LSR Working Group A. Wang Internet-Draft China Telecom Intended status: Standards Track Z. Hu Expires: March 26, 2022 Huawei Technologies G. Mishra Verizon Inc. A. Lindem Cisco Systems J. Sun ZTE Corporation September 22, 2021 Advertisement of Stub Link Attributes draft-wang-lsr-stub-link-attributes-01 Abstract This document describes the mechanism that can be used to differentiate the stub links from the normal interfaces within ISIS or OSPF domain. 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 March 26, 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 Wang, et al. Expires March 26, 2022 [Page 1] Internet-Draft PIA September 2021 carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Conventions used in this document . . . . . . . . . . . . . . 3 3. Consideration for Identifying Stub Link . . . . . . . . . . . 3 4. Protocol Extension for Stub Link Attributes . . . . . . . . . 3 4.1. OSPF Stub-Link TLV . . . . . . . . . . . . . . . . . . . 4 4.2. ISIS Stub-link Sub-TLV . . . . . . . . . . . . . . . . . 5 5. Security Considerations . . . . . . . . . . . . . . . . . . . 6 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 7. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 6 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 8.1. Normative References . . . . . . . . . . . . . . . . . . 7 8.2. Informative References . . . . . . . . . . . . . . . . . 7 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 1. Introduction Stub links are used commonly within an operators enterprise or service provider networks. One of the most common use cases for stub links is in a data center Layer 2 and Layer 3 Top of Rack(TOR) switch where the inter connected links between the TOR switches and uplinks to the core switch are only a few links and a majority of the links are Layer 3 VLAN switched virtual interface trunked between the TOR switches serving Layer 2 broadcast domains. In this scenario all the VLANs are made as stub links as it is recommended to limit the number of network LSAs between routers and switches to avoid unnecessary hello processing overhead. Another common use case is an inter-AS routing scenario where the same routing protocol but different IGP instance is running between the adjacent BGP domains. Using stub link on the inter-AS connections can ensure that prefixes contained within a domain are only reachable within the domain itself and not allow the link state database to be merged between domain which could result in undesirable consequences. For operator which runs different IGP domains that interconnect with each other via the stub links, there is desire to obtain the inter-AS topology information as described in [I-D.ietf-idr-bgpls-inter-as-topology-ext]. If the router that runs BGP-LS within one IGP domain can distinguish stub links from other Wang, et al. Expires March 26, 2022 [Page 2] Internet-Draft PIA September 2021 normal interfaces, it is then easy for the router to report these stub links using BGP-LS to a centralized PCE controller. Draft [I-D.dunbar-lsr-5g-edge-compute] describes the case that edge compute server attach the network and needs to flood some performance index information to the network to facilitate the network select the optimized application resource. The edge compute server will also not run IGP protocol. And, stub links are normally the boundary of one IGP domain, knowing them can facilitate the operators to apply various policies on such interfaces, for example, to secure their networks, or filtering the incoming traffic with scrutiny. But OSPF and ISIS have no position to identify such stub links and their associated attributes now. This document defines the protocol extension for OSPFv2/v3 and ISIS to indicate the stub links and their associated attributes. 2. Conventions used in this document The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119] . 3. Consideration for Identifying Stub Link OSPF[RFC5392] defines the Inter-AS-TE-v2 LSA and Inter-AS-TE-v3 LSA to carry the TE information about inter-AS links. These LSAs can be used to transfer the information about the stub link which is located at the boundary of one AS. This document defines the Stub-Link TLV within these LSAs to identify the stub link and transfer the associated attributes then. ISIS[RFC5316] defines the Inter-AS Reachability TLV to carry the TE information about inter-AS links. This TLV can be used to transfer the information about the stub link which is located at the boundary of one AS. This document defines the Stub-Link sub-TLV within this TLV to identify the stub link and transfer the associated attributes. 4. Protocol Extension for Stub Link Attributes The following sections define the protocol extension to indicate the stub link and its associated attributes in OSPFv2/v3 and ISIS. Wang, et al. Expires March 26, 2022 [Page 3] Internet-Draft PIA September 2021 4.1. OSPF Stub-Link TLV This document defines the OSPF Stub-Link TLV to describe stub link of a single router. This Stub-Link TLV is only applicable to the Inter- AS-TE-v2 LSA and Inter-AS-TE-v3 LSA. Inclusion in other LSA MUST be ignored. The OSPF Stub-Link TLV which is under the IANA codepoint "Top Level Types in TE LSAs" 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(Stub-Link) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Link Type | Prefix Length | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Link Prefix(variable) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sub-TLVs (variable) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: OSPF Stub-Link TLV Type: The TLV type. The value is 7(TBD) for OSPF Stub-Link Length: Variable, dependent on sub-TLVs Link Type: Define the type of the stub-link. This document