--- 1/draft-ietf-ospf-te-link-attr-reuse-14.txt 2020-06-22 03:13:14.257031530 -0700 +++ 2/draft-ietf-ospf-te-link-attr-reuse-15.txt 2020-06-22 03:13:14.301032639 -0700 @@ -1,55 +1,55 @@ LSR Working Group P. Psenak, Ed. Internet-Draft L. Ginsberg Intended status: Standards Track Cisco Systems -Expires: December 9, 2020 W. Henderickx +Expires: December 24, 2020 W. Henderickx Nokia J. Tantsura Apstra J. Drake Juniper Networks - June 7, 2020 + June 22, 2020 - OSPF Link Traffic Engineering Attribute Reuse - draft-ietf-ospf-te-link-attr-reuse-14.txt + OSPF Application-Specific Link Attributes + draft-ietf-ospf-te-link-attr-reuse-15.txt Abstract Existing traffic engineering related link attribute advertisements have been defined and are used in RSVP-TE deployments. Since the original RSVP-TE use case was defined, additional applications (e.g., - Segment Routing Traffic Engineering, Loop Free Alternate) have been - defined which also make use of the link attribute advertisements. In - cases where multiple applications wish to make use of these link - attributes the current advertisements do not support application - specific values for a given attribute nor do they support indication - of which applications are using the advertised value for a given - link. This document introduces new link attribute advertisements in - OSPFv2 and OSPFv3 which address both of these shortcomings. + Segment Routing Policy, Loop Free Alternate) have been defined that + also make use of the link attribute advertisements. In cases where + multiple applications wish to make use of these link attributes the + current advertisements do not support application specific values for + a given attribute nor do they support indication of which + applications are using the advertised value for a given link. This + document introduces new link attribute advertisements in OSPFv2 and + OSPFv3 that address both of these shortcomings. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." - This Internet-Draft will expire on December 9, 2020. + This Internet-Draft will expire on December 24, 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 @@ -59,122 +59,122 @@ the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 4 3. Existing Advertisement of Link Attributes . . . . . . . . . . 4 4. Advertisement of Link Attributes . . . . . . . . . . . . . . 4 4.1. OSPFv2 Extended Link Opaque LSA and OSPFv3 E-Router-LSA . 4 - 5. Advertisement of Application Specific Values . . . . . . . . 5 - 6. Reused TE link attributes . . . . . . . . . . . . . . . . . . 8 - 6.1. Shared Risk Link Group (SRLG) . . . . . . . . . . . . . . 8 - 6.2. Extended Metrics . . . . . . . . . . . . . . . . . . . . 8 - 6.3. Administrative Group . . . . . . . . . . . . . . . . . . 9 + 5. Advertisement of Application-Specific Values . . . . . . . . 5 + 6. Reused TE link attributes . . . . . . . . . . . . . . . . . . 9 + 6.1. Shared Risk Link Group (SRLG) . . . . . . . . . . . . . . 9 + 6.2. Extended Metrics . . . . . . . . . . . . . . . . . . . . 9 + 6.3. Administrative Group . . . . . . . . . . . . . . . . . . 10 6.4. Traffic Engineering Metric . . . . . . . . . . . . . . . 10 - 7. Maximum Link Bandwidth . . . . . . . . . . . . . . . . . . . 10 - 8. Considerations for Extended TE Metrics . . . . . . . . . . . 10 + 7. Maximum Link Bandwidth . . . . . . . . . . . . . . . . . . . 11 + 8. Considerations for Extended TE Metrics . . . . . . . . . . . 11 9. Local Interface IPv6 Address Sub-TLV . . . . . . . . . . . . 11 - 10. Remote Interface IPv6 Address Sub-TLV . . . . . . . . . . . . 11 - 11. Attribute Advertisements and Enablement . . . . . . . . . . . 11 - 12. Deployment Considerations . . . . . . . . . . . . . . . . . . 12 - 12.1. Use of Legacy RSVP-TE LSA Advertisements . . . . . . . . 12 - 12.2. Use of Zero Length Application Identifier Bit Masks . . 13 - 12.3. Interoperability, Backwards Compatibility and Migration + 10. Remote Interface IPv6 Address Sub-TLV . . . . . . . . . . . . 12 + 11. Attribute Advertisements and Enablement . . . . . . . . . . . 12 + 12. Deployment Considerations . . . . . . . . . . . . . . . . . . 13 + 12.1. Use of Legacy RSVP-TE LSA Advertisements . . . . . . . . 13 + 12.2. Interoperability, Backwards Compatibility and Migration Concerns . . . . . . . . . . . . . . . . . . . . . . . . 14 - 12.3.1. Multiple Applications: Common Attributes with RSVP- + 12.2.1. Multiple Applications: Common Attributes with RSVP- TE . . . . . . . . . . . . . . . . . . . . . . . . . 14 - 12.3.2. Multiple Applications: Some Attributes Not Shared + 12.2.2. Multiple Applications: Some Attributes Not Shared with RSVP-TE . . . . . . . . . . . . . . . . . . . . 14 - 12.3.3. Interoperability with Legacy Routers . . . . . . . . 