--- 1/draft-ietf-lsr-ip-flexalgo-03.txt 2021-12-19 14:13:14.808407171 -0800 +++ 2/draft-ietf-lsr-ip-flexalgo-04.txt 2021-12-19 14:13:14.848408168 -0800 @@ -1,23 +1,23 @@ LSR Working Group W. Britto Internet-Draft S. Hegde Intended status: Standards Track P. Kaneriya -Expires: November 15, 2021 R. Shetty +Expires: 22 June 2022 R. Shetty R. Bonica Juniper Networks P. Psenak Cisco Systems - May 14, 2021 + 19 December 2021 IGP Flexible Algorithms (Flex-Algorithm) In IP Networks - draft-ietf-lsr-ip-flexalgo-03 + draft-ietf-lsr-ip-flexalgo-04 Abstract An IGP Flexible Algorithm (Flex-Algorithm) allows IGP to compute constraint-based paths. As currently defined, IGP Flex-Algorithm is used with Segment Routing (SR) data planes - SR MPLS and SRv6. Therefore, Flex-Algorithm cannot be deployed in the absence of SR. This document extends IGP Flex-Algorithm, so that it can be used for regular IPv4 and IPv6 prefixes. This allows Flex-Algorithm to be @@ -31,83 +31,82 @@ Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." - This Internet-Draft will expire on November 15, 2021. + This Internet-Draft will expire on 22 June 2022. Copyright Notice Copyright (c) 2021 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal - Provisions Relating to IETF Documents - (https://trustee.ietf.org/license-info) in effect on the date of - publication of this document. Please review these documents - carefully, as they describe your rights and restrictions with respect - to this document. Code Components extracted from this document must - 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. + 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 Revised BSD License text as + described in Section 4.e of the Trust Legal Provisions and are + provided without warranty as described in the Revised BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3 3. Egress Node Procedures . . . . . . . . . . . . . . . . . . . 3 4. Advertising Flex-Algorithm Definitions (FAD) . . . . . . . . 3 5. Advertising IP Flex-Algorithm Participation . . . . . . . . . 3 5.1. The ISIS IP Algorithm Sub-TLV . . . . . . . . . . . . . . 4 5.2. The OSPF IP Algorithm TLV . . . . . . . . . . . . . . . . 5 6. Advertising IP Flex-Algorthm Reachability . . . . . . . . . . 6 6.1. The ISIS IPv4 Algorithm Prefix Reachability TLV . . . . . 6 6.2. The ISIS IPv6 Algorithm Prefix Reachability TLV . . . . . 8 - 6.3. The OSPFv2 Algorithm Prefix Reachability TLV . . . . . . 9 - 6.4. The OSPFv3 Flex-Algorithm IP Prefix Opaque LSA . . . . . 11 - 7. Calculating of IP Flex-Algorthm Paths . . . . . . . . . . . . 11 - 8. IP Flex-Algorthm Forwarding . . . . . . . . . . . . . . . . . 12 - 9. Deployment Considerations . . . . . . . . . . . . . . . . . . 12 - 10. Protection . . . . . . . . . . . . . . . . . . . . . . . . . 13 - 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 - 12. Security Considerations . . . . . . . . . . . . . . . . . . . 14 - 13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14 - 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 - 14.1. Normative References . . . . . . . . . . . . . . . . . . 14 - 14.2. Informative References . . . . . . . . . . . . . . . . . 16 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16 + 6.3. The OSPFv2 IP Algorithm Prefix Reachability Sub-TLV . . . 9 + 6.4. The OSPFv3 IP Algorithm Prefix Reachability Sub-TLV . . . 10 + 6.5. The OSPF IP Flexible Algorithm ASBR Metric Sub-TLV . . . 11 + 7. Calculating of IP Flex-Algorthm Paths . . . . . . . . . . . . 13 + 8. IP Flex-Algorthm Forwarding . . . . . . . . . . . . . . . . . 13 + 9. Deployment Considerations . . . . . . . . . . . . . . . . . . 14 + 10. Protection . . . . . . . . . . . . . . . . . . . . . . . . . 14 + 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 + 12. Security Considerations . . . . . . . . . . . . . . . . . . . 