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Network Working Group                                             L. Xue
Internet-Draft                                               B. Sarikaya
Intended status: Informational                                    Huawei
Expires: October 23, 2014                                 April 21, 2014


   Host Identification Problem in Service Function Chaining Use Cases
         draft-xue-sfc-address-sharing-in-sfc-use-cases-00.txt

Abstract

   The purpose of this document is to present host identification
   problem due to the address and prefix sharing in service function
   chaining.  So far we have identified this problem in the two use
   cases of the parental control service and offloading service but it
   is likely that more use cases can be identified.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on October 23, 2014.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions and Terminology . . . . . . . . . . . . . . . . .   2
   3.  Service Function Execution  . . . . . . . . . . . . . . . . .   3
   4.  Issue Description . . . . . . . . . . . . . . . . . . . . . .   4
     4.1.  Parental Control Use Case . . . . . . . . . . . . . . . .   4
     4.2.  Traffic Offload Use Case  . . . . . . . . . . . . . . . .   5
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   5
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   The use cases described in this document belong to service function
   chaining (SFC) area [I-D.liu-sfc-use-cases],
   [I-D.haeffner-sfc-use-case-mobility].  Service functions like
   Parental Control, Traffic Offloader, Web Proxy, Load Balancer, etc.
   can be executed in a chained fashion.  The order of execution of each
   function is controlled by an abstract entity called Service Chaining
   Enforcement Points (SCEP) [I-D.beliveau-sfc-architecture].  Each
   service function is directly connected to an SCEP.

   Traffic policy control, such as Parental Control Function and Traffic
   Offloader are commonly used by operators to enable flexible service
   to the customers.  The architecture we assume is shown in Figure 1.
   It is a typical home network architecture.

   Address sharing/host identification issue comes up if the residential
   gateway (RG) is a NAT box in IPv4 or a single prefix is assigned to
   the RG in DHCPv6-Prefix Delegation in IPv6
   [I-D.boucadair-intarea-host-identifier-scenarios].  Multiple hosts
   are sharing the same public IPv4 address or single IPv6 prefix.

   Some earlier solution approaches to the host identification problem
   are analysed in [RFC6967].  It is not clear if those approaches can
   also be used in the service function chaining use cases.

2.  Conventions and 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 RFC 2119 [RFC2119].




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3.  Service Function Execution

   We assume a service function chaining architecture similar to
   [I-D.beliveau-sfc-architecture].  In its simplified form, possibly
   suitable in home networks, the service chain enforcement point is
   also the ingress router or edge router, e.g. Broadband Network
   Gateway.  In this case parental control function and all other
   functions are directly connected to SCEP.  There is an egress router
   that routes traffic to the edge router, see Figure 1.

   Parental control service function is needed to filter the traffic
   from the Internet for certain content.  Home users connect to the
   Internet after getting their address from RG.  In case of NAT at the
   RG, all outgoing traffic carries the same address for all users, i.e.
   RG address for its WAN interface.  In case RG is assigned a single
   prefix, all outgoing IPv6 packets contain the same prefix.

   Encrypted web traffic (https) represents a very significant part of
   Web traffic and is likely to become the main or even the only method
   to carry Web data over the Internet.  Service functions MUST be able
   to decrypt such encrypted traffic, e.g. using Secure Socket Layer
   (SSL).  In case of address sharing/host identification, being able to
   decrypt encrypted data becomes a requirement in order to be able to
   access the URL and user information to filter.

   With data services rapidly increasing, the traditional cellular
   network becomes the bottleneck in providing mobile services mainly
   because of the increasing bandwidth demand.  Operators are trying to
   offload the data traffic from the mobile subscribers to the broadband
   network.  Traffic offloader service function is needed in the
   broadband access network for this purpose.

   One common broadband access network for offload is home network.
   Traffic offloader service function decides on each flow/service
   coming from the hosts at home if they should be routed to the
   broadband network, i.e. offloaded or they should be sent to the
   packet data network gateway fo the mobile network.














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                    +----------------+  +-----------------+
   Service Function |Parental Control|  |Traffic Offloader|
             Chain  +----------------+  +-----------------+
                         \              /
                     ---------------------------------------------
     --+-   +----+         \         /       --+-
   /      \ |Rout|    +-------------+      /      \      +-------------+
  |  Home  || ed |----| Edge Router |-----|Network | --- |    Router   |
  | Network|| RG |    +-------------+     |        |     |   (Egress)  |
   \      / +----+                         \      /      +-------------+
     ----                                    ----             |
                                                            --+-
                                                          /      \
                                                         |Internet|
                                                         |        |
                                                          \      /
                                                            ----

                Figure 1: Service Chaining in Home Network

4.  Issue Description

4.1.  Parental Control Use Case

   Parental control service function searches each packet for certain
   content, e.g. certain URL like www.thisbizarresite.com.  Parental
   control function should keep this information (URL and source IP
   address) in its cache so that all subsequent packets can be filtered
   for certain users from the Web server.  Parental control service
   should send the packet back to SCEP to be forwarded to the home
   network.

