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Versions: 00

IDR Working Group                                            D. Freedman
Internet-Draft                                                  Claranet
Intended status: Standards Track                               R. Raszuk
Expires: September 1, 2012                                  NTT MCL Inc.
                                                               R. Shakir
                                                                      BT
                                                       February 29, 2012


                        BGP OPERATIONAL Message
                 draft-ietf-idr-operational-message-00

Abstract

   The BGP Version 4 routing protocol (RFC4271) is now used in many
   ways, crossing boundaries of administrative and technical
   responsibility.

   The protocol lacks an operational messaging plane which could be
   utilised to diagnose, troubleshoot and inform upon various conditions
   across these boundaries, securely, during protocol operation, without
   disruption.

   This document proposes a new BGP message type, the OPERATIONAL
   message, which can be used to effect such a messaging plane for use
   both between and within Autonomous Systems.

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 September 1, 2012.

Copyright Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors.  All rights reserved.



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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Applications . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  BGP OPERATIONAL message  . . . . . . . . . . . . . . . . . . .  5
     3.1.  BGP OPERATIONAL message capability . . . . . . . . . . . .  5
     3.2.  BGP OPERATIONAL message encoding . . . . . . . . . . . . .  5
     3.3.  PRI Format . . . . . . . . . . . . . . . . . . . . . . . .  6
     3.4.  BGP OPERATIONAL message TLVs . . . . . . . . . . . . . . .  9
       3.4.1.  ADVISE TLVs  . . . . . . . . . . . . . . . . . . . . .  9
       3.4.2.  STATE TLVs . . . . . . . . . . . . . . . . . . . . . . 10
       3.4.3.  DUMP TLVs  . . . . . . . . . . . . . . . . . . . . . . 12
       3.4.4.  CONTROL TLVs . . . . . . . . . . . . . . . . . . . . . 13
   4.  Use of the ADVISE TLVs . . . . . . . . . . . . . . . . . . . . 16
   5.  Use of the STATE TLVs  . . . . . . . . . . . . . . . . . . . . 18
     5.1.  Utilising STATE TLVs for Cross-Domain Debugging
           Functionality  . . . . . . . . . . . . . . . . . . . . . . 18
     5.2.  Utilising STATE TLVs in the context of Error Handling  . . 18
   6.  Use of the DUMP TLVs . . . . . . . . . . . . . . . . . . . . . 20
   7.  Error Handling . . . . . . . . . . . . . . . . . . . . . . . . 22
   8.  Security considerations  . . . . . . . . . . . . . . . . . . . 23
   9.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 24
   10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 26
   11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 27
     11.1. Normative References . . . . . . . . . . . . . . . . . . . 27
     11.2. Informative References . . . . . . . . . . . . . . . . . . 27
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 29













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1.  Introduction

   In this document, a new BGP message type, the OPERATIONAL message is
   defined, creating a communication channel over which messages can be
   passed, using a series of contained TLV elements.

   The messages can be human readable, for the attention of device
   operators or machine readable, in order to provide simple self test
   routines, which can be exchanged between BGP speakers.

   A number of TLV elements will be assigned to provide for these
   message types, along with TLV elements to assist with description of
   the message data, such as describing precisely BGP prefixes and
   encapsulating BGP UPDATE messages to be sent back for inspection in
   order to troubleshoot session malfunctions.

   The use of OPERATIONAL messages will be negotiated by BGP Capability
   [RFC5492], since the messages are in-band with the BGP session, they
   can be assumed to either be authenticated as originating directly
   from the BGP neighbor.

   The goal of this document is to provide a simple, extensible
   framework within which new messaging and diagnostic requirements can
   live.



























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2.  Applications

   The authors would like to propose three main applications which BGP
   OPERATIONAL TLVs are designed to address.  New TLVs can be easily
   added to enhance further current applications or to propose new
   applications.

   The set of TLVs is organised in the following four functional groups
   comprising the three applications and some control messaging:

   o  ADVISE TLVs, designed to convey human readable information to be
      passed, cross boundary to operators, to inform them of past or
      upcoming error conditions, or provide other relevant, in-band
      operational information.  The "Advisory Demand Message" ADM
      (Section 3.4.1.1) is an example of this.

   o  STATE TLVs, designed to carry information about BGP state across
      BGP neighbors, including both per-neighbor and global counters.

   o  DUMP TLVs, designed to describe or encapsulate data to assist in
      realtime or post-mortem diagnostics, such as structured
      representations of affected prefixes / NLRI and encapsulated raw
      UPDATE messages for inspection.

   o  CONTROL TLVs, designed to facilitate control messaging such as
      replies to requests which can not be satisfied.

   Means concerning the reporting of information carried by these TLVs,
   either in reply or request processing are implementation specific but
   could include methods such as SYSLOG.





















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3.  BGP OPERATIONAL message

3.1.  BGP OPERATIONAL message capability

   A BGP speaker that is willing to exchange BGP OPERATIONAL Messages
   with a neighbor should advertise the new OPERATIONAL Message
   Capability to the neighbor using BGP Capabilities advertisement
   [RFC5492] .  A BGP speaker may send an OPERATIONAL message to its
   neighbor only if it has received the OPERATIONAL message capability
   from them.

