LSR Working Group A. Wang Internet-Draft China Telecom Intended status: Standards Track Z. Hu Expires: April 1, 2021 Huawei Technologies G. Mishra Verizon Inc. September 28, 2020 Passive Interface Attribute draft-wang-lsr-passive-interface-attribute-03 Abstract This document describes the mechanism that can be used to differentiate the passive interfaces 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 April 1, 2021. Copyright Notice Copyright (c) 2020 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of Wang, et al. Expires April 1, 2021 [Page 1] Internet-Draft PIA September 2020 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. Scenario Description . . . . . . . . . . . . . . . . . . . . 3 4. Passive Interface Attribute . . . . . . . . . . . . . . . . . 4 4.1. ISIS Passive Interface Attribute . . . . . . . . . . . . 4 4.2. OSPF Passive Interface Attribute . . . . . . . . . . . . 5 5. Security Considerations . . . . . . . . . . . . . . . . . . . 5 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 7. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 5 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 8.1. Normative References . . . . . . . . . . . . . . . . . . 6 8.2. Informative References . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 1. Introduction Passive interfaces are used commonly within an operators enterprise or service provider networks. One of the most common use cases for passive interface is in a data center Layer 2 and Layer 3 TOR(Top of Rack) switch where the inter connected link between the TOR switches and uplink to the Core switch are only a few links and a majority of the links are Layer 3 VLAN Switched Virtual Interface Default Gateways trunked betwen the TOR switches servicing Layer 2 broadcast domains. In this scenario all the VLANs are made passive 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 diffent IGP instance is running between the adjacent BGP domains. Using passive interface on the inter-as tiepoint 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, 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 is within one IGP domain and can distinguish passive interfaces from other interfaces with transit neighbor, it is then easy for the router to report these passive links using BGP-LS to centralized PCE controller. Wang, et al. Expires April 1, 2021 [Page 2] Internet-Draft PIA September 2020 But OSPF and ISIS have no capabilities to flag such passive interface. This document defines the protocol extension for OSPF and ISIS for the prefix that comes from passive interface. 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. Scenario Description Figure 1 illustrates the topology scenario when ISIS/OSPF is running in different domain. B1, B3 are border routers within IGP domain A, B2, B4 are border routers within domain B. S1-S4 are the internal routers within domain A, T1-T4 are the internal routers within domain B. The two domain are interconnected via the links between B1/B2 and B3/B4. Passive interfaces are enabled in the links between B1/B2 and B3/B4 respectively. For domain A and B, the S2/T1 router that runs ISIS/ OSPF can't extract the passives links from the normal links and report it to PCE controller via the BGP-LS protocol. They can only judge the passive interfaces from other characteristics, such as no IGP neighbor on this link. Such judgement can extract these passive links but it is not accurate, because it covers also the situation when there are some issues to establish the ISIS adjacency/OSPF neighbor but not the passive interface. For passive interfaces that are used in the edge router or switches which connects the server, for example in the router S1/S4 and T2/T4 in Figure 1, knowing these interfaces are correctly configured will also benefit the management of them. The method to label these passive interfaces explicitly is necessary then. Wang, et al. Expires April 1, 2021 [Page 3] Internet-Draft PIA September 2020 +-----------------+ +----+IP SDN Controller+----+ | +-----------------+ | | | |BGP-LS |BGP-LS | | +---------------+-----+ +-----+--------------+ | +--+ +-++ ++-+ +-++ +|-+ +--+| | |S1+--------+S2+---+B1+-----------+B2+---+T1+--------+T2|| | +-++ N1 +-++ ++-+ +-++ ++++ N2 +-++| | | | | | || | | | | | | | || | | | +-++ +-++ ++-+ +-++ ++++ +-++| | |S4+--------+S3+---+B3+-----------+B4+---+T3+--------+T4|| | +--+ +--+ ++-+ +-++ ++-+ +--+| | | | | | | | | | Domain A(ISIS) | | Domain B(OSPF) | +---------------------+ +--------------------+ Figure 1: Inter-AS Domain Scenarios 4. Passive Interface Attribute 4.1. ISIS Passive Interface Attribute [RFC7794] defines the "IPv4/IPv6 Extended Reachability Attribute Flags" sub-TLV to advertise the additional flags associated with a given prefix advertisement. We propose new bit(Bit 5 is desired) to be assigned by the IANA for the passive interface attribute, as illustrated in Figure2: 0 1 2 3 4 5 6 7 +-+-+-+-+-+-+-+-+ |X|R|N|E|A|U +-+-+-+-+-+-+-+-+ Figure 2: Prefix Attribute Flags U-flag: Unactive Flag(Bit 5) Set for local interface that is configured as passive interface. When the interfaces on one router be configured as the passive interface, the U-flag bit will be set in the "IPv4/IPv6 Extended Reachability Attribute Flags" sub-TLV. This sub-TLV will be included in the TLV 135, TLV 235, TLV 236 and TLV 237 as necessary and be flooded within the ISIS domain. Wang, et al. Expires April 1, 2021 [Page 4] Internet-Draft PIA September 2020 4.2. OSPF Passive Interface Attribute [RFC5340] defines the "Prefix Option field" in "Intra-Area-Prefix- LSAs" LSA to describe the prefix capabilities. The bits in this field can be defined to flag the prefix is coming from the passive interface. We propose new bit(Bit 1 is desired) to be assigned by the IANA for the passive interface, as illustrated in Figure 3: 0 1 2 3 4 5 6 7 +--+--+--+--+--+-+--+--+ | | | U|DN| P|x|LA|NU| +--+--+--+--+--+-+--+--+ Figure 3: The PrefixOptions Field U-flag: Unactive Flag(Bit 2) Set for local interface that is configured as passive interface. When the interfaces on one router be configured as the passive interface, the U-flag bit will be set in the "Prefix Option field" of Intra-Area-Prefix-LSAs. The router receives such advertisement can then easily distinguish the passive interfaces from the normal interface, and reports them to the PCE controller if it run the BGP-LS protocol. 5. Security Considerations Security concerns for ISIS are addressed in [RFC5304] and[RFC5310] Advertisement of the additional information defined in this document introduces no new security concerns. 6. IANA Considerations IANA is requested to allocate the U-bit (bit position 5 is desired) from the "Bit Values for Prefix Attribute Flags Sub-TLV" registry of ISIS TLV codepoint. IANA is requested to allocate the U-bit(bit position 2 is desired) from the "OSPFv3 Prefix Options" registry of OSPFv3 Parameters codepoint. 7. Acknowledgement Thanks Shunwan Zhang, Tony Li, Les Ginsberg and Robert Raszuk for their suggestions and comments on this idea. Wang, et al. Expires April 1, 2021 [Page 5] Internet-Draft PIA September 2020 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, . [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, . [RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008, . [RFC7794] Ginsberg, L., Ed., Decraene, B., Previdi, S., Xu, X., and U. Chunduri, "IS-IS Prefix Attributes for Extended IPv4 and IPv6 Reachability", RFC 7794, DOI 10.17487/RFC7794, March 2016, . 8.2. Informative References [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-08 (work in progress), April 2020. Authors' Addresses Aijun Wang China Telecom Beiqijia Town, Changping District Beijing 102209 China Email: wangaj3@chinatelecom.cn Wang, et al. Expires April 1, 2021 [Page 6] Internet-Draft PIA September 2020 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 Wang, et al. Expires April 1, 2021 [Page 7]