Network Working Group Y. Gu Internet-Draft Huawei Intended status: Standards Track H. Chen Expires: October 4, 2019 China Telecom Co., Ltd. D. Ma ZDNS S. Zhuang Huawei April 2, 2019 BMP for BGP Route Leak Detection draft-gu-grow-bmp-route-leak-detection-02 Abstract According to RFC7908 [RFC7908], Route leaks refer to case that the delivery range of route advertisements is beyond the expected range. For many current security protection solutions, the ISPs (Internet Service Providers) are focusing on finding ways to detect the happening of route leaks. However, the real-time route leak detection if any occurs is important as well. This document extends the BGP Monitoring Protocol (BMP) [RFC7854] to provide a routing security scheme suitable for ISPs to detect BGP route leaks within their own networks. Requirements Language 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]. 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 October 4, 2019. Gu, et al. Expires October 4, 2019 [Page 1] Internet-Draft Route Leak Detection April 2019 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 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. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2.1. ISP Route Leak Prevention Methods . . . . . . . . . . . . 3 2.2. Challenge of the Current Route Leak Prevention Methods . 4 3. Route Leak Detection Considerations . . . . . . . . . . . . . 4 4. Extending BMP for RLD . . . . . . . . . . . . . . . . . . . . 6 5. Implementation Examples . . . . . . . . . . . . . . . . . . . 7 6. Benefits . . . . . . . . . . . . . . . . . . . . . . . . . . 9 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9 8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 9 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 10. Security Considerations . . . . . . . . . . . . . . . . . . . 9 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 11.1. Normative References . . . . . . . . . . . . . . . . . . 9 11.2. Informative References . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 1. Terminology BMP: BGP Monitoring Protocol BMS: BGP Monitoring Station C2P: Customer to Provider ISP: Internet Service Provider P2P: Peer to Peer RIB: Routing Information Base Gu, et al. Expires October 4, 2019 [Page 2] Internet-Draft Route Leak Detection April 2019 RLD: Route Leak Detection 2. Introduction RFC 7908 defines "Route Leak" as: A route leak is the propagation of routing announcement(s) beyond their intended scope, which can result in possible situations such as eavesdropping, device overload, route black hole and so on. More specifically, the intended scope of route announcements is usually defined by local route filtering/ distribution policies within devices. These policies are designed to realise the pair-wise peering business relationships between ASes (autonomous systems), which include Customer to Provider (C2P), Peer to Peer (Peer to Peer), and Provider to Customer (P2C). In a C2P relationship, the customer pays the provider for traffic sent between the two ASes. In return, the customer gains access to the ASes the provider can reach, including those which the provider reaches through its own providers. In a P2P relationship, the peering ASes gain access to each other's customers, typically without either AS paying the other[Luckie]. RFC 7908 classifies six typical route leaks situations based on the documented events. 2.1. ISP Route Leak Prevention Methods Since BGP itself does not provide any route leak prevention/ protection, in the current networks, network administrators/operators typically configure export policies on the AS border routers (ASBRs) to prevent route leak. For example, refer to the topology in Figure 1, the bussiness relationship between AS2 and AS1 is P2C, and P2C between AS1 and AS3, and C2P between AS1 and AS4. According to RFC 7908, for AS1, any route received from the provider AS (i.e., AS2 here) and then distributed to its provider AS (i.e., AS4) is treated as route leak (Type 1 route leak). Thus, to prevent such case from happening, an export policy is configured at ASBR R2 of AS1. The export strategies are meant for the intention that "routes from AS2 can be sent to AS3, and cannot be sent to AS4." Routes received from AS2 at AS1 (i.e., R1 here) are marked with BGP community attributes so that when these routes arrive at any exit ASBR of AS1 (i.e., R2 here) is filtered by the route leak policy configured at R2 by identifying the community attribute attached from R1. This community attribute stands for the peering business relationship between AS2 and AS1. Suppose the destination of the route A is AS4, then R2 will not distribute Route A to AS4 were the export policies configured correctly. Gu, et al. Expires October 4, 2019 [Page 3] Internet-Draft Route Leak Detection April 2019 ************************* * * "Send Route Route A * AS1 +*+-----> A to AS3" +--> * + * +-----+ +-----+ * +---+ +---+ *+P2C+--|AS3 +----+ ... +--+ AS2 +---+P2C+*+-+ R1+---------+ R2| * +-----+ +-----+ * +-+-+\ +---+ * * | \\ // |\ * * | \\// | \ * "Do not send * | //\ | \+-------> Route A to AS4" * | // \\ | * +-----+ * | / \ | *+C2P+--|AS4 +----+ ... * +-+-+ +-+-+ * +-----+ +--+ R3+---------+ R4| * * +---+ +---+ * * * ************************* Figure 1: Route propagatin between ISPs 2.2. Challenge of the Current Route Leak Prevention Methods However, it could happen that the export policies configured at ASBRs to prevent route leak are misconfigured or simply out of date considering the changes of bussiness relationships between ASes. For example, the export policies at R2 fails to filter Route A and distributes it to AS4, then a route leak happens. Thus, in addition to such route leak prevention methods, there requires a valid detection method to detect any occurred leak in a timely manner so that the incorrect policies can be identified to avoid further leaks. 