[Nsi-wg] Bidirectional path finding

[Henrik Thostrup Jensen]

Hi John

On Wed, 25 Sep 2013, John MacAuley wrote:

> In a bidirectional service request (directionality == Bidirectional) I 
> specify a pair of bidirectional STP I would like connected.  Is there an 
> assumption that I can only satisfy this service request by 
> interconnecting bidirectional STP in the topology, or can the 
> aggregating NSA segment this into component unidirectional ports and 
> route using independent unidirectional STP (with any symmetricPath 
> restrictions)?

I'd say splitting it up into undirectional circuits should be okay (I 
guess most path finders are not going to bother with this, but I am 
putting anything on the line).

> Using bidirectional topology greatly simplifies path 
> finding, however, the symmetricPath parameter only applies to the 
> intra-domain connections done by the uPA.

AFAIK, symmetric should be for the entire path. However there is currently 
no way to really expose that two undidirectional paths are symmetric in 
the topology. Hence, it is impossibly to guarantee a multi-domain path 
with the symmetric constraint AFAICT.

Only in single-domain requests, where the NSA has knowledge about the 
underlying structure is it possibly to guarantee the symmetric constraint.

Interesting...


     Best regards, Henrik

  Henrik Thostrup Jensen <htj at nordu.net>
  Software Developer, NORDUnet