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Versions: 00 01 02 03 04 05 draft-ietf-v6ops-dc-ipv6

Network Working Group                                            Z. Chen
Internet-Draft                                             China Telecom
Intended status: Standards Track                                D. Lopez
Expires: April 22, 2013                                   Telefonica I+D
                                                                 T. Tsou
                                               Huawei Technologies (USA)
                                                                 C. Zhou
                                                     Huawei Technologies
                                                        October 19, 2012

              IPv6 Operational Guidelines for Datacenters


   This document is intended to provide operational guidelines for
   datacenter operators planning to deploy IPv6 in their
   infrastructures.  It aims to offer a reference framework 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

   Apart from facilitating the transition to IPv6, the mechanisms
   outlined here are intended to make this transition 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

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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   time.  It is inappropriate to use Internet-Drafts as reference
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   This Internet-Draft will expire on April 22, 2013.

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   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   described in the Simplified BSD License.

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Transition Stages  . . . . . . . . . . . . . . . . . . . . . .  6
     2.1.  Experimental Stage. Native IPv4 Infrastructure . . . . . .  7
       2.1.1.  Off-shore v6 Access  . . . . . . . . . . . . . . . . .  8
     2.2.  Dual Stack Stage. Internal Adaptation  . . . . . . . . . .  8
       2.2.1.  Dual-stack at the Aggregation Layer  . . . . . . . . .  9
       2.2.2.  Dual-stack Extended OS/Hypervisor  . . . . . . . . . . 11
     2.3.  Next Generation Stage. Pervasive IPv6 Infrastrcuture . . . 11
   3.  Security Considerations  . . . . . . . . . . . . . . . . . . . 12
   4.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 12
   5.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13
   6.  Informative References . . . . . . . . . . . . . . . . . . . . 13
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14

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1.  Introduction

   The need for considering the aspects related to IPv4-to-IPv6
   transition 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
   transition a key aspect both for these infrastructures themselves,
   and for providing a simpler and clear path to service transition.

   All issues discussed here are related to DC infrastructure
   transition, 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 transition have
   been discussed in depth elsewhere (see, for example
   [I-D.ietf-v6ops-icp-guidance] and
   [I-D.chkpvc-enterprise-incremental-ipv6]) 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 transition procedures are
   intended to keep services as independent as possible of these

   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

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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, some 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.  Transition Stages

   The framework is structured along transition stages, associated with
   the degree of penetration of IPv6 into the DC communication fabric.
   It is worth noting we are using these stages 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 the
   stage describe in first place, 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 stage, 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 transition stages 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 transition stages can be considered when analyzing IPv6
   deployment in the DC infrastructure, all compatible with the
   availability of services running in the DC through IPv6:

   o  Experimental.  The DC keeps a native IPv4 infrastructure, with
      gateway routers (or even application gateways when services
      require so) performing the adaptation to requests arriving from
      the IPv6 Internet.

   o  Dual stack.  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.

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   o  Next generation.  The DC has a fully pervasive IPv6
      infrastructure, including full IPv6 hypervisors, which perform the
      appropriate tunneling or NAT if required by internal applications
      running IPv4.

2.1.  Experimental Stage. Native IPv4 Infrastructure

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

   It is important to remark that in no case this can be considered a
   permanent stage in the transition, or even a long-term solution for
   incorporating IPv6 into the DC infrastructure.  This stage is only
   recommended for exprimentation or early evalution purposes.

   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 in the experimentation or early deployment phases this
   stage is applicable to.

   Even at this stage, 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-flow-label-balancing].  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

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

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2.1.1.  Off-shore v6 Access

   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].

   When this off-shore mode is applied, the original source address will
   be hidden to the DC infrastructure, and therefore identification
   techniques based on it, such as geolocation or reputation evaluation,
   will be hampered.  Unless there is a specific trust link between the
   DC operator and the ISP, and the DC operator is able to access
   equivalent identification interfaces provided by the ISP as an
   additional service, the off-shore experimental stage cannot be
   considered applicable when source address identification is required.

2.2.  Dual Stack Stage. Internal Adaptation

   This stage requires dual-stack elements in some internal parts of the
   DC infrastructure.  This brings some degree of partition 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
   stage 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, at the price of the additional complexity of dealing
   with a double protocol stack, as noted in
   [I-D.ietf-v6ops-icp-guidance] and elsewhere.

   This transition stage 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.  A common scenario would include
   native dual stack servers for certain services combined with single
   stack ones for others (web server in dual stack and database servers
   only supporting v4, for example).