14 - 12.3.4. Use of Application Specific Advertisements for RSVP- + 12.2.3. Interoperability with Legacy Routers . . . . . . . . 15 + 12.2.4. Use of Application-Specific Advertisements for RSVP- TE . . . . . . . . . . . . . . . . . . . . . . . . . 15 - 13. Security Considerations . . . . . . . . . . . . . . . . . . . 15 + 13. Security Considerations . . . . . . . . . . . . . . . . . . . 16 14. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 14.1. OSPFv2 . . . . . . . . . . . . . . . . . . . . . . . . . 16 14.2. OSPFv3 . . . . . . . . . . . . . . . . . . . . . . . . . 17 + 15. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 18 16. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 18 - 17. References . . . . . . . . . . . . . . . . . . . . . . . . . 18 - 17.1. Normative References . . . . . . . . . . . . . . . . . . 18 + 17. References . . . . . . . . . . . . . . . . . . . . . . . . . 19 + 17.1. Normative References . . . . . . . . . . . . . . . . . . 19 17.2. Informative References . . . . . . . . . . . . . . . . . 20 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21 1. Introduction Advertisement of link attributes by the OSPFv2 [RFC2328] and OSPFv3 [RFC5340] protocols in support of traffic engineering (TE) was introduced by [RFC3630] and [RFC5329] respectively. It has been extended by [RFC4203], [RFC7308] and [RFC7471]. Use of these extensions has been associated with deployments supporting Traffic Engineering over Multiprotocol Label Switching (MPLS) in the presence of the Resource Reservation Protocol (RSVP) - more succinctly referred to as RSVP-TE [RFC3209]. - For the purposes of this document an application is a technology - which makes use of link attribute advertisements - examples of which - are listed in Section 5. + For the purposes of this document an application is a technology that + makes use of link attribute advertisements, examples of which are + listed in Section 5. - In recent years new applications have been introduced which have use + In recent years new applications have been introduced that have use cases for many of the link attributes historically used by RSVP-TE. - Such applications include Segment Routing Traffic Engineering (SRTE) + Such applications include Segment Routing (SR) Policy [I-D.ietf-spring-segment-routing-policy] and Loop Free Alternates (LFA) [RFC5286]. This has introduced ambiguity in that if a - deployment includes a mix of RSVP-TE support and SRTE support (for - example) it is not possible to unambiguously indicate which + deployment includes a mix of RSVP-TE support and SR Policy support + (for example) it is not possible to unambiguously indicate which advertisements are to be used by RSVP-TE and which advertisements are - to be used by SRTE. If the topologies are fully congruent this may - not be an issue, but any incongruence leads to ambiguity. + to be used by SR Policy. If the topologies are fully congruent this + may not be an issue, but any incongruence leads to ambiguity. - An example where this ambiguity causes a problem is a network in - which RSVP-TE is enabled only on a subset of its links. A link - attribute is advertised for the purpose of another application (e.g. - SRTE) for a link that is not enabled for RSV-TE. As soon as the + An example where this ambiguity causes a problem is a network in that + RSVP-TE is enabled only on a subset of its links. A link attribute + is advertised for the purpose of another application (e.g. SR + Policy) for a link that is not enabled for RSVP-TE. As soon as the router that is an RSVP-TE head-end sees the link attribute being advertised for that link, it assumes RSVP-TE is enabled on that link, even though it is not. If such RSVP-TE head-end router tries to - setup an RSVP-TE path via that link it will result in the path setup + setup an RSVP-TE path via that link, it will result in the path setup failure. An additional issue arises in cases where both applications are supported on a link but the link attribute values associated with each application differ. Current advertisements do not support - advertising application specific values for the same attribute on a + advertising application-specific values for the same attribute on a specific link. - This document defines extensions which address these issues. Also, - as evolution of use cases for link attributes can be expected to - continue in the years to come, this document defines a solution which + This document defines extensions that address these issues. Also, as + evolution of use cases for link attributes can be expected to + continue in the years to come, this document defines a solution that is easily extensible for the introduction of new applications and new use cases. 