Internet DRAFT - draft-cheng-savnet-proactive-defense-network
draft-cheng-savnet-proactive-defense-network
Network Working Group W. Cheng
Internet-Draft China Mobile
Intended status: Informational N. Geng
Expires: 21 April 2024 Huawei
D. Li
Tsinghua University
S. Yue
China Mobile
19 October 2023
Network Proactive Defense based on Source Address Validation
draft-cheng-savnet-proactive-defense-network-01
Abstract
Source address validation (SAV) helps routers check the validity of
packets. Networks can use the SAV capability to enhance threat
awareness. This document proposes proactive defense network where
routers can directly identify threats through SAV. The proactive
threat awareness feature is helpful for satisfying the threat
awareness requirement of ISPs.
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
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Internet-Drafts are draft documents valid for a maximum of six months
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on 21 April 2024.
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Copyright Notice
Copyright (c) 2023 IETF Trust and the persons identified as the
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Proactive Defense Network Architecture . . . . . . . . . . . 4
3. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1. Security Situational Awareness . . . . . . . . . . . . . 5
3.2. Security Services for Customers . . . . . . . . . . . . . 6
3.3. Attack Source Tracing . . . . . . . . . . . . . . . . . . 6
3.4. Path Protection for Important Traffic . . . . . . . . . . 6
3.5. Accurate SAV Rule Generation . . . . . . . . . . . . . . 6
3.6. Entire Network Security Planning . . . . . . . . . . . . 7
4. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 7
5. Deployment Considerations . . . . . . . . . . . . . . . . . . 8
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
7. Security Considerations . . . . . . . . . . . . . . . . . . . 8
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
9.1. Normative References . . . . . . . . . . . . . . . . . . 8
9.2. Informative References . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
Source address spoofing is one of the important security threats to
the Internet. Many attacks, such as flood-based DoS, reflective
attacks and spoof-based worm/malware propagation [RFC6959][netscout],
are based on spoofed source addresses. These attacks harm both ISPs'
and customers' networks. The ISPs' bandwidth may be drained, which
impacts customers' services. Some malicious traffic can traverse the
ISP network and directly attack the customer network. The attacks
bring great economic losses to both ISPs and customers. Besides,
spoofed source addresses make it hard to tracing the attackers. ISPs
have the requirement to detect the threats of source address spoofing
throughout the networks so that they can better defend themselves and
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guarantee the services.
To meet the threat awareness requirement, firewalls, DPI devices, or
anti-DDoS systems can be deployed at the IDC entrance or the trunk
interface to sense and intercept attack traffic including source
address spoofing traffic. However, the requirement of ISPs cannot be
fully met. These methods are single-point ones which are lack of
network-level view. Threats are usually identified through big data
analysis, which inevitably brings challenges to recall, accuracy, and
timeliness, and makes source tracing difficult. Since routers are
not directly involved in defending networks, the methods can only
provide out-of-band reactive threat awareness.
Route-based source address validation (SAV)
[RFC2827][RFC3704][RFC8704] enables network routers to detect source
address spoofing attacks. The SAV mechanisms can help routers
configure or generate SAV rules which indicate the valid incoming
interfaces of source addresses. When a packet arrives, the validity
of the packet will be checked by the rules. The router with SAV
rules installed can validate packets locally without the assistance
of an external device. Any router in the network (mostly edge
routers and aggregation routers) can conduct packet validation
[manrs-antispoofing][nist-rec] and detect packets with spoofed source
addresses in a real-time manner.
By deploying SAV, the network can have the capability of proactive
defense, which is named as proactive defense network (PDN) in this
document. In a PDN, routers can directly identify threats through
SAV. The proactive threat awareness feature is much helpful for
satisfying the threat awareness requirement of ISPs.
To efficiently discover threats and inform operators, routers need to
automatically generate accurate SAV rules for validation and report
threat information in real time to the security analysis center for
further analysis [sav-table]. The threats reported by routers can be
treated as a complementary to the previously mentioned single-point
methods. Together with the single-point methods, network proactive
threat awareness based on SAV can help ISPs obtain more accurate
threat awareness results at the entire network level and help make
more proper defense actions.
This document describes the PDN architecture as well as the use
cases, requirements, and deployment considerations.
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2. Proactive Defense Network Architecture
Figure 1 presents the SAV-based proactive defense network
architecture. In the architecture, the security analysis center is
connected to the routers that deploy SAV in the local network.
At the beginning, the routers need to get SAV rules installed in
advance. The SAV mechanisms can be enabled on routers to generate
SAV rules automatically. The rules can also be configured manually
through management tools like YANG [sav-yang].
The packets passing through the router will be checked. If the check
result is invalid or unknown, the router samples the packets and
reports them to the center. At the same time, the router records the
validation statistics, e.g., the total number of invalid packets
received from an interface. These statistics can also be reported.
