B-----C-----D--------E



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            ^           ^
            |           |
            +--(iBGP)---+

   In this network, A is sending certificates it has learned from other
   sources to B using the mechanisms described in [SOBGP-BGPEXT]. It is
   passing these certificates to D via iBGP, and D is passing these cer-
   tificates to E via eBGP. Each edge router, B and D, process these
   certificates locally, building the databases required to validate
   received routing information from them.


4.3. Multihoming Deployment

   Multihoming presents a special challenge to the deployment of soBGP
   within a large scale internetwork.

     (---------)            (---------)
    (  AS65401  )          (  AS65402  )
   (             )        (             )
    (           )          (           )
      (---A---)              (---B---)
          |                      |
           \                    /
            \-----+      +-----/
                  |      |
               (--C------D--)
              (              )
               (   No-AS    )
                (----------)

   Assume No-AS has obtained a block of addresses, 10.1.1.0/24, from
   AS65401, and would like to advertise that same block of addresses
   through AS65402. Since No-AS has no AS number, it cannot generate any
   soBGP certificates, and must rely on its upstream providers to work
   out the security impact in some way. The simplest solution would be,
   of course, for NOAS to obtain an AS number, and fully participate in
   soBGP, but barring that, what other solutions are there?

   AS65401 could issue a certificate allowing AS65402 to originate just
   the prefix in question, 10.1.1.0/24, or AS65401 could simply list
   AS65402 in the certificate covering 10.1.1.0/24 as an authorized ori-
   ginator for this address space (as multiple authorized originators
   are allowed).







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4.4. Proxy Advertisement of Certificates

   Note there is no requirement for a given entity which originates
   routes into the routing system to actually originate the correspond-
   ing certificates required for the correct origination of the route to
   be validated, and the AS Path attached to the route to be verified.

             (-----------------)
            ( Other Third Party )
              (---------------)
               /             \
              /               \
     (---------)            (---------)
    (  AS65401  )          (  AS65402  )
   (             )        (             )
    (           )          (           )
      (---A---)              (---B---)
          |                      |
           \                    /
            \-----+      +-----/
                  |      |
               (--C------D--)
              (              )
               (  AS65403   )
                (----------)

   In this case, AS65401, AS65402, or some other third part may actually
   advertise the certificates necessary for AS65403 to originate vali-
   dated routes.


5. Other Deployment Considerations

   In this section, we move from specific deployment scenerios to other
   deployment considerations, such as key generation and protection, and
   memory utilization/impact.


5.1. Certificate Generation and Private Key Protection

   There is only one private/public key pair per autonomous system; cer-
   tificates are generated as determined by local policy and as required
   to account for changes in the network. Since the entity's private key
   is not used in any part of the operations verifying received informa-
   tion, or in generating information to transmit to other devices,
   these certificates could be generated on some secure central system
   in the AS, and the results, containing only public keys, can be
   transmitted throughout the network.



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   Securing the private key of each entity should be relatively easy in
   this environment, since the location of the private key can be care-
   fully constrained; no device other than the system which generates
   the required certificates needs use of the private key.


5.2. Impact on Performance and Memory Utilization

   Detailed performance and memory utilization characteristics of soBGP
   will be the subject of future investigation. However, as this is an
   important area of consideration, we present some suggested analysis
   below. (In other words, this is a guess).

   In terms of memory, each device running sobGP will need to store:

   o    Each of the Entitycerts Received. The maximum number of Enti-
        tycerts within the routing system would be the number partici-
        pating autonomous systems multiplied by the number of outstand-
        ing Entitycerts from each autonomous system.

   o    Each of the ASPolicycerts Received. The number of ASPolicycerts
        within the system will probably be similar to the number of
        Entitycerts within the system.

   o    Each of the PrefixPolicycerts Received. The number of PrefixPol-
        icyCerts within the system will depend on the number of address
        blocks each participant in the routing system advertises, and
        could double during key rollover.

   Performance will depend on the cryptographic processing requirements
   imposed by the certificate signature methods, as described in
   [SOBGP-CERTIFICATE]. However, all of this additional memory and pro-
   cessing would most likely be required on a distributed soBGP server,
   rather than on routers themselves.

