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INIT Forwarding for the Stream Control Transmission Protocol
draft-tuexen-tsvwg-sctp-init-fwd-00

Document Type Active Internet-Draft (individual)
Authors Michael Tüxen , Timo Völker
Last updated 2022-10-24
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draft-tuexen-tsvwg-sctp-init-fwd-00
Network Working Group                                           M. Tüxen
Internet-Draft                                                 T. Völker
Intended status: Standards Track         Münster Univ. of Appl. Sciences
Expires: 27 April 2023                                   24 October 2022

      INIT Forwarding for the Stream Control Transmission Protocol
                  draft-tuexen-tsvwg-sctp-init-fwd-00

Abstract

   The Stream Control Transmission Protocol (SCTP) extension described
   in this document allows the support of a simple mechanism to
   distribute association requests between a cluster of SCTP end points
   providing the same service.  In particular, this allows the use of
   anycast addresses in combination with SCTP.

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 https://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 27 April 2023.

Copyright Notice

   Copyright (c) 2022 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 (https://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 Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions . . . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  A New Chunk Parameter . . . . . . . . . . . . . . . . . . . .   2
   4.  Procedures  . . . . . . . . . . . . . . . . . . . . . . . . .   3
   5.  Socket API Considerations . . . . . . . . . . . . . . . . . .   4
     5.1.  Get or Set Accepting a Zero Checksum
           (SCTP_INIT_FORWARDING)  . . . . . . . . . . . . . . . . .   5
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   The protocol extension described in this document allows an
   initiation of an SCTP association to deal with an address change of
   the peer during the handshake.  The extension enables the peer to
   respond from another address than the one used as destination address
   in the received packet containing the INIT chunk.  The SCTP Dynamic
   Address Reconfiguration extension described in [RFC5061] can not be
   used, since it does not apply to the handshake.

2.  Conventions

   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 BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

3.  A New Chunk Parameter

   The INIT Forwarding Chunk Parameter is defined by the following
   figure.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Type = 0x8006         |            Length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   \                                                               \
   /                           Parameter                           /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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                 Figure 1: INIT Forwarding Chunk Parameter

   Type: 16 bits (unsigned integer)
      This field holds the IANA defined parameter type for the "INIT
      Forwarding" chunk parameter.  IANA is requested to assign the
      value 32774 (0x8006) for this parameter type.

   Length: 16 bits (unsigned integer)
      This field holds the length in bytes of the chunk parameter; the
      value MUST be the length of the parameter included plus 4.

   Parameter: variable length
      The parameter MUST be one of:

      *  IPv4 Address parameter as specified in [RFC9260].

      *  IPv6 Address parameter as specified in [RFC9260].

      *  Padding parameter as specified in [RFC4820].  The length of the
         Padding parameter MUST be either the length of an IPv4 Address
         parameter or the length of the IPv6 Address parameter.

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

   The INIT Forwarding Chunk Parameter MAY appear in INIT and INIT ACK
   chunks and MUST NOT appear in any other chunk.  If an INIT or INIT
   ACK chunk contains an INIT Forwarding Chunk Parameter, the INIT
   Forwarding Chunk Parameter MUST be the first optional/variable-length
   parameter.

   If an end point not supporting the extension described in this
   document receives this parameter in an INIT or INIT ACK chunk, it
   skips this parameter and continues to process further parameters in
   the chunk.  This behaviour is REQUIRED by [RFC9260] because the
   highest-order 2 bits of the Type are 10.

4.  Procedures

   If an end point that sends an SCTP packet containing an INIT chunk
   wants to allow the peer to respond from an address different from the
   destination address of the packet, MUST use the INIT Forwarding Chunk
   parameter as the first optional/variable-length parameter.  The
   parameter in the INIT Forwarding Chunk parameter MUST be a Padding
   parameter.  If the SCTP packet containing the INIT chunk is sent over
   IPV4, the length of the padding parameter MUST be the length of an
   IPv4 Address parameter, which is 8 bytes.  Otherwise, if the SCTP
   packet containing the INIT chunk is sent over IPV6, the length of the

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   padding parameter MUST be the length of an IPv6 Address parameter,
   which is 20 bytes.

   If a middlebox receives an SCTP packet containing an INIT chunk with
   INIT Forwarding Chunk parameter as its first optional/variable-length
   parameter and wants to change the destination address of the packet,
   it MUST replace the Padding parameter in the INIT Forwarding Chunk
   parameter with an IPv4 or IPv6 Address parameter containing the
   original destination address of the SCTP packet containing the INIT
   chunk.  If the INIT Forwarding Chunk parameter does not contain a
   Padding parameter, but an IPv4 or IPv6 Address parameter, the INIT
   Forwarding Chunk parameter MUST NOT be modified at all.

