Networking Working Group P. Psenak, Ed. Internet-Draft C. Filsfils Intended status: Standards Track Cisco Systems Expires: April 11, 2021 A. Bashandy Individual B. Decraene Orange Z. Hu Huawei Technologies October 8, 2020 IS-IS Extension to Support Segment Routing over IPv6 Dataplane draft-ietf-lsr-isis-srv6-extensions-11 Abstract Segment Routing (SR) allows for a flexible definition of end-to-end paths by encoding paths as sequences of topological sub-paths, called "segments". Segment routing architecture can be implemented over an MPLS data plane as well as an IPv6 data plane. This draft describes the IS-IS extensions required to support Segment Routing over an IPv6 data plane. 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. 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 April 11, 2021. Psenak, et al. Expires April 11, 2021 [Page 1] Internet-Draft ISIS Srv6 Extension October 2020 Copyright Notice Copyright (c) 2020 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 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 . . . . . . . . . . . . . . . . . . . . . . . . 3 2. SRv6 Capabilities sub-TLV . . . . . . . . . . . . . . . . . . 4 3. Advertising Supported Algorithms . . . . . . . . . . . . . . 4 4. Advertising Maximum SRv6 SID Depths . . . . . . . . . . . . . 5 4.1. Maximum Segments Left MSD Type . . . . . . . . . . . . . 5 4.2. Maximum End Pop MSD Type . . . . . . . . . . . . . . . . 5 4.3. Maximum H.Encaps MSD Type . . . . . . . . . . . . . . . . 5 4.4. Maximum End D MSD Type . . . . . . . . . . . . . . . . . 6 5. SRv6 SIDs and Reachability . . . . . . . . . . . . . . . . . 6 6. Advertising Anycast Property . . . . . . . . . . . . . . . . 7 7. Advertising Locators and End SIDs . . . . . . . . . . . . . . 8 7.1. SRv6 Locator TLV Format . . . . . . . . . . . . . . . . . 8 7.2. SRv6 End SID sub-TLV . . . . . . . . . . . . . . . . . . 10 8. Advertising SRv6 Adjacency SIDs . . . . . . . . . . . . . . . 11 8.1. SRv6 End.X SID sub-TLV . . . . . . . . . . . . . . . . . 12 8.2. SRv6 LAN End.X SID sub-TLV . . . . . . . . . . . . . . . 13 9. SRv6 SID Structure Sub-Sub-TLV . . . . . . . . . . . . . . . 15 10. Advertising Endpoint Behaviors . . . . . . . . . . . . . . . 16 11. Implementation Status . . . . . . . . . . . . . . . . . . . . 16 11.1. Cisco . . . . . . . . . . . . . . . . . . . . . . . . . 17 11.2. Huawei . . . . . . . . . . . . . . . . . . . . . . . . . 17 11.3. Juniper . . . . . . . . . . . . . . . . . . . . . . . . 17 11.4. Arrcus . . . . . . . . . . . . . . . . . . . . . . . . . 17 11.5. Interoperability Testing. . . . . . . . . . . . . . . . 18 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18 12.1. SRv6 Locator TLV . . . . . . . . . . . . . . . . . . . . 18 12.1.1. SRv6 End SID sub-TLV . . . . . . . . . . . . . . . . 18 12.1.2. Revised sub-TLV table . . . . . . . . . . . . . . . 18 12.2. SRv6 Capabilities sub-TLV . . . . . . . . . . . . . . . 19 12.3. SRv6 End.X SID and SRv6 LAN End.X SID sub-TLVs . . . . . 19 12.4. MSD Types . . . . . . . . . . . . . . . . . . . . . . . 20 Psenak, et al. Expires April 11, 2021 [Page 2] Internet-Draft ISIS Srv6 Extension October 2020 12.5. Sub-Sub-TLVs for SID Sub-TLVs . . . . . . . . . . . . . 20 12.6. Prefix Attribute Flags Sub-TLV . . . . . . . . . . . . . 20 13. Security Considerations . . . . . . . . . . . . . . . . . . . 21 14. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 21 15. References . . . . . . . . . . . . . . . . . . . . . . . . . 22 15.1. Normative References . . . . . . . . . . . . . . . . . . 22 15.2. Informative References . . . . . . . . . . . . . . . . . 24 15.