IDR                                                          J. Snijders
Internet-Draft                                                       NTT
Obsoletes: 8203 (if approved)                                   J. Heitz
Updates: 4486 (if approved)                                        Cisco
Intended status: Standards Track                              J. Scudder
Expires: March 22, April 17, 2021                                          Juniper
                                                               A. Azimov
                                                                  Yandex
                                                      September 18,
                                                        October 14, 2020

           Extended BGP Administrative Shutdown Communication
                      draft-ietf-idr-rfc8203bis-07
                      draft-ietf-idr-rfc8203bis-08

Abstract

   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 of up to 255 octets to improve communication
   using multibyte character sets.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "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
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   This Internet-Draft will expire on March 22, April 17, 2021.

Copyright Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   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.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   5   6
   Appendix A.  Acknowledgements . . . . . . . . . . . . . . . . . .   6
   Appendix B.  Changes to RFC 8203  . . . . . . . . . . . . . . . .   6
   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 as 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
   "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
      Reset").

   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 NUL terminated.  UTF-8 "Shortest Form"
      encoding is REQUIRED to guard against the technical issues
      outlined in [UTR36].

   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
   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 should be a log message.  For this
   reason, operators would be wise to keep shutdown communications to
   less than 128 octets when feasible.

   There

   If a Shutdown Communication of any length is no guarantee sent to a BGP speaker
   that the receiver supports either implements neither [RFC8203] nor this
   specification or [RFC8203], so any shutdown communication might not
   be logged in specification, then that
   speaker will treat it as an easily-readable form at all.  Therefore, operators
   would also error, the consequence of which should be wise not
   a log message.

   In any case, a receiver of a NOTIFICATION message is unable to
   acknowledge the receipt and correct understanding of any Shutdown
   Communication.

   Operators should not rely on shutdown communications Shutdown Communications as their sole
   form of communication with their peer for important events.

   If it is known that the peer BGP speaker supports this specification,
   then a Shutdown Communication that is not longer than 255 octets MAY
   be sent.  Otherwise, a Shutdown Communication MAY be sent, but it
   SHOULD NOT be longer than 128 octets.

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

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

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
   attack.

   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.

7.  References

7.1.  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,
              <https://www.rfc-editor.org/info/rfc2119>.

   [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,
              <https://www.rfc-editor.org/info/rfc4271>.

   [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>.

7.2.  Informative References

   [RFC4272]  Murphy, S., "BGP Security Vulnerabilities Analysis",
              RFC 4272, DOI 10.17487/RFC4272, January 2006,
              <https://www.rfc-editor.org/info/rfc4272>.

   [RFC5424]  Gerhards, R., "The Syslog Protocol", RFC 5424,
              DOI 10.17487/RFC5424, March 2009,
              <https://www.rfc-editor.org/info/rfc5424>.

   [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,
              <https://www.rfc-editor.org/info/rfc6973>.

   [RFC8203]  Snijders, J., Heitz, J., and J. Scudder, "BGP
              Administrative Shutdown Communication", RFC 8203,
              DOI 10.17487/RFC8203, July 2017,
              <https://www.rfc-editor.org/info/rfc8203>.

   [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.

   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 has length 139 bytes.

   If a Shutdown Communication message longer than 128 octets is sent to
   a BGP speaker that implements [RFC8203], then that speaker will bring
   it to the attention of an operator, but will otherwise process the
   NOTIFICATION message as normal.

Authors' Addresses

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

   Email: job@ntt.net

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

   Email: jheitz@cisco.com

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

   Email: jgs@juniper.net

   Alexander Azimov
   Yandex

   Email: a.e.azimov@gmail.com