Link State Routing Z. Li Internet-Draft Z. Hu Intended status: Standards Track Huawei Technologies Expires: December 31, 2022 K. Talaulikar, Ed. Arrcus Inc P. Psenak Cisco Systems June 29, 2022 OSPFv3 Extensions for SRv6 draft-ietf-lsr-ospfv3-srv6-extensions-04 Abstract The Segment Routing (SR) architecture allows flexible definition of the end-to-end path by encoding it as a sequence of topological elements called "segments". It can be implemented over the MPLS or the IPv6 data plane. This document describes the OSPFv3 extensions required to support Segment Routing over the IPv6 data plane (SRv6). 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 December 31, 2022. Copyright Notice Copyright (c) 2022 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 Li, et al. Expires December 31, 2022 [Page 1] Internet-Draft OSPFv3 Extensions for SRV6 June 2022 to this document. Code Components extracted from this document must 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. Requirements Language . . . . . . . . . . . . . . . . . . 3 2. SRv6 Capabilities TLV . . . . . . . . . . . . . . . . . . . . 3 3. Advertisement of Supported Algorithms . . . . . . . . . . . . 5 4. Advertisement of SRH Operation Limits . . . . . . . . . . . . 5 4.1. Maximum Segments Left MSD Type . . . . . . . . . . . . . 5 4.2. Maximum End Pop MSD Type . . . . . . . . . . . . . . . . 6 4.3. Maximum H.Encaps MSD Type . . . . . . . . . . . . . . . . 6 4.4. Maximum End D MSD Type . . . . . . . . . . . . . . . . . 6 5. SRv6 SIDs and Reachability . . . . . . . . . . . . . . . . . 6 5.1. SRv6 Flexible Algorithm . . . . . . . . . . . . . . . . . 8 6. SRv6 Locator LSA . . . . . . . . . . . . . . . . . . . . . . 8 6.1. SRv6 Locator TLV . . . . . . . . . . . . . . . . . . . . 10 7. Advertisment of SRv6 End SIDs . . . . . . . . . . . . . . . . 12 8. Advertisment of SRv6 SIDs Associated with Adjacencies . . . . 14 8.1. SRv6 End.X SID Sub-TLV . . . . . . . . . . . . . . . . . 14 8.2. SRv6 LAN End.X SID Sub-TLV . . . . . . . . . . . . . . . 16 9. SRv6 SID Structure Sub-TLV . . . . . . . . . . . . . . . . . 18 10. Advertising Endpoint Behaviors . . . . . . . . . . . . . . . 20 11. Security Considerations . . . . . . . . . . . . . . . . . . . 20 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 21 12.1. OSPF Router Information TLVs . . . . . . . . . . . . . . 21 12.2. OSPFv3 LSA Function Codes . . . . . . . . . . . . . . . 21 12.3. OSPFv3 Extended-LSA Sub-TLVs . . . . . . . . . . . . . . 22 12.4. OSPFv3 Locator LSA TLVs . . . . . . . . . . . . . . . . 22 12.5. OSPFv3 Locator LSA Sub-TLVs . . . . . . . . . . . . . . 22 13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 23 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 23 14.1. Normative References . . . . . . . . . . . . . . . . . . 23 14.2. Informative References . . . . . . . . . . . . . . . . . 25 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 25 1. Introduction Segment Routing (SR) architecture [RFC8402] specifies how a node can steer a packet through an ordered list of instructions, called segments. These segments are identified through Segment Identifiers (SIDs). Li, et al. Expires December 31, 2022 [Page 2] Internet-Draft OSPFv3 Extensions for SRV6 June 2022 Segment Routing can be instantiated on the IPv6 data plane through the use of the Segment Routing Header (SRH) defined in [RFC8754]. SRv6 refers to this SR instantiation on the IPv6 dataplane. The network programming paradigm for SRv6 is specified in [RFC8986]. It describes how any behavior can be bound to a SID and how any network program can be expressed as a combination of SIDs. It also describes several well-known behaviors that can be bound to SRv6 SIDs. This document specifies extensions to OSPFv3 in order to support SRv6 as defined in [RFC8986] by signaling the SRv6 capabilities of the node and some of the SRv6 SIDs with their endpoint behaviors that are instantiated on an SRv6 capable router. Familiarity with [RFC8986] is necessary to understand the extensions specified in this document. At a high level, the extensions to OSPFv3 are comprised of the following: 1. SRv6 Capabilities TLV to advertise the SRv6 features and SRH operations supported by the router 2. Several new sub-TLVs are defined to advertise various SRv6 Maximum SID Depths. 3. SRv6 Locator TLV to advertise the SRv6 Locator - a form of summary address for the algorithm specific SIDs instantiated on the router 4. TLVs and Sub-TLVs to advertise the SRv6 SIDs instantiated on the router along with their endpoint behaviors 1.1. Requirements 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. 