Re: [Teas] Te-topology and te data models questions

[Igor Bryskin <[e-mail]>]

 Hi Anton,

Thank you for the interest, review and questions Please, find in line.

Cheers,
Igor

    On Tuesday, October 22, 2019, 6:55:07 AM EDT, Anton Snitser <[e-mail]> wrote:  
 
  
Hello everyone,
 
  
 
Name is Anton, am a systems engineer from Sedona systems.
 
  
 
I have been reviewing the ietf-te.yang and ietf-te-topology.yang data models as well as their various augmentations and I had a few questions regarding how they are meant to be used when representing native network state and managed objects. Not sure if this Is the correct email group. Saw it in the drafts, decided to try.
 
  
    
   - What is the usage scope of transitional links? – it is meant to represent an inter-layer transition between different layers, but as peC the diagrams In the drafts I have only seen it being used in the same    

   -    

   -  IB>>Correct. Transitional link is a special link modeling an inter-layer relationship. Specifically, it connects a client layer LTP with a server layer TTP and may articulate a cost of adding additional links in the server layer to satisfy  path computation request in the client layer. Transitional link is only useful  in multi-layer computations. Alternative to transitional link is inter-layer lock.
   -    

   - Can transitional links be used inter layer to describe a cross-layer-link in a technology disaggregated environment? E.g., a router port <-> OTN client-port and subsequently the OTN to WDM cross-layer-links. consider each layer node as a separate physical node e.g., physical router, OTN switch and WDM node    

   -    

   - IB>> No, in your case the link from the router is a regular TE link and belongs to OTN, while transitional link is inside WDM device (where OTN to WDM adaptation actually occurs)   




 
  
 
Consider the following.
 

 Is it possible to describe a link where a source node:tp from the IP topology and a destination node:tp from the OTN/WDM topology create a transitional link. IB>> No, see above
 
  
    
   - Are there strict guidelines on how a TTP should be modeled? In the drafts it is mentioned a TTP can be an OCH transponder in the WDM topology. What about OTN and IP? What are the rules used to designate a physical/logical entity as a TTP or non-TTP entity?
   
   - Can an IP loopback on routers be considered a TTP? If not then what is a TTP in the IP layer?
   - What is a TTP in the OTN layer? Is it the framing module in the switch?
   
   - IB>> TTP, generally speaking,  represents a device inside a TE node where a particular client-server layer adaptation (different in some way from other client-layer adaptations in the same node) occurs.  Normally, IP layer TE nodes do not have/requite TTPs, unless it is an abstract node, in which case the TTP may indicate, for example,  the physical router where TE tunnel (described on abstract IP topology) terminates.    


  
    
   - The figures are missing from thetutorial draft. Is there a reference implementation document somewhere?    

 
  
    
   - I have more questions, but I wanted to start slow.. to see there I get an ACK response.
 
  
 
  
 
Thank you very much to whoever answers!
 
Brgrds
 
  
 

 
Anton Snizar | Systems Engineer

 
m: [phone]
 
e: [e-mail]
 
w: sedonasys.com
 
l: Linkedin
 
  
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