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Versions: (draft-gundavelli-netext-pmipv6-sipto-option) 00 01 02 03 04 05 06 07 08 09 10 11 12 RFC 6909

NETEXT WG                                             S. Gundavelli, Ed.
Internet-Draft                                                     Cisco
Intended status: Standards Track                                 X. Zhou
Expires: March 16, 2013                                  ZTE Corporation
                                                             J. Korhonen
                                                  Nokia Siemens Networks
                                                                G. Feige
                                                               R. Koodli
                                                                   Cisco
                                                      September 12, 2012


       IPv4 Traffic Offload Selector Option for Proxy Mobile IPv6
              draft-ietf-netext-pmipv6-sipto-option-06.txt

Abstract

   This specification defines a mechanism and a related mobility option
   for carrying IPv4 Offload traffic selectors between a mobile access
   gateway and a local mobility anchor in a Proxy Mobile IPv6 domain.
   Based on the received offload flow selectors from the local mobility
   anchor, a mobile access gateway can enable offload traffic rule on
   the selected IPv4 flows.

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 16, 2013.

Copyright Notice

   Copyright (c) 2012 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 . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Conventions and Terminology  . . . . . . . . . . . . . . . . .  4
     2.1.  Conventions  . . . . . . . . . . . . . . . . . . . . . . .  4
     2.2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Solution Overview  . . . . . . . . . . . . . . . . . . . . . .  5
     3.1.  LMA Considerations . . . . . . . . . . . . . . . . . . . .  7
     3.2.  MAG Considerations . . . . . . . . . . . . . . . . . . . .  8
   4.  IP Traffic Offload Selector Option . . . . . . . . . . . . . .  9
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 10
   6.  Protocol Configuration Variables . . . . . . . . . . . . . . . 10
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 11
   8.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 12
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 12
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12
























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1.  Introduction

   Mobile Operators are expanding their network coverage by integrating
   various access technology domains (Ex: Wireless LAN, LTE) into a
   common IP mobile core.  For providing IP mobility support to a mobile
   node irrespective of the access network to which it is attached.  For
   example, the 3GPP S2a Proxy Mobile IPv6 [TS23402] reference point,
   specified by the 3GPP system architecture, is providing the needed
   protocol inter-working.  When this protocol interface based on Proxy
   Mobile IPv6 [RFC5213] is used, the mobile node is topologically
   anchored at the local mobility anchor [RFC5213] in the home network.
   The mobile node's IPv4 traffic is always tunneled back from the
   mobile access gateway [RFC5213] in the access network to the local
   mobility anchor in the home network.  This may not be the case with
   IPv6 traffic, as the mobile node can be assigned an IPv6 prefix from
   the access network in addition to the IPv6 prefix from the home
   network and thereby allowing the mobile node to use an IPv6 address
   from the access network for traffic that needs to be offloaded in the
   access network.

   However, with the exponential growth in the mobile data traffic,
   mobile operators are exploring new ways to offload some of the IP
   traffic flows at the nearest access edge where ever there is an
   internet peering point, as supposed to carrying it all the way to the
   mobility anchor in the home network.  Not all IP traffic need to be
   routed back to the home network, some of the non-essential traffic
   which does not require IP mobility support can be offloaded at the
   mobile access gateway in the access network.  This approach allows
   efficient usage of the mobile packet core which helps in lowering
   transport costs.  The local mobility anchor in the home network can
   potentially deliver the IP flow selectors to the mobile access
   gateway in the access network, for identifying the IP flows that need
   to be offloaded.  Example of such non-essential traffic is entirely a
   policy decision.  A given operator may choose to offload all traffic
   except that requires QoS services (Ex: Voice over IP traffic), or may
   choose to offload all HTTP traffic.  From the point of view of this
   specification, its only about traffic matching a given flow selector
   and classification for offload.  This approach has one limitation
   with respect to identifying encrypted traffic.  IPsec encrypted
   traffic with no visibility into the application payload cannot be
   selected for offload.