16 + 13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 16 + 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 17 + 14.1. Normative References . . . . . . . . . . . . . . . . . . 17 + 14.2. Informative References . . . . . . . . . . . . . . . . . 18 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19 1. Introduction An IGP Flex-Algorithm as specified in [I-D.ietf-lsr-flex-algo] computes a constraint-based path to: - o All Flex-Algorithm specific Prefix Segment Identifiers (SIDs) + * All Flex-Algorithm specific Prefix Segment Identifiers (SIDs) [RFC8402]. - o All Flex-Algorityhm specific SRv6 Locators - [I-D.ietf-spring-srv6-network-programming]. + * All Flex-Algorityhm specific SRv6 Locators [RFC8986]. Therefore, Flex-Algorithm cannot be deployed in the absence of SR and SRv6. This document extends Flex-Algorithm, allowing it to compute paths to: - o An IPv4 [RFC0791] address. + * An IPv4 [RFC0791] address. - o An IPv6 [RFC8200] address. + * An IPv6 [RFC8200] address. This allows Flex-Algorithm to be deployed in any IP network, even in the absence of SR and SRv6. 2. 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 @@ -135,23 +134,22 @@ in Sections 5, 6 and 7 of [I-D.ietf-lsr-flex-algo]. 5. Advertising IP Flex-Algorithm Participation A node may use various algorithms when calculating paths to nodes and prefixes. Algorithm values are defined in the IGP Algorithm Type Registry [IANA-ALG]. A node MUST participate in a Flex-Algorithm to be: - o able to compute path for such Flex-Algorithm - - o be part of the topology for such Flex-Algorithm + * able to compute path for such Flex-Algorithm + * be part of the topology for such Flex-Algorithm Flex-Algorithm participation MUST be advertised for each Flex- Algorithm application independently, as specified in Section 10.2 of [I-D.ietf-lsr-flex-algo]. Using Flex-Algorithm for regular IPv4 and IPv6 prefixes represents a new Flex-Algorithm application (IP Flex- Algorithm), and as such the Flex-Algorithm participation for the IP Flex-Algorithm application MUST be signalled independently of any other Flex-Algorithm applications (e.g. SR). Following sections describe how the IP Flex-Algorithm participation @@ -165,25 +163,25 @@ 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Algorithm 1 | Algorithm 2 | Algorithm ... | Algorithm n | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: ISIS IP Algorithm Sub-TLV - o Type: IP Algorithm Sub-TLV (Value 29) + * Type: IP Algorithm Sub-TLV (Value 29) - o Length: Variable + * Length: Variable - o Algorithm (1 octet): value from 1 to 255. + * Algorithm (1 octet): value from 1 to 255. The IP Algorithm Sub-TLV MUST be propagated throughout the level and MUST NOT be advertised across level boundaries. Therefore, the S bit in the Router Capability TLV, in which the IP Algorithm Sub-TLV is advertised, MUST NOT be set. The IP Algorithm Sub-TLV is optional. It MUST NOT be advertised more than once at a given level. A router receiving multiple IP Algorithm sub-TLVs from the same originator SHOULD select the first advertisement in the lowest-numbered LSP and subsequent instances of @@ -210,25 +208,25 @@ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Algorithm 1 | Algorithm... | Algorithm n | | +- -+ | | + + Figure 2: OSPF IP Algorithm TLV - o Type: IP Algorithm TLV (Value TBD by IANA) + * Type: IP Algorithm TLV (Value TBD by IANA) - o Length: Variable + * Length: Variable - o Algorithm (1 octet): value from 1 to 255. + * Algorithm (1 octet): value from 1 to 255. The IP Algorithm TLV is optional. It SHOULD only be advertised once in the Router Information Opaque LSA. When multiple IP Algorithm TLVs are received from a given router, the receiver MUST use the first occurrence of the TLV in the Router Information Opaque LSA. If the IP Algorithm TLV appears in multiple Router Information Opaque LSAs that have different flooding scopes, the IP Algorithm TLV in the Router Information Opaque LSA with the area-scoped flooding scope MUST be used. If the IP Algorithm TLV @@ -252,26 +250,32 @@ in which the advertising node participates. 