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Versions: 00 01 02 draft-ietf-dnsop-session-signal

DNSOP Working Group                                            R. Bellis
Internet-Draft                                                       ISC
Intended status: Standards Track                             S. Cheshire
Expires: January 7, 2017                                      Apple Inc.
                                                            J. Dickinson
                                                                 Sinodun
                                                               A. Mankin
                                                             T. Pusateri
                                                            Unaffiliated
                                                            July 6, 2016


                         DNS Session Signaling
                  draft-bellis-dnsop-session-signal-00

Abstract

   The Extension Mechanisms for DNS (EDNS(0)) [RFC6891] is explicitly
   defined to only have "per-message" semantics.  This document defines
   a new Session Signaling OpCode used to carry persistent "per-session"
   type-length-values (TLVs), and defines an initial set of TLVs used to
   handle feature negotiation and to manage session timeouts and
   termination.

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 7, 2017.

Copyright Notice

   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



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   (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  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Protocol Details  . . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  Message Format  . . . . . . . . . . . . . . . . . . . . .   3
     3.2.  Message Handling  . . . . . . . . . . . . . . . . . . . .   4
     3.3.  TLV Format  . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Mandatory TLVs  . . . . . . . . . . . . . . . . . . . . . . .   5
     4.1.  Feature Negotiation . . . . . . . . . . . . . . . . . . .   5
       4.1.1.  TypeCode Support  . . . . . . . . . . . . . . . . . .   5
     4.2.  Layer 4 Connection Management TLVs  . . . . . . . . . . .   6
       4.2.1.  Terminate . . . . . . . . . . . . . . . . . . . . . .   6
       4.2.2.  Idle Timeout  . . . . . . . . . . . . . . . . . . . .   6
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
     5.1.  DNS Session Signaling OpCode Registration . . . . . . . .   7
     5.2.  DNS Session Signaling Status Codes Registry . . . . . . .   7
     5.3.  DNS Session Signaling Type Codes Registry . . . . . . . .   7
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   8
   8.  Normative References  . . . . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   The Extension Mechanisms for DNS (EDNS(0)) [RFC6891] is explicitly
   defined to only have "per-message" semantics.  This document defines
   a new Session Signaling OpCode used to carry persistent "per-session"
   type-length-values (TLVs), and defines an initial set of TLVs used to
   handle feature negotiation and to manage session timeouts and
   termination.

   A further issue with EDNS(0) is that there is no standard mechanism
   for a client to be able to tell whether a server has processed or
   otherwise acted upon the individual options contained with an OPT RR.
   The Session Signaling Opcode therefore requires an explicit response
   to each TLV within a request.

   The message format (see Section 3.1) does not completely conform to
   the standard DNS packet format but is designed such that existing DNS



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   protocol parsers should be able to read the packet header and then
   simply ignore the extra data that appears thereafter.

2.  Terminology

   The terms "initiator" and "responder" correspond respectively to the
   initial sender and subsequent receiver of a Session Signaling TLV,
   regardless of which was the "client" and "server" in the usual DNS
   sense.  The term "sender" may apply to either an initiator or
   responder.

   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].

3.  Protocol Details

   Session Signaling messages MUST only be carried in protocols and in
   environments that can guarantee that the same two endpoints are in
   communication for the entire lifetime of the session.

   Session Signaling messages relate only to the specific session in
   which they are being carried.  Where a middle box (e.g. a DNS proxy,
   forwarder, or session multiplexer) is in the path the message MUST
   NOT be blindly forwarded in either direction by that middle box.
   This does not preclude the use of these messages in the presence of a
   NAT box that rewrites Layer 3 or Layer 4 headers but otherwise
   maintains the effect of a single session.

   << RB: OSI Layer 5 session analog?  This is obviously intended for
   TCP "sessions" which aren't distinct from Layer 4, but is this also
   applicable to DNS-o-DTLS, or DNS over UDP with an EDNS cookie - I
   think probably "yes" for the former, but "no" for the latter.  I'm
   wondering whether "session" is even the right term to be using
   here >>

3.1.  Message Format

   A message containing a Session Signaling Opcode does not conform to
   the usual DNS message format.  The 12 octet header format from
   [RFC1035] is preserved, but the four section count fields (QDCOUNT,
   ANCOUNT, NSCOUNT and ARCOUNT) MUST all be set to zero.

   A list of TLVs are used in place of the usual sections, and MUST
   appear immediately after the 12 octet header.  The total size of the
   TLVs is calculated from the value of the standard two octet framing
   word minus the 12 octets of the DNS header.




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3.2.  Message Handling

   Both clients and servers may unilaterally send Session Signaling
   messages at any point in the lifetime of a session and are therefore
   considered to be the initiator with respect to that message.  The
   initiator MUST set the value of the QR bit in the DNS header to zero
   (0), and the responder MUST set it to one (1).

