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Re: I-D ACTION:draft-ayyangar-ccamp-lsp-stitching-00.txt

arthi:

which flexibility are we expecting here, this "segment" can accommodate
exactly one incoming request -


IB>> Disagree - the segment could be a component link within a bundle. In
this case stitching FA TE link may accomodate multiple LSPs

additionally only nodes part of the same

area can make use of this advertisement - 

AA-----> I agree with Igor...one of the reasons you advertise an FA is
to attract traffic over that FA, note that it is advertised with
TE metric = (TE metric of FA LSP path - 1) ..... I would think this would
also be the reason to advertise an LSP segment, IF this is desired. Again,
note that this decision is completely local to the node originating the
LSP segment and would be dictated by some policy.

i obviously understand that policy triggers of not such behaviour, the issue i point out is one of the case that could be of interest for inst. multiple path comp. domains within the same area generate the issue of the flooding scope within that area (as the computational domain does not scope the flooding) for the purpose being of attracting on specific segments how to prevent node within the inner "domain" to make use of these segments

this said, in case an advertisement is to be considered rules should also be defined in terms of parameters that would require to be inherited

IB>> Who said that sticthing segments must necessarily terminate on domain
borders? There could be multiple reasons why a network operator could
pre-provision (dynamically or statically) LSP segments inside his network
and advertise them (as bundles or individually) as TE links to be used for
specific TE purposes.


AA----------> Agreed.

thanks,
-arthi


IB>> See my comment above. I might want to use statically provisioned
segments. I might want to use nodes that do not have proper signaling
software.
For instance, recall the discussions on P2MP and how we want use legacy LSRs
to be part of P2MP tunnels


AA-------> Absolutely.


in case of classical FA-LSP it makes sense to advertize the FA link
because it represents a lower region LSP (with usually a given ratio of
unreserved bandwidth that makes worth advertizing the FA link) but in
case of a segment i do have some difficulties to excatly see where this
flexibility would deliver ?


IB>> Again, if you imagine that several parallel sticthing segments are
advertised as as single FA, how it would be different from the bandwidth
usage point of view compared to advertising lower layer FA ? In fact it
would be even more useful, because in case of lower layer FA you need also
to advertise termination/adaptation capabilities, while in case of stitching
FA no addaptation is required.

Igor

thanks,
- dimitri.


thanks,
- dimitri.



a more technical point is related to the definition of an FA LSP 

which

per LSP-Hierarchy mandates crossing LSP region border: the head-end 

and

tail-end switching capability represent the SC of the resulting TE 

link

while intermediate node terminates the SC corr. to the switching type 

of


the FA-LSP (e.g. creation of a [PSC-1,PSC-1] link throughout a PSC-2
capable network with first and last link being [PSC-1,PSC-2] and
[PSC-2,PSC-1], resp.), while in the LSP segment case we would have


now

the creation of a [PSC-1,PSC-1] link with first and last link being
[PSC-1,PSC-1] and [PSC-1,PSC-1], resp. so there is no region border
crossing anymore - so here the question is about definition and
detailing the triggers

AA--------> As far as trigger for setting up an LSP segment is 

concerned,


I agree that there is no longer the notion of "crossing region
boundaries". I realize that the document doesn't discuss this,


especially


given that we are doing other comparisons with FA LSPs. So, I will add
this discussion in the next revision. I think in case of LSP segment


the

trigger for LSP segment setup would come from a) successful switching 

type


and switching capability match and b) some local policy on the node 

which


dictates the setting up of an LSP segment.



IB>> I have a comment here. LSP-Hierarchy is not a Bible and could be
challenged in many ways. FA LSP is, generally speaking, created on a


layer


boundary rather than on region boundary: nothing prevents creating a 

VC4

FA


LSP that starts and stops in the middle of TDM region to carry several 

VC12


LSPs. Furthermore, stitching FA is a special case of FA when it is used 

by


LSPs of the same layer as one where the FA-LSP was created. As for 

triggers,


there could be multiple ones for setting up/tearing down stitching 

FA-LSPs:


configuration, receiving setup request for inter-domain LSP, other 

policies.


Igor






More on a) later.

thanks,
-arthi





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