6. Advertising IP Flex-Algorthm Reachability To be able to associate the prefix with the Flex-Algorithm, the existing prefix reachability advertisements can not be used, because they advertise the prefix reachability in default algorithm 0. Instead, a new IP Flex-Algorithm reachability advertisements are defined in ISIS and OSPF. + The M-flag in FAD is not applicable to IP Algorithm Prefixes. Any IP + Algorithm Prefix advertisement includes the Algorithm and Metric + fields. When IP Algorithm Prefix is advertised between areas or + domains, the metric field in the IP Algorithm Prefix advertisement + MUST be used irrespective of the M-flag in the FAD advertisement. + Two new top-level TLVs are defined in ISIS [ISO10589] to advertise prefix reachability associated with a Flex-Algorithm. - o The IPv4 Algorithm Prefix Reachability TLV + * The IPv4 Algorithm Prefix Reachability TLV - o The IPv6 Algorithm Prefix Reachability TLV + * The IPv6 Algorithm Prefix Reachability TLV New top-level TLV of OSPFv2 Extended Prefix Opaque LSA [RFC7684] is defined to advertise prefix reachability associated with a Flex- Algorithm in OSPFv2. 6.1. The ISIS IPv4 Algorithm Prefix Reachability TLV A new top level TLV is defined for advertising IPv4 Flex-Algorithm Prefix Reachability in ISIS - IPv4 Algorithm Prefix Reachability TLV. @@ -280,72 +284,72 @@ The ISIS IPv4 Algorithm Prefix Reachability 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - ISIS IPv4 Algorithm Prefix Reachability TLV + Figure 3: ISIS IPv4 Algorithm Prefix Reachability TLV - o Type: IPv4 Algorithm Prefix Reachability TLV (Value 126). + * Type: IPv4 Algorithm Prefix Reachability TLV (Value 126). - o Length: variable. + * Length: variable. - o R bits (4 bits): reserved for future use. They MUST be set to + * R bits (4 bits): reserved for future use. They MUST be set to zero on transmission and MUST be ignored on receipt. - o MTID (12 bits): Multitopology Identifier as defined in [RFC5120]. + * MTID (12 bits): Multitopology Identifier as defined in [RFC5120]. Note that the value 0 is legal. Followed by one or more prefix 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Pfx Length | Prefix (variable)... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sub-tlv-len | Sub-TLVs (variable) . . . | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - ISIS IPv4 Algorithm Prefix Reachability TLV + Figure 4: ISIS IPv4 Algorithm Prefix Reachability TLV - o Metric (4 octets): Metric information. + * Metric (4 octets): Metric information. - o Flags (1 octet): + * Flags (1 octet): 0 1 2 3 4 5 6 7 +-+-+-+-+-+-+-+-+ |D| Reserved | +-+-+-+-+-+-+-+-+ D-flag: When the Prefix is leaked from level-2 to level-1, the D bit MUST be set. Otherwise, this bit MUST be clear. Prefixes with the D bit set MUST NOT be leaked from level-1 to level-2. This is to prevent looping. - o Algorithm (1 octet): Associated Algorithm from 1 to 255. + * Algorithm (1 octet): Associated Algorithm from 1 to 255. - o Prefix Len (1 octet): Prefix length measured in bits. + * Prefix Len (1 octet): Prefix length measured in bits. - o Prefix (variable length): Prefix mapped to Flex-Algorithm. + * Prefix (variable length): Prefix mapped to Flex-Algorithm. - o Optional Sub-TLV-length (1 octet): Number of octets used by sub- + * Optional Sub-TLV-length (1 octet): Number of octets used by sub- TLVs - o Optional sub-TLVs (variable length). + * Optional sub-TLVs (variable length). A router receiving multiple IPv4 Algorithm Prefix Reachability advertisements for the same prefix, from the same originator, each with a different Algorithm, MUST select the first advertisement in the lowest-numbered LSP and ignore any subsequent IPv4 Algorithm Prefix Reachability