   The Capability Code for this capability is specified in the IANA
   Considerations section of this document.

   The Capability Length field of this capability is 2 octets.



                      +------------------------------+
                      | Capability Code (1 octet)    |
                      +------------------------------+
                      | Capability Length (1 octet)  |
                      +------------------------------+



                 OPERATIONAL message BGP Capability Format

3.2.  BGP OPERATIONAL message encoding

   The BGP message as defined [RFC4271] consists of a fixed-size header
   followed by two octet length field and one octet of type value.  The
   RFC limits the maximum message size to 4096 octets.  As one of the
   applications of BGP OPERATIONAL message (through the MUD
   (Section 3.4.3.3) message) is to be able to carry an entire,
   potentially malformed BGP UPDATE, this specification mandates that
   when the neighbor has negotiated the BGP OPERATIONAL message
   capability, any further BGP message which may be subject to enclosure
   within a BGP OPERATIONAL message must be sent with the maximum size
   reduced to accommodate for the potential need of additional wrapping
   header size requirements.  This is applicable to both the current BGP
   maximum message size limit or for any future modifications.

   For the purpose of the OPERATIONAL message information encoding we
   will use one or more Type-Length-Value containers where each TLV will
   have the following format:





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     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 2
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |      Type (2 octets)          |       Length (2 octets)       |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                      Value (Variable)                         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                      OPERATIONAL message TLV Format

   TYPE: 2 octet value indicating the TLV type

   LENGTH: 2 octet value indicating the TLV length in octets

   VALUE: Variable length value field depending on the type of the TLVs
   carried.

   To work around continued BGP churn issues some types of TLVs will
   need to contain a sequence number to correlate a request with
   associated replies.  The sequence number will consist of 8 octets and
   will be of the form: (4 octet bgp_router_id) + (local 4 octet
   number).  When the local 4 octet number reaches 0xFFFF it should
   restart from 0x0000.  The sequence number is only used if the TLV
   requires sequencing else it is not included.

   The typical application scenario for use of the sequence number is
   for it to be included in a request TLV to be copied into associated
   reply messages in order to correlate requests with their associated
   replies.

3.3.  PRI Format

   Prefix Reachability Indicators (PRI) are used to represent prefix
   NLRI and BGP attributes in a request and only prefix NLRI in a
   response, in this draft.

   Each PRI is encoded as a 3-tuple of the form <Flags, Payload Type,
   Payload> whose fields are described below:












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     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 2
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |     Flags      |  Payload Type |      Payload (Variable)      |
     +---------------------------------------------------------------+
     |                     Payload (Variable)                        |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The use and the meaning of these fields are as follows:

   a) Flags:
      Four bits indicating NLRI Reachability:


                             0 1 2 3 4 5 6 7 8
                             +-+-+-+-+-+-+-+-+
                             |R|I|O|L| Resvd |
                             +-+-+-+-+-+-+-+-+

      aa) R Bit:
         The R (Reachable) bit, if set represents that the prefixes were
         deemed reachable in the NLRI, else represents that the prefixes
         were deemed unreachable.  This bit is meaningless in the
         context of all currently defined requests and can thus only be
         found in a response.  If found in a request an implementation
         MUST ignore its state.

      ab) I Bit:
         The I (Adj-RIB-In) bit, if set in a query, indicates that the
         requestor wishes for the response to be found in the Adj-RIB-In
         of the neighbor representing this session, if cleared indicates
         that the Adj-RIB-In of the neighbor representing this session
         is not searched.  If set in a response, indicates that the Adj-
         RIB-In of the neighbor representing this session contained this
         information, if cleared it did not.

      ac) O Bit:
         The O (Adj-RIB-Out) bit, if set in a query, indicates that the
         requestor wishes for the response to be found in the Adj-RIB-
         Out of the neighbor representing this session, if cleared
         indicates that the Adj-RIB-Out of the neighbor representing
         this session is not searched.  If set in a response, indicates
         that the Adj-RIB-Out of the neighbor representing this session
         contained this information, if cleared it did not.







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      ad) L Bit:
         The L (Loc-RIB) bit, if set in a query, indicates that the
         requestor wishes for the response to be found in the BGP Loc-
         RIB of the neighbor, if cleared indicates that the Loc-RIB of
         the neighbor is not searched.  If set in a response, indicates
         that the Loc-RIB of the neighbor contained this information, if
         cleared it did not.

