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Versions: 00                                                            
DOTS                                                         J. Francois
INTERNET-DRAFT                                                     Inria
Intended Status: Standard Track                               A. Lahmadi
Expires: September 22, 2016               University of Lorraine - LORIA
                                                     Giovane C. M. Moura
                                                               SIDN Labs
                                                            Marco Davids
                                                               SIDN Labs
                                                          March 21, 2016


                       IPv6 DOTS Signal Option
               draft-francois-ipv6-dots-signal-option-00


Abstract

   This document describes a delivery mechanism based on the IPv6 Hop-
   by-Hop options extension header type to carry a DOTS client signal
   message over a congested network due to a DDoS attack. The specified
   mechanism allows the DOTS client signal message to be included using
   an opportunistic way in outgoing IPv6 packets traveling then through
   the network to reach a DOTS server or relay.


Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as
   Internet-Drafts.

   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."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/1id-abstracts.html

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html


Copyright and License Notice



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   Copyright (c) 2016 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
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document. Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document. Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.



Table of Contents

   1  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.2 Motivation . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.3  Terminology . . . . . . . . . . . . . . . . . . . . . . . .  4
   2. Opportunistic DOTS signal format  . . . . . . . . . . . . . . .  5
     2.1 Hop-by-Hop option encoding . . . . . . . . . . . . . . . . .  5
     2.2 DOTS signal Option attributes  . . . . . . . . . . . . . . .  6
     2.3 Example  . . . . . . . . . . . . . . . . . . . . . . . . . .  6
   3 Option Processing  . . . . . . . . . . . . . . . . . . . . . . .  7
     3.2 Opportunistic DOTS signal initialization by a DOTS client  .  7
     3.2 Processing by a non DOTS opportunistic-capable router  . . .  8
     3.3 Processing by a DOTS opportunistic-capable router  . . . . .  9
     3.4 Processing by a DOTS opportunistic-capable relay . . . . . .  9
     3.5 Processing by a DOTS opportunistic-capable server  . . . . .  9
   4  Impact on existing IP layer implementations . . . . . . . . . .  9
   5  Security Considerations . . . . . . . . . . . . . . . . . . . . 10
   6  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 10
   7  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     7.1  Normative References  . . . . . . . . . . . . . . . . . . . 10
     7.2  Informative References  . . . . . . . . . . . . . . . . . . 11
   Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . 12
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13












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1  Introduction

1.1 Overview



   A distributed denial-of-service (DDoS) attack aims at rendering
   machines or network resources unavailable. These attacks have grown
   in frequency, intensity and target diversity [I-D.draft-ietf-dots-
   requirements]. Moreover, several protocols have been utilized to
   amplify the intensity of the attacks [kuhrer2014exit], often peaking
   at several hundred gigabits per second.

   The DOTS aims at defining a common and open protocol to signal DDoS
   attacks to facilitate a coordinated response to these attacks. This
   document defines a signalling mechanism that instead of designing a
   new application-layer protocol, it utilizes the IPv6 Hop-by-Hop
   header [RFC2460]. This header has the advantage to be fully inspected
   by all network devices and it is the first header in IPv6 extension
   headers [RFC7045].

     The new option containing the attributes of the signalling message
   is included in an opportunistic way in available IPv6 packets leaving
   a network element until the message reaches a DOTS server. It thus
   constitutes an additional signalling channel but MUST NOT replace the
   original signalling channel used between DOTS client and servers as
   the one defined in [I-D.draft-reddy-dots-transport]. The DOTS client
   will thus embed the signalling attributes into outgoing IPv6 packets
   not necessarily going to the DOTS server. Intermediate routers
   receiving such a packet will examine it and embed the same
   information into other IPv6 packets. The process continues in this
   opportunistic manner to increase the probability that such a packet
   will be finally forwarded to a DOTS Relay or Server.

   Only the Hop-by-Hop options header allows such behavior and using
   Destination options header is not enough to make the DOTS signal
   going through the network in an opportunistic way. Each network
   element recognizing this new option will select the best fitted  IPv6
   packets to deliver the signal to the DOTS server or relay.     For
   this reason the Hop-by-Hop header option is essential to make such
   behavior compared to other existing IPv6 extension headers [RFC6564].


   It is also important to emphasize that while our mechanism utilizes
   an IPv6 header field, it can also be used signal IPv4 attacks as well
   - given that the network devices are dual stacked.

1.2 Motivation



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   The traffic generated by a DDoS can be characterized according to
   various parameters, such as the layer (IP/ICMP or application),
   maximum and instant throughput, among others. Regardless its nature,
   we assume that for most cases, a DOTS client will be able to signal
   back one or few messages , during the attack, to the DOTS phase.

