Re: [OSPF] OSPF GR and BFD operability

Anil Raj <anilraj85@gmail.com> Tue, 25 August 2015 15:36 UTC

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References: <CAPj3AOpO+o2hBp3J+mPXpwWiho5fMxE97b1SKsHigRfTQSGzjw@mail.gmail.com> <D201F336.2C912%acee@cisco.com>
Date: Tue, 25 Aug 2015 21:06:32 +0530
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From: Anil Raj <anilraj85@gmail.com>
To: "Acee Lindem (acee)" <acee@cisco.com>
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Cc: OSPF WG List <ospf@ietf.org>
Subject: Re: [OSPF] OSPF GR and BFD operability
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Thanks Acee for the details.
My concern was also in regards that, in a BFD-less setup during
helper-mode, OSPF hello packets from the neighbor are not honored at all
and is not used as a heartbeat mechanism, and hence waits for the entire
grace period before announcing the peer down. So any BFD implementation
done on software (may be multi-hop peers if applicable), this may still
cause BFD to cause remote inactivity notification, with data plane still
intact.

Regards,
Anil

On Tue, Aug 25, 2015 at 8:23 PM, Acee Lindem (acee) <acee@cisco.com> wrote:

> Hi Anil,
>
> OSPF and OSPFv3 graceful restart pre-dated BFD so this wasn’t explicitly
> covered. However, given that the intension is that the data plane is
> preserved during restart, an implementation could interpret this as a
> topology change and terminate helper mode as documented in section 3.2 of
> RFC 3623.
> Hope this helps,
> Acee
>
>
>
> From: OSPF <ospf-bounces@ietf.org> on behalf of Anil Raj <
> anilraj85@gmail.com>
> Date: Tuesday, August 25, 2015 at 10:19 AM
> To: OSPF WG List <ospf@ietf.org>
> Subject: [OSPF] OSPF GR and BFD operability
>
> Hi,
>
> I need clarification on the behavior when BFD notifies remote inactivity
> for a OSPF session, when OSPF neighbor is undergoing Graceful restart? OSPF
> router in helper mode will ideally inactivate the restarting neighbor only
> after grace period, and if BFD notifies neighbor down to OSPF, should the
> adjacency be terminated? If not, will it cause a blackhole for the entire
> grace period if the neighbor is actually down?
>
> Appreciate if you can help here.
>
> Regards,
> Anil
>
>