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Versions: 00 01                                                         
TRAM                                                        P. Martinsen
Internet-Draft                                                     Cisco
Intended status: Standards Track                               J. Uberti
Expires: March 19, 2015                                           Google
                                                           O. Moskalenko
                                                      September 15, 2014

                Single SOcket Dual Allocation with TURN


   This draft describes a simple method for allocating one IPv4 and one
   IPv6 relay address from a single ALLOCATE request to the TURN server.
   This saves local ports on the client, reduces the number of
   candidates gathered by the client, and reduces the number of messages
   sent between the client and the TURN server.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC 2119 [RFC2119].

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 March 19, 2015.

Copyright Notice

   Copyright (c) 2014 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.  Creating an Allocation  . . . . . . . . . . . . . . . . . . .   3
     2.1.  Sending an Allocate Request . . . . . . . . . . . . . . .   3
     2.2.  Receiving an Allocate Request . . . . . . . . . . . . . .   3
     2.3.  Receiving an Allocate Success Response  . . . . . . . . .   5
     2.4.  Receiving an Allocate Error Response  . . . . . . . . . .   5
   3.  Refreshing an Allocation  . . . . . . . . . . . . . . . . . .   5
     3.1.  Sending a Refresh Request . . . . . . . . . . . . . . . .   6
     3.2.  Receiving a Refresh Request . . . . . . . . . . . . . . .   6
     3.3.  CreatePermission  . . . . . . . . . . . . . . . . . . . .   6
       3.3.1.  Sending a CreatePermission Request  . . . . . . . . .   6
       3.3.2.  Receiving a CreatePermission Request  . . . . . . . .   7
   4.  Channels  . . . . . . . . . . . . . . . . . . . . . . . . . .   7
   5.  Implementation Status . . . . . . . . . . . . . . . . . . . .   7
     5.1.  open-sys  . . . . . . . . . . . . . . . . . . . . . . . .   7
     5.2.  NATTools  . . . . . . . . . . . . . . . . . . . . . . . .   8
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   9
   8.  Normative References  . . . . . . . . . . . . . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   The main motivation for this draft is to reduce the number of local
   ports on the client, reduce the number of candidates gathered during
   the discovery process, and reduce the number of messages that need to
   be exchanged to allocate the relay addresses needed for ICE.

   Reducing the number of local ports is important as it saves resources
   at three places in the network.  First, the number of open ports on
   the client is reduced, leading to fewer host candidates.  Secondly,
   with fewer local host ports there will be fewer NAT bindings for the
   NAT to keep track of, and fewer server reflexive candidates.  Lastly,
   with a single 5-tuple in use, it reduces the number of open ports the
   TURN server needs to open on the interface towards the client
   (Private side).  As ports are a scarce resource (16-bit number)

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   preserving them on the NAT and a the TURN server can make large scale
   deployments easier.

2.  Creating an Allocation

   The behavior specified here affects the processing defined in
   Section 6 of [RFC5766] and Section 4 of [RFC6156].

2.1.  Sending an Allocate Request

   A client that wishes to obtain one IPv6 and one IPv4 by sending one
   Allocate request MUST include two REQUESTED-ADDRESS-FAMILY
   attributes, one for each address family, in the Allocate request that
   it sends to the TURN server.  The order of the REQUESTED-ADDRESS-
   FAMILY is arbitrary, because the server either understands SSODA
   (then the order does not matter) or the server does not understand
   SSODA (then the server behavior is undefined - it may return a 400
   error, or it may take the first attribute, or it may take the last
   attribute).  Multiple candidates of the same family are not
   supported; the client MUST NOT include more than one REQUESTED-
   ADDRESS-FAMILY attribute for a given address family.  The mechanism
   to formulate an Allocate request is described in Section 6.1 of

   The SSODA mechanism is not available when using the odd/ even port
   allocation scheme.  Clients MUST NOT include a REQUESTED-ADDRESS-
   FAMILY attribute in an Allocate request that contains a RESERVATION-
   TOKEN attribute.  Clients MUST NOT include a second REQUESTED-
   ADDRESS-FAMILY attribute in an Allocate request that contains an
   EVEN-PORT attribute.

2.2.  Receiving an Allocate Request

   Once a server has verified that the request is authenticated and has
   not been tampered with, the TURN server processes the Allocate
   request following the rules in [RFC5766] and [RFC6156]..  Only one
   REQUESTED-ADDRESS-FAMILY attribute with the same family value is
   allowed in the request.  If two attributes with the same family value
   exist the server MUST return 400 Bad Request error.

   If no REQUESTED-ADDRESS-FAMILY attributes are present, the server
   MUST treat this as if the request contained a single REQUESTED-
   ADDRESS-FAMILY specifying the IPv4 address family.

   If the server can successfully process the request, it allocates a
   relay address for each of the REQUESTED-ADDRESS-FAMILY attributes
   present in the Allocate request.  The allocated relay addresses are
   returned in separate XOR-RELAYED-ADDRESS attributes in the Allocate

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   response message.  The ordering of the XOR-RELAYED-ADDRESS attributes
   in the response is arbitrary.

