Network Working Group L. Qin Internet-Draft D. Li Intended status: Informational J. Wu Expires: 13 May 2023 Tsinghua University L. Chen F. Gao Zhongguancun Laboratory 9 November 2022 SAVNET's Incentive Consideration for Defense Against Reflection Attacks draft-qin-savnet-incentive-02 Abstract Source address spoofing remains a significant challenge in today's Internet. Although source address validation (SAV) mechanisms, such as ingress filtering [RFC2827], unicast Reverse Path Forwarding (uRPF) [RFC3704], and the Enhanced Feasible-Path Unicast Reverse Path Forwarding (EFP-uRPF) [RFC8704], have been proposed for a long time, none of them have been widely deployed due to their limitation in accuracy, lack of incentive, or other cost concerns. This document specifically explains the incentive problem of existing SAV mechanisms and clarifies the direct incentive that SAVNET hopes to achieve. Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119][RFC8174] when, and only when, they appear in all capitals, as shown here. 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." Qin, et al. Expires 13 May 2023 [Page 1] Internet-Draft SAVNET Incentive November 2022 This Internet-Draft will expire on 13 May 2023. Copyright Notice Copyright (c) 2022 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 Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. The Importance of Direct Incentive for SAV Deployment . . . . 4 4. The Demand for Defense Against Reflection Attack . . . . . . 4 5. Incentive Comparison Between EFP-uRPF and SAVNET . . . . . . 5 5.1. Scenario 1 . . . . . . . . . . . . . . . . . . . . . . . 6 5.1.1. Case 1: only AS3 deploys SAV . . . . . . . . . . . . 6 5.1.2. Case 2: AS1 and AS3 deploy SAV . . . . . . . . . . . 7 5.1.3. Case 3: AS2 and AS3 deploy SAV . . . . . . . . . . . 8 5.1.4. Case 4: AS1, AS2, and AS3 deploy SAV . . . . . . . . 8 5.2. Scenario 2 . . . . . . . . . . . . . . . . . . . . . . . 9 5.2.1. Case 1: only AS3 deploys SAV . . . . . . . . . . . . 10 5.2.2. Case 2: AS1 and AS3 deploy SAV . . . . . . . . . . . 10 5.2.3. Case 3: AS2 and AS3 deploy SAV . . . . . . . . . . . 11 5.2.4. Case 4: AS1, AS2, and AS3 deploy SAV . . . . . . . . 11 5.3. Scenario 3 . . . . . . . . . . . . . . . . . . . . . . . 12 5.3.1. Case 1: only AS3 deploys SAV . . . . . . . . . . . . 13 5.3.2. Case 2: AS1 and AS3 deploy SAV . . . . . . . . . . . 13 5.3.3. Case 3: AS2 and AS3 deploy SAV . . . . . . . . . . . 14 5.3.4. Case 4: AS1, AS2, and AS3 deploy SAV . . . . . . . . 14 6. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 15 8. Normative References . . . . . . . . . . . . . . . . . . . . 15 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16 Qin, et al. Expires 13 May 2023 [Page 2] Internet-Draft SAVNET Incentive November 2022 1. Introduction Source address spoofing is one of the most important security threats in the Internet. By using forged source IP addresses, attackers can well hide their real identities and carry out various malicious attacks [RFC6959], among which reflection attack is the most common and harmful. In the reflection attack, the attacker spoofs the victim's source IP address and sends requests to servers with reflection and amplification functions, such as DNS or NTP servers. Upon receiving the requests, these servers will reply a large number of responses to the victim, resulting in a large-scale Distributed Denial of Service (DDoS) attack to the victim. To mitigate source address spoofing, several source address validation (SAV) mechanisms (e.g., ingress filtering [RFC2827], unicast Reverse Path Forwarding (uRPF) [RFC3704], and the Enhanced Feasible-Path Unicast Reverse Path Forwarding (EFP-uRPF) [RFC8704]) have been proposed to identify and reject traffic with forged source IP addresses. However, they have not been widely deployed due to their limitation in accuracy, lack of incentive, or other cost concerns. Source address spoofing remains a significant challenge in today's Internet. To help narrow the gap of existing SAV mechanisms, [draft-li-savnet-intra-domain-problem-statement] and [draft-wu-savnet-inter-domain-problem-statement] summarize the fundamental problems of existing SAV mechanisms and define the requirements for new SAV mechanisms. This document further explains the misaligned incentive problem of existing SAV mechanisms and specifies the direct incentive that SAVNET hopes to achieve. The direct incentive of SAV refers to a network deploying SAV can protect itself from being the victim of source address spoofing attacks, espacially the most important reflection attacks. 