advertisements for the same prefix for any other Algorithm. A router receiving multiple IPv4 Algorithm Prefix Reachability advertisements for the same prefix, from different originators, each @@ -373,139 +377,200 @@ A router receiving multiple IPv6 Algorithm Prefix Reachability advertisements for the same prefix, from different originators, each with a different Algorithm, MUST ignore all of them and MUST NOT install any forwarding entries based on these advertisements. In cases where a prefix advertisement is received in both a IPv6 Prefix Reachability TLV and an IPv6 Algorithm Prefix Reachability TLV, the IPv6 Prefix Reachability advertisement MUST be preferred when installing entries in the forwarding plane. -6.3. The OSPFv2 Algorithm Prefix Reachability TLV +6.3. The OSPFv2 IP Algorithm Prefix Reachability Sub-TLV - A new top level TLV of OSPFv2 Extended Prefix Opaque LSA is defined - for advertising IPv4 Algorithm Prefix Reachability in OSPFv2 - OSPF - Algorithm Prefix Reachability TLV + A new Sub-TLV of OSPFv2 Extended Prefix TLV is defined for + advertising IP Algorithm Prefix Reachability in OSPFv2 - OSPFv2 IP + Algorithm Prefix Reachability Sub-TLV. - Multiple Algorithm Prefix Reachability TLV MAY be advertised in each - OSPFv2 Extended Prefix Opaque LSA. However, since the opaque LSA - type defines the flooding scope, the LSA flooding scope MUST satisfy - the application specific requirements for all the prefixes included - in a single OSPFv2 Extended Prefix Opaque LSA. The Algorithm Prefix - Reachability TLV has the following format: + The OSPFv2 IP Algorithm Prefix Reachability 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - | Route Type | Prefix Length | AF | Flags | - +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MT-ID | Algorithm | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - | Address Prefix (variable) | - +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Metric | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - | Sub-TLVs (variable) | - +- -+ - | | - OSPFv2 Algorithm Prefix Reachability TLV + Figure 5: OSPFv2 IP Algorithm Prefix Reachability Sub-TLV - Type: Algorithm Prefix Reachability TLV (Value TBD by IANA). + * Type (2 octets) : The value is TBD. - Length: Variable dependent on sub-TLVs. + * Length (1 octet): 8 - Route Type (1 octet): type of the OSPF route. Supported types - are: + * MT-ID (1 octet): Multi-Topology ID as defined in [RFC8402] - 1 - Intra-Area + * Algorithm (1 octet): Associated Algorithm from 1 to 255. + Algorithm values are defined in the IGP Algorithm Type registry. + If the value of Algorithm is 0 the TLV MUST be ignored. - 2 - Inter-Area - 3 - AS External with Type-1 Metric + * Reserved: (2 octets). SHOULD be set to 0 on transmission and MUST + be ignored on reception. - 4 - AS External with Type-2 Metric + * Metric (3 octets): The algorithm specific metric value. - 5 - NSSA External with Type-1 Metric + A OSPFv2 router receiving multiple OSPFv2 IP Algorithm Prefix + Reachability Sub-TLVs in the same OSPFv2 Extended Prefix TLV, MUST + select the first advertisement of this Sub-TLV and MUST ignore all + remaining occurences of this Sub-TLV in the OSPFv2 Extended Prefix + TLV. - 6 - NSSA External with Type-2 Metric + A OSPFv2 router receiving multiple OSPFv2 IP Algorithm Prefix + Reachability TLVs for the same prefix, from different originators, + each with a different Algorithm, MUST ignore all of them and MUST NOT + install any forwarding entries based on these advertisements. - Prefix Length (1 octet): Length of prefix in bits. + In cases where a prefix advertisement is received in any of the LSAs + advertising the prefix reachability for algorithm 0 (Router-LSA, + Summary-LSA, AS-external-LSA or NSSA AS-external LSA) and in an + OSPFv2 IP Algorithm Prefix Reachability TLV, only the prefix + reachability advertisement for algorithm 0 MUST be