v6ops                                                              Z. Li
Internet-Draft                                              China Mobile
Intended status: Informational                                   Q. Zhao
Expires: January 5, 2012                                        X. Huang
                                                                   Y. Ma
                                         Beijing University of Posts and
                                                      Telecommunications
                                                                   X. Xu
                                             Huawei Technologies Co.,Ltd
                                                            July 4, 2011


     Analysis on Load Balancing Requirement in IPv4/IPv6 Transition
              draft-li-v6ops-load-balancing-requirement-00

Abstract

   This document first analyzes the critical issues of bottlenecks in
   existing tunneling and translation technologies, which can be solved
   by proper load balancing mechanisms(e,g., scalability, availability,
   and single point of failure).  Then, several key factors in designing
   a valid load balancing mechanism are described.  Solutions to
   specific load balancing requirements can be drawn out by considering
   these factors.  At last, current efforts about load balancing are
   introduced.

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 January 5, 2012.

Copyright Notice

   Copyright (c) 2011 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.










































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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Requirements Language  . . . . . . . . . . . . . . . . . . . .  4
   3.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   4.  Problems of Bottlenecks  . . . . . . . . . . . . . . . . . . .  5
   5.  Keys To the Load-balancing Solutions . . . . . . . . . . . . .  6
     5.1.  Target Device  . . . . . . . . . . . . . . . . . . . . . .  6
       5.1.1.  Tunnel End-Point . . . . . . . . . . . . . . . . . . .  6
       5.1.2.  Translation Gateway  . . . . . . . . . . . . . . . . .  6
     5.2.  Selection Policy . . . . . . . . . . . . . . . . . . . . .  6
       5.2.1.  Anycast-Based Selection Policy . . . . . . . . . . . .  6
       5.2.2.  Source-Based Selection Policy  . . . . . . . . . . . .  6
       5.2.3.  Destination-Based Selection Policy . . . . . . . . . .  7
       5.2.4.  Round-Robin Selection Policy . . . . . . . . . . . . .  7
       5.2.5.  Subscriber-Based Policy  . . . . . . . . . . . . . . .  7
       5.2.6.  Dynamic Selection Policy . . . . . . . . . . . . . . .  7
     5.3.  Transport Protocol . . . . . . . . . . . . . . . . . . . .  7
       5.3.1.  DNS  . . . . . . . . . . . . . . . . . . . . . . . . .  7
       5.3.2.  DHCP . . . . . . . . . . . . . . . . . . . . . . . . .  7
       5.3.3.  ICMPv6 . . . . . . . . . . . . . . . . . . . . . . . .  7
       5.3.4.  RADIUS . . . . . . . . . . . . . . . . . . . . . . . .  8
     5.4.  Load-balancer Location . . . . . . . . . . . . . . . . . .  8
       5.4.1.  Terminal/Host  . . . . . . . . . . . . . . . . . . . .  8
       5.4.2.  Access Gateway . . . . . . . . . . . . . . . . . . . .  8
       5.4.3.  Network Servers  . . . . . . . . . . . . . . . . . . .  8
   6.  Where Are We Now . . . . . . . . . . . . . . . . . . . . . . .  8
     6.1.  Work Done  . . . . . . . . . . . . . . . . . . . . . . . .  8
       6.1.1.  6RD  . . . . . . . . . . . . . . . . . . . . . . . . .  8
       6.1.2.  BIH  . . . . . . . . . . . . . . . . . . . . . . . . .  9
     6.2.  Work In Progress . . . . . . . . . . . . . . . . . . . . .  9
       6.2.1.  NAT64  . . . . . . . . . . . . . . . . . . . . . . . .  9
     6.3.  Work To Be Done  . . . . . . . . . . . . . . . . . . . . .  9
       6.3.1.  IVI  . . . . . . . . . . . . . . . . . . . . . . . . .  9
       6.3.2.  DS-Lite  . . . . . . . . . . . . . . . . . . . . . . .  9
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . .  9
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 10
   9.  Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 10
   10. Informative References . . . . . . . . . . . . . . . . . . . . 10
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11











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1.  Introduction

   Since the depletion of IPv4 address, IPv6 is being introduced into
   existing networks and IPv4 will be gradually replaced by IPv6.

