--- 1/draft-ietf-lsr-ospf-prefix-originator-02.txt 2019-08-26 20:16:45.460539037 -0700 +++ 2/draft-ietf-lsr-ospf-prefix-originator-03.txt 2019-08-26 20:16:45.500540046 -0700 @@ -1,24 +1,24 @@ LSR Working Group A. Wang Internet-Draft China Telecom Intended status: Standards Track A. Lindem -Expires: February 26, 2020 Cisco Systems +Expires: February 28, 2020 Cisco Systems J. Dong Huawei Technologies - K. Talaulikar P. Psenak + K. Talaulikar Cisco Systems - August 25, 2019 + August 27, 2019 OSPF Extension for Prefix Originator - draft-ietf-lsr-ospf-prefix-originator-02 + draft-ietf-lsr-ospf-prefix-originator-03 Abstract This document describes Open Shortest Path First (OSPF) v2 and OSPFv3 encodings to advertise the router-id of the originator of inter-area prefixes for OSPFv2 and OSPFv3 Link-State Advertisement (LSA), which are needed in several use cases in multi-area OSPF use cases. Status of This Memo @@ -28,21 +28,21 @@ Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." - This Internet-Draft will expire on February 26, 2020. + This Internet-Draft will expire on February 28, 2020. Copyright Notice Copyright (c) 2019 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 @@ -55,73 +55,73 @@ Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Conventions used in this document . . . . . . . . . . . . . . 3 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 4. Conventions used in this document . . . . . . . . . . . . . . 4 5. Scenario Description . . . . . . . . . . . . . . . . . . . . 4 6. Prefix Source Router-ID sub-TLV . . . . . . . . . . . . . . . 5 7. Extended LSA Elements of Procedure . . . . . . . . . . . . . 6 8. Security Considerations . . . . . . . . . . . . . . . . . . . 6 - 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 + 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 10. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 7 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 11.1. Normative References . . . . . . . . . . . . . . . . . . 7 11.2. Informative References . . . . . . . . . . . . . . . . . 8 - Appendix A. Inter-Area Topology Retrieval Process . . . . . . . 8 + Appendix A. Inter-Area Topology Retrieval Process . . . . . . . 9 Appendix B. Special Considerations on Inter-Area Topology Retrieval . . . . . . . . . . . . . . . . . . . . . 9 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 1. Introduction [I-D.ietf-ospf-mpls-elc] defines mechanisms to Entropy Readable Label Depth (ERLD) for ingress Label Switching Router (LSR) to discover each LSR's capability of performing Entropy Label (EL) -based load- balancing in Multi Protocol Label Switch (MPLS) networks. The ingress LSR can use this information to push the appropriate label stack for specific traffic, especially in segment routing environments and other stacked LSPs scenarios. However, in inter-area scenarios, the Area Border Router (ABR) does not advertise the originating OSPF router-id for inter-area prefixes. An OSPF router in one area doesn't know where the prefixes really came from and can't determine the router that originated inter-area prefixes and then can't judge the ERLD capabilities of the destination. It is necessary to transfer the originator information of these inter-area prefixes to ensure the ingress LSR constructs the - right Label stack. + right label stack. - More generally, draft [RFC8476] defines a mechanism to advertise - multiple types of supported Maximum SID Depths (MSD) at node and/or - link granularity. This information will be referred when the head- - end router starts to send traffic to destination prefixes. In inter- - area scenario, it is also necessary for the sender to learn the + More generally, [RFC8476] defines a mechanism to advertise multiple + types of supported Maximum SID Depths (MSD) at node and/or link + granularity. This information will be referred when the head-end + router starts to send traffic to destination prefixes. In inter-area + scenario, it is also necessary for the sender to learn the capabilities of the receivers associated with the inter-area prefixes. There is also another scenario where knowing the originator of inter- area prefixes is useful. For example, Border Gateway Protocol Link- State (BGP-LS) [RFC7752] describes mechanisms using the BGP protocol - to advertise Link-State information. This can enable an Soft + to advertise Link-State information. This can enable an Software Definition Network (SDN) controller to collect the underlay network topology automatically. But if the underlay network is divided into multiple areas and running the OSPF protocol, it is not easy for the SDN controller to rebuild the multi-area