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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 22, 2017                                     Apple Inc.
                                                            J. Dickinson
                                                            S. Dickinson
                                                                 Sinodun
                                                               A. Mankin
                                                              Salesforce
                                                             T. Pusateri
                                                            Unaffiliated
                                                           July 21, 2016


                         DNS Session Signaling
                  draft-bellis-dnsop-session-signal-01

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
   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 22, 2017.

Copyright Notice

   Copyright (c) 2016 IETF Trust and the persons identified as the
   document authors.  All rights reserved.





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   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  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Protocol Details  . . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  Message Format  . . . . . . . . . . . . . . . . . . . . .   4
     3.2.  Message Handling  . . . . . . . . . . . . . . . . . . . .   4
     3.3.  TLV Format  . . . . . . . . . . . . . . . . . . . . . . .   5
   4.  Mandatory TLVs  . . . . . . . . . . . . . . . . . . . . . . .   6
     4.1.  Session Management Support TLVs . . . . . . . . . . . . .   6
       4.1.1.  "Not Implemented" . . . . . . . . . . . . . . . . . .   6
     4.2.  Session Management TLVs . . . . . . . . . . . . . . . . .   6
       4.2.1.  Start Session . . . . . . . . . . . . . . . . . . . .   6
       4.2.2.  Terminate Session . . . . . . . . . . . . . . . . . .   6
       4.2.3.  Idle Timeout  . . . . . . . . . . . . . . . . . . . .   7
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
     5.1.  DNS Session Signaling Opcode Registration . . . . . . . .   8
     5.2.  DNS Session Signaling Type Codes Registry . . . . . . . .   8
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   9
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   9
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   9
   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
   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 request message.



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   It should be noted that the message format (see Section 3.1) does not
   conform to the standard DNS packet format.

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 term "session" in the context of this document means the exchange
   of DNS messages over a single connection using an end-to-end
   transport protocol where:

   o  connections can be long-lived

   o  either end of the connection may initiate requests

   o  message delivery order is guaranteed

   o  it is guaranteed that the same two endpoints are in communication
      for the entire lifetime of the session.

   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 where a session may be established according to the
   definition above.  Standard DNS over TCP [RFC1035], and DNS over TLS
   [RFC7858] are appropriate protocols.  DNS over plain UDP is not
   appropriate since it fails on both the bi-directional initiation
   requirement and the message order delivery requirement.

   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.

   A server MUST NOT initiate Session Signaling messages until a client-
   initiated Session Signaling message is received first.  This




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   requirement is to ensure that the client does not observe unsolicited
   inbound messages until it has indicated its ability to handle them.

   Session Signaling support is therefore said to be confirmed from the
   client's point of view after the first session signaling TLV has been
   sent by that client and subsequently successfully acknowledged by the
   server.

   Use of Session Signaling by a client should be taken as an implicit
   request for a long-lived session.

3.1.  Message Format

   A message containing a Session Signaling OpCode does not conform to
   the usual DNS message format.  The 4 octet header format from
   [RFC1035] is however preserved, since that includes the message ID
   and OpCode and RCODE fields, and the QR bit that differentiates
   requests from responses.

   Each message MUST contain only a single TLV.

                                                1   1   1   1   1   1
        0   1   2   3   4   5   6   7   8   9   0   1   2   3   4   5
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
      |                          MESSAGE ID                           |
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
      |QR |    OpCode     |            Z              |     RCODE     |
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
      |                                                               |
      /                           TLV-DATA                            /
      /                                                               /
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

   The MESSAGE ID, QR, OpCode and RCODE fields have their usual meaning
   as defined in [RFC1035].

   The Z bits are currently unused, and SHOULD be set to zero (0) in
   requests and responses unless re-defined in a later specification.

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).





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   Every Session Signaling request message MUST elicit a response (which
   MUST have the same ID in the DNS message header as in the request).

   In order to preserve the correct sequence of state, Session Signaling
   requests MUST NOT be processed out of order.

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

   The RCODE value in a response uses a subset of the standard (non-
   extended) RCODE values from the IANA DNS RCODEs registry, interpreted
   as follows:

           +------+----------+---------------------------------+
           | Code | Mnemonic | Description                     |
           +------+----------+---------------------------------+
           |    0 | NOERROR  | TLV processed successfully      |
           |      |          |                                 |
           |    1 | FORMERR  | TLV format error                |
           |      |          |                                 |
           |    4 | NOTIMP   | Session Signaling not supported |
           |      |          |                                 |
           |    5 | REFUSED  | TLV declined for policy reasons |
           +------+----------+---------------------------------+

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-TYPE                          |
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
      |                        SESSION-LENGTH                         |
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
      |                                                               |
      /                         SESSION-DATA                          /
      /                                                               /
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

   SESSION-TYPE:  A 16 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.