2. Terminology SAV: Source Address Validation, i.e. validating the authenticity of a packet's source IP address. Three roles in a reflection attack: * Attacker. A malicious host that spoofs the victim's source IP address when sending a request to the reflector. * Reflector. A reflective server (e.g., DNS or NTP server) that receives the forged request and responds to the victim. Qin, et al. Expires 13 May 2023 [Page 3] Internet-Draft SAVNET Incentive November 2022 * Victim. An innocent host that receives a lot of responses from the reflector, resulting in a DoS attack. Two results in the incentive comparison between EFP-uRPF and SAVNET: * "FAIL" means the victim network deploying SAV (EFP-uRPF or SAVNET) cannot help itself prevent the reflection attack. * "WORK" means the victim network deploying SAV (EFP-uRPF or SAVNET) can help itself prevent the reflection attack. 3. The Importance of Direct Incentive for SAV Deployment Ingress filtering, or BCP38 [RFC2827] requires the network to implement SAV filtering on its outgoing traffic. If all networks deploy BCP38 and only allow outgoing traffic with legitimate source addresses, source address spoofing can be effectively prevented. However, although BCP38 has been proposed for more than 20 years and is highly recommended by the Mutually Agreed Norms for Routing Security (MANRS), some ASes still do not deploy BCP38. One main reason is that operators lack incentive to deploy BCP38 in their networks. Specifically, BCP38 only prevents the AS who deploys SAV from originating spoofed traffic but does not protect the AS from receiving spoofed traffic or being the victim of an attack. The benefits from deploying BCP38 do not flow to the deployed network, but to the rest of the Internet. As a result, some ASes are reluctant to deploy BCP38 and prefer to wait for others to deploy. The deployment problem faced by BCP38 tells us that a good SAV mechanism must provide direct incentive/benefits to the deployed network. If a network deploys SAV but finds that it only helps other networks, the network will not be motivated to deploy SAV. If a network deploys SAV and finds that sometimes it can help itself (compared with not deploying), the network will be more motivated to deploy SAV. 4. The Demand for Defense Against Reflection Attack Nowadays, reflection attack has become one of the most common attacks based on source address spoofing. However, the victim network in a reflection attack may not receive the spoofed request. If an intermediate network deploys SAV to protect itself from being the victim of source address spoofing attacks, such as single-packet attacks, flood-based DoS, and etc [RFC6959], it can help prevent the reflection attack when receiving the spoofed request. Therefore, to mitigate reflection attacks, customer or user networks are increasingly asking their upstreaming providers to deploy SAV as close to the source as possible and to protect their source addresses Qin, et al. Expires 13 May 2023 [Page 4] Internet-Draft SAVNET Incentive November 2022 from being forged. Considering the security demand of customer or user networks, network operators would be willing to improve their competitiveness by providing defense against reflection attacks, so they will attract more users and gain more profits. However, BCP38 is not aligned with the demand for defense against reflection attacks. The operator who deploys BCP38 neither protects itself from receiving spoofed traffic nor protects its customer or user networks from reflection attacks. More recently, RFC8704 or BCP84 [RFC8704] proposes the Enhanced Feasible-Path Unicast Reverse Path Forwarding (EFP-uRPF) and recommends operators to adopt EFP-uRPF at customer interfaces in most inter-domain scenarios. Different