One document matched: draft-ietf-anima-prefix-management-00.xml
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<rfc category="info" docName="draft-ietf-anima-prefix-management-00" ipr="trust200902">
<front>
<title abbrev="Auto IPv6 Prefix Management">Autonomic IPv6 Edge Prefix Management in
Large-scale Networks</title>
<author fullname="Sheng Jiang" initials="S." role="editor" surname="Jiang">
<organization>Huawei Technologies Co., Ltd</organization>
<address>
<postal>
<street>Q14, Huawei Campus, No.156 Beiqing Road</street>
<city>Hai-Dian District, Beijing, 100095</city>
<country>P.R. China</country>
</postal>
<email>jiangsheng@huawei.com</email>
</address>
</author>
<author fullname="Zongpeng Du" initials="Z." surname="Du">
<organization>Huawei Technologies Co., Ltd</organization>
<address>
<postal>
<street>Q14, Huawei Campus, No.156 Beiqing Road</street>
<city>Hai-Dian District, Beijing, 100095</city>
<country>P.R. China</country>
</postal>
<email>duzongpeng@huawei.com</email>
</address>
</author>
<author fullname="Brian Carpenter" initials="B. E." surname="Carpenter">
<organization abbrev="Univ. of Auckland"/>
<address>
<postal>
<street>Department of Computer Science</street>
<street>University of Auckland</street>
<street>PB 92019</street>
<city>Auckland</city>
<region/>
<code>1142</code>
<country>New Zealand</country>
</postal>
<email>brian.e.carpenter@gmail.com</email>
</address>
</author>
<author fullname="Qiong Sun" initials="Q." surname="Sun">
<organization>China Telecom</organization>
<address>
<postal>
<street>No.118, Xizhimennei Street</street>
<city>Beijing</city>
<code>100035</code>
<country>P. R. China</country>
</postal>
<email>sunqiong@ctbri.com.cn</email>
</address>
</author>
<date day="11" month="January" year="2016"/>
<area>Operations and Management</area>
<workgroup>ANIMA WG</workgroup>
<keyword>Autonomic Networking, Prefix Management</keyword>
<abstract>
<t>This document describes an autonomic solution for IPv6 prefix management
at the edge of large-scale ISP networks. An important purpose of the
document is to use it for validation of the design of various
components of the autonomic networking infrastructure. </t>
</abstract>
</front>
<middle>
<section anchor="intro" title="Introduction">
<t>This document proposes an autonomic solution for IPv6 prefix management in
large-scale networks. The background to Autonomic Networking (AN) is
described in <xref target="RFC7575"/> and <xref target="RFC7576"/>. A
generic autonomic signaling protocol (GRASP) is specified by <xref target="I-D.ietf-anima-grasp"/> and would be used by the proposed
autonomic prefix management solution. An important purpose of the
present document is to use it for validation of the design of GRASP and other
components of the autonomic networking infrastructure described
in <xref target="I-D.behringer-anima-reference-model"/>.</t>
<t>This document is not intended to solve all cases of IPv6 prefix management.
In fact, it assumes that the network's main infrastructure elements already
have addresses and prefixes. The document is dedicated to how to make IPv6 prefix
management at the edges of large-scale networks as autonomic as possible.
It is specifically written for service provider (ISP) networks. Although
there are similarities between ISPs and large enterprise networks,
the requirements for the two use cases differ.</t>
<t>However, the solution is designed in a general way. Its use for a broader scope
than edge prefixes, including some or all infrastructure prefixes, is
left for future discussion.</t>
<t>Note in draft: This version is preliminary. In particular, many
design details may be subject to change until the Anima specifications
become agreed.</t>
</section> <!-- intro -->
<section anchor="term" title="Terminology">
<t>TBD</t>
</section> <!-- term -->
<section anchor="problem" title="Problem Statement">
<t>The autonomic networking use case considered here is autonomic IPv6
prefix management at the edge of large-scale ISP networks.</t>
<t>Although DHCPv6 Prefix Delegation <xref target="RFC3633"/> supports
automated delegation of IPv6 prefixes from one router to another, prefix management is
still largely depending on human planning. In other words, there is no
basic information or policy to support autonomic decisions on the prefix
length that each router should request or be delegated, according to its
role in the network. Roles could be locally defined or could be generic
(edge router, interior router, etc.). Furthermore, IPv6
prefix management by humans tends to be rigid and static after initial planning.</t>
<t>The problem to be solved by autonomic networking is how to dynamically
manage IPv6 address space in large-scale networks, so that
IPv6 addresses can be used efficiently. Here, we limit the problem to assignment of prefixes
at the edge of the network, close to access routers that support individual fixed-line subscribers,
mobile customers, and corporate customers. We assume that the core infrastructure of the
network has already been established with appropriately assigned prefixes.
