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Filsfils 5 Expires: October 9, 2020 Cisco Systems, Inc. 6 D. Bernier 7 Bell Canada 8 Z. Li 9 Huawei Technologies 10 F. Clad, Ed. 11 P. Camarillo 12 A. AbdelSalam 13 Cisco Systems, Inc. 14 April 07, 2020 16 Simplifying Firewall Rules with Network Programming and SRH Metadata 17 draft-guichard-spring-srv6-simplified-firewall-02 19 Abstract 21 A clear application of the SRv6 Network Programming model consists in 22 steering, in a stateless manner, packets through a Service Function 23 Chain (SFC). Each Service Function (SF) is identified by a segment. 24 Each SF can enrich its operation thanks to metadata present in the 25 SRH. 27 This document describes a practical use-case where the SF is a 28 firewall and the metadata helps to drastically decrease the number of 29 rules that need to be maintained by the operation team. 31 Status of This Memo 33 This Internet-Draft is submitted in full conformance with the 34 provisions of BCP 78 and BCP 79. 36 Internet-Drafts are working documents of the Internet Engineering 37 Task Force (IETF). Note that other groups may also distribute 38 working documents as Internet-Drafts. The list of current Internet- 39 Drafts is at https://datatracker.ietf.org/drafts/current/. 41 Internet-Drafts are draft documents valid for a maximum of six months 42 and may be updated, replaced, or obsoleted by other documents at any 43 time. It is inappropriate to use Internet-Drafts as reference 44 material or to cite them other than as "work in progress." 46 This Internet-Draft will expire on October 9, 2020. 48 Copyright Notice 50 Copyright (c) 2020 IETF Trust and the persons identified as the 51 document authors. All rights reserved. 53 This document is subject to BCP 78 and the IETF Trust's Legal 54 Provisions Relating to IETF Documents 55 (https://trustee.ietf.org/license-info) in effect on the date of 56 publication of this document. Please review these documents 57 carefully, as they describe your rights and restrictions with respect 58 to this document. Code Components extracted from this document must 59 include Simplified BSD License text as described in Section 4.e of 60 the Trust Legal Provisions and are provided without warranty as 61 described in the Simplified BSD License. 63 Table of Contents 65 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 66 2. Use-case overview . . . . . . . . . . . . . . . . . . . . . . 3 67 3. Demo availability . . . . . . . . . . . . . . . . . . . . . . 5 68 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 69 5. Security Considerations . . . . . . . . . . . . . . . . . . . 5 70 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5 71 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 72 7.1. Normative References . . . . . . . . . . . . . . . . . . 6 73 7.2. Informative References . . . . . . . . . . . . . . . . . 6 74 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 76 1. Introduction 78 The Segment Routing architecture is defined in [RFC8402]. 80 The IPv6 instantiation of Segment Routing, also known as SRv6, 81 leverages the Segment Routing Header (SRH) defined in [RFC8754] to 82 encode a list of segments, as well as some complementary information 83 in an IPv6 header. [I-D.ietf-spring-srv6-network-programming] builds 84 upon the base SRv6 definition and introduces the concept of network 85 programming. In a sense, the list of segments in the SRH is the 86 source code of a network program, while the SRH TLVs represent the 87 memory of that program. 89 Furthermore, [I-D.ietf-spring-sr-service-programming] describes how 90 segments can be associated with Service Functions and defines SRH 91 TLVs specifically designed for carrying service metadata. Together, 92 these documents define an integrated solution for underlay, overlay 93 and SFC that uses a single header and does not require any per-flow 94 state in the network fabric. 96 2. Use-case overview 98 In an SR domain, firewall policies are applied to control how the 99 various endpoints, users or applications are allowed to communicate 100 between each other. These entities are categorized into classes for 101 the purpose of applying policies to pools rather than individual 102 entities. For example, the endpoints in Class1 may be allowed to 103 communicate with those in either Class3 or Class4, but Class2 is can 104 only communicate with Class4, and Class5 cannot communicate with any 105 other class. 107 A reference diagram is depicted on Figure 1. An SRv6-enabled network 108 interconnects 4 classes (Class1..4) and a firewall appliance is in 109 charge of enforcing the network policies. 111 +--------------------------------+ 112 +-------+ | SRv6 domain | +-------+ 113 |Class1 |-+ | | +-|Class3 | 114 +-------+ | +----+----+ +----------+ +----+----+ | +-------+ 115 +-| Node A | | F1 | | Node B |-+ 116 +-|(ingress)|-----|(firewall)|-----|(egress) |-+ 117 +-------+ | +----+----+ +----------+ +----+----+ | +-------+ 118 |Class2 |-+ | ---------------------> | +-|Class4 | 119 +-------+ | | +-------+ 120 +--------------------------------+ 122 Figure 1: Base diagram 124 Node A is configured to steer the traffic coming from Class1 or 125 Class2 and headed to Class3 or Class4 into an SRv6 service policy to 126 Node B, via the firewall F1. As part of the steering process, Node A 127 identifies the source and destination classes, encapsulates the 128 traffic and attaches an SRH that contains the SR Policy SID-list, as 129 well as the class information in the SRH TLVs. The procedure to 130 identify the traffic classes is out of the scope of this document. 