Re: [Detnet-dp-dt] New update of the draft available

I think there’s still a bit of confusion what constitutes T and L labels. Say I have a topology below:

          DA-T-PE     P       P       Php      DA-S-PE       Php    DA-T-PE
PW label     200      200     200     200    200 swp 300     300    300
L label
T label          123  swp 124 swp 125 pop                131 pop

Why would I need L-labels in the above case?

          DA-T-PE     P       P       Php      DA-S-PE       Php    DA-T-PE
PW label     200      200     200     200         200        200    200
L label      300      300     300     300    300 swp 400     400    400
T label          123  swp 124 swp 125 pop                131 pop

Here I could use the L-label to bypass DA-S-PE.

Correct me if this is not correct assumption..

- Jouni

> On Mar 10, 2017, at 6:38 PM, Loa Andersson <loa@pi.nu> wrote:
> 
> Jouni,
> 
> Mostly looks very good, the thing I don't understand is why you still say that the L-label is optional, it really isn't.
> 
> - we need it to deliver the d-pw label unchanged
> - since we can't guarantee that the "P" nodes are not able to do
>  DetNet NSP, we can't set up the d-pw label with signaling that
>  exposes the "request for DetNet NSP/FRER" to P nodes.
> - needed for protection
> - the end-to-end tunnel must be the innermost tunnel, carrying
>  pw label
> 
> There is one case, if two DA-*-PEs are immediately adjacent, there the
> L-lable will be an implicit NULL label and not appear in the stack, but
> for the control plane it is there.
> 
> /Loa
> 
> On 2017-03-11 07:25, Jouni Korhonen wrote:
>> * Added Loa’s comments on the L-label.
>> * Added Janos’ comments.
>> * Added extended forwarder text.
>> * Added (speculative text.. can be removed) D bit to flow-id word so that we can check in a ring case the direction of the flow (note this does not double history buffer space as claimed.. did not bother to fix that)
>> * reworked the PW encapsulation pictures.
>> * Added more content to DA-*-PE descriptions.
>> 
>> - Jouni
>> 
>> 
> 
> -- 
> 
> 
> Loa Andersson                        email: loa@mail01.huawei.com
> Senior MPLS Expert                          loa@pi.nu
> Huawei Technologies (consultant)     phone: +46 739 81 21 64
> 
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