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 25 1. Introduction With Segment Routing (SR) [RFC8402], a node steers a packet through an ordered list of instructions, called segments. Segments are identified through Segment Identifiers (SIDs). Segment Routing can be directly instantiated on the IPv6 data plane through the use of the Segment Routing Header defined in [RFC8754]. SRv6 refers to this SR instantiation on the IPv6 dataplane. The network programming paradigm [I-D.ietf-spring-srv6-network-programming] is central to SRv6. It describes how any behavior can be bound to a SID and how any network program can be expressed as a combination of SIDs. This document specifies IS-IS extensions that allow the IS-IS protocol to encode some of these SIDs and their behaviors. Familiarity with the network programming paradigm [I-D.ietf-spring-srv6-network-programming] is necessary to understand the extensions specified in this document. This document defines one new top level IS-IS TLV and several new IS- IS sub-TLVs. The SRv6 Capabilities sub-TLV announces the ability to support SRv6. Several new sub-TLVs are defined to advertise various SRv6 Maximum SID Depths. The new SRv6 Locator top level TLV announces SRv6 locators - a form of summary address for the set of topology/algorithm specific SIDs instantiated at the node. The SRv6 End SID sub-TLV, the SRv6 End.X SID sub-TLV, and the SRv6 LAN End.X SID sub-TLV are used to advertise which SIDs are Psenak, et al. Expires April 11, 2021 [Page 3] Internet-Draft ISIS Srv6 Extension October 2020 instantiated at a node and what Endpoint behavior is bound to each instantiated SID. 2. SRv6 Capabilities sub-TLV A node indicates that it supports the SR Segment Endpoint Node functionality as specified in [RFC8754] by advertising a new SRv6 Capabilities sub-TLV of the router capabilities TLV [RFC7981]. The SRv6 Capabilities sub-TLV may contain optional sub-sub-TLVs. No sub-sub-TLVs are currently defined. The SRv6 Capabilities sub-TLV has the following format: 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | optional sub-sub-TLVs... Type: 25 Length: 2 + length of sub-sub-TLVs Flags: 2 octets The following flags are defined: 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | |O| | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ where: O-flag: If set, the router supports use of the O-bit in the Segment Routing Header(SRH) as defined in [I-D.ietf-6man-spring-srv6-oam]. 3. Advertising Supported Algorithms SRv6 capable router indicates supported algorithm(s) by advertising the SR Algorithm TLV as defined in [RFC8667]. Psenak, et al. Expires April 11, 2021 [Page 4] Internet-Draft ISIS Srv6 Extension October 2020 4. Advertising Maximum SRv6 SID Depths [RFC8491] defines the means to advertise node/link specific values for Maximum SID Depths (MSD) of various types. Node MSDs are advertised in a sub-TLV of the Router Capabilities TLV [RFC7981]. Link MSDs are advertised in a sub-TLV of TLVs 22, 23, 141, 222, and 223. This document defines the relevant SRv6 MSDs and requests MSD type assignments in the MSD Types registry created by [RFC8491]. 4.1. Maximum Segments Left MSD Type The Maximum Segments Left MSD Type specifies the maximum value of the "SL" field [RFC8754] in the SRH of a received packet before applying the Endpoint behavior associated with a SID. SRH Max SL Type: 41 If no value is advertised the supported value is assumed to be 0. 4.2. Maximum End Pop MSD Type The Maximum End Pop MSD Type specifies the maximum number of SIDs in the SRH to which the router can apply "PSP" or USP" behavior, as defined in [I-D.ietf-spring-srv6-network-programming] flavors. SRH Max End Pop Type: 42 If the advertised value is zero or no value is advertised then it is assumed that the router cannot apply PSP or USP flavors. 4.3. Maximum H.Encaps MSD Type The Maximum H.Encaps MSD Type specifies the maximum number of SIDs that can be included as part of the "H.Encaps" behavior as defined in [I-D.ietf-spring-srv6-network-programming]. SRH Max H.encaps Type: 44 If the advertised value is zero or no value is advertised then the router can apply H.Encaps only by encapsulating the incoming packet in another IPv6 header without SRH the same way IPinIP encapsulation is performed. If the advertised value is non-zero then the router supports both IPinIP and SRH encapsulation subject to the SID limitation specified by the advertised value. Psenak, et al. Expires April 11, 2021 [Page 5] Internet-Draft ISIS Srv6 Extension October 2020 4.4. Maximum End D MSD Type The Maximum End D MSD Type specifies the maximum number of SIDs in an SRH when performing decapsulation associated with "End.Dx" behaviors (e.g., "End.DX6" and "End.DT6") as defined in [I-D.ietf-spring-srv6-network-programming]. SRH Max End D Type: 45 If the advertised value is zero or no value is advertised then it is assumed that the router cannot apply "End.DX6" or "End.DT6" behaviors if the outer IPv6 header contains an SRH. 5. SRv6 SIDs and Reachability As discussed in [I-D.ietf-spring-srv6-network-programming], an SRv6 Segment Identifier (SID) is 128 bits and consists of Locator, Function and Argument parts. A node is provisioned with topology/algorithm specific locators for each of the topology/algorithm pairs supported by that node. Each locator is a covering prefix for all SIDs provisioned on that node which have the matching topology/algorithm. Locators MUST be advertised in the SRv6 Locator TLV (see Section 7.1). 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 topology/algorithm is supported by the receiving node. Locators are routable and MAY also be advertised in Prefix Reachability TLVs (236 or 237). Locators associated with Flexible Algorithms [I-D.ietf-lsr-flex-algo] SHOULD NOT be advertised in Prefix Reachability TLVs (236 or 237). Locators associated with algorithm 0 and 1 (for all supported topologies) SHOULD be advertised in a Prefix Reachability TLV (236 or 237) so that legacy routers (i.e., routers which do NOT support SRv6) will install a forwarding entry for algorithm 0 and 1 SRv6 traffic. In cases where a locator advertisement is received in both a Prefix Reachability TLV and an SRv6 Locator TLV, the Prefix Reachability advertisement MUST be preferred when installing entries in the forwarding plane. This is to prevent inconsistent forwarding entries between SRv6 capable and SRv6 incapable routers. Psenak, et al. Expires April 11, 2021 [Page 6] Internet-Draft ISIS Srv6 Extension October 2020 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 in TLVs 22, 23, 222, 223, and 141. SRv6 SIDs 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 topology/algorithm pair will be forwarded correctly, while SRv6 SIDs associated with an unsupported topology/algorithm pair 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. There are a number of ways in which this requirement could be compromised. In order to ensure correct forwarding, network operators should take steps to make sure that this requirement is not compromised. o Another locator associated with a different topology/algorithm is the longest match o A prefix advertisement (i.e., from TLV 236 or 237) is the longest match 6. Advertising Anycast Property Both prefixes and SRv6 Locators may be configured as anycast and as such the same value can be advertised by multiple routers. It is useful for other routers to know that the advertisement is for an anycast identifier. A new flag in "Bit Values for Prefix Attribute Flags Sub-TLV" registry [RFC7794] is defined to advertise the anycast property: Bit #: 4 Name: Anycast Flag (A-flag) When the prefix/SRv6 locator is configured as anycast, the A-flag SHOULD be set. Otherwise, this flag MUST be clear. The A-flag MUST be preserved when leaked between levels. Psenak, et al. Expires April 11, 2021 [Page 7] Internet-Draft ISIS Srv6 Extension October 2020 The A-flag and the N-flag MUST NOT both be set. If both N-flag and A-flag are set in the prefix/SRv6 Locator advertisement, the receiving routers MUST ignore the N-flag. The same prefix/SRv6 Locator can be advertised by multiple routers. If at least one of them sets the A-Flag in its advertisement, the prefix/SRv6 Locator SHOULD be considered as anycast. A prefix/SRv6 Locator that is advertised by a single node and without an A-Flag SHOULD be interpreted as a node specific locator. All the nodes advertising the same anycast locator MUST instantiate the exact same set of SIDs under such anycast locator. Failure to do so may result in traffic being black-holed or mis-routed. The Prefix Attribute Flags Sub-TLV can be carried in the SRv6 Locator TLV as well as the Prefix Reachability TLVs. When a router originates both the Prefix Reachability TLV and the SRv6 Locator TLV for a given prefix, and the router is originating the Prefix Attribute Flags Sub-TLV in one of the TLVs, the router SHOULD advertise identical versions of the Prefix Attribute Flags Sub-TLV in both TLVs. 7. Advertising Locators and End SIDs The SRv6 Locator TLV is introduced to advertise SRv6 Locators and End SIDs associated with each locator. This new TLV shares the sub-TLV space defined for TLVs 135, 235, 236 and 237. 