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Network Working Group                                            Z. Chen
Internet-Draft                                             China Telecom
Intended status: Standards Track                                D. Lopez
Expires: December 20, 2012                                 Telefonica I+D
                                                                 T. Tsou
                                               Huawei Technologies (USA)
                                                                 C. Zhou
                                                     Huawei Technologies
                                                            June 19, 2012


             A Reference Framework for DC Migration to IPv6
                      draft-lopez-v6ops-dc-ipv6-02

Abstract

   This document is intended to provide a reference framework for
   datacenter operators planning for a migration of their
   infrastructures to IPv6.  It aims to offer a scheme for evaluating
   different products and architectures, and therefore it is also
   addressed to manufacturers and solution providers, so they can use it
   to gauge their solutions.  We believe this will translate in a
   smoother and faster transition of these infrastuctures into IPv6

   The document focuses on the DC infrastructure itself, its operation,
   and the aspects related to DC interconnection through IPv6.  It does
   not consider the particular mechanisms for making Internet services
   provided by applications hosted in the DC available through IPv6
   beyond the specific aspects related to how their deployment on the DC
   infrastructure.

   Apart from facilitating the migration procedure itself, the
   mechanisms outlined here are intended to make this migration as
   transparent as possible (if not completely transparent) to
   applications and services running on the DC infrastructure, as well
   as to take advantage of IPv6 features to simplify DC operations,
   internally and across the Internet.

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/.




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   Internet-Drafts are draft documents valid for a maximum of six months
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   This Internet-Draft will expire on November 6, 2012.

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
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   described in the Simplified BSD License.






























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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Maturity Levels  . . . . . . . . . . . . . . . . . . . . . . .  6
     2.1.  Maturity Level 1: Native IPv4 Infrastructure . . . . . . .  7
     2.2.  Maturity Level 2: Internal dual-stacks . . . . . . . . . .  7
     2.3.  Maturity Level 3: Pervasive IPv6 Infrastrcuture  . . . . . 11
   3.  Security Considerations  . . . . . . . . . . . . . . . . . . . 11
   4.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 11
   5.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12
   6.  Informative References . . . . . . . . . . . . . . . . . . . . 12
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12







































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1.  Introduction

   The need for considering the aspects related to IPv4-to-IPv6
   migration for all devices and services connected to the Internet has
   been widely mentioned elsewhere, and it is not our intention to make
   an additional call on it.  Just let us note that many of those
   services are already or will soon be located in datacenters (DC),
   what makes considering the issues associated to DC infrastructure
   migration a key aspect both for these infrastructures themselves, and
   for providing a simpler and clear path to service migration.

   All issues discussed here are related to DC infrastructure migration,
   and are intended to be orthogonal to whatever particular mechanisms
   for making the services hosted in the DC available through IPv6
   beyond the specific aspects related to their deployment on the
   infrastructure.  Those general mechanisms to service migration have
   been discussed in depth elsewhere and are considered to be orthogonal
   to the goal of this discussion.  Though it is obvious that their
   applicability in many cases would depend on the characteristics of
   the supporting DC infrastructure, the migration procedures are
   intended to keep services as independent as possible of these
   processes.

   Furthermore, the combination of the regularity and controlled
   management in a DC interconnection fabric with IPv6 universal end-to-
   end addressing should translate in simpler and faster VM migrations,
   either intra- or inter-DC, and even inter-provider.

   The diagram in Figure 1 depicts a generalized interconnection schema
   in a DC.





















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             |               |
       +-----+-----+   +-----+-----+
       |  Gateway  |   |  Gateway  |          Internet Access
       +-----+-----+   +-----+-----+
             |               |
             +---+-----------+
                 |     |
         +---+---+     +---+---+
         | Core0 |     | CoreN |              Core
         +---+---+     +---+---+
               /  \    /      /
              /    \-----\   /
             /   /---/    \ /
           +--------+       +--------+
         +/-------+ |     +/-------+ |
         | Aggr01 | +-----| AggrN1 | +        Aggregation
         +---+---+/       +--------+/
          /     \         /      \
         /       \       /        \
   +-----+    +-----+   +-----+    +-----+
   | T11 |... | T1x |   | T21 |... | T2y |    Access
   +-----+    +-----+   +-----+    +-----+
   | HyV |    | HyV |   | HyV |    | HyV |    Physical Servers
   +:::::+    +:::::+   +:::::+    +:::::+
   | VMs |    | VMs |   | VMs |    | VMs |    Virtual Machines
   +-----+    +-----+   +-----+    +-----+
   . . . .    . . . .   . . . .    . . . .
   +-----+    +-----+   +-----+    +-----+
   | HyV |    | HyV |   | HyV |    | HyV |
   +:::::+    +:::::+   +:::::+    +:::::+
   | VMs |    | VMs |   | VMs |    | VMs |
   +-----+    +-----+   +-----+    +-----+

                   Figure 1: DC Interconnnection Schema

   o  Hypervisors provide connection services (among others) to virtual
      machines running on physical servers.

   o  Access elements provide connectivity directly to/from physical
      servers.  The access elements are typically placed either top-of-
      rack (ToR) or end-of-row(EoR).

   o  Aggregation elements group several (many) physical racks to
      achieve local integration and provide as much structure as
      possible to data paths.

   o  Core elements connect all aggregation elements acting as the DC
      backbone.