   Parental control function receives next packet from the recorded URL.
   Now it needs to decide to filter it or not.  Filtering for specific
   host should depend on the source address, i.e. the address of the
   host that is being subject to the parental control in IPv4 or the
   prefix of the host that is being subject to the parental control in
   IPv6.  In case of NAT'ed RG, all incoming packets from one RG contain
   the same address, i.e. WAN interface address of RG.  In case of IPv6,
   all incoming packets contain the same prefix.

   In order to do the parental control on the incoming traffic, parental
   control service function needs to identify each host.  A typical host
   identity is its IP address in broadband network.  In Figure 1, RG
   knows identifiers of each host in the home network.  Edge router
   needs to identify the host so that it can inform the service
   functions and set the proper service chain.




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   Edge router MUST set host identifier state in the service functions
   that need it, e.g. parental control.  Parental control function MUST
   be able to identify incoming traffic to be filtered, e.g. specific
   URL information.  All other traffic is not subject to filtering.
   Parental control function filters all traffic coming from indicated
   URL only for the specific hosts identified by the service control
   enforcement point.

4.2.  Traffic Offload Use Case

   Traffic offloader service function works on each flow/service and
   decides if it should be offloaded to the broadband network or sent
   back to the mobile network.  In this scenario, the broadband network
   MUST obtain the subscriber subscription from the mobile network and
   decide if the traffic coming from this subscriber needs to be
   offloaded or not.  If offloading is needed, This usually means that
   the source address of the subscriber needs to be known on edge
   router.  In case of NAT'ed RG, all the hosts information lost, this
   introduces a major challenge on how to obtain host identification to
   decide to offload the traffic or not.

5.  IANA Considerations

   This document makes no request to IANA.

6.  Security Considerations

   Any security considerations arising from Service Function Chaining
   use cases are TBD.

7.  Acknowledgements

   TBD.

8.  References

8.1.  Normative References

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

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

   [RFC3633]  Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic
              Host Configuration Protocol (DHCP) version 6", RFC 3633,
              December 2003.



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   [TS29.212]
              "3GPP TS29.212, Policy and Charging Control (PCC) over Gx/
              Sd reference point", December 2011.

8.2.  Informative References

   [I-D.beliveau-sfc-architecture]
              Beliveau, A., "Service Function Chaining Architecture",
              draft-beliveau-sfc-architecture-00 (work in progress),
              October 2013.

   [I-D.boucadair-intarea-host-identifier-scenarios]
              Boucadair, M., Binet, D., Durel, S., Chatras, B., Reddy,
              T., Williams, B., Sarikaya, B., and L. Xue, "Host
              Identification: Use Cases", draft-boucadair-intarea-host-
              identifier-scenarios-05 (work in progress), April 2014.

   [I-D.haeffner-sfc-use-case-mobility]
              Haeffner, W., Napper, J., Stiemerling, M., and D. Lopez,
              "Service Function Chaining Use Cases in Mobile Networks",
              draft-haeffner-sfc-use-case-mobility-01 (work in
              progress), February 2014.

   [I-D.liu-sfc-use-cases]
              Will, W., Li, H., Huang, O., Boucadair, M., Leymann, N.,
              Cao, Z., Qiong, Q., and C. Pham, "Service Function
              Chaining (SFC) Use Cases", draft-liu-sfc-use-cases-05
              (work in progress), April 2014.

   [RFC6967]  Boucadair, M., Touch, J., Levis, P., and R. Penno,
              "Analysis of Potential Solutions for Revealing a Host
              Identifier (HOST_ID) in Shared Address Deployments", RFC
              6967, June 2013.

Authors' Addresses

   Li Xue
   Huawei
   NO.156 Beiqing Rd. Z-park, Shi-Chuang-Ke-Ji-Shi-Fan-Yuan,
   Beijing, HaiDian District  100095
   China

   Email: xueli@huawei.com








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   Behcet Sarikaya
   Huawei
   5340 Legacy Dr.
   Plano, TX  75024

   Email: sarikaya@ieee.org













































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