7.1. SRv6 Locator TLV Format The SRv6 Locator TLV has the following format: 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 |R|R|R|R| MTID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type: 27 Length: variable. R bits: reserved for future use. They MUST be set to zero on transmission and MUST be ignored on receipt. Psenak, et al. Expires April 11, 2021 [Page 8] Internet-Draft ISIS Srv6 Extension October 2020 MTID: Multitopology Identifier as defined in [RFC5120]. Note that the value 0 is legal. Followed by one or more locator entries of the form: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Metric | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Flags | Algorithm | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Loc Size | Locator (variable)... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sub-tlv-len | Sub-TLVs (variable) . . . | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Metric: 4 octets. As described in [RFC5305]. Flags: 1 octet. The following flags are defined 0 0 1 2 3 4 5 6 7 +-+-+-+-+-+-+-+-+ |D| Reserved | +-+-+-+-+-+-+-+-+ where: D bit: When the Locator is leaked from level-2 to level-1, the D bit MUST be set. Otherwise, this bit MUST be clear. Locators with the D bit set MUST NOT be leaked from level-1 to level-2. This is to prevent looping. The remaining bits are reserved for future use. They MUST be set to zero on transmission and MUST be ignored on receipt. Algorithm: 1 octet. Associated algorithm. Algorithm values are defined in the IGP Algorithm Type registry. Loc-Size: 1 octet. Number of bits in the SRv6 Locator field. (1 - 128) Locator: 1-16 octets. This field encodes the advertised SRv6 Locator. The Locator is encoded in the minimal number of octets for the given number of bits. Trailing bits MUST be set to zero and ignored when received. Psenak, et al. Expires April 11, 2021 [Page 9] Internet-Draft ISIS Srv6 Extension October 2020 Sub-TLV-length: 1 octet. Number of octets used by sub-TLVs Optional sub-TLVs. 7.2. SRv6 End SID sub-TLV The SRv6 End SID sub-TLV is introduced to advertise SRv6 Segment Identifiers (SID) with Endpoint behaviors which do not require a particular neighbor in order to be correctly applied [I-D.ietf-spring-srv6-network-programming]. SRv6 SIDs associated with a neighbor are advertised using the sub-TLVs defined in Section 8. This new sub-TLV is advertised in the SRv6 Locator TLV defined in the previous section. SRv6 End SIDs inherit the topology/algorithm from the parent locator. The SRv6 End SID sub-TLV has the following format: 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 | Endpoint Behavior | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SID (128 bits) . . . | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SID (cont . . .) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SID (cont . . .) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SID (cont . . .) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Sub-sub-tlv-len| sub-sub-TLVs (variable) . . . | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type: 5. Length: variable. Flags: 1 octet. No flags are currently defined. Endpoint Behavior: 2 octets, as defined in [I-D.ietf-spring-srv6- network-programming]. Legal behavior values for this sub-TLV are defined in Section 10 of this document. Psenak, et al. Expires April 11, 2021 [Page 10] Internet-Draft ISIS Srv6 Extension October 2020 SID: 16 octets. This field encodes the advertised SRv6 SID. Sub-sub-TLV-length: 1 octet. Number of octets used by sub-sub- TLVs. Optional sub-sub-TLVs. The SRv6 End SID MUST be a subnet of the associated Locator. SRv6 End SIDs which are NOT a subnet of the associated locator MUST be ignored. Multiple SRv6 End SIDs MAY be associated with the same locator. In cases where the number of SRv6 End SID sub-TLVs exceeds the capacity of a single TLV, multiple Locator TLVs for the same locator MAY be advertised. For a given MTID/Locator the algorithm MUST be the same in all TLVs. If this restriction is not met all TLVs for that MTID/ Locator MUST be ignored. 