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Versions: 00 01 02

Network Working Group                                          M. Tuexen
Internet-Draft                          Muenster Univ. of Appl. Sciences
Updates: 6951 (if approved)                                   R. Stewart
Intended status: Standards Track                           Netflix, Inc.
Expires: January 4, 2018                                    July 3, 2017


   Additional Considerations for UDP Encapsulation of Stream Control
                  Transmission Protocol (SCTP) Packets
             draft-tuexen-tsvwg-sctp-udp-encaps-cons-02.txt

Abstract

   RFC 6951 specifies the UDP encapsulation of SCTP packets.  The
   described handling of received packets requires the check of the
   verification tag.  However, RFC 6951 misses a specification for the
   handling of received packets for which this check is not possible.

   This document updates RFC 6951 by specifying the handling of received
   packets where the verification tag can not be checked.

Status of This Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   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."

   This Internet-Draft will expire on January 4, 2018.

Copyright Notice

   Copyright (c) 2017 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



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   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  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions . . . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  Handling of Out of the Blue Packets . . . . . . . . . . . . .   3
   4.  Handling of SCTP Packets Containing an INIT Chunk Matching an
       Existing Association  . . . . . . . . . . . . . . . . . . . .   3
   5.  Middlebox Considerations  . . . . . . . . . . . . . . . . . .   5
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   8.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   6
   9.  Normative References  . . . . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   [RFC6951] specifies the UDP encapsulation of SCTP packets.  To be
   able to adopt automatically to changes of the remote UDP
   encapsulation port number, it is updated automatically when
   processing received packets.  This includes automatic enabling and
   disabling of UDP encapsulation.

   Section 5.4 of [RFC6951] describes the processing of received packets
   and requires the check of the verification tag before updating the
   remote UDP encapsulation port and the possible enabling or disabling
   of UDP encapsulation.

   [RFC6951] basically misses a description for the handling of received
   packets where this verification tag check is not possible.  This
   includes packets for which no association can be found and packets
   containing an INIT chunk, since the verification tag for these
   packets must be 0.

2.  Conventions

   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 [RFC2119].








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3.  Handling of Out of the Blue Packets

   If the processing of an out of the blue packet requires the sending
   of a packet in response according to the rules specified in
   Section 8.4 of [RFC4960], the following rules apply:

   1.  If the received packet was encapsulated in UDP, the response
       packets MUST also be encapsulated in UDP.  The UDP source port
       and UDP destination port used for sending the response packet are
       the UDP destination port and UDP source port of the received
       packet.

   2.  If the receive packet was not encapsulated in UDP, the response
       packet MUST NOT be encapsulated in UDP.

   Please not that in these cases a check of the of the verification tag
   is not possible.

4.  Handling of SCTP Packets Containing an INIT Chunk Matching an
    Existing Association

   SCTP packets containing an INIT chunk have the verification tag 0 in
   the common header.  Therefore the verification can't be checked.

   The following rules apply when processing the received packet:

   1.  The remote UDP encapsulation port for the source address of the
       received SCTP packet MUST NOT be updated if the encapsulation of
       outgoing packets is enabled and the received SCTP packet is
       encapsulated.

   2.  The UDP encapsulation for outgoing packets towards the source
       address of the received SCTP packet MUST NOT be enabled, if it is
       disabled and the received SCTP packet is encapsulated.

   3.  The UDP encapsulation for outgoing packets towards the source
       address of the received SCTP packet MUST NOT be disabled, if it
       is enabled and the received SCTP packet is not encapsulated.

   4.  If the UDP encapsulation for outgoing packets towards the source
       address of the received SCTP packet is disabled and the received
       SCTP packet is encapsulated, an SCTP packet containing an ABORT
       chunk MUST be sent.  The ABORT chunk MAY include the error cause
       defined below indicating an "Restart of an Association with New
       Encapsulation Port".  This packet containing the ABORT chunk MUST
       be encapsulated in UDP.  The UDP source port and UDP destination
       port used for sending the packet containing the ABORT chunk are




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       the UDP destination port and UDP source port of the received
       packet containing the INIT chunk.

   5.  If the UDP encapsulation for outgoing packets towards the source
       address of the received SCTP packet is disabled and the received
       SCTP packet is not encapsulated, the processing defined in
       [RFC4960] MUST be performed.  If a packet is sent in response, it
       MUST NOT be encapsulated.

   6.  If the UDP encapsulation for outgoing packets towards the source
       address of the received SCTP packet is enabled and the received
       SCTP packet is not encapsulated, an SCTP packet containing an
       ABORT chunk MUST be sent.  The ABORT chunk MAY include the error
       cause defined below indicating an "Restart of an Association with
       New Encapsulation Port".  This packet containing the ABORT chunk
       MUST NOT be encapsulated in UDP.