   We have the same behavior in other DDoS attacks. For instance, on
   November 30th and December 1st, 2015, the Root DNS system was hit by
   an application layer (DNS) attack [rootops-ddos]. Each one of the 13
   root server letters (A--M) was hit by attacks peaking at 5 million
   queries per second. By utilizing the RIPE Atlas DNSMON
   infrastructure, we can see that during the DDoS attacks, most of the
   root server letters remained reachable and able to respond to the DNS
   request sent by the probes employed by the DNSMON [ripe-dnsmon-ddos].
   Few letters, however, had a packet loss rate of more than 99%. The
   DNSMON probes, however, experience mostly delays in their DNS
   requests instead.

   Our signalling mechanism operates in an opportunistic way it is
   designed for DDoS as the ones on the Root DNS system.




1.3  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

   The terms DOTS client, DOTS server, DOTS relay, DOTS agents, signal
   channel, DOTS signal and DOTS signal refers to the terminology
   introduced in [I-D.draft-ietf-dots-requirements].

   The following terms are introduced:

      Opportunistic DOTS signal :
         an IPv6 packet containing the signalling attributes of an
         attack within the Hop-by-Hop extension header. The purpose is
         the same as the DOTS signal. It is used to request help for
         mitigating the attack.

      DOTS opportunistic-capable router:
         a router  with the capacity to decode the opportunistic DOTS
         signal and re-embed such an information in other IPv6 packets.

      All DOTS opportunistic-capable agent are defined as the DOTS
      agents supporting the opportunistic DOTS signal processing.



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2. Opportunistic DOTS signal format

      The goal is to provide an efficient mechanism where nodes in a
      network facing a DDoS attack can deliver a DOTS signal message
      sent by a DOTS client to the DOTS server. The solution defines a
      new IPv6 Hop-by-Hop header option with the semantic that the
      network node SHOULD include the option content within one or
      multiple outgoing IPv6 packets.

2.1 Hop-by-Hop option encoding

      According to [RFC2460], options encoded into the IPv6  Hop-by-Hop
      header are formatted as Type-Length-Values (TLVs). The option for
      opportunistic DOTS signal is thus defined as follows:



   0               7              15              22              31
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Option type  |Option Data Len|    DOTS Signal Attribute[1]   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | DOTS Signal Attribute[2] |  ...  | DOTS Signal Attribute[n]   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The first two bytes define the Hop-by-Hop Option type number
   allocated to the DOTS opportunistic signalling. This number is not
   yet fixed but the first three bits MUST be set to 0. The first two
   zero bits indicate that routers which cannot handle the DOTS signal
   option will continue to process other options. The third 0 bit means
   that the option processing will not change the packet's final
   destination [RFC2460].

   The second two bytes contain the length of the option content. The
   content of the DOTS Signal option is a variable-length field that
   contains one or more type-length-values (TLV) encoded DOTS signal
   attributes, and has the following format:


   0               7              15
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Attr Type   | Attr Data Len | Attr Data ...   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The Attr Type is 8-bit identifier of a DOTS signal attribute.

   The Attr Data Len is 8-bit unsigned integer which is the length of
   Attr Data in bytes.




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   The Attr Data is variable-length field that contains the data of the
   attribute.

2.2 DOTS signal Option attributes



   The first attribute embedded into the opportunistic DOTS signal is a
   TTL (Time-to-Live) field which indicates the maximum number of
   retransmission of the signal into another IPv6 packets until it MUST
   be discarded. Remaining attributes are similar to the header fields
   described in [I-D.draft-reddy-dots-transport] (section 5.1.1) used to
   convey a DOTS signal through a HTTP POST.

    The sequence of attributes to be inserted within the header SHOULD
   be TLV encoded, and they are defined in the following order:

   TTL: Time-to-Live. This is a mandatory attribute.

   host: the IP address of the DOTS server where the signal option
      SHOULD be delivered.

   port: the listening port of the DOTS server.


   policy-id: defined in [I-D.draft-reddy-dots-transport].

   target-ip: defined in [I-D.draft-reddy-dots-transport].
      However, each address or prefix is encoded in its own TLV
      element.

   target-port: defined in [I-D.draft-reddy-dots-transport].
      However, each target port is encoded in its own TLV element.

   target-protocol: defined in [I-D.draft-reddy-dots-transport].
      However each target protocol is encoded in its own TLV element.


   The encoded attributes MUST be included in the option header in the
   order defined above.

