BGP Monitoring Protocol
draft-ietf-grow-bmp-06

Network Working Group                                         J. Scudder
Internet-Draft                                          Juniper Networks
Intended status: Standards Track                             R. Fernando
Expires: June 2, 2012                                      Cisco Systems
                                                               S. Stuart
                                                                  Google
                                                       November 30, 2011

                        BGP Monitoring Protocol
                         draft-ietf-grow-bmp-06

Abstract

   This document proposes a simple protocol, BMP, which can be used to
   monitor BGP sessions.  BMP is intended to provide a more convenient
   interface for obtaining route views for research purpose than the
   screen-scraping approach in common use today.  The design goals are
   to keep BMP simple, useful, easily implemented, and minimally
   service-affecting.  BMP is not suitable for use as a routing
   protocol.

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 June 2, 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
   publication of this document.  Please review these documents

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   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.

   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008.  The person(s) controlling the copyright in some of this
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   it for publication as an RFC or to translate it into languages other
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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1.  Requirements Language  . . . . . . . . . . . . . . . . . .  5
   2.  Lifecycle of a BMP Session . . . . . . . . . . . . . . . . . .  5
   3.  BMP Message Format . . . . . . . . . . . . . . . . . . . . . .  5
     3.1.  Common Header  . . . . . . . . . . . . . . . . . . . . . .  5
     3.2.  Per-Peer Header  . . . . . . . . . . . . . . . . . . . . .  6
     3.3.  Initiation Message . . . . . . . . . . . . . . . . . . . .  8
     3.4.  Route Monitoring . . . . . . . . . . . . . . . . . . . . .  9
     3.5.  Stats Reports  . . . . . . . . . . . . . . . . . . . . . .  9
     3.6.  Peer Down Notification . . . . . . . . . . . . . . . . . . 10
     3.7.  Peer Up Notification . . . . . . . . . . . . . . . . . . . 11
   4.  Route Monitoring . . . . . . . . . . . . . . . . . . . . . . . 12
   5.  Stat Reports . . . . . . . . . . . . . . . . . . . . . . . . . 13
   6.  Other Considerations . . . . . . . . . . . . . . . . . . . . . 13
   7.  Using BMP  . . . . . . . . . . . . . . . . . . . . . . . . . . 14
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 14
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 15
   10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 15
   11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
     11.1. Normative References . . . . . . . . . . . . . . . . . . . 15
     11.2. Informative References . . . . . . . . . . . . . . . . . . 16
   Appendix A.  Changes Between BMP Versions 1 and 2  . . . . . . . . 16
   Appendix B.  Changes Between BMP Versions 2 and 3  . . . . . . . . 16
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16

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1.  Introduction

   Many researchers wish to have access to the contents of routers' BGP
   RIBs as well as a view of protocol updates that the router is
   receiving.  This monitoring task cannot be realized by standard
   protocol mechanisms.  At present, this data can only be obtained
   through screen-scraping.

   The BMP protocol provides access to the Adj-RIB-In of a peer on an
   ongoing basis and a periodic dump of certain statistics that the
   monitoring station can use for further analysis.  The following are
   the messages provided by BMP.

   o  Route Monitoring (RM): An initial dump of all routes received from
      a peer as well as an ongoing mechanism that sends the incremental
      routes advertised and withdrawn by a peer to the monitoring
      station.

   o  Peer Down Notification (PD): A message sent to indicate that a
      peering session has gone down with information indicating the
      reason for the session disconnect.

   o  Stats Reports (SR): This is an ongoing dump of statistics that can
      be used by the monitoring station as a high level indication of
      the activity going on in the router.

   o  Peer Up Notification (PU): A message sent to indicate that a
      peering session has come up.  The message includes information
      regarding the data exchanged between the peers in their OPEN
      messages as well as information about the peering TCP session
      itself.  In addition to being sent whenever a peer transitions to
      ESTABLISHED state, a Peer Up Notification is sent for each peer
      that is in ESTABLISHED state when the BMP session itself comes up.