used and all + occurences of the OSPFv2 IP Algorithm Prefix Reachability TLV MUST be + ignored. - AF (1 octet): Address family for the prefix. Currently, the only - supported value is 0 for IPv4 unicast. The inclusion of address - family in this TLV allows for future extension. +6.4. The OSPFv3 IP Algorithm Prefix Reachability Sub-TLV - Flags (1 octet): Flags applicable to the prefix. Supported Flags - include: + The OSPFv3 IP Algorithm Prefix Reachability Sub-TLV is defined for + advertisement of the IP Algorithm Prefix Reachability in OSPFv3. - 0x80 - A-Flag (Attach flag): An Area Border Router (ABR) - generating an Extended Prefix TLV for inter-area prefix that is - locally connected or attached in other connected area SHOULD - set this flag. + The OSPFv3 IP Algorithm Prefix Reachability Sub-TLV is a sub-TLV of + the following OSPFv3 TLVs defined in [RFC8362]: - 0x40 - N-Flag (Node Flag): Set when the prefix identifies the - advertising router i.e., the prefix is a host prefix - advertising a globally reachable address typically associated - with a loopback address. The advertising router MAY choose to - not set this flag even when the above conditions are met. If - the flag is set and the prefix length is not a host prefix then - the flag MUST be ignored. The flag is preserved when the - OSPFv2 Extended Prefix Opaque LSA is propagated between areas. + * Intra-Area-Prefix TLV - MT-ID (1 octet): Multi-Topology ID as defined in [RFC8402] + * Inter-Area-Prefix TLV - Algorithm: (1 octet). Associated Algorithm from 1 to 255. + * External-Prefix TLV - Adress Prefix: For the address family IPv4 unicast, the prefix - itself encoded as a 32-bit value. The default route is - represented by a prefix of length 0. Prefix encoding for other - address families is beyond the scope of this specification. + The format of OSPFv3 IP Algorithm Prefix Reachability Sub-TLV is + shown below: - Metric (4 octets): Metric information. + 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 | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Algorithm | Metric | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - If this TLV is advertised multiple times for the same prefix in the - same OSPFv2 Extended Prefix Opaque LSA, only the first instance of - the TLV is used by receiving OSPFv2 Routers. This situation SHOULD - be logged as an error. + Figure 6: OSPFv3 Algorithm Prefix Sub-TLV - If this TLV is advertised multiple times for the same prefix in - different OSPFv2 Extended Prefix Opaque LSAs originated by the same - OSPF router, the OSPF advertising router is re-originating Extended - Prefix Opaque LSAs for multiple prefixes and is most likely repacking - Algorithm Prefix Reachability TLVs in Extended Prefix Opaque LSAs. - In this case, the Algorithm Prefix Reachability TLV in the Extended - Prefix Opaque LSA with the smallest Opaque ID is used by receiving - OSPFv2 Routers. This situation may be logged as a warning. + Where: - It is RECOMMENDED that OSPF routers advertising Algorithm Prefix - Reachability TLVs in different Extended Prefix Opaque LSAs re- - originate these LSAs in ascending order of Opaque ID to minimize the - disruption. + Type (2 octets): The value is TBD. - A router receiving multiple Algorithm Prefix Reachability TLVs for - the same prefix, from different originators, each with a different - Algorithm, MUST ignore all of them and MUST NOT install any - forwarding entries based on these advertisements. + Length (2 octets): 4. - In cases where a prefix advertisement is received in any of the LSAs - advertising the prefix reachability for algorithm 0 (Router-LSA, - Summary-LSA, AS-external-LSA or NSSA AS-external LSA) and in an IPv4 - Algorithm Prefix Reachability TLV, the prefix reachability - advertisement for algorithm 0 MUST be preferred when installing - entries in the forwarding plane, regardless of the Route