      The rest of the field is reserved for future use.

   b) Payload Type:
      This one octet type specifies the type and geometry of the
      payload.

      ba) Type 0 - NLRI:
         The payload contains (perhaps multiple) NLRI, the format of
         each NLRI is as defined in the base specification of such NLRI
         appropriate for the AFI/SAFI.

      bb) Type 1 - Next Hop:
         The payload contains a Next Hop address, appropriate for the
         AFI/SAFI.  When used in an SSQ (Section 3.4.2.7) message the
         response is expected to contain prefixes from the selected RIBs
         which contain this next-hop in their next-hop attribute.

      bc) Type 2 - AS Number:
         The payload contains a 16 or 32 bit AS number (as defined in
         [RFC4893]), when used in an SSQ message the response is
         expected to contain prefixes from the selected RIBs which
         contain this AS number in their AS_PATH or AS4_PATH (as
         appropriate) attributes.

      bc) Type 3 - Standard Community:
         The payload contains a standard community (as defined in
         [RFC1997]), when used in an SSQ message the response is
         expected to contain prefixes from the selected RIBs which
         contain this standard community in their communities attribute.

      bd) Type 4 - Extended Community:
         The payload contains an extended community (as defined in
         [RFC4360]), when used in an SSQ message the response is
         expected to contain prefixes from the selected RIBs which
         contain this standard community in their extended communities
         attribute.







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      be) Types 5-65535 - Reserved:
         Types 5-65535 are reserved for future use.

   c) Payload:
      Contains the actual payload, as defined by the payload type, the
      payload is of variable length, to be calculated from the remaining
      TLV length.

   PRI are used for both request and response modes, a response MUST
   only contain an NLRI (type 0) payload but a request MAY contain
   payloads specifying a type to search for, an implementation MUST
   validate all PRI it receives in a request against the type of request
   which was made.

   An implementation MUST NOT send a PRI in response with no NLRI (type
   0) payload, this is considered to be invalid.  If the implementation
   wishes to signal that a request did not yield a any valid results an
   implementation MAY respond with an NS TLV (Section 3.4.4.2), using
   the "Not Found" subcode, for example.

3.4.  BGP OPERATIONAL message TLVs

3.4.1.  ADVISE TLVs

   ADVISE TLVs convey human readable information to be passed, cross
   boundary to operators, to inform them of past or upcoming error
   conditions, or provide other relevant, in-band operational
   information.

3.4.1.1.  Advisory Demand Message (ADM)

   TYPE: 1 - ADM

   LENGTH: 3 Octets (AFI+SAFI) + Variable value (up to 2K octets)

   USE: To carry a message, on demand, comprised of a string of UTF-8
   characters (up to 2K octets in size), with no null termination.  Upon
   reception, the string SHOULD be reported to the host's administrator.

   Implementations SHOULD provide their users the ability to transmit a
   free form text message generated by user input.

3.4.1.2.  Advisory Static Message (ASM)

   TYPE: 2 - ASM

   LENGTH: 3 Octets (AFI+SAFI) + Variable value (up to 2K octets)




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   USE: To carry a message, on demand, comprised of a string of UTF-8
   characters, with no null termination.  Upon reception, the string
   SHOULD be stored in the BGP neighbor statistics field within the
   router.  The string SHOULD be accessible to the operator by executing
   CLI commands or any other method (local or remote) to obtain BGP
   neighbor statistics (e.g.  NETCONF, SNMP).

   The expectation is that the last ASM received from a BGP neighbor
   will be the message visible to the operator (the most current ASM).

   Implementations SHOULD provide their users the ability to transmit a
   free form text message generated by user input.

3.4.2.  STATE TLVs

   STATE TLVs reflect, on demand, the internal state of a BGP neighbor
   as seen from the other neighbor's perspective.

3.4.2.1.  Reachable Prefix Count Request (RPCQ)

   TYPE: 3 - RPCQ

   LENGTH: 3 Octets (AFI+SAFI) + Sequence Number

   USE: Sent to the neighbor to request that an RPCP (Section 3.4.2.2)
   message is generated in response.

3.4.2.2.  Reachable Prefix Count Reply (RPCP)

   TYPE: 4 - RPCP

   LENGTH: 3 Octets (AFI+SAFI) + Sequence Number + 4 Octet RX Prefix
   Counter (RXC) + 4 Octet TX Prefix Counter (TXC)

   USE: Sent in reply to an RPCQ (Section 3.4.2.1) message from a
   neighbor, RXC is populated with the number of reachable prefixes
   accepted from the peer and TXC with the number of prefixes to be
   transmitted to the peer for the AFI/SAFI.

3.4.2.3.  Adj-Rib-Out Prefix Count Request (APCQ)

   TYPE: 5 - APCQ

   LENGTH: 3 Octets(AFI+SAFI) + Sequence Number

   USE: Sent to the neighbor to request that an APCP (Section 3.4.2.4)
   message is generated in response.




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   APCQ can be used as a simple mechanism when an implementation does
   not permit or support the use of RPCQ.

3.4.2.4.  Adj-Rib-Out Prefix Count Reply (APCP)

   TYPE: 6 - APCP

   LENGTH: 3 Octets(AFI+SAFI) + Sequence Number + 4 Octet TX Prefix
   Counter (TXC)

   USE: Sent in reply to an APCQ (Section 3.4.2.3) message from a
   neighbor, TXC is populated with the number of prefixes held in the
   Adj-Rib-Out for the neighbor for the AFI/SAFI.

3.4.2.5.  BGP Loc-Rib Prefix Count Request (LPCQ)

   TYPE: 7 - LPCQ

   LENGTH: 3 Octets(AFI+SAFI) + Sequence Number

   USE: Sent to the peer to request that an LPCP (Section 3.4.2.6)
   message is generated in response.