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 capitals, as shown here. 3. Existing Advertisement of Link Attributes There are existing advertisements used in support of RSVP-TE. These advertisements are carried in the OSPFv2 TE Opaque LSA [RFC3630] and OSPFv3 Intra-Area-TE-LSA [RFC5329]. Additional RSVP-TE link attributes have been defined by [RFC4203], [RFC7308] and [RFC7471]. Extended Link Opaque LSAs as defined in [RFC7684] for OSPFv2 and Extended Router-LSAs [RFC8362] for OSPFv3 are used to advertise link - attributes that are used by applications other then RSVP-TE or GMPLS. - These LSAs were defined as a generic containers for distribution of - the extended link attributes. + attributes that are used by applications other than RSVP-TE or GMPLS + [RFC4203]. These LSAs were defined as a generic containers for + distribution of the extended link attributes. 4. Advertisement of Link Attributes This section outlines the solution for advertising link attributes originally defined for RSVP-TE or GMPLS when they are used for other applications. 4.1. OSPFv2 Extended Link Opaque LSA and OSPFv3 E-Router-LSA Advantages of Extended Link Opaque LSAs as defined in [RFC7684] for @@ -182,21 +182,21 @@ advertisement of link attributes originally defined for RSVP-TE when used in packet networks and in GMPLS: 1. Advertisement of the link attributes does not make the link part of the RSVP-TE topology. It avoids any conflicts and is fully compatible with [RFC3630] and [RFC5329]. 2. The OSPFv2 TE Opaque LSA and OSPFv3 Intra-Area-TE-LSA remains truly opaque to OSPFv2 and OSPFv3 as originally defined in [RFC3630] and [RFC5329] respectively. Their contents are not - inspected by OSPF, that acts as a pure transport. + inspected by OSPF, which instead acts as a pure transport. 3. There is a clear distinction between link attributes used by RSVP-TE and link attributes used by other OSPFv2 or OSPFv3 applications. 4. All link attributes that are used by other applications are advertised in a single LSA, the Extended Link Opaque LSA in OSPFv2 or the OSPFv3 E-Router-LSA [RFC8362] in OSPFv3. The disadvantage of this approach is that in rare cases, the same @@ -213,40 +213,42 @@ TE link attributes used for RSVP-TE/GMPLS continue to use OSPFv2 TE Opaque LSA [RFC3630] and OSPFv3 Intra-Area-TE-LSA [RFC5329]. The format of the link attribute TLVs that have been defined for RSVP-TE applications will be kept unchanged even when they are used for non-RSVP-TE applications. Unique code points are allocated for these link attribute TLVs from the OSPFv2 Extended Link TLV Sub-TLV Registry [RFC7684] and from the OSPFv3 Extended-LSA Sub-TLV Registry [RFC8362], as specified in Section 14. -5. Advertisement of Application Specific Values +5. Advertisement of Application-Specific Values - To allow advertisement of the application specific values of the link - attribute, a new Application Specific Link Attributes (ASLA) sub-TLV + To allow advertisement of the application-specific values of the link + attribute, a new Application-Specific Link Attributes (ASLA) sub-TLV is defined. The ASLA sub-TLV is a sub-TLV of the OSPFv2 Extended Link TLV [RFC7684] and OSPFv3 Router-Link TLV [RFC8362]. On top of advertising the link attributes for standardized applications, link attributes can be advertised for the purpose of - application that is not defined as standardized one. We call such - application a user defined application. What such application might - be is not subject to the standardization and is outside of the scope - of this specification. + applications that are not standardized. We call such an application + a "User Defined Application" or "UDA". These applications are not + subject to standardization and are outside of the scope of this + specification. - The ASLA sub-TLV is an optional sub-TLV and can appear multiple times - in the OSPFv2 Extended Link TLV and OSPFv3 Router-Link TLV. The ASLA - sub-TLV MUST be used for advertisement of the link attributes listed - at the end on this section if these are advertised inside OSPFv2 - Extended Link TLV and OSPFv3 Router-Link TLV. It has the following - format: + The ASLA sub-TLV is an optional sub-TLV of OSPFv2 Extended Link TLV + and OSPFv3 Router-Link TLV. Multiple ASLA sub-TLVs can be present in + its parent TLV when different applications want to control different + link attributes or when different value of the same attribute needs + to be advertised by multiple applications. The ASLA sub-TLV MUST be + used for advertisement of the link attributes listed at the end on + this section if these are advertised inside OSPFv2 Extended Link TLV + and OSPFv3 Router-Link TLV. 