The AN approach discussed in
this document is based on the assumption that there is a generic
discovery and negotiation protocol that enables direct negotiation
between intelligent IP routers. GRASP <xref target="I-D.ietf-anima-grasp"/> is
intended to be such a protocol.</t>
<section anchor="experience" title="Intended User and Administrator Experience">
<t>The intended experience is, for the administrator(s) of a
large-scale network, that the management of IPv6 address space at the edge of
the network can be run with minimum efforts, as devices at the edge are added
and removed and as customers of all kinds join and leave the network. In the ideal
scenario, the administrator(s) only have to specify a single IPv6 prefix for the
whole network and the initial prefix length for each device role. As far as
users are concerned, IPv6 prefix assignment would occur exactly as it does
in any other network.</t>
<t>The actual prefix usage needs to be logged for potential offline
management operations including audit and security incident tracing.</t>
</section>
<section anchor="params" title="Analysis of Parameters and Information Involved">
<t>For specific purposes of address management, a few parameters are
involved on each edge device (some of them can be pre-configured before
they are connected). They include:</t>
<t><list style="symbols">
<t>Identity, authentication and authorization of this device. This is expected
to use the autonomic networking secure bootstrap process
<xref target="I-D.ietf-anima-bootstrapping-keyinfra"/>, following which the device
could safely take part in autonomic operations. </t>
<t>Role of this device.</t>
<t>An IPv6 prefix length for this device.</t>
<t>An IPv6 prefix that is assigned to this device and its
downstream devices.</t>
</list>A few parameters are involved in the network as a whole. They
are:</t>
<t><list style="symbols">
<t>Identity of a trust anchor, which is a certification authority
(CA) maintained by the network administrator(s), used during the secure
bootstrap process.</t>
<t>Total IPv6 address space available for edge devices. It is one (or several) IPv6
prefix(es).</t>
<t>The initial prefix length for each device role.</t>
</list></t>
<section anchor="device" title="Parameters each device can decide for itself">
<t>This section identifies those of the above parameters that do not
need external information in order for the devices concerned to set
them to a reasonable value after bootstrap or after a network
disruption. There are few of these:</t>
<t><list style="symbols">
<t>Role of this device.</t>
<t>Default IPv6 prefix length for this device.</t>
<t>Identity of this device.</t>
</list>The device may be shipped from the manufacturer with
pre-configured role and default prefix length, which could be modified
by an autonomic mechanism.</t>
</section>
<!-- device -->
<section anchor="intent" title="Information needed from policy intent">
<t>This section identifies those parameters that need external
information about policy intent in order for the devices concerned
to set them to a non-default value.</t>
<t><list style="symbols">
<t>Non-default value for the IPv6 prefix length for this device.