   7.  If the UDP encapsulation for outgoing packets towards the source
       address of the received SCTP packet is enabled and the received
       SCTP packet is encapsulated, but the UDP source port of the
       received SCTP packet is not equal to the remote UDP encapsulation
       port for the source address of the received SCTP packet, an SCTP
       packet containing an ABORT chunk MUST be sent.  The ABORT chunk
       MAY include the error cause defined below indicating an "Restart
       of an Association with New Encapsulation Port".  This packet
       containing the ABORT chunk MUST be encapsulated in UDP.  The UDP
       source port and UDP destination port used for sending the packet
       containing the ABORT chunk are the UDP destination port and UDP
       source port of the received packet containing the INIT chunk.

   8.  If the UDP encapsulation for outgoing packets towards the source
       address of the received SCTP packet is enabled and the received
       SCTP packet is encapsulated and the UDP source port of the
       received SCTP packet is equal to the remote UDP encapsulation
       port for the source address of the received SCTP packet, the
       processing defined in [RFC4960] MUST be performed.  If a packet
       is sent in response, it MUST be encapsulated.  The UDP source
       port and UDP destination port used for sending the packet
       containing the ABORT chunk are the UDP destination port and UDP
       source port of the received packet containing the INIT chunk.

   The error cause indicating an "Restart of an Association with New
   Encapsulation Port" is defined bytes the following figure.








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    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        Cause Code = 14        |       Cause Length = 8        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Current Encapsulation Port  |     New Encapsulation Port    |
   +-------------------------------+-------------------------------+

   Cause Code: 2 bytes (unsigned integer)
      This field MUST hold the IANA defined error cause code for the
      "Restart of an Association with New Encapsulation Port" error
      cause.  The suggested value of this field for IANA is 14.

   Cause Length: 2 bytes (unsigned integer)
      This field holds the length in bytes of the error cause; the value
      MUST be 8.

   Current Encapsulation Port: 2 bytes (unsigned integer)
      This field holds the remote encapsulation port currently being
      used for the destination address the received packet containing
      the INIT chunk was sent from.  If the UDP encapsulation for
      destination address is currently disabled, 0 is used.

   New Encapsulation Port: 2 bytes (unsigned integer)
      If the received SCTP packet containing the INIT chunk is
      encapsulated in UDP, this field holds the UDP source port number
      of the UDP packet.  If the received SCTP packet is not
      encapsulated in UDP, this field is 0.

   All transported integer numbers are in "network byte order" a.k.a.,
   Big Endian.

5.  Middlebox Considerations

   Middleboxes often use different timeouts for UDP based flows than for
   other flows.  Therefore the HEARTBEAT.Interval parameter SHOULD be
   lowered to 15 seconds when UDP encapsulation is used.

6.  IANA Considerations

   [NOTE to RFC-Editor:

      "RFCXXXX" is to be replaced by the RFC number you assign this
      document.

   ]

   [NOTE to RFC-Editor:




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      The suggested value for the error cause code is tentative and to
      be confirmed by IANA.

   ]

   This document (RFCXXXX) is the reference for the registration
   described in this section.

   A new error cause code has to be assigned by IANA.  This requires an
   additional line in the "Error Cause Codes" registry for SCTP:

Error Cause Codes

Value    Cause Code                                            Reference
-----    ----------                                            ---------
14       Restart of an Association with New Encapsulation Port [RFCXXXX]

7.  Security Considerations

   This document does not change the considerations given in [RFC6951].

   However, not following the procedures given in this document might
   allow an attacker to take over SCTP associations.  The attacker needs
   only to share the IP address of an existing SCTP association.

   It should also be noted that if firewalls will be applied at the SCTP
   association level they have to take the UDP encapsulation into
   account.

8.  Acknowledgments

   The authors wish to thank Georgios Papastergiou for an initial
   problem report.

   The authors wish to thank Irene Ruengeler and Felix Weinrank for
   their invaluable comments.

   This work has received funding from the European Union's Horizon 2020
   research and innovation programme under grant agreement No. 644334
   (NEAT).  The views expressed are solely those of the author(s).

9.  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,
              <http://www.rfc-editor.org/info/rfc2119>.




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   [RFC4960]  Stewart, R., Ed., "Stream Control Transmission Protocol",
              RFC 4960, DOI 10.17487/RFC4960, September 2007,
              <http://www.rfc-editor.org/info/rfc4960>.

   [RFC6951]  Tuexen, M. and R. Stewart, "UDP Encapsulation of Stream
              Control Transmission Protocol (SCTP) Packets for End-Host
              to End-Host Communication", RFC 6951,
              DOI 10.17487/RFC6951, May 2013,
              <http://www.rfc-editor.org/info/rfc6951>.

Authors' Addresses

   Michael Tuexen
   Muenster University of Applied Sciences
   Stegerwaldstrasse 39
   48565 Steinfurt
   Germany

   Email: tuexen@fh-muenster.de


   Randall R. Stewart
   Netflix, Inc.
   Chapin, SC  29036
   United States

   Email: randall@lakerest.net
























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