The reported data can efficiently help ISPs do network proactive
threat awareness. It should be noted that the router may choose to
directly take further actions (e.g., dropping, permitting, rate
limiting, etc.) on the packet with invalid validation or wait for
further instructions from the center. It's up to the configurations
of operators.
The center collects and analyzes the threat data reported by the
routers. The data may be consolidated with those from other data
sources (e.g., anti-DDoS devices) to provide a global view on network
threats. Based on this view, further filtering operations can be
performed, and SAV rules updates can also be conducted by the central
center. The architecture supports a closed-loop security protection
workflow consisting of threat awareness, threat analysis, and threat
elimination as shown in Figure 1.
+-------------------+
| Security Analysis | Step2: threat analysis
| Center |
+--#-----#--------#-+
Step1: report / | \ Step3: threat elimination
threat data / | ... \ instructions
+-------------/--------|-----------\--------------+
| AS / | \ |
| +--------#--+ +-----#-----+ ... +#----------+ |
| |SAV Router1| |SAV Router2| ... |SAV RouterN| |
| +-----------+ +-----------+ ... +-----------+ |
+-------------------------------------------------+
Figure 1: Network proactive threat awareness architecture
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The architecture works without requiring the full deployment of SAV
on routers. Even only partial routers enable SAV at the particular
interfaces, network proactive threat awareness can still take effect
and provides valuable threat data for the security analysis center.
Besides, this architecture has some tolerance for the accuracy of SAV
rules. Different SAV mechanisms have different application scenarios
and are constantly evolving. In some special scenarios, such as
asymmetric routing, route convergence, and failure scenarios, the SAV
accuracy cannot be guaranteed. Even so, network proactive threat
awareness can still detect the existence of potential/ongoing
threats. Therefore, operators can install some tentative SAV rules
whose accuracy cannot be guaranteed. The tentative rules can be used
for monitoring the packets with the particular source addresses and
usually take a conservative action to invalid packets (e.g., only
sampling invalid packets but not dropping).
Overall, the architecture has no strict requirements for SAV
deployment and accuracy guarantees of SAV rules. The incomplete and
flawed threat data can still provide important reference for the
security analysis center. By consolidating the threat data from
network proactive threat awareness and other threat awareness tools,
the center can have a good view of network security situation.
Although the SAV deployment and accuracy guarantees are not strictly
required, there are some requirements on the networks. The
requirements ensure that the architecture works normally or is fully
utilized for threat awareness. See Section 4 for more details of
these requirements.
3. Use Cases
This section will introduce some SAV use cases for proactive defense
network architecture.
3.1. Security Situational Awareness
Network routers can proactively and quickly detect attack packets
with spoofed source addresses and report the threat data to the
security analysis center. The center can obtain interface/router-
based statistics and the sampled data packets. These data are
helpful for operators understanding the current situation of network
security and visualizing network threats.
Compared with only relying on single-point and reactive defense
methods, ISPs can get more accurate, complete, and real-time threat
information by using network proactive threat awareness. The
information will greatly help ISPs better defend their networks.
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3.2. Security Services for Customers
The threat awareness capability of the network enables the ISP to
fully understand the source address spoofing attacks on the network.
Therefore, when an attack occurs, the ISP can provide warnings for
the customer network to help customers better cope with the attack
traffic. In addition, ISPs can provide customers with the services
of attack traffic blocking/rate-limiting and provide different
service levels. Customers can choose to purchase the appropriate
service. When an ISP detects the attack to a customer, the ISP
preferentially allocates some network resources to the customer who
purchase services and intercepts attack traffic at the upstream
routers. Such security services can help reduce the impact of
attacks on customers' networks, which also enhances ISPs'
competitiveness.
3.3. Attack Source Tracing
The threat information can be used to locate the attack's entrance to
the local threat awareness network, i.e., attack source tracing. O&M
and troubleshooting costs are reduced. Besides, the ISP can carry
out near source filtering on the entrance router interface which is
the closest point to the attack source in the network. Near source
filtering blocks attack traffic as soon as possible and thus
minimizes the effects of the attack to the network.
3.4. Path Protection for Important Traffic
Source address validation limits the incoming directions of source
addresses, which can be leverage to limited the forwarding path of
the traffic from specific sources. By installing tailored SAV rules
on routers, proactive defense network can monitor whether the target
traffic traverses the pre-defined forwarding paths.
3.5. Accurate SAV Rule Generation
Generating accurate SAV rules can be a challenging problem by using a
completely distributed manner like uRPF. The security analysis
center in the proactive defense network can help collect SAV-related
information over the network, generate accurate SAV rules, and
install them into the routers' data planes. This is a kind of
centralized SAV rule generation method, which can be a complementary
of existing distributed SAV mechanisms.