3.4.2.6.  BGP Loc-Rib Prefix Count Reply (LPCP)

   TYPE: 8 - LPCP

   LENGTH: 3 Octets(AFI+SAFI) + Sequence Number + 4 Octet Loc-Rib
   Counter (LC)

   USE: Sent in reply to an LPCQ (Section 3.4.2.5) message from a
   neighbor, LC is populated with the number of prefixes held in the
   entire Loc-Rib for the AFI/SAFI.

3.4.2.7.  Simple State Request (SSQ)

   TYPE: 9 - SSQ

   LENGTH: 3 Octets(AFI+SAFI) + Sequence Number + Single request PRI
   (Variable)

   USE: Using a PRI as a request form (See Section 3.3), an
   implementation can be asked to return information about prefixes
   found in various RIBs.

   A single, simple PRI is used in the request, containing a single NLRI
   or attribute as the PRI payload.  RIB response filtering may take
   place through the setting of the I, O and L bits in the PRI Flags



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   field.

   An implementation MAY respond to an SSQ TLV in with an SSP (See
   Section 3.4.3.4) TLV (containing the appropriate data).  An
   implementation MAY also respond to an SSQ with an NS TLV (with the
   appropriate subcode set) indicating why there will not be an SSP TLV
   in response.  An implementation MAY also not respond at all (See
   Section 8).

3.4.3.  DUMP TLVs

   DUMP TLVs provide data in both structured and unstructured formats in
   response to events, for use in debugging scenarios.

3.4.3.1.  Dropped Update Prefixes (DUP)

   TYPE: 10 - DUP

   LENGTH: 3 Octets(AFI+SAFI) + Variable number of dropped UPDATE Prefix
   Reachability Indicators (PRI) (See Section 3.3)

   USE: To report to a neighbor a structured set of prefix reachability
   indicators retrievable from the last dropped UPDATE message, sent in
   response to an UPDATE message which was well formed but not accepted
   by the neighbor by policy.

   For example, an UPDATE which was dropped and the rescued NLRI
   concerned a number of both reachable and unreachable prefixes, the
   DUP would encapsulate two PRI, one with the R-Bit (reachable) set,
   housing the rescued reachable NLRI and the other with the R-Bit
   cleared (unreachable), housing the rescued unreachable NLRI as
   payload.

3.4.3.2.  Malformed Update Prefixes (MUP)

   TYPE: 11 - MUP

   LENGTH: 3 Octets(AFI+SAFI) + Variable number of dropped update Prefix
   Reachability Indicators (PRI) (See Section 3.3) due to UPDATE
   Malformation.

   USE: To report to a neighbor a structured set of prefix reachability
   indicators retrievable from the last UPDATE message dropped through
   malformation, sent in response to an UPDATE message which was not
   well formed and not accepted by the neighbor, where a NOTIFICATION
   message was not sent.  A MUP TLV may accompany a MUD
   (Section 3.4.3.3) TLV.




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   See the example from Section 3.4.3.1.

3.4.3.3.  Malformed Update Dump (MUD)

   TYPE: 12 - MUD

   LENGTH: 3 Octets(AFI+SAFI) + Variable length representing retrievable
   malformed update octet stream.

   USE: To report to a peer a copy of the last UPDATE message dropped
   through malformation, sent in response to an UPDATE message which was
   not well formed and not accepted by the neighbor, where a
   NOTIFICATION message was not sent.  A MUD TLV may accompany a MUP
   (Section 3.4.3.2) TLV.

3.4.3.4.  Simple State Response (SSP)

   TYPE: 13 - SSP

   LENGTH: 3 Octets(AFI+SAFI) + Sequence Number + Single Response PRI
   (Variable)

   USE: Using a PRI as a response form (See Section 3.3), an
   implementation uses the SSP TLV to return a response to an SSQ (See
   Section 3.4.2.7) TLV which should contain information about prefixes
   found in various RIBs.  These RIBs should be walked to extract the
   information according to local policy.

   A single, simple PRI is used in the response, containing multiple
   NLRI.  The I, O and L bits in the PRI Flags field should be set
   indicating which RIBs the prefixes were found in.

   An implementation MAY respond to an SSQ TLV in with an SSP TLV
   (containing the appropriate data).  An implementation MAY also
   respond to an SSQ with an NS TLV (with the appropriate subcode set)
   indicating why there will not be an SSP TLV in response.  An
   implementation MAY also not respond at all (See Section 8).

   If no data is found to satisfy a query which is permitted to be
   answered, an implementation MAY respond with an NS TLV with the
   subcode "Not Found" to indicate that no data was found in response to
   the query.  An implementation MUST NOT send a PRI in response with no
   NLRI payload, this is considered to be invalid.

3.4.4.  CONTROL TLVs

   CONTROL TLVs satisfy control mechanism messaging between neighbors,
   they are used for such functions as to refuse messages and



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   dynamically signal OPERATIONAL capabilities to neighbors during
   operation.