   If an end point receives an SCTP packet containing an INIT chunk and
   the INIT chunk contains an INIT Forwarding Chunk parameter including
   an Address parameter as its first optional/variable-length parameter,
   the end point MUST include this INIT Forwarding Chunk parameter as
   the first optional/variable-length parameter in the INIT ACK chunk,
   which is sent in response.  If the INIT Forwarding Chunk parameter
   contains a Padding parameter and the end-point does not want to use
   the destination address, it MUST put an INIT Forwarding Chunk
   parameter containing this address in the INIT ACK chunk sent in
   response.  If the end point wants to use the destination address in
   the association and the INIT Forwarding Chunk parameter contains a
   Padding parameter, the INIT Forwarding Chunk parameter MUST NOT be
   included in the INIT ACK chunk.

   If an end point receives an SCTP packet containing an INIT ACK chunk
   and it cannot find the association for this packet using the IP
   addresses and port numbers, and the INIT ACK chunk contains an INIT
   Forwarding Chunk parameter as its first optional/variable-length
   parameter, it SHOULD use the IP address contained in the Address
   parameter of the INIT Forwarding Chunk parameter instead of the
   source address of the received packet for the association lookup.  If
   an association is then found, the address in the INIT Forwarding
   Chunk parameter MUST be removed as a remote address and the source
   address of the packet containing the INIT ACK chunk MUST be added as
   an unconfirmed remote address.

5.  Socket API Considerations

   This section describes how the socket API defined in [RFC6458] needs
   to be extended to provide a way for the application to control the
   UDP encapsulation.

   Please note that this section is informational only.

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   A socket API implementation based on [RFC6458] is extended by
   supporting one new read/write IPPROTO_SCTP level socket option.

5.1.  Get or Set Accepting a Zero Checksum (SCTP_INIT_FORWARDING)

   This socket option can be used to control the support of INIT
   forwarding.  It applies only to future SCTP associations on the
   socket.

   This option expects an integer boolean flag, where a non-zero value
   turns on the option, and a zero value turns off the option.

   This option is off by default.

6.  IANA Considerations

   [NOTE to RFC-Editor: "RFCXXXX" is to be replaced by the RFC number
   you assign this document.]

   [NOTE to RFC-Editor: The requested value for the parameter type is
   tentative and to be confirmed by IANA.]

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

   A new chunk parameter type has to be assigned by IANA.  This requires
   an additional line in the "Chunk Parameter Types" registry for SCTP:

            +==========+==========================+===========+
            | ID Value | Chunk Parameter Type     | Reference |
            +==========+==========================+===========+
            | 32774    | INIT Forwarding (0x8006) | [RFCXXXX] |
            +----------+--------------------------+-----------+

               Table 1: New entry in "Chunk Parameter Types"
                                  registry

7.  Security Considerations

   This document does not change the considerations given in [RFC9260].

8.  References

8.1.  Normative References

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   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC4820]  Tuexen, M., Stewart, R., and P. Lei, "Padding Chunk and
              Parameter for the Stream Control Transmission Protocol
              (SCTP)", RFC 4820, DOI 10.17487/RFC4820, March 2007,
              <https://www.rfc-editor.org/info/rfc4820>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC9260]  Stewart, R., Tüxen, M., and K. Nielsen, "Stream Control
              Transmission Protocol", RFC 9260, DOI 10.17487/RFC9260,
              June 2022, <https://www.rfc-editor.org/info/rfc9260>.

8.2.  Informative References

   [RFC5061]  Stewart, R., Xie, Q., Tuexen, M., Maruyama, S., and M.
              Kozuka, "Stream Control Transmission Protocol (SCTP)
              Dynamic Address Reconfiguration", RFC 5061,
              DOI 10.17487/RFC5061, September 2007,
              <https://www.rfc-editor.org/info/rfc5061>.

   [RFC6458]  Stewart, R., Tuexen, M., Poon, K., Lei, P., and V.
              Yasevich, "Sockets API Extensions for the Stream Control
              Transmission Protocol (SCTP)", RFC 6458,
              DOI 10.17487/RFC6458, December 2011,
              <https://www.rfc-editor.org/info/rfc6458>.

Authors' Addresses

   Michael Tüxen
   Münster University of Applied Sciences
   Stegerwaldstrasse 39
   48565 Steinfurt
   Germany
   Email: tuexen@fh-muenster.de

   Timo Völker
   Münster University of Applied Sciences
   Stegerwaldstrasse 39
   48565 Steinfurt
   Germany
   Email: timo.voelker@fh-muenster.de

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