   BMP operates over TCP.  All options are controlled by configuration
   on the monitored router.  No message is ever sent from the monitoring
   station to the monitored router.  The monitored router MAY take steps
   to prevent the monitoring station from sending data (e.g. by half-
   closing the TCP session or setting its window size to zero) or it MAY
   silently discard any data erroneously sent by the monitoring station.

   The monitoring station is configured to listen on a particular TCP
   port and the router is configured to establish an active connection
   to that port and to send messages on that TCP connection.  There is
   no initialization or handshaking phase, messages are simply sent as
   soon as the connection is established.  If the router is unable to
   connect to the monitoring station, it periodically retries the
   connection.  A suggested default retry period is 30 seconds.

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   If the monitoring station intends to restart BMP processing, it
   simply drops the connection.  The router then re-establishes the
   connection and resends the messages.

1.1.  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 [RFC2119].

2.  Lifecycle of a BMP Session

   A BMP session begins when a router running BMP successfully opens a
   TCP session (the "BMP session") to the monitoring station it is
   configured to talk to.  It MAY first send an Initiation message.  It
   subsequently sends a Peer Up message over the BMP session for each of
   its BGP peers which are in Established state.  It follows by sending
   the contents of its Adj-RIBs-In (or Loc-RIB, see Section 4)
   encapsulated in Route Monitoring messages.  Once it has sent all the
   routes for a given peer, it sends an End-of-RIB message for that
   peer; when End-of-RIB has been sent for each peer, the initial table
   dump has completed.  (A monitoring station that wishes only to gather
   a table dump could close the connection once it has gathered an End-
   of-RIB or Peer Down message corresponding to each Peer Up message.)

   Following the initial table dump, the router sends incremental
   updates encapsulated in Route Monitoring messages.  It MAY
   periodically send Stats Reports or even new Initiation messages,
   according to configuration.  If any new BGP peers become Established,
   corresponding Peer Up messages are sent.  If any BGP peers for which
   Peer Up messages were sent transition out of the Established state,
   corresponding Peer Down messages are sent.

   A BMP session ends when the TCP session that carries it is closed for
   any reason.

3.  BMP Message Format

3.1.  Common Header

   The following common header appears in all BMP messages.  The rest of
   the data in a BMP message is dependent on the "Message Type" field in
   the common header.

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     0 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8
     +-+-+-+-+-+-+-+-+
     |    Version    |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                        Message Length                         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |   Msg. Type   |
     +---------------+

   o  Version (1 byte): Indicates the BMP version.  This is set to '3'
      for all messages defined in this specification.  Version 0 is
      reserved and MUST NOT be sent.

   o  Message Length (4 bytes): Length of the message in bytes
      (including headers, data and encapsulated messages, if any).

   o  Message Type (1 byte): This identifies the type of the BMP
      message.  A BMP implementation MUST ignore unrecognized message
      types upon receipt.

      *  Type = 0: Route Monitoring
      *  Type = 1: Statistics Report
      *  Type = 2: Peer Down Notification
      *  Type = 3: Peer Up Notification
      *  Type = 4: Initiation Message

3.2.  Per-Peer Header

   The per-peer header follows the common header for most BMP messages.
   The rest of the data in a BMP message is dependent on the "Message
   Type" field in the common header.

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     0 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |   Peer Type   |  Peer Flags   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |         Peer Distinguisher (present based on peer type)       |
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                 Peer Address (16 bytes)                       |
     ~                                                               ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                           Peer AS                             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                         Peer BGP ID                           |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                    Timestamp (seconds)                        |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                  Timestamp (microseconds)                     |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   o  Peer Type (1 byte): These bits identify the type of the peer.
      Currently only two types of peers are identified,

      *  Peer Type = 0: Global Instance Peer
      *  Peer Type = 1: L3 VPN Instance Peer

   o  Peer Flags (1 byte): These flags provide more information about
      the peer.  The flags are defined as follows.