   Every Session Signaling request message MUST elicit a response (which
   MUST have the same ID in the DNS message header as in the request)
   and every TLV contained within the request requires a corresponding
   TLV in the response.

   In order to preserve the correct sequence of state, Session Signaling
   requests MUST NOT be processed out of order.  Similarly the TLVs in a
   message MUST be processed in the order in which they are contained in
   the message, and the order of the TLVs in the response MUST
   correspond with the order of the TLVs in the request.

   << RB: should the presence of a SS message create a "sequencing
   point", such that all pending responses must be answered? >>

3.3.  TLV Format

                                                1   1   1   1   1   1
        0   1   2   3   4   5   6   7   8   9   0   1   2   3   4   5
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
      |SESSION-STATUS |         SESSION-TYPE                          |
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
      |                        SESSION-LENGTH                         |
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
      |                                                               |
      /                         SESSION-DATA                          /
      /                                                               /
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

   SESSION-STATUS:  A 4 bit field used in a response to indicate the
      success (or otherwise) of an operation, as defined in the DNS
      Session Signaling Status Codes Registry.  It SHOULD contain
      "NOERROR" (0) in a request message but the responder MUST NOT
      reject the request if it does not.

   SESSION-TYPE:  A 12 bit field in network order giving the type of the
      current Session Signaling TLV per the IANA DNS Session Signaling
      Type Codes Registry.

   SESSION-LENGTH:  A 16 bit field in network order giving the size in
      octets of SESSION-DATA.



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   SESSION-DATA:  Type-code specific.  The SESSION-DATA field MUST be
      NUL padded to an even number of octets such that each Session
      Signaling TLV is aligned on a two octet boundary relative to the
      start of the first Session Signaling TLV.  Padding octets MUST NOT
      be included in the calculation of SESSION-LENGTH but MUST be
      included in the calculation of the overall message length.

   << RB: the padding is specified such that client code can read the
   type and length fields directly from an aligned uint16_t array (with
   byte swapping) >>

4.  Mandatory TLVs

4.1.  Feature Negotiation

4.1.1.  TypeCode Support

   The TypeCode Support TLV (1) is used to allow a client and server to
   exchange information about which Session Signaling Type Codes they
   support.

   The SESSION-DATA contains a list of the Session Signaling Type Codes
   supported by the sender.

                                                1   1   1   1   1   1
        0   1   2   3   4   5   6   7   8   9   0   1   2   3   4   5
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
      |                           TYPE CODEs                          |
      /                              ...                              /
      /                                                               /
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

   TYPE CODEs:  A list of 16 bit words in network order comprising the
      complete list of Session Signaling Type Codes supported by the
      sender.  Since a Session Signaling Type Code is in reality only a
      12 bit value, the four most significant bits of each word MUST be
      zero.  The number of TYPE CODEs can be calculated from the total
      length of the TLV.

   An initiator MAY send its own list of supported Session Signaling
   Type Codes in a TypeCode Support TLV, and if sent they MUST be
   complete.  Otherwise the SESSION-DATA MUST be empty.  In either case
   the responder MUST respond with its complete list of supported Type
   Codes.







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4.2.  Layer 4 Connection Management TLVs

4.2.1.  Terminate

   The Terminate TLV (64) MAY be sent by a server to request that the
   client terminate the session, and when sent MUST be the only TLV
   present.  It MUST NOT be requested by a client.

   The client SHOULD terminate the session as soon as possible, but MAY
   wait for any inflight queries to be answered.  It MUST NOT initiate
   any new queries over the existing session, nor send any further TLVs
   other than its response to the Terminate request.

   << RB: dns-sd push has a "reconnect delay" option but I think it's of
   questionable value since in an anycast or load-balancing architecture
   there's no way for the client to know which instance sent the option
   nor control which server instance the next connection will go to.
   This would IMHO be better controlled directly at the TCP layer. >>

4.2.2.  Idle Timeout

   The Idle Timeout TLV (65) has similar semantics to the EDNS TCP
   Keepalive Option [RFC7828].  It is used by a server to tell the
   client how long it may leave the current session idle for.

   The SESSION-DATA is as follows:

                                                1   1   1   1   1   1
        0   1   2   3   4   5   6   7   8   9   0   1   2   3   4   5
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
      |                         IDLE TIMEOUT                          |
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

   IDLE TIMEOUT:  the idle timeout for the current session, specified as
      a 16 bit word in network order in units of 100 milliseconds.

   It is NOT an error for this TLV and the similar EDNS option to appear
   within the same session.  The client SHOULD pay attention to the most
   recently received value, regardless of which method was used to send
   it.