from BCP38, EFP-uRPF provides some direct incentive, as it aims to protect the deployed AS from receiving spoofed traffic from customer interfaces. Nonetheless, EFP-uRPF is essentially performing ingress filtering at a higher aggregation point (i.e., the top AS of a customer cone). It only validates traffic from customer interfaces but does not validate traffic from provider and peer interfaces. The operator who deploys EFP-uRPF only prevents its customer cone from originating spoofed traffic, but does not protect the customer cone from receiving spoofed traffic or being the victim of a reflection attack from outside the customer cone. Moreover, the victim network will not gain additional protection against reflection attack even if it also deploys EFP-uRPF. Therefore, EFP-uRPF cannot perfectly meet the demand for defense against reflection attacks. 5. Incentive Comparison Between EFP-uRPF and SAVNET In the following, we use reflection attack as an example to measure the incentive that EFP-uRPF or SAVNET can provide to the victim network. We simplify the participants in a reflection attack into three roles (attacker network, reflector network, and victim network) and enumerate three attack scenarios by changing the relative positions of the three roles. In each scenario, we suppose the victim network always deploys SAV mechanism (EFP-uRPF or SAVNET), because only the victim can get benefit from the SAV mechanism. Then, for any deployment case of the other two networks (i.e., attacker network and reflector network), we check whether the reflection attack can be prevented. If so, the victim network has strong motivation to deploy SAV; if not, the victim network has weak motivation to deploy SAV. Since there is no specific SAVNET solution yet, we assume SAVNET can meet the following requirements: * Validate traffic from all directions. Qin, et al. Expires 13 May 2023 [Page 5] Internet-Draft SAVNET Incentive November 2022 * Match the real data-plane forwarding path originated from each deployed AS. 5.1. Scenario 1 Figure 1 shows the first reflection attack scenario where the reflector network is located between the attacker network and the victim network. The attacker spoofs the source address of the victim and sends a forged request to the reflector. After receiving the request from attacker, the reflector responds to the victim. +---------+ | AS2 +-+Reflector ++/\+-----+ / \ request / \ response / \ / \ +---------+ +-+\/+----+ Attacker+-+ AS1 | | AS3 +-+ Victim +---------+ +---------+ AS1: Attacker network AS2: Reflector network AS3: Victim network Figure 1: The first reflection attack scenario. 5.1.1. Case 1: only AS3 deploys SAV +==============+==============+===========+===========+========+ | Relationship | Relationship | EFP-uRPF | EFP-uRPF | SAVNET | | between AS1 | between AS2 | algorithm | algorithm | | | and AS2 | and AS3 | A | B | | +==============+==============+===========+===========+========+ | P2C | P2C | FAIL | FAIL | FAIL | +--------------+--------------+-----------+-----------+--------+ | P2P | P2C | FAIL | FAIL | FAIL | +--------------+--------------+-----------+-----------+--------+ | C2P | C2P | FAIL | FAIL | FAIL | +--------------+--------------+-----------+-----------+--------+ | C2P | P2P | FAIL | FAIL | FAIL | +--------------+--------------+-----------+-----------+--------+ | C2P | P2C | FAIL | FAIL | FAIL | +--------------+--------------+-----------+-----------+--------+ Qin, et al. Expires 13 May 2023 [Page 6] Internet-Draft SAVNET Incentive November 2022 Table 1: All SAV mechanisms fail if only AS3 deploys SAV in scenario 1 Table 1 shows the effectiveness of EFP-uRPF and SAVNET against the reflection attack under different relationships among AS1, AS2, and AS3. We omit combinations of relationships that violate valley-free principle. If only the victim network deploys SAV, both EFP-uRPF and SAVNET fail to prevent the reflection attack in scenario 1, because the victim network does not receive the forged request at all. 5.1.2. Case 2: AS1 and AS3 deploy SAV +==============+==============+===========+===========+========+ | Relationship | Relationship | EFP-uRPF | EFP-uRPF | SAVNET | | between AS1 | between AS2 | algorithm | algorithm | | | and AS2 | and AS3 | A | B | | +==============+==============+===========+===========+========+ | P2C | P2C | FAIL | FAIL | WORK | +--------------+--------------+-----------+-----------+--------+ | P2P | P2C | FAIL | FAIL | WORK | +--------------+--------------+-----------+-----------+--------+ | C2P | C2P | FAIL | FAIL | WORK | +--------------+--------------+-----------+-----------+--------+ | C2P | P2P | FAIL | FAIL | WORK | +--------------+--------------+-----------+-----------+--------+ | C2P | P2C | FAIL | FAIL | WORK | +--------------+--------------+-----------+-----------+--------+ Table 2: SAVNET works best if AS1 and AS3 deploy SAV in scenario 1 Table 2 shows that SAVNET works best when victim network and attacker network deploy SAV. If AS1 and AS3 deploy SAVNET, AS1 learns that traffic with victim's source address must come from outside the AS, not inside the AS. Therefore, SAVNET in AS1 can successfully detect the forged request and prevent the reflection attack. However, since EFP-uRPF in AS1 does not verify outgoing traffic, EFP-uRPF fails in this deployment case. Qin, et al. Expires 13 May 2023 [Page 7] Internet-Draft SAVNET Incentive November 2022 5.1.3. Case 3: AS2 and AS3 deploy SAV +==============+==============+===========+===========+========+ | Relationship | Relationship | EFP-uRPF | EFP-uRPF | SAVNET | | between AS1 | between AS2 | algorithm | algorithm | | | and AS2 | and AS3 | A | B | | +==============+==============+===========+===========+========+ | P2C | P2C | FAIL | FAIL | WORK | +--------------+--------------+-----------+-----------+--------+ | P2P | P2C | FAIL | FAIL | WORK | +--------------+--------------+-----------+-----------+--------+ | C2P | C2P | WORK | WORK | WORK | +--------------+--------------+-----------+-----------+--------+ | C2P | P2P | WORK | WORK | WORK | +--------------+--------------+-----------+-----------+--------+ | C2P | P2C | WORK | FAIL | WORK | +--------------+--------------+-----------+-----------+--------+ Table 3: SAVNET works best if AS2 and AS3 deploy SAV in scenario 1 As shown in Table 3, SAVNET works best when victim network and reflector network deploy SAV. If AS2 and AS3 deploy SAVNET, AS2 learns that traffic with victim's source address must come from AS3, so it will block the forged request from AS1. If AS2 and AS3 deploy EFP-uRPF, since EFP-uRPF only work for traffic from customer interfaces, EFP-uRPF algorithm A and algorithm B both fail when AS1 is the provider/peer of AS2. EFP-uRPF algorithm A works well when AS1 is the customer of AS2, but EFP-uRPF algorithm B still fails when AS1 and AS3 are both in the customer cone of AS2, because EFP-uRPF algorithm B cannot identify source address spoofing between ASes in customer cone. 5.1.4. Case 4: AS1, AS2, and AS3 deploy SAV +==============+==============+===========+===========+========+ | Relationship | Relationship | EFP-uRPF | EFP-uRPF | SAVNET | | between AS1 | between AS2 | algorithm | algorithm | | | and AS2 | and AS3 | A | B | | +==============+==============+===========+===========+========+ | P2C | P2C | FAIL | FAIL | WORK | +--------------+--------------+-----------+-----------+--------+ | P2P | P2C | FAIL | FAIL | WORK | +--------------+--------------+-----------+-----------+--------+ | C2P | C2P | WORK | WORK | WORK | +--------------+--------------+-----------+-----------+--------+ Qin, et al. Expires 13 May 2023 [Page 8] Internet-Draft SAVNET Incentive November 2022 | C2P | P2P | WORK | WORK | WORK | +--------------+--------------+-----------+-----------+--------+ | C2P | P2C | WORK | FAIL | WORK | +--------------+--------------+-----------+-----------+--------+ Table 4: SAVNET works best if AS1, AS2, and AS3 deploy SAV in scenario 1 In scenario 1, SAVNET still works best when all three roles deploy SAV. When they deploy SAVNET, both AS1 and AS2 can effectively identify and block the forged request. When they deploy EFP-uRPF, only AS2 sometimes can prevent the reflection attack, with the same results as Section 4.1.3. 