SAVNET-based Anti-DDoS Architecture

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Table of Contents

1. Introduction

DDoS attacks using spoofing addresses are notorious on the Internet. The attackers command a large number of zombie hosts to forge the target's address and send bogus requests, after which the servers respond with magnified datagrams to the target, resulting in an amplification DDoS attacks. Some other DDoS attacks (e.g., TCP SYN Flooding Attacks [RFC4987]) also forge source IP addresses in order to drain the target's resources. These DDoS attacks are simple to carry out but can inflict significant damage. Their attack traffic is widely dispersed and similar to normal traffic, leading challenge to detect and mitigate. Furthermore, the spoofed addresses serve as a mask for the attackers, making it difficult to traceback the attackers.¶

Some Source Address Validation (SAV) techniques have been proposed to defend against DDoS attacks. The current practice for achieving ingress filtering is uRPF [RFC3704], which includes strict uRPF and loose uRPF. Unfortunately, the strict uRPF often improperly blocks legitimate traffic under asymmetric routing, and the loose uRPF generally permits all received packets. EFP-uRPF [RFC8704] makes the uRPF more flexible about directionality, while there are mechanisms that MAY lead to improper permit or improper block problems in specific scenarios. The SAVNET Working Group [SAVNET_WG] provides SAV techniques for intra-domain and inter-domain networks to resolve the problems raised above. It has been deployed for experimental practice [RFC5210] and is promising to solve the SAV problem.¶

However, these SAV techniques are still a long way from being able to defend against DDoS attacks. First, they only discard spoofing packets at local devices, lacking coordination to detect DDoS attacks with a global view. Second, only when these SAV techniques are widely deployed will they be able to eliminate DDoS attacks using spoofing addresses, which will take a long time. Third, there are limited incentives exist to encourage Internet Service Providers (ISPs) to widely deploy SAV devices.¶

In the above context, this document offers a SAVNET-based Anti-DDoS Architecture (SADA) that incorporates the following advances.¶

• A distributed DDoS detection mechanism based on honeynets. The SADA introduces a SAV controller for gathering spoofing statistics from SAV routers that act as honeynets. The SADA can detect DDoS attacks with a comprehensive analysis using aggregated information from distributed SAV routers.¶
• A multi-stage DDoS mitigation mechanism. By overviewing the DDoS attack with a comprehensive view, the mitigation policies can be deployed at multiple stages (i.e., near-source, middle, and near-target). These policies vary at different locations and can efficiently mitigate the attack.¶
• A suspect-based DDoS traceback mechanism. The SADA requires SAV routers to monitor the communication logs of suspicious hosts that have ever forged addresses. The communication logs will be analyzed to find the attackers.¶

The SADA can provide considerable advantages for DDoS attacks by fully adopting SAVNET features with only minor changes. Even with a small number of SAV routers deployed, the SADA can deliver accurate DDoS detections across a larger area. As long as the attack traffic flows through the SAV domain, the SADA is able to mitigate it. With the aggregated communication logs of suspicious hosts, the SADA can also assist in tracing back the attacker. In addition, the SADA will provide a spoofing address database and a DDoS attacks database, both of which will be available for SAV domains and other domains. The above incentives MAY induce ISPs to widely deploy SAV devices, which will, in turn, stimulate a more valuable SADA system.¶

2. Architecture

+---------------------------------------------------------------+
|                Control Plane (SAV controller)                 |
+---------------------------------------------------------------+
|  +-------------+       +-------------+       +-------------+  |
|  |  Detection  |       | Mitigation  |       |  Traceback  |  |
|  +-------------+       +-------------+       +-------------+  |
|  +--------------------+     +------------------+              |
|  | Spoofing Addresses |     |   DDoS Attack    |              |
|  | Database           |     |   Database       |     ...      |
|  +--------------------+     +------------------+              |
+---------------^-------------------------------+---------------+
                |                               |
     Northbound |                               | Southbound
     Interface  |                               | Interface
                |                               |
+---------------+-------------------------------v---------------+
|                  Data Plane (SAV routers)                     |
+---------------------------------------------------------------+
|  +-------------+    +-------------+    +-------------+        |
|  | Monitoring  |    | Measurement |    |  Filtering  |  ...   |
|  +-------------+    +-------------+    +-------------+        |
+---------------------------------------------------------------+

    Figure 1: The SAVNET-based Anti-DDoS Architecture

The proposed SADA is shown in Figure 1. The SADA consists of the data plane and the control plane, where the primary functions of the data plane are monitoring, measurement, and filtering, and the primary functions of the control plane are detecting the attacks, formulating defense strategies, and tracing back the attacks. The northbound interface is used to send statistics data to the control plane, and the southbound interface is used to receive defense strategies from the control plane. The two planes communicate with each other and work together to defend against DDoS attacks.¶