2. SRv6 Capabilities TLV The SRv6 Capabilities TLV is used by an OSPFv3 router to advertise its support for the SR Segment Endpoint Node [RFC8754] functionality along with its SRv6 related capabilities. This is an optional top level TLV of the OSPFv3 Router Information LSA [RFC7770] which MUST be advertised by an SRv6 enabled router. Li, et al. Expires December 31, 2022 [Page 3] Internet-Draft OSPFv3 Extensions for SRV6 June 2022 This TLV SHOULD be advertised only once in the OSPFv3 Router Information LSA. When multiple SRv6 Capabilities TLVs are received from a given router, the receiver MUST use the first occurrence of the TLV in the OSPFv3 Router Information Opaque LSA. If the SRv6 Capabilities TLV appears in multiple OSPFv3 Router Information Opaque LSAs that have different flooding scopes, the TLV in the OSPFv3 Router Information Opaque LSA with the area-scoped flooding scope MUST be used. If the SRv6 Capabilities TLV appears in multiple OSPFv3 Router Information Opaque LSAs that have the same flooding scope, the TLV in the OSPFv3 Router Information Opaque LSA with the numerically smallest Instance ID MUST be used and subsequent instances of the TLV MUST be ignored. The OSPFv3 Router Information Opaque LSA can be advertised at any of the defined opaque flooding scopes (link, area, or Autonomous System (AS)). For the purpose of SRv6 Capabilities TLV advertisement, area- scoped flooding is REQUIRED. The format of OSPFv3 SRv6 Capabilities TLV is shown 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 | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Flags | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sub-TLVs... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: SRv6 Capabilities TLV Where: o Type: 2 octets field. The value for this type is TBD. o Length: 2 octets field. The total length of the value portion of the TLV including Sub-TLVs in terms of octets. o Reserved: 2 octets field. It MUST be set to 0 on transmission and MUST be ignored on receipt. o Flags: 2 octets field. The flags are defined as follows: Li, et al. Expires December 31, 2022 [Page 4] Internet-Draft OSPFv3 Extensions for SRV6 June 2022 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | |O| | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ where: * O-flag: If set, then the router is capable of supporting the O-bit in the SRH flags, as specified in [RFC9259]. * Other flags are not defined and reserved for future use. They MUST be set to 0 on transmission and MUST be ignored on receipt. The SRv6 Capabilities TLV may contain optional Sub-TLVs. No Sub-TLVs are currently defined. 3. Advertisement of Supported Algorithms SRv6 enabled OSPFv3 router advertises its algorithm support using the SR Algorithm TLV defined in [RFC8665] as described in [RFC8666]. 4. Advertisement of SRH Operation Limits An SRv6 enabled router may have different capabilities and limits when it comes to SRH processing and this needs to be advertised to other routers in the SRv6 domain. [RFC8476] defines the means to advertise node and link specific values for Maximum SID Depth (MSD) types. Node MSDs are advertised using the Node MSD TLV in the OSPFv3 Router Information LSA [RFC7770] while Link MSDs are advertised using the Link MSD Sub-TLV of the Router-Link TLV [RFC8362]. The format of the MSD types for OSPFv3 is defined in [RFC8476]. The MSD types for SRv6 that are defined in section 4 of [I-D.ietf-lsr-isis-srv6-extensions] for IS-IS are also used by OSPFv3. These MSD Types are allocated under the IGP MSD Types registry maintained by IANA that are shared by IS-IS and OSPF. They are described below: 4.1. Maximum Segments Left MSD Type The Maximum Segments Left MSD Type signals the maximum value of the "Segments Left" field of the SRH of a received packet before applying the Endpoint behavior associated with a SID. If no value is advertised, the supported value is assumed to be 0. Li, et al. Expires December 31, 2022 [Page 5] Internet-Draft OSPFv3 Extensions for SRV6 June 2022 4.2. Maximum End Pop MSD Type The Maximum End Pop MSD Type signals the maximum number of SIDs in the SRH to which the router can apply "Penultimate Segment Pop (PSP) of the SRH" or "Ultimate Segment Pop (USP) of the SRH", as defined in [RFC8986] flavors. If the advertised value is zero or no value is advertised, then the router cannot apply PSP or USP flavors. 4.3. Maximum H.Encaps MSD Type The Maximum H.Encaps MSD Type signals the maximum number of SIDs that can be added as part of the "H.Encaps" behavior as defined in [RFC8986]. If the advertised value is zero or no value is advertised then the headend can apply an SR Policy that only contains one segment, without inserting any SRH. A non-zero SRH Max H.encaps MSD indicates that the headend can insert an SRH up to the advertised value. 4.4. Maximum End D MSD Type The Maximum End D MSD Type specifies the maximum number of SIDs present in an SRH when performing decapsulation. These includes, but not limited to, End.DX6, End.DT4, End.DT46, End with USD, End.X with USD as defined in [RFC8986]. If the advertised value is zero or no value is advertised then the router cannot apply any behavior that results in decapsulation and forwarding of the inner packet if the other IPv6 header contains an SRH. 5. SRv6 SIDs and Reachability An SRv6 Segment Identifier (SID) is 128 bits and comprises of Locator, Function and Argument parts as described in [RFC8986]. A node is provisioned with algorithm specific locators for each algorithm supported by that node. Each locator is a covering prefix for all SIDs provisioned on that node which have the matching algorithm. Locators MUST be advertised in the SRv6 Locator TLV (see Section 6.1). Forwarding entries for the locators advertised in the SRv6 Locator TLV MUST be installed in the forwarding plane of receiving SRv6 capable routers when the associated algorithm is supported by the receiving node. Locators can be of different route types similar to existing OSPFv3 route types - Intra-Area, Inter- Area, External, and NSSA. The processing of the prefix advertised in the SRv6 Locator TLV, the