2.3 Example

   Following is an example of an encoded Hop-by-Hop Option header to
   signal that a web service is under attack.


   0               7              15              22              31



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   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Next Header  | Hdr Ext Len=7 | PadN Option=2 |      0        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      0        | DOTS Type=31  |Opt Data Len=80| Attr. type=TTL|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |Att Data Len=1 |      128      |Attr. type=host|Att Data Len=4 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                            192.0.2.1                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |Attr. type=port|Att Data Len=2 |             443               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |A. type=policy |Att Data Len=2 |         123321333242          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |Attr. type= ip |Att Data Len=4 |             192.0....         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       ...... 2.20             |Attr. type= ip |Att Data Len=16|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +                                                               +
   |                      2001:db8:6401::1  ...                    |
   +                                                               +
   |                                                               |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |Attr. type=port|Att Data Len=2 |             8080              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |Attr. type=port|Att Data Len=2 |             443               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |Attr.type=proto|Att Data Len=2 |             TCP               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



3 Option Processing

3.2 Opportunistic DOTS signal initialization by a DOTS client

   When a DOTS client needs to inform the DOTS server that it is under
   attack, it firstly makes a connection attempt and applies the
   mechanisms described in [I-D.draft-reddy-dots-transport].

   In addition it actives an opportunistic mechanism to include the Hop-
   by-Hop header option defined in this document in one or multiple IPv6
   packets leaving the node.

   The selection of packets has to be configured  a priori. The
   configuration is composed of a sequence of rules defined in a



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   hierarchical order such that they are triggered in a sequential
   manner.

   Each rule is defined by:
      o a set of filters over the IPv6 packet headers. Only packets
      matching those filters are selected for opportunistic signalling.
      For instance, only packets heading to a given subnetwork or to
      specific address close to a DOTS server can be selected to
      increase the chance to reach the latter.

      o a ratio to select only a proportion of packets matching the
      filters in order to limit the induced overhead of the
      opportunistic signalling.

      o a timeout until the rule is active and selected IPv6 packets
      embed the DOTS opportunistic signal.

   The objective is to apply each ordered rule after another according
   to their timeouts. The first rule is triggered immediately after the
   opportunistic signalling is activated.

   Although the definition of rules MUST be configured by the user. It
   is RECOMMENDED to order them inversely related to the number of
   packet that would be selected. This can be approximated regarding the
   definition of filters. The core idea is to benefit from the first
   instants of the attack before losing connectivity by using a maximum
   of outgoing packets. It is thus RECOMMENDED to define the first as
   matching all IPv6 packets with a ratio equals one to rapidly
   disseminate the information but with a short timeout to limit the
   implied overhead.

   Here is the an example of rules:
      1: all outgoing IPv6 packets with a 10 second timeout
      2: all outgoing IPv6 packets with a ratio of 10% and a 1 minute
      timeout
      3: all outgoing multicast IPv6 packets with a ratio of 10% and a 1
      minute timeout
      4: all outgoing anycast IPv6 packets with a ratio of 10% and a 5
      minute timeout
      5: all outgoing IPv6 packets heading to the DOTS server with a
      ratio of 100% and a one hour timeout



3.2 Processing by a non DOTS opportunistic-capable router

   When receiving an opportunistic DOTS signal encoded in a IPv6 packet,
   a non DOT opportunistic capable router simply skips the Hop-by-Hop



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   option and continue the normal processing of the IPv6 packet because
   the option type MUST start with three zero bits.


3.3 Processing by a DOTS opportunistic-capable router

   A DOTS opportunistic-capable router MUST store DOTS signalling
   information whose it is aware of. If a router processes an IPv6 DOTS
   opportunistic signal and supports this option, it first checks if it
   has already stored the associated information. In that case, the
   router simply skips the option and continues the normal processing
   otherwise it stores the encoded information in order to embed it
   again in other IPv6 packets similarly to the DOTS client. Hence, a
   set of rules are also defined in advance and are triggered upon the
   reception of a new opportunistic DOTS signal. Once all rule have been
   applied, signalling information MUST be discarded by the router. When
   embedding the information into other IPv6 packets, the router MUST
   decrease the TTL by one since opportunistic signalling does not
   prevent loops in the dissemination of signalling.

3.4 Processing by a DOTS opportunistic-capable relay


    If a DOTS relay has DOTS capabilities, it will apply the same
   strategy as a DOTS client by making attempts of direct connections to
   the DOST server and in addition it inserts the Hop-by-Hop header DOTS
   signalling option in leaving IPv6 packets using the strategy
   specified above.


