Re: [mpls] Poll on MPLS forwarder characteristics

[Loa Andersson <[e-mail]>]

Working Groups, MPLS Open DT,

This poll is closed, and Adrian has promised to post the results.

/Loa
for the MNA co-chairs

On 2022-09-21 09:49, Loa Andersson wrote:
> Working Group(s),
> 
> In the discussions relating to adding MPLS Network Actions and Ancillary 
> Data, several questions have arisen that would be best resolved by 
> understanding how existing implementations function. The answers to 
> these questions will not necessarily enable us to make firm decisions in 
> one direction (because proof of a negative is hard), but might help us 
> avoid proposals that would break implementations.
> 
> We have five questions below. Please send your responses to Adrian 
> ([e-mail]) starting the email subject with “MPLS Forwarder 
> Poll”. Adrian will anonymise them and make the batch of anonymised 
> responses available to the MPLS Working Group. Using this approach 
> ensures the confidentially of the data and nothing will be explicitly or 
> implicitly leaked regarding the equipment behaviour of a specific 
> vendor. If different implementations have different behaviours please 
> indicate this.
> 
> 
> 1. Does your implementation look at anything more than the top label in 
> the label stack? If so, does it
> 
> a) "scan ahead" examining the labels,
> b) Simply use the Label Stack Entries as input to a hash,
> c) Just search for the Bottom of Stack?
> d) Something else
> 
> 2. In the case where your implementation looks at label values below Top 
> of Stack,
> 
> a) Does the scan-ahead recognise SPLs.
> b) If so, what does it do if the label value is an SPL (bSPL or eSPL) 
> that it does not recognise?
> 
> (Note that this question applies to RFC 3031/3032 implementations as 
> well as RFC 6790/8662 implementations.
> 
> 3. What value does your implementation set as
>      a) The ELI TC field
>      b) The ELI TTL
>      c) The EL TC field
>      d) The EL TTL
> 
> In each case what happens if the received bits in those fields are not 
> as expected?
> 
> 4.
>     a) How does your Penultimate Hop Pop implementation (RFC 
> 3031/3032/3270/3443) process the TTL and TC (as EXP) from the popped 
> Label Stack Entry?
>     b) In particular, does it copy either field into the exposed 
> top-of-stack Label Stack Entry (in the case where the popped label was 
> not bottom of    stack)?
> 
> 5. Does your Penultimate Hop Pop implementation examine the exposed top-
> of-stack label to see whether it is a bSPL? If so, what does it do?
> 
> /Loa
> For the MNA co-chairs

-- 
Loa Andersson                        email: [e-mail]
Senior MPLS Expert                          [e-mail]
Bronze Dragon Consulting             phone: [phone]