Re: Can Multihop BFD be protected using RLFA backup?

Muthu Arul Mozhi Perumal <> Thu, 17 January 2019 11:02 UTC

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From: Muthu Arul Mozhi Perumal <>
Date: Thu, 17 Jan 2019 16:32:21 +0530
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Subject: Re: Can Multihop BFD be protected using RLFA backup?
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Hi Stephane,

Thanks for your response. Please see inline..

On Thu, Jan 17, 2019 at 3:27 PM <> wrote:

> Hi,
> I think that the fact that “control” packets can benefit of FRR is really
> implementation dependent. It is also linked to the place where BFD packets
> are created (RP or LC).
> From a theoretical point of view, nothing prevents FRR to be used as for
> any packet generated by the router itself.

Do we know of any implementation that provides RLFA FRR protection to
multihop BFD packets?

> Regarding the encapsulation, if your BFD client is using RFC5883, this
> will not change during FRR, the FRR will just push labels on top
> independently.

The primary reason for my question on encapsulations is because RFC 4379
has the foll. as one of the reasons for using the destination address
in 127/8 range for IPv4 (0:0:0:0:0:FFFF:7F00/104 range for IPv6) for
diagnostic packets sent over MPLS LSP:
   1. Although the LSP in question may be broken in unknown ways, the
      likelihood of a diagnostic packet being delivered to a user of an
      MPLS service MUST be held to an absolute minimum.

Since multihop BFD uses a routable destination address, wondering whether
there would be any issues if multihop BFD packets are sent over the RLFA
backup path without following RFC 5884 encapsulation..


> Again, the possibility to get FRR is really implementation dependent, as
> the forwarding decision of the BFD packet may not be taken by the network
> processor of the LC.
> Brgds,
> *From:* Rtg-bfd [] *On Behalf Of *Muthu
> Arul Mozhi Perumal
> *Sent:* Thursday, January 17, 2019 10:16
> *To:*
> *Subject:* Can Multihop BFD be protected using RLFA backup?
> Hi All,
> Multihop BFD (RFC 5883) packets are sent over UDP/IP. The encapsulation
> used is identical to single hop BFD (RFC 5881) except that the UDP
> destination port is set to 4784.
> Now, suppose on the ingress node there is no IP/LFA backup path for the
> destination address tracked by multihop BFD, but there exists an an RLFA
> backup path to that destination. In this case, is multihop BFD expected to
> be protected using the RLFA backup path i.e should multihop BFD packets be
> sent over the RLFA backup path if the primary path goes down?
> If multihop BFD packets are to be sent over the RLFA backup path, what
> encapsulation should the ingress use? The encapsulation specified in RFC
> 5883 or the encapsulation specified in RFC 5884 (MPLS BFD)?
> Please let me know you opinion.
> Regards,
> Muthu
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