                             0 1 2 3 4 5 6 7 8
                             +-+-+-+-+-+-+-+-+
                             |V|L| Reserved  |
                             +-+-+-+-+-+-+-+-+

      *  The V flag indicates the the Peer address is an IPv6 address.
         For IPv4 peers this is set to 0.
      *  The L flag, if set to 1, indicates that the message reflects
         the Loc-RIB (i.e., it reflects the application of inbound
         policy).  It is set to 0 if the message reflects the
         Adj-RIB-In.  See Section 4 for further detail.
      *  The remaining bits are reserved for future use.

   o  Peer Distinguisher (8 bytes): Routers today can have multiple
      instances (example L3VPNs).  This field is present to distinguish
      peers that belong to one address domain from the other.

      If the peer is a "Global Instance Peer", this field is zero

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      filled.  If the peer is a "L3VPN Instance Peer", it is set to the
      route distinguisher of the particular L3VPN instance that the peer
      belongs to.

   o  Peer Address: The remote IP address associated with the TCP
      session over which the encapsulated PDU was received.  It is 4
      bytes long if an IPv4 address is carried in this field (with most
      significant bytes zero filled) and 16 bytes long if an IPv6
      address is carried in this field.

   o  Peer AS: The Autonomous System number of the peer from which the
      encapsulated PDU was received.  If a 16 bit AS number is stored in
      this field [RFC4893], it should be padded with zeroes in the most
      significant bits.

   o  Peer BGP ID: The BGP Identifier of the peer from which the
      encapsulated PDU was received.

   o  Timestamp: The time when the encapsulated routes were received
      (one may also think of this as the time when they were installed
      in the Adj-RIB-In), expressed in seconds and microseconds since
      midnight (zero hour), January 1, 1970 (UTC).  If zero, the time is
      unavailable.  Precision of the timestamp is implementation-
      dependent.

3.3.  Initiation Message

   The initiation message provides a means for the monitored router to
   inform the monitoring station of its vendor, software version, and so
   on.  The initiation message is OPTIONAL.  When used, an initiation
   message MUST be sent as the first message after the TCP session comes
   up.  An initiation message MAY be sent at any point thereafter, if
   warranted by a change on the monitored router.

   The initiation message consists of the common BMP header followed by
   one or more TLVs containing information about the monitored router,
   as follows:

     0 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |          Information Type     |       Information Length      |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                 Information (variable)                        |
     ~                                                               ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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   o  Information Type (2 bytes): Type of information provided.  Defined
      types are:

      *  Type = 0: String.  The Information field contains a free-form
         UTF-8 string whose length is given by the "Information Length"
         field.

   o  Information Length (2 bytes): The length of the following
      Information field, in bytes.

   o  Information (variable): Information about the monitored router,
      according to the type.

3.4.  Route Monitoring

   Route Monitoring messages are used for initial synchronization of
   ADJ-RIB-In.  They are also used for ongoing monitoring of received
   advertisements and withdraws.  This is discussed in more detail in
   subsequent sections.

   Following the common BMP header and per-peer header is a BGP PDU.

3.5.  Stats Reports

   These messages contain information that could be used by the
   monitoring station to observe interesting events that occur on the
   router.  'Stats Report' messages have a message type of '3'.

   The transmission of the SR messages could be timer triggered or event
   driven (for example, when a significant event occurs or a threshold
   is reached).  This specification does not impose any timing
   restrictions on when and on what event these reports have to be
   transmitted.  It is left to the implementation to determine
   transmission timings -- however, configuration control should be
   provided of the timer and/or threshold values.  This document only
   specifies the form and content of SR messages.

   Following the common BMP header and per-peer header is a 4-byte field
   that indicates the number of counters in the stats message where each
   counter is encoded as a TLV.