   This document defines a new mobility option, IP Traffic Offload
   Selector option for Proxy Mobile IPv6 (PMIPv6).  This option can be
   used by the local mobility anchor to notify the mobile access gateway
   with the flow selectors that can used for selecting the flows for
   offloading them at the access edge.  Since, the mobile node's IP
   address topologically belongs to the home network, the offloaded IP



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   traffic flows need to be NAT [RFC2663] translated.  These offloaded
   flows will not have mobility support as the NAT becomes the anchor
   point for those flows.  Given this NAT translation requirement for
   the offloaded traffic, this approach will be limited to mobile node's
   IPv4 flows.  There are better ways to solve this problem for IPv6 and
   with the goal not to create NAT66 requirement, this specification
   does not support traffic offload support for IPv6 flows.  This
   document also does not define any new semantics for flow selectors.
   The flow identification and the related semantics are all leveraged
   from [RFC6088].


2.  Conventions and Terminology

2.1.  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 RFC 2119 [RFC2119].

2.2.  Terminology

   All the mobility related terms used in this document are to be
   interpreted as defined in the base Proxy Mobile IPv6 specifications
   [RFC5213] and [RFC5844].  Additionally, this document uses the
   following abbreviations:

   IP Flow

      IP Flow represents a set of IP packets that match a traffic
      selector.  The selector is typically based on the source IP
      address, destination IP address, source port, destination port and
      other fields in upper layer headers.

   IP Traffic Offload

      The approach of selecting specific IP flows and routing them
      through the access network, instead of tunneling them to the home
      network.  Offload can also be between two access networks
      (Example: moving some of the traffic from LTE access to WLAN
      access).

   NAT (Network Address Translation)








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      Network Address Translation [RFC2663] is a method by which IP
      addresses are mapped from one address realm to another, providing
      transparent routing to end hosts.


3.  Solution Overview

   The following illustrates the scenario where the mobile access
   gateway in an access network has the ability to offload some of the
   IPv4 traffic flows, based on the traffic selectors it received from
   the local mobility anchor in the home network.  For example, all the
   HTTP flows may be offloaded at the mobile access gateway and all the
   other flows for that mobility session are tunneled back to the local
   mobility anchor.  The offloaded flows have to be NAT translated and
   this specification does not impose any restrictions on the location
   of the NAT function.  It is possible, the NAT function is collocated
   with the mobile access gateway, or its located some where in the edge
   of the access network.  When the NAT is not collocated on the mobile
   access gateway, the NAT function should have the ability to identify
   the offloaded IP traffic for NAT policy enforcement.  This could be
   achieved by configuring a specific VLAN between the mobile access
   gateway and the NAT device and ensuring all the traffic on that VLAN
   is NAT translated.  This can also be achieved through other means and
   the details are outside the scope of this document.

   The selectors that are delivered to the mobile access gateway can be
   used to classify the traffic, so it can be offloaded to the access
   network.  The parameters in the IP traffic selectors can be used to
   match against the header fields in the data packets.  These
   parameters include Source IP address, Destination IP address, TCP/UDP
   Port numbers, and other fields.




















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            _----_
          _(      )_
         ( Internet )
          (_      _)
            '----'
              |
              :
   (IPv4 Traffic Offload Point)
              :
              |
   .........................................................
              |                              |
   +--------+ |                   +---------------------+
   |  Local |-|                   | Services requiring  |
   |Services| |                   | mobility, or service|
   +--------+ |                   | treatment           |
              |                   +---------------------+
            +---+                            |
            |NAT|                            |
            +---+                            |
              |            _----_            |
           +-----+       _(      )_       +-----+
   [MN]----| MAG |======(    IP    )======| LMA |-- Internet
           +-----+       (_      _)       +-----+
                           '----'
                              .
                              .
       [Access Network]       .        [Home Network]
   ..........................................................

              Figure 1: IP Traffic Offload Support at the MAG

   Figure 2 explains the operational sequence of the Proxy Mobile IPv6
   protocol signaling message exchange between the mobile access gateway
   and the local mobility anchor for negotiating the IP Traffic Offload
   selectors.  The details related to DHCP transactions, or Router
   Advertisements on the access link are not shown here as that is not
   the key focus of this specification.













