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INTERNET-DRAFT                                                  C. Byrne
Intended Status: Informational                                J. Kleberg
Expires: January 21, 2016                                  July 20, 2015

                Advisory Guidelines for UDP Deployment


   User Datagram Protocol (UDP) is commonly used as a volumetric attack
   transport on the internet.  Some network operators experience surges
   of UDP attack traffic that are multiple orders of magnitude above the
   baseline traffic rate for UDP.  Application developers should be
   advised that UDP is being rate-limited on a bits-per-second and
   packet-per-second basis by network operators to enforce known good
   baseline traffic levels for UDP. UDP has been abused to such an
   extent that legitimate use may become collateral damage and
   application and protocol developers should avoid using UDP as a
   transport when possible.

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
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   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

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Copyright and License Notice

   Copyright (c) 2015 IETF Trust and the persons identified as the

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   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
   2  Threat from UDP . . . . . . . . . . . . . . . . . . . . . . . .  3
   3  Recommendations for Application and Protocol Developers . . . .  3
   4  Recommendations for Network Operators . . . . . . . . . . . . .  3
   3  Security Considerations . . . . . . . . . . . . . . . . . . . .  4
   4  IANA Considerations . . . . . . . . . . . . . . . . . . . . . .  4
   5  References  . . . . . . . . . . . . . . . . . . . . . . . . . .  4
     5.1  Normative References  . . . . . . . . . . . . . . . . . . .  4
     5.2  Informative References  . . . . . . . . . . . . . . . . . .  5
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . .  5

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1  Introduction

   The User Datagram Protocol (UDP) [RFC0768] provides a minimal,
   unreliable, best-effort, message-passing transport to applications
   and other protocols (such as tunnels) that desire to operate over UDP
   [I-D.draft-ietf-tsvwg-rfc5405bis]. Since UDP does not establish an
   end-to-end connection at the transport layer, it is possible to carry
   out a source IP address spoofed distributed reflective denial-of-
   service attack (DRDoS)[ROSSOW]. Large amplification attacks have
   happened for years on a daily basis and are having a widespread
   negative impact on the internet [US-CERT].

2  Threat from UDP

   Simplicity is the strength of UDP.  Simplicity is also UDP's
   weakness. UDP allows a single packet response from an application.
   TCP [RFC793] and SCTP [RFC4960] operate differently. TCP has a three-
   way handshake and SCTP has a four-way handshake, and thus they verify
   the reverse path will accept the communication within the transport
   layer prior to the application layer engaging.  Since UDP does not do
   any of this handshaking in the transport layer, the applications are
   left to create their own procedure for responding to network
   communication initiation.  In the case of  SNMP, NTP, CHARGEN, and
   DNS, a single spoofed IP packet can generate a much larger response
   to an attack target in many deployments.  The result is that several
   of these UDP deployments covering millions of internet nodes allow an
   attacker to hide the true source of the attack and amplify the
   magnitude of the attack by reflecting off of widely deployed UDP
   services on the internet [ROSSOW].

3  Recommendations for Application and Protocol Developers

   1. Application and protocol developers should avoid using UDP.  The
      abuse of UDP for DRDoS on the internet has made UDP subject to
      aggressive filtering at the transport protocol level.
   2. If UDP must be used, encapsulate it in IPsec [RFC4303] to avoid
      matching IP protocol 17 filters.
   3. In the case of WebRTC [I-D.draft-ietf-rtcweb-transports], TURN
      [RFC5766] should be used to concentrate and manage a known-good
      UDP flows.  It is also recommended that WebRTC evolve to support
      native SCTP transport.
   4. In the case of QUIC [I-D.draft-tsvwg-quic-protocol] and other
      transport innovations, a new IANA assigned protocol number should
      be used to meaningful differentiates traffic from commonly abused
      UDP services.

4  Recommendations for Network Operators

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   1. To prevent the spoofed reflection attacks, all network operators
      should implement anti-spoof address filtering [RFC2827].  This
      prevents the trigger of the DRDoS.
   2. Network operators should govern the types of systems that offer
      UDP services.  This stewardship of directly attached nodes limits
      the fleet of nodes offering UDP services that could be abused for
   3. Network operators should baseline and rate-limit UDP for bits-per-
      second and packets-per-second.  This effort acts as protection
      mechanism to prevent unexpected large UDP flows that are highly
      likely to be DRDoS from propagating across the internet.

3  Security Considerations

   The continued abuse of UDP is a material security threat to the
   availability of the internet.  While mitigating the threat at the
   node implementation level would be ideal, years of experience has
   demonstrated this is not broadly effective.  While improving overall
   network availability by limiting UDP, it is likely that several
   important protocols will be negatively impacted including DNS,
   DNSSEC, DTLS, SRTP, UDP encapsulated IPsec and others.

4  IANA Considerations


5  References

5.1  Normative References

   [RFC768]   Postel, J., "User Datagram Protocol", RFC768, August 1980.

   [RFC2827]  Ferguson, P., D Senie., "Network Ingress Filtering:
              Defeating Denial of Service Attacks which employ IP Source
              Address Spoofing", RFC2827, BCP38, May 2000.

   [RFC4303]  Kent, S., "IP Encapsulating Security", RFC4303, December

   [RFC5766]  Mahy, R., Matthews, P., and J. Rosenberg, "Traversal Using
              Relays around NAT (TURN): Relay Extensions to Session
              Traversal Utilities for NAT (STUN)", RFC 5766, April 2010.

   [ROSSOW]   Rossow, C., "Amplification Hell: Revisiting Network
              Protocols for DDoS Abuse",

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              , February 2014.

5.2  Informative References

   [I-D.draft-ietf-rtcweb-transports] Alvestrand,H., "Transports for
              WebRTC", draft-ietf-rtcweb-transports-09 (work in
              progress), July 2015.

   [I-D.draft-ietf-tsvwg-rfc5405bis] Eggert, C., G. Fairhurst., G.
              Shepherd, "UDP Usage Guidelines", draft-ietf-tsvwg-
              rfc5405bis-03 (work in progress), July 2015.

   [I-D.draft-tsvwg-quic-protocol] Hamilton, R., J. Iyengar, I. Swett,
              A. Wilk., "QUIC: A UDP-Based Secure and Reliable Transport
              for HTTP/2", draft-tsvwg-quic-protocol-01 (work in
              progress), July 2015.

   [RFC793]   Postel, J., "Transport Control Protocol", RFC793,
              September 1981.

   [RFC4960]  Stewart, R., "Stream Control Transmission Protocol",
              RFC4960, September 2007.

   [US-CERT]  US-CERT,"Alert (TA14-017A) UDP-Based Amplification
              Attacks", https://www.us-cert.gov/ncas/alerts/TA14-017A,

Authors' Addresses

   Cameron Byrne
   Bellevue, WA, USA
   EMail: Cameron.Byrne@T-Mobile.com

   Jason Kleberg
   Bellevue, WA, USA
   EMail: Jason.Kleberg@T-Mobile.com

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