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.