[Docs] [txt|pdf|xml|html] [Tracker] [Email] [Diff1] [Diff2] [Nits]

Versions: 00 01 02 03 04 05 06 07

MMUSIC                                                           D. Wing
Internet-Draft                                                  T. Reddy
Intended status: Standards Track                                P. Patil
Expires: December 19, 2014                                  P. Martinsen
                                                                   Cisco
                                                           June 17, 2014


                        Mobility with ICE (MICE)
                   draft-wing-mmusic-ice-mobility-07

Abstract

   This specification describes how endpoint mobility can be achieved
   using ICE.

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 December 19, 2014.

Copyright Notice

   Copyright (c) 2014 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
   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.




Wing, et al.            Expires December 19, 2014               [Page 1]

Internet-Draft                    MICE                         June 2014


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Notational Conventions . . . . . . . . . . . . . . . . . . . .  3
   3.  Break Before Make  . . . . . . . . . . . . . . . . . . . . . .  4
     3.1.  Absence of other interfaces in Valid list  . . . . . . . .  5
       3.1.1.  Receiving ICE Mobility event . . . . . . . . . . . . .  6
     3.2.  Keeping unused relayed candidates active . . . . . . . . .  7
     3.3.  New STUN Attributes  . . . . . . . . . . . . . . . . . . .  8
   4.  Make Before Break  . . . . . . . . . . . . . . . . . . . . . .  8
   5.  Comparison to ICE Restart and Trickle ICE  . . . . . . . . . .  8
     5.1.  Break Before Make - ICE Restart  . . . . . . . . . . . . .  9
     5.2.  Break Before Make - Trickle ICE  . . . . . . . . . . . . . 10
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 10
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 11
   8.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11
   9.  Change History . . . . . . . . . . . . . . . . . . . . . . . . 11
     9.1.  Changes from draft-wing-mmusic-ice-mobility-00 to -01  . . 11
     9.2.  Changes from draft-wing-mmusic-ice-mobility-01 to -02  . . 11
     9.3.  Changes from draft-wing-mmusic-ice-mobility-02 to -03  . . 11
     9.4.  Changes from draft-wing-mmusic-ice-mobility-03 to -04  . . 12
     9.5.  Changes from draft-wing-mmusic-ice-mobility-04 to -05  . . 12
     9.6.  Changes from draft-wing-mmusic-ice-mobility-05 to -06  . . 12
     9.7.  Changes from draft-wing-mmusic-ice-mobility-06 to -07  . . 12
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
     10.1. Normative References . . . . . . . . . . . . . . . . . . . 12
     10.2. Informative References . . . . . . . . . . . . . . . . . . 12
   Appendix A.    . . . . . . . . . . . . . . . . . . . . . . . . . . 13
     A.1.  Presence of other interfaces in Valid list . . . . . . . . 13
       A.1.1.  Receiving ICE Mobility event . . . . . . . . . . . . . 14
     A.2.  Losing an Interface  . . . . . . . . . . . . . . . . . . . 14
       A.2.1.  Keeping unused candidates in the valid list active . . 15
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16


















Wing, et al.            Expires December 19, 2014               [Page 2]

Internet-Draft                    MICE                         June 2014


1.  Introduction

   When moving between networks, an endpoint has to change its IP
   address.  This change breaks upper layer protocols such as TCP and
   RTP.  Various techniques exist to prevent this breakage, all tied to
   making the endpoint's IP address static (e.g., Mobile IP, Proxy
   Mobile IP, LISP).  Other techniques exist, which make the upper layer
   protocol ambivalent to IP address changes (e.g., SCTP).  The
   mechanisms described in this document are in that last category.

