Extended BGP Administrative Shutdown Communication
NTT Ltd.Theodorus Majofskistraat 1001065 SZAmsterdamNetherlandsjob@ntt.netCisco170 West Tasman DriveSan JoseCA95134United States of Americajheitz@cisco.comJuniper Networks1133 Innovation WaySunnyvaleCA94089United States of Americajgs@juniper.netYandexUlitsa Lva Tolstogo 16Moscow119021Russian Federationa.e.azimov@gmail.com
Routing
IDRBGPceaseshutdownThis document enhances the BGP Cease NOTIFICATION message "Administrative
Shutdown" and "Administrative Reset" subcodes for operators to transmit a
short free-form message to describe why a BGP session was shut down 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.IntroductionIt can be troublesome for an operator to correlate a BGP-4 session teardown in the network with a notice that
was transmitted via offline methods, such as email or telephone calls. This document
updates by specifying a mechanism to
transmit a short free-form UTF-8
message as part of a Cease NOTIFICATION
message to inform the peer why the BGP session is being shut down or reset.
This document obsoletes ; the specific
differences and rationale are discussed in detail in .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
when, and only when, they appear in all capitals, as shown here.
Shutdown CommunicationIf 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" , 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:
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 .
Mechanisms concerning the reporting of information contained in
the Shutdown Communication are implementation specific but
SHOULD include methods such as syslog.
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 should be a log message.
If a Shutdown Communication of any length is sent to a BGP
speaker that implements neither [RFC8203] nor this specification,
then that speaker will treat it as
an error, the consequence of which should be 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 as their
sole form of communication with their peers 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.
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.
IANA ConsiderationsIANA has referenced this document at subcodes "Administrative Shutdown"
and "Administrative Reset" in the "BGP Cease NOTIFICATION message subcodes"
registry under the "Border Gateway Protocol (BGP) Parameters" group in addition to
.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 to learn about these issues.
UTF-8 "Shortest Form" encoding is REQUIRED to guard against the technical issues outlined in .
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 they 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 and .
Users of this mechanism should consider applying data minimization practices
as outlined in
because a received Shutdown Communication may be used at the receiver's discretion.ReferencesNormative ReferencesInformative ReferencesUnicode Security ConsiderationsChanges to RFC 8203The maximum permitted length was changed from 128 to 255.Feedback from operators based in regions that predominantly use multibyte character
sets showed that messages similar in meaning to what can be sent in other languages
using single-byte encoding failed to fit within the length constraints as specified by
. For example, the phrase "Planned work to add
switch to stack. Completion time - 30 minutes" has a length of 65 bytes. Its translation in
Russian has a length of 139 bytes.If a Shutdown Communication message longer than 128 octets is sent to a BGP speaker
that implements , then that speaker will bring
it to the attention of an operator but will otherwise process the NOTIFICATION message
as normal.AcknowledgementsThe authors would like to gratefully acknowledge ,
, , , , , , ,
, , , , ,
, and .The authors would like to thank and for their work on and granting the related BCP
78 rights to the IETF Trust.The authors would like to acknowledge (MSK-IX) for raising
awareness that the length specification of was insufficient
in context of multibyte character sets.