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   MN    MAG(NAT)   LMA
   |------>|        |    1. Mobile Node Attach
   |       |------->|    2. Proxy Binding Update
   |       |<-------|    3. Proxy Binding Acknowledgement (IPTS Option)
   |       |========|    4. Tunnel/Route Setup
   |       +        |    5. Installing the traffic offload rules
   |------>|        |    6. IPv4 packet from mobile node
   |       +        |    7. Forwarding rule - Tunnel home/offload
   |       |        |


            Figure 2: Exchange of IP Traffic Offload Selectors

3.1.  LMA Considerations

   The following considerations apply to the local mobility anchor.

   o  If the received Proxy Binding Update includes the IP Traffic
      Offload Selector option (Section 4), but if the configuration
      variable, EnableIPTrafficOffloadSupport (Section 6) on the local
      mobility anchor is set to a value of (0), then the local mobility
      anchor MUST ignore the IP Traffic Offload Selector option and
      process the rest of the packet as per [RFC5213].  This would have
      no effect on the operation of the rest of the protocol.

   o  If the received Proxy Binding Update includes the IP Traffic
      Offload Selector option (Section 4), and if the configuration
      variable, EnableIPTrafficOffloadSupport (Section 6) on the local
      mobility anchor is set to a value of (1), then the local mobility
      anchor can acquire the offload policy from a network function (Ex:
      AAA or PCRF) and can construct the traffic selectors based on the
      offload policy and deliver those selectors in the Proxy Binding
      Acknowledgement message using the IP Traffic Offload Selector
      option.  The specific details on how the offload policy for a
      mobile node is provisioned on the local mobility anchor is out of
      the scope for this document.  However, if the received Proxy
      Binding Update included a proposed Offload traffic selectors, the
      local mobility anchor MAY choose to honor that request and include
      the proposed selectors in the reply.

   o  If the received Proxy Binding Update does not include the IP
      Traffic Offload Selector option (Section 4), and if the
      configuration variable, EnableIPTrafficOffloadSupport (Section 6)
      on the local mobility anchor is set to a value of (1), then the
      local mobility anchor SHOULD NOT include the IP Traffic Offload
      Selector option in the Proxy Binding Acknowledgement.





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3.2.  MAG Considerations

   o  If the configuration variable, EnableIPTrafficOffloadSupport on
      the mobile access gateway is set to a value of (0), then the
      mobile access gateway MUST NOT include the IP Traffic Offload
      Selector option (Section 4) in the Proxy Binding Update message
      that it sends to the local mobility anchor.  Otherwise, the option
      MUST be included in the Proxy Binding Update message.  When this
      option is included, it is an indication to the local mobility
      anchor that the mobile access gateway is capable of supporting IP
      Traffic Offload support.  The TS format field of the IP Traffic
      Offload Selector option MUST be set to a value of (255),
      indicating that the mobile access gateway is not proposing any
      specific offload policy for that mobility session, but a request
      to the local mobility anchor to provide the IP traffic offload
      flow selectors for that mobility session.

   o  The mobile access gateway MAY choose to include its proposed IP
      traffic offload flow selectors in the IP Traffic Offload Selector
      option (Section 4).  Including this offload traffic selectors
      serves as a proposal to the local mobility anchor, which the local
      mobility anchor can override with its own offload policy, or agree
      to the proposed policy.  When including the offload traffic
      selectors, the TS format field of the IP Traffic Offload Selector
      option MUST be set to the respective flow specification type.

   o  If there is no IP Traffic Offload Selector option in the
      corresponding Proxy Binding Acknowledgement message, that the
      mobile access gateway receives in response to a Proxy Binding
      Update, it serves as an indication that the local mobility anchor
      does not support IP Traffic Offload support for that mobility
      session, and it implies the local mobility anchor cannot deliver
      IP flow selectors for that mobility session.  The mobile access
      gateway upon accepting the Proxy Binding Acknowledgement message
      MUST NOT enable any offload policy for that mobility session.  All
      the mobile node's IP flows MUST be tunneled back to the local
      mobility anchor.

   o  If there is an IP Traffic Offload Selector option in the
      corresponding Proxy Binding Acknowledgement message, it is an
      indication that the local mobility anchor has provided the IP
      traffic Offload selectors for that mobility session [RFC5213] and
      the identified IP flows have to be offloaded.  Considerations
      related to (M) flag MUST be applied.  The mobile access gateway
      SHOULD enable traffic offload for those identified flows.  The
      delivered offload selectors rules MUST be applied only for the
      flows associated to that mobility session.




