[Nml-wg] [Nsi-wg] Conversation about ITU concepts with Ciena folks

[Jeroen van der Ham]

Jerry Sobieski wrote:
> Hmmm...I guess I am confused.   I thought transitional links *were* 
> adaptation components of the topology (and vice versa).   A selected 
> path that transited/transitioned an adaptation componet had to configure 
> that adaptation at provisioning time;

As far as I understand it Transitional Links were introduced to create
an abstraction of the adaptation and links underneath it.

> I think though, whatever you 
> call it or where ever it is in the topology, transitional links / 
> adaptation components function differently in two different situations:  
> a) Encapsulation, and b) stitching.   The former, is a "vertical" 
> transition where the upper layer protocol is tunneled in its entirety 
> through the lower layer protocol (ala IP/Ethernet, or Ethernet/sonet 
> (via GFP adaptation) ) and must have a matching decapsulation function 
> at the egress, and the latter is more "horizontal" transition where the 
> current transport protocol is stripped in its entirety leaving only the 
> user data payload which is then placed in the next transport protocol 
> for forwarding (the stitching adaptation does not require a matching 
> function at its egress point - only whatever it needs for the next 
> stage).   Does this jive with the discussion and other papers on these 
> concepts?

If I understand correctly the distinction you make has already been
proposed by Guy earlier: forwarding (your "vertical") and switching
("horizontal").

Jeroen.