One document matched: draft-carpenter-anima-gdn-protocol-03.xml
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<front>
<title abbrev="GDN Protocol">A Generic Discovery and Negotiation Protocol
for Autonomic Networking</title>
<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="Bing Liu" initials="B." surname="Liu">
<organization>Huawei Technologies Co., Ltd</organization>
<address>
<postal>
<street>Q14, Huawei Campus</street>
<street>No.156 Beiqing Road</street>
<city>Hai-Dian District, Beijing</city>
<code>100095</code>
<country>P.R. China</country>
</postal>
<email>leo.liubing@huawei.com</email>
</address>
</author>
<!---->
<date day="20" month="April" year="2015"/>
<abstract>
<t>This document establishes requirements for a protocol that enables intelligent
devices to dynamically discover peer devices, to synchronize state with them,
and to negotiate parameter settings mutually with them. The document then
defines a general protocol for discovery, synchronization and negotiation,
while the technical objectives for specific scenarios are to be described in
separate documents. An Appendix briefly discusses existing protocols with
comparable features.</t>
</abstract>
</front>
<middle>
<section anchor="intro" title="Introduction">
<t>The success of the Internet has made IP-based networks bigger and
more complicated. Large-scale ISP and enterprise networks have become more and more
problematic for human based management. Also, operational costs are growing quickly.
Consequently, there are increased requirements for autonomic behavior in the networks.
General aspects of autonomic networks are discussed in
<xref target="I-D.irtf-nmrg-autonomic-network-definitions"/>
and <xref target="I-D.irtf-nmrg-an-gap-analysis"/>.
<!-- A reference model for autonomic networking is given in
<xref target="I-D.behringer-anima-reference-model"/> -->
In order to fulfil autonomy, devices that embody autonomic service agents
need to be able to discover each other, to synchronize state with each other,
and to negotiate parameters and resources directly with each other.
There is no restriction on the type of parameters and resources concerned,
which include very basic information needed for addressing and routing,
as well as anything else that might be configured in a conventional network.</t>
<t>Following this Introduction, <xref target="reqts"/> describes the requirements
for network device discovery, synchronization and negotiation.
Negotiation is an iterative process, requiring multiple message exchanges forming
a closed loop between the negotiating devices. State synchronization, when needed,
can be regarded as a special case of negotiation, without iteration.
<xref target="highlevel"/> describes a behavior model for a protocol
intended to support discovery, synchronization and negotiation. The
design of Generic Discovery and Negotiation Protocol (GDNP) in <xref target="Overview"/>
of this document is mainly based on this behavior model. The relevant capabilities
of various existing protocols are reviewed in <xref target="current"/>.</t>
<t>The proposed discovery mechanism is oriented towards synchronization and
negotiation objectives. It is based on a neighbor discovery process, but
also supports diversion to off-link peers. Although many negotiations will occur
between horizontally distributed peers, many target scenarios are hierarchical
networks, which is the predominant structure of current large-scale networks.
However, when a device starts up with no pre-configuration, it has no
knowledge of a hierarchical superior. The protocol itself is capable of
being used in a small and/or flat network structure such as a small
office or home network as well as a professionally managed network.
Therefore, the discovery mechanism needs to be able to allow a device
to bootstrap itself without making any prior assumptions about network
structure. </t>
<t>Because GDNP can be used to perform a decision process among distributed
devices or between networks, it must run in a secure and strongly authenticatd
environment.
<!-- adopts a tight certificate-based security mechanism,
which needs a Public Key Infrastructure (PKI) <xref target="RFC5280"/> system.
The PKI may be managed by an operator or be autonomic, as discussed
in <xref target="I-D.pritikin-anima-bootstrapping-keyinfra"/>. --></t>
<t>It is understood that in realistic deployments, not all devices will
support GDNP. It is expected that some autonomic service agents will manage
a group of non-autonomic nodes, and that other non-autonomic nodes
will be managed traditionally. Such mixed scenarios
are not discussed in this specification.</t>
</section>
<!-- intro -->
<section anchor="reqts" title="Requirement Analysis of Discovery, Synchronization and Negotiation">
<t>This section discusses the requirements for discovery, negotiation
and synchronization capabilities.</t>
<section title="Requirements for Discovery">
<t>In an autonomic network we must assume that when a device starts up
it has no information about any peer devices, the network structure,
or what specific role it must play. In some cases, when a
new application session starts up within a device, the device may again lack
information about relevant peer devices. It might be necessary to set
up resources on multiple other devices, coordinated and matched to
each other so that there is no wasted resource. Security settings
might also need updating to allow for the new device or user.
Therefore a basic requirement is that there must be a mechanism by
which a device can separately discover peer devices for each of the
technical objectives that it needs to manage. Some objectives may
only be significant on the local link, but others may be significant
across the routed network and require off-link operations. Thus,
the relevant peer devices might be immediate neighbors on the same
layer 2 link or they might be more distant and only accessible via
layer 3. The mechanism must therefore support both on-link discovery
and off-link discovery of peers that support specific technical
objectives.</t>
<t>The relevant peer devices may be different for different technical
objectives. Therefore discovery needs to be repeated as often as
necessary to find peers capable of acting as counterparts for each
objective that a discovery initiator needs to handle. In many
scenarios, the discovery process may be followed by a synchronization
or negotiation process. Therefore, a discovery objective may be associated with
one or more synchronization or negotiation objectives.</t>
<t>When a device first starts up, it has no knowledge of the network structure.
Therefore the discovery process must be able to support any network scenario,
assuming only that the device concerned is bootstrapped from factory condition.
</t>
<t>In some networks, as mentioned above, there will be some
hierarchical structure, at least for certain synchronization or negotiation
objectives. A special case of discovery is that each
device must be able to discover its hierarchical superior for each
such objective that it is capable of handling. This is part of the more
general requirement to discover off-link devices.</t>
<t>During initialisation, a device must be able to establish mutual trust
with the rest of the network and join an authentication mechanism. Although
this will inevitably start with a discovery action, it is a special case
precisely because trust is not yet established. This topic
is the subject of <xref target="I-D.pritikin-anima-bootstrapping-keyinfra"/>.
In addition, depending on the type of network involved, discovery of other
central functions might be needed, such as
<!-- a source of intent distribution
<xref target="I-D.irtf-nmrg-autonomic-network-definitions"/> or -->
the Network Operations
Center (NOC) <xref target="I-D.eckert-anima-stable-connectivity"/>.
GDNP must be capable of supporting such discovery during initialisation,
as well as discovery during ongoing operation.</t>
</section>
<section anchor="synchreq" title="Requirements for Synchronization and Negotiation Capability">
<t>We start by considering routing protocols, the closest
approximation to autonomic networking in widespread use. Routing
protocols use a largely autonomic model based on distributed devices
that communicate repeatedly with each other. However, routing is
mainly based on one-way information synchronization (in either
direction), rather than on bi-directional negotiation. The focus
is reachability, so current routing protocols only consider simple
link status, i.e., up or down, and an underlying assumption is that
all nodes need a consistent view of the network topology. Other information,
such as latency, congestion, capacity, and particularly unused capacity,
would be helpful to get better path selection and utilization rate, but
are not normally used in distributed routing algorithms. Also,
autonomic networks need to be able to manage many more dimensions,
such as security settings, power saving, load balancing, etc.
In general, these items do not apply to all participating nodes, but only
to a subset. A basic requirement for the protocol is therefore the
ability to represent, discover, synchronize and negotiate almost any
kind of network parameter among arbitrary subsets of participating nodes.</t>
<t>Human intervention in complex situations is costly and error-prone.
Therefore, synchronization or negotiation of parameters without human
intervention is desirable whenever the coordination of multiple devices can improve
overall network performance. It follows that a requirement for the protocol
is to be capable of running in any device that would otherwise need
human intervention.</t>
<t>Human intervention in large networks is often replaced by use of a
top-down network management system (NMS). It therefore follows that a
requirement for the protocol is to be capable of running in
any device that would otherwise be managed by an NMS, and that it can
co-exist with an NMS.</t>
<t>Since the goal is to minimize human intervention, it is necessary that the
network can in effect "think ahead" before changing its parameters. In
other words there must be a possibility of forecasting the effect of a
change by a "dry run" mechanism before actually installing the
change. This will be an application of the protocol rather than a feature
of the protocol itself. </t>
<t>Status information and traffic metrics need to be shared between
nodes for dynamic adjustment of resources and for monitoring purposes.
While this might be achieved by existing protocols when they are
available, the new protocol needs to be able to support parameter
exchange, including mutual synchronization, even when no negotiation
as such is required.</t>
<t>Recovery from faults and identification of faulty devices should be
as automatic as possible. However, the protocol's role is limited
to the ability to handle discovery, synchronization and negotiation at
any time, in case an autonomic service agent detects an anomaly such
as a negotiation counterpart failing.</t>
<t>Management logging, monitoring, alerts and tools for intervention are required.
However, these can only be features of individual autonomic service agents.
Another document <xref target="I-D.eckert-anima-stable-connectivity"/> discusses how
such agents may be linked into conventional OAM systems via an Autonomic Control Plane
<xref target="I-D.behringer-anima-autonomic-control-plane"/>. </t>
<t>The protocol needs to be able to deal with a wide variety of
technical objectives, covering any type of network parameter.
Therefore the protocol will need either an explicit information model
describing its messages, or at least a flexible and extensible message
format. One design consideration is whether to adopt an existing
information model or to design a new one. Another consideration is
whether it should be able to carry some or all of the message formats used by
existing configuration protocols.</t>
</section>
<section title="Specific Technical Requirements">
<t>To be a generic platform, the protocol payload format should be
independent of the transport protocol or IP version.
In particular, it should be able to run over IPv6 or IPv4.
