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IDR                                                          J. Snijders
Internet-Draft                                                       NTT
Obsoletes: 8203 (if approved)                                   J. Heitz
Updates: 4486 (if approved)                                        Cisco
Intended status: Standards Track                              J. Scudder
Expires: April 18, 2020                                          Juniper
                                                               A. Azimov
                                                        October 16, 2019

           Extended BGP Administrative Shutdown Communication


   This document enhances the BGP Cease NOTIFICATION message
   "Administrative Shutdown" and "Administrative Reset" subcodes for
   operators to transmit a short freeform message to describe why a BGP
   session was shutdown or reset.  This document updates RFC 4486 and
   obsoletes RFC 8203 by defining an Extended BGP Administrative
   Shutdown Communication to improve communication using multibyte
   character sets.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

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 https://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 April 18, 2020.

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Copyright Notice

   Copyright (c) 2019 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
   (https://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  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Shutdown Communication  . . . . . . . . . . . . . . . . . . .   2
   3.  Operational Considerations  . . . . . . . . . . . . . . . . .   3
   4.  Error Handling  . . . . . . . . . . . . . . . . . . . . . . .   4
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   7.  Implementation status - RFC EDITOR: REMOVE BEFORE PUBLICATION   5
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   6
   Appendix A.  Acknowledgements . . . . . . . . . . . . . . . . . .   6
   Appendix B.  Changes to RFC 8203  . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   It can be troublesome for an operator to correlate a BGP-4 [RFC4271]
   session teardown in the network with a notice that was transmitted
   via offline methods such email or telephone calls.  This document
   updates [RFC4486] by specifying a mechanism to transmit a short
   freeform UTF-8 [RFC3629] message as part of a Cease NOTIFICATION
   message [RFC4271] to inform the peer why the BGP session is being
   shutdown or reset.  This document obsoletes [RFC8203]; the specific
   differences and rationale are discussed in detail in Appendix B.

2.  Shutdown Communication

   If a BGP speaker decides to terminate its session with a BGP
   neighbor, and it sends a NOTIFICATION message with the Error Code
   "Cease" and Error Subcode "Administrative Shutdown" or

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   "Administrative Reset" [RFC4486], it MAY include a UTF-8 encoded
   string.  The contents of the string are at the operator's discretion.

   The Cease NOTIFICATION message with a Shutdown Communication is
   encoded as below:

    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
   | Error code 6  |    Subcode    |    Length     |     ...       \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+               /
   \                                                               \
   /                 ... Shutdown Communication ...                /
   \                                                               \

                                 Figure 1

   Subcode:  the Error Subcode value MUST be one of the following
      values: 2 ("Administrative Shutdown") or 4 ("Administrative

   Length:  this 8-bit field represents the length of the Shutdown
      Communication field in octets.  When the length value is zero, no
      Shutdown Communication field follows.

   Shutdown Communication:  to support international characters, the
      Shutdown Communication field MUST be encoded using UTF-8.  A
      receiving BGP speaker MUST NOT interpret invalid UTF-8 sequences.
      Note that when the Shutdown Communication contains multibyte
      characters, the number of characters will be less than the length
      value.  This field is not NULL terminated.

   Mechanisms concerning the reporting of information contained in the
   Shutdown Communication are implementation specific but SHOULD include
   methods such as Syslog [RFC5424].

3.  Operational Considerations

   Operators are encouraged to use the Shutdown Communication to inform
   their peers of the reason for the shutdown of the BGP session and
   include out-of-band reference materials.  An example of a useful
   Shutdown Communication would be:

   "[TICKET-1-1438367390] software upgrade; back in 2 hours"

   "[TICKET-1-1438367390]" is a ticket reference with significance to
   both the sender and receiver, followed by a brief human-readable

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   message regarding the reason for the BGP session shutdown followed by
   an indication about the length of the maintenance.  The receiver can
   now use the string 'TICKET-1-1438367390' to search in their email
   archive to find more details.

   If a Shutdown Communication longer than 128 octets is sent to a BGP
   speaker that implements [RFC8203], then that speaker will treat it as
   an error, the consequence of which is a log message.  For this
   reason, operators would be wise to keep shutdown communications to
   less than 128 octets when feasible.

   There is no guarantee that the receiver supports either this
   specification or [RFC8203], so any shutdown communication might not
   be logged in an easily-readable form at all.  Therefore, operators
   would also be wise not to rely on shutdown communications as their
   sole form of communication with their peer for important events.

4.  Error Handling

   If a Shutdown Communication with an invalid UTF-8 sequence is
   received, a message indicating this event SHOULD be logged for the
   attention of the operator.  An erroneous or malformed Shutdown
   Communication itself MAY be logged in a hexdump format.

5.  IANA Considerations

   Per this document, IANA is requested to reference this document at
   subcode "Administrative Shutdown", and at subcode "Administrative
   Reset" in the "Cease NOTIFICATION message subcodes" registry under
   the "Border Gateway Protocol (BGP) Parameters" group in addition to
   [RFC4486] and [RFC8203].

6.  Security Considerations

   This document uses UTF-8 encoding for the Shutdown Communication.
   There are a number of security issues with Unicode.  Implementers and
   operators are advised to review Unicode Technical Report #36 [UTR36]
   to learn about these issues.  UTF-8 "Shortest Form" encoding is
   REQUIRED to guard against the technical issues outlined in [UTR36].