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SABM Length | UDABM Length | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Standard Application Identifier Bit Mask | +- -+ @@ -275,69 +277,95 @@ in octets. The value MUST be 0, 4 or 8. If the User Defined Application Bit Mask is not present, the User Defined Application Bit Mask Length MUST be set to 0. Standard Application Identifier Bit Mask: Optional set of bits, where each bit represents a single standard application. Bits are defined in the Link Attribute Application Identifier Registry, which has been defined in [I-D.ietf-isis-te-app]. Current assignments are repeated here for informational purpose: + 0 1 2 3 4 5 6 7 ... + +-+-+-+-+-+-+-+-+... + |R|S|F| ... + +-+-+-+-+-+-+-+-+... + Bit-0 (R-bit): RSVP-TE - Bit-1 (S-bit): Segment Routing TE + Bit-1 (S-bit): Segment Routing Policy Bit-2 (F-bit): Loop Free Alternate (LFA). Includes all LFA types User Defined Application Identifier Bit Mask: Optional set of bits, where each bit represents a single user defined application. If the SABM or UDABM length is other than 0, 4, or 8, the ASLA sub- TLV MUST be ignored by the receiver. Standard Application Identifier Bits are defined/sent starting with - Bit 0. Undefined bits which are transmitted MUST be transmitted as 0 + Bit 0. Undefined bits that are transmitted MUST be transmitted as 0 and MUST be ignored on receipt. Bits that are not transmitted MUST be treated as if they are set to 0 on receipt. Bits that are not supported by an implementation MUST be ignored on receipt. User Defined Application Identifier Bits have no relationship to Standard Application Identifier Bits and are not managed by IANA or any other standards body. It is recommended that bits are used starting with Bit 0 so as to minimize the number of octets required - to advertise all UDAs. + to advertise all UDAs. Undefined bits which are transmitted MUST be + transmitted as 0 and MUST be ignored on receipt. Bits that are not + transmitted MUST be treated as if they are set to 0 on receipt. Bits + that are not supported by an implementation MUST be ignored on + receipt. If the link attribute advertisement is intended to be only used by a specific set of applications, corresponding Bit Masks MUST be present - and application specific bit(s) MUST be set for all applications that + and application-specific bit(s) MUST be set for all applications that use the link attributes advertised in the ASLA sub-TLV. Application Bit Masks apply to all link attributes that support - application specific values and are advertised in the ASLA sub-TLV. + application-specific values and are advertised in the ASLA sub-TLV. The advantage of not making the Application Bit Masks part of the attribute advertisement itself is that the format of any previously defined link attributes can be kept and reused when advertising them in the ASLA sub-TLV. If the same attribute is advertised in more than single ASLA sub-TLVs with the application listed in the Application Bit Masks, the application SHOULD use the first instance of advertisement and ignore any subsequent advertisements of that attribute. + If link attributes are advertised associated with zero length + Application Identifier Bit Masks for both standard applications and + user defined applications, then any Standard Application and/or any + User Defined Application is permitted to use that set of link + attributes. If support for a new application is introduced on any + node in a network in the presence of such advertisements, these + advertisements are permitted to be used by the new application. If + this is not what is intended, then existing advertisements MUST be + readvertised with an explicit set of applications specified before a + new application is introduced. + + An application-specific advertisement (Application Identifier Bit + Mask with a matching Application Identifier Bit set) for an attribute + MUST always be preferred over the advertisement of the same attribute + with the zero length Application Identifier Bit Masks for both + standard applications and user defined applications on the same link. + This document defines the initial set of link attributes that MUST use the ASLA sub-TLV if advertised in the OSPFv2 Extended Link TLV or in the OSPFv3 Router-Link TLV. Documents which define new link - attributes MUST state whether the new attributes support application - specific values and as such MUST be advertised in an ASLA sub-TLV. - The link attributes that MUST be advertised in ASLA sub-TLVs are: + attributes MUST state whether the new attributes support application- + specific values and as such are advertised in an ASLA sub-TLV. The + standard link attributes that are advertised in ASLA sub-TLVs are: - Shared Risk Link Group [RFC4203] - Unidirectional Link Delay [RFC7471] - Min/Max Unidirectional Link Delay [RFC7471] - Unidirectional Delay Variation [RFC7471] - Unidirectional Link Loss [RFC7471] @@ -356,35 +383,35 @@ 6. Reused TE link attributes This section defines the use case and indicates the code points (Section 14) from the OSPFv2 Extended Link TLV Sub-TLV Registry and OSPFv3 Extended-LSA Sub-TLV Registry for some of the link attributes that have been originally defined for RSVP-TE or GMPLS. 