   ICE [RFC5245] ensures two endpoints have a working media path between
   them, and is typically used by Internet-connected interactive media
   systems (e.g., SIP endpoints).  ICE does not expect either the local
   host or the remote host to change their IP addresses.  Although ICE
   does allow an "ICE restart", this is done by sending a re-INVITE
   which goes over the SIP signaling path.  The SIP signaling path is
   often slower than the media path (which needs to be recovered as
   quickly as possible), consumes an extra half round trip, and incurs
   an additional delay if the mobility event forces the endpoint to re-
   connect with its SIP proxy.  When a device changes its IP address, it
   is necessary for it to re-establish connectivity with its SIP proxy,
   which can be performed in parallel with the steps described in this
   document.  This document describes how mobility is performed entirely
   in the media path, without the additional delay of re-establishing
   SIP connectivity, issuing a new offer/answer, or the complications of
   multiple SIP offers.  This document considers re-establishing bi-
   directional media the most critical aspect of a successful mobility
   event, and its efforts are towards meeting that goal.

   This document proposes a mechanism to achieve RTP mobility when both
   endpoints support MICE.  When both endpoints support MICE, ICE itself
   can be used to provide mobility.  When only one endpoint supports
   MICE, a TURN server provides mobility as described in
   [I-D.wing-tram-turn-mobility].  Both mobility techniques work across
   and between network types (e.g., between 3G and wired Internet
   access), so long as the client can still access the remote ICE peer
   or TURN server.

   Readers are assumed to be familiar with ICE [RFC5245].


2.  Notational 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].

   This note uses terminology defined in [RFC5245], and the following



Wing, et al.            Expires December 19, 2014               [Page 3]

Internet-Draft                    MICE                         June 2014


   additional terminology:

   Break Before Make:  The initially selected interface for
      communication may become unavailable (e.g due to loss of coverage
      when moving out of a WiFi hotspot) and new interfaces may become
      available due to administrative action (e.g manual activation of a
      specific connectivity technology) or due to dynamic conditions
      (e.g.  Entering coverage area of a wireless network).

   Make Before Break:  The initially selected interface for
      communication may become deprioritized (e.g new interface becoming
      available and it's per bit cost is cheaper and the connection
      speed is faster than existing interface used for communication).

   Simultaneous Mobility:  If both the endpoints are mobile and roam at
      the same time between networks.


3.  Break Before Make

   When both endpoints support ICE, ICE itself can provide mobility
   functions.  One of the primary aspects of ICE is its address
   gathering, wherein ICE has each endpoint determine all of the IP
   addresses and ports that might be usable for that endpoint and
   communicate that list of addresses and ports to its peer, usually
   over SDP.  That enables the next primary aspect of ICE, which is its
   connectivity checks: each ICE endpoint sends a connectivity check
   from a checklist created by the local and remote candidates exchanged
   in the initial offer/answer exchange.  When the ICE endpoint checks
   the mapped address from the STUN response during ICE connectivity
   checks and finds that the transport address does not match any of the
   local candidates that the ICE agent knows about, the mapped address
   represents a new candidate -- a peer reflexive candidate.  This will
   cause the endpoint to construct a new pair and insert it into the
   local checklist (Section 7.2.1.3 of [RFC5245]).  ICE Mobility (MICE)
   takes advantage of that existing ICE functionality to provide faster
   mobility.

   Endpoints that support ICE Mobility perform ICE normally, and MUST
   also include the MOBILITY-SUPPORT attribute in all of their STUN
   requests and their STUN responses.  The inclusion of this attribute
   allows the ICE peer to determine if it can achieve mobility using ICE
   or needs to use TURN.  To force the use of TURN to achieve ICE
   mobility, the ICE endpoint SHOULD NOT respond to ICE connectivity
   checks that have an IP address and port different from the TURN
   server, unless those connectivity checks contain the MOBILITY-SUPPORT
   attribute.  In this way, the remote peer will think those other
   candidates are invalid (because its connectivity checks did not



Wing, et al.            Expires December 19, 2014               [Page 4]

Internet-Draft                    MICE                         June 2014


   succeed).

