[dev] OpenFabric now included in FRR

[Christian Franke]

All -

I'm glad to announce the merging of OpenFabric (PR #2875
https://github.com/FRRouting/frr/pull/2875) into master.

OpenFabric (https://tools.ietf.org/html/draft-white-openfabric-06) is
one of the solutions provided for the currently ongoing effort in the
IETF to develop routing protocols which cope well with densely connected
topologies like spine-leaf and clos. For those topologies, established
routing protocols often run into scaling issues because of large fan-out
and the high degree of interconnection.

OpenFabric is based on IS-IS. To improve the scaling properties, it uses
a more optimized flooding algorithm which reduces the number of LSPs
exchanged in the network to the minimum required to update all nodes.

To to test FRR's implementation of OpenFabric, just build and run
fabricd with a configuration as following:

> !
> interface lo
>  ip address 100.0.1.1/32
>  ip router openfabric 1
>  ipv6 address 2001:db8:64::1:1/128
>  ipv6 router openfabric 1
>  openfabric passive
> !
> interface eth0
>  ip router openfabric 1
>  ipv6 router openfabric 1
> !
> [...]
> !
> interface ethX
>  ip router openfabric 1
>  ipv6 router openfabric 1
> !
> router openfabric 1
>  net 49.0001.0001.0001.00
> !
All Best,
Chris