6.1. Shared Risk Link Group (SRLG) - The SRLG of a link can be used in OSPF calculated IPFRR [RFC5714] to - compute a backup path that does not share any SRLG group with the - protected link. + The SRLG of a link can be used in OSPF calculated IPFRR (IP Fast + Reroute) [RFC5714] to compute a backup path that does not share any + SRLG group with the protected link. To advertise the SRLG of the link in the OSPFv2 Extended Link TLV, the same format for the sub-TLV defined in section 1.3 of [RFC4203] is used and TLV type 11 is used. Similarly, for OSPFv3 to advertise the SRLG in the OSPFv3 Router-Link TLV, TLV type 12 is used. 6.2. Extended Metrics [RFC3630] defines several link bandwidth types. [RFC7471] defines extended link metrics that are based on link bandwidth, delay and - loss characteristics. All these can be used to compute primary and - backup paths within an OSPF area to satisfy requirements for + loss characteristics. All of these can be used to compute primary + and backup paths within an OSPF area to satisfy requirements for bandwidth, delay (nominal or worst case) or loss. To advertise extended link metrics in the OSPFv2 Extended Link TLV, the same format for the sub-TLVs defined in [RFC7471] is used with the following TLV types: 12 - Unidirectional Link Delay 13 - Min/Max Unidirectional Link Delay @@ -501,205 +528,189 @@ advertised in the ASLA sub-TLV. Instead, it MAY be advertised as a sub-TLV of the OSPFv3 E-Router-LSA Router-Link TLV [RFC8362]. To advertise the Remote Interface IPv6 Address Sub-TLV in the OSPFv3 Router-Link TLV, the same format for sub-TLV defined in [RFC5329] is used with TLV type 25. 11. Attribute Advertisements and Enablement This document defines extensions to support the advertisement of - application specific link attributes. + application-specific link attributes. There are applications where the application enablement on the link - is relevant - e.g. RSVP-TE - one need to make sure that RSVP is + is relevant - e.g., RSVP-TE - one needs to make sure that RSVP is enabled on the link before sending a RSVP-TE signaling message over it. - There are applications, where the enablement of the application on - the link is irrelevant and has nothing to do with the fact that some - link attributes are advertised for the purpose of such application - - e.g. LFA. + There are applications where the enablement of the application on the + link is irrelevant and has nothing to do with the fact that some link + attributes are advertised for the purpose of such application. An + example of this is LFA. Whether the presence of link attribute advertisements for a given application indicates that the application is enabled on that link depends upon the application. Similarly, whether the absence of link attribute advertisements indicates that the application is not enabled depends upon the application. - In the case of RSVP-TE, the advertisement of application specific + In the case of RSVP-TE, the advertisement of application-specific link attributes has no implication of RSVP-TE being enabled on that link. The RSVP-TE enablement is solely derived from the information carried in the OSPFv2 TE Opaque LSA [RFC3630] and OSPFv3 Intra-Area- TE-LSA [RFC5329]. - In the case of SRTE, advertisement of application specific link - attributes does not indicate enablement of SRTE. The advertisements - are only used to support constraints which may be applied when - specifying an explicit path. SRTE is implicitly enabled on all links - which are part of the Segment Routing enabled topology independent of - the existence of link attribute advertisements - - In the case of LFA, advertisement of application specific link + In the case of SR Policy, advertisement of application-specific link + attributes does not indicate enablement of SR Policy. The + advertisements are only used to support constraints that may be + applied when specifying an explicit path. SR Policy is implicitly + enabled on all links that are part of the Segment Routing enabled + topology independent of the existence of link attribute + advertisements + In the case of LFA, advertisement