   After concluding ICE and moving to the ICE completed state (see
   Section 8 of [RFC5245]) either endpoint or both endpoints can
   initiate ICE Mobility, no matter if it was the Controlling Agent or
   the Controlled Agent during normal ICE processing.

3.1.  Absence of other interfaces in Valid list

   When the interface currently being used for communication becomes
   unavailable then ICE agent acquires a list of interfaces that are
   available and based on the locally configured host policy
   preferences, the ICE endpoint performs ICE Mobility using one of the
   available interfaces.  In this case local candidates from the
   selected interface are not present in the valid list.  ICE Mobility
   is performed by:

   1.  The ICE agent remembers the remote host/server reflexive/peer
       reflexive candidates for each component of the media streams
       previously used from the valid list before clearing its ICE check
       list and ICE Valid List.

   2.  The ICE endpoint gathers host candidates of the same address
       family as the remote peer on the new interface, forms a check
       list by creating candidate pairs with local host candidates and
       remote host/server-reflexive candidates collected in step 1,
       performs "Computing Pair Priority and Ordering Pairs" (Section
       5.7.2 of [RFC5245]), "Pruning the Pairs" (Section 5.7.3 of
       [RFC5245], "Computing states" (Section 5.7.4 of [RFC5245]).

   3.  The ICE endpoint initiates ICE connectivity checks on those
       candidates from the check list in the previous step, and includes
       the MOBILITY-EVENT attribute in those connectivity checks.

   4.  The ICE endpoint acts as controlling agent and the ICE
       connectivity check from the previous step SHOULD also include the
       USE-CANDIDATE attribute to signal an aggressive nomination (see
       Section 2.6 of [RFC5245]).

   5.  The ICE endpoint performs "Discovering Peer Reflexive Candidates"
       (Section 7.1.3.2.1 of [RFC5245]), "Constructing a Valid Pair"
       (Section 7.1.3.2.2 of [RFC5245]), "Updating Pair States" (Section
       7.1.3.2.3 of [RFC5245]), and "Updating the Nominated Flag"
       (Section 7.1.3.2.4 of [RFC5245]).  When the valid list contains a
       candidate pair for each component then ICE processing is
       considered complete for the media stream and ICE agent can start
       sending media using the nominated candidate pair.




Wing, et al.            Expires December 19, 2014               [Page 5]

Internet-Draft                    MICE                         June 2014


   6.  Once ICE connectivity checks for all of the media streams are
       completed, the controlling ICE endpoint follows the procedures in
       Section 11.1 of [RFC5245], specifically to send updated offer if
       the candidates in the m and c lines for the media stream (called
       the DEFAULT CANDIDATES) do not match ICE's SELECTED CANDIDATES
       (also see Appendix B.9 of [RFC5245]).

   The ICE endpoint even after Mobility using ICE is successful can
   issue an updated offer indicating ICE restart if connectivity checks
   using higher priority candidate pairs are not successful.

   Mobility using ICE could fail in case of Simultaneous Mobility or if
   the ICE peer is behind NAT that performs Address-Dependent Filtering
   (see Section 5 of [RFC5245]).  Hence the ICE endpoint in parallel
   will re-establish connection with the SIP proxy.  It will then
   determine whether to initiate ICE restart under the following
   conditions:

   a.  After re-establishing connection with the SIP proxy and before
       sending new offer to initiate ICE restart if Mobility using ICE
       is successful then stop sending the new offer.

   b.  After successful negotiation of updated offer/answer to initiate
       ICE restart, proceed with ICE restart and stop Mobility using ICE
       if ICE checks are in the Running/Failed states or ICE is
       partially successful and not yet reached ICE complete state.
       It's not implementation friendly to have to two checks running in
       parallel.  ICE restart can re-use partial successful ICE
       connectivity check results from Mobility using ICE if required as
       optimization.