defines the followings type: o 0: Reserved o 1: AS boundary link o 2: Loopback link o 3: Vlan interface link o 4-255: For future extension Prefix Length: The length of the interface address, in octet. Link Prefix: The prefix of the stub-link. It's length is determined by the field "Prefix Length". Sub-TLVs: Existing sub-TLV that defined within "Open Shortest Path First (OSPF) Traffic Engineering TLVs" for TE Link TLV(Value 2) can be included if necessary. Wang, et al. Expires March 26, 2022 [Page 4] Internet-Draft PIA September 2021 If this TLV is advertised multiple times in the same Inter-AS-TE-v2/ v3 LSA, only the first instance of the TLV is used by receiving OSPFv2/v3 routers. This situation SHOULD be logged as an error. If this TLV is advertised multiple times for the same link in different Inter-AS-TE-v2/v3 LSA originated by the same OSPFrouter, the OSPFStub-Link TLV in these LSAs with the smallest Opaque ID is used by receiving OSPFrouters. This situation may be logged as a warning. It is RECOMMENDED that OSPF routers advertising OSPF Stub-Link TLVs in different OSPF Inter-AS-TE v2/v3 LSAs re-originate these LSAs in ascending order of Opaque ID to minimize the disruption. This document creates a registry for Stub-Link attributes in Section 6. 4.2. ISIS Stub-link Sub-TLV This document defines the ISIS Stub-Link sub-TLV to describes stub link of a single router. This Stub-Link sub-TLV is only applicable to the Inter-AS Reachability TLV. Inclusion in other TLV MUST be ignored. The ISIS Stub-Link sub-TLV which is under the IANA codepoint "Sub- TLVs for TLVs 22, 23, 25, 141, 222, and 223" 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(Stub-Link) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Link Type | Prefix Length | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Link Prefix(variable) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sub-TLVs(Variable) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: ISIS Stub-Link Sub-TLV Type: ISIS sub-TLV codepoint. Value is 45(TBD) for stub-link TLV. Length: Variable, dependent on sub-TLVs Link Type: Define the type of the stub-link. This document defines the followings type: Wang, et al. Expires March 26, 2022 [Page 5] Internet-Draft PIA September 2021 o 0: Reserved o 1: AS boundary link o 2: Loopback link o 3: Vlan interface link o 4-255: For future extension Prefix Length: The length of the interface address, in octet. Link Prefix: The prefix of the stub-link. It's length is determined by the field "Prefix Length". Sub-TLVs: Existing sub-TLVs that defined within "Sub-TLVs for TLVs 22, 23, 25, 141, 222, and 223" can be included if necessary. 5. Security Considerations Security concerns for ISIS are addressed in [RFC5304] and[RFC5310] Security concern for OSPFv3 is addressed in [RFC4552] Advertisement of the additional information defined in this document introduces no new security concerns. 6. IANA Considerations IANA is requested to the allocation in following registries: +===========================+======+===========================+ | Registry | Type | Meaning | +===========================+======+===========================+ |Top Level Types in TE LSAs | 7 |OSPF Stub-Link TLV | +---------------------------+------+---------------------------+ |Sub-TLVs for TLVs 22, 23, | | | | 25, 141, 222, and 223 | 45 |IS-IS Stub-Link sub-TLV | +---------------------------+------+---------------------------+ Figure 3: IANA Allocation for newly defined TLVs 7. Acknowledgement Thanks Shunwan Zhang, Tony Li, Les Ginsberg, Acee Lindem, Dhruv Dhody, Jeff Tantsura and Robert Raszuk for their suggestions and comments on this idea. Wang, et al. Expires March 26, 2022 [Page 6] Internet-Draft PIA September 2021 8. References 8.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC4552] Gupta, M. and N. Melam, "Authentication/Confidentiality for OSPFv3", RFC 4552, DOI 10.17487/RFC4552, June 2006, . [RFC5304] Li, T. and R. Atkinson, "IS-IS Cryptographic Authentication", RFC 5304, DOI 10.17487/RFC5304, October 2008, . [RFC5310] Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R., and M. Fanto, "IS-IS Generic Cryptographic Authentication", RFC 5310, DOI 10.17487/RFC5310, February 2009, . [RFC5316] Chen, M., Zhang, R., and X. Duan, "ISIS Extensions in Support of Inter-Autonomous System (AS) MPLS and GMPLS Traffic Engineering", RFC 5316, DOI 10.17487/RFC5316, December 2008, . [RFC5392] Chen, M., Zhang, R., and X. Duan, "OSPF Extensions in Support of Inter-Autonomous System (AS) MPLS and GMPLS Traffic Engineering", RFC 5392, DOI 10.17487/RFC5392, January 2009, . 8.2. Informative References [I-D.dunbar-lsr-5g-edge-compute] Dunbar, L., Chen, H., and C. Telecom, "IS-IS & OSPF extension for 5G Edge Computing Service", draft-dunbar- lsr-5g-edge-compute-00 (work in progress), July 2021. [I-D.ietf-idr-bgpls-inter-as-topology-ext] Wang, A., Chen, H., Talaulikar, K., and S. Zhuang, "BGP-LS Extension for Inter-AS Topology Retrieval", draft-ietf- idr-bgpls-inter-as-topology-ext-09 (work in progress), September 2020. Wang, et al. Expires March 26, 2022 [Page 7] Internet-Draft PIA September 2021 Authors' Addresses Aijun Wang China Telecom Beiqijia Town, Changping District Beijing 102209 China Email: wangaj3@chinatelecom.cn Zhibo Hu Huawei Technologies Huawei Bld., No.156 Beiqing Rd. Beijing 100095 China Email: huzhibo@huawei.com Gyan S. Mishra Verizon Inc. 13101 Columbia Pike Silver Spring MD 20904 United States of America Email: gyan.s.mishra@verizon.com Acee Lindem Cisco Systems No. 301 Midenhall Way Cary NC 27513 United States of America Email: acee@cisco.com Jinsong Sun ZTE Corporation No. 68, Ziijnhua Road Nan Jing 210012 China Email: sun.jinsong@zte.com.cn Wang, et al. Expires March 26, 2022 [Page 8]