of application-specific link attributes does not indicate enablement of LFA on that link. Enablement is controlled by local configuration. If, in the future, additional standard applications are defined to use this mechanism, the specification defining this use MUST define - the relationship between application specific link attribute + the relationship between application-specific link attribute advertisements and enablement for that application. - This document allows the advertisement of application specific link + This document allows the advertisement of application-specific link attributes with no application identifiers i.e., both the Standard Application Identifier Bit Mask and the User Defined Application Identifier Bit Mask are not present (See Section 5). This supports the use of the link attribute by any application. In the presence of an application where the advertisement of link attribute advertisements is used to infer the enablement of an application on that link (e.g., RSVP-TE), the absence of the application identifier leaves ambiguous whether that application is enabled on such a link. This needs to be considered when making use of the "any application" encoding. 12. Deployment Considerations 12.1. Use of Legacy RSVP-TE LSA Advertisements Bit Identifiers for Standard Applications are defined in Section 5. All of the identifiers defined in this document are associated with - applications which were already deployed in some networks prior to - the writing of this document. Therefore, such applications have been + applications that were already deployed in some networks prior to the + writing of this document. Therefore, such applications have been deployed using the RSVP-TE LSA advertisements. The Standard Applications defined in this document may continue to use RSVP-TE LSA advertisements for a given link so long as at least one of the following conditions is true: The application is RSVP-TE - The application is SRTE or LFA and RSVP-TE is not deployed + The application is SR Policy or LFA and RSVP-TE is not deployed anywhere in the network - The application is SRTE or LFA, RSVP-TE is deployed in the - network, and both the set of links on which SRTE and/or LFA - advertisements are required and the attribute values used by SRTE - and/or LFA on all such links is fully congruent with the links and - attribute values used by RSVP-TE + The application is SR Policy or LFA, RSVP-TE is deployed in the + network, and both the set of links on which SR Policy and/or LFA + advertisements are required and the attribute values used by SR + Policy and/or LFA on all such links is fully congruent with the + links and attribute values used by RSVP-TE - Under the conditions defined above, implementations which support the + Under the conditions defined above, implementations that support the extensions defined in this document have the choice of using RSVP-TE - LSA advertisements or application specific advertisements in support - of SRTE and/or LFA. This will require implementations to provide - controls specifying which type of advertisements are to be sent/ - processed on receive for these applications. Further discussion of - the associated issues can be found in Section 12.3. + LSA advertisements or application-specific advertisements in support + of SR Policy and/or LFA. This will require implementations to + provide controls specifying which type of advertisements are to be + sent/ processed on receive for these applications. Further + discussion of the associated issues can be found in Section 12.2. - New applications which future documents define to make use of the + New applications that future documents define to make use of the advertisements defined in this document MUST NOT make use of RSVP-TE LSA advertisements. This simplifies deployment of new applications by eliminating the need to support multiple ways to advertise attributes for the new applications. -12.2. Use of Zero Length Application Identifier Bit Masks - - If link attributes are advertised associated with zero length - Application Identifier Bit Masks for both standard applications and - user defined applications, then any Standard Application and/or any - User Defined Application is permitted to use that set of link - attributes so long as there is not another set of attributes - advertised on that same link which is associated with a non-zero - length Application Identifier Bit Mask with a matching Application - Identifier Bit set. If support for a new application is introduced - on any node in a network in the presence of such advertisements, - these advertisements are permitted to be used by the new application. - If this is not what is