3.1.1.  Receiving ICE Mobility event

   A STUN Binding Request containing the MOBILITY-EVENT attribute MAY be
   received by an ICE endpoint.  The agent MUST use short-term
   credential to authenticate the STUN request containing the MOBILITY-
   EVENT attribute and perform a message integrity check.  The ICE
   endpoint will generate STUN Binding Response containing the MOBILE-
   SUPPORT attribute and the ICE agent takes role of controlled agent.
   If STUN Request containing the MOBILITY-EVENT attribute is received
   before the endpoint is in the ICE Completed state, it should be
   silently discarded.

   The agent remembers the highest-priority nominated pairs in the Valid
   list for each component of the media stream, called the previous
   selected pairs before removing all the selected candidate pairs from
   the Valid List .  It continues sending media to that address until it
   finishes with the steps described below.  Because those packets might



Wing, et al.            Expires December 19, 2014               [Page 6]

Internet-Draft                    MICE                         June 2014


   not be received due to the mobility event, it MAY cache a copy of
   those packets.

   1.  The ICE endpoint constructs a pair whose local candidate is equal
       to the transport address on which the STUN request was received
       with MOBILITY-EVENT, USE-CANDIDATE attributes and a remote
       candidate equal to the source transport address where the STUN
       request came from.

   2.  The ICE endpoint will add this pair to the valid list if not
       already present.

   3.  The agent sets the nominated flag for that pair in the valid pair
       to true.  ICE processing is considered complete for a media
       stream if the valid list contains a selected candidate pair for
       each component and ICE agent can start sending media.

   The ICE endpoint will follow Steps 1 to 3 when subsequent STUN
   Binding Requests are received with MOBILITY-EVENT and USE-CANDIDATE
   attributes.

3.2.  Keeping unused relayed candidates active

   The ICE endpoints can maintain the relayed candidates active even
   when not actively used, so that relayed candidates can be tried if
   ICE connectivity checks using other candidate types fails.  The ICE
   agent will have to create permissions in the TURN server for the
   remote relayed candidate IP addresses and perform the following
   steps:

   1.  The ICE agent will keep the relayed candidates alive using
       Refresh transaction, as described in [RFC5766].

   2.  When the endpoint IP address changes due to mobility, the ICE
       agent will refresh it's allocation with TURN server using
       [I-D.wing-tram-turn-mobility].

   3.  The ICE agent will pair local and remote relayed candidates for
       connectivity checks when performing the steps in Section 3.1.

   4.  If the ICE connectivity check succeeds only with local and remote
       relayed candidates, it suggests that either other peer is roaming
       at the same time or is behind Address-Dependent Filtering NAT.
       The ICE agent adds the relayed candidate pair to the valid list
       and marks it as selected.  The ICE agent can now send media using
       the newly selected relayed candidate pair.  The Mobile device
       must re-establish connection with SIP proxy, issue an updated
       offer indicating ICE restart so that media can switched to



Wing, et al.            Expires December 19, 2014               [Page 7]

Internet-Draft                    MICE                         June 2014


       higher-priority candidate pairs.

   This approach assists Mobility using ICE to succeed but brings in
   additional overhead of maintaining relayed candidates.In case of
   Simultaneous Mobility, host candidates can change for both the
   endpoints by maintaining relayed candidates and using
   [I-D.wing-tram-turn-mobility], media session can be established using
   the relayed candidate pair.

3.3.  New STUN Attributes

   Three new attributes are defined by this section: MOBILITY-EVENT,
   MOBILITY-SUPPORT.

   The MOBILITY-EVENT attribute indicate the sender experienced a
   mobility event.  This attribute has no value, thus the attribute
   length field MUST always be 0.  Rules for sending and interpretation
   of receiving are described above.

   The MOBILITY-SUPPORT attribute indicates the sender supports ICE
   Mobility, as defined in this document.  This attribute has no value,
   thus the attribute length field MUST always be 0.  Rules for sending
   and interpretation of receiving are described above.


