DOTS M. Chen
Internet-Draft Li. Su
Intended status: Informational Jin. Peng
Expires: May 3, 2020 CMCC
October 31, 2019

A method for dots server deployment


As DOTS is used for DDoS Mitigation signaling, in practice, there are different deployment scenarios for DOTS agents deployment depending on the network deployment mode. This document made an accommandation for DOTS Server deployment which may be Suitable for ISP. The goal is to provide some guidance for DOTS agents deployment.

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Table of Contents

1. Introduction

DDoS Open Threat Signaling (DOTS) is a protocol to standardize real-time signaling, threat-handling requests[I-D.ietf-dots-signal-channel], when attack target is under attack, dots client send mitigation request to dots server for help, If the mitigation request contains enough messages of the attack, then the mitigator can respond very effectively.

In the architecture draft[I-D.ietf-dots-architecture], when comes to the deployment topic, it says this does not necessarily imply that the attack target and the DOTS client have to be co-located in the same administrative domain, but it is expected to be a common scenario. Although co-location of DOTS server and mitigator within the same domain is expected to be a common deployment model, it is assumed that operators may require alternative models.

In the DOTS server discovery draft[I-D.ietf-dots-server-discovery], it is says that a key point in the deployment of DOTS is the ability of network operators to be able to onfigure DOTS clients with the correct DOTS server(s) nformation consistently.

In the DOTS multihoming draft[I-D.ietf-dots-multihoming], it provides deployment recommendations for DOTS client and DOTS gateway, it is says when conveying a mitigation request to protect the attack target, the DOTS client among the DOTS servers available Must select a DOTS server whose network has assigned the prefixes from which target prefixes and target IP addresses are derived. This implies that id no appropriate DOTS server is found, the DOTS client must not send the mitigation request to any DOTS server. So in this document, we give some dots server deployment consideration as the title suggests we prefer hierarchical deployment.

This is DOTS server deployment guidance for operators, We've written about our experience as an ISP, and we hope that other scenarios will contribute as well.

2. Terminology

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 [RFC2119]

The readers should be familiar with the terms defined in [I-D.ietf-dots-requirements] [I-D.ietf-dots-use-cases]

The terminology related to YANG data modules is defined in [RFC7950]

In addition, this document uses the terms defined below:

dots svr:
abbreviation of dots server.
Internet service provider.
With the function of DOTS server that can receive messages from clients and made decisions for mitigators selection.
netflow/ipfix collector:
Flow collector used for DDoS attack detection.

3. DOTS server Considerations

When take dots server deployment into consideration, one thing must be involved is far, how many network devices can play the role of mitigator, we make a summerized list as follows:

Whether DOTS server can be deployed, the following conditions need to be met:

4. DOTS server deployment inside an ISP

4.1. DOTS Agents Deployment

From the internal structure of ISP, the whole network can divide into three parts logically. There are three most important routers: backbone router, man(metropolitan area network) router, and IDC router. When a ddos attack occurs, it must be one of the three cases as follows, and the corresponding mitigator will responsible for mitigation.

Normally, The lower network the target in, the easier it is to alert. Because the higher network the attack target in, the greater the bandwidth of the pipeline. As shown in the following figure, Orchestrator take on the role for scheduling. Because the importance of the orchestrator, it is suggested to consider bakeup mechanisms to ensure continuity and security.

How does DOTS client can find DOTS servers, we can reference the DOTS server discovery draft[I-D.ietf-dots-server-discovery], Static configuration or dynamic discovery depends on the actual scenario and the size of the network.

    				|other ISP|
    			         |         backbone network
                 +---------------+     +----------+
                 |backbone router|-----|mitigator1|
                 +---------------+     +----------+
                    |dots svr1|
                         |       metropolitan area network
                   +----------+       +----------+
                   |man router|-------|mitigator2|
                   +----------+       +----------+
                    |dots svr2|
                         |       local area network
                   +----------+      +----------+
                   |IDC router|------|mitigator3|
                   +----------+      +----------+
                    |dots svr3|
                   +-----------+    +-----------------------+   +-------------+
                   |dots client|----|netflow/ipfix collector|---|attack target|  
                   +-----------+    +-----------------------+   +-------------+

Figure 1: DOTS Server Deployment

4.2. DOTS Agents interfaces

In the dots use case draft[I-D.ietf-dots-use-cases], it is says the orchestrator analyses the various information it receives from DDoS telemetry system, and initiates one or multiple DDoS mitigation strategies. In the telemetry draft, all the telemetry informations are contained and some parameters can be used to make decisions. This section made a discussion on which attributes could be used in orchestrator for scheduling and the orchestrator's ability. to know all the related mitigators capability and residue capability.

