IDR Working Group R. Chen Internet-Draft Ch. Dai Intended status: Standards Track Sh. Peng Expires: July 14, 2021 ZTE Corporation January 10, 2021 Inter-domain Network Slicing via BGP-LU draft-zhou-idr-inter-domain-lcu-02 Abstract This document aims to solve inter-domain network slicing problems using existing technologies. It attempts to establish multiple BGP- LU LSPs of different colors for a prefix to stitch multiple network segments. 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 July 14, 2021. 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 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. Chen, et al. Expires July 14, 2021 [Page 1] Internet-Draft Inter-domain Network Slicing via BGP-LU January 2021 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Requirements notation . . . . . . . . . . . . . . . . . . . . 2 3. Color . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 4. Advertising multiple paths . . . . . . . . . . . . . . . . . 3 5. Assigning Label(s) . . . . . . . . . . . . . . . . . . . . . 3 6. Inter-domain Network Slicing via BGP-LU . . . . . . . . . . . 4 7. Deploy Considerations . . . . . . . . . . . . . . . . . . . . 6 8. Security Considerations . . . . . . . . . . . . . . . . . . . 6 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 10.1. Normative References . . . . . . . . . . . . . . . . . . 6 10.2. Information References . . . . . . . . . . . . . . . . . 7 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 1. Introduction As described in [I-D.peng-teas-network-slicing], in the traditional end to end inter-domain network slicing, BGP-LU to build inter-domain MPLS LSP, and overlay service will be directly over BGP-LU LSP. [RFC8277] specifies a set of procedures for using BGP to advertise that a specified router has bound a specified MPLS label to a specified address prefix. It's an effective way for inter-domain labels, but it does not have the ability to select the underlying network resources. This document describes the colored BGP-LU LSP, which defines the multiple paths for the same destination prefix can be advertised in BGP UPDATE message, and each UPDATE message can contain the color Extended Community [I-D.ietf-idr-tunnel-encaps] with different color value, which helps to select the underlying resources. 2. Requirements notation 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. Color [I-D.ietf-idr-tunnel-encaps] introduces the concept of color, which is used as one of the KEY of SR policy [I-D.ietf-spring-segment-routing-policy]. The color of SR policy defines a TE purpose, which includes a set of constraints such as bandwidth, delay, TE metric, etc. Chen, et al. Expires July 14, 2021 [Page 2] Internet-Draft Inter-domain Network Slicing via BGP-LU January 2021 Color is used a policy keyword to help routing decisions and can be carried through Community attribute [I-D.ietf-idr-tunnel-encaps] in BGP. Each UPDATE SHOULD contain a Color Extended Community with a specific color value, the Color Sub-TLV is only an opaque extended community. 4. Advertising multiple paths A BGP speaker can advertise multiple paths for a particular address prefix by a Path identifier in the Extended NLRI Encoding as defined in [RFC7911]. +--------------------------------+ | Path Identifier (4 octets) | +--------------------------------+ | Length (1 octet) | +--------------------------------+ | Prefix (variable) | +--------------------------------+ The Path Identifier only identifies a path, not carrying any particular semantics.In this document, it can be generated by the tuple. The assignment to the Path Identifier for a path by a BGP speaker is purely a local matter. Therefore, if a BGP speaker has two colors for the prefix P, which correspond to two different paths, it may advertise two UPDATE NLRIs, with color1 extended community and with color2 extended community. Pathid1 and pathid2 in two UPDATE NLRIs MUST be different. Note that in this document, BGP speakers acting as border routers that interact with external neighbors need to support advertising multiple paths corresponding to the same prefix. Although multiple paths have differnet path ids, they have the same next hop. As for the procedures of mutual backup paths with the same prefix and the differnet next hops, refer to [RFC7911]. 5. Assigning Label(s) [RFC8277] describes how to use BGP to bind MPLS label(s) to address prefixes. The specific format of the UPDATE message is detailed in Section 2 of [RFC8277]. [RFC8277] Section 3.2 details the process of modifying the Label field during propagation. When propagating a SAFI-4 or SAFI-128 route, if the Network Address of Next Hop field has never changed, the label field must remain unchanged. Otherwise, if the Network Chen, et al. Expires July 14, 2021 [Page 3] Internet-Draft Inter-domain Network Slicing via BGP-LU January 2021 Address of Next Hop field is changed, the label field(s) of the propagating route must contain the label(s) that is (are) bound to the prefix at the new next hop. What the label changes to depends on the local policy. However, LSPs with different color paths need to have different label(s). 