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3.6. Entire Network Security Planning
Proactive defense network can help ISPs learn which types of attacks
are predominant, from which directions are more frequent, and which
target networks are frequently attacked. This kind of information
provides reference for entire network security planning. For
example, security analysis center can pre-install tentative rules for
monitoring/blocking/limiting/redirecting the particular traffic, so
that the attack traffic can be properly processed immediately.
4. Requirements
The networks for proactive defense network need to meet the following
requirements:
* Complete SAV rule generation capability. Network routers SHOULD
be able to automatically generate accurate SAV rules to form a
complete SAV table. A tool should also be provided to implement
remote configuration of SAV rules so that the center have the
capability to install/update the rules on routers. Besides, the
rule generation mechanism SHOULD cover various scenarios including
single-homing subnets/ASes, multi-homing subnets/ASes, internal
aggregation points, the Internet interfaces, etc.
* Accurate and scalable SAV rule expression. Directly using FIB for
SAV like uRPF is not enough for achieving accurate validation in
the data plane. ACL-based filtering provides the capability of
accurate SAV rule expression but faces significant scalability
problems. The hardware may need to be optimized to support
accurate and scalable SAV rule expression so that the routers in
the proactive defense network can efficiently detect network
threats.
* Flexible validation mode. Interface-based source prefix
allowlists are preferred as SAV rules, under which the validation
is strict and unknown prefixes are blocked. When such allowlists
are hard to be obtained (e.g., at the Internet interfaces),
interface-based source prefix blocklists or prefix-based interface
allowlists SHOULD be generated as SAV rules which focus on
checking specific prefixes and ignore unknown prefixes
[sav-table].
* Configurable actions to validated packets. Routers can check
packets with spoofed source addresses in real time based on the
SAV table and proactively report statistics and packet
information. Various actions, such as sampling, rate limiting,
discarding, and traffic redirecting, SHOULD be supported for
packets with different validation results [sav-table].
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5. Deployment Considerations
ISPs are very careful when deploying SAV. There exist risks that SAV
may cause network interruption and negative impacts on the customers'
networks. Therefore, the phased deployment is likely to be adopted.
Gradually enabling SAV for threat awareness and elimination can be
much helpful for ISPs to reduce the risks of network incidents. The
following shows a possible strategy of the phased deployment.
* Phase 1: Only focus on threat awareness by enabling SAV on
specified interfaces. Threat elimination actions will be seldom
taken.
* Phase 2: Support threat awareness by enabling SAV on all important
interfaces, and routers can take threat elimination actions
explicitly instructed by operators or the security analysis
center.
* Phase 3: Taking on threat awareness by fully enabling SAV in the
network, and routers can take threat elimination actions directly
(e.g., dropping or rate limiting invalid packets directly). The
routers will also coordinate with the security analysis center for
achieving an automatic proactive defense system.
6. IANA Considerations
This document makes no request of IANA.
7. Security Considerations
TBD
8. Acknowledgements
Much thanks for the contributions from: Mingqing Huang and Ce Zheng.
9. References
9.1. Normative References
[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>.
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[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>.
[RFC5635] Kumari, W. and D. McPherson, "Remote Triggered Black Hole
Filtering with Unicast Reverse Path Forwarding (uRPF)",
RFC 5635, DOI 10.17487/RFC5635, August 2009,
<https://www.rfc-editor.org/info/rfc5635>.
[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>.
[sav-table]
"Source Address Validation Table Abstraction and
Application", 2022, <https://datatracker.ietf.org/doc/
draft-huang-savnet-sav-table/>.
9.2. Informative References
[manrs-antispoofing]
MANRS, "MANRS Implementation Guide", 2023,
<https://www.manrs.org/netops/guide/antispoofing/>.
[netscout] NETSCOUT, "DDoS THREAT INTELLIGENCE REPORT", 2023,
<https://www.netscout.com/threatreport>.
[nist-rec] Sriram, K. and D. Montgomery, "Resilient Interdomain
Traffic Exchange: BGP Security and DDos Mitigation", 2019,
<https://www.nist.gov/publications/resilient-interdomain-
traffic-exchange-bgp-security-and-ddos-mitigation>.
[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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[sav-yang] "YANG Data Model for Intra-domain and Inter-domain Source
Address Validation(SAVNET)", 2023,
<https://datatracker.ietf.org/doc/draft-li-savnet-sav-
yang/>.
Authors' Addresses
Weiqiang Cheng
China Mobile
Beijing
China
Email: chengweiqiang@chinamobile.com
Nan Geng
Huawei
Beijing
China
Email: gengnan@huawei.com
Dan Li
Tsinghua University
Beijing
China
Email: tolidan@tsinghua.edu.cn
Shengnan Yue
China Mobile
Beijing
China
Email: yueshengnan@chinamobile.com
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