IPv6 Operational Guidelines for Datacenters
draft-lopez-v6ops-dc-ipv6-03
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft whose latest revision state is "Replaced".
|
|
|---|---|---|---|
| Authors | Zhonghua Chen , Diego R. Lopez , Tina Tsou (Ting ZOU) , Cathy Zhou | ||
| Last updated | 2012-10-20 | ||
| Replaced by | draft-ietf-v6ops-dc-ipv6 | ||
| RFC stream | (None) | ||
| Formats | |||
| Stream | Stream state | (No stream defined) | |
| Consensus boilerplate | Unknown | ||
| RFC Editor Note | (None) | ||
| IESG | IESG state | I-D Exists | |
| Telechat date | (None) | ||
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| Send notices to | (None) |
draft-lopez-v6ops-dc-ipv6-03
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
draft-lopez-v6ops-dc-ipv6-03
Abstract
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
infrastructure.
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
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
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 April 22, 2013.
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
Provisions Relating to IETF Documents
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publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
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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
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, 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
any.
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
accesses.
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
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 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
infrastructure.
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
Internet.
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
None.
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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
[I-D.carpenter-flow-label-balancing]
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.
[I-D.chkpvc-enterprise-incremental-ipv6]
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.
[I-D.ietf-v6ops-icp-guidance]
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.
[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.
[I-D.vyncke-opsec-v6]
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://
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
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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