Type - advertised in IPv4 Algorithm Prefix Reachability TLV. + Algorithm (1 octet): Associated Algorithm from 1 to 255. + Algorithm values are defined in the IGP Algorithm Type registry. + If the value of Algorithm is 0 the TLV MUST be ignored. -6.4. The OSPFv3 Flex-Algorithm IP Prefix Opaque LSA + Metric (3 octets): The algorithm specific metric value. - TBD. + When the OSPFv3 IP Algorithm Prefix Reachability Sub-TLV is present, + the metric value in its parent TLV MUST be set to LSInfinity + ([RFC2328]). If the metric value in the parent TLV is not set to + LSInfinity, the OSPFv3 IP Algorithm Prefix Sub-TLV MUST be ignored by + the receiver. + + A OSPFv3 router receiving multiple OSPFv3 IP Algorithm Prefix + Reachability Sub-TLVs in the same parent TLV, MUST select the first + advertisement of this Sub-TLV and MUST ignore all remaining + occurences of this Sub-TLV in the parent TLV. + + A OSPFv3 router receiving multiple OSPFv3 IP Algorithm Prefix + Reachability TLVs for the same prefix, from different originators, + each with a different Algorithm, MUST ignore all of them and MUST NOT + install any forwarding entries based on these advertisements. + + In cases where a prefix advertisement is received in any of the TLVs + advertising the prefix reachability for algorithm 0 (Intra-Area- + Prefix TLV, Inter-Area-Prefix TLV, or External-Prefix TLV) with + metric other then LSInfinity, all OSPFv3 IP Algorithm Prefix TLVs + received for the prefix MUST be ignored. + +6.5. The OSPF IP Flexible Algorithm ASBR Metric Sub-TLV + + Section 10.2 of the [I-D.ietf-lsr-flex-algo] defines the OSPF + Flexible Algorithm ASBR Metric Sub-TLV (FAAM) that is used by OSPFv2 + and OSPFv3 to advertise Flex-Algorithm specific metric associated + with a given ASBR reachability advertisement by an ABR. + + As described in section 11 of [I-D.ietf-lsr-flex-algo] each + application signals the participation independently. IP Flex- + Algorithm participation is signalled independently of the Segment + Routing (SR) Flex-Algorithm participation. As a result, the + calculated topologies for SR and IP Flex-Algorithm could be + different. Such difference prevents the usage of FAAM for the + purpose of the IP Flex-Algorithm. + + The OSPF IP Flexible Algorithm ASBR Metric (IPFAAM) Sub-TLV is + defined for the advertisement of the IP Flex-Algorithm specific + metric associated with an ASBR by the ABR. + + The IPFAAM Sub-TLV is a Sub-TLV of the: + + - OSPFv2 Extended Inter-Area ASBR TLV as defined in + [I-D.ietf-lsr-flex-algo] + + - OSPFv3 Inter-Area-Router TLV defined in [RFC8362] + + OSPF IPFAAM 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 | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Algorithm | Reserved | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Metric | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + where: + + Type (2 octets): TBD for OSPFv2, TBD for OSPFv3. + + Length (2 octets): 8. + + Algorithm (1 octet): Associated Algorithm from 1 to 255. + Algorithm values are defined in the IGP Algorithm Type registry. + If the value of Algorithm is 0 the TLV MUST be ignored. + + Reserved: (3 octets). SHOULD be set to 0 on transmission and MUST + be ignored on reception. + + Metric (4 octets): The algorithm specific metric value. + + The usage of the IPFAAM Sub-TLV is similar to the usage of the FAAM + Sub-TLV defined in [I-D.ietf-lsr-flex-algo], but it is used to + advertise IP Flex-Algorithm metric. + + An OSPF ABR MUST include the OSPF IPFAAM Sub-TLVs as part of the ASBR + reachability advertisement between areas for every IP Flex-Algorithm + in which it participates and the ASBR is reachable in. + + FAAM Sub-TLV as defined in [I-D.ietf-lsr-flex-algo] MUST NOT be used + during IP Flex-Algorithm path calculation, IPFAAM Sub-TLV MUST be + used instead. 