However, some functions, such as multicasting or broadcasting on
a link, might need to be IP version dependent. In case of doubt, IPv6 should
be preferred.</t>
<t>The protocol must be able to access off-link counterparts via routable addresses,
i.e., must not be restricted to link-local operation.</t>
<t> The negotiation process must be guaranteed to terminate (with success or failure) and if necessary
it must contain tie-breaking rules for each technical objective that requires them. While this
must be defined specifically for each use case, the protocol should have some general mechanisms
in support of loop and deadlock prevention.</t>
<t>Dependencies and conflicts: In order to
decide a configuration on a given device, the device may need
information from neighbors. This can be established through the
negotiation procedure, or through synchronization if that
is sufficient. However, a given item in a neighbor
may depend on other information from its own neighbors, which may
need another negotiation or synchronization procedure to obtain or decide.
Therefore, there are potential dependencies and conflicts among negotiation or synchronization
procedures. Resolving dependencies and conflicts is a matter for the individual autonomic
service agents involved. To allow this, there need to be clear boundaries and convergence
mechanisms for negotiations. Also some mechanisms are needed to avoid
loop dependencies.</t>
<t>Policy constraints: There must be
provision for general policy intent rules to be applied by all devices in
the network (e.g., security rules, prefix length, resource sharing
rules). However, policy intent distribution might not use the negotiation
protocol itself.</t>
<t>Management monitoring, alerts and intervention:
Devices should be able to report to a monitoring
system. Some events must be able to generate operator alerts and
some provision for emergency intervention must be possible (e.g.
to freeze synchronization or negotiation in a mis-behaving device). These features
may not use the negotiation protocol itself.</t>
<t>The protocol needs to be fully secure against forged messages and
man-in-the middle attacks, and as secure as reasonably possible
against denial of service attacks. It needs to be capable of
encryption in order to resist unwanted monitoring, although this
capability may not be required in all deployments. However, it is not
required that the protocol itself provides these security features; it may
depend on an existing secure environment. </t>
</section>
</section>
<!-- reqts -->
<section anchor="Overview" title="GDNP Protocol Overview">
<section anchor="terms" title="Terminology">
<t>The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
<xref target="RFC2119"/> when they appear in ALL CAPS. When these words
are not in ALL CAPS (such as "should" or "Should"), they have their
usual English meanings, and are not to be interpreted as <xref target="RFC2119"/> key words.</t>
<t>This document uses terminology defined in <xref target="I-D.irtf-nmrg-autonomic-network-definitions"/>.</t>
<t>The following additional terms are used throughout this document:
<list style="symbols">
<t>Discovery: a process by which a device discovers peer devices
according to a specific discovery objective. The discovery results
may be different according to the different discovery objectives.
The discovered peer devices may later be used as negotiation
counterparts or as sources of synchronization data. </t>
<t>Negotiation: a process by which two (or more) devices interact
iteratively to agree on parameter settings that best satisfy the
objectives of one or more devices.</t>
<t>State Synchronization: a process by which two (or more) devices
interact to agree on the current state of parameter
values stored in each device. This is a special case of negotiation
in which information is sent but the devices do not request
their peers to change parameter settings. All other definitions
apply to both negotiation and synchronization. </t>
<t>Objective: An objective in GDNP is a configurable state
of some kind, which occurs in three contexts: Discovery, Negotiation
and Synchronization. In the protocol, an objective is represented by an
identifier (actually a GDNP option number) and if relevant a value.
Normally, a given objective will occur during discovery and negotiation,
or during discovery and synchronization, but not in all three contexts.
<list style="symbols">
<t>One device may support multiple independent objectives.</t>
<t>The parameter described by a given objective is naturally based
on a specific service or function or action. It may in principle be
anything that can be set to a specific logical, numerical or string
value, or a more complex data structure, by a network node.
That node is generally expected to be an autonomic service agent
which may itself manage other nodes.</t>
<t>Discovery Objective: if a node needs to synchronize or negotiate
a specific objective but does not know a peer that supports this objective,
it starts a discovery process. The objective is called a Discovery Objective
during this process.</t>
<!-- A discovery objective may be in one-to-one correspondence
with a synchronization objective or a negotiation objective, or it may
correspond to a certain group of such objectives. -->
<t>Synchronization Objective: an objective whose specific technical content
needs to be synchronized among two or more devices. </t>
<t>Negotiation Objective: an objective whose specific technical content
needs to be decided in coordination with another network device. </t>
</list></t>
<t>Discovery Initiator: a device that spontaneously starts discovery
by sending a discovery message referring to a specific discovery
objective.</t>
<t>Discovery Responder: a peer device which responds to the
discovery objective initiated by the discovery initiator.</t>
<t>Synchronization Initiator: a device that spontaneously starts synchronization
by sending a request message referring to a specific synchronization
objective.</t>
<t>Synchronization Responder: a peer device which responds with the
value of a synchronization objective.</t>
<t>Negotiation Initiator: a device that spontaneously starts
negotiation by sending a request message referring to a specific
negotiation objective.</t>
<t>Negotiation Counterpart: a peer device with which the Negotiation
Initiator negotiates a specific negotiation objective.</t>
<!-- <t>Device Identifier: a public key, which identifies the device in
GDNP messages. It is assumed that its associated private key is
maintained in the device only.</t>
<t>Device Certificate: A certificate for a single device, also the
identifier of the device, further described in <xref target="DeviceID"/>.</t>
<t>Device Certificate Tag: a tag, which is bound to the device
identifier. It is used to present a Device Certificate in short
form.</t> -->
</list></t>
</section>
<section anchor="highlevel" title="High-Level Design Choices">
<t>This section describes a behavior model and some considerations for
designing a generic discovery, synchronization and negotiation protocol, which can
act as a platform for different technical objectives.</t>
<t>NOTE: This protocol is described here in a stand-alone fashion as a
proof of concept. An early version was prototyped by Huawei
and the Beijing University of Posts and Telecommunications. However,
this is not yet a definitive proposal for IETF adoption. In
particular, adaptation and extension of one of the protocols discussed
in <xref target="current"/> might be an option. <!-- Also, the
security model outlined below would in practice be part of a general
security mechanism in an autonomic control plane
<xref target="I-D.behringer-anima-autonomic-control-plane"/>. --> This whole
specification is subject to change as a result.</t>
<t><list style="symbols">
<t>A generic platform<vspace blankLines="1"/>
The protocol is designed as a generic platform, which
is independent from the synchronization or negotiation contents. It takes
care of the general intercommunication between
counterparts. The technical contents will vary according to the
various synchronization or negotiation objectives and the different pairs of
counterparts.<vspace blankLines="1"/></t>
<t>Security infrastructure and trust relationship<vspace blankLines="1"/>
Because this negotiation protocol may directly
cause changes to device configurations and bring significant
impacts to a running network, this protocol <!-- is based on a
restrictive security infrastructure, allowing it to be trusted
and monitored so that every device in this negotiation
system behaves well and remains well protected. -->
is assumed to run within an existing secure environment with
strong authentication.
<vspace blankLines="1"/>
On the other hand, a limited negotiation model
might be deployed based on a limited trust relationship. For
example, between two administrative domains, devices might also
exchange limited information and negotiate some particular
configurations based on a limited conventional or contractual
trust relationship.<vspace blankLines="1"/></t>
<t>Discovery, synchronization and negotiation designed together<vspace blankLines="1"/>
The discovery method and the synchronization and negotiation methods
are designed in the same way and can be combined when this is
useful. These processes can also be performed independently when appropriate.
<list style="symbols">
<t>GDNP discovery is appropriate for efficient discovery of GDNP peers
and allows a rapid mode of operation described in <xref target="discmech"/>.
For some parameters, especially those concerned with application layer
services, a text-based discovery mechanism such as DNS Service Discovery
<xref target="I-D.ietf-dnssd-requirements"/> or
Service Location Protocol <xref target="RFC2608"/>
might be more appropriate. The choice is left to the designers of individual
Autonomic Service Agents.
</t>
</list></t>
<t>A uniform pattern for technical contents<vspace blankLines="1"/>
The synchronization and negotiation contents are defined
according to a uniform pattern. They could be carried either in simple
TLV (Type, Length and Value) format or in payloads described by a
flexible language. The initial protocol design uses the TLV approach.
The format is extensible for unknown future requirements. <vspace blankLines="1"/></t>
<t>A conservative model for synchronization<vspace blankLines="1"/>
GDNP supports bilateral synchronization, which could be used
to perform synchronization among a small number of nodes.
<list style="symbols">
<t>For some parameters, synchronization across
large groups of nodes, possibly including all autonomic nodes, might be needed.
For such cases, a flooding mechanism such as ADNCP
<xref target="I-D.stenberg-anima-adncp"/> is considered more appropriate.
GDNP is designed to coexist with ADNCP. The choice is left to the designers of
individual Autonomic Service Agents.
</t>
</list></t>
<t>A simple initiator/responder model for negotiation<vspace blankLines="1"/>
Multi-party negotiations are too complicated to be modeled and
there might be too many dependencies among the parties to converge
efficiently. A simple initiator/responder model is more feasible
and can complete multiple-party negotiations by indirect steps.
<vspace blankLines="1"/></t>
<t>Organizing of synchronization or negotiation content<vspace blankLines="1"/>
Naturally, the technical content will be
organized according to the relevant function or service. The
content from different functions or services is kept
independent from each other. They are not combined into a
single option or single session because these contents may be
negotiated or synchronized with different counterparts or may be
different in response time.<vspace blankLines="1"/></t>
<t>Self aware network device<vspace blankLines="1"/>Every network
device will be pre-loaded with various functions and be
aware of its own capabilities, typically decided by the hardware,
firmware or pre-installed software. Its exact role may depend on
the surrounding network behaviors, which may include forwarding
behaviors, aggregation properties, topology location, bandwidth,
tunnel or translation properties, etc. The surrounding topology will
depend on the network planning. Following an initial discovery phase,
the device properties and those of its neighbors are the
foundation of the synchronization or negotiation behavior of a specific
device. A device has no pre-configuration for the
particular network in which it is installed.<vspace blankLines="1"/></t>
<t>Requests and responses in negotiation procedures<vspace blankLines="1"/>
The initiator can negotiate with
its relevant negotiation counterpart devices, which may be
different according to the specific negotiation objective. It can request
relevant information from the negotiation counterpart so that it
can decide its local configuration to give the most coordinated
performance. It can request the negotiation counterpart to make a
matching configuration in order to set up a successful
communication with it. It can request certain simulation or
forecast results by sending some dry run conditions.
