BGP-add-path analyser


The IDR working group of the IETF has worked during the last years on
the development of BGP extensions that allow a BGP router to advertise
several paths towards the same prefix over a BGP session. This feature,
usually called add-apths, is being implemented by router vendors and
network operators are considering its deployment.

To allow network operators to better understand the possible impact of
BGP add-path in their network, we have enhanced a BGP simulator to
support this feature and developped an analyser on top of this
simulator. Based on a model of the network that can be developped with
the IGP topology, the iBGP sessions and the routes received over eBGP
sessions, the analyser computes metrics such as :

- Number of messages exchanged (eBGP, iBGP, withdraws, updates) during
an event
- Control plane convergence time (time between first and last BGP
message) of an event
- Number of paths in Adj-Rib-Ins
- Availability of path diversity (at least two different nexthops) for
fast convergence
- Path optimality for Hot Potato Routing (IGP costs to the nexthops)

The simulator supports the different add-path selection modes that are
discussed with the IETF.

We have used the tool on the Abilene network whose configuration is
publically available and you can find the results at

The simulator and the analyser tool were written by Virginie Van den
Schrieck. They are both publically available :

Feel free to contact Virginie for additional information or if you would
like to use the analyser on your network.

Best regards,

Olivier Bonaventure