calculation of its reachability and the installation in the forwarding plane follows the process defined for the respective route types in base OSPFv3 [RFC5340]. Li, et al. Expires December 31, 2022 [Page 6] Internet-Draft OSPFv3 Extensions for SRV6 June 2022 Locators associated with algorithm 0 and 1 SHOULD be advertised using the respective OSPFv3 Extended LSA types with extended TLVs [RFC8362] based on the OSPFv3 route of the locators so that routers which do not support SRv6 will install a forwarding entry for algorithm 0 and 1 SRv6 traffic. When operating in "sparse-mode" of compatibility [RFC8362] these locators SHOULD be also advertised using the respective base OSPFv3 LSAs [RFC5340]. In cases where a locator advertisement is received via in both in a prefix reachability advertisement (i.e. via base OSPFv3 LSAs and/or Extended Prefix TLVs using OSPFv3 Extended LSAs) and an SRv6 Locator TLV, the prefix reachability advertisement in OSPFv3 MUST be preferred over the advertisement in the SRv6 Locator TLV when installing entries in the forwarding plane. This is to prevent inconsistent forwarding entries between SRv6 capable and SRv6 incapable routers. Such preference of prefix reachability advertisement does not have any impact on the rest of the data advertised in the SRv6 Locator TLV. SRv6 SIDs are advertised as Sub-TLVs in the SRv6 Locator TLV except for SRv6 End.X SIDs/LAN End.X SIDs which are associated with a specific Neighbor/Link and are therefore advertised as Sub-TLVs of E- Router-Link TLV. SRv6 SIDs received from other nodes are not directly routable and MUST NOT be installed in the forwarding plane. Reachability to SRv6 SIDs depends upon the existence of a covering locator. Adherence to the rules defined in this section will assure that SRv6 SIDs associated with a supported algorithm will be forwarded correctly, while SRv6 SIDs associated with an unsupported algorithm will be dropped. NOTE: The drop behavior depends on the absence of a default/summary route covering a given locator. In order for forwarding to work correctly, the locator associated with SRv6 SID advertisements must be the longest match prefix installed in the forwarding plane for those SIDs. In order to ensure correct forwarding, network operators should take steps to make sure that this requirement is not compromised. For example, the following situations should be avoided: o Another locator associated with a different topology/algorithm is the longest match o Another base OSPFv3 prefix advertisement is the longest match Li, et al. Expires December 31, 2022 [Page 7] Internet-Draft OSPFv3 Extensions for SRV6 June 2022 5.1. SRv6 Flexible Algorithm [I-D.ietf-lsr-flex-algo] specifies IGP Flexible Algorithm mechanisms for OSPFv3. Section 14.2 of [I-D.ietf-lsr-flex-algo] explains SRv6 forwarding for Flex-Algorithm and the same apply for supporting SRv6 Flexi-Algorithm using OSPFv3. When the algorithm value that is carried in the SRv6 Locator TLV (refer Section 6.1) represents a Flex-Algorithm, the procedures described in section 14.2 of [I-D.ietf-lsr-flex-algo] are followed for the programming of those specific SRv6 Locators. Locators associated with Flexible Algorithms SHOULD NOT be advertised in the base OSPFv3 prefix reachability advertisements. Advertising the Flexible Algorithm locator as regular prefix reachability advertisements would make the forwarding for it to follow algo 0 path. The procedures like ASBR reachability advertisements and the procedures for inter-area, external and NSSA route advertisement and computation as specified in [I-D.ietf-lsr-flex-algo] for OSPFv3 Flex- Algorithm for SR-MPLS also apply for SRv6. 6. SRv6 Locator LSA The SRv6 Locator LSA has a function code of TBD while the S1/S2 bits are dependent on the desired flooding scope for the LSA. The flooding scope of the SRv6 Locator LSA depends on the scope of the advertised SRv6 Locator and is under the control of the advertising router. The U bit will be set indicating that the LSA should be flooded even if it is not understood. Multiple SRv6 Locator LSAs can be advertised by an OSPFv3 router and they are distinguished by their Link State IDs (which are chosen arbitrarily by the originating router). The format of SRv6 Locator LSA is shown below: Li, et al. Expires December 31, 2022 [Page 8] Internet-Draft OSPFv3 Extensions for SRV6 June 2022 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LS age |1|S12| Function Code | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Link State ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Advertising Router | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LS sequence number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LS checksum | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | +- TLVs -+ | ... | Figure 2: SRv6 Locator LSA The format of the TLVs within the body of the SRv6 Locator LSA is the same as the format used by [RFC3630]. The variable TLV section consists of one or more nested TLV tuples. Nested TLVs are also referred to as Sub-TLVs. The format of each TLV is: 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 | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Value | o o o | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3: SRv6 Locator LSA TLV Format The Length field defines the length of the value portion in octets (thus, a TLV with no value