intended, then existing advertisements MUST be - readvertised with an explicit set of applications specified before a - new application is introduced. - -12.3. Interoperability, Backwards Compatibility and Migration Concerns +12.2. Interoperability, Backwards Compatibility and Migration Concerns - Existing deployments of RSVP-TE, SRTE, and/or LFA utilize the legacy - advertisements listed in Section 3. Routers which do not support the - extensions defined in this document will only process legacy - advertisements and are likely to infer that RSVP-TE is enabled on the - links for which legacy advertisements exist. It is expected that - deployments using the legacy advertisements will persist for a + Existing deployments of RSVP-TE, SR Policy, and/or LFA utilize the + legacy advertisements listed in Section 3. Routers which do not + support the extensions defined in this document will only process + legacy advertisements and are likely to infer that RSVP-TE is enabled + on the links for which legacy advertisements exist. It is expected + that deployments using the legacy advertisements will persist for a significant period of time. Therefore deployments using the - extensions defined in this document in the presence of routers which + extensions defined in this document in the presence of routers that do not support these extensions need to be able to interoperate with the use of legacy advertisements by the legacy routers. The following sub-sections discuss interoperability and backwards compatibility concerns for a number of deployment scenarios. -12.3.1. Multiple Applications: Common Attributes with RSVP-TE +12.2.1. Multiple Applications: Common Attributes with RSVP-TE In cases where multiple applications are utilizing a given link, one of the applications is RSVP-TE, and all link attributes for a given link are common to the set of applications utilizing that link, interoperability is achieved by using legacy advertisements for RSVP- TE. Attributes for applications other than RSVP-TE MUST be - advertised using application specific advertisements. This results + advertised using application-specific advertisements. This results in duplicate advertisements for those attributes. -12.3.2. Multiple Applications: Some Attributes Not Shared with RSVP-TE +12.2.2. Multiple Applications: Some Attributes Not Shared with RSVP-TE In cases where one or more applications other than RSVP-TE are utilizing a given link and one or more link attribute values are not shared with RSVP-TE, interoperability is achieved by using legacy advertisements for RSVP-TE. Attributes for applications other than - RSVP-TE MUST be advertised using application specific advertisements. + RSVP-TE MUST be advertised using application-specific advertisements. In cases where some link attributes are shared with RSVP-TE, this requires duplicate advertisements for those attributes -12.3.3. Interoperability with Legacy Routers +12.2.3. Interoperability with Legacy Routers - For the applications defined in this document, routers which do not + For the applications defined in this document, routers that do not support the extensions defined in this document will send and receive only legacy link attribute advertisements. So long as there is any - legacy router in the network which has any of the applications + legacy router in the network that has any of the applications enabled, all routers MUST continue to advertise link attributes using legacy advertisements. In addition, the link attribute values associated with the set of applications supported by legacy routers - (RSVP-TE, SRTE, and/or LFA) are always shared since legacy routers - have no way of advertising or processing application specific values. - Once all legacy routers have been upgraded, migration from legacy - advertisements to application specific advertisements can be achieved - via the following steps: + (RSVP-TE, SR Policy, and/or LFA) are always shared since legacy + routers have no way of advertising or processing application-specific + values. Once all legacy routers have been upgraded, migration from + legacy advertisements to application specific advertisements can be + achieved via the following steps: - 1)Send new application specific advertisements while continuing to + 1)Send new application-specific advertisements while continuing to advertise using the legacy advertisement (all advertisements are then duplicated). Receiving routers continue to use legacy advertisements. - 2)Enable the use of the application specific advertisements on all + 2)Enable the use of the application-specific advertisements on all routers 3)Keep legacy advertisements if needed for RSVP-TE purposes. When the migration