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Zhuang 7 Huawei 8 July 12, 2021 10 Destination-IP-Origin-AS Filter for BGP Flow Specification 11 draft-wang-idr-flowspec-dip-origin-as-filter-04 13 Abstract 15 BGP Flowspec mechanism (BGP-FS) [RFC8955] [RFC8956]propogates both 16 traffic Flow Specifications and Traffic Filtering Actions by making 17 use of the BGP NLRI and the BGP Extended Community encoding formats. 18 This document specifies a new BGP-FS component type to support AS- 19 level filtering. The match field is the origin AS number of the 20 destination IP address that is encoded in the Flowspec NLRI. This 21 function is applied in a single administrative domain. 23 Requirements Language 25 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 26 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 27 document are to be interpreted as described in [RFC2119]. 29 Status of This Memo 31 This Internet-Draft is submitted in full conformance with the 32 provisions of BCP 78 and BCP 79. 34 Internet-Drafts are working documents of the Internet Engineering 35 Task Force (IETF). Note that other groups may also distribute 36 working documents as Internet-Drafts. The list of current Internet- 37 Drafts is at https://datatracker.ietf.org/drafts/current/. 39 Internet-Drafts are draft documents valid for a maximum of six months 40 and may be updated, replaced, or obsoleted by other documents at any 41 time. It is inappropriate to use Internet-Drafts as reference 42 material or to cite them other than as "work in progress." 44 This Internet-Draft will expire on January 13, 2022. 46 Copyright Notice 48 Copyright (c) 2021 IETF Trust and the persons identified as the 49 document authors. All rights reserved. 51 This document is subject to BCP 78 and the IETF Trust's Legal 52 Provisions Relating to IETF Documents 53 (https://trustee.ietf.org/license-info) in effect on the date of 54 publication of this document. Please review these documents 55 carefully, as they describe your rights and restrictions with respect 56 to this document. Code Components extracted from this document must 57 include Simplified BSD License text as described in Section 4.e of 58 the Trust Legal Provisions and are provided without warranty as 59 described in the Simplified BSD License. 61 Table of Contents 63 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 64 2. Definitions and Acronyms . . . . . . . . . . . . . . . . . . 3 65 3. The Flow Specification Encoding for Destination-IP-Origin-AS 66 Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 67 4. Use Case . . . . . . . . . . . . . . . . . . . . . . . . . . 4 68 5. Security Considerations . . . . . . . . . . . . . . . . . . . 6 69 6. IANA . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 70 7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 6 71 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6 72 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 73 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 75 1. Introduction 77 BGP Flow Specification (BGP-FS) [RFC8955] [RFC8956] defines a new BGP 78 NLRI to distribute traffic flow specification rules via BGP 79 ([RFC4271]). BGP-FS policies have a match condition that may be 80 n-tuple match in a policy, and an action that modifies the packet and 81 forwards/drops the packet. Via BGP, new filter rules can be sent to 82 all BGP peers simultaneously without changing router configuration, 83 and the BGP peer can install these routes in the forwarding table. 84 BGP-FS defines Network Layer Reachability Information (NLRI) format 85 used to distribute traffic flow specification rules. NLRI (AFI=1, 86 SAFI=133) is for IPv4 unicast filtering. NLRI (AFI=1, SAFI=134) is 87 for BGP/MPLS VPN filtering.[I-D.ietf-idr-flowspec-l2vpn][I-D.ietf- 88 idr-flowspec-l2vpn] extends the flow-spec rules for layer 2 Ethernet 89 packets. 91 This document specifies a new BGP-FS component type to support AS- 92 level filtering. The match field is the origin AS number of the 93 destination IP address that is encoded in the Flowspec NLRI. This 94 function is applied in a single administrative domain. 96 2. Definitions and Acronyms 98 o FS: Flow Specification 100 o Destination-IP-Origin-AS: The origin AS number of the destination 101 IP address 103 3. The Flow Specification Encoding for Destination-IP-Origin-AS Filter 105 This document proposes a new flow specification component type that 106 is encoded in the BGP Flowspec NLRI. The following new component 107 type is defined. 109 o Destination-IP-Origin-AS 111 Type TBD1 - Destination-IP-Origin-AS 113 Encoding: 115 Contains a set of {operator, value} pairs that are used to match the 116 Destination-IP-Origin-AS (i.e. the origin AS number of the 117 destination IP address). 119 The operator byte is encoded as: 121 0 1 2 3 4 5 6 7 122 +---+---+---+---+---+---+---+---+ 123 | e | a | len | 0 |lt |gt |eq | 124 +---+---+---+---+---+---+---+---+ 126 Where: 128 e - end-of-list bit. Set in the last {op, value} pair in the list. 130 a - AND bit. If unset, the previous term is logically ORed with the 131 current one. If set, the operation is a logical AND. It MUST be 132 unset in the Destination-IP-Origin-AS filter. 134 len - The length of the value field for this operator given as (1 << 135 len). This encodes 1 (len=00), 2 (len=01), 4 (len=10), and 8 136 (len=11) octets. 138 lt - less than comparison between data and value. 140 gt - greater than comparison between data and value. 142 eq - equality between data and value. 