<vspace blankLines="1"/>Beyond the traditional yes/no answer, the
responder can reply with a suggested alternative if
its answer is 'no'. This would start a bi-directional negotiation
ending in a compromise between the two devices.<vspace blankLines="1"/></t>
<t>Convergence of negotiation procedures<vspace blankLines="1"/>
To enable convergence, when a responder makes a
suggestion of a changed condition in a negative reply, it should
be as close as possible to the original request or previous
suggestion. The suggested value of the third or later negotiation
steps should be chosen between the suggested values from the last
two negotiation steps. In any case there must be a mechanism to
guarantee convergence (or failure) in a small number of steps, such
as a timeout or maximum number of iterations.
<vspace blankLines="1"/>
<list style="symbols">
<t>End of negotiation<vspace blankLines="1"/>
A limited number of rounds, for example three, or a timeout, is needed
on each device for each negotiation objective. It may be an implementation
choice, a pre-configurable parameter, or a network-wide policy intent.
These choices might vary between different types of autonomic service agent.
Therefore, the definition of each negotiation objective MUST clearly specify
this, so that the negotiation can always be terminated properly.
<vspace blankLines="1"/></t>
<t>Failed negotiation<vspace blankLines="1"/>There must be a
well-defined procedure for concluding that a negotiation cannot
succeed, and if so deciding what happens next (deadlock
resolution, tie-breaking, or revert to best-effort
service). Again, this MUST be specified for individual
negotiation objectives, as an implementation choice, a pre-configurable
parameter, or a network-wide policy intent.</t>
</list></t>
</list></t>
</section>
<section title="GDNP Protocol Basic Properties and Mechanisms">
<section title="Required External Security Mechanism">
<t>The protocol SHOULD run within a secure Autonomic Control Plane (ACP)
<xref target="I-D.behringer-anima-autonomic-control-plane"/>. If this is
impossible, it MUST use TLS <xref target="RFC5246"/> or DTLS <xref target="RFC6347"/>
for all messages, based on a local Public Key Infrastructure (PKI)
<xref target="RFC5280"/> managed within the autonomic network itself. </t>
<t>Link-local multicast is used for discovery messages. These cannot be secured,
but responses to discovery messages MUST be secured. However, during initialisation,
before a node has joined the applicable trust infrastructure,
e.g., <xref target="I-D.pritikin-anima-bootstrapping-keyinfra"/>,
it will be impossible to secure certain messages.
Such messages MUST be limited to the strictly necessary minimum. </t>
</section>
<section title="Transport Layer Usage">
<t>The protocol is capable of running over UDP or TCP, except for multicast
discovery messages which can only run over UDP. When running within an ACP,
UDP SHOULD be used for messages not exceeding the minimum IPv6 path MTU,
and TCP SHOULD be used for longer messages. In other words, IPv6 fragmentation
should be avoided. When running without an ACP, TLS MUST be used by default, except
for multicast discovery messages. DTLS MAY be supported as an alternative. </t>
</section>
<section anchor="discmech" title="Discovery Mechanism and Procedures">
<t><list style="symbols">
<t>Separated discovery and negotiation mechanisms<list style="empty">
<t>Although discovery and negotiation or synchronization are defined
together in the GDNP, they are separated mechanisms. The discovery
process could run independently from the negotiation or synchronization
process. Upon receiving a discovery (<xref target="DiscoveryMessage"/>) or request
(<xref target="RequestMessage"/>) message, the
recipient device should return a message in which it either
indicates itself as a discovery responder or diverts the
initiator towards another more suitable device.</t>
<t>The discovery action will normally be followed by
a negotiation or synchronization action. The
discovery results could be utilized by the negotiation
protocol to decide which device the initiator will negotiate
with.</t>
</list></t>
<t>Discovery Procedures<list style="empty">
<t>Discovery starts as an on-link operation. The Divert option
can tell the discovery initiator to contact an off-link
discovery objective device. Every DISCOVERY message is sent
by a discovery initiator via UDP to the ALL_GDNP_NEIGHBOR multicast
address (<xref target="Constants"/>). Every network
device that supports the GDNP always listens to a well-known
UDP port to capture the discovery messages.</t>
<t>If the neighbor device supports the requested discovery objective,
it MAY respond with a Response message (<xref target="ResponseMessage"/>) with
locator option(s). Otherwise, if the neigbor device has cached information
about a device that supports the requested discovery objective (usually
because it discovered the same objective before), it SHOULD
respond with a Response message with a Divert option pointing
to the appropriate Discovery Responder.</t>
<t>If no discovery response is received within a reasonable timeout
(default GDNP_DEF_TIMEOUT milliseconds, <xref target="Constants"/>),
the DISCOVERY message MAY be repeated, with a newly generated
Session ID (<xref target="SessionID"/>). An exponential backoff SHOULD be used
for subsequent repetitions, in order to mitigate possible denial of service attacks.</t>
<t>After a GDNP device successfully discovers a Discovery Responder
supporting a specific objective, it MUST cache this
information. This cache record MAY be used for future
negotiation or synchronization, and SHOULD be passed on when appropriate
as a Divert option to another Discovery Initiator. The cache lifetime
is an implementation choice.</t>
<t>If multiple Discovery Responders are found for the same objective, they
SHOULD all be cached, unless this creates a resource shortage. The method
of choosing between multiple responders is an implementation choice.</t>
<t>A GDNP device with multiple link-layer interfaces (typically a router) MUST
support discovery on all interfaces. If it receives a DISCOVERY message
on a given interface for a specific objective that it does not support and for
which it has not previously discovered a Discovery Responder, it MUST relay
the query by re-issuing the same DISCOVERY message on its other interfaces.
However, it MUST limit the total rate at which it relays discovery messages
to a reasonable value, in order to mitigate possible denial of service attacks.
It MUST cache the Session ID value of each relayed
discovery message and, to prevent loops, MUST NOT relay a DISCOVERY message
which carries such a cached Session ID. </t>
<t>This relayed discovery mechanism, with caching of the results, should be sufficient to support
most network bootstrapping scenarios.</t>
</list></t>
<t>A complete discovery process will start with multicast on the
local link; a neighbor might divert it to an off-link destination,
which could be a default higher-level gateway in a hierarchical network.
Then discovery would continue with a unicast to that gateway; if that gateway
is still not the right counterpart, it should divert to another device,
which is in principle closer to the right counterpart. Finally the right
counterpart responds to start the negotiation or synchronization process.</t>
<t>Rapid Mode (Discovery/Negotiation binding)<list style="empty">
<t>A Discovery message MAY include one or more Negotiation
Objective option(s). This allows a rapid mode of negotiation
described in <xref target="negproc"/>. A similar mechanism
is defined for synchronization in <xref target="synchproc"/>.</t>
</list></t>
</list></t>
</section>
<!-- <section title="Certificate-based Security Mechanism">
<t>A certificate-based security mechanism provides security
properties for GDNP:</t>
<t><list style="symbols">
<t>the identity of a GDNP message sender can be verified by a
recipient.</t>
<t>the integrity of a GDNP message can be checked by the recipient
of the message.</t>
<t>anti-replay protection can be assured by the GDNP message recipient.</t>
</list>The authority of the GDNP message sender depends on a
Public Key Infrastructure (PKI) system with a Certification
Authority (CA), which should normally be run by the network
operator. In the case of a network with no operator, such as a small
office or home network, the PKI itself needs to be established by an
autonomic process, which is out of scope for this specification.</t>
<t>A Request message MUST carry a Certificate option, defined in
<xref target="CertOption"/>. The first Negotiation Message,
responding to a Request message, SHOULD also carry a Certificate
option. Using these messages, recipients build their certificate
stores, indexed by the Device Certificate Tags included in every
GDNP message. This process is described in more detail below.</t>
<t>Every message MUST carry a signature option (<xref target="SignOption"/>).</t>
<t>For now, the authors do not think packet size is a problem. In
this GDNP specification, there SHOULD NOT be multiple certificates
in a single message. The current most used public keys are 1024/2048
bits; some may reach 4096. With overhead included, a single
certificate is less than 500 bytes. Messages are expected to be far shorter
than the normal packet MTU within a modern network.</t>
<section title="Support for algorithm agility">
<t>Hash functions are used to provide message integrity checks. In
order to provide a means of addressing problems that may emerge in
the future with existing hash algorithms, as recommended in
<xref target="RFC4270"/>, a mechanism for negotiating the use of
more secure hashes in the future is provided.</t>
<t>In addition to hash algorithm agility, a mechanism for
signature algorithm agility is also provided.</t>
<t>The support for algorithm agility in this document is mainly a
unilateral notification mechanism from sender to recipient. If the
recipient does not support the algorithm used by the sender, it
cannot authenticate the message. Senders in a single
administrative domain are not required to upgrade to a new
algorithm simultaneously.</t>
<t>So far, the algorithm agility is supported by one-way
notification, rather than negotiation mode. As defined in
<xref target="SignOption"/>, the sender notifies the recipient
what hash/signature algorithms it uses. If the responder doesn't
know a new algorithm used by the sender, the negotiation request
would fail. In order to establish a negotiation session, the
sender MAY fall back to an older, less preferred algorithm.