   The Current Internet is almost fully built on IPv4.  IPv6 is
   fundamentally incompatible with IPv4.  The smooth and incremental
   transition from IPv4 to IPv6 is vital to IPv6's success.  IPv6
   transition technologies are generally classified into three
   catigories: dual stack, tunneling (e.g., 6RD[RFC5969], DS-
   Lite[I-D.ietf-softwire-dual-stack-lite]) and translation (e.g. ,
   NAT64[RFC6146], IVI[RFC6219], BIH[I-D.ietf-behave-v4v6-bih]).

   Dual stack technology can gradually steer traffic from IPv4 network
   to IPv6 network by using the address selection policy that generally
   "IPv6 prior to IPv4", as specified in [RFC3484].

   Both tunneling and translation technologies introduce traffic
   concentration points, the tunnel end-point in tunneling technology
   and the translation gateway in translation technology.  When the
   scope of IPv6 deployment continuously expands and the traffic of IPv6
   business gradually grows, traffic concentration points usually bare
   very heavy work load.  These concentration points will become
   bottlenecks and the sources of the single point of failure.  To
   address such issues,load balancing mechanism should be considered.

   This document firstly analyzes these problems caused by the
   centralized points imposed in the current tunneling and translation
   solutions.  These problems are expected to be solved by proper load
   balancing mechanisms.  Secondly, several key factors in designing
   such load balancing mechanisms are analyzed.  Finally, current
   efforts about load balancing are analyzed and concluded.


2.  Requirements Language

   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.  Terminology

   The terminology used in this document is consistent with
   6rd[RFC5969], NAT64[RFC6146], IVI[RFC6219], DS-
   Lite[I-D.ietf-softwire-dual-stack-lite].  Besides, the following
   terminology is defined.




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   Load-balancer: A system which distributes users' workload across
   multiple devices providing identical services.

   Target Device: The device to which a load-balancer distributes
   workload.  That is the concentration points of the tunneling and
   translation technologies.

   Selection policy: The Policy by which the load-balancer selects
   target device.

   Transport protocol: The protocol the load balancer uses to delivery
   information of selected target device to user.


4.  Problems of Bottlenecks

   During the coexistence of IPv4 and IPv6, more and more IPv6 traffic
   will be carried on IPv4 network or IPv4 Internet in the form of 6in4
   tunnel such as 6RD[RFC5969].  Similarly, more and more IPv4 traffic
   will be guided to IPv6 network or IPv6 Internet in the form of 4in6
   tunnel such as DS-Lite [I-D.ietf-softwire-dual-stack-lite].  Both DS-
   Lite and 6RD concentrate all the tunnel traffic at the tunnel end-
   points in the service provider network.  These tunnel end-points are
   traffic concentration points which are potential bottlenecks.

   During the evolution from IPv4 to IPv6, IPv6 users will communicate
   with IPv4 network or IPv4 Internet in the form of 6->4 translation
   such as NAT64[RFC6146].  Similarly, some IPv4 users will visit IPv6
   network or IPv6 Internet in the form of 4->6 translation such as
   IVI[RFC6219].  Both NAT64 and IVI convert all the translation traffic
   at the translation gateways in service provider network.  These
   translation gateways are traffic concentration points or potential
   bottlenecks.

   There are many problems about bottlenecks.

      1.  The performance of a single concentration point cannot satisfy
      the increasing workload.

      2.  Drive traffic through roundabout path.

      3.  Involve a single point of failure.

   In order to avoid becoming bottleneck, traffic concentration point
   should be distributed to multiple parallel points.  Each parallel
   point performs the same operations.  There must be some load-
   balancing mechanisms to make parallel points collaborate with one
   another stably, smartly and efficiently.



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5.  Keys To the Load-balancing Solutions

   In order to keep transition technology always available when traffic
   growing from small to large scale, some load balancing approaches
   should be applied at IPv4/IPv6 conjunction points.  There are four
   categories requirements for load balancing scheme.  Different
   solutions or mechanisms may be concluded when necessary to meet the
   requirements of each.  The four categories requirements are: Target
   Device, Selection policy, Transport protocol and Load-balancer
   location.

5.1.  Target Device

   As mentioned above, the target device can be tunnel end-point or
   translation gateway in service provider network.

5.1.1.  Tunnel End-Point

   In DS-Lite, such device is AFTR (Address Family Transition Router
   element) which is 4in6 tunnel concentration point and NAPT44 address
   port translator.  In 6RD, such device is BR (Border Relay) which is
   only a 6in4 tunnel concentration point.