4.  Make Before Break

   When a new interface comes up and initially selected interface
   becomes deprioritized (e.g due to a low cost interface becoming
   available).  The ICE endpoint re-connects to the SIP proxy using the
   new interface, gather candidates, exchange updated offer/exchange to
   restart ICE.  Once ICE processing has reached the Completed state
   then the ICE endpoint can successfully switch the media over to the
   new interface.  The interface initially used for communication can
   now be turned off without disrupting communications.


5.  Comparison to ICE Restart and Trickle ICE

   There has been some concern that ICE Mobility is unnecessary, and
   that an ICE restart (section 9.1.1.1 of [RFC5245]) would provide
   exactly the same functionality as ICE Mobility.  These sections
   examine how ICE restart and Trickle ICE
   [I-D.rescorla-mmusic-ice-trickle] compare with ICE Mobility.







Wing, et al.            Expires December 19, 2014               [Page 8]

Internet-Draft                    MICE                         June 2014


5.1.  Break Before Make - ICE Restart

   o  If ICE Restart is used for RTP Mobility then in case of Break
      before Make,

      1.  Before the endpoint can send an ICE restart message, it has to
          first re-establish communication with its SIP proxy.  This
          consumes one round-trip for both TCP and UDP.  If the
          connection is protected with TLS (TCP) or DTLS (UDP), we can
          assume TLS session resumption [RFC5077] will be used to reduce
          the number of TLS messages.  With TLS session resumption, this
          consumes 1 round trip.  If TLS session resumption is not
          available, a full TLS handshake consumes 2 round trips.  This
          is a total of 2 round trips (with session resumption) to 3
          round trips (without session resumption), which is multiplied
          by the round trip time to the SIP proxy.  The round trip time
          is dependent on a particular network or deployment, for
          example in second (2.5G), third (3G) generation wireless
          networks and satellite communication round trip time could be
          higher than 250ms.  These calculations are only considering
          the network round-trip time and do not consider the wall-clock
          time to validate the TLS certificates or generate the TLS keys
          on the TLS client or the TLS server, which would make this
          longer.

      2.  While performing the above steps to re-establish SIP
          connectivity with its SIP proxy, the endpoint will gather host
          candidates which incur no network traffic, server-reflexive
          candidates which incur a round-trip to a STUN server, and
          relayed candidates which incurs three round trips (two for re-
          authentication and one for creating the TURN permission).  The
          STUN and TURN communications can be performed in parallel with
          the SIP connectivity check from step (1), above.

      3.  The endpoints through the SIP server will exchange offer/
          answer.  The SIP server could also be located halfway around
          the world from the endpoints and the delay could be
          significant.  For SIP over UDP the endpoint will have send a
          SIP request and wait for the response to arrive.

      4.  ICE restart requires sending a new INVITE.  A new INVITE
          cannot be sent if there is an open SIP dialog, such as a
          previous INVITE.  This means rapid mobility events will not
          work well, and there is also an increased likelihood for glare
          (both endpoints sending INVITEs at the same time).






Wing, et al.            Expires December 19, 2014               [Page 9]

Internet-Draft                    MICE                         June 2014


5.2.  Break Before Make - Trickle ICE

   o  If Trickle ICE [I-D.rescorla-mmusic-ice-trickle] is used for RTP
      Mobility then in case of Break before Make,

      1.  Trickle ICE can begin connectivity checks while the endpoint
          is still gathering candidates and can considerably shorten the
          time necessary for ICE processing to complete.  It still
          involves the overhead of step 1 explained in section
          Section 5.1.

      2.  The endpoint would learn host candidates and inform them to
          the remote peer in offer, the remote peer will provide its
          candidates in answer.  The host, server reflexive, peer
          reflexive and relayed candidates of the remote peer may not
          change and the remote peer does not have to gather the
          candidates again.  Trickle ICE will test local host candidates
          with all types of remote candidates provided by the remote
          peer in the answer.

          a.  If the endpoint is not behind NAT and the ICE peer is
              behind NAT performing endpoint dependent filtering (or
              firewall blocking unsolicited incoming traffic) then ICE
              connectivity checks initiated by the endpoint to the
              remote peer will succeed as a consequence of suicide ICE
              connectivitivy check packets.

          b.  If the endpoint is behind NAT and ICE peer is behind
              endpoint-dependent filtering NAT then ICE connectivity
              checks using the first offer/answer will fail but will
              later succeed in subsequent offer/answer where the
              endpoint provides server-reflexive candidates.

