[PATCH RFC 1/1] Add the Babel routing protocol (RFC 6129) to Bird.

Juliusz Chroboczek jch at pps.univ-paris-diderot.fr
Tue Aug 25 20:34:35 CEST 2015

>> BTW, the argumentation in 3.5.5 of RFC 6126 seems a bit strange to me.
>> It essentially says that unreachable routes are added to avoid transient
>> routing loops before Babel converges. But transient routing loops until
>> convergence is a common behavior for IGPs (both RIP, OSPF and IS-IS do
>> that), while blackholing may be far less expected behavior, esp. if it is
>> for several minutes, which is far longer time than usually necessary for
>> protocol convergence.

Yes.  Babel is designed to be robust not only on wired networks (where
OSPF and IS-IS work just fine), but also on wireless mesh networks, where
a routing loop, even a transient one, causes cross-link interference and
may prevent the routing protocol from reconverging.  For that reason,
Babel prefers to blackhole rather than risking to create a routing loop.

>> It seems more like local policy setting than something which should be
>> part of protocol specification.

I agree, it could perhaps be disabled on some kinds of links.

-- Juliusz

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