144 The bits lt, gt, and eq can be combined to produce match the 145 Destination-IP-Origin-AS filter or a range of Destination-IP-Origin- 146 AS filter(e.g. less than AS1 and greater than AS2). 148 The value field is encoded as: 150 0 1 2 3 151 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 1 152 +---------------------------------------------------------------+ 153 ~ Destination-IP-Origin-AS (4 octets) ~ 154 +---------------------------------------------------------------+ 156 Per section 10 of [RFC8955] , If a receiving BGP speaker cannot 157 support this new Flow Specification component type, it MUST discard 158 the NLRI value field that contains such unknown components. Since 159 the NLRI field encoding (Section 4 of [RFC8955]) is defined in the 160 form of a 2-tuple , message decoding can skip 161 over the unknown NLRI value and continue with subsequent remaining 162 NLRI. 164 4. Use Case 166 This section describes how to use this function in a simple scenario. 167 Considering the topology shown in Figure 1. In AS64597's R1, if the 168 ISP AS64597 wants to redirect all packets originating from IP Prefix 169 61 to AS64598, first goto to R3, then forward them to AS64598", the 170 ISP AS64597 can use the traditional method or the method defining in 171 this draft. 173 +---------+ 174 | BGP FS | 175 | Server | 176 +----|----+ 177 | 178 | 179 / 180 / 181 ************/************ IP Prefix 81 182 * / * IP Prefix 82 183 IP Prefix 61 * / AS64597 * IP Prefix 83 184 * / * IP Prefix 84 185 +-------+ * +---+/ +---+ * +-------+ 186 +AS64596+-------+ R1+---------+ R2|------+AS64598+ 187 +-------+ * +-+-+\ +---+ */ +-------+ 188 * \ |\ / 189 * \ | \ /* IP Prefix 91 190 * \ | /\* IP Prefix 92 191 * \ | / \ IP Prefix 93 192 * \ |/ *\ IP Prefix 94 193 * \ +-+-+ * \ +-------+ 194 * \-+ R3+------+AS64599+ 195 * +---+ * +-------+ 196 * * 197 ************************* 198 Figure 1: Redirect the traffic using Flowspec 200 Using the traditional method, the ISP AS64597 needs to setup multiple 201 "Destination Prefix + Source Prefix" rules in Router R1 as following: 203 +--------------+--------------+-------------------------+ 204 | Destination | Source Prefix| Redirect to IP Nexthop | 205 | Prefix | | | 206 +--------------+--------------+-------------------------+ 207 | IP Prefix 81 | IP Prefix 61 | R3 | 208 +--------------+--------------+-------------------------+ 209 | IP Prefix 82 | IP Prefix 61 | R3 | 210 +--------------+--------------+-------------------------+ 211 | IP Prefix 83 | IP Prefix 61 | R3 | 212 +--------------+--------------+-------------------------+ 213 | IP Prefix 84 | IP Prefix 61 | R3 | 214 +--------------+--------------+-------------------------+ 215 | More... | 216 +--------------+--------------+-------------------------+ 218 Figure 2: Using the traditional method to redirect the traffic 220 Using the method defining in this draft, the ISP AS64597 needs to 221 setup only one "Destination Origin AS + Source Prefix" rule in Router 222 R1 as following: 224 +--------------+--------------+-------------------------+ 225 | Destination | Source Prefix| Redirect to IP Nexthop | 226 | IP Origin AS | | | 227 +--------------+--------------+-------------------------+ 228 | 64598 | IP Prefix 61 | R3 | 229 +--------------+--------------+-------------------------+ 231 Figure 3: Using the AS-level filtering method to redirect the traffic 233 Obviously, the new method defining in this draft saves a lot of entry 234 spaces on the control plane and forwarding plane, and it would 235 greatly simplify the operation of the control plane, and the more 236 destination prefixes an AS has, the more obvious the benefit. 238 5. Security Considerations 240 No new security issues are introduced to the BGP protocol by this 241 specification. 243 6. IANA 245 IANA is requested to a new entry in "Flow Spec component types 246 registry" with the following values: 248 +----------------------------------------------------------+ 249 | Type | RFC or Draft | Description | 250 +----------------------------------------------------------+ 251 | TBD1 | This Draft | Destination-IP-Origin-AS | 252 +----------------------------------------------------------+ 254 7. Contributors 256 TBD 258 8. Acknowledgments 260 The authors would like to acknowledge the review and inputs from Gang 261 Yan, Zhenbin Li, Rainbow Wu, Jie Dong and Ziqing Cao. 263 9. References 265 [I-D.ietf-idr-flowspec-l2vpn] 266 Hao, W., Eastlake, D. E., Litkowski, S., and S. Zhuang, 267 "BGP Dissemination of L2 Flow Specification Rules", draft- 268 ietf-idr-flowspec-l2vpn-16 (work in progress), November 269 2020. 271 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 272 Requirement Levels", BCP 14, RFC 2119, 273 DOI 10.17487/RFC2119, March 1997, 274 . 276 [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A 277 Border Gateway Protocol 4 (BGP-4)", RFC 4271, 278 DOI 10.17487/RFC4271, January 2006, 279 . 281 [RFC8955] Loibl, C., Hares, S., Raszuk, R., McPherson, D., and M. 282 Bacher, "Dissemination of Flow Specification Rules", 283 RFC 8955, DOI 10.17487/RFC8955, December 2020, 284 . 286 [RFC8956] Loibl, C., Ed., Raszuk, R., Ed., and S. Hares, Ed., 287 "Dissemination of Flow Specification Rules for IPv6", 288 RFC 8956, DOI 10.17487/RFC8956, December 2020, 289 . 291 Authors' Addresses 293 Haibo Wang 294 Huawei 295 156 Beiqing Road 296 Beijing 100095 297 P.R. China 299 Email: rainsword.wang@huawei.com 301 Aijun Wang 302 China Telecom 303 Beiqijia Town, Changping District 304 Beijing 102209 305 P.R. China 307 Email: wangaj3@chinatelecom.cn 308 Shunwan Zhuang 309 Huawei 310 156 Beiqing Road 311 Beijing 100095 312 P.R. China 314 Email: zhuangshunwan@huawei.com