7. Calculating of IP Flex-Algorthm Paths IP Flex-Algorthm is considered as yet another application of the Flex-Algorithm as described in Section 10 and Section 12 of the [I-D.ietf-lsr-flex-algo]. Participation for the IP Flex-Algorithm is signalled as described in Section 5 and is specific to the IP Flex-Algorithm application. @@ -577,92 +642,131 @@ 10. Protection In many networks where IGP Flexible Algorithms are deployed, IGP restoration will be fast and additional protection mechanisms will not be required. IGP restoration may be enhanced by Equal Cost Multipath (ECMP). In other networks, operators can deploy additional protection mechanisms. The following are examples: - o Loop Free Alternates (LFA) [RFC5286] + * Loop Free Alternates (LFA) [RFC5286] - o Remote Loop Free Alternates (R-LFA) [RFC7490] + * Remote Loop Free Alternates (R-LFA) [RFC7490] LFA and R-LFA computations MUST be restricted to the flex-algo topology and the computed backup nexthops should be programmed for the IP flex-algo prefixes. 11. IANA Considerations This specification updates the OSPF Router Information (RI) TLVs Registry as follows: - +-------+------------------+---------------------------+ + +=======+==================+===========================+ | Value | TLV Name | Reference | - +-------+------------------+---------------------------+ + +=======+==================+===========================+ | TBD | IP Algorithm TLV | This Document Section 5.2 | +-------+------------------+---------------------------+ + Table 1 + This document also updates the "Sub-TLVs for TLV 242" registry as follows: - +-------+----------------------+---------------------------+ + +=======+======================+===========================+ | Value | TLV Name | Reference | - +-------+----------------------+---------------------------+ + +=======+======================+===========================+ | 29 | IP Algorithm Sub-TLV | This Document Section 5.1 | +-------+----------------------+---------------------------+ + Table 2 + This document also updates the "ISIS TLV Codepoints Registry" registry as follows: - +-------+------------------+-----+-----+-----+-------+--------------+ + +=======+==================+=====+=====+=====+=======+=============+ | Value | TLV Name | IIH | LSP | SNP | Purge | Reference | - +-------+------------------+-----+-----+-----+-------+--------------+ + +=======+==================+=====+=====+=====+=======+=============+ | 126 | IPv4 Algorithm | N | Y | N | N | This | | | Prefix | | | | | document, | | | Reachability TLV | | | | | Section 6.1 | + +-------+------------------+-----+-----+-----+-------+-------------+ | 127 | IPv6 Algorithm | N | Y | N | N | This | | | Prefix | | | | | document, | | | Reachability TLV | | | | | Section 6.2 | - +-------+------------------+-----+-----+-----+-------+--------------+ + +-------+------------------+-----+-----+-----+-------+-------------+ - This document updates the "OSPFv2 Extended Prefix Opaque LSA TLVs" - registry as follows:: + Table 3 - +-------+----------------------------------+------------------------+ + This document updates the "OSPFv2 Extended Prefix TLV Sub-TLVs" + registry as follows: + + +=======+=========================+================+ | Value | TLV Name | Reference | - +-------+----------------------------------+------------------------+ - | TBD | OSPFv2 Algorithm Prefix | This Document, | - | | Reachability TLV | Section 6.1 | - +-------+----------------------------------+------------------------+ + +=======+=========================+================+ + | TBD | OSPFv2 IP Algorithm | This Document, | + | | Prefix Reachability TLV | Section 6.3 | + +-------+-------------------------+----------------+ + + Table 4 + + This document updates the "OSPFv3 Extended-LSA Sub-TLVs" registry as + follows: + + +=======+==============================+================+ + | Value | TLV Name | Reference | + +=======+==============================+================+ + | TBD | OSPFv3 IP Algorithm Prefix | This Document, | + | | Reachability Sub-TLV | Section 6.4 | + +-------+------------------------------+----------------+ + | TBD | OSPFv3 IP Flexible Algorithm | This Document, | + | | ASBR Metric Sub-TLV | Section 6.5 | + +-------+------------------------------+----------------+ + + Table 5 + + This document updates the "OSPFv2 Extended Inter-Area ASBR Sub-TLVs" + registry as follows: + + +=======+============================+================+ + | Value | TLV Name | Reference | + +=======+============================+================+ + | 2 | OSPF IP Flexible Algorithm | This Document, | + | | ASBR Metric Sub-TLV | Section 6.5 | + +-------+----------------------------+----------------+ + + Table 6 12. Security Considerations This document inherits security considerations from [I-D.ietf-lsr-flex-algo]. 13. Acknowledgements Thanks to Bruno Decraene for his contributions to this document. + Special thanks to Petr Bonbon Adamec of Cesnet for supporting + interoperability testing. 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-15 (work in progress), April 2021. + A. Gulko, "IGP Flexible Algorithm", Work in Progress, + Internet-Draft, draft-ietf-lsr-flex-algo-18, 25 October + 2021, . - [ISO10589] - IANA, "Intermediate system to Intermediate system routing + [ISO10589] IANA, "Intermediate system to Intermediate system routing information exchange protocol for use in conjunction with the Protocol for providing the Connectionless-mode Network Service (ISO 8473)", August 1987, . [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, DOI 10.17487/RFC0791, September 1981, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, @@ -705,94 +809,108 @@ [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, . [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, . [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", STD 86, RFC 8200, DOI 10.17487/RFC8200, July 2017, . -14.2. Informative References + [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, . - [I-D.ietf-spring-srv6-network-programming] - Filsfils, C., Garvia, P. C., Leddy, J., Voyer, D., - Matsushima, S., and Z. Li, "Segment Routing over IPv6 - (SRv6) Network Programming", draft-ietf-spring-srv6- - network-programming-28 (work in progress), December 2020. +14.2. Informative References - [IANA-ALG] - IANA, "Sub-TLVs for TLV 242 (IS-IS Router CAPABILITY + [IANA-ALG] IANA, "Sub-TLVs for TLV 242 (IS-IS Router CAPABILITY TLV)", August 1987, . [RFC5286] Atlas, A., Ed. and A. Zinin, Ed., "Basic Specification for IP Fast Reroute: Loop-Free Alternates", RFC 5286, DOI 10.17487/RFC5286, September 2008, . [RFC7490] Bryant, S., Filsfils, C., Previdi, S., Shand, M., and N. So, "Remote Loop-Free Alternate (LFA) Fast Reroute (FRR)", RFC 7490, DOI 10.17487/RFC7490, April 2015, . [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, . + [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, + . + Authors' Addresses + William Britto Juniper Networks Elnath-Exora Business Park Survey - Bangalore, Karnataka 560103 + Bangalore 560103 + Karnataka India Email: bwilliam@juniper.net Shraddha Hegde Juniper Networks Elnath-Exora Business Park Survey - Bangalore, Karnataka 560103 + Bangalore 560103 + Karnataka India Email: shraddha@juniper.net Parag Kaneriya Juniper Networks Elnath-Exora Business Park Survey - Bangalore, Karnataka 560103 + Bangalore 560103 + Karnataka India Email: pkaneria@juniper.net - Rejesh Shetty Juniper Networks Elnath-Exora Business Park Survey - Bangalore, Karnataka 560103 + Bangalore 560103 + Karnataka India Email: mrajesh@juniper.net Ron Bonica Juniper Networks 2251 Corporate Park Drive Herndon, Virginia 20171 - USA + United States of America Email: rbonica@juniper.net + Peter Psenak Cisco Systems Apollo Business Center - Mlynske nivy 43, Bratislava 82109 + 82109 Mlynske nivy 43 Slovakia Email: ppsenak@cisco.com