   The primary impact on routers and routing protocol convergence will
   be the memory and processing requirements added from the additional
   route filters or processing as required by the deployment technique
   used.












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6. Normative References


   [BGP] Rekhter, Y., and T. Li, "A Border Gateway Protocol 4 (BGP-4)",
        RFC 1771, March 1995.

   [SOBGP-BGPEXT]
        Ng J (editor), "Extensions to BGP to Support Secure Origin BGP
        (soBGP)",  draft-ng-sobgp-bgp-extensions-01.txt, April 2004

   [SOBGP-CERTIFICATE]
        Weis, Brian (editor), "Secure Origin BGP (soBGP) Certificates",
        draft-weis-sobgp-certificates-01.txt, October 2003


7. Informative References


[SOBGP-RADIUS]
     Lovnick, C, "RADIUS Attributes for soBGP Support", draft-lonvick-
     sobgp-radius-04.txt, February 2004

[PATH-CONSIDER]
     White, Russ, "Considerations in Validating the Path in Routing Pro-
     tocols", draft-white-pathconsiderations-02.txt, April 2004

[COST]
     Retana, A., White, R., "BGP Custom Decision Process", draft-
     retana-bgp-custom-decision-00, October 2002.


8. Editor's Address

   Russ White
   Cisco Systems
   7025 Kit Creek Road
   Research Triangle Park, NC 27709
   riw@cisco.com













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Network Working Group                                           James Ng
Internet Draft                                                  (editor)
Expiration Date: October 2004                              Cisco Systems
File Name: draft-ng-sobgp-bgpextensions-00.txt                April 2004

             Extensions to BGP Transport soBGP Certificates
                  draft-ng-sobgp-bgpextensions-00.txt

   Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   Internet Drafts are working documents of the Internet Engineering
   Task Force (IETF), its Areas, and its Working Groups. Note that other
   groups may also distribute working documents as Internet Drafts.

   Internet Drafts are draft documents valid for a maximum of six
   months.  Internet Drafts may be updated, replaced, or obsoleted by
   other documents at any time. It is not appropriate to use Internet
   Drafts as reference material or to cite them other than as a "working
   draft" or "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.


1. Contributors

   A large number of people contributed to or provided valuable feedback
   on this document; we've tried to include all of them here (in no
   particular order), but might have missed a few: Russ White, Alvaro
   Retana, Dave Cook, John Scudder, David Ward, Martin Djernaes, Chris
   Lonvick, Brian Weis, Tim Gage, Scott Fanning, Barry Friedman, Jim
   Duncan, Yi Yang, Robert Adams, Tony Tauber, Iljitsch van Beijnum, and
   Jonathan Natale.












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2. Abstract

   There is a great deal of concern over the security of routing systems
   within the Internet, particularly in relation to the Border Gateway
   Protocol [BGP], which is used to provide routing information between
   autonomous systems. This document proposes a system where the origin
   of any advertisement within BGP can be verified and authenticated,
   preventing the advertisement of prefix blocks by unauthorized
   networks, verifying that the final destination in the path is
   actually within the autonomous system to which the packets are being
   routed, and proving the validity of the AS Path contained in the
   update.

   This document does not:

   o    Attempt to provide information on how such a security system
        could or should be deployed; readers are referenced to [SOBGP-
        ARCH] for this discussion.

   o    Attempt to determine what sorts of keys should be used within
        such a system, nor how any sort of trust relationship can or
        should be built between the entities cooperating within the
        routing system. These are considered in [SOBGP-CERTIFICATE].

   o    Attempt to analyse the performance, memory utilization, or other
        impacts on devices running this protocol; these are addressed in
        [SOBGP-ARCH].

   o    Attempt to analyze the security protection provided by the pro-
        posed security system. This may be address in a future draft.

   This document primarily focuses on extensions to the BGP protocol
   itself to support such a security system through the transport of the
   certificates described in [SOBGP-CERTIFICATE].

   The IETF has been notified of intellectual property rights claimed in
   regard to some or all of the specification contained in this docu-
   ment. For more information consult the online list of claimed rights.













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3. Definitions


   o    Entity: A participant in the internetwork routing system.