Certificates and network policy intent SHOULD limit the
choice of algorithms.</t>
</section>
<section title="Message validation on reception">
<t>When receiving a GDNP message, a recipient MUST discard the
GDNP message if the Signature option is absent, or the Certificate
option is in a Request Message.</t>
<t>For the Request message and the Response message with a
Certification Option, the recipient MUST first check the authority
of this sender following the rules defined in <xref target="RFC5280"/>. After successful authority validation,
an implementation MUST add the sender's certification into the
local trust certificate record indexed by the associated Device
Certificate Tag (<xref target="DeviceID"/>).</t>
<t>The recipient MUST now authenticate the sender by verifying the
Signature and checking a timestamp, as specified in <xref target="TimeCheck"/>. The order of two procedures is left as
an implementation decision. It is RECOMMENDED to check timestamp
first, because signature verification is much more computationally
expensive.</t>
<t>The signature field verification MUST show that the signature
has been calculated as specified in <xref target="SignOption"/>. The public key used for signature
validation is obtained from the certificate either carried by the
message or found from a local trust certificate record by
searching the message-carried Device Certificate Tag.</t>
<t>Only the messages that get through both the signature
verifications and timestamp check are accepted and continue to be
handled for their contained GDNP options. Messages that do not
pass the above tests MUST be discarded as insecure messages.</t>
</section>
<section anchor="TimeCheck" title="TimeStamp checking">
<t>Recipients SHOULD be configured with an allowed timestamp Delta
value, a "fuzz factor" for comparisons, and an allowed clock drift
parameter. The recommended default value for the allowed Delta is
300 seconds (5 minutes); for fuzz factor 1 second; and for clock
drift, 0.01 second.</t>
<t>The timestamp is defined in the Signature Option, <xref target="SignOption"/>. To facilitate timestamp checking,
each recipient SHOULD store the following information for each
sender:</t>
<t><list style="symbols">
<t>The receive time of the last received and accepted GDNP
message. This is called RDlast.</t>
<t>The time stamp in the last received and accepted GDNP
message. This is called TSlast.</t>
</list>An accepted GDNP message is any successfully verified
(for both timestamp check and signature verification) GDNP message
from the given peer. It initiates the update of the above
variables. Recipients MUST then check the Timestamp field as
follows:</t>
<t><list style="symbols">
<t>When a message is received from a new peer (i.e., one that
is not stored in the cache), the received timestamp, TSnew, is
checked, and the message is accepted if the timestamp is
recent enough to the reception time of the packet, RDnew:
<list style="empty">
<t>-Delta < (RDnew - TSnew) < +Delta</t>
</list><vspace blankLines="1"/>The RDnew and TSnew values
SHOULD be stored in the cache as RDlast and TSlast.</t>
<t>When a message is received from a known peer (i.e., one
that already has an entry in the cache), the timestamp is
checked against the previously received GDNP message:<list style="empty">
<t>TSnew + fuzz > TSlast + (RDnew - RDlast) x (1 -
drift) - fuzz</t>
</list><vspace blankLines="1"/>If this inequality does not
hold, the recipient SHOULD silently discard the message. If,
on the other hand, the inequality holds, the recipient SHOULD
process the message. <vspace blankLines="1"/>Moreover, if the
above inequality holds and TSnew > TSlast, the recipient
SHOULD update RDlast and TSlast. Otherwise, the recipient MUST
NOT update RDlast or TSlast.</t>
</list>An implementation MAY use some mechanism such as a
timestamp cache to strengthen resistance to replay attacks. When
there is a very large number of nodes on the same link, or when a
cache filling attack is in progress, it is possible that the cache
holding the most recent timestamp per sender will become full. In
this case, the node MUST remove some entries from the cache or
refuse some new requested entries. The specific policy as to which
entries are preferred over others is left as an implementation
decision.</t>
</section>
</section> -->
<section anchor="negproc" title="Negotiation Procedures">
<t>A negotiation initiator sends a negotiation request to a
counterpart device, including a specific negotiation objective.
<!-- It may request relevant information from the
negotiation counterpart so that it can decide its local
configuration to give the most coordinated performance. This would
be sufficient in a case where the required function is limited to
state synchronization.--> It may request the negotiation
counterpart to make a specific configuration. Alternatively, it may
request a certain simulation or forecast result by sending a dry run configuration.
The details, including the distinction between dry run and an actual
configuration change, will be defined separately for each type of negotiation
objective.</t>
<t>If the counterpart can immediately apply the requested
configuration, it will give an immediate positive (accept) answer.
This will end the negotiation phase immediately. Otherwise, it will
negotiate. It will reply with a proposed alternative configuration
that it can apply (typically, a configuration that uses fewer resources
than requested by the negotiation initiator). This will start a
bi-directional negotiation to reach a compromise between the two
network devices.</t>
<t>The negotiation procedure is ended when one of the negotiation
peers sends a Negotiation Ending message, which contains an accept
or decline option and does not need a response from the negotiation
peer. Negotiation may also end in failure (equivalent to a decline)
if a timeout is exceeded or a loop count is exceeded. </t>
<t>A negotiation procedure concerns one objective and one
counterpart. Both the initiator and the counterpart may take part in
simultaneous negotiations with various other devices, or in
simultaneous negotiations about different objectives. Thus, GDNP is
expected to be used in a multi-threaded mode. Certain negotiation
objectives may have restrictions on multi-threading, for example to
avoid over-allocating resources.</t>
<t>Rapid Mode (Discovery/Negotiation linkage)<list style="empty">
<t>A Discovery message MAY include a Negotiation
Objective option. In this case the Discovery message also acts
as a Request message to indicate to the Discovery Responder
that it could directly reply to the Discovery Initiator with
a Negotiation message for rapid processing, if it
could act as the corresponding negotiation
counterpart. However, the indication is only advisory not
prescriptive. </t>
<t>This rapid mode could reduce the interactions between
nodes so that a higher efficiency could be achieved. This
rapid negotiation function SHOULD be configured off by default
and MAY be configured on or off by policy intent.</t>
</list></t>
</section>
<section anchor="synchproc" title="Synchronization Procedure">
<t>A synchronization initiator sends a synchronization request to a
counterpart device, including a specific synchronization objective.
The counterpart responds with a Response
message containing the current value of the requested synchronization
objective. No further messages are needed. If no Response
message is received, the synchronization request MAY be repeated
after a suitable timeout.</t>
<t>In the case just described, the message exchange is unicast and
concerns only one synchronization objective. For large groups of nodes
requiring mutual synchronization, ADNCP <xref target="I-D.stenberg-anima-adncp"/>
is considered more appropriate. In the following case,
several synchronization objectives may be combined.</t>
<!-- <t>A synchronization responder MAY send an unsolicited Response message containing
one or more Synchronization Objective option(s), if and only if the specification
of those objectives
permits it. This MAY be sent as a multicast message to the ALL_GDNP_NEIGHBOR multicast
address (<xref target="Constants"/>). In this case a suitable mechanism is needed
to avoid excessive multicast traffic. This mechanism MUST be defined as part of the
specification of the synchronization objective(s) concerned. It might be a simple rate
limit or a more complex mechanism such as the Trickle algorithm <xref target="RFC6206"/>.</t> -->
<t>Rapid Mode (Discovery/Synchronization linkage)<list style="empty">
<t>A Discovery message MAY include one or more Synchronization
Objective option(s). In this case the Discovery message also acts
as a Request message to indicate to the Discovery Responder
that it could directly reply to the Discovery Initiator with
a Response message with synchronization data for rapid processing,
if the discovery target supports the corresponding synchronization
objective(s). However, the indication is only advisory not
prescriptive.</t>
<t>This rapid mode could reduce the interactions between
nodes so that a higher efficiency could be achieved. This
rapid synchronization function SHOULD be configured off by default
and MAY be configured on or off by policy intent.</t>
</list></t>
</section>
</section>
<section anchor="Constants" title="GDNP Constants">
<t><list style="symbols">
<t>ALL_GDNP_NEIGHBOR<vspace blankLines="1"/>A link-local
scope multicast address used by a GDNP-enabled device to discover
GDNP-enabled neighbor (i.e., on-link) devices . All devices that
support GDNP are members of this multicast group.<list style="symbols">
<t>IPv6 multicast address: TBD1</t>
<t>IPv4 multicast address: TBD2</t>
</list></t>
<t>GDNP Listen Port (TBD3)<vspace blankLines="1"/>A UDP and TCP port that
every GDNP-enabled network device always listens to.</t>
<t>GDNP_DEF_TIMEOUT (60000 milliseconds)<vspace blankLines="1"/>The default timeout used to
determine that a discovery or negotiation has failed to complete.</t>
<t>GDNP_DEF_LOOPCT (6)<vspace blankLines="1"/>The default loop count used to
determine that a negotiation has failed to complete.</t>
</list></t>
</section>
<!-- <section anchor="DeviceID" title="Device Identifier and Certificate Tag">
<t>A GDNP-enabled Device MUST generate a stable public/private key
pair before it participates in GDNP. There MUST NOT be any way of
accessing the private key via the network or an operator interface.
The device then uses the public key as its identifier, which is
cryptographic in nature. It is a GDNP unique identifier for a GDNP
participant.</t>
<t>It then gets a certificate for this public key, signed by a
Certificate Authority that is trusted by other network devices. The
Certificate Authority SHOULD be managed within the local administrative domain,
to avoid needing to trust a third party. The signed certificate would
be used for authentication of the message sender. In a managed
network, this certification process could be performed at a central
location before the device is physically installed at its intended
location. In an unmanaged network, this process must be autonomic,
including the bootstrap phase.</t>
<t>A 128-bit Device Certifcate Tag, which is generated by taking a
cryptographic hash over the device certificate, is a short
presentation for GDNP messages. It is the index key to find the device
certificate in a recipient's local trusted certificate record.</t>
<t>The tag value is formed by taking a SHA-1 hash algorithm
<xref target="RFC3174"/> over the
corresponding device certificate and taking the leftmost 128 bits of
the hash result.</t>
</section> -->
<section anchor="SessionID" title="Session Identifier (Session ID)">
<t>A 24-bit opaque value used to distinguish multiple sessions between
the same two devices. A new Session ID MUST be generated for every
new Discovery or Request message, and for every unsolicited Response message.