8. Advertising SRv6 Adjacency SIDs Certain SRv6 Endpoint behaviors [I-D.ietf-spring-srv6-network-programming] are associated with a particular adjacency. This document defines two new sub-TLVs of TLV 22, 23, 222, 223, and 141 - namely "SRv6 End.X SID" and "SRv6 LAN End.X SID". IS-IS Neighbor advertisements are topology specific - but not algorithm specific. End.X SIDs therefore inherit the topology from the associated neighbor advertisement, but the algorithm is specified in the individual SID. All End.X SIDs MUST be a subnet of a Locator with matching topology and 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. 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. Psenak, et al. Expires April 11, 2021 [Page 11] Internet-Draft ISIS Srv6 Extension October 2020 8.1. SRv6 End.X SID sub-TLV This sub-TLV is used to advertise an SRv6 SID associated with a point to point adjacency. Multiple SRv6 End.X SID sub-TLVs MAY be associated with the same adjacency. The SRv6 End.X SID sub-TLV has the following format: 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 | Algorithm | Weight | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Endpoint Behavior | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SID (128 bits) . . . | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SID (cont . . .) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SID (cont . . .) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SID (cont . . .) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Sub-sub-tlv-len| Sub-sub-TLVs (variable) . . . | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type: 43 Length: variable. Flags: 1 octet. 0 1 2 3 4 5 6 7 +-+-+-+-+-+-+-+-+ |B|S|P|Reserved | +-+-+-+-+-+-+-+-+ where: B-Flag: Backup flag. If set, the End.X SID is eligible for protection (e.g., using IPFRR) as described in [RFC8355]. Psenak, et al. Expires April 11, 2021 [Page 12] Internet-Draft ISIS Srv6 Extension October 2020 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. When set, the P-Flag indicates that the End.X SID is persistently allocated, i.e., the End.X SID value remains consistent across router restart and/or interface flap. Reserved bits: MUST be zero when originated and ignored when received. Algorithm: 1 octet. Associated algorithm. Algorithm values are defined in the IGP Algorithm Type registry. Weight: 1 octet. The value represents the weight of the End.X SID for the purpose of load balancing. The use of the weight is defined in [RFC8402]. Endpoint Behavior: 2 octets. As defined in [I-D.ietf-spring-srv6- network-programming] Legal behavior values for this sub-TLV are defined in Section 10. SID: 16 octets. This field encodes the advertised SRv6 SID. Sub-sub-TLV-length: 1 octet. Number of octets used by sub-sub- TLVs. Note that multiple TLVs for the same neighbor may be required in order to advertise all of the SRv6 End.X SIDs associated with that neighbor. 8.2. SRv6 LAN End.X SID sub-TLV This sub-TLV is used to advertise an SRv6 SID associated with a LAN adjacency. Since the parent TLV is advertising an adjacency to the Designated Intermediate System(DIS) for the LAN, it is necessary to include the System ID of the physical neighbor on the LAN with which the SRv6 SID is associated. Given that a large number of neighbors may exist on a given LAN a large number of SRv6 LAN END.X SID sub- TLVs may be associated with the same LAN. Note that multiple TLVs for the same DIS neighbor may be required in order to advertise all of the SRv6 End.X SIDs associated with that neighbor. The SRv6 LAN End.X SID sub-TLV has the following format: Psenak, et al. Expires April 11, 2021 [Page 13] Internet-Draft ISIS Srv6 Extension October 2020 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 | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | Neighbor System-ID (ID length octets) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Flags | Algorithm | Weight | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Endpoint Behavior | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SID (128 bits) . . . | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SID (cont . . .) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SID (cont . . .) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SID (cont . . .) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Sub-sub-tlv-len| sub-sub-TLVs (variable) . . . | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type: 44 Length: variable. Neighbor System-ID: IS-IS System-ID of length "ID Length" as defined in [ISO10589]. Flags: 1 octet. 0 1 2 3 4 5 6 7 +-+-+-+-+-+-+-+-+ |B|S|P|Reserved | +-+-+-+-+-+-+-+-+ where B,S, and P flags are as described in Section 8.1. Reserved bits MUST be zero when originated and MUST be ignored when received. Algorithm: 1 octet. Associated algorithm. Algorithm values are defined in the IGP Algorithm Type registry. Psenak, et al. Expires April 11, 2021 [Page 14] Internet-Draft ISIS Srv6 Extension October 2020 Weight: 1 octet. The value represents the weight of the End.X SID for the purpose of load balancing. The use of the weight is defined in [RFC8402]. Endpoint Behavior: 2 octets. As defined in [I-D.ietf-spring-srv6- network-programming] Legal behavior values for this sub-TLV are defined in Section 10. SID: 16 octets. This field encodes the advertised SRv6 SID. Sub-sub-TLV-length: 1 octet. Number of octets used by sub-sub- TLVs. 9. SRv6 SID Structure Sub-Sub-TLV SRv6 SID Structure Sub-Sub-TLV is an optional Sub-Sub-TLV of: SRv6 End SID Sub-TLV (Section 7.2) SRv6 End.X SID Sub-TLV (Section 8.1) SRv6 LAN End.X SID Sub-TLV (Section 8.2) SRv6 SID Structure Sub-Sub-TLV is used to advertise the length of each individual part of the SRv6 SID as defined in [I-D.ietf-spring-srv6-network-programming]. It has the following format: 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ where: Type: 1 Length: 4 octets. LB Length: 1 octet. SRv6 SID Locator Block length in bits. LN Length: 1 octet. SRv6 SID Locator Node length in bits. Fun. Length: 1 octet. SRv6 SID Function length in bits. Psenak, et al. Expires April 11, 2021 [Page 15] Internet-Draft ISIS Srv6 Extension October 2020 Arg. Length: 1 octet. SRv6 SID Arguments length in bits. ISIS SRv6 SID Structure Sub-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 ISIS SRv6 SID Structure Sub- Sub-TLV must be lower or equal to 128 bits. If the sum of all four sizes advertised in the ISIS SRv6 SID Structure Sub-Sub-TLV is larger than 128 bits, the parent Sub-TLV MUST be ignored by the receiver. 10. Advertising Endpoint Behaviors Endpoint behaviors are defined in [I-D.ietf-spring-srv6-network-programming]. The codepoints for the Endpoint behaviors are defined in the "SRv6 Endpoint Behaviors" registry defined in [I-D.ietf-spring-srv6-network-programming]. This section lists the Endpoint behaviors which MAY be advertised by ISIS, together with their codepoints. If this behavior is advertised it MUST only be advertised in the TLV[s] as indicated by "Y" in the table below, and MUST NOT be advertised in the TLV[s] as indicated by "N" in the table below. 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 | 11. Implementation Status RFC Ed.: Please remove this section prior to publication. This section describes the implementation status of the ISIS SRv6 extensions. Psenak, et al. Expires April 11, 2021 [Page 16] Internet-Draft ISIS Srv6 Extension October 2020 11.1. Cisco Cisco's ISIS SRv6 implementation supports following functionalities: Types of SID supported: End, End.X, LAN End.X, END.OP Intra/Inter area/level support: Yes Anycast SID support: Yes, including A-flag (Section 6) SID Structure Sub-Sub-TLV: Yes 11.2. Huawei Huawei's ISIS SRv6 implementation supports following functionalities: Types of SID supported: End, End.X, LAN End.X Intra/Inter area/level support: Yes Anycast SID support: Yes, no A-flag support (Section 6) SID Structure Sub-Sub-TLV: Yes 11.3. Juniper Juniper's ISIS SRv6 implementation supports following functionalities: Types of SID supported: End, End.X, LAN End.X Intra/Inter area/level support: Yes Anycast SID support: Yes, no A-flag support (Section 6) SID Structure Sub-Sub-TLV: No 11.4. Arrcus Arrcus's ISIS SRv6 implementation supports following functionalities: Types of SID supported: End, End.X, LAN End.X Intra/Inter area/level support: Yes Anycast SID support: No (Section 6) SID Structure Sub-Sub-TLV: Yes Psenak, et al. Expires April 11, 2021 [Page 17] Internet-Draft ISIS Srv6 Extension October 2020 11.5. Interoperability Testing. EANTC interoperability testing has been performed in April 2019. Results can be found at EANTC site [1]. 