topology, because normally an ABR that connects multiple areas will hide the detailed topology information - for these non-backbone areas. If only the router in backbone area - runs the BGP-LS protocol, it just learn and report the summary - network information from the non-backbone areas. If the SDN + for these non-backbone areas. If only the internal routers within + backbone area run the BGP-LS protocol, they just learn and report the + summary network information from the non-backbone areas. If the SDN controller can learn the originator of the inter-area prefixes, it is - possible for them to rebuild the inter-area topology automatically. + possible to rebuild the inter-area topology automatically. [RFC7794] introduces the Intermediate System to Intermediate System (IS-IS) "IPv4/IPv6 Source Router IDs" Type-Length-Value (TLV) to advertise the source of the prefixes redistributed from a different IS-IS level. This TLV can be used in the above scenarios. Such solution can also be applied in networks that run the OSPF protocol, but the related LSAs TLV must be extended. This draft provides such solution for the OSPFv2 and OSPFv3 protocols. @@ -140,24 +140,28 @@ o ERLD: Entropy Readable Label Depth o EL: Entropy Label o IS-IS: Intermediate System to Intermediate System o LSA: Link-State Advertisement o MSD: Maximum SID Depths + o NLRI: Network Layer Reachability Information + o OSPF: Open Shortest Path First o SID: Segment IDentifier + o SDN: Software Definition Network + 4. 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] . 5. Scenario Description Figure 1 illustrates the topology scenario when OSPF is running in multi-area. R0-R4 are routers in backbone area, S1-S4,T1-T4 are @@ -223,29 +227,28 @@ +---------------------------------------------------------------+ Figure 2: Prefix Source Router-ID sub-TLV Format o Source Router-ID Sub-TLV Type: TBD1[RFC7684] or TBD2 [RFC8362] o Length: 4 o Value: Router-ID of OSPFv2/OSPFv3 source router For OSPFv2, this sub-TLV is a sub-TLV of OSPFv2 Extended Prefix TLV, - which is included in the "OSPFv2 Extended Prefix Opaque LSA" - [RFC7684]. + which SHOULD be included in the "OSPFv2 Extended Prefix Opaque LSA" . For OSPFv3, this sub-TLV is a sub-TLV of "Inter-Area-Prefix TLV", - which is included in the "E-Inter-Area-Prefix-LSA". + which SHOULD be included in the "E-Inter-Area-Prefix-LSA". 7. Extended LSA Elements of Procedure - When an ABR, for example R2 in Fig.1, receives the Router-LSA + When an ABR, for example R2 in Figure 1, receives the Router-LSA announcement in area 2, it should originate the corresponding "OSPFv2 Extended Prefix Opaque LSA" for OSPFv2 or "E-Inter-Area-Prefix-LSA" for OSPFv3 that includes the Source Router-ID sub-TLV for the network prefixes, e.g., for prefix Lt1, N2. etc., which identifies the source router that advertised the prefix. When S1 in another area receives such LSA, it then can learn that prefix Lt1 is associated with node T1, check the ERLD, or MSD value according to its necessity, and construct the right label stack at the ingress node S1 for the traffic destined to Lt1. @@ -254,51 +257,51 @@ includes it in the prefix information advertised to an SDN controller as described in[I-D.ietf-idr-bgp-ls-segment-routing-ext]. The SDN controller can then use such information to build the inter-area topology according to the process described in the Appendix A. The topology retrieval process may not suitable for some environments as stated in Appendix B. 8. Security Considerations Security concerns for OSPF are addressed in [RFC5709] - Advertisement of the additional information defined in this document introduces no new security concerns 9. IANA Considerations This specification defines one Prefix Source Router-ID sub-TLV as described in Section 6. This value should be added to the existing - OSPFv2 Extended Prefix TLV Sub-TLVs registry and OSPFv3 Extended-LSA - Sub-TLVs registry respectively. + "OSPFv2 Extended Prefix TLV Sub-TLVs" registry and "OSPFv3 Extended- + LSA Sub-TLVs registry" respectively. - Th following new sub-TLV is added to the registry of "OSPFv2 Extended - Prefix TLV Sub-TLVs". The allocation policy is IETF Review that - defined in [RFC7684] + The following new sub-TLV is added to the registry of "OSPFv2 + Extended Prefix TLV Sub-TLVs". The allocation policy is IETF Review + that defined in [RFC7684] +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++++++++ | Code Point | Description | Status | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++++++++ | TBD | Prefix Source Sub-TLV | Allocation from IANA | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++++++++ -Figure 