[Nsi-wg] NSI Path/Connection manipulation and decomposition semantics (short)

[Jerry Sobieski]

Hi Guilherme-

These examples don't speak to path selection constraints or any 
particular transport framing constraints.  This being said, I did assume 
that these STPs were compatible (as I wasn't trying to show transport 
layer function - just path object manipulation)   Further, I did not 
state whether  A>B meant that these were adjacent STPs in the topology - 
in my mind I assumed the A>B was assumed to be a loose hop.  I tried to 
just state some very simple nomenclature for describing path objects, 
and then make some simple statement about how they can be decomposed and 
re-combined.   A and M (for example) could be very differnet types of 
STPs, how or why they ended up in the path object wasn't germaine to 
this issue (IMO).

Given A>M, and N>Z, concatenating these two paths requires that M and N 
be examined.  If they are not equivalent topologically then the 
concatenation A>M>N>Z would imply/require some sort of path construction 
from M to N was necessary.  That path selection would [magically] 
address your concerns. (:-)   If they did turn out to be equivalent 
points, then the adaptation you ask about would presumably have been 
done between A and M or between N and Z.  Again, I wasn't trying to 
define how the path was selected, just how to manipulate it after the 
fact..  

Hope this helps (and thanks for reading it close enough to ask the 
questions - valid questions.) 
Regard
Jerry

Guilherme Fernandes wrote:
> Wouldn't it be possible for A>M to end be terminated at a different layer
> (L1) than the entry layer L2 for M>Z, and M not have the adaptation
> function
> L1->L2?
>
> In that case, the first implication does not hold, and would need
> Concatenation to be conditional.
>
> (Sorry if this doesn't follow NSI terminology)
>
> Guilherme
>
>   
>> Can I propose some connection decomposition and manipulation
>> semantics?   Try these:
>>
>> Definition:  A Service Termination/Transit Point  "STP" identifies a
>> location in the topology.   STPs primarily denote a lowest level
>> component of the topology where a service instance may begin, end, or
>> transit.   An STP may also identify a higher level topological construct
>> where a service instance may begin, end, or transit.   In the case of a
>> higher level construct, the service instance may touch any sub-component
>> to meet the termination or transit constraint.
>>
>> Definition:  Given STPs A and Z,  "A>Z" denotes a unidirectional Path
>> beginning at A and ending at Z;
>>
>> Rule 1:  Equivalence:    Given two STPs J and K,    If J==K ("J is
>> topologically equivalent to K"), then K==J, and both identify the same
>> location (object) in the topology.
>>
>> Rule 2: Concatenation:    Given STPs A,M,N,,Z, a Connection C1:=(A>M),
>> and a Connection C2:=(N>Z),
>>                     then   C1:C2 == (A>M):(N>Z) == (A>M>N>Z)       "C1
>> concatenated with C2 is equivalent to ..."
>>
>> Implications:
>>
>> -  If Connection A>M exists, and a Connection M>Z exists,  Then by
>> concatenation a Connection A>M>Z exists, and by implication A>Z exists.
>> -  Given J==K, then A>J == A>K;   and  (J>K)==J==K;
>> - Given STPs A, M, N, and Z,   If M==N, then (A>M):(N>Z) == A>M>N>Z ==
>> A>M>Z ==A>N>Z;
>>
>> Thoughts?
>> Jerry
>>
>>
>>
>> _______________________________________________
>> nsi-wg mailing list
>> nsi-wg at ogf.org
>> http://www.ogf.org/mailman/listinfo/nsi-wg
>>
>>     
>
>
>   
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://www.ogf.org/pipermail/nsi-wg/attachments/20100224/48a97c32/attachment.html