portion would have a length of 0). The TLV is padded to 4-octet alignment; padding is not included in the Length field (so a 3-octet value would have a length of 3, but the total size of the TLV would be 8 octets). Nested TLVs are also 32-bit aligned. For example, a 1-byte value would have the Length field set to 1, and 3 octets of padding would be added to the end of the value portion of the TLV. The padding is composed of zeros. Li, et al. Expires December 31, 2022 [Page 9] Internet-Draft OSPFv3 Extensions for SRV6 June 2022 6.1. SRv6 Locator TLV The SRv6 Locator TLV is a top-level TLV of the SRv6 Locator LSA that is used to advertise an SRv6 Locator, its attributes, and SIDs associated with it. Multiple SRv6 Locator TLVs MAY be advertised in each SRv6 Locator LSA. However, since the S12 bits define the flooding scope, the LSA flooding scope MUST satisfy the application- specific requirements for all the locators included in a single SRv6 Locator LSA. When multiple SRv6 Locator TLVs are received from a given router in an SRv6 Locator LSA for the same Locator, the receiver MUST use the first occurrence of the TLV in the LSA. If the SRv6 Locator TLV for the same Locator appears in multiple SRv6 Locator LSAs that have different flooding scopes, the TLV in the SRv6 Locator LSA with the area-scoped flooding scope MUST be used. If the SRv6 Locator TLV for the same Locator appears in multiple SRv6 Locator LSAs that have the same flooding scope, the TLV in the SRv6 Locator LSA with the numerically smallest Link-State ID MUST be used and subsequent instances of the TLV MUST be ignored. The format of SRv6 Locator TLV is shown 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 | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Route Type | Algorithm | Locator Length| Flags | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Metric | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Locator (128 bits) ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Locator cont ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Locator cont ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Locator cont ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sub-TLVs (variable) | +- -+ | ... | Figure 4: SRv6 Locator TLV Where: Li, et al. Expires December 31, 2022 [Page 10] Internet-Draft OSPFv3 Extensions for SRV6 June 2022 Type: 2 octets field. The value for this type is 1. Length: 2 octets field. The total length of the value portion of the TLV including Sub-TLVs in terms of octets. Route Type: 1 octet field. The type of the locator route. The only supported types are the ones listed below and the SRv6 Locator TLV MUST be ignored on receipt of any other type. 1 - Intra-Area 2 - Inter-Area 3 - AS External Type 1 4 - AS External Type 2 5 - NSSA External Type 1 6 - NSSA External Type 2 Algorithm: 1 octet field. The algorithm associated with the SRv6 Locator. Algorithm values are defined in the IGP Algorithm Type registry. Locator Length: 1 octet field. Carries the length of the Locator prefix as the number of locator bits from the range (1-128). Flags: 1 octet field. The flags are defined as follows: 0 1 2 3 4 5 6 7 +-+-+-+-+-+-+-+-+ |N|A| Reserved | +-+-+-+-+-+-+-+-+ * N-flag: When the locator uniquely identifies a node in the network (i.e., it is provisioned on one and only one node), the N bit MUST be set. Otherwise, this bit MUST be clear. * A-flag: When the Locator is configured as anycast, the A bit SHOULD be set. Otherwise, this bit MUST be clear. If both the N and A bits are set, then the receiving routers MUST ignore the N bit (i.e., consider it as not set). * Other flags are not defined and reserved for future use. They MUST be set to 0 on transmission and MUST be ignored on receipt. Metric: 4 octets field. The metric value associated with the SRv6 Locator. Li, et al. Expires December 31, 2022 [Page 11] Internet-Draft OSPFv3 Extensions for SRV6 June 2022 Locator: 16 octets field. This field encodes the advertised SRv6 Locator. Sub-TLVs: Used to advertise Sub-TLVs that provide additional attributes for the given SRv6 Locator and SRv6 SIDs associated with it. 7. Advertisment of SRv6 End SIDs The SRv6 End SID Sub-TLV is a Sub-TLV of the SRv6 Locator TLV in the SRv6 Locator LSA (defined in Section 6). It is used to advertise the SRv6 SIDs belonging to the node along with their associated endpoint behaviors. SIDs associated with adjacencies are advertised as described in Section 8. Every SRv6 enabled OSPFv3 router SHOULD advertise at least one SRv6 SID associated with an END behavior for its node as specified in [RFC8986]. SRv6 End SIDs inherit the algorithm from the parent locator. The SRv6 End SID MUST be allocated from its associated locator. SRv6 End SIDs that are NOT allocated from the associated locator MUST be ignored. The router MAY advertise multiple instances of the SRv6 End SID Sub- TLV within the SRv6 Locator TLV - one for each of the SRv6 SIDs to be advertised. When multiple SRv6 End SID Sub-TLVs are received in the SRv6 Locator TLV from a given router for the same SRv6 SID value, the receiver MUST use the first occurrence of the Sub-TLV in the SRv6 Locator TLV. The format of SRv6 End SID Sub-TLV is shown below Li, et al. Expires December 31, 2022 [Page 12] Internet-Draft OSPFv3 Extensions for SRV6 June 2022 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 | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Flags | Reserved | Endpoint Behavior | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SID (128 bits) ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SID cont ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SID cont ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SID cont ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sub-TLVs (variable) . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 5: SRv6 End SID Sub-TLV Where: Type: 2 octets field. The value for this type is 1. Length: 2 octets field. The total length of the value portion of the Sub-TLV including its further Sub-TLVs in terms of octets. Reserved: 1 octet field. It MUST be set to 0 on transmission and MUST be ignored on receipt. Flags: 1 octet field. It carries the flags associated with the SID. No flags are currently defined and this field MUST be set to 0 on transmission and MUST be ignored on receipt. Endpoint Behavior: 2 octets field. The endpoint behavior code point for this SRv6 SID as defined in [RFC8986]. Supported behavior values for this sub-TLV are defined in Section 10 of this document. Unsupported or unrecognized behavior values are ignored by the receiver. SID: 16 octets field. This field encodes the advertised SRv6 SID. Sub-TLVs: Used to advertise Sub-TLVs that provide additional attributes for the given SRv6 SID. Li, et al. Expires December 31, 2022 [Page 13] Internet-Draft OSPFv3 Extensions for SRV6 June 2022 8. Advertisment of SRv6 SIDs Associated with Adjacencies The SRv6 endpoint behaviors are defined in [RFC8986] include certain behaviors which are specific to links or adjacencies. The most basic of these which is critical for link state routing protocols like OSPFv3 is the End.X behavior that is an instruction to forward to a specific neighbor on a specific link. These SRv6 SIDs along with others that are defined in [RFC8986] which are specific to links or adjacencies need to be advertised by OSPFv3 so that this information is available to all routers in the area to influence the packet path via these SRv6 SIDs over the specific adjacencies. The advertisement of SRv6 SIDs and their behaviors that are specific to a particular neighbor is done via two different optional Sub-TLVs of the E-Router-Link TLV defined in [RFC8362] as follows: o SRv6 End.X SID Sub-TLV: For OSPFv3 adjacencies over point-to-point or point-to-multipoint links and the adjacency to the Designated Router (DR) over broadcast and non-broadcast-multi-access (NBMA) links. o SRv6 LAN End.X SID Sub-TLV: For OSPFv3 adjacencies on broadcast and NBMA links to the Backup DR and DR-Other neighbors. This Sub- TLV includes the OSPFv3 Router-ID of the neighbor and thus allows for an instance of this Sub-TLV for each neighbor to be explicitly advertised under the E-Router-Link TLV for the same link. Every SRv6 enabled OSPFv3 router SHOULD instantiate at least one unique SRv6 End.X SID corresponding to each of its neighbor. A router MAY instantiate more than one SRv6 End.X SID for for a single neighbor. The same SRv6 End.X SID MAY be advertised for more than one neighbor. Thus multiple instances of the SRv6 End.X SID and SRv6 LAN End.X SID Sub-TLVs MAY be advertised within the E-Router-Link TLV for a single link. All End.X and LAN End.X SIDs MUST be subsumed by the subnet of a Locator with the matching algorithm which is advertised by the same node in an SRv6 Locator TLV. End.X SIDs which do not meet this requirement MUST be ignored. This ensures that the node advertising the End.X or LAN End.X SID is also advertising its corresponding Locator with the algorithm that will be used for computing paths destined to the SID. 8.1. SRv6 End.X SID Sub-TLV The format of the SRv6 End.X SID Sub-TLV is shown below Li, et al. Expires December 31, 2022 [Page 14] Internet-Draft OSPFv3 Extensions for SRV6 June 2022 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 | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Endpoint Behavior | Flags | Reserved1 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Algorithm | Weight | Reserved2 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SID (128 bits) ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SID cont ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SID cont ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SID cont ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sub-TLVs (variable) . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 6: SRv6 End.X SID Sub-TLV Where: Type: 2 octets field. The value for this type is TBD. Length: 2 octets field. The total length of the value portion of the Sub-TLV including its further Sub-TLVs in terms of octets. Endpoint Behavior: 2 octets field. The endpoint behavior code point for this SRv6 SID as defined in [RFC8986]. Supported behavior values for this sub-TLV are defined in Section 10 of this document. Unsupported or unrecognized behavior values are ignored by the receiver. Flags: 1 octet field. The flags are defined as follows: 0 1 2 3 4 5 6 7 +-+-+-+-+-+-+-+-+ |B|S|P| Reserved| +-+-+-+-+-+-+-+-+ * B-Flag: Backup Flag. If set, the SID refers to a path that is eligible for protection. Li, et al. Expires December 31, 2022 [Page 15] Internet-Draft OSPFv3 Extensions for SRV6 June 2022 * S-Flag: Set Flag. When set, the S-Flag indicates that the End.X SID refers to a set of