Re: [mpls] Opsdir last call review of draft-ietf-mpls-spring-entropy-label-11

[<[e-mail]>]

Hi Joe,

Thanks for your comments.
I have fixed the nits as part of the next revision.
I have clarified also some points that you have mentioned, please see inline.

Brgds,

Stephane


-----Original Message-----
From: Joe Clarke [mailto:[e-mail]] 
Sent: Monday, June 25, 2018 16:39
To: [e-mail]
Cc: [e-mail]; [e-mail]; [e-mail]
Subject: Opsdir last call review of draft-ietf-mpls-spring-entropy-label-11

Reviewer: Joe Clarke
Review result: Has Nits

I have been asked to review this document on behalf of the ops directorate.  I
know my review is a few days late, but I hope it will still be of some use.

This document describes how to use/place entropy labels in a SPRING path over
an MPLS dataplane for purposes of optimizing load balancing.  Overall, I think
the document is ready, but I did have a couple of operational
questions/comments and found a number of nits.

I found a couple of MAY requirements in here that I feel should be stronger or
offer some additional recommendation (mainly to favor operators or help guide
vendors).  First, section 4 states "For simplicity, an implementation MAY use
the minimum ERLD between each linecard as the ERLD value for the system."  I
feel there should be a stronger recommendation on what to do here given that
ERLD is later described as a key piece of the algorithm for EL placement.  A
vendor may opt for the simple approach, but should they consider a more robust
approach to favor operators?

[SLI] Proposed addition:
"The drawback of using a single ERLD for a system lower than the capability of one or more specific component is that it may increase the number of ELI/ELs inserted. This leads to an increase of the label stack size."

Second, section 5 states "this node MAY advertise its MSD value or a subset of
its MSD value to the controller."  It MAY NOT do that, too.  It would be good
to highlight pros and cons to this.

[SLI] Here is the proposal:" As the controller does not have
   the knowledge of the entire label stack to be pushed by the node, the
   node SHOULD advertise an MSD value which is lower than its actual limit. If the node advertises an MSD values equal to its actual limit, the controller could program an LSP using a number of labels equal to the MSD value. When receiving this label stack from the controller, the ingress node may not be able to add any service (L2VPN, L3VPN, EVPN...) label on top of this label stack.  The consequence could be for the ingress node to drop service packets that should have been forwarded over the LSP."



Finally, section 7.2 states "In case of a trade-off, an implementation MAY
provide flexibility to the operator to select the criteria to be considered
when placing EL/ELIs..."  I can see this being of great value to operators to
have vendors allow this.  But as with any MAY, the vendor MAY choose NOT to do
it.  SHOULD seems better here for that reason.

[SLI] Agree that "SHOULD" better fits here

On to the nits:

Section 1

Expand LSP before using

===

Section 1

s/local node who/local node which/

===

Section 1

s/disordering/misordering/

I think the latter makes more sense, yes?

===

Section 2

Add LSP to your list of terminology

===

Section 6

s/destinated/destined/

===

Section 6

s/accomodate/accommodate/

===

Section 7.1.2

s/node has not a sufficient/node does not have a sufficient/

===

Section 7.1.2

<Adj_P1P2, Adj_set_P2P3, Adj_P3P4,
   Adj_P4P5, Adj_P5P6, Adj_set_P6P7, Adj_P7P8; Adj_set_P8PE2,VPN_label>

Note the ';' after Adj_P7P8.  This is a comma everywhere else.  I think it
should be a comma here, too.

===

Section 7.1.2

s/PE1 is limited to push a maximum of 11 labels,/PE1 is limited to push a
maximum of 11 labels./

Note the change of a comma to a period.

===

Section 7.2 and throughout

You use EL/ELI and ELI/EL interchangeably.  For consistency, pick one and go
with it.

===

Section 7.2

s/considered as exhaustive/considered exhaustive/

===

Section 7.2.2.2

I would like to point out that you define an adjacency set as a set of
adjacencies.  Perhaps you want to further refine this to add more clarity.

===

Section 9

s/In future/In the future/

===

Section 9

s/capabilities and may be remove/capabilities and may remove/



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