RFC 8690
Clarification of Segment ID Sub-TLV Length for RFC 8287
Part 1 of 2 💖 the title block tea first, then the good stuff
RFC 8690: Clarification of Segment ID Sub-TLV Length for RFC 8287 🎀
Okay bestie, so this doc is from the IETF (Internet Engineering Task Force) and it's RFC 8690 📜. It was written by N. Nainar, C. Pignataro, and F. Iqbal from Cisco Systems, Inc., and A. Vainshtein from ECI Telecom. F. Iqbal is writing as an Individual, so no company on that one. 💅
The category is Standards Track 🔥, the ISSN is 2070-1721, and it was published in December 2019 ✨. Most importantly, it updates RFC 8287 🦋. It doesn't obsolete anything, so RFC 8287 is still the main character, we're just adding clarity to it. 🫶
Abstract ✨
Okay so [RFC8287] is the one that extends MPLS LSP Ping and Traceroute so they can handle Segment Routing IGP-Prefix and IGP-Adjacency Segment Identifiers (SIDs) with the MPLS data plane 🌸. It brings in three Target Forwarding Equivalence Class (FEC) Stack sub-TLVs. RFC 8287 explains the format and procedure for handling those sub-TLVs, but it doesn't really spell out how the length of the Segment ID sub-TLVs should be worked out for the Length field of each sub-TLV 🙈. That confusion has caused interoperability issues 💀.
This document updates RFC 8287 by clarifying the length of each of the Segment ID sub-TLVs defined there 🍓.
Status of This Memo
This is an Internet Standards Track document 🌈.
It's a product of the Internet Engineering Task Force (IETF), so it represents the consensus of the IETF community 👑. It went through public review and was approved for publication by the Internet Engineering Steering Group (IESG) ✨. If you want more info on Internet Standards, check out Section 2 of RFC 7841 🧚.
For the current status, any errata, and how to give feedback, go to https://www.rfc-editor.org/info/rfc8690 💜.
Copyright Notice
Copyright (c) 2019 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) as they were in effect on the date of publication 📜. Please actually read these, bestie, because they describe your rights and restrictions for this document 🙈. Code Components pulled out of this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions, and they come without warranty, as described in the Simplified BSD License ⚠️.
Table of Contents 🗂️
1. Introduction
2. Terminology
3. Requirements Notation
4. Length Field Clarification for Segment ID Sub-TLVs
4.1. IPv4 IGP-Prefix Segment ID Sub-TLV
4.2. IPv6 IGP-Prefix Segment ID Sub-TLV
4.3. IGP-Adjacency Segment ID Sub-TLV
5. IANA Considerations
6. Security Considerations
7. Normative References
Acknowledgements
Contributors
Authors' Addresses1. Introduction 🌷
[RFC8287] extends MPLS LSP Ping and Traceroute for Segment Routing IGP-Prefix and IGP-Adjacency Segment Identifiers (SIDs) with the MPLS data plane 💖. It proposes three Target FEC Stack sub-TLVs 🎀. RFC 8287 defines the format and procedure to handle those sub-TLVs, but it doesn't sufficiently clarify how the length of the Segment ID sub-TLVs should be computed for the Length field of the sub-TLVs. This may result in interoperability issues 😭.
So this document updates [RFC8287] by clarifying the length of each Segment ID sub-TLV defined in [RFC8287] 🫶.
2. Terminology 📖
This document uses the terminology from [RFC8402], [RFC8029], and [RFC8287]. You're expected to already be familiar with those terms the way those documents use them 🧚.
3. Requirements Notation 🔑
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 🔥.
4. Length Field Clarification for Segment ID Sub-TLVs 🎀
Section 5 of [RFC8287] defines three different Segment ID sub-TLVs that can be included in the Target FEC Stack TLV defined in [RFC8029]. The length of each sub-TLV MUST be calculated as defined in this section 💅.
The TLV representations defined in Sections 5.1, 5.2, and 5.3 of [RFC8287] are updated to clarify the length calculations, as shown in Sections 4.1, 4.2, and 4.3, respectively 🦋. The updated TLV representations contain explicitly defined lengths 🌈.
4.1. IPv4 IGP-Prefix Segment ID Sub-TLV 💜
The sub-TLV length for the IPv4 IGP-Prefix Segment ID MUST be set to 8, as shown in the TLV format below ✨:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Type = 34 (IPv4 IGP-Prefix SID)| Length = 8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 prefix |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Prefix Length | Protocol | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+4.2. IPv6 IGP-Prefix Segment ID Sub-TLV 🌸
The sub-TLV length for the IPv6 IGP-Prefix Segment ID MUST be set to 20, as shown in the TLV format below 🧚:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Type = 35 (IPv6 IGP-Prefix SID)| Length = 20 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| |
| IPv6 Prefix |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Prefix Length | Protocol | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+4.3. IGP-Adjacency Segment ID Sub-TLV 🦋
Okay, this one is the trickiest 🙈. The sub-TLV length for the IGP-Adjacency Segment ID varies depending on the Adjacency Type and Protocol. In any of the allowed combinations of Adjacency Type and Protocol, the sub-TLV length MUST be calculated by including 2 octets of the Reserved field 🔥. Table 1 lists the length for the different combinations of Adj. Type and Protocol 💅.
+----------+-------------------------------------+
| Protocol | Length for Adj. Type |
| +----------+------+------+------------+
| | Parallel | IPv4 | IPv6 | Unnumbered |
+==========+==========+======+======+============+
| OSPF | 20 | 20 | 44 | 20 |
+----------+----------+------+------+------------+
| ISIS | 24 | 24 | 48 | 24 |
+----------+----------+------+------+------------+
| Any | 20 | 20 | 44 | 20 |
+----------+----------+------+------+------------+
Table 1: IGP-Adjacency SID Length ComputationFor example, when the Adj. Type is set to Parallel Adjacency and the Protocol is set to 0, the sub-TLV will look like this 🍓:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Type = 36 (IGP-Adjacency SID) | Length = 20 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Adj. Type = 1 | Protocol = 0 | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local Interface ID (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote Interface ID (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertising Node Identifier (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Receiving Node Identifier (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+Authors' Addresses 💌
okay bestie, last stop! here's where you can find the brilliant minds behind this doc 🫶
Nagendra Kumar Nainar 💜
Nagendra Kumar Nainar
Cisco Systems, Inc.
7200-12 Kit Creek Road
Research Triangle Park, NC 27709
United States of America
Email: naikumar@cisco.comCarlos Pignataro 🦋
Carlos Pignataro
Cisco Systems, Inc.
7200-11 Kit Creek Road
Research Triangle Park, NC 27709
United States of America
Email: cpignata@cisco.comFaisal Iqbal 🌸
Faisal Iqbal
Individual
Canada
Email: faisal.ietf@gmail.comAlexander Vainshtein ✨
Alexander Vainshtein
ECI Telecom
Israel
Email: vainshtein.alex@gmail.com📦 where this page comes from
- ietf: rfc8690 2019-12
- 💖 girlified by claude-haiku-5-5 on : a language model's rewrite of the original, under its terms