adjacencies (and therefore MAY be assigned to other adjacencies as well). * P-Flag: Persistent Flag: If set, the SID is persistently allocated, i.e., the SID value remains consistent across router restart and session/interface flap. * Other flags are not defined and reserved for future use. They MUST be set to 0 on transmission and MUST be ignored on receipt. Reserved1: 1 octet field. It MUST be set to 0 on transmission and MUST be ignored on receipt. Algorithm: 1 octet field. The algorithm associated with the SRv6 Locator from which the SID is allocated. Algorithm values are defined in the IGP Algorithm Type registry. Weight: 1 octet field. Its value represents the weight of the End.X SID for the purpose of load-balancing. The use of the weight is defined in [RFC8402]. Reserved2: 2 octets field. It MUST be set to 0 on transmission and MUST be ignored on receipt. SID: 16 octeta field. This field encodes the advertised SRv6 SID. Sub-TLVs: Used to advertise Sub-TLVs that provide additional attributes for the given SRv6 End.X SID. 8.2. SRv6 LAN End.X SID Sub-TLV The format of the SRv6 LAN End.X SID Sub-TLV is as shown below: Li, et al. Expires December 31, 2022 [Page 16] Internet-Draft OSPFv3 Extensions for SRV6 June 2022 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 | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Endpoint Behavior | Flags | Reserved1 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Algorithm | Weight | Reserved2 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | OSPFv3 Router-ID of neighbor | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SID (128 bits) ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SID cont ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SID cont ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SID cont ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sub-TLVs (variable) . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 7: SRv6 LAN End.X SID Sub-TLV Where: o Type: 2 octets field. The value for this type is TBD. o Length: 2 octets field. The total length of the value portion of the Sub-TLV including its further Sub-TLVs in terms of octets. o Endpoint Behavior: 2 octets field. The code point for the endpoint behavior for this SRv6 SID as defined in section 9.2 of [RFC8986]. o Flags: 1 octet field. The flags are defined as follows: 0 1 2 3 4 5 6 7 +-+-+-+-+-+-+-+-+ |B|S|P| Reserved| +-+-+-+-+-+-+-+-+ * B-Flag: Backup Flag. If set, the SID refers to a path that is eligible for protection. Li, et al. Expires December 31, 2022 [Page 17] Internet-Draft OSPFv3 Extensions for SRV6 June 2022 * S-Flag: Set Flag. When set, the S-Flag indicates that the End.X SID refers to a set of adjacencies (and therefore MAY be assigned to other adjacencies as well). * P-Flag: Persistent Flag: If set, the SID is persistently allocated, i.e., the SID value remains consistent across router restart and session/interface flap. * Other flags are not defined and reserved for future use. They MUST be set to 0 on transmission and MUST be ignored on receipt. o Reserved1: 1 octet field. It MUST be set to 0 on transmission and MUST be ignored on receipt. o Algorithm: 1 octet field. The algorithm associated with the SRv6 Locator from which the SID is allocated. Algorithm values are defined in the IGP Algorithm Type registry. o Weight: 1 octet field. Its value represents the weight of the End.X SID for the purpose of load balancing. The use of the weight is defined in [RFC8402]. o Reserved2: 2 octets field. It MUST be set to 0 on transmission and MUST be ignored on receipt. o Neighbor ID: 4 octets field. It carries the OSPFv3 Router-id of the neighbor. o SID: 16 octets field. This field encodes the advertised SRv6 SID. o Sub-TLVs: Used to advertise Sub-TLVs that provide additional attributes for the given SRv6 SID. 9. SRv6 SID Structure Sub-TLV SRv6 SID Structure Sub-TLV is used to advertise the structure of the SRv6 SID as defined in [RFC8986]. It is used as an optional Sub-TLV of the following: o SRv6 End SID Sub-TLV (refer Section 7) o SRv6 End.X SID Sub-TLV (refer Section 8.1) o SRv6 LAN End.X SID Sub-TLV (refer Section 8.2) The Sub-TLV has the following format: Li, et al. Expires December 31, 2022 [Page 18] Internet-Draft OSPFv3 Extensions for SRV6 June 2022 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 | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LB Length | LN Length | Fun. Length | Arg. Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 8: SRv6 SID Structure Sub-TLV Where: Type: 2 octets field. The value for this type is TBD. Length: 2 octets field. It carries the value 4. LB Length: 1 octet field. SRv6 SID Locator Block length in bits. LN Length: 1 octet bit field. SRv6 SID Locator Node length in bits. Function Length: 1 octet field. SRv6 SID Function length in bits. Argument Length: 1 octet field. SRv6 SID Argument length in bits. The SRv6 SID Structure Sub-TLV MUST NOT appear more than once in its parent Sub-TLV. If it appears more than once in its parent Sub-TLV, the parent Sub-TLV MUST be ignored by the receiver. The sum of all four sizes advertised in SRv6 SID Structure Sub-TLV MUST be less than or equal to 128 bits. If the sum of all four sizes advertised in the SRv6 SID Structure Sub-TLV is larger than 128 bits, the parent TLV/Sub-TLV MUST be ignored by the receiver. The SRv6 SID Structure Sub-TLV is intended