   At this stage, 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

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   encapsulation and fragmentation issues when traversing between L2 and
   L3 spaces.  With an appropriate prefix management, automatic address
   assignment, discovery, and renumbering can be applied not only to
   public service interfaces, but most notably to data and management

   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 stage requires a much more careful planning
   of addressing schemas and access control, according to security
   levels.  While the experimental stage implies relatively few global
   routable addresses, this one brings the advantages and risks of using
   different kinds of addresses at each point of the IPv6-aware

2.2.1.  Dual-stack at the Aggregation Layer

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

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                 Figure 2: Data Center Application Scheme

   An initial approach corresponding to this transition stage 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) are 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 based on 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 balancer (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
   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.  As described below, a
   simplified IPv4/IPv6 translation model can be applied, which could be
   implemented in the LB device.  The mapping information of IPv4 and
   IPv6 will be generated automatically based on the information of the
   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

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   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
   part of the LB.

2.2.2.  Dual-stack Extended OS/Hypervisor

   Another option for deploying a infrastructure at the dual-stack stage
   would bring dual-stack much closer to the application servers, by
   requiring hypervisors, VMs and applications in the v6-capable zone of
   the DC to be able to operate in dual stack.  This way, incoming
   connections would be dealt in a seamless manner, while for outgoing
   ones an OS-specific replacement for system calls like gethostbyname()
   and getaddrinfo() would accept a character string (an IPv4 literal,
   an IPv6 literal, or a domain name) and would return a connected
   socket or an error message, having executed a happy eyeballs
   algorithm ([RFC6555]).

   If these hypothetical system call replacements were smart enough,
   they would allow the transparent interoperation of DCs with different
   levels of v6 penetration, either horizontal (internal data paths are
   not migrated, for example) or vertical (per tenant or service group).
   This approach requires, on the other hand, all the involved DC
   infrastructure to become dual-stack, as well as some degree of
   explicit application adaptation.

2.3.  Next Generation Stage. Pervasive IPv6 Infrastrcuture

   We can consider a DC infrastructure at the next generation stage when
   all network layer elements, including hypervisors, are IPv6-aware and
   apply it by default.  Conversely with the experimental stage, access

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   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 next generation DC deployment,
   already demonstrated in practice, and claims the advantages of
   materializing the stage from the beginning, providing some rationale
   for it based on simplifying the transition process.  It relies on
   stateless NAT64 ([RFC6052], [RFC6145]) to enable access from the IPv4

3.  Security Considerations

   A thorough collection of operational security aspects for IPv6
   network is made in [I-D.vyncke-opsec-v6].  Most of them, with the
   probable exception of those specific to residential users, are
   applicable in the environment we consider in this document.  Let us
   just emphasize the relevance of addressing plan issues (and the
   limits to public routable addresses for the whole infrastructure),
   and the need for careful configuration of access control rules at the
   translation points.  This latter one is specially sensitive in
   infrastructures at the dual-stack stage, as the translation points
   are potentially distributed, and when protocol translation is offered
   as an external service, since there can be operational mismatches.

4.  IANA Considerations


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5.  Acknowledgements

   We would like to thank Tore Anderson, Ray Hunter, Arturo Servin, Joel
   Jaeggli, Fred Baker, Lorenzo Colitti, and Dan York for their
   questions, suggestions and comments.

6.  Informative References

              Carpenter, B., Jiang, S., and W. Tarreau, "Using the IPv6
              Flow Label for Server Load Balancing",
              draft-carpenter-flow-label-balancing-01 (work in
              progress), June 2012.

              Chittimaneni, K., Chown, T., Howard, L., Kuarsingh, V.,
              Pouffary, Y., and E. Vyncke, "Enterprise Incremental
              IPv6", draft-chkpvc-enterprise-incremental-ipv6-01 (work
              in progress), July 2012.

              Carpenter, B. and S. Jiang, "IPv6 Guidance for Internet
              Content and Application Service Providers",
              draft-ietf-v6ops-icp-guidance-04 (work in progress),
              September 2012.

              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.

              Chittimaneni, K., Kaeo, M., and E. Vyncke, "Operational
              Security Considerations for IPv6 Networks",
              draft-vyncke-opsec-v6-01 (work in progress), July 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.

   [RFC6555]  Wing, D. and A. Yourtchenko, "Happy Eyeballs: Success with
              Dual-Stack Hosts", RFC 6555, April 2012.

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   [V6DCS]    "The case for IPv6-only data centres", <https://

Authors' Addresses

   Zhonghua Chen
   China Telecom

   Email: 18918588897@189.cn

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

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

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

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

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

   Email: cathy.zhou@huawei.com

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