Thank you Curtis,
We opened
https://github.com/IETF-OPSAWG-WG/draft-opsarea-rfc5706bis/issues/146,
to track this change.
Regards, Benoit
In message <[email protected]>
"Adrian Farrel" writes:
Subject: Call for adoption: draft-opsarea-rfc5706bis-06 (Ends 2025-11-11)
This message starts a 3-week Call for Adoption for this document.
If you are going to use this example you should get the story right.
ORIG:
BGP flap damping [RFC2439] is an example. It was designed to block
high-frequency route flaps; however, the design did not consider the
existence of BGP path exploration / slow convergence. In real
operations, path exploration caused false flap damping, resulting in
loss of reachability. As a result, many networks turned flap damping
off.
NEW:
BGP flap damping [RFC2439] is an example. It was designed to block
high-frequency route flaps. The design did consider the existence
of BGP path exploration / slow convergence with the inclusion of
full BGP path in the stored information. A specific vendor with
memory constrained routers chose to interpret this requirement as
optional in their implementation. Thererfore, in real operations,
path exploration caused false flap damping, resulting in loss of
reachability. As a result, many networks turned flap damping off.
The specific vendor was Cisco which at the time had routers with as
little as 4MB of memory in the field. Storing only the prefix and not
the full path was seen as having less impact on their very limited
memory. Cisco has quite a megaphone and were able to blame the
standard even though lead developers participating in IETF (mostly
Tony Li, but others) were very explicitly told that their
implementation was not compliant and would result in path exploration
false positives. Much of the industry at the time viewed any Cisco
implementation (of any protocol, including BGP itself) as a defacto
standard even if not adherent to IETF standards.
RFC2439:
The AS path is generally included in order to identify downstream
instability which is not being damped or not being sufficiently
damped and is alternating between a stable and an unstable path.
Under rare circumstances it may be desirable to exclude AS path for
all or a subset of prefixes.
Note that RFC2439 explicitly points to the need for AS path to cover
the case of "alternating between a stable and an unstable path" aka
path exploration. Following the rare circumstances statement is a
discussion truncating the AS path for AS sets. At no point in the
document is it implied that an implementation that does not store AS
path at all would work and it is explictly stated why it would not
work.
Curtis
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