Re: [mpls] Concerns about ISD

[Stewart Bryant <[e-mail]>]

> On 16 Apr 2022, at 14:38, Robert Raszuk <[e-mail]> wrote:
> 
> Hi Tianran,
> 
> I do not think DETNET(including bounded delay) need neither. There is already specifications for MPLS.
> 
> We are not going to review them all here.
> 
> 
> That is a very interesting and important point. I just looked at RFC8964 and surprise ... no need to change MPLS architecture. Just use a service label concept and carry service info outside of the data plane. 
> 
> What I called Forwarding Behaviour ID they call service label (analogy to other types of service labels already carried in MPLS). The difference between RFC8964 and FBI approach seems to be about types of services (aka actions) to execute on the packets. Also FBI concept works with domain wide labels while service labels are pretty much local to a given node. 
> 
> So a bit curious what the above architectures are missing which would really justify to define, develop and deploy a new MPLS data plane ? 
> 
> Kind regards,
> Robert
> 
> PS. For those who are claiming that use a post stack data PSD should be the only option let me observe that if this solution is supposed to work with SR-MPLS the label stack of pure transport may be pretty large. So number of nodes may not be capable to fetch PSD (we invented EL just because transit LSRs were not even able to read IP header). That to me is a practical blocker for this approach if MNA will continue. 
> 

Detnet is really an overlay system.

The delivery label takes the packet to the next hop in the Detnet layer. This is popped and the service label exposed. The service label is then processed. Then if the packet is to continue a new service label is pushed followed by a new delivery label.

In a PHPed network where every node is a service label the service label is always ToS. However the operation in not really swap as in MSPW, the service label and the CW are examined and processed.

Note that Detnet does not support many of the features being asked for in NA/MIAD.

- Stewart