[lisp] Re: Review draft-ietf-lisp-te

[Padma Pillay-Esnault <[e-mail]>]

Thanks for your responses - see below

> On Jun 13, 2024, at 2:34 PM, Dino Farinacci <[e-mail]> wrote:
> 
> 
>>>>> 
>>>>> What is the precedence between the L bit and the S bit? Must they both be set to 1? What is the procedure of L
>>>> 
>>>> There isn't one, they are treated independently.
>>> 
>>> PPE
>>> How is the decision to skip a node taken?
>>> Let’s take this example  ( n (L=1, S=0, P=0), n+1 (L=1,S=1),…., etr)
>>> 
>>> If we check S=0 first then the decision is just to Skip that hop “n” then will not do a look up and go to next
> 
> Right, if the encapsulator thinks the RLOC for n is down, it could go to n+1.

Here is where i wonder whether strict would have been best to drop the packet and not go to n+1 per the example for SFC where there are mandatory services.

I think it might be worthwhile to document this behavior so as there are no surprises.
Thoughts?

Padma
> 
>>> reencap hop n+1 . Get a valid RLOC by performing look up for next hops in the list. (Result “n”is skipped).
> 
> Then it looks up EID n+1 to get the RLOC for it.
> 
>>> If we check first L = 1 and then there is a valid RLOC we use the reencap hop n regardless of whether it was skippable
>>> (Result here “n” is not skipped)
> 
> Right.
> 
>>> If S =1 then we may do a look up (Result “n” not skipped)
>>> See more below on S=1 and unreachability.
>>> 
>>> I was wondering which is the actual behavior. As the text on S=0 is a “can skip” it seems implementation specific and still be ok.  Should some guidance on use of L and S bit be included for clarity?  FWIW I have no strong opinion on this.
> 
> You have to lookup the EID when L=1, you can't tell the EID is up or not, you have to probe its RLOC. When you do that, you can decide not to use it and move to the second one. If the S=1 is set for this EID, then you must stop using the ELP.
> 
> Dino
>