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   o  If the mobile access gateway is not capable, or enabled to support
      IP Traffic Offload support, but if the received Proxy Binding
      Acknowledgement message has the IP Traffic Offload Selector
      option, the mobile access gateway SHOULD ignore the option and
      process the rest of the packet as per [RFC5213].


4.  IP Traffic Offload Selector Option

   A new mobility option, IP Traffic Offload Selector option, is defined
   for using it in Proxy Binding Update (PBU) and Proxy Binding
   Acknowledgement (PBA) messages exchanged between a mobile access
   gateway and a local mobility anchor.  This option is used for
   carrying the flow selectors for enabling IP traffic offload function
   at the mobile access gateway.

   The alignment requirement for this option is 4n.


   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
                                   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                   |      Type     |   Length      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |M|             Reserved                        |    TS Format  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Traffic Selector ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


               Figure 3: IP Traffic Offload Selector Option

   Type
      <IANA-1>

   Length
      8-bit unsigned integer indicating the length in octets of the
      option, excluding the type and length fields.

   Reserved
      This field is unused for now.  The value MUST be initialized to 0
      by the sender and MUST be ignored by the receiver.

   IP Traffic Offload Mode Flag
      This field indicates the offload mode.  If the (M) flag value is
      set to a value of (1), it is an indication that all the IP flows
      associated to that mobility session except the identified IP
      flow(s) in this mobility option SHOULD be offloaded at the mobile



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      access gateway.  If the (M) flag value is set to a value of (0),
      it is an indication that the identified IP flow(s) in this
      mobility option SHOULD be offloaded at the mobile access gateway
      and all other IP flows associated with that mobility session need
      to be tunneled to the local mobility anchor.

   TS Format
      An 8-bit unsigned integer indicating the Traffic Selector Format.
      The values for this field are maintained by the "Traffic Selector
      Format" namespace defined in [RFC6089].  The value of "255" is
      reserved and is used when there are no selectors to carry.  In
      this case, the option is used only as a capability indicator.
      When the value of TS Format field is set to (1), the format that
      follows is the IPv4 Binary Traffic Selector specified in section
      3.1 of [RFC6088].

   TS Selector
      A variable-length opaque field for including the traffic
      specification identified by the TS format field.


5.  IANA Considerations

   This document requires the following two IANA actions.

   o  Action-1: This specification defines a new Mobility Header option,
      IP Traffic Offload Selector option.  This option is described in
      Section 4.  The Type value for this option needs to be assigned
      from the same numbering space as allocated for the other mobility
      options [RFC6275].

   o  Action-2: The Sub-type field of the IP Traffic Offload Selector
      option described in Section 4 uses the number space from "Traffic
      Selector Format" namespace specified in [RFC6089].  This
      specification reserves the value (255) (NULL Selector) from that
      number space.


6.  Protocol Configuration Variables

   This specification defines the following configuration variable that
   control the use of IP Traffic Offload support for a mobility session.
   The mobility entities, local mobility anchor and the mobile access
   gateway MUST allow these variables to be configured by the system
   management.  The configured values for these protocol variables MUST
   survive server reboots and service restarts.





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   EnableIPTrafficOffloadSupport

         This flag indicates whether or not IP Traffic Offload support
         needs to be enabled.  This configuration variable is available
         at both in the mobile access gateway and at the local mobility
         anchor.  The default value for this flag is set to (0),
         indicating that the support for IP Traffic offload support is
         disabled.