3.4.4.1.  Max Permitted (MP)

   TYPE: 65534 - MP

   LENGTH: 3 Octets(AFI+SAFI) + 2 Octet Value

   USE: The Max Permitted TLV is used to signal to the neighbor the
   maximum number of OPERATIONAL messages that will be accepted in a
   second of time (see Section 8, Security Considerations), an
   implementation MUST, on receipt of an MP TLV, ensure that it does not
   exceed the rate specified in the MP TLV for sending OPERATIONAL
   messages to the neighbor, for the duration of the session.

   An implementation MAY send subsequent MP TLVs during the session's
   lifetime, updating the maximum acceptable rate

   MP TLVs MAY be rate limited by the receiver as part of OPERATIONAL
   rate limiting (see Section 8, Security Considerations).

3.4.4.2.  Not Satisfied (NS)

   TYPE: 65535 - NS

   LENGTH: 3 Octets(AFI+SAFI) + Sequence Number + 2 Octet Error Subcode

   USE: To respond to a query to indicate that the implementation can or
   will not answer this query.  The following subcodes are defined:

   0x01 - Request TLV Malformed:  Used to signal to the neighbor that
      the request was malformed and will not be processed.  A neighbor
      on receiving this message MAY re-transmit the request but MUST
      increment the sequence number.  Implementations SHOULD ensure that
      the same request is not retransmitted excessively when repeatedly
      receiving this Error Subcode in response.

   0x02 - TLV Unsupported for this neighbor:  Used to signal to the
      neighbor that the request was unsupported and will not be
      processed.  A neighbor on receiving this message MUST NOT
      retransmit the request for the duration of the session.

   0x03 - Max query frequency exceeded:  Used to signal to the neighbor
      that the request has exceeded the rate at which the neighbor finds
      acceptable for the implementation to transmit requests at, see
      Section 3.4.4.1 (MP TLV) and Section 8 and (Security
      Considerations) for more information.



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   0x04 - Administratively prohibited:  Used to signal to the neighbor
      that the request was administratively prohibited and will not be
      processed.  A neighbor on receiving this message MUST NOT
      retransmit the request for the duration of the session.

   0x05 - Busy:  Used to signal to the neighbor that the request will
      not be replied to, due to lack of resources estimated to satisfy
      the request.  It is suggested that, on receipt of this error
      subcode a message is logged to inform the operator of this failure
      as opposed to automatically attempting to re-try the previous
      query.

   0x06 - Not Found:  Used to signal to the neighbor that the request
      would have been replied to but does not contain any data (i.e the
      data was not found).  An implementation MUST NOT send a PRI
      response with no NLRI payload, this is considered to be invalid.

   NS TLVs MAY be rate limited by the receiver as part of OPERATIONAL
   rate limiting (see Section 8, Security Considerations).
































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4.  Use of the ADVISE TLVs

   The BGP routing protocol is used with external as well as internal
   neighbors to propagate route advertisements.  In the case of external
   BGP sessions, there is typically a demarcation of administrative
   responsibility between the two entities.  While initial configuration
   and troubleshooting of these sessions is handled via offline means
   such as email or telephone calls, there is gap when it comes to
   advising a BGP neighbor of a behaviour that is occurring or will
   occur momentarily.  There is a need for operators to transmit a
   message to a BGP neighbor to notify them of a variety of types of
   messages.  These messages typically would include those related to a
   planned or unplanned maintenance action.  These ADVISE messages could
   then be interpreted by the remote party and either parsed via logging
   mechanisms or viewed by a human on the remote end via the CLI.  This
   capability will improve operator NOC-to-NOC communication by
   providing a communications medium on an established and trusted BGP
   session between two autonomous systems.

   The reason that this method is preferred for NOC-to-NOC
   communications is that other offline methods do fail for a variety of
   reasons.  Emails to NOC aliases ahead of a planned maintenance may
   have ignored the mail or may have not of recorded it properly within
   an internal tracking system.  Even if the message was recorded
   properly, the staff that are on-duty at the time of the maintenance
   event typically are not the same staff who received the maintenance
   notice several days prior.  In addition, the staff on duty at the
   time of the event may not even be able to find the recorded event in
   their internal tracking systems.  The end result is that during a
   planned event, some subset of eBGP peers will respond to a session/
   peer down event with additional communications to the operator who is
   initiating the maintenance action.  This can be via telephone or via
   email, but either way, it may result in a sizeable amount of replies
   inquiring as to why the session is down.

   The result of this is that the NOC responsible for initiating the
   maintenance can be inundated with calls/emails from a variety of
   parties inquiring as to the status of the BGP session.  The NOC
   initiating the maintenance may have to further inquire with
   engineering staff (if they are not already aware) to find out the
   extent of the maintenance and communicate this back to all of the
   NOCs calling for additional information.  The above scenario outlines
   what is typical in a planned maintenance event.  In an unplanned
   maintenance event (the need for an immediate router upgrade/reload),
   the number of calls and emails will dramatically increase as more
   parties are unaware of the event.