     0 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                        Stats Count                            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Each counter is encoded as follows,

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     0 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |         Stat Type             |          Stat Len             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                        Stat Data                              |
     ~                                                               ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   o  Stat Type (2 bytes): Defines the type of the statistic carried in
      the "Stat Data" field.

   o  Stat Len (2 bytes): Defines the length of the "Stat Data" Field.

   This specification defines the following statistics.  All statistics
   are 4-byte quantities and the stats data are counters.  A BMP
   implementation MUST ignore unrecognized stat types on receipt, and
   likewise MUST ignore unexpected data in the Stat Data field.

   o  Stat Type = 0: Number of prefixes rejected by inbound policy.

   o  Stat Type = 1: Number of (known) duplicate prefix advertisements.

   o  Stat Type = 2: Number of (known) duplicate withdraws.

   o  Stat Type = 3: Number of updates invalidated due to CLUSTER_LIST
      loop.

   o  Stat Type = 4: Number of updates invalidated due to AS_PATH loop.

   o  Stat Type = 5: Number of updates invalidated due to ORIGINATOR_ID.

   o  Stat Type = 6: Number of updates invalidated due to AS_CONFED
      loop.

   Note that the current specification only specifies 4-byte counters as
   "Stat Data".  This does not preclude future versions from
   incorporating more complex TLV-type "Stat Data" (for example, one
   which can carry prefix specific data).  SR messages are optional.
   However if an SR message is transmitted, this specification requires
   at least one statistic to be carried in it.

3.6.  Peer Down Notification

   This message is used to indicate that a peering session was
   terminated.  The type of this message is 4.

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     0 1 2 3 4 5 6 7 8
     +-+-+-+-+-+-+-+-+
     |    Reason     | 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |            Data (present if Reason = 1, 2 or 3)               |
     ~                                                               ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Reason indicates why the session was closed.  Defined values are:

   o  Reason 1: The local system closed the session.  Following the
      Reason is a BGP PDU containing a BGP NOTIFICATION message that
      would have been sent to the peer.

   o  Reason 2: The local system closed the session.  No notification
      message was sent.  Following the reason code is a two-byte field
      containing the code corresponding to the FSM Event which caused
      the system to close the session (see Section 8.1 of [RFC4271]).
      Zero is used to indicate that no relevant Event code is defined.

   o  Reason 3: The remote system closed the session with a notification
      message.  Following the Reason is a BGP PDU containing the BGP
      NOTIFICATION message as received from the peer.

   o  Reason 4: The remote system closed the session without a
      notification message.

3.7.  Peer Up Notification

   The Peer Up message is used to indicate that a peering session has
   come up (i.e., has transitioned into ESTABLISHED state).  Following
   the common BMP header and per-peer header is the following:

     0 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                 Local Address (16 bytes)                      |
     ~                                                               ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |         Local Port            |        Remote Port            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                    Sent OPEN Message                          |
     ~                                                               ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                  Received OPEN Message                        |
     ~                                                               ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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   o  Local Address: The local IP address associated with the peering
      TCP session.  It is 4 bytes long if an IPv4 address is carried in
      this field, as determined by the V flag (with most significant
      bytes zero filled) and 16 bytes long if an IPv6 address is carried
      in this field.

   o  Local Port: The local port number associated with the peering TCP
      session.

   o  Remote Port: The remote port number associated with the peering
      TCP session.  (Note that the remote address can be found in the
      Peer Address field of the fixed header.)

   o  Sent OPEN Message: The full OPEN message transmitted by the
      monitored router to its peer.

   o  Received OPEN Message: The full OPEN message received by the
      monitored router from its peer.