   If the server cannot satisfy the request at all, because none of the
   specified address families are supported, the server MUST return a
   440 error code, as indicated in [RFC6156].

   If the server cannot satisfy the request at all, because the server
   could not allocate any of the specified addresses, the server MUST
   return a 508 (Insufficient Capacity) error code as indicated in

   If some of the requested address could be allocated, but some could
   not, either because the requested address family is not supported, or
   the server currently lacks capacity, the server MUST indicate this
   partial success by returning an Allocate Success Response that
   contains XOR-RELAYED-ADDRESS attributes for the addresses that were
   successfully allocated, as well as XOR-RELAYED-ADDRESS with ANY
   addresses (that is, IPv4 address or IPv6 address [::0]:0)
   corresponding to the address families that could not be allocated.
   This will notify the client that the desired REQUESTED-ADDRESS-FAMILY
   was understood, but could not be allocated.  A success response with
   ANY addresses MUST NOT be returned if all allocation requests cannot
   be satisfied; instead, an error response should be returned, as
   indicated above.

   This somewhat unusual pattern of partial success is used to avoid the
   need for an additional round-trip when the client just wants whatever
   address families the TURN server supports.

   Note that while allocating multiple address families at the same time
   is supported, doing this sequentially is not.  The server MUST reject
   any attempt to "add" an address family to an existing allocation with
   a 437 (Allocation Mismatch) error code.

   [OPEN ISSUE 1: do we need to include REQUESTED-ADDRESS-FAMILY
   attribute(s) with failed address family (or families) to help the
   client to recognize whether this is an "old" non-SSODA server or a
   "new" SSODA-supporting server ?]

   [OPEN ISSUE 2: do we have to consider a particular ordering of
   the ALLOCATE request and response ? Can attribute ordering provide
   some benefits in this case ?]

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2.3.  Receiving an Allocate Success Response

   This section describes how the client must react on receiving a
   response to the dual allocation request.  If the client is not using
   dual allocation, then the behavior is the same as the rules in
   [RFC5766] and in [RFC6156].

   If the client receives an Allocate Success Response containing a non-
   ANY (ANY as defined above) XOR-RELAYED-ADDRESS attribute for each of
   the REQUESTED-ADDRESS-FAMILY attributes in the Allocate request sent
   by the client, the client knows that the TURN server supports
   multiple address family allocation over a single socket.  All relay
   addresses can now be used by the client.

   If the Allocate response contains both usable XOR-RELAYED-ADDRESS
   attributes as well as ANY XOR-RELAYED-ADDRESS attributes, then the
   client knows that the TURN server "understands" dual allocation SSODA
   request, but the server either does not support one of the requested
   address families or cannot currently allocate an address of that
   family.  The allocated non-ANY address can be used, but the client
   SHOULD NOT try to allocate any of the unsupported families on a
   different 5-tuple.

   If the Allocate Response contains only one XOR-RELAYED-ADDRESS
   attribute, then the client knows that the TURN server does not
   support SSODA.  The client can retry the missing address family
   allocations on new 5-tuples, if desired.  Subsequent Allocate
   requests towards the same TURN server SHOULD NOT include multiple

2.4.  Receiving an Allocate Error Response

   When doing dual allocation, if the client receives an Allocate error
   response with the 440 (Unsupported Address Family) error code, then
   the client knows that the TURN server does not support any of the
   desired address families, or might be a non-SSODA server that
   misinterpreted the included REQUESTED-ADDRESS-FAMILY attributes in
   the Allocate request.  The client SHOULD retry its IPv4 request on
   the same 5-tuple, with no REQUESTED-ADDRESS-FAMILY attribute, and MAY
   retry other address families on different local ports, by sending an
   Allocate request with only one REQUESTED-ADDRESS-FAMILY attribute.

3.  Refreshing an Allocation

   The behavior specified here affects the processing defined in
   Section 7 of [RFC5766] and Section 5 of [RFC6156].  This section MUST
   only be used if the client has verified that the TURN server supports

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   SSODA during the allocation creation described in Section 2.1.
   Otherwise, revert back to RFC 5766 or RFC 6156 behavior.

3.1.  Sending a Refresh Request

   To perform an allocation refresh, the client generates a Refresh
   Request as described in Section 7.1 of [RFC5766].  When refreshing a
   dual allocation, the client SHOULD include one or more REQUESTED-
   ADDRESS-FAMILY attributes describing the the family types that should
   be refreshed; the client MUST only include family types that it
   previously allocated and has not yet deleted.  When refreshing a
   (single) allocation on a server that does not not support SSODA,
   REQUESTED-ADDRESS-FAMILY should be omitted, for backwards

   This process can also be used to delete an allocation of a specific
   address type, by setting the lifetime of that refresh request to 0.
   It is possible to delete one or more allocations depending on how
   many REQUESTED-ADDRESS-FAMILY attributes are included.  Deleting a
   single allocation destroys any permissions or channels associated
   with that particular allocation; it MUST NOT affect any permissions
   or channels associated with allocations for other address families.

