Re: [mpls] p2mp BFD over MPLS LSP

Greg Mirsky <> Wed, 17 October 2018 15:56 UTC

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From: Greg Mirsky <>
Date: Wed, 17 Oct 2018 08:56:09 -0700
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To: Gyan Mishra <>
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Subject: Re: [mpls] p2mp BFD over MPLS LSP
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Hi Gyan,
if the application requires protection switchover to be performed by the
head of the p2mp LSP, then you may take advantage of p2mp BFD with active
tails. I think that it is a more suitable mode of p2mp BFD for such
scenario. For the case of 1+1 protection p2mp BFD without active tails
seems an appropriate choice.


On Wed, Oct 17, 2018 at 7:58 AM Gyan Mishra <> wrote:

> Thanks Greg for the thorough explanation.
> P2MP BFD over mpls lsp so that could be mldp or TE p2mp lsp correct and
> for either if protection is done at the head of the lsp which would be the
> FEC root you would not need the P2MP bfd with active tail spec.
> Thank you
> Gyan
> Gyan
> On Mon, Oct 15, 2018, 10:44 AM Greg Mirsky <> wrote:
>> Hi Gyan,
>> thank you for your very pointed question. The base specification for BFD
>> in multipoint networks (often referred to as "p2mp BFD") explains that in
>> p2mp and mp2mp MPLS LSP cases p2mp BFD MAY use IP/UDP encapsulation in
>> Section 5.8:
>>    For multipoint LSPs, when IP/UDP encapsulation of BFD control packets
>>    is used, MultipointTail MUST expect destination UDP port 3784.
>>    Destination IP address of BFD control packet MUST be in
>>    range for IPv4 or in 0:0:0:0:0:FFFF:7F00:0/104 range for IPv6.  The
>>    use of these destination addresses is consistent with the
>>    explanations and usage in [RFC8029].  Packets identified as BFD
>>    packets MUST be consumed by MultipointTail and demultiplexed as
>>    described in Section 5.13.2.  Use of other types of encapsulation of
>>    the BFD control message over multipoint LSP is outside the scope of
>>    this document.
>> In some environments using IP/UDP encapsulation for BFD Control packet is
>> overburden, and this draft explains how p2mp BFD must be used with G-ACh
>> encapsulation. Both types, IP/UDP and G-ACh, may be used to monitor MVPN.
>> Additionally, note that the base p2mp BFD mode does not support tail
>> notification of the path failure to the head. If the protection action to
>> be performed not by the tail but the head, you'd need to use BFD for
>> Multipoint Networks with Active Tail specification. G-ACh encapsulation may
>> be used in any of these specs.
>> Regards,
>> Greg
>> On Sat, Oct 13, 2018 at 7:14 PM Gyan Mishra <>
>> wrote:
>>> Hi Greg
>>> So this Draft would support BFD with IPv6 encap along with the IPV4
>>> encap for P2MP MVPN LSP so would this support all MVPN profiles.
>>> Thank you
>>> Gyan
>>> On Sat, Oct 13, 2018, 4:25 PM Greg Mirsky <> wrote:
>>>> Dear WG Chairs, et al.,
>>>> as the author of the BFD for Multipoint Networks over
>>>> Point-to-Multi-Point MPLS LSP (draft-mirsky-mpls-p2mp-bfd) I would like to
>>>> ask you to consider WG adoption call of the draft. The document addresses
>>>> non-IP encapsulation of p2mp BFD over MPLS LSP that may be useful if the
>>>> overhead of IP, particularly IPv6, encapsulation is the concern. The base
>>>> specification of BFD for Multipoint Networks is at this time in IESG LC.
>>>> Regards,
>>>> Greg
>>>> _______________________________________________
>>>> mpls mailing list