   The client SHOULD terminate the current session if it remains idle
   for longer than the specified timeout (and MAY of course terminate
   the session earlier).  The server MAY unilaterally terminate the
   connection at any time, but SHOULD allow the client to keep the
   connection open if further messages are received before the idle
   timeout expires.




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   << RB: this assumes that the EDNS OPT RR is added at the final stage
   of message processing, and therefore not affected by out-of-order
   processing - c.f. comment above about sequencing points >>

5.  IANA Considerations

5.1.  DNS Session Signaling OpCode Registration

   IANA are directed to assign the value TBD for the Session Signaling
   OpCode in the DNS OpCodes Registry.

5.2.  DNS Session Signaling Status Codes Registry

   IANA are directed to create the DNS Session Signaling Status Codes
   Registry, with initial values as follows:

     +------+----------+---------------------------------+-----------+
     | Code | Mnemonic | Description                     | Reference |
     +------+----------+---------------------------------+-----------+
     |    0 | NOERROR  | TLV processed successfully      | RFC-TBD1  |
     |      |          |                                 |           |
     |    4 | NOTIMP   | TLV not implemented             | RFC-TBD1  |
     |      |          |                                 |           |
     |    5 | REFUSED  | TLV declined for policy reasons | RFC-TBD1  |
     +------+----------+---------------------------------+-----------+

   Registration of additional Session Signaling Status Codes requires
   Standards Action.

5.3.  DNS Session Signaling Type Codes Registry

   IANA are directed to create the DNS Session Signaling Type Codes
   Registry, with initial values as follows:


















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   +----------+---------------------------------+----------+-----------+
   |     Type | Name                            | Status   | Reference |
   +----------+---------------------------------+----------+-----------+
   |        0 | Reserved                        |          | RFC-TBD1  |
   |          |                                 |          |           |
   |        1 | TypeCode Support                | Standard | RFC-TBD1  |
   |          |                                 |          |           |
   |   2 - 63 | Unassigned, reserved for        |          |           |
   |          | feature negotiation TLVs        |          |           |
   |          |                                 |          |           |
   |       64 | Terminate                       | Standard | RFC-TBD1  |
   |          |                                 |          |           |
   |       65 | Idle Timeout                    | Standard | RFC-TBD1  |
   |          |                                 |          |           |
   | 66 - 127 | Unassigned, reserved for        |          |           |
   |          | session management TLVs         |          |           |
   |          |                                 |          |           |
   |    127 - | Unassigned                      |          |           |
   |     3965 |                                 |          |           |
   |          |                                 |          |           |
   |   3968 - | Reserved for local /            |          |           |
   |     4031 | experimental use                |          |           |
   |          |                                 |          |           |
   |   4032 - | Reserved for future expansion   |          |           |
   |     4095 |                                 |          |           |
   +----------+---------------------------------+----------+-----------+

   Registration of additional Session Signaling Type Codes requires
   Expert Review. << RB: definition of process required? >>

6.  Security Considerations

   The authors are not aware of any specific security considerations
   introduced by this specification at this time.

7.  Acknowledgements

   TBW

8.  Normative References

   [RFC1035]  Mockapetris, P., "Domain names - implementation and
              specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
              November 1987, <http://www.rfc-editor.org/info/rfc1035>.







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

   [RFC6891]  Damas, J., Graff, M., and P. Vixie, "Extension Mechanisms
              for DNS (EDNS(0))", STD 75, RFC 6891, DOI 10.17487/
              RFC6891, April 2013,
              <http://www.rfc-editor.org/info/rfc6891>.

   [RFC7828]  Wouters, P., Abley, J., Dickinson, S., and R. Bellis, "The
              edns-tcp-keepalive EDNS0 Option", RFC 7828, DOI 10.17487/
              RFC7828, April 2016,
              <http://www.rfc-editor.org/info/rfc7828>.

Authors' Addresses

   Ray Bellis
   Internet Systems Consortium, Inc.
   950 Charter Street
   Redwood City  CA 94063
   USA

   Phone: +1 650 423 1200
   Email: ray@isc.org


   Stuart Cheshire
   Apple Inc.
   1 Infinite Loop
   Cupertino  CA 95014
   USA

   Phone: +1 408 974 3207
   Email: cheshire@apple.com


   John Dickinson
   Sinodun Internet Technologies
   Magadalen Centre
   Oxford Science Park
   Oxford  OX4 4GA
   United Kingdom








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   Allison Mankin
   Unaffiliated

   Email: allison.mankin@gmail.com


   Tom Pusateri
   Unaffiliated

   Phone: +1 843 473 7394
   Email: pusateri@bangj.com








































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