We suggest orchestrator has three capabilities and reuse the method of registration and notification in signal channel:

1.Can get the neflow/ipfix collector's telemetry informations.

2.Can get the capabilities of each mitigator, it means the initial capacity, this means that with each addition of mitigator there needs to be a protocol that can push this information to orchestrator, we recommend using DOTS signal channel to transfer initial capacity.

3.When mitigation finished, mitigator can inform orchestrator that mitigation is finished and capacity has been released, also we recommend using DOTS signal channel to transfer.

4.2.1. Bandwidth consuming attack

The following parameters will be required by orchestrator:

The recommended approach here is to redirect traffic and flow cleaning.

4.2.2. Host resource consuming attack

The following parameters will be required by orchestrator:

The recommended approach here is to use router for disposition.

5. DOTS server deployment between ISPs

The coexistence of different operators is very common, coordination between operators across networks is very important. Interdomain attacks occur frequently, We recommend deploying the DOTS server at the access point

    				+-------------+        +-------------+
    				|    ISP A    |--------|    ISP B    |
    				| +---------+ |        | +---------+ |
    				| |dots svrA| |        | |dots svrB| |
    				+-------------+        +-------------+
    				    |                           |
                               |    ISP C    |
                               | +---------+ |
                               | |dots svrC| |

Figure 2: DOTS Server Deployment2

6. Security Considerations


7. IANA Considerations


8. Acknowledgement


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.
[RFC7950] Bjorklund, M., "The YANG 1.1 Data Modeling Language", RFC 7950, DOI 10.17487/RFC7950, August 2016.

9.2. Informative References

[I-D.ietf-dots-architecture] Mortensen, A., K, R., Andreasen, F., Teague, N. and R. Compton, "Distributed-Denial-of-Service Open Threat Signaling (DOTS) Architecture", Internet-Draft draft-ietf-dots-architecture-14, May 2019.
[I-D.ietf-dots-multihoming] Boucadair, M., K, R. and W. Pan, "Multi-homing Deployment Considerations for Distributed-Denial-of-Service Open Threat Signaling (DOTS)", Internet-Draft draft-ietf-dots-multihoming-02, July 2019.
[I-D.ietf-dots-requirements] Mortensen, A., K, R. and R. Moskowitz, "Distributed Denial of Service (DDoS) Open Threat Signaling Requirements", Internet-Draft draft-ietf-dots-requirements-22, March 2019.
[I-D.ietf-dots-server-discovery] Boucadair, M. and R. K, "Distributed-Denial-of-Service Open Threat Signaling (DOTS) Agent Discovery", Internet-Draft draft-ietf-dots-server-discovery-05, August 2019.
[I-D.ietf-dots-signal-channel] K, R., Boucadair, M., Patil, P., Mortensen, A. and N. Teague, "Distributed Denial-of-Service Open Threat Signaling (DOTS) Signal Channel Specification", Internet-Draft draft-ietf-dots-signal-channel-38, October 2019.
[I-D.ietf-dots-use-cases] Dobbins, R., Migault, D., Moskowitz, R., Teague, N., Xia, L. and K. Nishizuka, "Use cases for DDoS Open Threat Signaling", Internet-Draft draft-ietf-dots-use-cases-20, September 2019.

Authors' Addresses

Meiling Chen CMCC 32, Xuanwumen West BeiJing , BeiJing 100053 China EMail:
Li Su CMCC 32, Xuanwumen West BeiJing , 100053 China EMail:
Jin Peng CMCC 32, Xuanwumen West BeiJing , 100053 China EMail: