[mpls] Poll on MPLS forwarder characteristics
Loa Andersson <loa@pi.nu> Wed, 21 September 2022 07:49 UTC
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Subject: [mpls] Poll on MPLS forwarder characteristics
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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 (adrian@olddog.co.uk) 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: loa@pi.nu Senior MPLS Expert loa.pi.nu@gmail.com Bronze Dragon Consulting phone: +46 739 81 21 64
- [mpls] Poll on MPLS forwarder characteristics Loa Andersson
- Re: [mpls] Poll on MPLS forwarder characteristics Adrian Farrel
- Re: [mpls] Poll on MPLS forwarder characteristics Loa Andersson
- Re: [mpls] Poll on MPLS forwarder characteristics Loa Andersson