4.  Route Monitoring

   After the BMP session is up, Route Monitoring messages are used to
   provide a snapshot of the Adj-RIB-In of a particular peer.  This is
   done by sending all routes stored in the Adj-RIB-In of that peer
   using standard BGP Update messages.  There is no requirement on the
   ordering of messages in the peer dump.  When the initial peer dump is
   completed, this MUST be indicated by sending an End-of-RIB marker (as
   specified in Section 2 of [RFC4724], plus the BMP encapsulation
   header).

   Depending on the implementation or configuration, it may only be
   possible to send the Loc-RIB (post-policy routes) instead of the Adj-
   RIB-In.  This is because it is possible that a BGP implementation may
   not store, for example, routes which have been filtered out by
   policy.  If this is the case, the implementation may send the Loc-RIB
   path that pertains to a particular peer in the route monitor message.
   Such paths MUST have the L flag set in the BMP header (see
   Section 3).

   If the implementation is able to provide information about when
   routes were received, it MAY provide such information in the BMP
   timestamp field.  Otherwise, the BMP timestamp field MUST be set to
   zero, indicating that time is not available.

   AS Numbers in the BMP UPDATE message MUST be sent as 4-octet
   quantities, as described in [RFC4893].  This affects the AS_PATH and
   AGGREGATOR path attributes.  AS4_PATH or AS4_AGGREGATOR path

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   attributes MUST NOT be sent in a BMP UPDATE message, as it makes no
   sense to do so.

   Ongoing monitoring is accomplished by propagating route changes in
   BGP UPDATE PDUs and forwarding those PDUs to the monitoring station,
   again using RM messages.  When a change occurs to a route, such as an
   attribute change, the router must update the monitor with the new
   attribute.  When a route is withdrawn by a peer, a corresponding
   withdraw is sent to the monitor.  Multiple changed routes MAY be
   grouped into a single BGP UPDATE PDU when feasible, exactly as in the
   standard BGP protocol.

   It's important to note that RM messages are not real time replicated
   messages received from a peer.  While the router should attempt to
   generate updates as soon as they are received there is a finite time
   that could elapse between reception of an update and the generation
   an RM message and its transmission to the monitoring station.  If
   there are state changes in the interim for that prefix, it is
   acceptable that the router generate the final state of that prefix to
   the monitoring station.  The actual PDU generated and transmitted to
   the station might also differ from the exact PDU received from the
   peer, for example due to differences between how different
   implementations format path attributes.

5.  Stat Reports

   As outlined above, SR messages are used to monitor specific events
   and counters on the monitored router.  One type of monitoring could
   be to find out if there are an undue number of route advertisements
   and withdraws happening (churn) on the monitored router.  Another
   metric is to evaluate the number of looped AS-Paths on the router.

   While this document proposes a small set of counters to begin with,
   the authors envision this list may grow in the future with new
   applications that require BMP style monitoring.

6.  Other Considerations

   Some routers may support multiple instances of the BGP protocol, for
   example as "logical routers" or through some other facility.  The BMP
   protocol relates to a single instance of BGP; thus, if a router
   supports multiple BGP instances it should also support multiple BMP
   instances (one per BMP instance).

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7.  Using BMP

   Once the BMP session is established route monitoring starts dumping
   the current snapshot as well as incremental changes simultaneously.

   It is fine to have these operations occur concurrently.  If the
   initial dump visits a route and subsequently a withdraw is received,
   this will be forwarded to the monitoring station which would have to
   correlate and reflect the deletion of that route in its internal
   state.  This is an operation a monitoring station would need to
   support regardless.

   If the router receives a withdraw for a prefix even before the peer
   dump procedure visits that prefix, then the router would clean up
   that route from its internal state and will not forward it to the
   monitoring station.  In this case, the monitoring station may receive
   a bogus withdraw which it can safely ignore.

