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Re: I-D ACTION:draft-ietf-ccamp-inter-domain-framework-02.txt (fwd)



Igor Bryskin wrote:


[snip]

I have several comments on the document.

Section 1.1 Nested domains:

For further consideration of nested domains see [MRN]

MRN does not cover nested domains, ITU hierarchical routing does. This
is a hole in (G)MPLS TE


not sure to understand your comment here, in particular when considering
"switching capability domains" - i suggest you take a look for instance
at section 5.1.7 of MRN that provides you an example if this can help
understanding


IB>> I think we have a problem with the definition of a nested routing
domain and this draft is actually a good place to provide such definition.
Here is from MRN 5.17:

In calculating the path for the PSC-LSP, the
        TE database is filtered to include the link, both ends of which
        include only PSC. In this way hierarchical routing of the PSC-
        LSP and TDM-LSP is done by using a TE database filtered with
        respect to switching capability. The hierarchical routing IHMO is
not about filtering TED with respect to switching capability. The computing
entitity in the containing domain cannot do this because it has zero or
limited TED information about nested domains. In my view nesting of routing
domains and nesting of network regions or layers have nothing in common. For
example, nesting of routing domains may happen within a single (say, IP or
ATM) layer.

i don't think you have quite understood the example in the ref'ed section, now as you are moving the debate to hierarchical routing the response to your question is already detailed in the ason req. document section 4.2 - no need to repeat things all over -

Section 2.1 LSP Nesting

FA and FA-LSP are not accurate terms for describing LSP nesting, which
is using an LSP created in one network layer as a data link in other
layer(s). H-LSP (Hierarchical LSP) is a better term. When H-LSP is advertised as a
TE link, the link is not necessarily FA, that is, it may require direct IGP
adjacency between its ends to provide necessary control plane
connectivity.


note: a hierarchical LSP does also translate as (using your words) "LSP
created in one network layer as a data link in other layer(s)" the whole
discussion point here is about the control plane instance and
relationship -


IB>> Despite that you quote my own words I have no idea what you just said
:=) I just want to remind you that in Minneappolis we had a lengthy
discussion (you and Arthi took part in it as well as the authors of LSP-HIER
Yakov and Kireeti) about FA and hierarchical LSPs. We all seemed to agree
that Forwarding Adjacency (FA) is unfortunately confusing name for a TE link
that does not require direct IGP adjacency between its ends for control
plane connectivity, that, although H-LSPs and FAs often come together, they
do not have to relate to each other. The results of this discussionis are
reflected in
www.ietf.org/internet-drafts/draft-ietf-ccamp-gmpls-ason-lexicography-02.txt
, section 3.9

i am not discussing this i just want to highlight that from a data plane perspective relationship is the same, the section could have been called LSP nesting but introducing the distinction between FA's and non FA's based on the control plane relationship

[snip]

Section 2.3 LSP stitching

Again, a stitching segment created in one domain and advertised as a TE
link into a different domain is not an FA, it is just a "regular" TE link not
distinguishable from a TE link supported by static data link(s)

>> indeed this is not an FA (i.e. "LSP segments may be managed as FAs ..." 
- but not for the reason you have indicated - simply because there is no
notion of nesting when considering an LSP segment

IB>> And I repeat again that FA has nothing to do with the nesting

i don't understand your comment the document says "LSP segments MAY be managed as FAs" it could simply add "... or any suitable methods for making these segments usable by nodes not being the head or the tail-end"