Benjamin,
thanks for review, please see inline (##PP):
On 20/05/2020 00:44, Benjamin Kaduk via Datatracker wrote:
Benjamin Kaduk has entered the following ballot position for
draft-ietf-isis-mpls-elc-12: Discuss
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DISCUSS:
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As for other reviewers, many of my comments duplicate those for the OSPF
document; I expect that the analogous responses apply and am fine if
they only appear for one document's review.
Here, the question I have about normative language applies to the text
in Section 3:
When a router propagates a prefix between ISIS levels ([RFC5302], it
MUST preserve the ELC signaling for this prefix.
The scenario in question is analogous to the OSPF cross-area case: is
the router propagating the prefix between ISIS levels required to
implement this document; is preservation of the flag value a new
requirement from this document vs. a preexisting property; and is this
document trying to make normative requirements of devices that don't
implement this document?
##PP
this is a new requirement and only applies to the routers that support
this document. We are not making normative requirements of devices that
don't implement this document, we cannot.
Maybe we can add that it only applies to the routers that supports this
extension:
"When a router supporting this extension propagates a prefix between
ISIS levels ([RFC5302], it MUST preserve the ELC signaling for this prefix."
Would it work?
Likewise, the ASBR case for cross-protocol redistribution seems to
rather inherently require understanding the semantics of the flags being
translated.
similarly to the above I can chnage to:
"When a router supporting this extension redistribute a prefix ..."
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COMMENT:
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Section 1
Should we add a sentence at the end of the last paragraph about how
"this document defines a mechanism to signal the ERLD using IS-IS"?
not sure I understand, how is described in the body of the document.
In cases where LSPs are used (e.g., SR-MPLS [RFC8660], it would be
side note(?): I don't know that SR-MPLS is so popular so as to be
privileged as the only example given for LSP usage. If we instead
talked about using IGPs to signal labels, this selection would seem less
surprising to me.
this document describes the ELC/ERLD capability signaling for SR MPLS.
For non SR MPLS cases, thee are existing mechanisms to learn ELC/ERLD.
I can replace the text with:
"In cases where SR is used with the MPLS Data Plane"
Would it work?
Section 3
unless all of its interfaces are capable of processing ELs. If a
router supports ELs on all of its interfaces, it SHOULD set the ELC
for every local host prefix it advertises in IS-IS.
Do we want to say anything about (not) advertising the ELC for other
prefixes?
Do we have to? I can add "MUST NOT set ELC with for any other prefix",
but I find it unneeded.
Section 4
I agree with Roman's comment about code 2 vs TBD2.
that has been fixed already.
ERLD in the range between 0 to 255. The scope of the advertisement
depends on the application. If a router has multiple interfaces with
Just to check: w.r.t. "scope", both this document and the OSPF one only
define usage of this MSD type at the scope of a single node, right? (I
don't see a particular reason to preclude using it at a different
scope.)
the scope here means where the information will be flooded - area only
or network wide. No such thing as a node scope.
Section 6
- Bit 3 in the Bit Values for Prefix Attribute Flags Sub-TLV
registry has been assigned to the ELC Flag. IANA is asked to
Is there an "IS-IS" in the name of this registry?
no the registry name is "Bit Values for Prefix Attribute Flags Sub-TLV".
Section 7
Should we say anything about considerations for redistributing ELC/ERLD
information at the ASBR with respect to exposing "internal information"
to external parties?
why would this be "internal information" and why redistribution would be
"external party"? Redistribution between IGPs is predominantly done
between IGPs under same administrative domain.
This document specifies the ability to advertise additional node
capabilities using IS-IS and BGP-LS. As such, the security
considerations as described in [RFC7981], [RFC7752], [RFC7794],
[RFC8491], [RFC8662], [I-D.ietf-idr-bgp-ls-segment-routing-ext] and
RFC 8662's security considerations have a pretty hard dependency on RFC
6790's security considerations; it might be worth mentioning 6790
directly in this list as well.
would not that be implicit when mentioning RFC 8662?
[I-D.ietf-idr-bgp-ls-segment-routing-msd] are applicable to this
document.
Could we also have a brief note that the normal IS-IS authentication
mechanisms serve to protect the ELC/ERLD information?
do we need to repeat this every time we add a bit in the TLV?
Incorrectly setting the E flag during origination, propagation or
redistribution may lead to black-holing of the traffic on the egress
node.
This is what happens when the E flag should not be set but is
erroneously set. Should we also say what happens if we should set the E
flag but erroneously clear it (e.g., that poor or no load-balancing may
occur)?
yes, there is a text there already:
"Incorrectly setting of the ERLD value may lead to poor or no
load-balancing of the traffic."
Section 8
I do see the note in the shepherd writeup about the sixth author (thank
you!); if we're already breaking through the 5-author limit, did we
consider making those who "should be considered as co-authors" listed as
co-authors?
I'm not fun of this 5 authors rule to be honest.
Section 10.1
Should we reference RFC 7981 from Section 4 as well? Right now we seem
to only use it for the security considerations, which is not necessarily
enough to qualify it as a normative reference.
we reference RFC8491, which references RFC 7981. I don't see a need to
reference RFC 7981 directly.
thanks,
Peter
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