for informational use by the control and management planes. It MUST NOT be used at a transit node (as defined in [RFC8754]) for forwarding packets. As an example, this information could be used for: o validation of SRv6 SIDs being instantiated in the network and advertised via OSPFv3. These can be learnt by controllers via BGP-LS and then be monitored for conformance to the SRv6 SID allocation scheme chosen by the operator as described in Section 3.2 of [RFC8986]. Li, et al. Expires December 31, 2022 [Page 19] Internet-Draft OSPFv3 Extensions for SRV6 June 2022 o verification and the automation for securing the SRv6 domain by provisioning filtering rules at SR domain boundaries as described in Section 5 of [RFC8754]. The details of these potential applications are outside the scope of this document. 10. Advertising Endpoint Behaviors Endpoint behaviors are defined in [RFC8986]. The codepoints for the Endpoint behaviors are defined in the in the "SRv6 Endpoint Behaviors" registry of [RFC8986]. This section lists the Endpoint behaviors and their codepoints, which MAY be advertised by OSPFv3 and the Sub-TLVs in which each type MAY appear. |-----------------------|--------------------|-----|-------|-----------| | Endpoint | Endpoint | End | End.X | LAN End.X | | Behavior | Behavior Codepoint | SID | SID | SID | |-----------------------|--------------------|-----|-------|-----------| | End (PSP, USP, USD) | 1-4, 28-31 | Y | N | N | |-----------------------|--------------------|-----|-------|-----------| | End.X (PSP, USP, USD) | 5-8, 32-35 | N | Y | Y | |-----------------------|--------------------|-----|-------|-----------| | End.DX6 | 16 | N | Y | Y | |-----------------------|--------------------|-----|-------|-----------| | End.DX4 | 17 | N | Y | Y | |-----------------------|--------------------|-----|-------|-----------| | End.DT6 | 18 | Y | N | N | |-----------------------|--------------------|-----|-------|-----------| | End.DT4 | 19 | Y | N | N | |-----------------------|--------------------|-----|-------|-----------| | End.DT64 | 20 | Y | N | N | |-----------------------|--------------------|-----|-------|-----------| Figure 9: SRv6 Endpoint Behaviors in OSPFv3 11. Security Considerations Existing security extensions as described in [RFC5340] and [RFC8362] apply to these SRv6 extensions. While OSPFv3 is under a single administrative domain, there can be deployments where potential attackers have access to one or more networks in the OSPFv3 routing domain. In these deployments, stronger authentication mechanisms such as those specified in [RFC4552] or [RFC7166] SHOULD be used. Implementations MUST assure that malformed TLV and Sub-TLV defined in this document are detected and do not provide a vulnerability for Li, et al. Expires December 31, 2022 [Page 20] Internet-Draft OSPFv3 Extensions for SRV6 June 2022 attackers to crash the OSPFv3 router or routing process. Reception of malformed TLV or Sub-TLV SHOULD be counted and/or logged for further analysis. Logging of malformed TLVs and Sub-TLVs SHOULD be rate-limited to prevent a Denial of Service (DoS) attack (distributed or otherwise) from overloading the OSPFv3 control plane. This document describes the OSPFv3 extensions required to support Segment Routing over an IPv6 data plane. The security considerations for Segment Routing are discussed in [RFC8402]. [RFC8986] defines the SRv6 Network Programming concept and specifies the main Segment Routing behaviors to enable the creation of interoperable overlays; the security considerations from that document apply too. The advertisement for an incorrect MSD value may have negative consequences, see [RFC8476] for additional considerations. Security concerns associated with the setting of the O-flag are described in [RFC9259]. Security concerns associated with the usage of Flex-Algorithms are described in [I-D.ietf-lsr-flex-algo]. 12. IANA Considerations This document requests IANA to perform allocations from OSPF and OSPFv3 related registries as well as creating of new registries as follows. 12.1. OSPF Router Information TLVs This document requests allocation of a new code point in the "OSPF Router Information (RI) TLVs" registry under the "OSPF Parameters" registry for the new TLV below: Type TBD (suggested 20): SRv6-Capabilities TLV: Refer to Section 2. 12.2. OSPFv3 LSA Function Codes This document requests allocation of a new code point in the "OSPFv3 LSA Function Codes" registry under the "OSPFv3 Parameters" registry for the new LSA below: o Type TBD (suggested 42): SRv6 Locator LSA: Refer to Section 6. Li, et al. Expires December 31, 2022 [Page 21] Internet-Draft OSPFv3 Extensions for SRV6 June 2022 12.3. OSPFv3 Extended-LSA Sub-TLVs This document requests allocation of the following new code points in the "OSPFv3 Extended-LSA Sub-TLVs" registry under the "OSPFv3 Parameters" registry for the new Sub-TLVs below: o Type TBD (suggested 30): SRv6 SID Structure Sub-TLV : Refer to Section 9. o Type TBD (suggested 31): SRv6 End.X SID Sub-TLV : Refer to Section 8.1. o Type TBD (suggested 32): SRv6 LAN End.X SID Sub-TLV : Refer to Section 8.2. 