   With the ADVISE TLV set, an operator can transmit an OPERATIONAL



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   message just prior to initiating the maintenance specifying what
   event will happen, what ticket number this event is associated with
   and the expected duration of the event.  This message would be
   received by BGP peers and stored in their logs as well as any
   monitoring system if they have this capability.  Now, all of the BGP
   peers have immediate access to the information about this session,
   why it went down, what ticket number this is being tracked under and
   how long they should wait before assuming there is an actual problem.
   Even smaller networks without the network management capabilities to
   correlate BGP events and OPERATIONAL messages would typically have an
   operator login to a router and examine the logs via the CLI.

   This draft specifies two types of ADVISE TLV, a DEMAND message (ADM)
   and a STATIC message (ASM), it is anticipated that the DEMAND message
   will be used to send a message, on demand to the BGP neighbor, to
   inform them of realtime events.  The STATIC message can be used to
   provide continual, "Sticky" information to the neighbor, such as a
   contact telephone number or e-mail address should there be a
   requirement to have continual access to this information.
































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5.  Use of the STATE TLVs

   At the current time, the BGP-4 protocol, provides no mechanism by
   which the state of a remote system can be examined.  Increasingly, as
   BGP-4 is utilised for additional applications, there is utility in
   providing in-band mechanisms for simple integrity checks, and
   diagnostic information to be exchanged between systems.  As such,
   there are two sets of applications envisaged to be implemented
   utilising the STATE TLVs of the OPERATIONAL message.

5.1.  Utilising STATE TLVs for Cross-Domain Debugging Functionality

   In numerous cases, autonomous system boundaries represent a
   demarcation point between operational teams - in these cases,
   debugging the information received over a BGP session between the two
   systems is likely to result in human-to-human contact.  In simple
   cases, this provides a particularly inefficient means by which
   specific queries regarding the routing information received via a
   BGP-4 session can be made.  Whilst complex debugging is likely to
   continue to involve operational personnel, in a number of cases, it
   is advantageous for an operator to allow the remote administrative
   team to validate specific characteristics of the router's RIB.  Such
   a means of debugging greatly enhances the speed of localising
   particular failures, and hence provides a potential reduction in the
   time to recovery of services dependent on the routing information
   transmitted via the BGP session.  The STATE TLVs described in this
   document are intended to provide a mechanism by which requests for,
   and responses containing such debugging information can be
   implemented.

   An example of the use of such a mechanism is on BGP-4 sessions making
   up a network-network interconnection carrying Layer 3 MPLS VPN
   [RFC4364] services - in these cases, such NNIs may be between
   particular administrative teams of the same network provider.  The
   OPERATIONAL SSQ is intended to provide a simple query language that
   can be utilised to receive the subset of routing information that
   matches a particular query within the remote system's RIB.  It is
   envisaged that such behaviour provides a simple means by which an
   operator can validate whether particular routing information is
   present, and as expected, on the remote system.  Identification of
   inconsistencies quickly allows the device responsible for missing or
   incorrect information to be identified without direct interaction
   between humans.

5.2.  Utilising STATE TLVs in the context of Error Handling

   The enhancements to the BGP-4 protocol intended to provide more
   targeted error handling described in [I-D.ietf-idr-error-handling]



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   provide a number of cases whereby NLRI that are contained in
   particular UPDATEs may not be accepted by the remote BGP speaker.  In
   this case, there is currently no mechanism by which an operator can
   identify whether the routing information received by the local
   speaker matches that which the remote speaker purports to have
   advertised.  The Adj-Rib-Out Prefix Count Request (APCQ) and
   Reachable Prefix Count Request (RPCQ) are intended to provide means
   by which simple validation can be performed between two BGP speakers.
   It is envisaged that a BGP implementation can simply validate whether
   the remote system's RIB is consistent utilising such a mechanism, and
   hence trigger follow-up actions based on this.  The extent of such
   follow-up actions is not intended to be defined by this document,
   however, it is envisaged that there is utility in such a state being
   flagged to an operational team to allow investigation of any
   inconsistency to be examined.  Since many BGP-4 UPDATE message errors
   may be transient, validating the prefix counts in the local RIB
   against those received in response to the STATE TLV prefix count
   query messages described herein allows an operator to determine
   whether any inconsistency is persisting at the time of query, and
   hence whether any action is required.

   In addition to allowing a manually-triggered validation of the RIB
   prefix counts, such a mechanism provides a simple means by which
   automated consistency checking can be enhanced on a BGP session.  A
   device initiating a periodic check based on the RPCQ or APCQ TLVs can
   validate basic information regarding the number of entries in a
   particular RIB of a remote neighbor.  Such consistency checks may
   trigger further (more detailed) sets of consistency validation
   mechanisms, or be flagged to a local operator.  In this case, the
   potential forwarding black-holes that can be caused by inconsistency
   in the RIB of two systems can be quickly identified, and examined by
   an operator, or recovered from via an automated means such as a
   ROUTE-REFRESH message.  As such, the use of the OPERATIONAL TLV in
   this case allows the resources on the BGP speakers involved to be
   minimised by allowing the speakers to perform a lightweight check
   prior to triggering any further action.