4. The Security Message

   This document proposes a new message type, the SECURITY message,
   which is to be used for carrying security information within the BGP
   protocol. The SECURITY message is type [TBD]. The SECURITY message is
   used to transport the certificates described in [SOBGP-CERTIFICATE].


4.1. Negotiating Security Capability

   The ability to exchange SECURITY messages MAY be negotiated at ses-
   sion startup, as described in [CAPABILITY]. The capability code is
   <to be assigned by IANA>.


   o    Speakers MAY negotiate the exchange of SECURITY information only
        or SECURITY and NLRIs.

   o    If the exchange of SECURITY messages is negotiated, the SECURITY
        option message MUST be exchanged before any other SECURITY mes-
        sages are exchanged. The option bits in this message determine
        if SECURITY messages or NLRIs will be exchanged first.

   o    If two BGP speakers have negotiated to exchange SECURITY mes-
        sages, they SHOULD exchange the soBGP certificates contained in
        their local databases.


4.2. The Security Message Format

   The SECURITY message is formatted as described in [BGP], with a type
   code of [TBD]. Within each message is a series of TLVs, or security
   message blocks, formatted as:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-------------------------------+-------------------------------+
   | Type                          | Length                        |
   +-------------------------------+-------------------------------+
   | Data                                                          |
   +---------




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   o    Type: A two octet unsigned integer describing the type of infor-
        mation contained within the data field.

   o    Length: A two octet unsigned integer describing the length of
        the data field, in octets.

   o    Data: The data, as described within this and other documents
        which describe information to be carried within the SECURITY
        message type.

      Two TLVs are currently defined within the SECURITY message.
      Further TLVs are defined for carrying certificates in [SOBGP-
      CERTIFICATE].


4.2.1. The SECURITY Option TLV

   The SECURITY Option TLV provides a way for exchanging speakers to
   inform their peers about local configurations which may pertain to
   the peering session. SECURITY Option TLVs are encapsulated within a
   TLV Type 1, and transmitted within the SECURITY message type.

   If SECURITY Option TLVs are transmitted, they MUST be transmitted
   before the transmission of any other SECURITY data.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-------------------------------+-------------------------------+
   | TLV Type                      | Length                        |
   +-------------------------------+-------------------------------+
   | Options                                                       |
   +---------------------------------------------------------------+

   o    TLV type: (2 octets), 1 (0x0001)

   o    Length: (2 octets), set to 2

   o    Options: (4 octets), a bitfield, described below

   The options field is a 32 bit bitfield, allowing up to 32 different
   options to be specified.

   o    Bit 0: If set, indicates that SECURITY information should be
        sent before NLRI information on this session; if cleared, indi-
        cates that NLRI information should be sent before SECURITY
        information.

   o    Bit 1: If set, indicates that this peer will only transmit



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        validated certificates of any type along this session. This bit
        MUST NOT be used for eBGP sessions.

   o    Bit 2: If set, indicates that this peer will only accept vali-
        dated certificates of any type along this session (valid only on
        iBGP sessions).

   Bit 0 in the option field allows the operator to configure the local
   device so it receives all prefixes first, decreasing convergence to
   the minimum time, or receives all SECURITY information first, allow-
   ing all prefixes to be validated before they are installed.

   Bits 1 and 2 allow peers along an iBGP session to trust the certifi-
   cations they receive without validating them. If bit 1 is set on the
   transmitting peer, bit 2 is set on the receiving peer, and the BGP
   peering session is an authenticated or encrypted iBGP session, the
   receiving peer may accept all received certificates from the
   transmitting peer as already validated. This is called a trusted
   peering relationship.


4.2.2. The Request TLV

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-------------------------------+-------------------------------+
   | TLV Type                      | Length                        |
   +-------------------------------+-------------------------------+
   | Request Type                  | Length                        |
   +-------------------------------+-------------------------------+
   | Request Indicator SubTV ....                                  |
   +---------------------------
   | Request Type                  | Length                        |
   +-------------------------------+-------------------------------+
   | Request Indicator SubTV ....                                  |
   +---------------------------

   o    TLV type: (2 octets), 2

   o    Length: (2 octets), set to the total length of the request in
        octets.

   o    Request Type: (2 octets), treated as an unsigned integer indi-
        cating the type of information requested.

   o    Length: (2 octets), set to the number of requests of the request
        type included in this request.