5.2. Scenario 2 Figure 2 shows the second reflection attack scenario. In scenario 2, the victim network is located between the attack network and the reflector network. When attacker sends a forged request to the reflector, the request first arrives at the victim network and then be forwarded to the reflector network. Subsequently, the reflector responds to the victim. +---------+ | AS3 +-+Victim ++/\+--+/\+ / \ \ / \ \ /request \ \ response / \ \ +---------+ + \/+-----+ Attacker+-+ AS1 | | AS2 +-+Reflector +---------+ +---------+ AS1: Attacker network AS2: Reflector network AS3: Victim network Figure 2: The second reflection attack scenario. Qin, et al. Expires 13 May 2023 [Page 9] Internet-Draft SAVNET Incentive November 2022 5.2.1. Case 1: only AS3 deploys SAV +==============+==============+===========+===========+========+ | Relationship | Relationship | EFP-uRPF | EFP-uRPF | SAVNET | | between AS1 | between AS3 | algorithm | algorithm | | | and AS3 | and AS2 | A | B | | +==============+==============+===========+===========+========+ | P2C | P2C | FAIL | FAIL | WORK | +--------------+--------------+-----------+-----------+--------+ | P2P | P2C | FAIL | FAIL | WORK | +--------------+--------------+-----------+-----------+--------+ | C2P | C2P | WORK | WORK | WORK | +--------------+--------------+-----------+-----------+--------+ | C2P | P2P | WORK | WORK | WORK | +--------------+--------------+-----------+-----------+--------+ | C2P | P2C | WORK | WORK | WORK | +--------------+--------------+-----------+-----------+--------+ Table 5: SAVNET works best if only AS3 deploys SAV in scenario 2 Table 5 shows the effectiveness of EFP-uRPF and SAVNET when only AS3 in scenario 2 deploys SAV. If AS3 deploys SAVNET, it can reject the forged request when it receives the forged request. If AS3 deploys EFP-uRPF, it only works when AS1 is the customer of AS3 because EFP- uRPF only implements SAV filtering at customer interfaces. We also compare EFP-uRPF and SAVNET in the following three deployment cases. We find that if the SAV mechanism is EFP-uRPF algorithm A or EFP-uRPF algorithm B, only the victim network in scenario 2 has the possibility to reject the forged request by implementing SAV. Even if attacker network or reflector network also deploys EFP-uRPF, it does not provide additional assistance to victim network. Therefore, on the basis that the victim network has deployed SAV, SAVNET always works best in different deployment cases. 5.2.2. Case 2: AS1 and AS3 deploy SAV +==============+==============+===========+===========+========+ | Relationship | Relationship | EFP-uRPF | EFP-uRPF | SAVNET | | between AS1 | between AS3 | algorithm | algorithm | | | and AS3 | and AS2 | A | B | | +==============+==============+===========+===========+========+ | P2C | P2C | FAIL | FAIL | WORK | +--------------+--------------+-----------+-----------+--------+ | P2P | P2C | FAIL | FAIL | WORK | +--------------+--------------+-----------+-----------+--------+ Qin, et al. Expires 13 May 2023 [Page 10] Internet-Draft SAVNET Incentive November 2022 | C2P | C2P | WORK | WORK | WORK | +--------------+--------------+-----------+-----------+--------+ | C2P | P2P | WORK | WORK | WORK | +--------------+--------------+-----------+-----------+--------+ | C2P | P2C | WORK | WORK | WORK | +--------------+--------------+-----------+-----------+--------+ Table 6: SAVNET works best if AS1 and AS3 deploy SAV in scenario 2 5.2.3. Case 3: AS2 and AS3 deploy SAV +==============+==============+===========+===========+========+ | Relationship | Relationship | EFP-uRPF | EFP-uRPF | SAVNET | | between AS1 | between AS3 | algorithm | algorithm | | | and AS3 | and AS2 | A | B | | +==============+==============+===========+===========+========+ | P2C | P2C | FAIL | FAIL | WORK | +--------------+--------------+-----------+-----------+--------+ | P2P | P2C | FAIL | FAIL | WORK | +--------------+--------------+-----------+-----------+--------+ | C2P | C2P | WORK | WORK | WORK | +--------------+--------------+-----------+-----------+--------+ | C2P | P2P | WORK | WORK | WORK | +--------------+--------------+-----------+-----------+--------+ | C2P | P2C | WORK | WORK | WORK | +--------------+--------------+-----------+-----------+--------+ Table 7: SAVNET works