[Pce] A discussion point for draft-ietf-pce-pcep-flowspec

["Adrian Farrel" <[e-mail]>]

Hi WG,

I received a couple of private emails about draft-ietf-pce-pcep-flowspec.

Since they were private, I will try to be circumspect about who they were
from.

The sender asked to have a flag attached to a flow specification that
indicates that it can be installed as a static route and thus not subject to
a firewall rule so the longest prefix matching can be performed to
manipulate route resolution for an LSP.

The request also said that traditionally flow-specifications result in
firewall rules and those rules operate on packets before longest prefix
match. We want to install static routes, the equivalent of installing a
prefix for an LSP and if we treat a flowspec as a static route we can mess
things up like rule ordering and so on.

The sender suggested that there are currently some draft(s) regarding this
behavior for BGP flowspec as well, but was not able to point me at them.

I asked for some clarifications and got back:

"What BGP-FS does is install data-plane filters.  We handle that by
installing RIB entries (that's what BGP carries) into a RIB. Those entries
are transformed into firewall filters.  What I am asking for is not
currently supported by BGP-flowspec.

"What I am asking for is an indication that a flow-specification NOT be
transformed into a data-plane filter.  In other words, installed as a normal
route where the route is subject to longest prefix match based forwarding.
If you consider how we had to implement the multicast support for PCEP
flowspec, it is quite similar.  So, in my mind, the 'flag' is an indicator
to do LPM for a destination.  Presence of the flag also means that no other
fields can be present in the flowspec, e.g. source address or dest/src L4
ports, etc."

In my view, it should not be too hard to add a flag to the PCEP flow
specification.

But a couple of questions for the working group and my co-authors:
- Does anyone else have interest in this work?
- Can anyone else identify the related BGP work?
- Does anyone want to suggest text for this?
- Is this something we should leave as a future extension that can be
proposed if/when someone cares about it?

I suspect that the default position is "do nothing" and ask Julien to move
the draft forward, so if you care please speak up.

Thanks,
Adrian