3. Route Leak Detection Considerations There are some existing methods proposed for Route Leak Detection (RLD). It's straightforward to think of the idea of using a route's AS path combined with the business relationship information between ISPs/ASes to detect any route leak. However, there exist implementation difficuties. First of all, the business relationship information between ISPs/ASes is not publicly disclosed due to confidentiality reasons. Thus, many attempts have been made to infer relationships and strategies between ASs, however, the accuracy of these techniques is often questioned. In particular, the increase in the number of Internet Exchange Points (IXPs) and their role in the recent "flattening" of the Internet Gu, et al. Expires October 4, 2019 [Page 4] Internet-Draft Route Leak Detection April 2019 topology, makes that a large fraction of AS relationships cannot be discovered using these data collection points [Siddiqui]. Secondly, the acquisition of BGP AS path information is also no easy work. Some BGP monitoring tools, such as Looking Glass and Route View, the data accuracy or completeness remains to be an issue. This has led to the such BGP monitoring tools not being well used by various ISPs. Some other technologies extend existing routing protocols to realize RLD. For example, modify the BGP update message, which may bring about compatibility problems involved in the implementation of the solution. Besides, new extension brings interoperation, device upgrade issues. Thus, extending the routing protocols is not the first choice for leak detection if there are other options. Summarizing the above discussions, we have identified the following considerations when designing a RLD solution: o Consideration 1: The detection should not depend on inferred business relationship information, which leads to inaccurate detection; o Consideration 2: The detection should not depend on inaccurate/ incomplete AS path information , which leads to inaccurate detection or a detection miss; o Consideration 3: The detection should try to avoid extension works of routing protocols considering the interoperation issues; BMP (BGP Monitoring Protocol) is currently deployed by OTT and operators to monitor the BGP routes, such as monitoring BGP Adj-RIB- In using the process defined in [RFC7854], and monitoring BGP Adj- RIB-Out using the process defined in [I-D.ietf-grow-bmp-adj-rib-out]. Considering the above mentioned requirements of RLD design, extending BMP to collect the business relationships between an ISP and its neighboring ASes can be a good choice for this single ISP to do RLD. There are several merits: o First of all, it does not involve data disclosure issue since the collected relationship information is only between itself and its neighboring ASes; o Secondly, BMP provides accurate and complete BGP data monitoring within a singe AS; o Thirdly, it does not require BGP extension work, and thus no interoperation concern. Gu, et al. Expires October 4, 2019 [Page 5] Internet-Draft Route Leak Detection April 2019 Thus, a single ISP can deploy this method to do RLD without relying on any other information from either other ISPs or third party tools. There are cases where some networks' owners want to retain their route space internally, but they don't want them to be leaked outside, then they can use the proposing suggestion in this document. 4. Extending BMP for RLD +------------+ | BMP server | +------> + +<-------+ | | RLD ser^er | | + +------------+ + BMP RM adj_rib_in: BMP RM adj_rib_out: relationship between relationship between AS2 and AS1 AS1 and AS4 | + ***|********************* | * | * | "Send Route Route A * | AS1 +*+---------> A to AS3" +--> * | + * | +-----+ +-----+ * +---+ +---+ *+P2C+-----+ AS3 +----+ ... +--+ AS2 +---+P2C+*+-+ R1+---------+ R2| * | +-----+ +-----+ * +-+-+\ +---+ * | * | \\ // |\ * | * | \\// | \ * | "Do not send * | //\ | \+-----------> Route A to AS4" * | // \\ | * | +-----+ * | / \ | *+C2P+-----+ AS4 +----+ ... * +-+-+ +-+-+ * | +-----+ +--+ R3+---------+ R4+----------+ * +---+ +---+ * * * ************************* Figure 2: RLD depolyment by a single ISP A Relationship TLV is defined for BMP Route Monitoring Message. Considering that the AS relationships are sometims per route based instead of per peer/AS based, this TLV is added at the end of each BGP Update Message, and then wrapped up by the BMP per peer header and comon header. The TLV format is defined as follows: Gu, et al. Expires October 4, 2019 [Page 6] Internet-Draft Route Leak Detection April 2019 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 (2 octets) | Length (2 