--- 1/draft-ietf-lsr-isis-srv6-extensions-04.txt 2020-02-17 06:13:13.778757209 -0800 +++ 2/draft-ietf-lsr-isis-srv6-extensions-05.txt 2020-02-17 06:13:13.826758435 -0800 @@ -1,24 +1,24 @@ Networking Working Group P. Psenak, Ed. Internet-Draft C. Filsfils Intended status: Standards Track Cisco Systems -Expires: July 18, 2020 A. Bashandy - Arrcus +Expires: August 20, 2020 A. Bashandy + Individual B. Decraene Orange Z. Hu Huawei Technologies - January 15, 2020 + February 17, 2020 IS-IS Extension to Support Segment Routing over IPv6 Dataplane - draft-ietf-lsr-isis-srv6-extensions-04.txt + draft-ietf-lsr-isis-srv6-extensions-05.txt 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. @@ -38,21 +38,21 @@ 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 July 18, 2020. + This Internet-Draft will expire on August 20, 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 @@ -68,36 +68,36 @@ 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 + 7.1. SRv6 Locator TLV Format . . . . . . . . . . . . . . . . . 9 7.2. SRv6 End SID sub-TLV . . . . . . . . . . . . . . . . . . 10 8. Advertising SRv6 Adjacency SIDs . . . . . . . . . . . . . . . 12 8.1. SRv6 End.X SID sub-TLV . . . . . . . . . . . . . . . . . 12 8.2. SRv6 LAN End.X SID sub-TLV . . . . . . . . . . . . . . . 14 9. SRv6 SID Structure Sub-Sub-TLV . . . . . . . . . . . . . . . 15 10. Advertising Endpoint Behaviors . . . . . . . . . . . . . . . 16 11. Implementation Status . . . . . . . . . . . . . . . . . . . . 17 11.1. Cisco . . . . . . . . . . . . . . . . . . . . . . . . . 17 11.2. Huawei . . . . . . . . . . . . . . . . . . . . . . . . . 17 11.3. Juniper . . . . . . . . . . . . . . . . . . . . . . . . 18 11.4. 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 . . . . . . . . . . . . . . . 19 + 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 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 @@ -113,21 +113,21 @@ 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 [I-D.ietf-6man-segment-routing-header]. 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 SID's. + 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. @@ -141,22 +141,24 @@ 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 instantiated at a node and what Endpoint behavior is bound to each instantiated SID. 2. SRv6 Capabilities sub-TLV - A node indicates that it has support for SRv6 by advertising a new - SRv6 Capabilities sub-TLV of the router capabilities TLV [RFC7981]. + A node indicates that it supports the SR Segment Endpoint Node + functionality as specified in [I-D.ietf-6man-segment-routing-header] + 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 | @@ -204,23 +206,22 @@ received packet before applying the Endpoint behavior associated with a SID. SRH Max SL Type: 41 (Suggested value - to be assigned by IANA) 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 top SRH in an SRH stack to which the router can apply "PSP" or - USP" as defined in [I-D.ietf-spring-srv6-network-programming] - flavors. + 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 (Suggested value - to be assigned by IANA) 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 @@ -241,22 +242,21 @@ 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 (Suggested value - to be assigned by IANA) 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 extension - header right underneath the outer IPv6 header is an SRH. + "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 @@ -267,51 +267,53 @@ 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 (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 SRv6 traffic. + 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 in 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 on SRv6 capable/SRv6 incapable routers. + 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. 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 + 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 @@ -332,61 +334,74 @@ 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. + 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 (Suggested value to be assigned by IANA) + + Length: variable. + + 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) . . . | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - Type: 27 (Suggested value to be assigned by IANA) - - Length: variable. - - MTID: Multitopology Identifier as defined in [RFC5120]. - Note that the value 0 is legal. - - Locator entry: - 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 | +-+-+-+-+-+-+-+-+ @@ -395,26 +410,27 @@ 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 SHOULD 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 Locator field. + 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. + octets for the given number of bits. Trailing bits MUST be set + to zero and ignored when received. 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 @@ -484,20 +500,28 @@ 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. + 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 @@ -665,22 +691,27 @@ 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. 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 TLV, - the parent TLV MUST be ignored by the receiver. + 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] and [I-D.ietf-6man-spring-srv6-oam]. 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 and their codepoints, which MAY be advertised by IS-IS and the SID sub-TLVs in which each type MAY @@ -733,21 +764,21 @@ Types of SID supported: End, End.X Intra/Inter area/level support: Yes Anycast SID support: Yes, no A-flag support (Section 6) SID Structure Sub-Sub-TLV: No 11.3. Juniper Juniper's implementation is in beta stage and supports most of the - sections of the this draft. + sections of this draft. 11.4. 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 @@ -767,30 +798,20 @@ 12.1.1. SRv6 End SID sub-TLV This document adds the following new sub-TLV to the (renamed) "Sub- TLVs for TLVs 27, 135, 235, 236 and 237 registry". Value: 5 (suggested - to be assigned by IANA) Name: SRv6 End SID - This document requests the creation of a new IANA managed registry - for sub-sub-TLVs of the SRv6 End SID sub-TLV. The registration - procedure is "Expert Review" as defined in [RFC7370]. Suggested - registry name is "sub-sub-TLVs for SRv6 End SID sub-TLV". No sub- - sub-TLVs are defined by this document except for the reserved value. - - 0: Reserved - - 1-255: Unassigned - 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: Type 27 135 235 236 237 1 n y y y y 2 n y y y y 3 n y y y y @@ -941,22 +964,22 @@ [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-03 (work in progress), December 2019. [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-08 (work in - progress), January 2020. + draft-ietf-spring-srv6-network-programming-09 (work in + progress), February 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, @@ -1046,21 +1069,21 @@ Email: ppsenak@cisco.com Clarence Filsfils Cisco Systems Brussels Belgium Email: cfilsfil@cisco.com Ahmed Bashandy - Arrcus + Individual Email: abashandy.ietf@gmail.com Bruno Decraene Orange Issy-les-Moulineaux France Email: bruno.decraene@orange.com