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6.  Use of the DUMP TLVs

   Where a notable condition is experienced by a BGP-4 speaker,
   currently a limited set of responses are available to the speaker to
   make human network administrators aware of the condition.  Within a
   local administrative boundary, logging functionality such as SNMP and
   SYSLOG can be used to record the occurrence of the event, as such,
   this provides visibility in an effective manner to the local
   administrator of the device.  Whilst this provides a mechanism to
   make the router operator aware of erroneous states, or messages,
   where the condition is a direct result of an input from a remote
   system, or the information is of note to the remote BGP speaker,
   there is no means to communicate the detection of an erroneous
   condition to the remote device.  As described in
   [I-D.ietf-grow-ops-reqs-for-bgp-error-handling] such conditions are
   likely to occur within the context of the handling of erroneous
   UPDATE messages.

   The OPERATIONAL message intends to provide a number of message types
   to a BGP speaker that can be used to communicate information to a
   remote system.  Whilst clearly free-text mechanisms such as the ADM
   provide a means by which arbitrary information can be transmitted,
   the use of a structured message type indicating particular message
   data can be transmitted back to the remote speaker provides means by
   which this information can be processed and reported directly.  As
   such, the knowledge that particular OPERATIONAL messages relate to
   particular erroneous conditions that may be affecting network
   operation allows a system to determine any specific response actions,
   or prioritise any reporting to network management systems.

   Where an UPDATE message's NLRI attribute can be wholly parsed, the
   pertinent information as to the prefixes that have been identified to
   be in the message is available to the receiving BGP speaker.
   Clearly, this information is of relevance to the administrators of
   the remote device, and is likely to provide some information
   regarding the contents of the message which is considered erroneous.
   The Malformed UPDATE Prefixes (MUP) TLV defined herein is intended to
   allow the receiving speaker to transmit the minimum required
   information regarding an UPDATE identified as malformed to the remote
   speaker without the overhead of additional path attributes (which may
   not be available to the receiving speaker).  It is envisaged that the
   Dropped Update Prefixes (DUP) TLV provides analogous behaviour in the
   case where the UPDATE message is dropped due to local administrative
   policy, or implementation characteristics.

   In some cases in order to determine the exact condition resulting in
   an error, there is a requirement for a network operator (or equipment
   implementor) to have an exact copy of the protocol message



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   transmitted to a remote system.  The operational requirements
   presented in [I-D.ietf-grow-ops-reqs-for-bgp-error-handling] describe
   the operational advantage of logging a copy of such a message
   locally, however, where the message is erroneous due to a bug in the
   formation or transmission of the message by the sender, and the error
   is identified on the receiving speaker, this information is not
   available to the operator responsible for the erroneous network
   element.  The Malformed UPDATE Dump (MUD) TLV is intended to be
   utilised to transmit an encapsulated copy of such a message back to
   the remote BGP speaker, and hence allow the operator to determine the
   exact formation of the invalid message.








































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7.  Error Handling

   An implementation MUST NOT send an OPERATIONAL message to a neighbor
   in response to an erroneous or malformed OPERATIONAL message.  Any
   erroneous or malformed OPERATIONAL message received SHOULD be logged
   for the attention of the operator and then MAY be discarded.













































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8.  Security considerations

   No new security issues are introduced to the BGP protocol by this
   specification.

   Where a request type is not supported or allowed by an implementation
   for some reason, the implementation MAY send an NS (Section 3.4.4.2)
   TLV in response, the Error subcode of this TLV SHOULD be set
   according to the reason that this request will not be responded to.

   Implementations MUST rate-limit the rate at which they transmit and
   receive OPERATIONAL messages.  Specifically, an implementation MUST
   NOT allow the handling of OPERATIONAL messages to negatively impact
   any other functions on a router such as regular BGP message handling
   or other routing protocols.

   Although an NS error subcode is provided to indicate that a request
   was rate-limited, an implementation need not reply to a request at
   all, this is the suggested course of action when rate-limiting the
   sending of responses to a neighbor.

   An implementation MAY send an MP (Section 3.4.4.1) TLV to indicate
   the maximum rate at which it will accept OPERATIONAL messages from a
   neighbor, upon receipt of this TLV the sender MUST ensure it does not
   transmit above this rate for the duration of the session.

   An implementation, considering a request to be too computationally
   expensive, MAY reply with the "Busy" NS error subcode to indicate
   such, though the implementation need not reply to the request.

   Implementations MUST provide a mechanism for preventing access to
   information requested by SSR (Section 3.4.2.7) messages for the
   operator.  Implementations SHOULD ensure that responses concerning
   the Loc-RIB (PRI with L-Bit set or responses which would set the
   L-Bit) are filtered in the default configuration.
















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9.  IANA Considerations

   IANA is requested to allocate a type code for the OPERATIONAL message
   from the BGP Message Types registry, as well as requesting a type
   code for the new OPERATIONAL Message Capability negotiation from BGP
   Capability Codes registry.

   This document requests IANA to define and maintain a new registry
   named: "OPERATIONAL Message Type Values".  The allocation policy is
   on a first come first served basis.