All follow-up messages in the same
discovery, synchronization or negotiation procedure, which is initiated
by the request message, MUST carry the same Session ID.</t>
<t>The Session ID SHOULD have a very low collision rate locally. It is
RECOMMENDED to be generated by a pseudo-random algorithm using a seed
which is unlikely to be used by any other device in the same
network <xref target="RFC4086"/>.</t>
</section>
<section anchor="GDNPMessages" title="GDNP Messages">
<t>This document defines the following GDNP message format and types.
Message types not listed here are reserved for future use. The numeric
encoding for each message type is shown in parentheses.</t>
<section title="GDNP Message Format">
<t>GDNP messages share an identical fixed format header and a
variable format area for options. GDNP message headers and options
are in the type-length-value (TLV) format defined in DNCP (see
Section "Type-Length-Value Objects" in <xref target="I-D.ietf-homenet-dncp"/>)<!-- ,
with one difference. In the message header TLVs, the length field
covers the whole message including all options and pads-->.
</t>
<t>Every GDNP message carries <!-- the Device
Certificate Tag of its sender and -->a Session ID. Options are
presented serially in the options field, with padding to
4-byte alignment.</t>
<t>The following diagram illustrates the format of GDNP
messages:</t>
<t><figure>
<artwork><![CDATA[ 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MESSAGE_TYPE | 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Session ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Options (variable length) |
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure></t>
<t><list style="hanging">
<t hangText="MESSAGE_TYPE:"> Identifies the GDNP message type. 16-bit.
<!--</t>
<t hangText="MESSAGE_LEN:"> Total length of the GDNP message including all options and pads. 16-bit. -->
</t>
<t hangText="Reserved:"> Set to zero, ignored on receipt. 8-bit.
</t>
<t hangText="Session ID:"> Identifies this GDNP session, as defined in
<xref target="SessionID"/>. 24-bit.
</t>
<!-- <t hangText="Device Certificate Tag:">
Represents the Device Certificate, which identifies
the negotiation devices, as defined in <xref target="DeviceID"/>.
The Device Certificate Tag is 128 bit, also defined
in <xref target="DeviceID"/>. It is used as index key to find the
device certificate.
</t> -->
<t hangText="Options:"> GDNP Options carried in this message. Options are
defined starting at <xref target="GDNPOptions"/>.
</t></list></t>
</section>
<section anchor="DiscoveryMessage" title="Discovery Message">
<t>DISCOVERY (MESSAGE_TYPE = G1):</t><t>
A discovery initiator sends a DISCOVERY message
to initiate a discovery process.
</t><t>
The discovery initiator sends the DISCOVERY
messages to the link-local ALL_GDNP_NEIGHBOR multicast
address for discovery, and stores the discovery
results (including responding discovery objectives and
corresponding unicast addresses or FQDNs).
</t><t>
A DISCOVERY message MUST include exactly one of the following:
<list style="symbols">
<t>a discovery objective option (<xref target="ObjOption"/>).
</t>
<t>a negotiation objective option (<xref target="ObjOption"/>) to indicate
to the discovery target that it MAY directly reply to
the discovery initiatior with a NEGOTIATION message for
rapid processing, if it could act as the corresponding negotiation counterpart.
The sender of such a DISCOVERY message MUST initialize
a negotiation timer and loop count in the same way as a REQUEST message
(<xref target="RequestMessage"/>).
</t>
<t>one or more synchronization objective options (<xref target="ObjOption"/>)
to indicate to the discovery
target that it MAY directly reply to the discovery initiator with a RESPONSE message
for rapid processing, if it could act as the corresponding synchronization counterpart.</t>
</list></t>
</section>
<section anchor="ResponseMessage" title="Response Message">
<t>RESPONSE (MESSAGE_TYPE = G2):</t><t>
A node which receives a DISCOVERY message sends a
Response message to respond to a discovery. It MUST
contain the same Session ID as the DISCOVERY message.
It MAY include a copy of the discovery objective from
the DISCOVERY message.
</t><t>
If the responding node supports the discovery objective
of the discovery, it MUST include at least one kind of
locator option (<xref target="LocatorOption"/>) to indicate its own
location. A combination of multiple kinds of locator
options (e.g. IP address option + FQDN option) is also
valid.
</t><t>
If the responding node itself does not support the discovery
objective, but it knows the locator of the discovery
objective, then it SHOULD respond to the discovery message with a
divert option (<xref target="DivertOption"/>) embedding a locator
option or a combination of multiple kinds of locator
options which indicate the locator(s) of the discovery
objective.
</t><t>
A node which receives a synchronization request
sends a Response message with the synchronization
data, <!-- A node MAY send an unsolicited Response Message
with synchronization data and this MAY be sent to the
link-local ALL_GDNP_NEIGHBOR multicast address, in accordance
with the rules in <xref target="synchproc"/>.
If the response contains synchronization data, this will
be -->in the form of GDNP Option(s) for the specific
synchronization objective(s).</t>
</section>
<section anchor="RequestMessage" title="Request Message">
<t>REQUEST (MESSAGE_TYPE = G3):</t><t>
A negotiation or synchronization requesting node
sends the REQUEST message to the unicast address (directly
stored or resolved from the FQDN) of the negotiation or
synchronization counterpart (selected from the discovery
results).</t>
<t>A request message MUST include the relevant objective option, with the requested
value in the case of negotiation. </t>
<t>When an initiator sends a REQUEST message, it MUST initialize a negotiation timer
for the new negotiation thread with the value GDNP_DEF_TIMEOUT milliseconds. Unless this
timeout is modified by a CONFIRM-WAITING message (<xref target="ConfirmWaitingMessage"/>),
the initiator will consider that the negotiation has failed when the timer expires. </t>
<t>When an initiator sends a REQUEST message, it MUST initialize the loop count
of the objective option with a value defined in the specification of the option
or, if no such value is specified, with GDNP_DEF_LOOPCT. </t>
</section>
<section anchor="NegotiationMessage" title="Negotiation Message">
<t>NEGOTIATION (MESSAGE_TYPE = G4):</t><t>
A negotiation counterpart sends a NEGOTIATION
message in response to a REQUEST message, a
NEGOTIATION message, or a DISCOVERY message
in Rapid Mode. A negotiation process MAY
include multiple steps.</t>
<t>The NEGOTIATION message MUST include the relevant Negotiation Objective option,
with its value updated according to progress in the negotiation. The sender
MUST decrement the loop count by 1. If the loop count becomes zero both parties
will consider that the negotiation has failed.</t>
</section>
<section anchor="NegotiationEndingMessage" title="Negotiation-ending Message">
<t>NEGOTIATION-ENDING (MESSAGE_TYPE = G5):</t><t>
A negotiation counterpart sends an NEGOTIATION-ENDING
message to close the negotiation. It MUST contain
one, but only one of accept/decline option,
defined in <xref target="AcceptOption"/> and <xref target="DeclineOption"/>.
It could be sent either by the
requesting node or the responding node.</t>
</section>
<section anchor="ConfirmWaitingMessage" title="Confirm-waiting Message">
<t>CONFIRM-WAITING (MESSAGE_TYPE = G6):</t><t>
A responding node sends a CONFIRM-WAITING message to
indicate the requesting node to wait for a further
negotiation response. It might be that the local
process needs more time or that the negotiation
depends on another triggered negotiation. This
message MUST NOT include any other options than the
Waiting Time Option (<xref target="WaitingTimeOption"/>).</t>
</section>
</section>
<section anchor="GDNPOptions" title="GDNP General Options">
<t>This section defines the GDNP general options for the negotiation
and synchronization protocol signalling. Additional option types are reserved for GDNP general
options defined in the future.</t>
<section title="Format of GDNP Options">
<t><figure>
<artwork><![CDATA[ 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| option-code | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| option-data |
| (option-len octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure></t>
<t><list style="hanging">
<t hangText="Option-code:"> An unsigned integer identifying the specific option
type carried in this option.
</t>
<t hangText="Option-len:"> An unsigned integer giving the length of the
option-data field in this option in octets.
</t>
<t hangText="Option-data:"> The data for the option; the format of this data
depends on the definition of the option.</t>
</list></t>
<t>
GDNP options are scoped by using encapsulation. If an
option contains other options, the outer Option-len includes the
total size of the encapsulated options, and the latter apply only to
the outer option.</t>
</section>
<section anchor="DivertOption" title="Divert Option">
<t>The divert option is used to redirect a GDNP request to another
node, which may be more appropriate for the intended negotiation or synchronization. It
may redirect to an entity that is known as a specific negotiation or synchronization
counterpart (on-link or off-link) or a default gateway. The divert
option MUST only be encapsulated in Response messages.
If found elsewhere, it SHOULD be silently ignored.</t>
<t><figure>
<artwork><![CDATA[ 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_DIVERT | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Locator Option(s) of Diversion Device(s) |
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure></t>
<t><list style="hanging">
<t hangText="Option-code:"> OPTION_DIVERT (G32).
</t>
<t hangText="Option-len:"> The total length of diverted destination
sub-option(s) in octets.
</t>
<t hangText="Locator Option(s) of Diversion Device(s):">
Embedded Locator Option(s) (<xref target="LocatorOption"/>)
that point to diverted destination device(s).