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   o    Reserved: (2 octets), set to 0x0000.

   o    Request Indicator: The information indicated by the request type
        bit field.

   The Request Type field indicates the type of certificates requested.
   Four request types are defined in this document.


   1    Any certificate matching the Request Indicator are requested.

   2    EntityCerts matching the Request Indicator are requested.

   3    ASPolicyCerts matching the Request Indicator are requested.

   4    PrefixPolicyCerts matching the Request Indicator are requested.

   Request indicator SubTVs restrict the set of certificates returned;
   there may be one or more request indicator SubTVs included in a
   request. Each SubTV consists of a two octet type field, treated as an
   unsigned integer, and a fixed length field containing the request
   indicator.

   o    Type 1: A four octet origin/authorized AS Number; two octet AS
        numbers shall be right justified within this field (placed in
        the two least significant octets).

   o    Type 2: A four octet signer/authorizer AS Number; two octet AS
        numbers shall be right justified within this field (placed in
        the two least significant octets).

   o    Type 3: A four octet IPv4 address is included in the request
        indicator.

   o    Type 4: A sixteen octet IPv6 address is included in the request
        indicator.

   o    Type 5: An eight octet starting serial number is included in the
        request indicator.

   o    Type 6: An eight octet ending serial number is included in the
        request indicator.









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4.2.3. The Cluster List TLV

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-------------------------------+-------------------------------+
   | TLV Type                      | Length                        |
   +-------------------------------+-------------------------------+
   | Cluster ID                                                    |
   +-------------------------------+-------------------------------+
   | ....                                                          |
   +---------------------------

   o    TLV type: (2 octets), 3

   o    Length: (2 octets), set to the number of cluster IDs in the TLV

   The use of the Cluster List TLV is described in the Reflecting SECU-
   RITY messages section below.


5. Receiving and Processing SECURITY messages

   Each section below describes the receipt and processing of SECURITY
   messages.


5.1. Processing SECURITY Messages Containing a Certificate

   For each certificate received, the BGP speaker MUST:


   o    Examine the certificate to determine if a copy of this certifi-
        cate already exists in the local database.  Any certificate
        which is found to already be held locally MUST be discarded.

   o    If the certificate is received through an untrusted peering
        relationship, place the certificate in a local certificate data-
        base and process according to [SOBGP-CERTIFICATE].

   o    If the certificate is received through a trusted peering rela-
        tionship, place certificate in a local certificate database,
        treating it as if it is already validated according to [SOBGP-
        CERTIFICATE].

   o    If a received certificate is sucessfully validated using the
        process described in [SOBGP-CERTIFICATE], it should be readver-
        tised to all peers outside the local autonomous system (eBGP
        peers). If the peering relationship is trusted, the certificate



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        should be advertised as validated by marking it as indicated in
        [SOBGP-CERTIFICATE].


5.2. Reflecting SECURITY Messages

   A BGP speaker MAY be configured to reflect received SECURITY mes-
   sages, with or without processing them, in a way similar to the way
   BGP routing information is reflected among iBGP speakers, described
   in [BGP-REFLECTION]. When reflecting SECURITY messages, a BGP speaker
   MUST:


   o    Examine the SECURITY message for the presence of a Cluster List
        TLV.

      o    If a Cluster List TLV exists, and the local router ID is con-
           tained in the list of Cluster IDs, discard the SECURITY mes-
           sage.

      o    If a Cluster List TLV exists, and the local router ID is not
           contained in the list of Cluster IDs, add the local router ID
           to the list and retransmit the SECURITY message to all BGP
           peers which have negotiated receipt of SECURITY messages.

      o    If a Cluster List TLV does not exist, add a new Cluster List
           TLV to the SECURITY message, including the local router ID in
           the new TLV.


5.3. Filtering of Certificates

   A BGP speaker may, for reasons of policy, filter soBGP certificates
   received from a peer.


   o    If a BGP speaker is part of a transit AS, it SHOULD NOT filter
        soBGP certificates.

   o    A BGP speaker MAY discard soBGP certificates which describe the
        authorization of address space which is being filtered out of
        the local routing information.