best if AS2 and AS3 deploy SAV in scenario 2 5.2.4. Case 4: AS1, AS2, and AS3 deploy SAV +==============+==============+===========+===========+========+ | Relationship | Relationship | EFP-uRPF | EFP-uRPF | SAVNET | | between AS1 | between AS3 | algorithm | algorithm | | | and AS3 | and AS2 | A | B | | +==============+==============+===========+===========+========+ | P2C | P2C | FAIL | FAIL | WORK | +--------------+--------------+-----------+-----------+--------+ | P2P | P2C | FAIL | FAIL | WORK | +--------------+--------------+-----------+-----------+--------+ | C2P | C2P | WORK | WORK | WORK | +--------------+--------------+-----------+-----------+--------+ | C2P | P2P | WORK | WORK | WORK | +--------------+--------------+-----------+-----------+--------+ Qin, et al. Expires 13 May 2023 [Page 11] Internet-Draft SAVNET Incentive November 2022 | C2P | P2C | WORK | WORK | WORK | +--------------+--------------+-----------+-----------+--------+ Table 8: SAVNET works best if AS1, AS2, and AS3 deploy SAV in scenario 2 5.3. Scenario 3 Figure 3 shows the third reflection attack scenario. The attacker network is located between the victim network and the reflector network. Attacker spoofs victim's source address in the request sent to reflector. Reflector receives the request from the attacker network and sends a response to the victim network via the attacker network. Below we make the incentive comparison between EFP-uRPF and SAVNET in scenario 3. By varying SAV deployment status of attacker network and reflector network, we find all SAV mechanisms fail in preventing the reflection attack in this scenario. For victim network, it does not receive the forged request. For attacker network and reflector network, SAV in their networks cannot identify this spoofing because the forged source address (i.e., victim's source address) shares the same valid incoming interface with the actual one (i.e., attacker's source address). +---------+ | AS1 +-+Attacker +----+/\+-+ / \ \ / \ \ /response\ \request / \ \ +----+\/+-+ +--+\/+---+ Victim+-+ AS3 | | AS2 +-+Reflector +---------+ +---------+ AS1: Attacker network AS2: Reflector network AS3: Victim network Figure 3: The third reflection attack scenario. Qin, et al. Expires 13 May 2023 [Page 12] Internet-Draft SAVNET Incentive November 2022 5.3.1. Case 1: only AS3 deploys SAV +==============+==============+===========+===========+========+ | Relationship | Relationship | EFP-uRPF | EFP-uRPF | SAVNET | | between AS3 | between AS1 | algorithm | algorithm | | | and AS1 | and AS2 | A | B | | +==============+==============+===========+===========+========+ | P2C | P2C | FAIL | FAIL | FAIL | +--------------+--------------+-----------+-----------+--------+ | P2P | P2C | FAIL | FAIL | FAIL | +--------------+--------------+-----------+-----------+--------+ | C2P | C2P | FAIL | FAIL | FAIL | +--------------+--------------+-----------+-----------+--------+ | C2P | P2P | FAIL | FAIL | FAIL | +--------------+--------------+-----------+-----------+--------+ | C2P | P2C | FAIL | FAIL | FAIL | +--------------+--------------+-----------+-----------+--------+ Table 9: All SAV mechanisms fail if only AS3 deploys SAV in scenario 3 5.3.2. Case 2: AS1 and AS3 deploy SAV +==============+==============+===========+===========+========+ | Relationship | Relationship | EFP-uRPF | EFP-uRPF | SAVNET | | between AS3 | between AS1 | algorithm | algorithm | | | and AS1 | and AS2 | A | B | | +==============+==============+===========+===========+========+ | P2C | P2C | FAIL | FAIL | FAIL | +--------------+--------------+-----------+-----------+--------+ | P2P | P2C | FAIL | FAIL | FAIL | +--------------+--------------+-----------+-----------+--------+ | C2P | C2P | FAIL | FAIL | FAIL | +--------------+--------------+-----------+-----------+--------+ | C2P | P2P | FAIL | FAIL | FAIL | +--------------+--------------+-----------+-----------+--------+ | C2P | P2C | FAIL | FAIL | FAIL | +--------------+--------------+-----------+-----------+--------+ Table 10: All SAV mechanisms fail if AS1 and AS3 deploy SAV in scenario 3 Qin, et al. Expires 13 May 2023 [Page 13] Internet-Draft SAVNET Incentive November 2022 