8.  IANA Considerations

   This document defines five message types for transferring BGP
   messages between cooperating systems (Section 3):

   o  Type 0: Route Monitor
   o  Type 1: Statistics Report
   o  Type 2: Peer Down Notification
   o  Type 3: Peer Up Notification
   o  Type 4: Initiation

   Type values 5 through 128 MUST be assigned using the "Standards
   Action" policy, and values 129 through 255 using the "Specification
   Required" policy defined in [RFC5226].

   This document defines five statistics types for statistics reporting
   (Section 3.5):

   o  Stat Type = 0: Number of prefixes rejected by inbound policy.
   o  Stat Type = 1: Number of (known) duplicate prefix advertisements.
   o  Stat Type = 2: Number of (known) duplicate withdraws.
   o  Stat Type = 3: Number of updates invalidated due to CLUSTER_LIST
      loop.
   o  Stat Type = 4: Number of updates invalidated due to AS_PATH loop.
   o  Stat Type = 5: Number of updates invalidated due to ORIGINATOR_ID.
   o  Stat Type = 6: Number of updates invalidated due to AS_CONFED
      loop.

   Stat Type values 7 through 32767 MUST be assigned using the

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   "Standards Action" policy, and values 32768 through 65535 using the
   "Specification Required" policy, defined in [RFC5226].

   This document defines one type for information carried in the
   Initiation message (Section 3.3):

   o  Type = 0: String.

   Information type values 1 through 32767 MUST be assigned using the
   "Standards Action" policy, and values 32768 through 65535 using the
   "Specification Required" policy, defined in [RFC5226].

9.  Security Considerations

   This document defines a mechanism to obtain a full dump or provide
   continuous monitoring of a BGP speaker's local BGP table, including
   received BGP messages.  This capability could allow an outside party
   to obtain information not otherwise obtainable.

   Implementations of this protocol MUST require manual configuration of
   the monitored and monitoring devices.

   Users of this protocol MAY use some type of secure transmission
   mechanism, such as IPSec [RFC4303], to transmit this data.

10.  Acknowledgements

   Thanks to John ji Ioannidis, Mack McBride, Danny McPherson, Dimitri
   Papadimitriou, Erik Romijn, and the members of the GROW working group
   for their comments.

11.  References

11.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC4271]  Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
              Protocol 4 (BGP-4)", RFC 4271, January 2006.

   [RFC4724]  Sangli, S., Chen, E., Fernando, R., Scudder, J., and Y.
              Rekhter, "Graceful Restart Mechanism for BGP", RFC 4724,
              January 2007.

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   [RFC4893]  Vohra, Q. and E. Chen, "BGP Support for Four-octet AS
              Number Space", RFC 4893, May 2007.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              May 2008.

11.2.  Informative References

   [RFC4303]  Kent, S., "IP Encapsulating Security Payload (ESP)",
              RFC 4303, December 2005.

Appendix A.  Changes Between BMP Versions 1 and 2

   o  Added Peer Up Message
   o  Added L flag
   o  Editorial changes

Appendix B.  Changes Between BMP Versions 2 and 3

   o  Added a 16-bit length field to the fixed header.
   o  Clarified error handling.
   o  Added stat types 5 and 6 (number of updates invalidated due to
      ORIGINATOR_ID and AS_CONFED, respectively).
   o  For peer down messages, the relevant FSM event is to be sent in
      type 2 messages.
   o  Added local address and local and remote ports to the peer up
      message.
   o  Require End-of-RIB marker after initial dump.
   o  Added Initiation message with string content.
   o  Changed assignment policy for IANA registries.
   o  Editorial changes.

Authors' Addresses

   John Scudder
   Juniper Networks
   1194 N. Mathilda Ave
   Sunnyvale, CA  94089
   USA

   Email: jgs@juniper.net

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   Rex Fernando
   Cisco Systems
   170 W. Tasman Dr.
   San Jose, CA  95134
   USA

   Email: rex@cisco.com

   Stephen Stuart
   Google
   1600 Amphitheatre Parkway
   Mountain View, CA  94043
   USA

   Email: sstuart@google.com

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