This needs to be decided based on the role of this device.</t>
<t>The initial prefix length for each device role.</t>
<t>Whether to allow the device request more address space.</t>
<t>The policy when to request more address space, for example, if
the address usage reaches a certain limit or percentage.</t>
</list></t>
</section>
<section anchor="compare" title="Comparison with current solutions">
<t>This section briefly compares the above use case with current
solutions. Currently, the address management is still largely
dependent on human planning. It is rigid and static after initial
planning. Address requests will fail if the configured address
space is used up.</t>
<t>Some autonomic and dynamic address management functions may
be achievable by extending the existing protocols, for example,
extending DHCPv6-PD to request IPv6 prefixes according to the device
role. However, defining uniform device roles may not be a practical
task. Some functions are not suitable to be achieved by any existing
protocols.</t>
<t>Using a generic autonomic discovery and negotiation
protocol instead of specific solutions has the advantage that
additional parameters can be included in the autonomic solution
without creating new mechanisms. This is the principal argument for
a generic approach.</t>
</section>
<!-- intent -->
</section>
<section anchor="interact" title="Interaction with other devices">
<section anchor="peers" title="Information needed from other devices">
<t>This section identifies those of the above parameters that need
external information from neighbor devices (including the upstream
devices). In many cases, two-way dialogue with neighbor devices is
needed to set or optimize them.</t>
<t><list style="symbols">
<t>Identity of a trust anchor.</t>
<t>The device will need to discover a device, from which it can
acquire IPv6 address space.</t>
<t>The initial prefix length for each device role, particularly
for its own downstream devices.</t>
<t>The default value of the IPv6 prefix length may be overridden
by a non-default value.</t>
<t>The device will need to request and acquire IPv6 prefix that
is assigned to this device and its downstream devices.</t>
<t>The device may respond to prefix delegation request from its
downstream devices.</t>
<t>The device may require to be assigned more IPv6 address
space, if it used up its assigned IPv6 address space.</t>
</list></t>
</section>
<!-- peers -->
<section anchor="monitor" title="Monitoring, diagnostics and reporting">
<t>This section discusses what role devices should play in
monitoring, fault diagnosis, and reporting.</t>
<t><list style="symbols">
<t>The actual address assignments need to be logged for the
potential offline management operations.</t>
<t>In general, the usage situation of address space should be
reported to the network administrators, in an abstract way, for
example, statistics or visualized report.</t>
<t>A forecast of address exhaustion should be reported.</t>
</list></t>
</section>
<!-- monitor -->
</section>
</section>
<section title="Autonomic Edge Prefix Management Solution">
<t>This section introduces an autonomic edge prefix management solution. It
uses the generic discovery and negotiation protocol defined by <xref target="I-D.ietf-anima-grasp"/>.
The relevant options are defined in <xref target="prefixNegoOptions"/>.</t>
<t>The procedures described below are carried out by an Autonomic Service Agent (ASA) in each
device that participates in the solution. We will refer to this as the PrefixManager ASA.</t>
<t/>
<section title="Behaviors on prefix requesting device">
<t>If the device containing an PrefixManager ASA has used up its
address pool, it can request more space according to its requirements.
It should decide the length of the requested prefix by the
intent-based mechanism, described in <xref target="prefixManageIntent"/>.
</t>
<t>An PrefixManager ASA that needs additional address space
should firstly discover peers that may be able to provide extra
address space. The ASA should send out a GRASP Discovery message
that contains an PrefixManager Objective option <xref target="prefixObjOption"/>
in order to discover peers also supporting that option. Then it should
choose one such peer, most likely the first to respond.</t>
<t>If the GRASP discovery Response message carries a divert option
pointing to an off-link PrefixManager ASA, the
requesting ASA may initiate negotiation with that ASA
diverted device to find out whether it can provide the
requested length prefix.</t>
<t>In any case, the requesting ASA will act as a GRASP negotiation initiator
by sending a GRASP Request message with an PrefixManager Objective option. The
ASA indicates in this option both the length of the requested prefix
and whether the ASA supports the DHCPv6 Prefix Delegation (PD)
function <xref target="RFC3633"/>. This starts a GRASP negotiation
process.</t>
<t>During the subsequent negotiation, the ASA will decide at each
step whether to accept the offered prefix. That decision, and the decision
to end negotiation, is an implementation choice.</t>
<t>The ASA could alternatively initiate rapid mode GRASP discovery
with an embedded negotiation request, if it is implemented.</t>
</section>
<section title="Behaviors on prefix providing device">
<t>A device that receives a Discovery message with an PrefixManager Objective
option should respond with a GRASP Response message if it contains an PrefixManager ASA.
Further details of the discovery process are described in <xref target="I-D.ietf-anima-grasp"/>.
When this ASA receives a subsequent Request message it should conduct a GRASP negotiation
sequence, using Negotiate, Confirm-waiting, and Negotiation-ending
messages as appropriate. The Negotiate messages carry an PrefixManager
Objective option. This will indicate whether the sending device supports
the PD function. More importantly, it will indicate the prefix and
its length offered to the requesting ASA. As described in <xref target="I-D.ietf-anima-grasp"/>,
negotiation will continue until either end stops it with a Negotiation-ending
message. If the negotiation succeeds, the prefix providing ASA will
remove the negotiated prefix from its pool, and the requesting ASA will
add it. If the negotiation fails, the party sending the Negotiation-ending
message may include an error code string. </t>
<t>During the negotiation, the ASA will decide at each step how large
a prefix to offer. That decision, and the decision to end negotiation, is
an implementation choice.</t>
<t>The ASA could alternatively negotiate in response to rapid mode GRASP discovery,
if it is implemented.</t>
<t>This specification is independent of whether the PrefixManager ASAs are all
embedded in routers, but that would be a rather natural scenario.