132 Node B is similarly configured to handle flows in the reverse 133 direction. 135 The firewall F1 reads the SRH TLVs and decides to forward or drop the 136 traffic based on the combination of the source and destination 137 classes. The availability of class metadata allows the firewall 138 rule-set size to scale with the number of valid (source class, 139 destination class) pairs. This drastically simplifies the firewall 140 configuration and operation compared to a traditional 5-tuple-based 141 model with tens of thousands of entries. 143 In Figure 2, a traffic flow from Class1 to Class3 is steered into the 144 SRv6 Policy "", where "B:F1:A::" represents a 145 service SID instantiated on the firewall F1 and "B:B:D3::" is an 146 End.DX4 SID on the egress node B that sends the inner packet to 147 Class3. The SRH "S-class" and "D-class" TLVs respectively represent 148 the source and destination class identifiers. This traffic flow is 149 allowed to traverse the firewall and reaches its final destination in 150 Class3. 152 +--------------------------------+ 153 | SRv6 domain | 154 | | 155 +-------+ +----+----+ +----------+ +----+----+ +-------+ 156 |Class1 |---| Node A | | F1 | | Node B |---|Class3 | 157 +-------+ |(ingress)|-----|(firewall)|-----|(egress) | +-------+ 158 +----+----+ +----------+ +----+----+ 159 --> | ---------------------> | --> 160 | | 161 +--------------------------------+ 163 +--------------+ +--------------+ +--------------+ +--------------+ 164 |IP4(10.0.1.12,| | IP6(A, F1) | | IP6(A, B) | |IP4(10.0.1.12,| 165 | 10.3.0.34)| +--------------+ +--------------+ | 10.3.0.34)| 166 +--------------+ |SRH(B:B:D3::, | |SRH(B:B:D3::, | +--------------+ 167 |B:F1:A::;SL=1;| |B:F1:A::;SL=0;| 168 | S-class=Cl1;| | S-class=Cl1;| 169 | D-class=Cl3)| | D-class=Cl3)| 170 +--------------+ +--------------+ 171 |IP4(10.0.1.12,| |IP4(10.0.1.12,| 172 | 10.3.0.34)| | 10.3.0.34)| 173 +--------------+ +--------------+ 175 Figure 2: Traffic flow from Class1 to Class3 177 In Figure 3, a traffic flow from Class2 to Class3 is steered into the 178 exact same SRv6 Policy "". The SRH "S-class" and 179 "D-class" TLVs are similarly populated with the source and 180 destination class identifiers. However, "S-class=Cl2" and 181 "D-class=Cl3" does not match an authorized class combination on the 182 firewall. The traffic is considered as invalid and dropped at F1. 184 +--------------------------------+ 185 | SRv6 domain | 186 | | 187 +-------+ +----+----+ +----------+ +----+----+ +-------+ 188 |Class2 |---| Node A | | F1 | | Node B |---|Class3 | 189 +-------+ |(ingress)|-----|(firewall)|-----|(egress) | +-------+ 190 +----+----+ +----------+ +----+----+ 191 --> | --------> X | 192 | | 193 +--------------------------------+ 195 +--------------+ +--------------+ 196 |IP4(10.0.1.12,| | IP6(A, F1) | 197 | 10.3.0.34)| +--------------+ 198 +--------------+ |SRH(B:B:D3::, | 199 |B:F1:A::;SL=1;| 200 | S-class=Cl2;| 201 | D-class=Cl3)| 202 +--------------+ 203 |IP4(10.0.1.12,| 204 | 10.3.0.34)| 205 +--------------+ 207 Figure 3: Traffic flow from Class2 to Class3 209 3. Demo availability 211 A working demo is available, using FD.io VPP [FDio] instances as 212 ingress and egress routers and the iptables-based SERA firewall 213 [SERA]. 215 4. IANA Considerations 217 To be updated. 219 5. Security Considerations 221 To be updated. 223 6. Acknowledgements 225 To be updated. 227 7. References 228 7.1. Normative References 230 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., 231 Decraene, B., Litkowski, S., and R. Shakir, "Segment 232 Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, 233 July 2018, . 235 [RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J., 236 Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header 237 (SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020, 238 . 240 7.2. Informative References 242 [FDio] "The Fast Data Project", The Linux Foundation , 2018, 243 . 245 [I-D.ietf-spring-sr-service-programming] 246 Clad, F., Xu, X., Filsfils, C., daniel.bernier@bell.ca, 247 d., Li, C., Decraene, B., Ma, S., Yadlapalli, C., 248 Henderickx, W., and S. Salsano, "Service Programming with 249 Segment Routing", draft-ietf-spring-sr-service- 250 programming-02 (work in progress), March 2020. 252 [I-D.ietf-spring-srv6-network-programming] 253 Filsfils, C., Camarillo, P., Leddy, J., Voyer, D., 254 Matsushima, S., and Z. Li, "SRv6 Network Programming", 255 draft-ietf-spring-srv6-network-programming-15 (work in 256 progress), March 2020. 258 [SERA] Abdelsalam, A., Salsano, S., Clad, F., Camarillo, P., and 259 C. Filsfils, "SERA: SEgment Routing Aware Firewall for 260 Service Function Chaining scenarios", IFIP Networking , 261 May 2018. 263 Authors' Addresses 265 James N Guichard (editor) 266 Futurewei Technologies Ltd. 268 Email: james.n.guichard@futurewei.com 270 Clarence Filsfils 271 Cisco Systems, Inc. 273 Email: cf@cisco.com 274 Daniel Bernier 275 Bell Canada 277 Email: daniel.bernier@bell.ca 279 Zhenbin Li 280 Huawei Technologies 282 Email: lizhenbin@huawei.com 284 Francois Clad (editor) 285 Cisco Systems, Inc. 287 Email: fclad@cisco.com 289 Pablo Camarillo 290 Cisco Systems, Inc. 292 Email: pcamaril@cisco.com 294 Ahmed AbdelSalam 295 Cisco Systems, Inc. 297 Email: ahabdels@cisco.com