3.2.  Receiving a Refresh Request

   The server refreshes the allocated address families that match the
   supplied REQUESTED-ADDRESS-FAMILY values.  If any of the values in
   the request do not match a currently allocated address, the server
   MUST respond with a 437 (Allocation Mismatch) error.  [OPEN ISSUE:
   discuss whether this is the right error code for the situation] If no
   REQUESTED-ADDRESS-FAMILY is present, the request should be treated as
   applying to all current allocations, for backward compatibility.

   The server MUST then refresh or delete the specified allocations, and
   return a Refresh Success Response.

3.3.  CreatePermission

   The behavior specified here affects the processing defined in
   Section 9 of [RFC5766] and Section 6 of [RFC6156]

3.3.1.  Sending a CreatePermission Request

   The client MUST only include XOR-PEER-ADDRESS attributes with
   addresses that match an address family of one of the currently
   allocated addresses.

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3.3.2.  Receiving a CreatePermission Request

   If an XOR-PEER-ADDRESS attribute contains an address of an address
   family different than that any of the relayed transport addresses
   allocated, the server MUST generate an error response with the 443
   (Peer Address Family Mismatch) response code, which is defined in
   Section 6.2.1 of [RFC6156].

4.  Channels

   The session channels setup process follows the same rules as in
   [RFC5766] and in [RFC6156]; the client is allowed to set up multiple
   channels within the same 5-tuple session.  However, when using SSODA
   and dual allocation, the peer addresses of those channels may be of
   different families.  Thus, a single 5-tuple session may create
   several IPv4 channels and several IPv6 channels.

5.  Implementation Status

   [Note to RFC Editor: Please remove this section and reference to
   [RFC6982] prior to publication.]

   This section records the status of known implementations of the
   protocol defined by this specification at the time of posting of this
   Internet-Draft, and is based on a proposal described in [RFC6982].
   The description of implementations in this section is intended to
   assist the IETF in its decision processes in progressing drafts to
   RFCs.  Please note that the listing of any individual implementation
   here does not imply endorsement by the IETF.  Furthermore, no effort
   has been spent to verify the information presented here that was
   supplied by IETF contributors.  This is not intended as, and must not
   be construed to be, a catalog of available implementations or their
   features.  Readers are advised to note that other implementations may

   According to [RFC6982], "this will allow reviewers and working groups
   to assign due consideration to documents that have the benefit of
   running code, which may serve as evidence of valuable experimentation
   and feedback that have made the implemented protocols more mature.
   It is up to the individual working groups to use this information as
   they see fit".

5.1.  open-sys

   Organization:   This is a public project, the full list of authors
      and contributors here: http://turnserver.open-sys.org/downloads/

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   Description:   A mature open-source TURN server specs implementation
      (RFC 5766, RFC 6062, RFC 6156, etc) designed for high-performance
      applications, especially geared for WebRTC.

   Implementation:  http://code.google.com/p/coturn/

   Level of maturity:   The TURN SSODA extension implementation can be
      qualified as "production" - it is well tested and fully
      implemented, but not widely used, yet..

   Coverage:   Fully implements SSODA this draft.

   Licensing:   BSD: http://turnserver.open-sys.org/downloads/LICENSE

   Implementation experience:   Few changes to existing code

   Contact:   Oleg Moskalenko <mom040267@gmail.com>.

5.2.  NATTools

   Organization:   Cisco

   Description:   NATTools is a set of client side focused ICE/TURN/STUN

   Implementation:   https://github.com/cisco/NATTools

   Level of maturity:   Running test code works well.  Not tested in any
      released products.

   Coverage:   Implement this draft.

   Licensing:   BSD

   Implementation experience:   Simple, few changes to the client.

   Contact:   Paal-Erik Martinsen <palmarti@gmail.com>.

6.  Security Considerations

   As the client can ask for two allocations for each allocation request
   sent, the TURN server can be DOS attacked with fewer messages.
   However this problem is minimal as the messages needs to be
   authenticated first as described in RFC 5766 [RFC5766].

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7.  Acknowledgements

   Authors would like to thank Simon Perreault for providing ideas
   direction and insight.  Jonathan Lennox provided excellent feedback
   on the mailing list.

8.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [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.

   [RFC6156]  Camarillo, G., Novo, O., and S. Perreault, "Traversal
              Using Relays around NAT (TURN) Extension for IPv6", RFC
              6156, April 2011.

   [RFC6982]  Sheffer, Y. and A. Farrel, "Improving Awareness of Running
              Code: The Implementation Status Section", RFC 6982, July

Authors' Addresses

   Paal-Erik Martinsen
   Cisco Systems, Inc.
   Philip Pedersens vei 20
   Lysaker, Akershus  1366

   Email: palmarti@cisco.com

   Justin Uberti
   Kirkland, WA

   Email: justin@uberti.name

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   Oleg Moskalenko
   Walnut Creek, CA

   Email: mom040267@gmail.com
   URI:   https://code.google.com/p/coturn/

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