   SESSION-DATA:  Type-code specific.




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4.  Mandatory TLVs

4.1.  Session Management Support TLVs

4.1.1.  "Not Implemented"

   Since the "NOTIMP" RCODE is required to indicate lack of support for
   the Session Signaling OpCode itself, the "Not Implemented" TLV (0)
   MUST be returned in response to a TLV that is not implemented by the
   responder.

   This TLV has no SESSION-DATA.

4.2.  Session Management TLVs

4.2.1.  Start Session

   The Start Session TLV (1) SHOULD be used by a client to indicate
   support for Session Signaling.  It MUST NOT be initiated by a server.

   It is not required that this TLV be used in every session - any valid
   client-initiated TLV will suffice to initiate Session Signaling
   support.  The intention of this TLV is to provide a suitable "No-Op"
   TLV to permit Session Signaling support to be negotiated without
   carrying any other information.

   This TLV has no SESSION-DATA.

   << RB: this could perhaps also be used as a real "no-op" message to
   provide application-level keep-alive pings >>

4.2.2.  Terminate Session

   The Terminate Session TLV (2) MAY be sent by a server to request that
   the client terminate the session.  It MUST NOT be initiated 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 requests over the existing session.

   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
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
      |                        RECONNECT DELAY                        |
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+



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   RECONNECT DELAY:  a time value, specified as a 16 bit word in network
      order in units of 100 milliseconds, within which the client MUST
      NOT establish a new session to the current server.

   The RECOMMENDED value is 10 seconds.  << RB: text required here about
   default values for load balancers, etc >>

4.2.3.  Idle Timeout

   The Idle Timeout TLV (3) has similar intent 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.  a client.  The definition
   of an idle session is as specified in [RFC7766].

   Messages generate by the client have no SESSION-DATA (whether in
   requests or responses).  A client-initiated Idle Timeout TLV allows
   the client to request the current timeout value, whereas a server-
   initiated request allows the server to unilaterally update the
   current timeout value.

   Messages generated by the server contain SESSION-DATA 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.

   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.

   A client / server pair that supports Session Signaling MUST NOT use
   the EDNS TCP KeepAlive option within any message once bi-directional
   Session Signaling support has been confirmed.

5.  IANA Considerations








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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 Type Codes Registry

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

   +-----------+--------------------------------+----------+-----------+
   |      Type | Name                           | Status   | Reference |
   +-----------+--------------------------------+----------+-----------+
   |         0 | Not implemented                |          | RFC-TBD1  |
   |           |                                |          |           |
   |         1 | Start Session                  | Standard | RFC-TBD1  |
   |           |                                |          |           |
   |         2 | Terminate Session              | Standard | RFC-TBD1  |
   |           |                                |          |           |
   |         3 | Idle Timeout                   | Standard | RFC-TBD1  |
   |           |                                |          |           |
   |    4 - 63 | Unassigned, reserved for       |          |           |
   |           | session management TLVs        |          |           |
   |           |                                |          |           |
   |      64 - | Unassigned                     |          |           |
   |     63487 |                                |          |           |
   |           |                                |          |           |
   |   63488 - | Reserved for local /           |          |           |
   |     64511 | experimental use               |          |           |
   |           |                                |          |           |
   |   64512 - | Reserved for future expansion  |          |           |
   |     65535 |                                |          |           |
   +-----------+--------------------------------+----------+-----------+

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

6.  Security Considerations

   If this mechanism is to be used with DNS over TLS, then these
   messages are subject to the same constraints as any other DNS over
   TLS messages and MUST NOT be sent in the clear before the TLS session
   is established.








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7.  Acknowledgements

   TBW

8.  References

8.1.  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>.

   [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>.

   [RFC7766]  Dickinson, J., Dickinson, S., Bellis, R., Mankin, A., and
              D. Wessels, "DNS Transport over TCP - Implementation
              Requirements", RFC 7766, DOI 10.17487/RFC7766, March 2016,
              <http://www.rfc-editor.org/info/rfc7766>.

   [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>.

8.2.  Informative References

   [RFC7858]  Hu, Z., Zhu, L., Heidemann, J., Mankin, A., Wessels, D.,
              and P. Hoffman, "Specification for DNS over Transport
              Layer Security (TLS)", RFC 7858, DOI 10.17487/RFC7858, May
              2016, <http://www.rfc-editor.org/info/rfc7858>.

Authors' Addresses











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   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

   Email: jad@sinodun.com


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

   Email: sara@sinodun.com


   Allison Mankin
   Salesforce

   Email: allison.mankin@gmail.com







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   Tom Pusateri
   Unaffiliated

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














































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