Appendix A. Transition Considerations for BGP Implementers

This appendix is not normative.

For an implementer, transitioning to a compliant BGP implementation may require a process that can take several years.

It is understood and acknowledged that operators who are taking advantage of an undefined behavior will always be surprised by changes to said behavior.

A.1. "N+1 N+2" Release Strategy

An implementer could leverage an approach described as the "N+1 and N+2" release strategy. In release N+1, the implementer introduces a new default configuration parameter to indicate that the BGP speaker is operating in "ebgp insecure-mode". In addition to the introduction of the new parameter, an implementer could begin to display informational warnings to the operator that certain parts of the configuration are incomplete. In release N+1, operators of the BGP implementation become aware that a configurable default exists in the implementation, and can prepare accordingly. In release N+2 or later, the inverse of the previous default configuration parameter that was introduced in release N+1 becomes the new default.

As a result, any new installation of release N+2 will adhere to this document. Installations upgraded from version release N+1 will adhere to the previous insecure behavior, if no modification was made to the "ebgp insecure-mode" configuration parameter.