</t></list></t>
</section>
<section anchor="AcceptOption" title="Accept Option">
<t>The accept option is used to indicate to the negotiation counterpart
that the proposed negotiation content is accepted.</t>
<t>The accept option MUST only be encapsulated in Negotiation-ending
messages. If found elsewhere, it SHOULD be silently ignored.</t>
<t><figure>
<artwork><![CDATA[ 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_ACCEPT | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure></t>
<t><list style="hanging">
<t hangText="Option-code:"> OPTION_ACCEPT (G33)
</t>
<t hangText="Option-len:"> 0
</t></list></t>
</section>
<section anchor="DeclineOption" title="Decline Option">
<t>The decline option is used to indicate to the negotiation
counterpart the proposed negotiation content is declined and end the
negotiation process.</t>
<t>The decline option MUST only be encapsulated in
Negotiation-ending messages. If found elsewhere, it SHOULD be
silently ignored.</t>
<t><figure>
<artwork><![CDATA[ 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_DECLINE | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure></t>
<t><list style="hanging">
<t hangText="Option-code:"> OPTION_DECLINE (G34)
</t>
<t hangText="Option-len:"> 0
</t></list></t>
<t>Notes: there are scenarios where a negotiation counterpart wants
to decline the proposed negotiation content and continue the
negotiation process. For these scenarios, the negotiation
counterpart SHOULD use a Negotiate message, with either an objective
option that contains at least one data field with all bits set to 1
to indicate a meaningless initial value, or a specific objective
option that provides further conditions for convergence.</t>
</section>
<section anchor="WaitingTimeOption" title="Waiting Time Option ">
<t>The waiting time option is used to indicate that the negotiation
counterpart needs to wait for a further negotiation response, since
the processing might need more time than usual or it might depend on
another triggered negotiation.</t>
<t>The waiting time option MUST only be encapsulated in
Confirm-waiting messages. If found elsewhere, it SHOULD be silently
ignored. When received, its value overwrites the negotiation timer
(<xref target="RequestMessage"/>).</t>
<t>The counterpart SHOULD send a Negotiation, Negotiation-Ending or another
Confirm-waiting message before the negotiation timer expires. If
not, the initiator MUST abandon or restart the negotiation
procedure, to avoid an indefinite wait.</t>
<t><figure>
<artwork><![CDATA[ 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_WAITING | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Time |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure></t>
<t><list style="hanging">
<t hangText="Option-code:"> OPTION_WAITING (G35)
</t>
<t hangText="Option-len:"> 4, in octets
</t>
<t hangText="Time:"> Time in milliseconds
</t></list></t>
</section>
<!-- <section anchor="CertOption" title="Certificate Option">
<t>The Certificate option carries the certificate of the sender. The
format of the Certificate option is as follows:</t>
<t><figure>
<artwork align="center"><![CDATA[ 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION Certificate | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. Certificate (variable length) .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure></t>
<t><list style="hanging">
<t hangText="Option-code:"> OPTION_CERT_PARAMETER (5)
</t>
<t hangText="Option-len:"> Length of certificate in octets
</t>
<t hangText="Public key:"> A variable-length field containing a certificate
</t></list></t>
</section>
<section anchor="SignOption" title="Signature Option">
<t>The Signature option allows public key-based signatures to be
attached to a GDNP message. The Signature option is REQUIRED in
every GDNP message and could be any place within the GDNP message.
It protects the entire GDNP header and options. A TimeStamp has been
integrated in the Signature Option for anti-replay protection. The
format of the Signature option is described as follows:</t>
<t><figure>
<artwork><![CDATA[ 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_SIGNATURE | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| HA-id | SA-id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timestamp (64-bit) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. Signature (variable length) .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure></t>
<t><list style="hanging">
<t hangText="Option-code:">OPTION_SIGNATURE (6)
</t>
<t hangText="Option-len:">12 + Length of Signature field in octets.
</t>
<t hangText="HA-id:">Hash Algorithm id. The hash algorithm is used for
computing the signature result. This design is
adopted in order to provide hash algorithm agility.
The value is from the Hash Algorithm for GDNP
registry in IANA. The initial value assigned
for SHA-1 is 0x0001.
</t>
<t hangText="SA-id:">Signature Algorithm id. The signature algorithm is
used for computing the signature result. This
design is adopted in order to provide signature
algorithm agility. The value is from the Signature
Algorithm for GDNP registry in IANA. The initial
value assigned for RSASSA-PKCS1-v1_5 is
0x0001.
</t>
<t hangText="Timestamp:">The current time of day (NTP-format timestamp
[RFC5905] in UTC (Coordinated Universal Time), a
64-bit unsigned fixed-point number, in seconds
relative to 0h on 1 January 1900.). It can reduce
the danger of replay attacks.
</t>
<t hangText="Signature:">A variable-length field containing a digital
signature. The signature value is computed with
the hash algorithm and the signature algorithm, as
described in HA-id and SA-id. The signature
constructed by using the sender's private key
protects the following sequence of octets:
<vspace blankLines="1"/>
1. The GDNP message header.
<vspace blankLines="1"/>
2. All GDNP options including the Signature option
(fill the signature field with zeroes).
<vspace blankLines="1"/>
The signature field MUST be padded, with all 0, to
the next 16 bit boundary if its size is not an even
multiple of 8 bits. The padding length depends on
the signature algorithm, which is indicated in the
SA-id field.
</t></list></t>
</section> -->
<section anchor="IDOption" title="Device Identity Option">
<t>The Device Identity option carries the identities of the sender
and of the domain(s) that it belongs to. The
format of the Device Identity option is as follows:</t>
<t><figure>
<artwork align="center"><![CDATA[ 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_DEVICE_ID | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. Identities (variable length) .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure></t>
<t><list style="hanging">
<t hangText="Option-code:"> OPTION_DEVICE_ID (G36)
</t>
<t hangText="Option-len:"> Length of identities in octets
</t>
<t hangText="Identities:"> A variable-length field containing the device identity
and one or more domain identities. The format is not yet defined.
</t>
<t hangText="Note:"> Currently this option is a placeholder. It might be removed or modified.
</t></list></t>
</section>
<section anchor="LocatorOption" title="Locator Options">
<t>These locator options are used to present a device's or
interface's reachability information. They are Locator IPv4 Address
Option, Locator IPv6 Address Option and Locator FQDN (Fully
Qualified Domain Name) Option.</t>
<t>Note that it is assumed that all locators are in scope throughout
the GDNP domain. GDNP is not intended to work across disjoint addressing
or naming realms. </t>
<section title="Locator IPv4 address option">
<t><figure>
<artwork><![CDATA[ 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_LOCATOR_IPV4ADDR | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4-Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure></t>
<t><list style="hanging">
<t hangText="Option-code:"> OPTION_LOCATOR_IPV4ADDR (G37)
</t>
<t hangText="Option-len:"> 4, in octets
</t>
<t hangText="IPv4-Address:"> The IPv4 address locator of the device/interface
</t></list></t>
<t>Note: If an operator has internal network address translation for IPv4,
this option MUST NOT be used within the Divert option.</t>
</section>
<section title="Locator IPv6 address option">
<t><figure>
<artwork><![CDATA[ 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_LOCATOR_IPV6ADDR | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| IPv6-Address |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure></t>
<t><list style="hanging">
<t hangText="Option-code:"> OPTION_LOCATOR_IPV6ADDR (G38)
</t>
<t hangText="Option-len:"> 16, in octets
</t>
<t hangText="IPv6-Address:"> The IPv6 address locator of the device/interface
</t></list></t>
<t> Note: A link-local IPv6 address MUST NOT be used when
this option is used within the Divert option.</t>
</section>
<section title="Locator FQDN option">
<t><figure>
<artwork><![CDATA[ 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_FQDN | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Fully Qualified Domain Name |
| (variable length) |
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure></t>
<t><list style="hanging">
<t hangText="Option-code:"> OPTION_FQDN (G39)
</t>
<t hangText="Option-len:"> Length of Fully Qualified Domain Name in octets
</t>
<t hangText="Domain-Name:"> The Fully Qualified Domain Name of the entity
</t></list></t>
<t>Note: Any FQDN which might not be valid throughout the network in question,
such as a Multicast DNS name <xref target="RFC6762"/>, MUST NOT be used when
this option is used within the Divert option.</t>
</section>
</section>
<!---->
</section>
<section title="Objective Options">
<section anchor="ObjOption" title="Format of Objective Options">
<t>An objective option is used to identify objectives for
the purposes of discovery, negotiation or synchronization.
All objectives must follow a common format as follows:</t>
<t><figure>
<artwork><![CDATA[ 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_XXX | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| loop-count | flags | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ value |
. (variable length) .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure></t>
<t><list style="hanging">
<t hangText="Option-code:"> OPTION_XXX: The option code assigned in
the specification of the XXX objective.
</t>
<t hangText="option-len:"> The total length in octets.
</t>
<t hangText="loop-count:"> The loop count. This field is
present if and only if the objective is a negotiation objective.
</t>
<t hangText="flags:"> Flag bits. This field is
present if and only if defined in the specification of the objective.
</t>
<t hangText="value:">
This field is to express the actual value of a negotiation
or synchronization objective. Its format is defined in the
specification of the objective and may be a single value
or a data structure of any kind.
</t></list></t>
</section>
<section anchor="ConsOption" title="General Considerations for Objective Options">
<t>Objective Options MUST be assigned
an option type greater than G63 in the GDNP option table.</t>
<t>An Objective Option that contains no additional
fields, i.e., has a length of 4 octets, is a discovery objective and MUST only be used
in Discovery and Response messages.</t>
<t>The Negotiation Objective Options contain negotiation objectives,
which are various according to different functions/services. They MUST
be carried by Discovery, Request or Negotiation Messages only. The negotiation
initiator MUST set the initial "loop-count" to a value specified in the
specification of the objective or, if no such value is specified, to
GDNP_DEF_LOOPCT.</t>
<t>For most scenarios, there should be initial values in the
negotiation requests. Consequently, the Negotiation Objective options MUST
always be completely presented in a Request message, or in a Discovery
message in rapid mode. If there is no
initial value, the bits in the value field SHOULD all be set to 1 to
indicate a meaningless value, unless this is inappropriate for the
specific negotiation objective.</t>
<t>Synchronization Objective Options are similar, but MUST be carried
by Discovery, Request or Response messages only. They include
value fields only in Response messages. </t>
</section>
<section title="Organizing of Objective Options">
<t>As noted earlier, one negotiation objective is handled by each
GDNP negotiation thread. Therefore, a negotiation objective, which is
based on a specific function or action, SHOULD be organized as a single
GDNP option. It is NOT RECOMMENDED to organize multiple negotiation
objectives into a single option, nor to split a single function
or action into multiple negotiation objectives. </t>
<t>A synchronization objective SHOULD also be organized
as a single GDNP option.</t>
<t>Some objectives will support more than one operational mode.