      3.  Trickle ICE must be supported by both endpoints for it be
          used.

   o  If both endpoints support TRICKLE ICE then it is RECOMMENDED that
      TRICKLE ICE be tried instead of ICE restart in steps (a) and (b)
      of Section 3.1.


6.  IANA Considerations

   IANA is requested to add the following attributes to the STUN
   attribute registry [iana-stun],

   o  MOBILITY-EVENT (0x802, in the comprehension-required range)




Wing, et al.            Expires December 19, 2014              [Page 10]

Internet-Draft                    MICE                         June 2014


   o  MOBILITY-SUPPORT (0x8000, in the comprehension-optional range)


7.  Security Considerations

   A mobility event only occurs after both ICE endpoints have exchanged
   their ICE information.  Thus, both username fragments are already
   known to both endpoints.  Each endpoint contributes at least 24 bits
   of randomness to the ice-ufrag (Section 15.4 of [RFC5245]), which
   provides 48 bits of randomness.  An off-path attacker would have to
   guess those 48 bits to cause the endpoints to perform HMAC-SHA1
   validation of the MESSAGE-INTEGRITY attribute.

   An attacker on the path between the ICE endpoints will see both ice-
   ufrags, and can cause the endpoints to perform HMAC-SHA1 validation
   by sending messages from any IP address.


8.  Acknowledgements

   Thanks to Alfred Heggestad, Lishitao, Sujing Zhou, Martin Thomson,
   Emil Ivov for review and comments.


9.  Change History

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

9.1.  Changes from draft-wing-mmusic-ice-mobility-00 to -01

   o  Updated section 3

9.2.  Changes from draft-wing-mmusic-ice-mobility-01 to -02

   o  Updated Introduction, Notational Conventions, sections 3.1, 3.2.

   o  Updated section 3.5

9.3.  Changes from draft-wing-mmusic-ice-mobility-02 to -03

   o  Moved sections Presence of other interfaces in Valid list, Losing
      an Interface to Appendix.








Wing, et al.            Expires December 19, 2014              [Page 11]

Internet-Draft                    MICE                         June 2014


9.4.  Changes from draft-wing-mmusic-ice-mobility-03 to -04

   o  Added Section 6.

9.5.  Changes from draft-wing-mmusic-ice-mobility-04 to -05

   o  Updated Section 6.

9.6.  Changes from draft-wing-mmusic-ice-mobility-05 to -06

   o  Updated Section 5.

   o  Added Implementation Status section.

9.7.  Changes from draft-wing-mmusic-ice-mobility-06 to -07

   o  Removed Turn Mobility


10.  References

10.1.  Normative References

   [I-D.wing-tram-turn-mobility]
              Wing, D., Patil, P., Reddy, T., and P. Martinsen,
              "Mobility with TURN", draft-wing-tram-turn-mobility-00
              (work in progress), June 2014.

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

   [RFC5245]  Rosenberg, J., "Interactive Connectivity Establishment
              (ICE): A Protocol for Network Address Translator (NAT)
              Traversal for Offer/Answer Protocols", RFC 5245,
              April 2010.

   [RFC5389]  Rosenberg, J., Mahy, R., Matthews, P., and D. Wing,
              "Session Traversal Utilities for NAT (STUN)", RFC 5389,
              October 2008.

   [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.