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   o  One or several gateways connecting the DC to the Internet and/or
      other DCs through dedicated links.

   In many actual deployments, depending on DC size and design
   decisions, many of these elements may be combined (core and gateways
   are provider by the same routers, or hypervisors act as access
   elements) or virtualized to some extent, but this layered schema is
   the one that best accommodates the different options to use L2 or L3
   at any of the different DC interconnection layers, and will help us
   in the discussion along the document.


2.  Maturity Levels

   The framework is structured along maturity levels, associated with
   the degree of penetration of IPv6 into the DC communication fabric.
   It is worth noting we are using these levels as a classification
   mechanism, and they have not to be associated with any a succession
   of steps from a v4-only infrastructure to full-fledged v6, but to
   provide a framework that operators, users, and even manufacturers
   could use to assess their plans and products.

   There is no (explicit or implicit) requirement on starting at level
   1, nor to follow them in successive order.  According to their needs
   and the available solutions, DC operators can choose to start or
   remain at a certain level, and freely move from one to another as
   they see fit, without contravening this document.  In this respect,
   the classification intends to support the planning in aspects such as
   the adaptation of the different maturity levels to the evolution of
   traffic patterns, or risk assessment in what relates to deploying new
   components and incorporating change control, integration and testing
   in highly-complex multi-vendor infrastructures.

   Three main maturity levels can be considered when analyzing IPv6
   deployment in the DC infrastructure, all compatible with the
   availability of services running in the DC through IPv6:

   1.  Native IPv4 infrastructure, with gateway routers (or even
       application gateways when services require so) performing the
       adaptation to requests arriving from the IPv6 Internet.

   2.  Internal dual stacks, where native IPv6 and IPv4 are present in
       the infrastructure, up to whatever the layer in the
       interconnection scheme where L3 is applied to packet forwarding

   3.  Pervasive IPv6 infrastructure, including full IPv6 hypervisors,
       which perform the appropriate tunneling or NAT if required by
       internal applications running IPv4.



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2.1.  Maturity Level 1: Native IPv4 Infrastructure

   This maturity level corresponds to the first step that many
   datacenters may take (or have taken) in order to make their external
   services accessible from the IPv6 Internet, and corresponds to IPv6
   traffic patterns totally originated out of the DC or their tenants,
   being a small percentage of the total external requests.  In this
   level, DC network scheme and addressing do not require any important
   change, if any.

   The translation of IPv6 requests into the internal infrastructure
   format occurs at the outmost level of the DC Internet connection.
   This can be typically achieved at the DC gateway routers, that
   support the appropriate address translation mechanisms for those
   services required to be accessed through native IPv6 requests.  The
   policies for applying adaptation can range from performing it only to
   a limited set of specified services to providing a general
   translation service for all public services.  Finer mechanisms, based
   on address ranges or more sophisticated dynamic policies are also
   possible, as they are applied by a limited set of control elements.
   This provides an additional level of control to the usage of IPv6
   routable addresses in the DC environment, which can be especially
   significant at the early deployment stages.

   This model is also suitable to be applied in an "off-shore" mode by
   the service provider connecting the DC infrastructure to the
   Internet, as described in [I-D.sunq-v6ops-contents-transition]

   Even at this level, some implicit advantages of IPv6 application come
   into play, even if they can only be applied at the ingress elements:

   o  Flow labels can be applied to enhance load-balancing, as described
      in [I-D.carpenter-v6ops-label-balance].  Incoming IPv6 requests
      can take advantage of them, and the gateway systems use them as a
      hint for applying load-balancing mechanisms at the IPv4 internal
      accesses.

   o  During VM migration (intra- or even inter-DC), Mobile IP
      mechanisms can be applied to keep service availability during the
      transient state.

   These advantages could potentially be employed to demonstrate the
   value in considering a more comprehensive infrastructure migration.

2.2.  Maturity Level 2: Internal dual-stacks

   This level implies the need for dual-stack elements in some internal
   parts of the DC infrastructure.  This brings some degree of partition



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   in the infrastructure, either in a horizontal (when data paths or
   management interfaces are migrated or left in IPv4 while the rest
   migrate) or a vertical (per tenant or service group), or even both.