is complete, it then becomes possible to advertise incongruent values per application on a given link. - Documents defining new applications which make use of the application + Documents defining new applications that make use of the application- specific advertisements defined in this document MUST discuss interoperability and backwards compatibility issues that could occur - in the presence of routers which do not support the new application. + in the presence of routers that do not support the new application. -12.3.4. Use of Application Specific Advertisements for RSVP-TE +12.2.4. Use of Application-Specific Advertisements for RSVP-TE The extensions defined in this document support RSVP-TE as one of the supported applications. It is however RECOMMENDED to advertise all link-attributes for RSVP-TE in the existing OSPFv2 TE Opaque LSA [RFC3630] and OSPFv3 Intra-Area-TE-LSA [RFC5329] to maintain backward - compatibility. RSVP-TE can eventually utilize the application - specific advertisements for newly defined link attributes, which are - defined as application specific. + compatibility. RSVP-TE can eventually utilize the application- + specific advertisements for newly defined link attributes, that are + defined as application-specific. - Link attributes that are NOT allowed to be advertised in the ASLA + Link attributes that are not allowed to be advertised in the ASLA Sub-TLV, such as Maximum Reservable Link Bandwidth and Unreserved Bandwidth MUST use the OSPFv2 TE Opaque LSA [RFC3630] and OSPFv3 Intra-Area-TE-LSA [RFC5329] and MUST NOT be advertised in ASLA Sub- TLV. 13. Security Considerations Existing security extensions as described in [RFC2328], [RFC5340] and [RFC8362] apply to extensions defined in this document. While OSPF is under a single administrative domain, there can be deployments @@ -712,21 +723,22 @@ this document are detected and do not provide a vulnerability for attackers to crash the OSPF router or routing process. Reception of a malformed TLV or Sub-TLV SHOULD be counted and/or logged for further analysis. Logging of malformed TLVs and Sub-TLVs SHOULD be rate-limited to prevent a Denial of Service (DoS) attack (distributed or otherwise) from overloading the OSPF control plane. This document defines a new way to advertise link attributes. Tampering with the information defined in this document may have an effect on applications using it, including impacting Traffic - Engineering. This is similar in nature to the impacts associated + Engineering that uses various link attributes for its path + computation. This is similar in nature to the impacts associated with (for example) [RFC3630]. As the advertisements defined in this document limit the scope to specific applications, the impact of tampering is similarly limited in scope. 14. IANA Considerations This specifications updates two existing registries: - OSPFv2 Extended Link TLV Sub-TLVs Registry @@ -735,33 +747,33 @@ New values are allocated using the IETF Review procedure as described in [RFC5226]. 14.1. OSPFv2 The OSPFv2 Extended Link TLV Sub-TLVs Registry [RFC7684] defines sub- TLVs at any level of nesting for OSPFv2 Extended Link TLVs. IANA has assigned the following Sub-TLV types from the OSPFv2 Extended Link TLV Sub-TLVs Registry: - 10 - Application Specific Link Attributes + 10 - Application-Specific Link Attributes 11 - Shared Risk Link Group - 12 - Unidirectional Link Delay 13 - Min/Max Unidirectional Link Delay 14 - Unidirectional Delay Variation 15 - Unidirectional Link Loss 16 - Unidirectional Residual Bandwidth + 17 - Unidirectional Available Bandwidth 18 - Unidirectional Utilized Bandwidth 19 - Administrative Group 20 - Extended Administrative Group 22 - TE Metric @@ -767,21 +779,21 @@ 23 - Maximum Link Bandwidth 14.2. OSPFv3 The OSPFv3 Extended-LSA Sub-TLV Registry [RFC8362] defines sub-TLVs at any level of nesting for OSPFv3 Extended LSAs. IANA has assigned the following Sub-TLV types from the OSPFv3 Extended-LSA Sub-TLV Registry: - 11 - Application Specific Link Attributes + 11 - Application-Specific Link Attributes 12 - Shared Risk Link Group 13 - Unidirectional Link Delay 14 - Min/Max Unidirectional Link Delay 15 - Unidirectional Delay Variation 16 - Unidirectional Link Loss @@ -835,21 +846,21 @@ Thanks to Alvaro Retana for his detailed review and comments. 17. References 17.1. Normative References [I-D.ietf-isis-te-app] Ginsberg, L., Psenak, P., Previdi, S., Henderickx, W., and J. Drake, "IS-IS TE Attributes per application", draft- - ietf-isis-te-app-14 (work in progress), June 2020. + ietf-isis-te-app-17 (work in progress), June 2020. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, DOI 10.17487/RFC2328, April 1998, .