10.2.  Informative References

   [I-D.rescorla-mmusic-ice-trickle]
              Rescorla, E., Uberti, J., and E. Ivov, "Trickle ICE:



Wing, et al.            Expires December 19, 2014              [Page 12]

Internet-Draft                    MICE                         June 2014


              Incremental Provisioning of Candidates for the Interactive
              Connectivity Establishment (ICE) Protocol",
              draft-rescorla-mmusic-ice-trickle-01 (work in progress),
              October 2012.

   [RFC5077]  Salowey, J., Zhou, H., Eronen, P., and H. Tschofenig,
              "Transport Layer Security (TLS) Session Resumption without
              Server-Side State", RFC 5077, January 2008.

   [RFC5763]  Fischl, J., Tschofenig, H., and E. Rescorla, "Framework
              for Establishing a Secure Real-time Transport Protocol
              (SRTP) Security Context Using Datagram Transport Layer
              Security (DTLS)", RFC 5763, May 2010.

   [RFC5780]  MacDonald, D. and B. Lowekamp, "NAT Behavior Discovery
              Using Session Traversal Utilities for NAT (STUN)",
              RFC 5780, May 2010.

   [RFC6263]  Marjou, X. and A. Sollaud, "Application Mechanism for
              Keeping Alive the NAT Mappings Associated with RTP / RTP
              Control Protocol (RTCP) Flows", RFC 6263, June 2011.

   [RFC6982]  Sheffer, Y. and A. Farrel, "Improving Awareness of Running
              Code: The Implementation Status Section", RFC 6982,
              July 2013.

   [iana-stun]
              IANA, "IANA: STUN Attributes", April 2011,
              <http://www.iana.org/assignments/stun-parameters/stun-pa
              rameters.xml>.


Appendix A.

A.1.  Presence of other interfaces in Valid list

   This technique is optional and only relevant if there is a host
   policy to maintain unused candidates on other interfaces using the
   steps in Appendix A.2.1.  ICE Agent can maintain unused candidates on
   other interfaces if it detects that it is behind Address-Dependent
   Filtering NAT or Firewall.  ICE Agent can detect NAT, Firewall
   behaviour using the procedure explained in [RFC5780].  When the
   interface currently being used for media communication becomes
   unavailable.  If other interfaces are available and local candidates
   from these interfaces are already present in the valid list then ICE
   endpoint will perform the following steps:





Wing, et al.            Expires December 19, 2014              [Page 13]

Internet-Draft                    MICE                         June 2014


   1.  The ICE endpoint based on the locally configured host policy
       preferences, will select a interface whose candidates are already
       present in the valid list.

   2.  The ICE endpoint clears all the pairs in the valid list
       containing the IP addresses from the interface that become
       unavailable.

   3.  The ICE endpoint initiates ICE connectivity checks on the
       selected interface.  The ICE endpoint acts as controlling agent
       and MUST include MOBILITY-EVENT attribute to signal mobility
       event and SHOULD also include the USE-CANDIDATE attribute to
       signal an aggressive nomination (see Section 2.6 of [RFC5245]).
       When all components have a nominated pair in the valid list,
       media can begin to flow using the highest priority nominated
       pair.

   4.  The ICE endpoint will re-establish connection with the SIP proxy.
       Once ICE connectivity checks for all of the media streams are
       completed, the controlling ICE endpoint follows the procedures in
       Section 11.1 of [RFC5245], specifically to send updated offer if
       the candidates in the m and c lines for the media stream (called
       the DEFAULT CANDIDATES) do not match ICE's SELECTED CANDIDATES
       (also see Appendix B.9 of [RFC5245]).

   The ICE endpoint after Mobility using ICE is successful can issue an
   updated offer indicating ICE restart if higher priority interface
   becomes available.

A.1.1.  Receiving ICE Mobility event

   The ICE endpoint that receives ICE Mobility Event will perform the
   steps in Section 3.1.1.

