MPLS Working Group L. Andersson Internet-Draft Bronze Dragon Consulting Intended status: Informational May 10, 2021 Expires: November 11, 2021 MPLS Open Design Team Questions draft-andersson-mpls-open-dt-questions-01 Abstract This document is a living document, meaning that during the life timme of the MPLS Open Design Team we will put additonal questions/ issues into the document. When we find an answer amd a way to document the issu it will be removed from this document. Ideally when the Design Team is closed this document will be empty, or maybe we just add a pointer to where the answer to quesstion is documented. Thus this document will never go on to become an RFCc. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on November 11, 2021. Copyright Notice Copyright (c) 2021 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must Andersson Expires November 11, 2021 [Page 1] Internet-Draft Open DT Questions May 2021 include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Requirement Language . . . . . . . . . . . . . . . . . . 2 2. Open DT Question List . . . . . . . . . . . . . . . . . . . . 3 2.1. Below the BoS . . . . . . . . . . . . . . . . . . . . . . 3 2.1.1. Limitations to the ability of LSR's to scan the Label Stack . . . . . . . . . . . . . . . . . . . . . . . . 3 2.1.2. Does flooding om maximum scanning depth of an LSR scale? . . . . . . . . . . . . . . . . . . . . . . . 3 2.1.3. Placeholder, due to duplicate to another section . . 4 2.1.4. First Nibble . . . . . . . . . . . . . . . . . . . . 4 2.1.5. More then on ACH after the BoS . . . . . . . . . . . 4 2.1.6. More then one indicator? . . . . . . . . . . . . . . 4 2.1.7. Multiple types of Indicators in the same stack . . . 4 2.1.8. Comfortable Readable Label Depth . . . . . . . . . . 4 2.2. Above the BoS . . . . . . . . . . . . . . . . . . . . . . 5 2.2.1. Resuse the ELI . . . . . . . . . . . . . . . . . . . 5 2.2.2. Using any bSPL . . . . . . . . . . . . . . . . . . . 5 2.2.3. Use of Extended SPLs . . . . . . . . . . . . . . . . 5 2.2.4. Generalized Action Indicator . . . . . . . . . . . . 5 3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6 5. Normative References . . . . . . . . . . . . . . . . . . . . 6 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6 1. Introduction "Living Documents" are not commonly used in the IETF, but we have considered it to be a good way of documenting the state of the issues worked on by the design team. 1.1. Requirement Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. For a document that is not intended to become and RFC on the Standards Track it might seem moot to have the requirement language included, however it might be that a question or an answer to one of Andersson Expires November 11, 2021 [Page 2] Internet-Draft Open DT Questions May 2021 the questions might use the BCP 14 language, so to avoid ambiguity we left it in 2. Open DT Question List 2.1. Below the BoS As we start working on this document we just add new questions as we define them. It is possible that later we will try to find a grouping af questions based more on technical commonalities. 2.1.1. Limitations to the ability of LSR's to scan the Label Stack Several LSRs have limitations how deep it is possible to scan the label stack looking for certain information. If the info that are being looked for is below this depth, is it possible to use these LSRs for manadatoy actions? The inormation needed for the mandatory action will never be found. 2.1.2. Does flooding om maximum scanning depth of an LSR scale? A remedy for the issues in Section 2.1.1 has been suggested, the maximum scanning depth for each LSR in the network should be flooded to all othr LSRs and used as a constraint when setting up LSPs. Would that scasle satisfactorily. Tentative answer: Stewart: It is one additional capability field (no more than a byte) to flood and I find it hard to imagine that it would not scale. The IGPs will need to be slightly updated, RFC 8491 will be a good starting point. Loa: Flooding will be done by an IGP, which is a small update to the IGP. For networks that is controlled by a network management system (centralized controller), the NMS will both knew the scanning limitations and establish the LSP. Conclusion: Unless we see any further comments, this question is closed. Andersson Expires November 11, 2021 [Page 3] Internet-Draft Open DT Questions May 2021 2.1.3. Placeholder, due to duplicate to another section Duplicate entry, in order to keep section number the duplicate has ben replaced by a placeholder. 2.1.4. First Nibble We have indications that when we started to snoop the first nibble after the LSE that has the BoS set to find out if the packet carried IP (v4 or v6), there was also an agreement that "we" would never put anything but 0b0000 or 0b0001 in that first nibble. It is off couurse intresting to try to understand the definition of "we" but since the aggreement were between the Internet Area and the PWE3 working group, it is likely that it will be considered binding for the Routing Area. Stewart: Can you try to find out more about this and where we stand today. 2.1.5. More then on ACH after the BoS Is it possible to have more than one ACH after the BoS. If currently not possible do we want to add it? How are the ACH's separated and related to the indicator in the label stack? 2.1.6. More then one indicator? What happens when you find the first indicator? If an LSR is scanning "the entire stack", what happens when the first indicator is found? Is the scanning aborted. If an GAL is below an FAI in the stack will it be found? 2.1.7. Multiple types of Indicators in the same stack Is it possible to have multiple types of indicators in the same label stack, e.g. FAI and GAL? 2.1.8. Comfortable Readable Label Depth What is the Readable Label Depth (RLD) that we are comforable with. Andersson Expires November 11, 2021 [Page 4] Internet-Draft Open DT Questions May 2021 This is a question that was voiced at a DT meeting, but there were not real discussion. Here we take the question to mean "What is the minimum RLD that we can count on by any LSR when we design functions that need to detect action indicators in the label stack?" 2.2. Above the BoS - 2.2.1. Resuse the ELI When using bSPLs for multipurpose - "the useless bit in the bSPL" - it was sometimes talked about reusing the ELI (unless this was misunderstood). Is this still on the agenda? 2.2.2. Using any bSPL Is it possible to use the "useless bits" in any bSPL to indicate actions? If we do will the corresponding bits. e.g. MSB in the TTL, mean the same thing regardless of in which bSPL it is found? 2.2.3. Use of Extended SPLs Is it possible to use the "useless bits" in an eSPL/cSPL? It would give use more bits to play with. If the answer to the question in Section 2.2.2 is yes the useless bits in the XL would be interpreted as in any other indicator, but you have at least 11 new bits in the eSPL. Maybe allocate an extended FAI-2 from the extended range? 2.2.4. Generalized Action Indicator Could we generalize the FAI (+ FAI-2 ?) to be general mechanism for indicating presence of "stuff" after the BoS? 3. IANA Considerations This document does not make any allocations of code points from IANA registries. Andersson Expires November 11, 2021 [Page 5] Internet-Draft Open DT Questions May 2021 4. Acknowledgements - - 5. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . Author's Address Loa Andersson Bronze Dragon Consulting Email: loa@pi.nu Andersson Expires November 11, 2021 [Page 6]