DOTS M. Chen
Internet-Draft Li. Su
Intended status: Informational China Mobile
Expires: December 26, 2020 June 24, 2020

A method for dots server deployment
draft-chen-dots-server-hierarchical-deployment-03

Abstract

As DOTS is used for DDoS Mitigation signaling, there are different deployment scenarios for DOTS agents deployment depending on the network topology. This document made recommandations for DOTS Server deployment, include ISP and enterprise deployment scenarios. 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 configure DOTS clients with the correct DOTS server(s) information 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.
ISP:
Internet service provider.
Orchestrator:
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 mitigator that can provide DDoS mitigation service. So far, how many network devices can play the role of mitigator, we make a summerized list as follows:

There are several requirements for DOTS server deployment that may be , and is consistent with other drafts:

4. DOTS server deployment inside an ISP

4.1. DOTS Agents Deployment

From the internal structure of ISP, the whole network can abstract as a three-level network logically. The hierarchy of the network can be adjusted according to the size of the network. In addition to having its own business, the upper network is responsible for connectivity between the lower networks. It's worth noting that there are usually Internet Data Centers(IDC), high bandwidth demand customers(such as online game companies) and VIP customer centers(such as financial clients) distributed in each level network, but most of these services are typically placed on a secondary network.


                          /<===>Mitigator
                    __(RT)___
                  /          \
                 /    primary \      
                ----------------
                        |
                      /   \
                     /     \    /<===>Mitigator
             _______        _(RT)_
            /       \      /      \
           / Second  \    / Second \
           -----------    ----------
              /               /   \
             /<==>Mitigator  /     \ 
        _(RT)              ___       _(RT)
      /     \             /   \     /    \
     / Third \           /Third\   /Third \
     ---------           -------   --------
        Figure 1: ISP multilevel network
           
          

There are mitigators such as cleaning centers in each regional network. Select the second level network for detailed description, the cleaning equipment is attached to the exit router, and Detector is concatenated on the link, usually detector could be one type of netflow/ipfix collector, sometimes could be firewall or IDS(Intrusion Detection System), they could able to find some types of DDoS attacks. Attacks from two different sources occur inside the Second network as follows:

                      
                   (Router)<=====>Flow Clean Device
                      ^^
                      ||(Detector)
              ________||__________
             (        ||          )
            (   #IDC# ++<<<<<<DDoS  )
            (     #VIP#              )
            (      #other service#   )
            (              ^^        )      
            _______________||________
                           ||
                DDoS>>>>>>>++                                
          
          Figure 2:Two DDoS attack paths
           
          

There are only two attack source paths under this structure: One is an attack launched within the network, flowing to the upper level of the network. The other is that low-level networks launch attacks and flow to the upper level of networks, and pass through the intermediate level network. Internal DDoS attacks is out of scope in this draft.

In this case, DOTS clients might consider to be deployed internally. When DDoS attack occurs, attack target inside the Second network may sense being attacked, such as customer complaints and the processing speed is slower than before. attack target then inform Detector(DOTS client) making mitigation request to DOTS server(Router), and the traffic mitigation is then triggered. DOTS server and Mitigator are in the same administrative domain.

          (The Secondary network)

                      ^
                      ||
                   (Router)<=====>Flow Clean Device
                (DOTS Server)          (Mitigator)
                      ^
                      ||
                      |/
                 (DOTS Client)
                    Detector
              ________||__________
             (        || 1        )
            (   #IDC# ++<<<<<<DDoS  )
            (     #VIP#              )
            (      #other service#   )
            (              ^^        )      
            _______________||_________
       -------------------2||--------------
      (The Third network)  ||
                           ||
                DDoS>>>>>>>++                                
          Figure 3: DOTS Agents Deployment
           
          

When DDoS Attack path case 1 occurs, the DOTS client in the same network will send mitigation requests to DOTS server which installed in the same area within export router.

