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PCP Working Group                                                G. Chen
Internet-Draft                                              China Mobile
Intended status: Standards Track                                T. Reddy
Expires: March 22, 2014                                         P. Patil
                                                                   Cisco
                                                            M. Boucadair
                                                          France Telecom
                                                      September 18, 2013


           PCP Server Discovery in Mobile Networks with SIPTO
                 draft-chen-pcp-sipto-serv-discovery-00

Abstract

   This document proposes an extension to DHCPv4 Relay information so
   that a PCP client learns the relevant PCP server deployed in the
   context of traffic offload.

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-
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   Internet-Drafts are draft documents valid for a maximum of six months
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   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 22, 2014.

Copyright Notice

   Copyright (c) 2013 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
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   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
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   include Simplified BSD License text as described in Section 4.e of



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   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.  DHCPv4 Relay Agent  . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  Format  . . . . . . . . . . . . . . . . . . . . . . . . .   3
     3.2.  Relay Agent behavior  . . . . . . . . . . . . . . . . . .   4
     3.3.  DHCPv4 Server behavior  . . . . . . . . . . . . . . . . .   4
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   5
   7.  Change History  . . . . . . . . . . . . . . . . . . . . . . .   5
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   Given the exponential growth in the mobile data traffic, Mobile
   Operators are investigating solutions to offload some of the IP
   traffic flows at the nearest access edge that has an Internet
   interconnection point.  This approach results in efficient usage of
   the mobile packet core and helps lower the transport cost.  Since
   Release 10, 3GPP starts supporting of Selected IP Traffic Offload
   (SIPTO) function defined in [TS23.060], [TS23.401].

   The SIPTO function described in [TS23.060] allows an operator to
   offload certain types of traffic at a network node close to the UE's
   point of attachment to the access network.  Traffic Offload
   Function(TOF) has been defined to make such decisions and enforces
   NAT for those traffic.  The traffic would go through the Mobile
   Packet Core only if the flow identification doesn't match TOF
   filters.  SIPTO architecture is also explained in
   [I-D.chen-pcp-mobile-deployment].

   [I-D.ietf-pcp-dhcp] specifies DHCP (IPv4 and IPv6) options to
   communicate Port Control Protocol (PCP) Server addresses to hosts.
   However, PCP Client on the mobile node will not know whether a flow
   will traverse the Mobile Packet Core or will get offloaded at the TOF
   and hence will not know which PCP server to send its requests to.
   Even if the mobile node learns its PCP server using DHCP, it will
   only learn about the PCP server in the Mobile Packet Core since the
   source of information is the DHCP server in the Mobile Packet Core.
   The mobile node may never learn the presence of the PCP server at



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   TOF.  This requires TOF to act as a PCP Proxy for the PCP server in
   the Mobile Packet Core and as a PCP server for the offloaded traffic
   at the TOF.  However, this alone does not solve this problem since
   the mobile node needs to be informed of the PCP proxy on the TOF.

   This document proposes an extension to DHCPv4 Relay Information
   Option to achieve this objective.  This will also ensure that the PCP
   client will only learn the PCP server address of the TOF.

   Note:

   o  The SIPTO problem can be addressed for IPv6 either by using NPTv6
      [RFC6296] or associating the mobile device with multiple IPv6
      prefixes (one prefix to offload the traffic and other one provided
      by the Mobile Packet Core for IP Mobility, access to Application
      Servers in Mobile Packet Core etc).  New DHCPv6 Relay Agent PCP
      Server option will only be required if NPTv6 is used to offload
      the traffic.  However if multiple IPv6 prefixes are assigned to
      the mobile device then it can use the mechanism explained in
      [I-D.ietf-pcp-server-selection] to contact multiple PCP servers.

   o  The proposed extension to DHCPv4 Relay Information Option in this
      document is also useful to solve problems in other deployments
      like PMIPv6 [RFC5213] where mobile access gateway can selectively
      offload some of the IPv4 traffic flows in the access network
      instead of tunneling back to the local mobility anchor in the home
      network [RFC6909].

2.  Terminology

   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.  DHCPv4 Relay Agent

   When DHCPv4 Relay Agent [RFC3046] is co-located with the TOF, the
   proposal is for the relay agent to influence the DHCPv4 Server to opt
   for the PCP server address proposed by the Relay Agent over the one
   configured on the DHCPv4 Server.  The DHCPv4 Relay Agent will insert
   a new suboption under relay agent information option indicating the
   IP address of the appropriate PCP server/proxy.  For this to happen,
   the UE MUST ensure that it includes OPTION_PCP_SERVER in the
   Parameter Request List Option in the DHCPv4 Discover/Request message.

3.1.  Format





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   To realize the mechanism described above, the document proposes a new
   PCP Server suboption for the DHCPv4 relay agent information option
   that carries the IP address of PCP Server.  If a PCP server is
   associated with more than one IP address, all those IP addresses can
   be listed as part of this option.  If there is more than one PCP
   server, there will be multiple instances of this option each
   corresponding to a PCP server.

    Code  Length   PCP IP address
   +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
   | TBA |  n  |  a1 |  a2 |  a3 |  a4 |  a1 |  a2 |  a3 |  a4 |  ...
   +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+


   Code:  TBA

   Length:   Includes the length of the "PCP Server IP address" field in
      octets; The maximum length is 255 octets.  The length should be
      multiple of 4.

   PCP Server IP address:  The IP address of the PCP Server to be used
      by the PCP Client when issuing PCP messages.

3.2.  Relay Agent behavior

   A DHCPv4 relay agent MAY be configured to include a PCP Server
   suboption in relayed DHCPv4 messages.  If the source IP address in
   the DHCPv4 request matches the TOF filter configuration then the PCP
   Server IP address SHOULD be inserted into the PCP Server suboption.
   The PCP Server IP address is determined through mechanisms outside
   the scope of this document.

3.3.  DHCPv4 Server behavior

   The proposed suboption provides additional information to the DHCP
   server.  Upon receiving a DHCPv4 Discover/Request containing the
   suboption, the DHCPv4 server, if configured to support this
   suboption, MUST populate the DHCPv4 Offer/Ack with the suggested PCP
   server IP address overriding any other PCP server IP address
   configuration that it may already have.  There is no special
   additional processing for this suboption.

4.  Security Considerations

   The security considerations in [RFC6887] , [I-D.ietf-pcp-proxy] and
   section 5 of [RFC3046] also apply to this use.





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5.  IANA Considerations

   Authors of this document request IANA to assign a suboption number
   for the PCP Server Suboption from the DHCP Relay Agent Information
   Option [RFC3046] suboption number space.

6.  Acknowledgements

   TODO

7.  Change History

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

8.  References

8.1.  Normative References

   [I-D.ietf-pcp-dhcp]
              Boucadair, M., Penno, R., and D. Wing, "DHCP Options for
              the Port Control Protocol (PCP)", draft-ietf-pcp-dhcp-08
              (work in progress), August 2013.

   [I-D.ietf-pcp-proxy]
              Boucadair, M., Penno, R., and D. Wing, "Port Control
              Protocol (PCP) Proxy Function", draft-ietf-pcp-proxy-04
              (work in progress), July 2013.

   [I-D.ietf-pcp-server-selection]
              Boucadair, M., Penno, R., Wing, D., Patil, P., and T.
              Reddy, "PCP Server Selection", draft-ietf-pcp-server-
              selection-01 (work in progress), May 2013.

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

   [RFC3046]  Patrick, M., "DHCP Relay Agent Information Option", RFC
              3046, January 2001.

   [RFC6887]  Wing, D., Cheshire, S., Boucadair, M., Penno, R., and P.
              Selkirk, "Port Control Protocol (PCP)", RFC 6887, April
              2013.

8.2.  Informative References

   [I-D.chen-pcp-mobile-deployment]




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              Chen, G., Cao, Z., Boucadair, M., Ales, V., and L.
              Thiebaut, "Analysis of Port Control Protocol in Mobile
              Network", draft-chen-pcp-mobile-deployment-04 (work in
              progress), July 2013.

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

   [RFC6296]  Wasserman, M. and F. Baker, "IPv6-to-IPv6 Network Prefix
              Translation", RFC 6296, June 2011.

   [RFC6909]  Gundavelli, S., Zhou, X., Korhonen, J., Feige, G., and R.
              Koodli, "IPv4 Traffic Offload Selector Option for Proxy
              Mobile IPv6", RFC 6909, April 2013.

   [TS23.060]
              3GPP, ., ""General Packet Radio Service (GPRS); Service
              description; Stage 2", June 2012.", September 2012.

   [TS23.401]
              3GPP, ., "General Packet Radio Service (GPRS) enhancements
              for Evolved Universal Terrestrial Radio Access Network (E-
              UTRAN) access (Release 11), 3GPP TS 23.401, V11.2.0 (2012-
              06).", September 2012.

Authors' Addresses

   Gang Chen
   China Mobile
   No.32 Xuanwumen West Street
   Xicheng District
   Beijing  100053
   China

   Email: phdgang@gmail.com


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

   Email: tireddy@cisco.com






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   Prashanth Patil
   Cisco Systems, Inc.
   Bangalore
   India

   Email: praspati@cisco.com


   Mohamed Boucadair
   France Telecom
   Rennes  35000
   France

   Email: mohamed.boucadair@orange.com





































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