A gateway router in a hierarchical network topology normally
provides prefixes for routers within its subnet, and it is likely
to contain the first PrefixManager ASA discovered by its downstream routers.
However, the GRASP discovery model, including its Redirect feature, means
that this is not an exclusive scenario, and a downstream PrefixManager ASA could
negotiate a new prefix with a router other than its upstream router.</t>
<t>A resource shortage may cause the gateway router to request more
resource in turn from its own upstream device. This would be another independent
GRASP discovery and negotiation process. During the processing time, the
gateway router should send a Confirm-waiting Message to the initial
requesting router, to extend its timeout. When the new resource becomes
available, the gateway router responds with a GRASP Negotiate message
with a prefix length matching the request.</t>
<t>The algorithm to choose which prefixes to assign on the prefix
providing devices is an implementation choice.</t>
</section>
<section title="Behavior after Successful Negotiation">
<t>Upon receiving a GRASP Negotiation-ending message that indicates that
an acceptable prefix length is available, the requesting device may
request the prefix using DHCPv6 PD, if both ASAs have indicated that
they are within a device that supports PD. Otherwise, it is
permissible for the initiating ASA to use the negotiated prefix
without further messages.</t>
<t>[Author's note: It is not intended to undermine DHCPv6 PD. But in fact, if PD
is not supported and the GRASP negotiation has succeeded, there should be no
problem with this and it seems consistent as a solution.]</t>
<t><!--[Author's note: undecided between PDrequest-failure-negotiation (the current description) or negotiation-PDrequest models.]
For now, replaced by discovery (negotiation length) - PDrequest.
Report Prefix Status (not included for now). This may have information leak issues.--></t>
</section>
<section title="Prefix logging">
<t>Within the autonomic prefix management, all the prefix assignment
is done by devices without human intervention. It is therefore
important to record all the prefix assignment history. However, the
logging and reporting process is out of scope for this specification.</t>
</section>
</section>
<section anchor="prefixNegoOptions" title="Autonomic Prefix Management Options">
<t>This section defines the GRASP options that are used to support
autonomic prefix management.</t>
<section anchor="prefixObjOption" title="Edge Prefix Objective Option">
<t>The PrefixManager Objective option is a GRASP objective option conforming
to <xref target="I-D.ietf-anima-grasp"/>. Its name is "PrefixManager" (see
<xref target="iana"/>) and it carries up to three data items as its value:
the PD support flag, the prefix length, and the actual prefix bits.
The format of the PrefixManager Objective option is described
as follows in CBOR data definition language (CDDL)
<xref target="I-D.greevenbosch-appsawg-cbor-cddl"/>:</t>
<figure>
<artwork><![CDATA[
objective = ["PrefixManager", objective-flags, loop-count,
PD-support, length, ?prefix]
loop-count = 0..255 ; as in the GRASP specification
objective-flags /= ; as in the GRASP specification
PD-support = true / false ; indicates whether sender supports PD
length = 0..128 ; requested or offered prefix length
prefix = bytes .size 16 ; offered prefix in binary format
]]></artwork>
</figure>
</section>
</section>
<section anchor="prefixManageIntent" title="Prefix Management Intent">
<t>With in a single administrative domain, the network operator could
provide intent for all devices with a certain role. Thus it would be possible to
apply an intended policy for every device in a simple way, without
human intervention or configuration files.</t>
<t>For example, the network operator could define the default prefix length for
each type of role. A prefix management intent, which contains all
mapping information of device roles and their default prefix lengths,
should be flooded in the network, through the Autonomic Control Plane
(ACP) <xref target="I-D.ietf-anima-autonomic-control-plane"/>. The
intent flooding mechanism is not yet defined, but one possibility would be
define a suitable GRASP synchronization objective and flood it through the
network. To make this concrete, there could be an objective defined
as follows:</t>
<figure>
<artwork><![CDATA[
objective = ["Intent.PrefixManager", objective-flags, text]
loop-count = 0..255 ; as in the GRASP specification
objective-flags /= ; as in the GRASP specification
;The text object would be the relevant intent statements (such
;as the example below) transmitted as a single string with all
;whitespace and format characters removed.