5.1.2.  Translation Gateway

   In NAT64, such device is stateful NAT64 device which is IPv6 to IPv4
   protocol address translator.  In IVI, such device is IVI translator
   which is the mapping and translation gateway.

5.2.  Selection Policy

   [I-D.zhang-behave-nat64-load-balancing] has proposed some kinds of
   prefix64 selection policies for NAT64 load balancing.  Those policies
   can also be applied to general load balancing selection policy in
   addition to Subscriber-Based Policy.

5.2.1.  Anycast-Based Selection Policy

   It requires a load-balancer to select target device according to
   whether target device and involved routers support anycast[RFC4291].

5.2.2.  Source-Based Selection Policy

   It requires a load-balancer to select target device according to the
   IPv6 address of user device.






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5.2.3.  Destination-Based Selection Policy

   It requires a load-balancer to choose target device according to
   e.g., the FQDN, the IPv4/IPv6 address, or other identifiers of
   destination servers.

5.2.4.  Round-Robin Selection Policy

   It requires a load-balancer to select target device and destination
   servers circularly according to the arrival request.

5.2.5.  Subscriber-Based Policy

   It requires a load-balancer to choose target device according to the
   subscriber's information, which can be stored in AAA servers, for
   example.

5.2.6.  Dynamic Selection Policy

   It requires a load-balancer to select target device according to the
   real-time status of target device.

5.3.  Transport Protocol

   According to the selection policy, one or more target devices may be
   chosen by load-balancer.  There are different protocols can be used
   to transport the results to user device.

5.3.1.  DNS

   DNS protocol carries response results to DNS queries.  If result is
   IPv6 address with network specific IPv6 prefix, traffic can be lead
   to relevant translation gateway.  If result is IPv6 address of tunnel
   end-point in service provider network, traffic can be lead to
   relevant tunnel concentration point.

5.3.2.  DHCP

   DHCPv4 or DHCPv6 protocol sends network configuration parameters to
   user device.  The parameters may contain network specific IPv6 prefix
   or tunnel end-point address.

5.3.3.  ICMPv6

   ICMPv6 protocol can broadcast RA (Router Advertisement) message and
   options to user device.  The options may contain network specific
   IPv6 prefix or tunnel end-point address.




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5.3.4.  RADIUS

   RADIUS protocol[RFC2865]] can transport subscriber's information to
   network servers such as DHCP or DNS server.  The subscriber's
   information may contain selected network specific IPv6 prefix or
   tunnel end-point address.  The network servers then can distribute
   the prefix or address to user device.

5.4.  Load-balancer Location

   The load-balancer can be implemented in different locations or
   different devices.

5.4.1.  Terminal/Host

   Terminal/Host can be modified to balance the load to target devices.
   The terminal/host should use the selection policy in 5.2 to choose a
   target device and make its traffic go through it.

5.4.2.  Access Gateway

   Access gateway can be modified to balance the load on target devices.
   The access gateway should use the selection policy in 5.2 to choose a
   target device and make user traffic go through it.

5.4.3.  Network Servers

   Network servers include DHCP server, DNS server, RADIUS server and so
   on.  They should use the selection policy in 5.2 to choose a target
   device.  Then, they delivery the results to user device and user
   device will make its traffic go through the target device.


6.  Where Are We Now

   At present, some transition technologies have specified their own
   load balancing solutions, some transition technologies' load
   balancing solutions are in discussion and the others' are still
   waiting to be focused on.

6.1.  Work Done

6.1.1.  6RD

   Target Device is BR, the tunnel end-point.

   Selection Policy is Anycast.




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   Transport Protocol can be DNS, DHCPv4, PPP, or manual configuration
   etc.  DHCPv4 is recommended in [RFC5969].

   Load-balancer Location is in network server.  DHCPv4 server is
   recommended in [RFC5969].

6.1.2.  BIH

   BIH is described in [I-D.ietf-behave-v4v6-bih].Since BIH is NOT
   REOMMENDED to use together with a NAT64, there is no traffic
   concentration point for the BIH per se.  So BIH does not need any
   load-balancing mechanism.

6.2.  Work In Progress

6.2.1.  NAT64

   Target Device is the NAT64 translator.

   [I-D.zhang-behave-nat64-load-balancing] is considering NAT64 load-
   balancing mechanism.  But no solution is recommended at present.

6.3.  Work To Be Done

6.3.1.  IVI

   Target Device is the IVI translator.

