Re: [OSPF] FYI on draft-kini-ospf-fast-notification-01

[Wenhu Lu <[e-mail]>]

FYI the authors and Manav had a good hall way talk and it turned out that we need some clarifications:
1. the fast-notification is a special packet created and sent upon certain events such as a link breakage. The normal ospf packets like hello, dd, lsa will go as is and will not be "fast-flooded".
2. the special fn packets can be either a newly defined packet format, or just an LSA but with a pre-defined multicast group address MC-FN (c.f. draft) which is different than regular OSPF group addresses.
3. Only fn packets will be put on and flooded through the said multicast trees. Other type of packets will not.
4. The dampening mechanism will be placed in the forwarding plane to prevent the potential DoS attacks.

We plan to update our draft to a newer version which will include more clarifications.
We thank Manav and others for many constructive comments and questions.
In the meanwhile, we welcome and solicit more comments and suggests and we will incorpate them into the next revision.

Thank you,
-wenhu

________________________________
From: Bhatia, Manav (Manav) [mailto:[e-mail]]
Sent: Wednesday, March 30, 2011 5:29 AM
To: Wenhu Lu; Sriganesh Kini
Cc: [e-mail]
Subject: RE: [OSPF] FYI on draft-kini-ospf-fast-notification-01

Hi Wenhu,

I am trying to say this:

If you dont do verification in HW then you leave a hole open for DoS, which means that you MUST do verification before flooding. However, this is easier said than done, and its extremely complex and convoluted to do this in HW.

And this is precisely why i had said "I'm saying that either ways you have an issue." in my last mail that you responded to.

Cheers, Manav
________________________________
From: Wenhu Lu [mailto:[e-mail]]
Sent: Wednesday, March 30, 2011 5.51 PM
To: Bhatia, Manav (Manav); Sriganesh Kini
Cc: [e-mail]
Subject: RE: [OSPF] FYI on draft-kini-ospf-fast-notification-01

Hi Manav,
If I read it correctly, your original message said there would be a hole if we don't do verification in data plane. Now you are saying you never asserted it would, I'm confused.
As Sri mentioned, the rate limiting should solve the problem easily.

Thanks,
-wenhu

________________________________
From: Bhatia, Manav (Manav) [mailto:[e-mail]]
Sent: Wednesday, March 30, 2011 5:05 AM
To: Wenhu Lu; Sriganesh Kini
Cc: [e-mail]
Subject: RE: [OSPF] FYI on draft-kini-ospf-fast-notification-01

Hi Wenhu,

I never asserted they would - If you claim to do auth verification in HW then you would presumably take care of this as well.

I'm saying that either ways you have an issue.

Cheers, Manav

________________________________
From: Wenhu Lu [mailto:[e-mail]]
Sent: Wednesday, March 30, 2011 5.31 PM
To: Bhatia, Manav (Manav); Sriganesh Kini
Cc: [e-mail]
Subject: RE: [OSPF] FYI on draft-kini-ospf-fast-notification-01

Hi Manav,
How would the data-plane auth verification prevent such DoS attacks?
Any replayed packets will go through.

Thanks,
-wenhu

________________________________
From: [e-mail] [mailto:[e-mail]] On Behalf Of Bhatia, Manav (Manav)
Sent: Wednesday, March 30, 2011 12:55 AM
To: Sriganesh Kini
Cc: [e-mail]
Subject: Re: [OSPF] FYI on draft-kini-ospf-fast-notification-01

Hi Sri,

This is regarding the point that i had raised yesterday - If the routers flood the "LSAs" in the data plane without verifying them, then we're leaving a hole open for DoS attacks, as any packet masquerading as a legitimate OSPF packet will get flooded on all routers. This is different from data packets flooding as these packets will be occupying the higest priority queues in both the ingress, egress and the CPU.

Second, what happens if the control packet is carrying an OSPF authentication digest? Would you still flood it without verifying the contents or would those be flooded regardless? I guess, you said that it would be the former. If thats the case, then this is not easy to do it in the HW as you would (i) need to parse the OSPF payload first to determine that its carrying a digest (ii) you would then need to verify it, which means you would be running HMAC-SHA in HW on the packet (given the Apad stuff that we have added in RFC5709 i dont think you can easily do this in HW) (iii) once the digest is verified you would need to flood it out on all the valid OSPF interfaces.

Cheers, Manav
________________________________
From: [e-mail] [mailto:[e-mail]] On Behalf Of Sriganesh Kini
Sent: Tuesday, March 29, 2011 9.20 PM
To: [e-mail]
Subject: [OSPF] FYI on draft-kini-ospf-fast-notification-01

Just an FYI to the list

This draft http://tools.ietf.org/html/draft-kini-ospf-fast-notification-01 was presented at the OSPF WG mtg today.

Thanks for the comments/questions at the mic. We will submit a new version addressing the comments.

Note that the other drafts related to Fast Notification (FN) are draft-lu-fn-transport and draft-lu-fast-notification-framework. These were presented in RTGWG.

Thanks

- Sri