   Although it may seem an artificial case, situations requiring this
   maturity level can arise from differen requirements from the user
   base, or the need for technology changes at different points of the
   infrastructure, or even the goal of having the possibility of
   experimenting new solutions in a controled real-operations
   environment.  This maturity level can accommodate different traffic
   patterns, both internal and external, though it better fits to
   scenarios of a clear differentiation of different types of traffic
   (external vs internal, data vs management...), and/or a more or less
   even distribution of external requests.

   At this level, the advantages outlined above on load balancing based
   on flow labels and Mobile IP mechanisms are applicable to any L3-
   based mechanism (intra- as well as inter-DC).  They will translate
   into enhanced VM mobility, more effective load balancing, and higher
   service availability.  Furthermore, the simpler integration provided
   by IPv6 to and from the L2 flat space to the structured L3 one can be
   applied to achieve simpler deployments, as well as alleviating
   encapsulation and fragmentation issues when traversing between L2 and
   L3 spaces.  With an appropriate prefix management, automatic address
   assingment, discovery, and renumbering can be applied not only to
   public service interfaces, but most notably to data and management
   paths.

   Other potential advantages include the application of multicast
   scopes to limit broadcast floods, and the usage of specific security
   headers to enhance tenant differentiation.

   On the other hand, this level requires a much more careful planning
   of addressing schemas and access control, according to security
   levels.  While at level 1 we were talking of relatively few global
   routable addresses, at this one the advantages and risks of using
   different kinds of addresses at each point of the IPv6-aware
   infrastructure.













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    +---------------------+
    |        Internet     |
    +---------+-----------+
              |
        +-----+----+
        |  Gateway |
        +-----+----+
              .
              .           Core Level
              .
           +--+--+
           | FW  |
           +--+--+
              |           Aggregation Level
           +--+--+
           | LB  |
           +--+--+
           _ / \_
          /       \
    +--+--+     +--+--+
    | Web | ... | Web |
    +--+--+     +--+--+
       | \ __ _ _/ |
       | /       \ |
    +--+--+     +--+--+
    |Cache|     | DB  |
    +-----+     +-----+

                 Figure 2: Data Center Application Scheme

   An initial approach corresponding to this maturity level relies on
   taking advantage of specific elements at the aggregation layer
   described in Figure 1, and make them able to provide dual-stack
   gatewaying to the IPv4-based servers and data infrastructure.

   Typically, firewalls (FW) is deployed as the security edge of the
   whole service domain and provides safe access control of this service
   domain from other function domains.  In addition, some application
   optimization devices and security devices (e.g.,Load Balancers, SSL
   VPN, IPS and etc.) may be deployed in the aggregation level to
   alleviate the burden of the server and to guarantee deep security, as
   shown in Figure 2.

   The load balncer (LB) or some other boxes could be upgraded to
   support the data transmission.  There may be two ways to achieve this
   at the edge of the DC: Encapsulation and NAT.  In the encapsulation
   case, the LB function carries the IPv6 traffic over IPv4 using an
   encapsulation (IPv6-in-IPv4).  In the NAT case, there are already



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   some technologies to solve this problem.  For example, DNS and NAT
   device could be concatenated for IPv4/IPv6 translation, if IPv6 host
   needs to visit IPv4 servers.  However, this may require the
   concatenation of multiple network devices, which means the NAT tables
   needs to be synchronized at different devices.  In this document, we
   propose a simplified IPv4/IPv6 translation model, which could be
   implemented in LB device.  The mapping information of IPv4 and IPv6
   will be generated automatically based on the information of LB.  The
   host IP address will be translated without port translation.


                           +----------+------------------------------+
                           |Dual Stack| IPv4-only       +----------+ |
                           |          |            +----|Web Server| |
                           |   +------|------+    /     +----------+ |
   +--------+  +-------+   |   |      |      |   /                   |
   |Internet|--|Gateway|---|---+Load-Balancer+-- \                   |
   |        |  |       |   |   |      |      |    \     +----------+ |
   +--------+  +-------+   |   +------|------+     +----|Web Server| |
                           |          |                 +----------+ |
                           +----------+------------------------------+

                     Figure 3: Dual Stack LB mechanism

   As shown in Figure 3,the LB can be considered divided into two parts:
   The dual-stack part facing the external border, and the IPv4-only
   part which contains the traditional LB functions.  The IPv4 DC is
   allocated an IPv6 prefix which is for the VSIPv6 (Virtual Service
   IPv6 Address).  We suggest that the IPv6 prefix is not the well-known
   prefix in order to avoid the IPv4 routings of the services in
   different DCs spread to the IPv6 network.  The VSIPv4 (Virtual
   Service IPv4 Address) is embedded in VSIPv6 using the allocated IPv6
   prefix.  In this way, the LB has the stateless IP address mapping
   between VSIPv6 and VSIPv4, and synchronization is not required
   between LB and DNS64 server.

