[OSPF] Experimental support of OSPFv2 Segment Routing in Free Range Routing

[Olivier Dugeon <[e-mail]>]

Hi all,

We are please to announce that we have added Experimental support of OSPF SR
(draft-ietf-ospf-segment-routing-extensions-24) in Free Range Routing
protocol suite https://frrouting.org

This feature is available on the master branch: 
https://github.com/FRRouting/frr
and will be part of the future 4.0 release.

Supported Features:

* Automatic computation of Primary and Backup Adjacency SID with
Cisco experimental remote IP address
* SRGB configuration
* Prefix configuration for Node SID with optional NO-PHP flag (Linux
kernel support both mode)
* Node MSD configuration (with Linux Kernel >= 4.10 a maximum of 32 labels
could be stack)
* Automatic provisioning of MPLS table
* Static route configuration with label stack up to 32 labels

Interoperability:
* tested on various topology including point-to-point and LAN interfaces
in a mix of Free Range Routing instance and Cisco IOS-XR 6.0.x
* check OSPF LSA conformity with latest wireshark release 2.5.0-rc

Known limitations

* Runs only within default VRF
* Only single Area is supported. ABR is not yet supported
* Only SPF algorithm is supported
* Extended Prefix Range is not supported
* MPLS table are not flush at startup. Thus, restarting zebra process is
   mandatory to remove old MPLS entries in the data plane after a crash of
   ospfd daemon
* With NO Penultimate Hop Popping, it is not possible to express a Segment
   Path with an Adjacency SID due to the impossibility for the Linux 
Kernel to
   perform double POP instruction.

For details implementation & instructions on how to use this new feature,
please consult doc/OSPF-SR.rst.

Regards

FRR team