Re: [babel] Shepherd Review of draft-ietf-babel-source-specific-04

[Juliusz Chroboczek <[e-mail]>]

>>>> I see.  So your current behaviour can be described by
>>>> 
>>>>   MUST drop the enclosing TLV and MAY drop the whole packet
>>>> 
>>>> May the MUST be a SHOULD, or must it be a MUST?

>>> If it's a SHOULD, what is one supposed to do instead if deciding not to
>>> drop?

>> It's not required to detect the situation -- we're in nasal daemons
>> land.

> That sorta feels under-specified to me?

Babel is a distributed algorithm, and its correctness relies on all nodes
in a routing domain behaving correctly.  There are many ways in which
a buggy or malicious node can disrupt a Babel network, and an
implementation is not required to detect most of them.  (The most common
in production is a node that announces a route but doesn't actually
forward packets, e.g. due to a mis-configured firewall.)

What Donald is requesting here is that we add a requirement that every
implementation should detect one particular (and rather unlikely) instance
of incorrect behaviour, and work around it.  I don't necessarily agree
with this requirement, but I am willing to put it in if the implementation
cost is low enough.

Assuming we put that requirement in, should we mandate (MUST) that all
implementations detect that incorrect situation and work around it, or
should we merely recommend (SHOULD) that they do?  Please keep in mind
that the situation identified by Donald is rather unlikely to occur in
practice, while the implementation cost will be carried by all implementations.

-- Juliusz