When DDoS Attack path case 2 occurs, the Dots server in the Third network export router will receive mitigation request. If the first level of protection is not effective enough, the DOTS server in the upper network will also receive mitigation requests.

If attacks on the same attack target are found both in adjacent areas, there are two strategies for the mitigators' selection, then found the best mitigation node for different scenes.

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. When multiple mitigators need to work together, then need orchestrator to take on the role for scheduling. Because the importance of the orchestrator, it is suggested to consider bakeup mechanisms or heartbeat technology 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.

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.

We suggest orchestrator has three capabilities and reuse the method of registration and notification in signal channel to know all the related mitigators capability and residue capability:

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

Because of global connectivity, 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    |
            | +---------+ |        | +---------+ |
            |   C/S       |        |    C/S      |
            +-------------+        +-------------+
                 |                           |
                 +---------------------------+
                               |
                               |
                       +-------------+      
                       |     C/S     |
                       | +---------+ |
                       |    ISP C    |
                       +-------------+
         Figure 4: DOTS Agents Deployment between ISPs
    				
    			

When an DDoS attack occurs, depending on the direction of the attack, the corresponding server is required for mitigation, DOTS server can use call home to find the source of the DDoS attacks[I-D.ietf-dots-signal-call-home]

6. DOTS server deployment for Enterprise

In addition to operators taking advantage of the pipeline to make a contribution to DDoS attack mitigation, there are also enterprise-level DDoS attack mitigation solutions. It's usually a cloud service and a large number of distributed nodes are deployed to protect their customers from DDoS attack, customers' websites can be hidden behind the nodes, usually the internet game companies and the live streaming company will choose this way.

            +-------------+        
            |    ISP      |        
            | +---------+ |        
            | |dots svr | |        
            +-------------+
                   |
                   |
            +-------------+
            | Anti-D Node |
            +-------------+
             |dots client|
             +-----------+
                   |
                   |
            +-------------+
            |attack target|
            +-------------+

         *Anti-D is for Anti-DDoS

  Figure 5: Deployment for Enterprise and ISP                
            
      
          

When enterprise-level anti-DDos nodes are unable to mitigate the DDoS attack, they can trigger DOTS client which integrated in the Anti-D Node to send mitigation request to ISP's DOTS server.

7. Security Considerations

TBD

8. IANA Considerations

TBD

9. Acknowledgement

TBD

10. References

10.1. 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.

10.2. Informative References

[I-D.ietf-dots-architecture] Mortensen, A., Reddy.K, T., Andreasen, F., Teague, N. and R. Compton, "Distributed-Denial-of-Service Open Threat Signaling (DOTS) Architecture", Internet-Draft draft-ietf-dots-architecture-18, March 2020.
[I-D.ietf-dots-multihoming] Boucadair, M., Reddy.K, T. and W. Pan, "Multi-homing Deployment Considerations for Distributed-Denial-of-Service Open Threat Signaling (DOTS)", Internet-Draft draft-ietf-dots-multihoming-04, May 2020.
[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 T. Reddy.K, "Distributed-Denial-of-Service Open Threat Signaling (DOTS) Agent Discovery", Internet-Draft draft-ietf-dots-server-discovery-10, February 2020.
[I-D.ietf-dots-signal-call-home] Reddy.K, T., Boucadair, M. and J. Shallow, "Distributed Denial-of-Service Open Threat Signaling (DOTS) Signal Channel Call Home", Internet-Draft draft-ietf-dots-signal-call-home-08, March 2020.
[I-D.ietf-dots-signal-channel] Reddy.K, T., 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-41, January 2020.
[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-23, May 2020.

Authors' Addresses

Meiling Chen China Mobile 32, Xuanwumen West BeiJing , BeiJing 100053 China EMail: chenmeiling@chinamobile.com
Li Su China Mobile 32, Xuanwumen West BeiJing , 100053 China EMail: suli@chinamobile.com