            +-------------------------------+
+-------+   |  +-------+         +-------+  |  +-------+
| SR 1  +---+  | SC 1  +----+----+ SC 2  |  +--+ SR 3  |
+-------+   |  +-------+    |    +-------+  |  +-------+
            |               |               |
+-------+   |           +---+---+           |  +-------+
| SR 2  +---+           | SC 3  |           +--+ SR 4  |
+-------+   |           +-------+           |  +-------+
            +-------------------------------+
SR: SAV router
SC: SAV controller

      Figure 2: Connection Example of SAV Devices

      +------------+               +------------+
      |   SAV      +---------------> SAV        |
      |   Router   <---------------+ Controller |
      +------------+               +------------+

3. Data Plane

The data plane is primarily comprised of distributed SAV routers. SAV routers MAY be deployed in access networks, within Autonomous System (AS) domains, or at the AS domains boundary. The general features of SAV routers are the same wherever they are deployed and can be summarized as follows.¶

• Collect Spoofing Information. SAV routers need to collect the statistical data of packets with spoofed addresses. The information includes but is not limited to spoofed source addresses, destination addresses, port numbers, packet intervals, and frequencies.¶
• Collect information of suspicious hosts. When SAV routers detect a host forging source addresses, they MAY add the host to the list of suspicious hosts. The SAV routers MUST then monitor the communication logs of these suspicious hosts. The logs contain information that includes but is not limited to destination addresses, protocols, packet intervals, and frequencies.¶
• Receive and Execute Instructions. When the SAV controller issue the defense strategies, the SAV routers MUST respond appropriately. The response mainly consists of Access Control Lists (ACL) filtering [RFC8519] and black-hole routing [RFC5635]. SAV routers with various locations will perform different actions, such as filtering spoofed packets at the access network and black-hole routing at the AS domain boundary.¶
• Keep the Capacity for Escape. Attack traffic can sometimes exceed router links, resulting in disconnection from SAV routers to the SAV controller. To avoid the terrible circumstance, SAV routers MUST reserve a specified amount of bandwidth to maintain a continuous connection with the SAV controller.¶

4. Control Plane

The control plane consists of the SAV controller that can be clustered or distributed servers. The SAV controller are responsible for detecting, mitigating, and tracing back DDoS attacks. They also provide spoofing address database and DDoS attacks database for others to reference. The following are the features of the SAV controller.¶

• Aggregate Spoofing Information. The SAV controller collects spoofing statistics from SAV routers everywhere and aggregates them for further analysis.¶
• Detect DDoS Attacks. The SAV controller MUST determine whether a DDoS attack is ongoing based on the aggregated information. The judgment results MUST specify the attack target, traffic volume, impacted scope, duration time, and so on.¶
• Formulate Defense Strategies. Based on judgment results, the SAV controller will devise the appropriate defense strategies. The defense mechanisms MAY include ACL-based filtering and black-hole routing, which vary on specific SAV routers according to their locations. The SAV controller then issues detailed defense instructions to individual SAV routers for execution.¶
• traceback Attacks. The SAV controller also aggregates information about suspicious hosts and analyzes the communication logs of these suspicious hosts to locate the attacker.¶
• Build and Maintain the databases. The SAV controller MUST build and maintain the spoofing address database at a global view, which will, in turn, help to detect DDoS attacks. The SAV controller MUST also build the DDoS attack database with the detection results, which contain the details about each attack, such as the attacker address, the target address, traffic volume, impacted scope, and duration time. Such a DDoS attack database will help to review the entire process of attacks.¶
• Provide Management Interface. Detecting, mitigating, and tracing back DDoS attacks MAY necessitate some manual settings in certain contexts. The management interface provides a convenient way to adjust these settings.¶

5. Incentives for Deployment

• Provide DDoS Defense Ability. Whenever the attack traffic flows through the SAV domains, the SAV devices can react to mitigate the attack. Any ISP that has deployed SAV devices can also obtain the spoofing address information and DDoS attacks information. With this accurate and real-time information, ISPs can decide how to take measures to protect their customers.¶
• Locate the Malicious Hosts and Reduce Costs. With deployed SAV devices, ISPs can identify the zombie hosts and help to traceback the attackers. These zombie hosts MAY incur additional traffic and energy costs. Locating and removing these malicious hosts not only help to reduce the costs but also improve the reputation of ISPs.¶

6. IANA Considerations

This document includes no request to IANA.¶

7. Security Considerations

• When DDoS attacks appear, the SAV routers MAY perform different filtering policies at different locations. If SAV routers get a bogus mitigation policy, they MAY undertake destructive filtering activities.¶
• The SAV controller is the core of the SADA and MUST be secure at all times. The SAV controller SHOULD be able to defend themselves against any invasions.¶
• The SAV controller's functions are based on statistical data aggregated from the SAV routers. Fake statistical data might have unanticipated consequences.¶

Acknowledgements

TBD¶

Authors' Addresses