octets) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Value(1 octet)| +-+-+-+-+-+-+-+-+ Figure 3: Relationship TLV Type (2 octets) = TBD, the Relatiship TLV indicates that this TLV represents the business relationship between the AS that sends the route and the AS that receives the route. Length (2 octets): Defines the length of the Value filed. The Value field is a 2 bit field, and can be "00", "01", and "10", which represents three types of relationships, i.e., P2C, P2P, C2P, respectively. As shown in Figure 3, with the Relationship TLV attached to each Route Monitoring Message, the RLD server (also working as the BMP server) combines the BMP adj_rib_in message collected from R1 and the BMP adj_rib_out message collected from R4 to decide if there's a route leak. For example, if the Relationship TLV in R1's adj_rib_in message indicates a value of "00", and the Relationship TLV in R4's adj_rib_out message indicates a value of "10", then the RLD server knows there exists a route leak. 5. Implementation Examples Let's take the topology of Figure 4 as an example to describe the implementation of the Intra-AS route leak detection. Gu, et al. Expires October 4, 2019 [Page 7] Internet-Draft Route Leak Detection April 2019 +--------+ | RLD | | Server | +---|----+ | *************|*********** Route A * ISP A | * ---> * AS A1 | * AS B1 * | * AS E1 +-------+ (1)+---+ (2) | +---+ +-------+ ... ---| ISP B |----|R1 |-----+---|R2 |-----| ISP E |--- ... +-------+ P1 +---+\ +---+ * +-------+ AS C1 * /| \\(2) // | * AS F1 +-------+ * / | \\// | * +-------+ ... ---| ISP C |--- |(2) //\ | /---| ISP F |--- ... +-------+ * | // \\ | / * +-------+ AS D1 * | / \ | / * AS G1 +-------+ * +---+ +---+ (3) +-------+ ... ---| ISP D |----|R3 |---------|R4 |-----| ISP G |--- ... +-------+ * +---+ +---+ P2 +-------+ * * ************************* Figure 4: RLD Server for One ISP Routing between multi-AS and doing route-leak verifications in Local- AS (AS1): o (1) R1 receives Route A from AS B1, Sets ISP-Specific community per the business relation between AS A1 and AS B1; R1 sets business relation to the BMP Route-Monitoring message that including Route A within the message, and sends the BMP Route- Monitoring message to RLD Server; o (2) R1 sends Route A to the other border routers (e.g. R4); o (3) Per the ISP-Specific community in Route A and the business relation between AS A1 and AS F1/G1, R4 can control the route advertisement, e.g., Send A to AS F1, Not send A to AS G1. R4 sets business relation to the BMP Route-Monitoring message that including Route A within the message if Route A been sent to AS F1/G1, and sends the BMP Route-Monitoring message to RLD Server; o (4) RLD Server doing route-leak verifications using the BMP information collecting from R1 & R4. The above approach can be an ISP route leak self-checking method: 1.No dependency on third-party ISP; 2.No BGP extension required. Gu, et al. Expires October 4, 2019 [Page 8] Internet-Draft Route Leak Detection April 2019 6. Benefits BMP is a good choice for the detection information collection with minor extension work while meeting above requirements. o Do not change BGP protocol; o Not put heavy impact on BGP processes; o Singe-ISP-Available solution. 7. Acknowledgements The authors would like to acknowledge the review and inputs from Jared Mauch, Alexander Azimov, Gang Yan, Zhenbin Li, Aijun Wang and the working group. 8. Contributors Haibo Wang Huawei Email: rainsword.wang@huawei.com 9. IANA Considerations TBD. 10. Security Considerations It is not believed that this document adds any additional security considerations. 11. References 11.1. Normative References [I-D.ietf-grow-bmp-adj-rib-out] Evens, T., Bayraktar, S., Lucente, P., Mi, K., and S. Zhuang, "Support for Adj-RIB-Out in BGP Monitoring Protocol (BMP)", draft-ietf-grow-bmp-adj-rib-out-04 (work in progress), March 2019. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . Gu, et al. Expires October 4, 2019 [Page 9] Internet-Draft Route Leak Detection April 2019 [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A Border Gateway Protocol 4 (BGP-4)", RFC 4271, DOI 10.17487/RFC4271, January 2006, . [RFC7854] Scudder, J., Ed., Fernando, R., and S. Stuart, "BGP Monitoring Protocol (BMP)", RFC 7854, DOI 10.17487/RFC7854, June 2016, . [RFC7908] Sriram, K., Montgomery, D., McPherson, D., Osterweil, E., and B. Dickson, "Problem Definition and Classification of BGP Route Leaks", RFC 7908, DOI 10.17487/RFC7908, June 2016, . 11.2. Informative References [Luckie] claffy, M. L. M. L. A. D. V. G. K., "AS Relationships, Customer Cones, and Validation", October 2013. [Siddiqui] Ramirez, M. S. S. D. M. M. Y. R. S. X. M. W., "Route Leak Detection Using Real-Time Analytics on local BGP Information", 2014. Authors' Addresses Yunan Gu Huawei Huawei Bld., No.156 Beiqing Rd. Beijing 100095 China Email: guyunan@huawei.com Huanan Chen China Telecom Co., Ltd. 109 Zhongshan W Ave Guangzhou 510630 China Email: chenhn8.gd@chinatelecom.cn Gu, et al. Expires October 4, 2019 [Page 10] Internet-Draft Route Leak Detection April 2019 Di Ma ZDNS 4 South 4th St. Zhongguancun Beijing, Haidian China Email: madi@zdns.cn Shunwan Zhuang Huawei Huawei Bld., No.156 Beiqing Rd. Beijing 100095 China Email: zhuangshunwan@huawei.com Gu, et al. Expires October 4, 2019 [Page 11]