A.2.  Losing an Interface

   When an interface is lost, the SDP MAY be updated, so that the remote
   ICE host does not waste its efforts with connectivity checks to that
   address, as those checks will fail.  Because it can be argued that
   this is merely an optimization, and that the interface loss might be
   temporary (and soon regained), and that ICE has reasonable
   accommodation for candidates where connectivity checks timeout, this
   specification does not strongly encourage updating the SDP to remove
   a lost interface.

   Likewise, this specification recommends that ICE candidate addresses
   in valid list be maintained actively, subject to the host's policy.
   For example, battery operated hosts have a strong incentive to not



Wing, et al.            Expires December 19, 2014              [Page 14]

Internet-Draft                    MICE                         June 2014


   maintain NAT binding for server reflexive candidates learnt through
   STUN Binding Request, as the maintenance requires sending periodic
   STUN Binding Indication.  As another example, a host that is
   receiving media over IPv6 may not want to persist with keeping a
   NATted IPv4 mapping alive (because that consumes a NAT mapping that
   could be more useful to a host actively utilizing the mapping for
   real traffic).

   Note: this differs from Section 8.3 of [RFC5245], which encourages
   abandoning unused candidates.

A.2.1.  Keeping unused candidates in the valid list active

   ICE endpoint subject to host policy can continue performing ICE
   connectivity checks using candidates from other interfaces on the
   host even after ICE is complete.  If valid list contains unused
   candidate pairs from other interfaces and one of these interfaces can
   be selected to send to media in case the existing interface used for
   media is unavailable then ICE endpoint can keep the unused candidate
   pairs from other interface{s} alive by sending keepalives every NN
   seconds.  It is recommended to only keep host/server-reflexive
   candidates active in the valid list and not the relayed candidates.

A.2.1.1.  Sending keep alive requests

   Application Mechanism for Keeping Alive the NAT Mappings Associated
   with RTP / RTP Control Protocol (RTCP) Flows [RFC6263] describes
   various reasons for doing keepalives on inactive streams and how to
   keep NAT mapping alive.  However this specification requires some
   additional functionality associated with the keepalives.

   STUN binding requests MUST be used as the keepalive message instead
   of the STUN Binding indication as specified in [RFC5245].  This is to
   ensure positive peer consent from the remote side that the candidate
   pair is still active and in future mobility can be achieved using the
   steps in Appendix A.1 .  The request must include the MOBILITY-
   SUPPORT attribute.  If the STUN binding response matches a pair in
   the checklist then that candidate pair should be kept in the list.
   If the STUN transaction fails then the candidate pair will be removed
   from valid list.

A.2.1.2.  Receiving keep alive requests

   Upon receiving a STUN binding request containing a MOBILITY-SUPPORT
   attribute even when ICE processing is in the Completed state, the ICE
   endpoint will add this pair to the valid list if not already present
   and generate STUN Binding Response containing the MOBILE-SUPPORT
   attribute.



Wing, et al.            Expires December 19, 2014              [Page 15]

Internet-Draft                    MICE                         June 2014


Authors' Addresses

   Dan Wing
   Cisco Systems, Inc.
   170 West Tasman Drive
   San Jose, California  95134
   USA

   Email: dwing@cisco.com


   Tirumaleswar Reddy
   Cisco Systems, Inc.
   Cessna Business Park, Varthur Hobli
   Sarjapur Marathalli Outer Ring Road
   Bangalore, Karnataka  560103
   India

   Email: tireddy@cisco.com


   Prashanth Patil
   Cisco Systems, Inc.
   Cessna Business Park, Varthur Hobli
   Sarjapur Marthalli Outer Ring Road
   Bangalore, Karnataka  560103
   India

   Email: praspati@cisco.com


   Paal-Erik Martinsen
   Cisco Systems, Inc.
   Philip Pedersens vei 22
   Lysaker, Akershus  1325
   Norway

   Email: palmarti@cisco.com













Wing, et al.            Expires December 19, 2014              [Page 16]


Html markup produced by rfcmarkup 1.107, available from http://tools.ietf.org/tools/rfcmarkup/