         When this flag on the mobile access gateway is set to a value
         of (1), the mobile access gateway MUST enable the IP Traffic
         offload support for a mobility session, specifically it MUST
         include the IP Traffic Offload Selector option in the Proxy
         Binding Update messages and offload the negotiated IP flows to
         the access network.  If the value of the flag is set to a value
         of (0), mobile access gateway MUST NOT enable IP Traffic
         Offload support and it MUST NOT include this option in the
         Proxy Binding Update.

         Similarly, when this flag on the local mobility anchor is set
         to a value of (1), the local mobility anchor SHOULD enable
         support for IP Traffic offload support.  When the local
         mobility anchor chooses to enable IP Traffic offload support
         and if there is offload flow policy specified for a mobility
         node, it SHOULD deliver the offload selectors to the mobile
         access gateway by including the IP Traffic Offload Selector
         option in the Proxy Binding Acknowledgement message.


7.  Security Considerations

   The IP Traffic Offload Selector option defined in this specification
   is for use in Proxy Binding Update and Proxy Binding Acknowledgement
   messages.  This option is carried like any other mobility header
   option as specified in [RFC5213] and does not require any special
   security considerations.  Carrying IP traffic offload selectors does
   not introduce any new security vulnerabilities.

   When IPv4 traffic offload support is enabled for a mobile node, the
   mobile access gateway selectively offloads some of the mobile node's
   traffic flows to the access network.  Typically, these offloaded
   flows get NAT translated and essentially that introduces certain
   vulnerabilities which are common to any NAT deployment.  These
   vulnerabilities and the related considerations have been well
   documented in the NAT specification [RFC2663].  There are no
   additional considerations above and beyond what is already documented
   by the NAT specifications and which are unique to the approach
   specified in this document.



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8.  Acknowledgements

   The authors would like to thank Ahmad Muhanna, Basavaraj Patil,
   Carlos Bernardos, Eric Voit, Frank Brockners, Hidetoshi Yokota, Marco
   Liebsch, Mark Grayson, Pierrick Seite, Ryuji Wakikawa, and Steve Wood
   for all the discussions related to the topic of IP traffic offload.


9.  References

9.1.  Normative References

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

   [RFC5213]  Gundavelli, S., Leung, K., Devarapalli, V., Chowdhury, K.,
              and B. Patil, "Proxy Mobile IPv6", RFC 5213, August 2008.

   [RFC5844]  Wakikawa, R. and S. Gundavelli, "IPv4 Support for Proxy
              Mobile IPv6", RFC 5844, May 2010.

   [RFC6088]  Tsirtsis, G., Giarreta, G., Soliman, H., and N. Montavont,
              "Traffic Selectors for Flow Bindings", RFC 6088,
              January 2011.

   [RFC6089]  Tsirtsis, G., Soliman, H., Montavont, N., Giaretta, G.,
              and K. Kuladinithi, "Flow Bindings in Mobile IPv6 and
              Network Mobility (NEMO) Basic Support", RFC 6089,
              January 2011.

9.2.  Informative References

   [RFC2663]  Srisuresh, P. and M. Holdrege, "IP Network Address
              Translator (NAT) Terminology and Considerations",
              RFC 2663, August 1999.

   [RFC6275]  Perkins, C., Johnson, D., and J. Arkko, "Mobility Support
              in IPv6", RFC 6275, July 2011.

   [TS23402]  3GPP, "Architecture enhancements for non-3GPP accesses",
              2010.










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Authors' Addresses

   Sri Gundavelli (editor)
   Cisco
   170 West Tasman Drive
   San Jose, CA  95134
   USA

   Email: sgundave@cisco.com


   Xingyue Zhou
   ZTE Corporation
   No.68 Zijinghua Rd
   Nanjing
   China

   Email: zhou.xingyue@zte.com.cn


   Jouni Korhonen
   Nokia Siemens Networks
   Linnoitustie 6
   Espoo  FIN-02600
   Finland

   Email: jouni.nospam@gmail.com


   Gaetan
   Cisco
   France

   Email: gfeige@cisco.com


   Rajeev Koodli
   Cisco
   3650 Cisco Way
   San Jose, CA  95134
   USA

   Email: rkoodli@cisco.com








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