6. Inter-domain Network Slicing via BGP-LU [RFC7911] defined that multiple paths for a particular address prefix by a Path identifier can be advertised in BGP UPDATE message, and each UPDATE message can contain the Color Extended Community [I-D.ietf-idr-tunnel-encaps] with different color value. That is a simple existing way to realize BGP-LU color function, and no protocol extension required. Consider the following example of establishing multiple BGP-LU LSPs per different colors in a cross-domain scenario. Chen, et al. Expires July 14, 2021 [Page 4] Internet-Draft Inter-domain Network Slicing via BGP-LU January 2021 <1.1.1.1, path-id1> <1.1.1.1, path-id1> <1.1.1.1, path-id1> ------------------------------------------------------------------> .----. .------. ( ) ( ) .-( )-. .-( )-. +---+---color1----+----+ +---+----color1----+---+ |PE1|\---SR-TE1---/|AS |-sub-if1 with slice1-|AS |\---SR-TE1---/|PE2| | |/---SR-TE2---\|BR1|-sub-if2 with slice2-|BR2|/---SR-TE2---\| | +---+---color2---- +---+ +---+--color2------+---+ ( ) ( ) '--( AS1 )--' '--( AS2 )--' ( ) ( ) '-' '-' -------------------------------------------------------------------> <1.1.1.1, path-id2> <1.1.1.1, path-id2> <1.1.1.1, path-id2> Label Exchange Tables: ASBR1: ASBR2: inLabel outLabel nextHop inLabel outLabel nextHop 201 200 SR-TE1 201 201 sub-if1 202 200 SR-TE2 202 202 sub-if2 PE2: prefix color outLabel nextHop 1.1.1.1 1 201 SR-TE1 1.1.1.1 2 202 SR-TE2 Figure 1: Example of Inter-domain Network Slicing via BGP-LU In figure 1, PE1 advertises two paths: <1.1.1.1, path-id1> carries the color1 attribute and <1.1.1.1, path-id2> carries the color2 attribute to ASBR1.PE1 advertises the binding between the prefix 1.1.1.1 and label 200. Because of the end node, both paths have the same label value 200. ASBR1 receives these two paths from PE1, and when sending to ASBR2, it modifies the next hop to itself. And allocate two new labels based on . As shown in Figure 1, ASBR1 sends two paths to ASBR2, <1.1.1.1, path-id1> carries color1+label201, and <1.1.1.1, path-id2> carries color2+label202. Similarly, ASBR2 also generates two different labels based on the . As shown in Figure 1, multiple end to end BGP-LU LSPs are established.Different BGP-LU LSPs select the lower SR-BE/TE tunnels according to their colors. Chen, et al. Expires July 14, 2021 [Page 5] Internet-Draft Inter-domain Network Slicing via BGP-LU January 2021 7. Deploy Considerations All BGP routers (PE1--ASBR1, ASBR1---ASBR2, ASBR2---PE2) SHOULD be BGP-LU neighbors in advance. There may be multiple border routers to ensure multipath backup. All routers require the ADD-PATH Capability which is described in chapter 4 of [RFC7911]. This document not only supports interprovider VPNs while the customer sites belong to different ASs, but also supports the Carrier-of- Carriers VPNs while the customer site belong to the same AS. Multiple operators are involved, so AS border routers may involve color mapping, color namespaces, or color service chains. These services can be delivered by the controller configurations or the local configurations. 8. Security Considerations TBD 9. IANA Considerations TBD. 10. References 10.1. Normative References [I-D.ietf-idr-tunnel-encaps] Patel, K., Velde, G., Sangli, S., and J. Scudder, "The BGP Tunnel Encapsulation Attribute", draft-ietf-idr-tunnel- encaps-22 (work in progress), January 2021. [I-D.ietf-spring-segment-routing-policy] Filsfils, C., Talaulikar, K., Voyer, D., Bogdanov, A., and P. Mattes, "Segment Routing Policy Architecture", draft- ietf-spring-segment-routing-policy-09 (work in progress), November 2020. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC7911] Walton, D., Retana, A., Chen, E., and J. Scudder, "Advertisement of Multiple Paths in BGP", RFC 7911, DOI 10.17487/RFC7911, July 2016, . Chen, et al. Expires July 14, 2021 [Page 6] Internet-Draft Inter-domain Network Slicing via BGP-LU January 2021 [RFC8277] Rosen, E., "Using BGP to Bind MPLS Labels to Address Prefixes", RFC 8277, DOI 10.17487/RFC8277, October 2017, . 10.2. Information References [I-D.peng-teas-network-slicing] Peng, S., Chen, R., Mirsky, G., and F. Qin, "Packet Network Slicing using Segment Routing", draft-peng-teas- network-slicing-04 (work in progress), October 2020. Authors' Addresses Ran Chen ZTE Corporation Email: chen.ran@zte.com.cn Chunning Dai ZTE Corporation Email: dai.chunning@zte.com.cn Shaofu Peng ZTE Corporation Email: peng.shaofu@zte.com.cn Chen, et al. Expires July 14, 2021 [Page 7]