Re: Moving right along ... Switching Type

["manoj juneja" <manojkumarjuneja@hotmail.com>]

Hi Dimitri,
            Are SDH/SONET traffic params in SNDER_TSPEC optional ? As
per my understanding these are mandatory as it gives information
regarding SDH/SONET label allocation (i.e. signal type, NCC, NVC, RCC
etc). If SDH/SONET traffic parameters are not present then how can I
determine these fields i.e. NCC, NVC, RCC, signals etc. from switching
type ?

Please correct me if I am wrong.

Regards,
manoj.

>From: Dimitri Papadimitriou <dimitri.papadimitriou@alcatel.be>
>To: Zhi-Wei Lin <zwlin@lucent.com>
>CC: John Drake <jdrake@calient.net>,   "'Ben Mack-Crane'" 
><Ben.Mack-Crane@tellabs.com>,   Kireeti Kompella <kireeti@juniper.net>, 
>ccamp@ops.ietf.org
>Subject: Re: Moving right along ... Switching Type
>Date: Wed, 31 Oct 2001 23:52:16 +0100
>
>Hi,
>
>We have two approaches either "traffic-parameters" are used
>(in SENDER_TSPEC) then i think the Switching Type capability
>is useless or they aren't then such field could be optionaly
>used when applicable (some examples are given in the routing
>document).
>
>Wouldn't be the right way to proceed by defining an "unknown"
>or "unspecified" value used when "traffic-parameters" are
>included within the Path Message and optional use the ones
>proposed in the current version of the specification when they
>aren't. This field is thus optional and MUST only be used when
>traffic parameters are not defined. I think this solves both
>approaches.
>
>I think that also some additional text is needed in order to
>clarify the semantic; the following one can be proposed (after
>having discussed with some individuals):
>"The Switching Type field is provided to allow nodes having
>multiple switching layer capabilities to indicate their
>preference. This field should only be used to indicate the
>link switching preference but not end-to-end switching
>preference".
>
>Notice that some proposal concerning the applicability scope
>have been proposed but never really committed within the I-D.
>
>Cheers,
>- dimitri.
>
>Zhi-Wei Lin wrote:
> >
> > Hi John,
> >
> > > <z>The section you mentioned, from what I can tell, is an example list
> > > of some possible combinations of different equipment functions. I see
> > > them as examples. But as I said, from routing perspective, it may make
> > > sense but not signaling. What you've pointed out is the routing 
>document...
> > >  From signaling perspective, if I removed the switching capability
> > > field, there is nothing lost...do you agree?
> > >
> > >
> > > JD:  No.  I will try again. What you have to demonstrate is that for 
>all
> > > possible combinations of switching capabilities supported on a link, 
>an
> > > intermediate node can deduce, from other fields in the Path message, 
>what
> > > switching capability is desired.
> > >
> >
> > <z>Wow...ok...so I have to list all the different combinations of
> > different switching capabilities on each side and the possible
> > connections and then demonstrate that what switching capability is
> > desired can be deduced...hmmm...can't I just say that whatever the
> > encoding type says and the sender_tspec says is what the switching type
> > used (I'm lazy, it takes too long to run through all the 
>combinations)</z>
> >
> > >
> > > And if I removed the switching capability field, then it opens the 
>door
> > > for the possibility where somewhere within my network I might change 
>the
> > > switching type in order to satisfy a request (because the switching 
>type
> > > requested is non-existent or exhausted).</z>
> > >
> > >
> > > JD: Please give an example of where substituting one value of 
>switching
> > > capability for another in the middle of an LSP makes sense.
> > >
> >
> > <z>Well, for example, you have a SONET network that can provide STS-48c,
> > and it goes through an all-optical network that can provide OCh1 (2.5G
> > service). In the SONET network it switches the STS-48c layer, while in
> > OTN network it switches the OCh layer. This is very similar to E1/VC-12
> > connection, where one part of network may work PDH-based and switching
> > E1 while another part may be SDH-based and switching VC-12, but the
> > connection or service is essentially the same. They're not really
> > client-server layers but similar layers from different 
>technologies...</z>
> >
> > > <z>I think it does make sense. I think you have to assume that within
> > > the switched transport network there will be many kinds of interfaces
> > > connecting to the transport network. If you can't offer this 
>capability,
> > > then essentially what you've done is segment the transport network 
>into
> > > sub-networks based on what interfaces they have and only the like-type
> > > interfaces can connect to each other. If you look at the IP world, you
> > > might have a switch with 100 Mbps and another with 10 Mbps connected
> > > together and talking to each other without a problem. This is 
>capability
> > > that is also needed, where one end could be 1 Gbps Ethernet and 
>another
> > > end is 10 Gbps Ethernet. But one end can also be an OC-48 SONET (no
> > > reason to restrict this). What really matters is that the service is
> > > delivered. Granted there will be some inefficiencies in this, but 
>that's
> > > really a policy decision whether users are willing to accept this type
> > > of connection.</z>
> > >
> > >
> > > JD:  What you're describing here is PSC LSPs and they work just fine.  
>What
> > > you were describing in your previous example was an LSP, one end of 
>which
> > > was
> > > PSC and the other end of which was TDM.  And that doesn't make sense.
> > >
> >
> > <z>Maybe this is one where we need to ask individuals with operational
> > experience and have some experience with service provisioning whether
> > having one end with Ethernet and another end with OC-48 sounds like a
> > configuration that makes sense?
> >
> > Again, the point here is that if this doesn't make sense, then
> > essentially what you have is multiple switched networks, each serving
> > one particular type of customer interface, i.e., a switched network for
> > 1 Gb Ethernet, a switched network for OC-48, etc.
> >
> > Is this one of those "violent agreements" where we're concentrating on
> > two different levels but saying the same thing?</z>
><< dimitri.papadimitriou.vcf >>


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