3: Prefix Source sub-TLV CodePoint from OSPFv2 Extended Prefix TLV Sub-TLVs - The following sub-TLV is added to the registry of "OSPFv3 Extended- - LSA Sub-TLVs". The allocation is IETF Review that defined in - [RFC8362] +Figure 3: CodePoint in "OSPFv2 Extended Prefix TLV Sub-TLVs" + + The following new sub-TLV is added to the registry of "OSPFv3 + Extended-LSA Sub-TLVs". The allocation policy is IETF Review that + defined in [RFC8362] +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++++++++ | Code Point | Description | Status | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++++++++ | TBD | Prefix Source Sub-TLV | Allocation from IANA | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++++++++ -Figure 4: Prefix Source sub-TLV CodePoint from OSPFv3 Extended-LSA Sub-TLVs +Figure 4: CodePoint in "OSPFv3 Extended-LSA Sub-TLVs" 10. Acknowledgement Many thanks to Les Ginsberg for his valuable suggestions on this draft. And also thanks Jeff Tantsura,Rob Shakir, Van De Velde Gunter, Goethals Dirk, Shaofu Peng, John E Drake for their valuable comments on this draft. 11. References @@ -350,25 +353,26 @@ [I-D.ietf-ospf-mpls-elc] Xu, X., Kini, S., Psenak, P., Filsfils, C., and S. Litkowski, "Signaling Entropy Label Capability and Entropy Readable Label-stack Depth Using OSPF", draft-ietf-ospf- mpls-elc-08 (work in progress), May 2019. Appendix A. Inter-Area Topology Retrieval Process When an IP SDN Controller receives this information, it should - compare the prefix NLRI that included in the BGP-LS packet. When it - encounters the same prefix but with different source router ID, it - should extract the corresponding area-ID, rebuild the link between - these two different source routers in non-backbone area. Belows is - one example that based on the Fig.1: + compare the prefix Network Layer Reachability Information (NLRI) that + included in the BGP-LS packet. When it encounters the same prefix + but with different source router ID, it should extract the + corresponding area-ID, rebuild the link between these two different + source routers in non-backbone area. Belows is one example that + based on the Figure 1: Assuming we want to rebuild the connection between router S1 and router S2 that locates in area 1: a. Normally, router S1 will advertise prefix N1 within its router- LSA. b. When this router-LSA reaches the ABR router R1, it will convert it into summary-LSA, add the Prefix Source Router-ID sub-TLV, which is router id of S1 in this example. @@ -377,35 +381,35 @@ BGP-LS protocol with IP SDN Controller. The controller then knows the prefixes of N1 is from S1. d. Router S2 will do the similar process, and the controller will also learn that prefixes N1 is also from S2. e. Then it can reconstruct the link between S1 and S2, using the prefix N1. The topology within Area 1 can then be reconstructed accordingly. - Iterating the above process continuously, an IP SDN controller can + Iterating the above process continuously, the IP SDN controller can retrieve a detailed topology that spans multiple areas. Appendix B. Special Considerations on Inter-Area Topology Retrieval The above topology retrieval process can be applied in the case where each link between routers is assigned a unique prefix. However, there are some situations where this heuristic cannot be applied. Specifically, the cases where the link is unnumbered or the prefix - corresponding to the link is an anycast prefix and is not unique. + corresponding to the link is an anycast prefix. The Appendix A heuristic to rebuild the topology can normally be used - if all links are numbered and the anycast prefixes correspond to - loopbacks and have a host prefix length, i.e., 32 for IPv4 prefixes - and 128 for IPv6 prefixes. + if all links are numbered. For anycast prefixes, if it corresponds + to the loopback interface and has a host prefix length, i.e., 32 for + IPv4 prefixes and 128 for IPv6 prefixes, Appendix A can also apply. Authors' Addresses Aijun Wang China Telecom Beiqijia Town, Changping District Beijing 102209 China Email: wangaj3@chinatelecom.cn @@ -410,32 +414,33 @@ Email: wangaj3@chinatelecom.cn Acee Lindem Cisco Systems 301 Midenhall Way Cary, NC 27513 USA Email: acee@cisco.com + Jie Dong Huawei Technologies Beijing China Email: jie.dong@huawei.com - Ketan Talaulikar - Cisco Systems - S.No. 154/6, Phase I, Hinjawadi - Pune 411 057 - India - - Email: ketant@cisco.com - Peter Psenak Cisco Systems Pribinova Street 10 Bratislava, Eurovea Centre, Central 3 81109 Slovakia Email: ppsenak@cisco.com + + Ketan Talaulikar + Cisco Systems + S.No. 154/6, Phase I, Hinjawadi + Pune 411 057 + India + + Email: ketant@cisco.com