SAVNET's Incentive Consideration for Defense Against Reflection Attacks
draft-qin-savnet-incentive-02
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| Authors | Lancheng Qin , Dan Li , Jianping Wu , Li Chen , Fang Gao | ||
| Last updated | 2022-11-08 | ||
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draft-qin-savnet-incentive-02
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."
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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/
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Please review these documents carefully, as they describe your rights
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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
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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.
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* 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
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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.
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* 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 |
+--------------+--------------+-----------+-----------+--------+
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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.
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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 |
+--------------+--------------+-----------+-----------+--------+
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| 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.
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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 |
+--------------+--------------+-----------+-----------+--------+
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| 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 |
+--------------+--------------+-----------+-----------+--------+
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| 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.
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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
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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
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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,
<https://www.rfc-editor.org/info/rfc2119>.
[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, <https://www.rfc-editor.org/info/rfc2827>.
[RFC3704] Baker, F. and P. Savola, "Ingress Filtering for Multihomed
Networks", BCP 84, RFC 3704, DOI 10.17487/RFC3704, March
2004, <https://www.rfc-editor.org/info/rfc3704>.
[RFC6959] McPherson, D., Baker, F., and J. Halpern, "Source Address
Validation Improvement (SAVI) Threat Scope", RFC 6959,
DOI 10.17487/RFC6959, May 2013,
<https://www.rfc-editor.org/info/rfc6959>.
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[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[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,
<https://www.rfc-editor.org/info/rfc8704>.
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
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