5.3.3. Case 3: AS2 and AS3 deploy SAV +==============+==============+===========+===========+========+ | Relationship | Relationship | EFP-uRPF | EFP-uRPF | SAVNET | | between AS3 | between AS1 | algorithm | algorithm | | | and AS1 | and AS2 | A | B | | +==============+==============+===========+===========+========+ | P2C | P2C | FAIL | FAIL | FAIL | +--------------+--------------+-----------+-----------+--------+ | P2P | P2C | FAIL | FAIL | FAIL | +--------------+--------------+-----------+-----------+--------+ | C2P | C2P | FAIL | FAIL | FAIL | +--------------+--------------+-----------+-----------+--------+ | C2P | P2P | FAIL | FAIL | FAIL | +--------------+--------------+-----------+-----------+--------+ | C2P | P2C | FAIL | FAIL | FAIL | +--------------+--------------+-----------+-----------+--------+ Table 11: All SAV mechanisms fail if AS2 and AS3 deploy SAV in scenario 3 5.3.4. Case 4: AS1, AS2, and AS3 deploy SAV +==============+==============+===========+===========+========+ | Relationship | Relationship | EFP-uRPF | EFP-uRPF | SAVNET | | between AS3 | between AS1 | algorithm | algorithm | | | and AS1 | and AS2 | A | B | | +==============+==============+===========+===========+========+ | P2C | P2C | FAIL | FAIL | FAIL | +--------------+--------------+-----------+-----------+--------+ | P2P | P2C | FAIL | FAIL | FAIL | +--------------+--------------+-----------+-----------+--------+ | C2P | C2P | FAIL | FAIL | FAIL | +--------------+--------------+-----------+-----------+--------+ | C2P | P2P | FAIL | FAIL | FAIL | +--------------+--------------+-----------+-----------+--------+ | C2P | P2C | FAIL | FAIL | FAIL | +--------------+--------------+-----------+-----------+--------+ Table 12: All SAV mechanisms fail if AS1, AS2, and AS3 deploy SAV in scenario 3 Qin, et al. Expires 13 May 2023 [Page 14] Internet-Draft SAVNET Incentive November 2022 6. Summary Overall, neither SAVNET nor EFP-uRPF completely prevents the reflection attack. But for any attack scenario or deployment case, we find that SAVNET is doing better or not worse than EFP-uRPF. It is worth noting that AS1 and AS2 in above scenarios can also be targets of reflection attacks from other networks. Therefore, a network has more incentive to deploy SAVNET as the SAV mechanism, because its own network will have high probability of being protected against reflection attacks. 7. Acknowledgments TBD 8. Normative References [draft-li-savnet-intra-domain-problem-statement] Li, D., Wu, J., Qin, L., Huang, M., and N. Geng, "Source Address Validation in Intra-domain Networks (Intra-domain SAVNET) Gap Analysis, Problem Statement and Requirements", 7 November 2022. [draft-wu-savnet-inter-domain-problem-statement] Wu, J., Li, D., Qin, L., Huang, M., and N. Geng, "Source Address Validation in Inter-domain Networks (Inter-domain SAVNET) Gap Analysis, Problem Statement and Requirements", 7 November 2022. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC2827] Ferguson, P. and D. Senie, "Network Ingress Filtering: Defeating Denial of Service Attacks which employ IP Source Address Spoofing", BCP 38, RFC 2827, DOI 10.17487/RFC2827, May 2000, . [RFC3704] Baker, F. and P. Savola, "Ingress Filtering for Multihomed Networks", BCP 84, RFC 3704, DOI 10.17487/RFC3704, March 2004, . [RFC6959] McPherson, D., Baker, F., and J. Halpern, "Source Address Validation Improvement (SAVI) Threat Scope", RFC 6959, DOI 10.17487/RFC6959, May 2013, . Qin, et al. Expires 13 May 2023 [Page 15] Internet-Draft SAVNET Incentive November 2022 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC8704] Sriram, K., Montgomery, D., and J. Haas, "Enhanced Feasible-Path Unicast Reverse Path Forwarding", BCP 84, RFC 8704, DOI 10.17487/RFC8704, February 2020, . Authors' Addresses Lancheng Qin Tsinghua University Beijing China Email: qlc19@mails.tsinghua.edu.cn Dan Li Tsinghua University Beijing China Email: tolidan@tsinghua.edu.cn Jianping Wu Tsinghua University Beijing China Email: jianping@cernet.edu.cn Li Chen Zhongguancun Laboratory Beijing China Email: Lichen@zgclab.edu.cn Fang Gao Zhongguancun Laboratory Beijing China Email: gaofang@zgclab.edu.cn Qin, et al. Expires 13 May 2023 [Page 16]