[Nsi-wg] [Nml-wg] Conversation about ITU concepts with Ciena folks
Jeroen van der Ham
vdham at uva.nl
Tue Sep 8 14:01:44 CDT 2009
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.
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