   As BGP Shutdown Communications are likely to appear in syslog output,
   there is a risk that carefully constructed Shutdown Communication
   might be formatted by receiving systems in a way to make them appear
   as additional syslog messages.  The 255 octet length limit on the BGP
   Shutdown Communication may help limit the ability to mount such an

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   Users of this mechanism should be aware that unless a transport that
   provides integrity is used for the BGP session in question, a
   Shutdown Communication message could be forged.  Unless a transport
   that provides confidentiality is used, a Shutdown Communication
   message could be snooped by an attacker.  These issues are common to
   any BGP message but may be of greater interest in the context of this
   proposal since the information carried in the message is generally
   expected to be used for human-to-human communication.  Refer to the
   related considerations in [RFC4271] and [RFC4272].

   Users of this mechanism should consider applying data minimization
   practices as outlined in Section 6.1 of [RFC6973] because a received
   Shutdown Communication may be used at the receiver's discretion.


   This section records the status of known implementations of the
   protocol defined by this specification at the time of posting of this
   Internet-Draft, and is based on a proposal described in RFC7942.  The
   description of implementations in this section is intended to assist
   the IETF in its decision processes in progressing drafts to RFCs.
   Please note that the listing of any individual implementation here
   does not imply endorsement by the IETF.  Furthermore, no effort has
   been spent to verify the information presented here that was supplied
   by IETF contributors.  This is not intended as, and must not be
   construed to be, a catalog of available implementations or their
   features.  Readers are advised to note that other implementations may

   As of today these vendors have produced an implementation of the
   Shutdown Communication:

   o  Juniper Junos
   o  OpenBSD OpenBGPD
   o  ...

8.  References

8.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

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   [RFC3629]  Yergeau, F., "UTF-8, a transformation format of ISO
              10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November
              2003, <https://www.rfc-editor.org/info/rfc3629>.

   [RFC4271]  Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
              Border Gateway Protocol 4 (BGP-4)", RFC 4271,
              DOI 10.17487/RFC4271, January 2006,

   [RFC4486]  Chen, E. and V. Gillet, "Subcodes for BGP Cease
              Notification Message", RFC 4486, DOI 10.17487/RFC4486,
              April 2006, <https://www.rfc-editor.org/info/rfc4486>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8203]  Snijders, J., Heitz, J., and J. Scudder, "BGP
              Administrative Shutdown Communication", RFC 8203,
              DOI 10.17487/RFC8203, July 2017,

8.2.  Informative References

   [RFC4272]  Murphy, S., "BGP Security Vulnerabilities Analysis",
              RFC 4272, DOI 10.17487/RFC4272, January 2006,

   [RFC5424]  Gerhards, R., "The Syslog Protocol", RFC 5424,
              DOI 10.17487/RFC5424, March 2009,

   [RFC6973]  Cooper, A., Tschofenig, H., Aboba, B., Peterson, J.,
              Morris, J., Hansen, M., and R. Smith, "Privacy
              Considerations for Internet Protocols", RFC 6973,
              DOI 10.17487/RFC6973, July 2013,

   [UTR36]    Davis, M. and M. Suignard, "Unicode Security
              Considerations", Unicode Technical Report #36, August
              2010, <http://unicode.org/reports/tr36/>.

Appendix A.  Acknowledgements

   The authors would like to gratefully acknowledge Tom Scholl, David
   Freedman, Jared Mauch, Jeff Haas, Peter Hessler, Bruno Decraene, John
   Heasley, Peter van Dijk, Arjen Zonneveld, James Bensley, Susan Hares,
   Saku Ytti, Lou Berger, Alvaro Retana, and Adam Roach.

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   The authors would like to thank Enke Chen and Vincent Gillet for
   their work on [RFC4486] and granting the related BCP 78 rights to the
   IETF Trust.

   The authors would like to acknowledge Misha Grishin (MSK-IX) for
   raising awareness that [RFC8203]'s length specification was
   insufficient in context of multibyte character sets.

Appendix B.  Changes to RFC 8203

   The maximum permitted length was changed from 128 to 255.

   Feedback from operators based in regions which predominantly use
   multibyte character sets, showed that messages similar in meaning to
   what can be send in other languages in using single-byte encoding,
   failed to fit within the Length constraints as specified by
   [RFC8203].  For example, the phrase: 'Planned work to add switch to
   stack.  Completion time - 30 minutes' has length 65 bytes.  Its
   translation in Russian
   &#1088;&#1072;&#1073;&#1086;&#1090;&#1099; &#1087;&#1086; &#1076;&#10
   86;&#1073;&#1072;&#1074;&#1083;&#1077;&#1085;&#1080;&#1102; &#1082;&#
   &#1089;&#1090;&#1077;&#1082;.&#1042;&#1088;&#1077;&#1084;&#1103; &#10
   79;&#1072;&#1074;&#1077;&#1088;&#1096;&#1077;&#1085;&#1080;&#1103; -
   30&#1084;&#1080;&#1085;&#1091;&#1090;' (See PDF for non-ASCII
   character string) has length 139 bytes.

Authors' Addresses

   Job Snijders
   NTT Communications
   Theodorus Majofskistraat 100
   Amsterdam  1065 SZ
   The Netherlands

   Email: job@ntt.net

   Jakob Heitz
   170 West Tasman Drive
   San Jose, CA  95134
   United States of America

   Email: jheitz@cisco.com

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   John Scudder
   Juniper Networks
   1194 N. Mathilda Ave
   Sunnyvale, CA  94089
   United States of America

   Email: jgs@juniper.net

   Alexander Azimov

   Email: a.e.azimov@gmail.com

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