Re: Routing and signaling across devices with different switching cap abilities

[Dimitri.Papadimitriou@alcatel.be]

hi,

Pandian, Vijay wrote:
> Consider a mix of devices with varying switching capabilities connected as
> follows:
>
>      PSC-1 <===> TDM-1 <===> LSC-1 <===> FSC <===> LSC-2 <===> TDM-2 <===>
> PSC-2
>
> Is it fair to assume that PSC-1 and PSC-2 would advertise TE-LSA's with
> "PSC" as the switching capability, TDM-1 and TDM-2 would advertise TE-LSA's
> with "TDM" as the switching capability, LSC-1 and LSC-2 would advertise
> TE-LSA's with "LSC" as the switching capability...?

what "fair" means in this context ? further the hierarchy refers
to region boundaries as follows:

PSC-1 < PSC-2 < PSC-3 < PSC-4 < L2SC < TDM < LSC < FSC

so assuming you're using different values (non-reported in gmpls- 
routing see below) for TDM and LSC, GMPLS mandates that for inst.
you're crossing region boundary at [TDM,LSC] the LSR at the edge
of the TDM region must capable to find [LSC,TDM], and if such
boundary doesn't exist it is fair to assume that the LSP will not
be established - note that we've specific values for L2SC (51),
TDM (100), LSC (150) and FSC (200) so what are you inferring with
TDM-1 and TDM-2 ?

> Given this, would the PSC device (say PSC-1) be able to compute a path using
> CSPF to PSC-2?

well why don't you use the value defined in gmpls-routing, instead
of trying to assess a rule for SC relationship that doesn't exist ?

> There had been some discussion regarding the type of label (SUKLM vs. lambda
> vs. port) to be used across these switching capabilities. How about the
> "LSP-Enc. Type", and "Switching Type" in the Generalized Label Request
> Object? How about the Bandwidth Encoding in the SENDER_TSPEC and FLOWSPEC
> object?

what's more precisely the question here ?

> According to rfc3471, section 3.1.1, the switching type is expected to map
> to one of the values advertised for the corresponding link. In that case,
> would the LSC-device accept a Generalized Label Request with TDM switching
> capability and "port" as the label coming from the TDM capable device?

i think we've sorted out this issue, during our previous discussion,
and the response is "the LSC interface accepts a Generalized Label 
Request with LSC switching capability and "port" as the label coming 
from the TDM capable device" i guess you mean when crossing the 
[TDM,LSC] boundary

> Any clarification on this is appreciated...
>
> Thanks,
>
> Vijay
>
> PS: During various GMPLS interop events, an additional FSC (and LSC?)
> switching capability in the TE-LSA's was required for the end devices to
> compute path.

yes, because some people didn't quite accurately translated the term 
"port" in their implementation ("port" =/= "physical port" such as a
fiber), but as discussed this is erroneous

hope this clarifies,
- dimitri.
--
Papadimitriou Dimitri
E-mail : dimitri.papadimitriou@alcatel.be
E-mail : dpapadimitriou@psg.com
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