]]></artwork>
</figure>
<t>This could be flooded to all nodes, and any PrefixManager ASA that did not receive it for some
reason could obtain a copy using GRASP synchronization. Upon receiving the prefix management intent,
every device can decide its default prefix length by matching its own role.</t>
<section title="Example of Prefix Management Intent">
<t>The prefix management intent in this document is used to carry
mapping information of device roles and their default prefix lengths
in an autonomic domain. For example, an IPRAN operator wants to
configure the prefix length of RNC Site Gateway (RSG) as 34, the
prefix length of Aggregation Site Gateway (ASG) as 44, and the prefix
length of Cell Site Gateway (CSG) as 56. She/he may input the
following intent into the autonomic network:</t>
<figure>
<artwork><![CDATA[{"autonomic_intent":
[
{"model_version": "1.0"},
{"intent_type": "Network management"},
{"autonomic_domain": "Customer_X_intranet"},
{"intent_name": "Prefix management"},
{"intent_version": 73},
{"Timestamp": "20150606 00:00:00"},
{"Lifetime": "Permanent"},
{"signature": "XXXXXXXXXXXXXXXXXXX"},
{"content":
[
{"role": [{"role_name": "RSG"},
{"role_characteristic":
[{"prefix_length": "34"}]}
]},
{"role": [{"role_name": "ASG"},
{"role_characteristic":
[{"prefix_length": "44"}]}
]},
{"role": [{"role_name": "CSG"},
{"role_characteristic":
[{"prefix_length": "56"}]}
]}
]
}
]
}
]]></artwork>
</figure>
</section>
</section>
<section anchor="security" title="Security Considerations">
<t>Relevant security issues are discussed in <xref target="I-D.ietf-anima-grasp"/>.
The preferred security model is that devices are trusted following
the secure bootstrap procedure <xref target="I-D.ietf-anima-bootstrapping-keyinfra"/>
and that a secure Autonomic Control Plane (ACP)
<xref target="I-D.ietf-anima-autonomic-control-plane"/> is in place. </t>
<t>It is RECOMMENDED that DHCPv6 PD, if used, should be operated using
DHCPv6 authentication or Secure DHCPv6.</t>
</section>
<!-- security -->
<section anchor="iana" title="IANA Considerations">
<t>This document defines one new GRASP Objective Option name, "PrefixManager". The IANA is requested to
add this to the GRASP Objective Names Table registry defined by <xref target="I-D.ietf-anima-grasp"/> (if approved).</t>
</section>
<!-- iana -->
<section anchor="ack" title="Acknowledgements">
<t>Valuable comments were received from
Michael Behringer,
Joel Halpern,
and Chongfeng Xie.</t>
<t>This document was produced using the xml2rfc tool <xref target="RFC2629"/>.</t>
</section>
<!-- ack -->
<section anchor="changes" title="Change log [RFC Editor: Please remove]">
<t>draft-jiang-anima-prefix-management-00: original version,
2014-10-25.</t>
<t>draft-jiang-anima-prefix-management-01: add intent example and
coauthor Zongpeng Du, 2015-05-04.</t>
<t>draft-jiang-anima-prefix-management-02: update references and the
format of the prefix management intent, 2015-10-14.</t>
<t>draft-ietf-anima-prefix-management-00: WG adoption, clarify scope and purpose,
update text to match latest GRASP spec, 2016-01-11.</t>
</section>
<!-- changes -->
</middle>
<back>
<references title="Normative References">
<?rfc include='reference.I-D.ietf-anima-grasp'?>
<?rfc include='reference.I-D.greevenbosch-appsawg-cbor-cddl'?>
<?rfc include='reference.I-D.ietf-anima-bootstrapping-keyinfra'?>
<?rfc include='reference.I-D.ietf-anima-autonomic-control-plane'?>
<?rfc include='reference.RFC.3633'?>
</references>
<references title="Informative References">
<?rfc include='reference.RFC.2629'?>
<?rfc include='reference.RFC.7575'?>
<?rfc include='reference.RFC.7576'?>
<?rfc include='reference.I-D.behringer-anima-reference-model'?>
</references>
</back>
</rfc>
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