   The load-balancing mechanism is not mentioned in the specification of
   IVI[RFC6219].

6.3.2.  DS-Lite

   Target Device is AFTR, the tunnel end-point.

   Although the load-balancing of AFTR can be done by using the FQDN
   option defined in [I-D.ietf-softwire-ds-lite-tunnel-option] and DNS,
   this point is not explicitly described in the specification of DS-
   lite [I-D.ietf-softwire-dual-stack-lite].


7.  Security Considerations

   The potential security problem should be considered in the specific
   load balancing mechanism designed for the specific transition
   technology.





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8.  IANA Considerations

   This document makes no request of IANA.

   Note to RFC Editor: this section may be removed on publication as an
   RFC.


9.  Contributors

   The following individuals have contributed to this document:

   Dacheng Zhang
   Huawei Technologies Co.,Ltd
   KuiKe Building, No.9 Xinxi Rd.,Haidian District
   Beijing 100085
   P.R. China

   Email: zhangdacheng@huawei.com


10.  Informative References

   [I-D.ietf-behave-v4v6-bih]
              Huang, B., Deng, H., and T. Savolainen, "Dual Stack Hosts
              Using "Bump-in-the-Host" (BIH)",
              draft-ietf-behave-v4v6-bih-04 (work in progress),
              April 2011.

   [I-D.ietf-softwire-ds-lite-tunnel-option]
              Hankins, D. and T. Mrugalski, "Dynamic Host Configuration
              Protocol for IPv6 (DHCPv6) Option for Dual- Stack Lite",
              draft-ietf-softwire-ds-lite-tunnel-option-10 (work in
              progress), March 2011.

   [I-D.ietf-softwire-dual-stack-lite]
              Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual-
              Stack Lite Broadband Deployments Following IPv4
              Exhaustion", draft-ietf-softwire-dual-stack-lite-11 (work
              in progress), May 2011.

   [I-D.zhang-behave-nat64-load-balancing]
              Zhang, D., Xu, X., and M. Boucadair, "Considerations on
              NAT64 Load-Balancing",
              draft-zhang-behave-nat64-load-balancing-02 (work in
              progress), April 2011.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate



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              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2865]  Rigney, C., Willens, S., Rubens, A., and W. Simpson,
              "Remote Authentication Dial In User Service (RADIUS)",
              RFC 2865, June 2000.

   [RFC3484]  Draves, R., "Default Address Selection for Internet
              Protocol version 6 (IPv6)", RFC 3484, February 2003.

   [RFC4291]  Hinden, R. and S. Deering, "IP Version 6 Addressing
              Architecture", RFC 4291, February 2006.

   [RFC5969]  Townsley, W. and O. Troan, "IPv6 Rapid Deployment on IPv4
              Infrastructures (6rd) -- Protocol Specification",
              RFC 5969, August 2010.

   [RFC6146]  Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful
              NAT64: Network Address and Protocol Translation from IPv6
              Clients to IPv4 Servers", RFC 6146, April 2011.

   [RFC6219]  Li, X., Bao, C., Chen, M., Zhang, H., and J. Wu, "The
              China Education and Research Network (CERNET) IVI
              Translation Design and Deployment for the IPv4/IPv6
              Coexistence and Transition", RFC 6219, May 2011.


Authors' Addresses

   Zhenqiang Li
   China Mobile
   Unit2, Dacheng Plaza, No. 28 Xuanwumenxi Ave, Xicheng District
   Beijing  100053
   P.R. China

   Email: lizhenqiang@chinamobile.com


   Qin Zhao
   Beijing University of Posts and Telecommunications
   Information Network Center, No. 10 Xitucheng Road, Haidian District
   Beijing  100876
   P.R. China

   Email: zhaoqin@bupt.edu.cn







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   Xiaohong Huang
   Beijing University of Posts and Telecommunications
   Information Network Center, No. 10 Xitucheng Road, Haidian District
   Beijing  100876
   P.R. China

   Email: huangxh@bupt.edu.cn


   Yan Ma
   Beijing University of Posts and Telecommunications
   Information Network Center, No. 10 Xitucheng Road, Haidian District
   Beijing  100876
   P.R. China

   Email: mayan@bupt.edu.cn


   Xiaohu Xu
   Huawei Technologies Co.,Ltd
   KuiKe Building, No.9 Xinxi Rd., Haidian District
   Beijing  100085
   P.R. China

   Email: xuxiaohu@huawei.com


























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