IDR Working Group A. Wang Internet-Draft China Telecom Intended status: Standards Track June 28, 2018 Expires: December 30, 2018 BGP-LS Extend for Inter-AS Topology Retrieval draft-wang-idr-bgpls-inter-as-topology-ext-01 Abstract This document describes the process to build BGP-LS key parameters in Native IP multi-domain scenario and defines some new inter-AS TE related TLVs for BGP-LS to let SDN controller retrieve the network topology automatically under various environments. Such process and extension can expand the usage of BGP-LS protocol to multi- domain, enable the network operator to collect the connection relationship between different AS domains and then calculate the overall network topology automatically based on the information provided by BGP-LS protocol. 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 30, 2018. Copyright Notice Copyright (c) 2018 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 Expires December 30, 2018 [Page 1] Internet-Draft BGP-LS-Inter-As-Ext June 2018 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. Inter-AS Domain Scenarios. . . . . . . . . . . . . . . . . . 3 3.1. IS-IS/OSPF Inter-AS Native IP Scenario . . . . . . . . . 3 3.2. IS-IS/OSPF Inter-AS TE Scenario . . . . . . . . . . . . . 4 4. Inter-AS TE related TLVs . . . . . . . . . . . . . . . . . . 5 5. Topology Reconstruction. . . . . . . . . . . . . . . . . . . 5 6. Security Considerations . . . . . . . . . . . . . . . . . . . 5 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 8. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 5 9. Normative References . . . . . . . . . . . . . . . . . . . . 6 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 7 1. Introduction BGP-LS [RFC7752] describes the methodology that using BGP protocol to transfer the Link-State information. Such method can enable SDN controller to collect the underlay network topology automatically, but normally it can only get the information within one IGP domain. If the operator has more than one IGP domain, and these domains interconnect with each other, there is no general TLV within current BGP- LS to transfer the interconnect information. Draft [I-D.ietf-idr-bgpls-segment-routing-epe] defines some extensions for exporting BGP peering node topology information (including its peers, interfaces and peering ASs) in a way that is exploitable in order to compute efficient BGP Peering Engineering policies and strategies. Such information can also be used to calculate the interconnection topology among different IGP domains, but it requires the border routers to run BGP-LS protocol to collect this information and report them to the PCE/SDN controller, which restricts the deployment flexibility of BGP-LS protocol. This draft analysizes the situations that the PCE/SDN controller needs to get about the inter-connected information between different AS domains, defines new TLVs to extend the BGP-LS protocol to transfer the key information related to the interconnect TE topology. After that, the SDN controller can then deduce the multi-domain topology automatically based on the information from BGP-LS protocol. Wang Expires December 30, 2018 [Page 2] Internet-Draft BGP-LS-Inter-As-Ext June 2018 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 RFC 2119 [RFC2119] . 3. Inter-AS Domain Scenarios. Fig.1 illustrates the multi-domain scenarios that this draft discussed. Normally, SDN Controller can get the topology of IGP A and IGP B individually via the BGP-LS protocol, but it can't get the topology connection information between these two IGP domains because there is generally no IGP protocol run on the connected links. +-----------------+ +----+IP SDN Controller+----+ | +-----------------+ | | | |BGP-LS |BGP-LS | | +---------------+-----+ +-----+--------------+ | +--+ +-++ ++-+ +-++ +|-+ +--+| | |S1+--------+S2+---+B1+-----------+B2+---+T1+--------+T2|| | +-++ N1 +-++ ++-+ +-++ ++++ N2 +-++| | | | | | || | | | | | | | || | | | +-++ +-++ ++-+ +-++ ++++ +-++| | |S4+--------+S3+---+B3+-----------+B4+---+T3+--------+T4|| | +--+ +--+ ++-+ +-++ ++-+ +--+| | | | | | | | | | IGP A | | IGP B | +---------------------+ +--------------------+ Fig.1 Inter-AS Domain Scenarios 3.1. IS-IS/OSPF Inter-AS Native IP Scenario When the IGP A or IGP B runs native IS-IS/OSPF protocol, the operator often redistributes the IPv4/IPv6 prefixes of interconnect links into IS-IS/OSPF protocol to ensure the inter-domain connectivity. If the IGP runs IS-IS protocol, the redistributed link information will be carried in IP External Reachability Information TLV within the Level 2 PDU type that defined in [RFC1195], every router within the IGP domain can deduce the redistributed router from the IS-IS LSDB. Wang Expires December 30, 2018 [Page 3] Internet-Draft BGP-LS-Inter-As-Ext June 2018 If the IGP runs OSPF protocol,[RFC2328]defines the type 5 external LSA to transfer the external IPv4 routes; [I-D.ietf-ospf-ospfv3-lsa-extend] defines the "External-Prefix TLV" to transfer the external IPv6 routes; these LSAs have also the advertising router information that initiates the redistribute activity. Every router within IGP