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5.4. Receiving and Processing Requests

   If a device receives a Request TLV, as described in the section "The
   Security Message," above, it should:

   o    Examine the request to ensure it is logically consistent. For
        instance, requesting an Entitycert based on an IPv4 address
        range is not logically consistent, since these certificates only
        contain an AS and a Signer AS.  If the request is not logically
        consistent, discard it.

   o    If the request is logically consistent, examine its local data-
        bases, and transmit the certificates requested which fulfill the
        conditions supplied in the request indicator SubTVs.

   o    If more than one of the same request indicator is included in a
        request message, they shall be treated as an OR condition; if
        any of the conditions match, the certificate shall match the
        set.


6. Security Considerations

   This document defines extensions to BGP that address specific secu-
   rity concerns for the protocol.  While it adds functionality, the
   flexibility allows it to not introduce any new security concerns.


7. IANA Considerations

   This document defines the Security Message for BGP, which contains a
   series of TLVs.  IANA is expected to maintain a registry of all the
   values defined, as follows:

   The SECURITY message Type field :

   o    Type value 0 is reserved.

   o    Type values 1 through 3 are assigned in this document.

   o    Type values 4 through 16575 MUST be assigned using the "IETF
        Consensus" policy defined in RFC2434 [RFC2434].

   o    Type values 16576 through 32895 SHOULD be assigned using the
        "Specification Required" policy defined in RFC2434 [RFC2434].

   o    Type values 32896 through 65535 are for "Private Use" as defined
        in RFC2434 [RFC2434].



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   Request TLV Request Type Field:

   o    Types 1 through 3 are assigned in this document.

   o    Types 4 thru 16575 MUST be assigned using the "IETF Consensus"
        policy defined in RFC2434 [RFC2434].

   o    Type values 16576 through 32895 SHOULD be assigned using the
        "Specification Required" policy defined in RFC2434 [RFC2434].

   o    Type values 32896 through 65535 are for "Private Use" as defined
        in RFC2434 [RFC2434].


8. Normative References

   [BGP] Rekhter, Y., and T. Li, "A Border Gateway Protocol 4 (BGP-4)",
        RFC 1771, March 1995.

   [MULTIPROTOCOL-BGP]
        Bates, T., Chandra, R., Katz, D., and Rekhter, Y., "Multiproto-
        col Extensions for BGP-4", RFC 2858, June 2000

   [CAPABILITY]
        Chandra, R., Scudder, J., "Capabilities Advertisement with BGP-
        4", RFC2842, May 2000

   [SOBGP-ARCH]
        White, R. (editor), "Architecture and Deployment Considerations
        for Secure Origin BGP (soBGP)", draft-white-sobgp-deployment-03,
        April 2004

   [SOBGP-CERTIFICATE]
        Weis, Brian (editor), "Secure Origin BGP (soBGP) Certificates",
        draft-weis-sobgp-certificates-01.txt, October 2003
















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9. Informative References

[RFC2434]
     Narten, T., Alvestrand, H., "Guidelines for Writing an IANA Con-
     siderations Section in RFCs", RFC 2434, October 1998.

[BGP-MD5]
     Heffernan, A., "Protection of BGP Sessions via the TCP MD5 Signa-
     ture Option", RFC2385, August 1998

[ESP] Kent, S., and R. Atkinson, "IP Encapsulating Security Payload",
     RFC 2406, November 1998.

[AH] Kent, S., and R. Atkinson, "IP Authentication Header", RFC 2402,
     November 1998.

[SOBGP-RADIUS]
     Lovnick, C, "RADIUS Attributes for soBGP Support", draft-lonvick-
     sobgp-radius-04.txt, February 2004

[BGP-REFLECTION]
     Bates, T, et al, "BGP Route Reflection - An Alternative to Full
     Mesh IBGP", draft-ietf-idr-rfc2796bis-00.txt, March 2004


10. Editor's Address

   James Ng (Editor)
   Cisco Systems
   7025 Kit Creek Road
   Research Triangle Park, NC 27709
   jamng@cisco.com



















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