12. IANA Considerations This document requests allocation for the following TLVs, sub-TLVs, and sub-sub-TLVs as well updating the ISIS TLV registry and defining a new registry. 12.1. SRv6 Locator TLV This document makes the following registrations in the the IS-IS TLV Codepoints registry: Type: 27 Description: SRv6 Locator TLV. Reference: This document (Section 7.1). A Locator TLV shares sub-TLV space with existing "Sub-TLVs for TLVs 135, 235, 236 and 237 registry". The name of this registry needs to be changed to "Sub-TLVs for TLVs 27, 135, 235, 236 and 237 registry". 12.1.1. SRv6 End SID sub-TLV This document makes the following registrations in the (renamed) "Sub-TLVs for TLVs 27, 135, 235, 236 and 237 registry": Type: 5 Description: SRv6 End SID sub-TLV. Reference: This document (Section 7.2). 12.1.2. Revised sub-TLV table The revised table of sub-TLVs for the (renamed) "Sub-TLVs for TLVs 27, 135, 235, 236 and 237 registry" is shown below: Psenak, et al. Expires April 11, 2021 [Page 18] Internet-Draft ISIS Srv6 Extension October 2020 Type 27 135 235 236 237 1 y y y y y 2 y y y y y 3 n y y y y 4 y y y y y 5 y n n n n 6 n y y y y 11 y y y y y 12 y y y y y 32 n y y y y 12.2. SRv6 Capabilities sub-TLV This document makes the following registrations in the "Sub- TLVs for TLV 242 registry": Type: 25 Description: SRv6 Capabilities sub-TLV. Reference: This document (Section 2). This document requests the creation of a new IANA managed registry for sub-sub-TLVs of the SRv6 Capability sub-TLV. The registration procedure is "Expert Review" as defined in [RFC8126]. Suggested registry name is "sub-sub-TLVs for SRv6 Capability sub-TLV". No sub- sub-TLVs are defined by this document except for the reserved value. 0: Reserved 1-255: Unassigned 12.3. SRv6 End.X SID and SRv6 LAN End.X SID sub-TLVs This document makes the following registrations in the "sub- TLVs for TLV 22, 23, 25, 141, 222 and 223 registry": Type: 43 Description: SRv6 End.X SID sub-TLV. Reference: This document (Section 8.1). Type: 44 Description: SRv6 LAN End.X SID sub-TLV. Psenak, et al. Expires April 11, 2021 [Page 19] Internet-Draft ISIS Srv6 Extension October 2020 Reference: This document (Section 8.2). Type 22 23 25 141 222 223 43 y y y y y y 44 y y y y y y 12.4. MSD Types This document makes the following registrations in the IGP MSD Types registry: Type Description ------------------ 41 SRH Max SL 42 SRH Max End Pop 44 SRH Max H.encaps 45 SRH Max End D 12.5. Sub-Sub-TLVs for SID Sub-TLVs This document requests a new IANA registry be created under the IS-IS TLV Codepoints Registry to control the assignment of sub-TLV types for the SID Sub-TLVs specified in this document - Section 7.2, Section 8.1, Section 8.2. The suggested name of the new registry is "Sub-Sub-TLVs for SID Sub-TLVs". The registration procedure is "Expert Review" as defined in [RFC8126]. The following assignments are made by this document: 0: Reserved 1: SRv6 SID Structure Sub-Sub-TLV (Section 9). 12.6. Prefix Attribute Flags Sub-TLV This document adds a new bit in the "Bit Values for Prefix Attribute Flags Sub-TLV" registry: Bit #: 4 Description: A bit Reference: This document (Section 6). Psenak, et al. Expires April 11, 2021 [Page 20] Internet-Draft ISIS Srv6 Extension October 2020 13. Security Considerations Security concerns for IS-IS are addressed in [ISO10589], [RFC5304], and [RFC5310]. 