domain can also deduce the redistributed router from the OSPF LSDB. For prefix information that associated with each router, BGP-LS [RFC7752] defines the Prefix NLRI which is illustrated below: 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 +-+-+-+-+-+-+-+-+ | Protocol-ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Identifier | | (64 bits) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // Local Node Descriptors (variable) // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // Prefix Descriptors (variable) // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: The IPv4/IPv6 Topology Prefix NLRI Format For these redistributed inter-domain links, their prefix information should be included in the "Prefix Descriptor", and the associated redistributed router information should be included in the "Local Node Descriptors". When such information is reported via the BGP-LS protocol, the PCE/ SDN controller can construct the underlay inter-domain topology according to procedure described in section 5 3.2. IS-IS/OSPF Inter-AS TE Scenario [RFC5316] and [RFC5392] define the IS-IS and OSPF extensions respectively to deal with the requirements for inter-AS traffic engineering. They define some new sub-TLVs(Remote AS Number、IPv4 Remote ASBR ID、IPv6 Remote ASBR ID) which are associated with the inter-AS TE link TLVs to report the TE topology between different domains. These TLVs are flooded within the IGP domain automatically. If the PCE/SDN controller can know these information via one of the interior router that runs BGP-LS protocol, the PCE/SDN controller can rebuild the inter-AS TE topology correctly. Wang Expires December 30, 2018 [Page 4] Internet-Draft BGP-LS-Inter-As-Ext June 2018 4. Inter-AS TE related TLVs This draft proposes to add three new TLVs that is included within the inter-AS TE link NLRI to transfer the information via BGP-LS, which are required to build the inter-AS related topology by the PCE/SDN controller. The following Link Descriptor TLVs are added into the Link NLRI in BGP-LS protocol : +-----------+---------------------+--------------+----------------+ | TLV Code | Description |IS-IS/OSPF TLV| Reference | | Point | | /Sub-TLV | (RFC/Section) | +-----------+---------------------+--------------+----------------+ | TBD |Remote AS Number | 24/21 | [RFC5316]/3.3.1| | | | | [RFC5392]/3.3.1| | TBD |IPv4 Remote ASBR ID | 25/22 | [RFC5316]/3.3.2| | | | | [RFC5392]/3.3.2| | TBD |IPv6 Remote ASBR ID | 26/24 | [RFC5316]/3.3.3| | | | | [RFC5392]/3.3.3| +-----------+---------------------+--------------+----------------+ 5. Topology Reconstruction. When SDN Controller gets such information from BGP-LS protocol, it should compares the proximity of the redistributed prefixes. If they are under the same network scope, then it should find the corresponding associated router information, build the link between these two border routers. After iterating the above procedures for all of the redistributed prefixes, the SDN controller can then retrieve the connection topology between different domains automatically. 6. Security Considerations TBD. 7. IANA Considerations TBD. 8. Acknowledgement The author would like to thank Acee Lindem and Ketan Talaulikar for their valuable comments and suggestions, thank also the comments from Jeff Tantsura and Dhruv Dhody. Wang Expires December 30, 2018 [Page 5] Internet-Draft BGP-LS-Inter-As-Ext June 2018 9. Normative References [I-D.ietf-idr-bgp-ls-segment-routing-ext] Previdi, S., Talaulikar, K., Filsfils, C., Gredler, H., and M. Chen, "BGP Link-State extensions for Segment Routing", draft-ietf-idr-bgp-ls-segment-routing-ext-08 (work in progress), May 2018. [I-D.ietf-idr-bgpls-segment-routing-epe] Previdi, S., Filsfils, C., Patel, K., Ray, S., and J. Dong, "BGP-LS extensions for Segment Routing BGP Egress Peer Engineering", draft-ietf-idr-bgpls-segment-routing- epe-15 (work in progress), March 2018. [I-D.ietf-ospf-ospfv3-lsa-extend] Lindem, A., Roy, A., Goethals, D., Vallem, V., and F. Baker, "OSPFv3 LSA Extendibility", draft-ietf-ospf-ospfv3- lsa-extend-23 (work in progress), January 2018. [I-D.ietf-teas-native-ip-scenarios] Wang, A., Huang, X., Qou, C., Huang, L., and K. Mi, "CCDR Scenario, Simulation and Suggestion", draft-ietf-teas- native-ip-scenarios-00 (work in progress), February 2018. [RFC1195] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and dual environments", RFC 1195, DOI 10.17487/RFC1195, December 1990, . [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, . [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, . Wang Expires December 30, 2018 [Page 6] Internet-Draft BGP-LS-Inter-As-Ext June 2018 [RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and S. Ray, "North-Bound Distribution of Link-State and Traffic Engineering (TE) Information Using BGP", RFC 7752, DOI 10.17487/RFC7752, March 2016, . [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, . [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, . Author's Address Aijun Wang China Telecom Beiqijia Town, Changping District Beijing, Beijing 102209 China Email: wangaj.bri@chinatelecom.cn Wang Expires December 30, 2018 [Page 7]