Hi John/Ben,
Happy New Year!
Both OSPF and IS-IS MSD documents have been published.
Wrt PCE - they merely state that if there’s no PCEP session between nodes
advertising and receiving this information, the receiving node has no other
means to learn the MSD of the advertising node, since it is local to the
node (while IGPs flood it to everyone).
Having this in the IGP drafts and PCE draft stating that if both protocols
advertise MSD, then IGP one should be preferred seemed clear enough (this
had been discussed).
>From granularity prospective - IGPs (BGP-LS) provide more details indeed as
per interface MSD could be advertised (PCEP could do node MSD only).
Hope this clarifies,
Jeff
On Sat, Jan 5, 2019 at 16:39 Benjamin Kaduk wrote:
> On Fri, Dec 21, 2018 at 04:59:28PM +, Jonathan Hardwick wrote:
> > Hi Benjamin
> >
> > Sorry for the delayed response. Please find replies to your comments
> below.
>
> And my apologies as well for waiting until after the holidays to
> counter-respond.
>
> > Best regards
> > Jon
> >
> >
> > Abstract
> >
> >This document specifies extensions to the Path
> >Computation Element Communication Protocol (PCEP) that allow a
> >stateful PCE to compute and initiate Traffic Engineering (TE) paths,
> >as well as a PCC to request a path subject to certain constraints and
> >optimization criteria in SR networks.
> >
> > Why are we talking about TE paths now instead of SR?
> >
> > [Jon] TE is the primary application for SR paths instantiated by a PCE.
> >
> > Section 1
> >
> >Several types of segment are defined. A node segment represents an
> >ECMP-aware shortest-path to a specific node, and is always identified
> >uniquely within the SR/IGP domain. [...]
> >
> > A path to a node is only going to be unique if the starting node is also
> included, is it not?
> >
> > [Jon] I suggest we reword this to make it clearer:
> >
> > OLD
> >A node segment represents an
> >ECMP-aware shortest-path to a specific node, and is always identified
> >uniquely within the SR/IGP domain.
> > NEW
> >A node segment uniquely identifies a specific node in the SR domain.
> >Each router in the SR domain associates a node segment with an
> >ECMP-aware shortest path to the node that it identifies.
> > END
>
> That works for me, thanks.
>
> > Section 3
> >
> > The sentences:
> >
> >In an SR network, the ingress node of an SR path prepends an SR
> >header to all outgoing packets. The SR header consists of a list of
> >SIDs (or MPLS labels in the context of this document).
> >
> > Appear virtually unchanged in both the start of the first paragraph and
> the middle of the second paragraph; is this duplication really needed?
> >
> > [Jon] No - we'll remove the redundant text.
> >
> >A PCC MAY include an RRO containing the recorded LSP in PCReq and
> >PCRpt messages as specified in [RFC5440] and [RFC8231], respectively..
> >This document defines a new RRO subobject for SR networks. The
> >methods used by a PCC to record the SR-TE LSP are outside the scope
> >of this document.
> >
> > It's not entirely clear that we need to define a standard container to
> carry site-local data when a site-local container could also be used.
> >
> > [Jon] Sorry, I don't understand your comment. The RRO is an existing
> PCEP object whose subobjects are used to describe the actual path taken by
> an LSP. We are adding subobjects to represent SIDs.
>
> I'm going from memory, and it's been some time since I read the document
> (so this could well be wrong), but I think I was thinking something like
> "we're defining a new type of subobject to represent SIDs, but the contents
> of that subobject are interpreted in a site-local manner. How is this
> different from just having site-local subobjects, with both the subobject
> type and its contents being site-local matters?" But this was just a
> non-blocking comment to start with, so if it doesn't make sense (or any
> other reason, really), feel free to drop the discussion -- I won't mind.
>
> > Section 5.2
> >
> > Please expand SRP (and RP, for that matter) on first usage.
> > (Interestingly,
> https://www.rfc-editor.org/materials/abbrev.expansion.txt
> > does not seem to have the correct expansion for this usage.)
> >
> > [Jon] Will do.
> >
> > Section 5.3.1
> >
> > * C: If the M bit and the C bit are both set to 1, then the TC,
> > S, and TTL fields in the MPLS label stack entry are specified
> > by the PCE. However, a PCC MAY choose to override these values
> > according its local policy and MPLS forwarding rules. If the M
> > bit is set to 1 but the C bit is set to zero, then the TC, S,
> > and TTL fields MUST be ignored by the PCC. The PCC MUST set
> > these fields according to its local policy and MPLS forwarding
> > rules. [...]
> >
> > Must be ignored in incoming messages received from where?
> >
