Re: [mpls] Alvaro Retana's No Objection on draft-ietf-mpls-lsp-ping-lag-multipath-06: (with COMMENT)

Alvaro Retana <> Thu, 14 March 2019 03:30 UTC

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From: Alvaro Retana <>
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Date: Wed, 13 Mar 2019 23:30:42 -0400
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Subject: Re: [mpls] Alvaro Retana's No Objection on draft-ietf-mpls-lsp-ping-lag-multipath-06: (with COMMENT)
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On March 13, 2019 at 10:14:42 AM, Mach Chen ( wrote:




> (2) §6: "Otherwise, if the responder does not know the LSR Capability
TLV, an

> MPLS echo reply with the return code set to "One or more of the TLVs was
> not understood" MUST be sent back to the initiator LSR." Given that this
> the case where the new TLV is not known, then we can't Normatively direct
> those nodes to do anything (since they probably don't implement anything
> this document). s/MUST/must + add a reference to rfc8029 (where the
> behavior is
> specified) [The same text appears again in §3 and §3.2. Writing the
> specification is one place is enough.]

It's more accurate to call it a "Mandatory" TLV that does not require an
implementation has to implement it, but will result in return code when a
node does not support it, as specified in RFC8029.

Maybe we could just remove the "optional", and make it clear to the IANA
section, the code point of this TLV should be allocated from the Mandatory
range. How do you think?

I think that optional should explicitly be replaced with mandatory…. And,
the IANA section should be clarified to indicate the range.


> (3) This document doesn't talk about what should be done if a response is
> not received, at any point in the process. I searched in rfc8029, but
> find anything related to timeouts...only §4.8 (Non-compliant Routers),
> includes a process on what to do if a reply is not received. That process
> doesn't seem to apply to this document -- what should an initiator do if a

> reply is not received? I am specially interested in the discovery phases.

Normally, the timeout process is left the implementation (e.g., through

If a reply cannot be received within a certain period, the initiator will
return timeout. That means there some issues along the path, operator
should intervene then. a log/notification of some kind should be raised.

During the discovery process, it looks like some things could be specified
without operator intervention.  For example, the capabilities may be
discovered (§3), but the request about the LAG may not be answered.  It
seems to me that the initiator could simply retry…maybe after some retries
the log/notification can be raised.  Just thinking out loud… Either way is
fine with me...