   The dual-stack part of the LB has a private IPv4 address pool.  When
   IPv6 packets arrive, the dual-stack part does the one-on-one SIP
   (source IP address) mapping (as defined in
   [I-D.sunq-v6ops-contents-transition]) between IPv4 private address
   and IPv6 SIP.  Because there will be too many UDP/TCP sessions
   between the DC and Internet, the IP addresses binding tables between
   IPv6 and IPv4 are not session-based, but SIP-based.  Thus, the dual-
   stack part of LB builds IP binding stateful tables for the host IPv6
   address and private IPv4 address of the pool.  When the following
   IPv6 packets of the host come from Internet to the LB, the dual stack
   part does the IP address translation for the packets.  Thus, the IPv6
   packets were translated to IPv4 packets and sent to the IPv4 only



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   part of the LB.

2.3.  Maturity Level 3: Pervasive IPv6 Infrastrcuture

   We can consider a DC infrastructure at maturity level 3 when all
   network layer elements, including hypervisors, are IPv6-aware and
   apply it by default.  Conversely with maturity level 1, access from
   the IPv4 Internet is achieved, when required, by protocol translation
   performed at the edge infrastructure elements, or even supplied by
   the service provider as an additional network service.

   This level can be of interest for new deployments willing to apply a
   fresh start aligned with future IPv6 widespread usage, when a
   relevant amount of requests are expected to be using IPv6, or to take
   advantage of any of the potential benefits that an IPv6 support
   infrastructure can provide.  The potential advantages mentioned for
   the previous levels (load balancing based on flow labels, mobility
   mechanisms for transient states in VM or data migration, controled
   multicast, and better mapping of L2 flat space on L3 constructs) can
   be applied at any layer, even especially tailored for individual
   services.  Obviously, the need for a careful planning of address
   space is even stronger here, though the centralized protocol
   translation services should reduce the risk of translation errors
   causing disruptions or security breaches.

   [V6DCS] proposes an approach to a maturity level 3 DC deployment,
   already demonstrated in practice, and claims the advantages of
   achieving level 3 from the beginning, providing some rationale for it
   based on simplifying the migration process.  It relies on stateless
   NAT64 ([RFC6052], [RFC6145]) to enable access from the IPv4 Internet.


3.  Security Considerations

   Need a further ellaboration, but addressing plan issues (on the
   limits to public routable addresses for the whole infrastructure) and
   the need for careful configuration of access control rules at the
   translation points should be addressed.  It must be noted that this
   is specially sensitive in the cases of maturity level 2 (as the
   translation points are potentially distributed) and when translation
   is offered as an external service in maturity levels 1 and 3 (as
   there can be operational mismatches).


4.  IANA Considerations

   None.




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5.  Acknowledgements

   We would like to thank Tore Anderson and Ray Hunter for their
   questions and comments.


6.  Informative References

   [I-D.carpenter-v6ops-label-balance]
              Carpenter, B., Jiang, S., and W. Tarreau, "Using the IPv6
              Flow Label for Server Load Balancing",
              draft-carpenter-v6ops-label-balance-02 (work in progress),
              March 2012.

   [I-D.sunq-v6ops-contents-transition]
              Sun, Q., Liu, D., Zhao, Q., Liu, Q., Xie, C., Li, X., and
              J. Qin, "Rapid Transition of IPv4 contents to be IPv6-
              accessible", draft-sunq-v6ops-contents-transition-03 (work
              in progress), March 2012.

   [RFC6052]  Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X.
              Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052,
              October 2010.

   [RFC6145]  Li, X., Bao, C., and F. Baker, "IP/ICMP Translation
              Algorithm", RFC 6145, April 2011.

   [V6DCS]    "The case for IPv6-only data centres", <https://
              ripe64.ripe.net/presentations/
              67-20120417-RIPE64-
              The_Case_for_IPv6_Only_Data_Centres.pdf>.


Authors' Addresses

   Zhonghua Chen
   China Telecom
   P.R.China

   Phone:
   Email: 18918588897@189.cn










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   Diego R. Lopez
   Telefonica I+D
   Don Ramon de la Cruz, 84
   Madrid  28006
   Spain

   Phone: +34 913 129 041
   Email: diego@tid.es


   Tina Tsou
   Huawei Technologies (USA)
   2330 Central Expressway
   Santa Clara, CA  95050
   USA

   Phone: +1 408 330 4424
   Email: Tina.Tsou.Zouting@huawei.com


   Cathy Zhou
   Huawei Technologies
   Bantian, Longgang District
   Shenzhen  518129
   P.R. China

   Phone:
   Email: cathy.zhou@huawei.com























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