Re: [babel] WG Last Call for draft-ietf-babel-source-specific (2018-03-26 to 2018-04-09)

[Juliusz Chroboczek <[e-mail]>]

> Please correct me if the following interpretation is wrong. There is
> a deployed fleet of RFC 6126 devices and it is not going to disappear
> immediately. There is going to be a deployed fleet of SS-extended
> devices. When the two kinds randomly meet in the wild and
> source-specific routes start to propagate, the network can randomly
> break or degrade.

> Acknowledging the problem in a document is a good start. But ending up
> with a design that fails to fail safe looks wrong.

Babel development tries, to the extent possible, to meet the needs of our
users.  When we decided to go with the mandatory bits (and therefore break
compatibility with 6126), I spoke with a number of users of Babel, some of
them in the live, some of them by e-mail.  I then explained the transition
plan on the babel-users mailing list, no less than three times.

There were no objections.  Our users are worried about a flag day, since
they are unable to update all of their routers in a timely manner.
However, they are not worried about an orderly transition:

  - the next version of babeld will not break compatibility without an
    explicit option;
  - future versions of babeld will have a per-interface flag called
    "rfc6126-compatible" that will cause babeld to remain compatible with
    deployed implementations.

Of course, I have not spoken with every single user of babeld.  However,
I am confident that the above transition plan is the best we can do
without splitting the community into "version 2" and "version 3", which at
this stage would be tantamount to suicide.

-- Juliusz