   This document makes the following assignments for the OPERATIONAL
   Message Type Values:

   ADVISE:

      *  Type 1 - Advisory Demand Message (ADM)

      *  Type 2 - Advisory Static Message (ASM)

   STATE:

      *  Type 3 - Reachable Prefix Count Request (RPCQ)

      *  Type 4 - Reachable Prefix Count Response (RPCP)

      *  Type 5 - Adj-RIB-Out Prefix Count Request (APCQ)

      *  Type 6 - Adj-RIB-Out Prefix Count Response (APCP)

      *  Type 7 - Loc-Rib Prefix Count Request (LPCQ)

      *  Type 8 - Loc-Rib Prefix Count Response (LPCP)

      *  Type 9 - Simple State Request (SSQ)

   DUMP:

      *  Type 10 - Dropped Update Prefixes (DUP)

      *  Type 11 - Malformed Update Prefixes (MUP)

      *  Type 12 - Malformed Update Dump (MUD)

      *  Type 13 - Simple State Response (SSP)






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   CONTROL:

      *  Type 65534 - Max Permitted (MP)

      *  Type 65535 - Not Satisfied (NS)














































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10.  Acknowledgements

   This memo is based on existing works [I-D.ietf-idr-advisory] and
   [I-D.raszuk-bgp-diagnostic-message] which describe a number of
   operational message types documented here.  The authors would like to
   thank Enke Chen, Bruno Decraene, Alton Lo, Tom Scholl, John Scudder
   and Richard Steenbergen for their valuable input.












































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11.  References

11.1.  Normative References

   [RFC1997]  Chandrasekeran, R., Traina, P., and T. Li, "BGP
              Communities Attribute", RFC 1997, August 1996.

   [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.

   [RFC4360]  Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended
              Communities Attribute", RFC 4360, February 2006.

   [RFC4760]  Bates, T., Chandra, R., Katz, D., and Y. Rekhter,
              "Multiprotocol Extensions for BGP-4", RFC 4760,
              January 2007.

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

   [RFC5492]  Scudder, J. and R. Chandra, "Capabilities Advertisement
              with BGP-4", RFC 5492, February 2009.

11.2.  Informative References

   [I-D.ietf-grow-ops-reqs-for-bgp-error-handling]
              Shakir, R., "Operational Requirements for Enhanced Error
              Handling Behaviour in BGP-4",
              draft-ietf-grow-ops-reqs-for-bgp-error-handling-02 (work
              in progress), October 2011.

   [I-D.ietf-idr-advisory]
              Scholl, T., Scudder, J., Steenbergen, R., and D. Freedman,
              "BGP Advisory Message", draft-ietf-idr-advisory-00 (work
              in progress), October 2009.

   [I-D.ietf-idr-error-handling]
              Scudder, J., Chen, E., Mohapatra, P., and K. Patel,
              "Revised Error Handling for BGP UPDATE Messages",
              draft-ietf-idr-error-handling-01 (work in progress),
              December 2011.

   [I-D.jasinska-ix-bgp-route-server]
              Jasinska, E., Hilliard, N., Raszuk, R., and N. Bakker,
              "Internet Exchange Route Server",



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              draft-jasinska-ix-bgp-route-server-03 (work in progress),
              October 2011.

   [I-D.nalawade-bgp-inform]
              Nalawade, G., Scudder, J., and D. Ward, "BGPv4 INFORM
              message", draft-nalawade-bgp-inform-02 (work in progress),
              August 2002.

   [I-D.nalawade-bgp-soft-notify]
              Nalawade, G., "BGPv4 Soft-Notification Message",
              draft-nalawade-bgp-soft-notify-01 (work in progress),
              July 2005.

   [I-D.raszuk-bgp-diagnostic-message]
              Raszuk, R., Chen, E., and B. Decraene, "BGP Diagnostic
              Message", draft-raszuk-bgp-diagnostic-message-02 (work in
              progress), March 2011.

   [I-D.retana-bgp-security-state-diagnostic]
              Retana, A. and R. Raszuk, "BGP Security State Diagnostic
              Message", draft-retana-bgp-security-state-diagnostic-00
              (work in progress), March 2011.

   [I-D.shakir-idr-ops-reqs-for-bgp-error-handling]
              Shakir, R., "Operational Requirements for Enhanced Error
              Handling Behaviour in BGP-4",
              draft-shakir-idr-ops-reqs-for-bgp-error-handling-01 (work
              in progress), February 2011.

   [RFC4364]  Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
              Networks (VPNs)", RFC 4364, February 2006.




















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Authors' Addresses

   David Freedman
   Claranet
   21 Southampton Row, Holborn
   London  WC1B 5HA
   UK

   Email: david.freedman@uk.clara.net


   Robert Raszuk
   NTT MCL Inc.
   101 S Ellsworth Avenue Suite 350
   San Mateo, CA  94401
   US

   Email: robert@raszuk.net


   Rob Shakir
   BT
   pp C3L
   BT Centre
   81, Newgate Street
   London  EC1A 7AJ
   UK

   Email: rob.shakir@bt.com
   URI:   http://www.bt.com/





















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