12.4. OSPFv3 Locator LSA TLVs This document requests setting up of a new "OSPFv3 Locator LSA TLVs" registry, that defines top-level TLVs for the OSPFv3 SRv6 Locator LSA, under the "OSPFv3 Parameters" registry. The initial code-points assignment is as below: o Type 0: Reserved. o Type 1: SRv6 Locator TLV : Refer to Section 6.1. Types in the range 2-32767 are allocated via IETF Review or IESG Approval [RFC8126]. Types in the range 32768-33023 are Reserved for Experimental Use; these will not be registered with IANA and MUST NOT be mentioned by RFCs. Types in the range 33024-45055 are to be assigned on a First Come First Served (FCFS) basis. Types in the range 45056-65535 are not to be assigned at this time. Before any assignments can be made in the 33024-65535 range, there MUST be an IETF specification that specifies IANA Considerations that cover the range being assigned. 12.5. OSPFv3 Locator LSA Sub-TLVs This document requests setting up of a new "OSPFv3 Locator LSA Sub- TLVs" registry, that defines Sub-TLVs at any level of nesting for the SRv6 Locator LSA, to be added under the "OSPFv3 Parameters" registry. The initial code-points assignment is as below: Li, et al. Expires December 31, 2022 [Page 22] Internet-Draft OSPFv3 Extensions for SRV6 June 2022 o Type 0: Reserved. o Type 1: SRv6 End SID Sub-TLV : Refer to Section 7. o Type 10: SRv6 SID Structure Sub-TLV : Refer to Section 9. Types in the range 2-9 and 11-32767 are allocated via IETF Review or IESG Approval [RFC8126]. Types in the range 32768-33023 are Reserved for Experimental Use; these will not be registered with IANA and MUST NOT be mentioned by RFCs. Types in the range 33024-45055 are to be assigned on a First Come First Served (FCFS) basis. Types in the range 45056-65535 are not to be assigned at this time. Before any assignments can be made in the 33024-65535 range, there MUST be an IETF specification that specifies IANA Considerations that cover the range being assigned. 13. Acknowledgements The authors would like to acknowledge the contributions from Dean Cheng in the early versions of this document. The authors would like to thank Acee Lindem and Chenzichao for their review and comments on this document. 14. References 14.1. Normative References [I-D.ietf-lsr-flex-algo] Psenak, P., Hegde, S., Filsfils, C., Talaulikar, K., and A. Gulko, "IGP Flexible Algorithm", draft-ietf-lsr-flex- algo-20 (work in progress), May 2022. [I-D.ietf-lsr-isis-srv6-extensions] Psenak, P., Filsfils, C., Bashandy, A., Decraene, B., and Z. Hu, "IS-IS Extensions to Support Segment Routing over IPv6 Dataplane", draft-ietf-lsr-isis-srv6-extensions-18 (work in progress), October 2021. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . Li, et al. Expires December 31, 2022 [Page 23] Internet-Draft OSPFv3 Extensions for SRV6 June 2022 [RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008, . [RFC7770] Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and S. Shaffer, "Extensions to OSPF for Advertising Optional Router Capabilities", RFC 7770, DOI 10.17487/RFC7770, February 2016, . [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 8126, DOI 10.17487/RFC8126, June 2017, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC8362] Lindem, A., Roy, A., Goethals, D., Reddy Vallem, V., and F. Baker, "OSPFv3 Link State Advertisement (LSA) Extensibility", RFC 8362, DOI 10.17487/RFC8362, April 2018, . [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., Decraene, B., Litkowski, S., and R. Shakir, "Segment Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, July 2018, . [RFC8476] Tantsura, J., Chunduri, U., Aldrin, S., and P. Psenak, "Signaling Maximum SID Depth (MSD) Using OSPF", RFC 8476, DOI 10.17487/RFC8476, December 2018, . [RFC8665] Psenak, P., Ed., Previdi, S., Ed., Filsfils, C., Gredler, H., Shakir, R., Henderickx, W., and J. Tantsura, "OSPF Extensions for Segment Routing", RFC 8665, DOI 10.17487/RFC8665, December 2019, . [RFC8666] Psenak, P., Ed. and S. Previdi, Ed., "OSPFv3 Extensions for Segment Routing", RFC 8666, DOI 10.17487/RFC8666, December 2019, . [RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J., Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header (SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020, . Li, et al. Expires December 31, 2022 [Page 24] Internet-Draft OSPFv3 Extensions for SRV6 June 2022 [RFC8986] Filsfils, C., Ed., Camarillo, P., Ed., Leddy, J., Voyer, D., Matsushima, S., and Z. Li, "Segment Routing over IPv6 (SRv6) Network Programming", RFC 8986, DOI 10.17487/RFC8986, February 2021, . [RFC9259] Ali, Z., Filsfils, C., Matsushima, S., Voyer, D., and M. Chen, "Operations, Administration, and Maintenance (OAM) in Segment Routing over IPv6 (SRv6)", RFC 9259, DOI 10.17487/RFC9259, June 2022, . 14.2. Informative References [RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering (TE) Extensions to OSPF Version 2", RFC 3630, DOI 10.17487/RFC3630, September 2003, . [RFC4552] Gupta, M. and N. Melam, "Authentication/Confidentiality for OSPFv3", RFC 4552, DOI 10.17487/RFC4552, June 2006, . [RFC7166] Bhatia, M., Manral, V., and A. Lindem, "Supporting Authentication Trailer for OSPFv3", RFC 7166, DOI 10.17487/RFC7166, March 2014, . Authors' Addresses Zhenbin Li Huawei Technologies Email: lizhenbin@huawei.com Zhibo Hu Huawei Technologies Email: huzhibo@huawei.com Ketan Talaulikar (editor) Arrcus Inc India Email: ketant.ietf@gmail.com Li, et al. Expires December 31, 2022 [Page 25] Internet-Draft OSPFv3 Extensions for SRV6 June 2022 Peter Psenak Cisco Systems Slovakia Email: ppsenak@cisco.com Li, et al. Expires December 31, 2022 [Page 26]