14. Contributors The following people gave a substantial contribution to the content of this document and should be considered as co-authors: Psenak, et al. Expires April 11, 2021 [Page 21] Internet-Draft ISIS Srv6 Extension October 2020 Stefano Previdi Huawei Technologies Email: stefano@previdi.net Paul Wells Cisco Systems Saint Paul, Minnesota United States Email: pauwells@cisco.com Daniel Voyer Email: daniel.voyer@bell.ca Satoru Matsushima Email: satoru.matsushima@g.softbank.co.jp Bart Peirens Email: bart.peirens@proximus.com Hani Elmalky Email: hani.elmalky@ericsson.com Prem Jonnalagadda Email: prem@barefootnetworks.com Milad Sharif Email: msharif@barefootnetworks.com> Robert Hanzl Cisco Systems Millenium Plaza Building, V Celnici 10, Prague 1, Prague, Czech Republic Email rhanzl@cisco.com Ketan Talaulikar Cisco Systems, Inc. Email: ketant@cisco.com 15. References 15.1. Normative References Psenak, et al. Expires April 11, 2021 [Page 22] Internet-Draft ISIS Srv6 Extension October 2020 [I-D.ietf-6man-spring-srv6-oam] Ali, Z., Filsfils, C., Matsushima, S., Voyer, D., and M. Chen, "Operations, Administration, and Maintenance (OAM) in Segment Routing Networks with IPv6 Data plane (SRv6)", draft-ietf-6man-spring-srv6-oam-07 (work in progress), July 2020. [I-D.ietf-spring-srv6-network-programming] Filsfils, C., Camarillo, P., Leddy, J., Voyer, D., Matsushima, S., and Z. Li, "SRv6 Network Programming", draft-ietf-spring-srv6-network-programming-24 (work in progress), October 2020. [ISO10589] Standardization", I. ". O. F., "Intermediate system to Intermediate system intra-domain routeing information exchange protocol for use in conjunction with the protocol for providing the connectionless-mode Network Service (ISO 8473), ISO/IEC 10589:2002, Second Edition.", Nov 2002. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi Topology (MT) Routing in Intermediate System to Intermediate Systems (IS-ISs)", RFC 5120, DOI 10.17487/RFC5120, February 2008, . [RFC5304] Li, T. and R. Atkinson, "IS-IS Cryptographic Authentication", RFC 5304, DOI 10.17487/RFC5304, October 2008, . [RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic Engineering", RFC 5305, DOI 10.17487/RFC5305, October 2008, . [RFC5310] Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R., and M. Fanto, "IS-IS Generic Cryptographic Authentication", RFC 5310, DOI 10.17487/RFC5310, February 2009, . [RFC7370] Ginsberg, L., "Updates to the IS-IS TLV Codepoints Registry", RFC 7370, DOI 10.17487/RFC7370, September 2014, . Psenak, et al. Expires April 11, 2021 [Page 23] Internet-Draft ISIS Srv6 Extension October 2020 [RFC7794] Ginsberg, L., Ed., Decraene, B., Previdi, S., Xu, X., and U. Chunduri, "IS-IS Prefix Attributes for Extended IPv4 and IPv6 Reachability", RFC 7794, DOI 10.17487/RFC7794, March 2016, . [RFC7981] Ginsberg, L., Previdi, S., and M. Chen, "IS-IS Extensions for Advertising Router Information", RFC 7981, DOI 10.17487/RFC7981, October 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, . [RFC8491] Tantsura, J., Chunduri, U., Aldrin, S., and L. Ginsberg, "Signaling Maximum SID Depth (MSD) Using IS-IS", RFC 8491, DOI 10.17487/RFC8491, November 2018, . [RFC8667] Previdi, S., Ed., Ginsberg, L., Ed., Filsfils, C., Bashandy, A., Gredler, H., and B. Decraene, "IS-IS Extensions for Segment Routing", RFC 8667, DOI 10.17487/RFC8667, 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, . 15.2. Informative 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-12 (work in progress), October 2020. [RFC8355] Filsfils, C., Ed., Previdi, S., Ed., Decraene, B., and R. Shakir, "Resiliency Use Cases in Source Packet Routing in Networking (SPRING) Networks", RFC 8355, DOI 10.17487/RFC8355, March 2018, . Psenak, et al. Expires April 11, 2021 [Page 24] Internet-Draft ISIS Srv6 Extension October 2020 [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, . 15.3. URIs [1] http://www.eantc.de/fileadmin/eantc/downloads/events/2017- 2020/MPLS2019/Segment_Routing_IPv6__SRv6_.pdf Authors' Addresses Peter Psenak (editor) Cisco Systems Pribinova Street 10 Bratislava 81109 Slovakia Email: ppsenak@cisco.com Clarence Filsfils Cisco Systems Brussels Belgium Email: cfilsfil@cisco.com Ahmed Bashandy Individual Email: abashandy.ietf@gmail.com Bruno Decraene Orange Issy-les-Moulineaux France Email: bruno.decraene@orange.com Zhibo Hu Huawei Technologies Email: huzhibo@huawei.com Psenak, et al. Expires April 11, 2021 [Page 25]