3.5 Processing by a DOTS opportunistic-capable server

   When the IP layer of the host where the DOTS server is running
   receives an IPv6 packet carrying a Hop-by-Hop DOTS signal option
   header it MUST extracts the content of the option and provides the
   attributes data to the server program.




4  Impact on existing IP layer implementations

   For this option to be applicable within an IP system, it requires
   modifications to existing IP layer implementation. At DOTS capable
   nodes (client, relay and server), it requires a service interface
   used by upper-layer protocols and application programs to ask the IP
   layer to insert and listen to the Hop-by-Hop header option in IPv6
   packets with the content and strategies described in Section 3. A



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   DOTS client invokes the service interface to insert the option, A
   DOTS relay invokes the service interface for listening and inserting
   the option, and finally a DOTS server only invokes the service
   interface to listen to the DOTS signalling option.

   Intermediate nodes (routers or middle boxes) IP layer needs to be
   extended to perform processing of the new Hop-by-Hop header option as
   described in Section 3. They mainly parse the first host attribute of
   the option and make a selection of a leaving IPv6 packet where the
   option will be inserted.

   Every node inserting the new proposed Hop-by-Hop option SHOULD only
   select IPv6 packets with enough left space to avoid fragmentation.


5  Security Considerations

   Any IPv6 header option could be used by an attacker to create an
   attack on the routers and intermediate boxes that process packets
   containing the option. The proposed IPv6 option in this document MAY
   be abused by an attacker to create a covert channel at the IP layer
   where data is hidden inside the content of the option [RFC6564].
   However, this attack is not specific to the proposed option and it is
   known issue of IPv6 header extensions and options.

   The option may also be used by an attacker to forge or modify
   opportunistic DOTS signal leading to trigger additional processing on
   intermediate nodes and DOTS servers. Besides, an attacker can also
   listen  opportunistic DOTS signals to monitor the impact of its own
   attack. These considerations are not specific to the proposed option.
   The DOTS agent MAY use techniques to enforce confidentiality,
   authenticity and integrity over the opportunistic DOTS signal
   channel.



6  IANA Considerations

   This draft defines a new IPv6 [RFC2460] hop-by-hop option. This
   requires an IANA RFC3692-style update of:
   http://www.iana.org/assignments/ipv6-parameters/ipv6-parameters.xhtml
   and ultimately the assignment of a new hop-by-hop option according to
   the guidelines described in [RFC5237].

7  References

7.1  Normative References




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7.2  Informative References

   [I-D.draft-ietf-dots-requirements]
      A. Mortensen., R. Moskowitz., and T. Reddy., "DDoS Open Threat
      Signaling Requirements", draft-ietf-dots-requirements-00 (work in
      progress), October 2015.
   [kuhrer2014exit]
      Kuhrer, Marc and Hupperich, Thomas and Rossow, Christian and Holz,
      Thorsten. Exit from Hell? Reducing the Impact of Amplification
      DDoS Attacks. In: 23rd USENIX Security Symposium (USENIX Security
      14).
   [I-D.draft-reddy-dots-transport]
      T. Reddy., D. Wing., P. Patil., M. Geller., M. Boucadair.,and R.
      Moskowitz., "Co-operative DDoS Mitigation", draft-reddy-dots-
      transport-03 (work in progress), March 2016.
   [rootops-ddos]
      rootops.: Events of 2015-11-30. Online: http://root-
      servers.org/news/events-of-20151130.txt
   [ripe-dnsmon-ddos]
      RIPE NCC DNS Monitoring Service (DNSMON). Online:
      https://atlas.ripe.net/dnsmon/






























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Acknowledgements

      This work is partly funded by FLAMINGO, a Network of Excellence
      project (ICT-318488) supported by the European Commission under
      its Seventh Framework Programme.














































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Authors' Addresses


   Jerome Francois
   Inria
   615 rue du Jardin Botanique
   54600 Villers-les-Nancy
   France

   Phone: +33 3 83 59 30 66
   EMail: jerome.francois@inria.fr


   Abdelkader Lahmadi
   University of Lorraine - LORIA
   615 rue du Jardin Botanique
   54600 Villers-les-Nancy
   France

   Phone: +33 3 83 59 30 00
   Email: Abdelkader.Lahmadi@loria.fr


   Giovane C. M. Moura
   SIDN Labs
   6825 MD Meander 501
   Arnhem, the Netherlands


   Marco Davids
   SIDN Labs
   6825 MD Meander 501
   Arnhem, the Netherlands


















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