An example is a negotiation objective with both a "dry run" mode
(where the negotiation is to find out whether the other end can in fact
make the requested change without problems) and a "live" mode. Such
modes will be defined in the specification of such an objective. These
objectives SHOULD include a "flags" octet, with bits indicating the
applicable mode(s).</t>
<t>An objective may have multiple parameters. Parameters
can be categorized into two classes: the obligatory ones presented as
fixed fields; and the optional ones presented in TLV sub-options or
some other form of data structure. The format might be
inherited from an existing management or configuration protocol,
the objective option acting as a carrier for that format.
The data structure might be defined in a formal language, but that is a
matter for the specifications of individual objectives.
There are many candidates, according to the context, such as ABNF, RBNF,
XML Schema, possibly YANG, etc. The GDNP protocol itself is agnostic on
these questions. </t>
<t>It is NOT RECOMMENDED to split parameters in a single objective into
multiple options, unless they have different response periods. An
exception scenario may also be described by split objectives.</t>
</section>
<section title="Vendor Specific Objective Options ">
<t>Option codes G128~159 have been reserved for vendor specific
options. Multiple option codes have been assigned because a single
vendor might use multiple options simultaneously. These vendor
specific options are highly likely to have different meanings when
used by different vendors. Therefore, they SHOULD NOT be used
without an explicit human decision and SHOULD NOT be used in
unmanaged networks such as home networks.</t>
<t>There is one general requirement that applies to all vendor specific
options. They MUST start with a field that uniquely identifies the enterprise
that defines the option, in the form of a registered 32 bit Private Enterprise Number (PEN)
<xref target="I-D.liang-iana-pen"/>. There is no default value for this field.
Note that it is not used during discovery. It MUST be verified during negotiation
or synchronization.</t>
<t>In the case of a vendor-specific objective, the loop count and flags,
if present, follow the PEN.</t>
<t><figure>
<artwork><![CDATA[ 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_vendor | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PEN |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| loop-count | flags | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ value |
. (variable length) .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure></t>
<t><list style="hanging">
<t hangText="Option-code:"> OPTION_vendor (G128~159)
</t>
<t hangText="Option-len:"> The total length in octets.</t>
<t hangText="PEN:"> Private Enterprise Number.</t>
<t hangText="loop-count:"> The loop count. This field is
present if and only if the objective is a negotiation objective.
</t>
<t hangText="flags:"> Flag bits. This field is
present if and only if defined in the specification of the objective.
</t>
<t hangText="value:"> This field is to express the actual value of a negotiation
or synchronization objective. Its format is defined in the vendor's
specification of the objective.</t>
</list></t>
</section>
<section title="Experimental Objective Options">
<t>Option codes G176~191 have been reserved for experimental options.
Multiple option codes have been assigned because a single experiment
may use multiple options simultaneously. These experimental options
are highly likely to have different meanings when used for different
experiments. Therefore, they SHOULD NOT be used without an explicit
human decision and SHOULD NOT be used in unmanaged networks such as
home networks.</t>
<t>These option codes are also RECOMMENDED for use in documentation
examples.</t>
</section>
</section>
</section>
<section title="Items for Future Work">
<t>There are various design questions that are worthy of more work
in the near future, as listed below (statically numbered for reference purposes):</t>
<t><list style="symbols">
<!-- <t>1. UDP vs TCP: For now, this specification suggests UDP and TCP as
message transport mechanisms. This is not clarified yet. UDP
is good for short conversations, is necessary for multicast discovery,
and generally fits the discovery and divert scenarios
well. However, it will cause problems with large messages. TCP is good
for stable and long sessions, with a little bit of time
consumption during the session establishment stage. If messages
exceed a reasonable MTU, a TCP mode will be required in any case.
This question may be affected by the security discussion. </t>
<t>2. DTLS or TLS vs built-in security mechanism. For now, this
specification has chosen a PKI based built-in security mechanism
based on asymmetric cryptography. However, (D)TLS might be chosen as security solution
to avoid duplication of effort. It also allows essentially similar security for short
messages over UDP and longer ones over TCP. The implementation trade-offs are different.
The current approach requires expensive asymmetric cryptographic calculations
for every message. (D)TLS has startup overheads but cheaper crypto per message.
DTLS is less mature than TLS.
</t>
<t>The following open issues apply only if the current security model is retained:
<list style="symbols">
<t>2.1. For replay protection, GDNP currently requires every participant to have an
NTP-synchronized clock. Is this OK for low-end devices, and how does
it work during device bootstrapping?
We could take the Timestamp out of signature option, to become
an independent and OPTIONAL (or RECOMMENDED) option.</t>
<t>2.2. The Signature Option (<xref target="SignOption"/>) states that this option
could be any place in a message. Wouldn't it be better to specify a position
(such as the end)? That would be much simpler to implement. </t>
</list></t>
<t>3. DoS Attack Protection needs work.</t>
<t>4. Should we consider preferring a text-based approach to
discovery (after the initial discovery needed for bootstrapping)? This topic is
deferred for now, but the following considerations apply:
This could be a complementary mechanism for multicast based discovery, especially
for a very large autonomic network. Centralized registration could be automatically
deployed incrementally. At the very first stage, the repository could be empty;
then it could be filled in by the objectives discovered by different devices (for example
using Dynamic DNS Update). The more records are stored in the repository, the less the
multicast-based discovery is needed. However, if we adopt such a mechanism, there would be
challenges: stateful solution, and security. </t> -->
<t>5. Need to expand description of the minimum requirements for
the specification of an individual discovery, synchronization or
negotiation objective. </t>
<t>6. Use case and protocol walkthrough. A description of how a node starts up,
performs discovery, and conducts negotiation and synchronisation for a sample
use case would help readers to understand the applicability of this specification.
Maybe it should be an artificial use case or maybe a simple real one.
However, the authors have not yet decided whether to have a separate document or
have it in this document. </t>
<t>7. Cross-check against other ANIMA WG documents for consistency and gaps.</t>
</list></t>
</section>
<section anchor="security" title="Security Considerations">
<t>It is obvious that a successful attack on negotiation-enabled nodes
would be extremely harmful, as such nodes might end up with a completely
undesirable configuration that would also adversely affect their peers.
GDNP nodes and messages therefore require full protection. </t>
<t>- Authentication<list style="hanging">
<t>A cryptographically authenticated identity for each device is
needed in an autonomic network. It is not safe to assume that a
large network is physically secured against interference or that all
personnel are trustworthy. Each autonomic device MUST be capable
of proving its identity and authenticating its messages. GDNP
relies on a separate certificate-based security mechanism to support
authentication, data integrity protection, and anti-replay protection.</t>
<t>Since GDNP is intended to be deployed in a single administrative
domain operating its own trust anchor and CA, there is
no need for a trusted public third party. In a network requiring
"air gap" security, such a dependency would be unacceptable. </t>
</list></t>
<t>- Privacy and confidentiality<list style="hanging">
<t>Generally speaking, no personal information is expected to be
involved in the negotiation protocol, so there should be no direct
impact on personal privacy. Nevertheless, traffic flow paths, VPNs,
etc. could be negotiated, which could be of interest for traffic
analysis. Also, operators generally want to conceal details of their
network topology and traffic density from outsiders. Therefore,
since insider attacks cannot be excluded in a large
network, the security mechanism for the protocol MUST
provide message confidentiality.</t>
</list></t>
<t>- DoS Attack Protection<list style="hanging">
<t>GDNP discovery partly relies on insecure link-local multicast. Since
routers participating in GDNP sometimes relay discovery messages from one link
to another, this could be a vector for denial of service attacks. Relevant
mitigations are specified in <xref target="discmech"/>. Additionally,
it is of great importance that firewalls prevent any GDNP messages
from entering the domain from an untrusted source. </t>
</list></t>
<t>- Security during bootstrap and discovery<list style="hanging">
<t>A node cannot authenticate GDNP traffic from other nodes until it
has identified the trust anchor and can validate certificates for other
nodes. Also, until it has succesfully enrolled
<xref target="I-D.pritikin-anima-bootstrapping-keyinfra"/> it cannot
assume that other nodes are able to authenticate its own traffic.
Therefore, GDNP discovery during the bootstrap phase for a new device
will inevitably be insecure and GDNP synchronization and negotiation
will be impossible until enrollment is complete.</t>
</list></t>
</section>
<section anchor="iana" title="IANA Considerations">
<t><xref target="Constants"/> defines the following link-local multicast
addresses, which have been assigned by IANA for use by GDNP:</t>
<t><list style="hanging">
<t hangText="ALL_GDNP_NEIGHBOR multicast address">(IPv6): (TBD1).
Assigned in the IPv6 Link-Local Scope Multicast Addresses registry.</t>
<t hangText="ALL_GDNP_NEIGHBOR multicast address">(IPv4): (TBD2).
Assigned in the IPv4 Multicast Local Network Control Block.
<vspace blankLines="1"/>
(Note in draft: alternatively, we could use 224.0.0.1, currently
defined as All Systems on this Subnet.)</t>
</list></t>
<t><xref target="Constants"/> defines the following UDP and TCP port,
which has been assigned by IANA for use by GDNP:</t>
<t><list style="hanging">
<t hangText="GDNP Listen Port:">(TBD3)</t>
</list></t>
<t>This document defines the General Discovery and Negotiation
Protocol (GDNP). The IANA is requested to create a GDNP registry within the
unused portion of the DNCP registry <xref target="I-D.ietf-homenet-dncp"/>.
The IANA is also requested to add two new registry tables to the newly-created
GDNP registry. The two tables are the GDNP Messages table and GDNP
Options table.</t>
<t>Initial values for these registries are given below. Future
assignments are to be made through Standards Action or Specification
Required <xref target="RFC5226"/>. Assignments for each registry
consist of a type code value, a name and a document where the usage is
defined.</t>
<t>Note to the RFC Editor: In the following tables and in the body of this
document, the values G0, G1, etc., should be replaced by the assigned values.</t>
<t>GDNP Messages table. The values in this table are 16-bit unsigned
integers. The following initial values are assigned in <xref target="GDNPMessages"/> in this document:</t>
<t><figure>
<artwork><![CDATA[ Type | Name | RFCs
---------+-----------------------------+------------
G0 |Reserved | this document
G1 |Discovery Message | this document
G2 |Response Message | this document
G3 |Request Message | this document
G4 |Negotiation Message | this document
G5 |Negotiation-ending Message | this document
G6 |Confirm-waiting Message | this document
G7~31 |reserved for future messages |
]]></artwork>
</figure>
</t><t>GDNP Options table. The values in this table are 16-bit
unsigned integers. The following initial values are assigned in <xref target="GDNPOptions"/> and <xref target="ObjOption"> </xref> in
this document:</t>
<t><figure>
<artwork><![CDATA[ Type | Name | RFCs
---------+-----------------------------+------------
G32 |Divert Option | this document
G33 |Accept Option | this document
G34 |Decline Option | this document
G35 |Waiting Time Option | this document
G36 |Device Identity Option | this document
G37 |Device IPv4 Address Option | this document
G38 |Device IPv6 Address Option | this document
G39 |Device FQDN Option | this document
G40~63 |Reserved for future GDNP |
|General Options |
G64~127 |Reserved for future GDNP |
|Objective Options |
G128~159|Vendor Specific Options | this document
G160~175|Reserved for future use |
G176~191|Experimental Options | this document
G192~???|Reserved for future use |
]]></artwork>
</figure>
</t>
<!-- <t>The IANA is also requested to create two new registry tables
in the GDNP Parameters registry. The two tables are the Hash Algorithm
for GDNP table and the Signature Algorithm for GDNP table.</t>
<t>Initial values for these registries are given below. Future
assignments are to be made through Standards Action or Specification
Required <xref target="RFC5226"/>. Assignments for each registry
consist of a name, a value and a document where the algorithm is
defined.</t>
<t>Hash Algorithm for GDNP. The values in this table are 16-bit unsigned
integers. The following initial values are assigned for Hash Algorithm
for GDNP in this document:</t>
<t><figure>
<artwork><![CDATA[ Name | Value | RFCs
- - - - - - - - - - -+- - - - - -+- - - - - -
Reserved | 0x0000 | this document
SHA-1 | 0x0001 | this document
SHA-256 | 0x0002 | this document
]]></artwork>
</figure>
</t><t>Signature Algorithm for GDNP. The values in this table are
16-bit unsigned integers. The following initial values are assigned for
Signature Algorithm for GDNP in this document:</t>
<t><figure>
<artwork><![CDATA[ Name | Value | RFCs
- - - - - - - - - - -+- - - - - -+- - - - - -
Reserved | 0x0000 | this document
RSASSA-PKCS1-v1_5 | 0x0001 | this document
]]></artwork>
</figure></t> -->
</section>
<section anchor="ack" title="Acknowledgements">
<t>A major contribution to the original version of this document was made by Sheng Jiang.</t>
<t>Valuable comments were received from
Michael Behringer,
Zongpeng Du,
Yu Fu,
Zhenbin Li,
Dimitri Papadimitriou,
Michael Richardson,
Markus Stenberg,
Rene Struik,
Dacheng Zhang,
and other participants in the NMRG research group
and the ANIMA working group.</t>
<t>This document was produced using the xml2rfc tool <xref target="RFC2629"/>.</t>
</section>
<section anchor="changes" title="Change log [RFC Editor: Please remove]">
<t>draft-carpenter-anima-discovery-negotiation-protocol-03, 2015-04-20:
<vspace blankLines="1"/>
Removed intrinsic security, required external security
<vspace blankLines="1"/>
Format changes to allow ADNCP co-existence
<vspace blankLines="1"/>
Recognized DNS-SD as alternative discovery method
<vspace blankLines="1"/>
Editorial improvements</t>
<t>draft-carpenter-anima-discovery-negotiation-protocol-02, 2015-02-19:
<vspace blankLines="1"/>
Tuned requirements to clarify scope,
<vspace blankLines="1"/>
Clarified relationship between types of objective,
<vspace blankLines="1"/>
Clarified that objectives may be simple values or complex data structures,
<vspace blankLines="1"/>
Improved description of objective options,
<vspace blankLines="1"/>
Added loop-avoidance mechanisms (loop count and default timeout,
limitations on discovery relaying and on unsolicited responses),
<vspace blankLines="1"/>
Allow multiple discovery objectives in one response,
<vspace blankLines="1"/>
Provided for missing or multiple discovery responses,
<vspace blankLines="1"/>
Indicated how modes such as "dry run" should be supported,
<vspace blankLines="1"/>
Minor editorial and technical corrections and clarifications,
<vspace blankLines="1"/>
Reorganized future work list. </t>
<t>draft-carpenter-anima-discovery-negotiation-protocol-01, restructured the logical flow of the document,
updated to describe synchronization completely, add unsolicited responses, numerous corrections
and clarifications, expanded future work list, 2015-01-06. </t>
<t>draft-carpenter-anima-discovery-negotiation-protocol-00, combination
of draft-jiang-config-negotiation-ps-03 and
draft-jiang-config-negotiation-protocol-02, 2014-10-08.</t>
</section>
</middle>
<back>
<references title="Normative References">
<?rfc include='reference.RFC.2119'?>
<?rfc include='reference.RFC.5280'?>
<?rfc include='reference.RFC.4086'?>
<?rfc include='reference.RFC.5246'?>
<?rfc include='reference.RFC.6347'?>
</references>
<references title="Informative References">
<?rfc include='reference.RFC.2629'?>
<?rfc include='reference.RFC.5226'?>
<?rfc include='reference.RFC.6733'?>
<?rfc include='reference.RFC.2865'?>
<?rfc include='reference.RFC.4861'?>
<?rfc include='reference.RFC.5971'?>
<?rfc include='reference.RFC.6241'?>
<?rfc include='reference.RFC.3209'?>
<?rfc include='reference.RFC.2205'?>
<?rfc include='reference.RFC.3416'?>
<?rfc include='reference.RFC.3315'?>
<?rfc include='reference.RFC.6887'?>
<?rfc include='reference.RFC.6762'?>
<?rfc include='reference.RFC.6763'?>
<?rfc include='reference.RFC.2608'?>
<?rfc include='reference.I-D.ietf-homenet-hncp'?>
<?rfc include='reference.I-D.stenberg-anima-adncp'?>
<?rfc include='reference.I-D.ietf-homenet-dncp'?>
<?rfc include='reference.I-D.ietf-netconf-restconf'?>
<?rfc include='reference.I-D.chaparadza-intarea-igcp'?>
<!-- <?rfc include='reference.I-D.behringer-anima-reference-model'?> -->
<?rfc include='reference.I-D.pritikin-anima-bootstrapping-keyinfra'?>
<?rfc include='reference.I-D.behringer-anima-autonomic-control-plane'?>
<?rfc include='reference.I-D.irtf-nmrg-an-gap-analysis'?>
<?rfc include='reference.I-D.irtf-nmrg-autonomic-network-definitions'?>
<?rfc include='reference.I-D.eckert-anima-stable-connectivity'?>
<?rfc include='reference.I-D.liang-iana-pen'?>
<?rfc include='reference.I-D.ietf-dnssd-requirements'?>
</references>
<section anchor="current" title="Capability Analysis of Current Protocols">
<t>This appendix discusses various existing protocols with properties
related to the above negotiation and synchronisation requirements. The
purpose is to evaluate whether any existing protocol, or a simple
combination of existing protocols, can meet those requirements.</t>
<t>Numerous protocols include some form of discovery, but these all appear to be very
specific in their applicability. Service Location Protocol (SLP)
<xref target="RFC2608"/> provides service discovery for managed networks,
but requires configuration of its own servers. DNS-SD <xref target="RFC6763"/>
combined with mDNS <xref target="RFC6762"/> provides service discovery for
small networks with a single link layer. <xref target="I-D.ietf-dnssd-requirements"/>
aims to extend this to larger autonomous networks. However, both SLP and DNS-SD appear to
target primarily application layer services, not the layer 2 and 3 objectives
relevant to basic network configuration. Both SLP and DNS-SD are text-based protocols. </t>
<t>Routing protocols are mainly one-way information announcements. The
receiver makes independent decisions based on the received information
and there is no direct feedback information to the announcing peer. This
remains true even though the protocol is used in both directions between
peer routers; there is state synchronization, but no negotiation, and
each peer runs its route calculations independently.</t>
<t>Simple Network Management Protocol (SNMP) <xref target="RFC3416"/> uses
a command/response model not well suited for peer negotiation. Network Configuration
Protocol (NETCONF) <xref target="RFC6241"/> uses an RPC model that does allow positive or
negative responses from the target system, but this is still not
adequate for negotiation.</t>
<t>There are various existing protocols that have elementary negotiation
abilities, such as Dynamic Host Configuration Protocol for IPv6 (DHCPv6)
<xref target="RFC3315"/>, Neighbor Discovery (ND) <xref target="RFC4861"/>,
Port Control Protocol (PCP) <xref target="RFC6887"/>, Remote Authentication
Dial In User Service (RADIUS) <xref target="RFC2865"/>, Diameter <xref target="RFC6733"/>,
etc. Most of them are configuration or
management protocols. However, they either provide only a simple
request/response model in a master/slave context or very limited
negotiation abilities.</t>
<t>There are also signalling protocols with an element of negotiation.
For example Resource ReSerVation Protocol (RSVP) <xref target="RFC2205"/>
was designed for negotiating quality of service
parameters along the path of a unicast or multicast flow. RSVP is a very
specialised protocol aimed at end-to-end flows. However, it has some
flexibility, having been extended for MPLS label distribution <xref target="RFC3209"/>.
A more generic design is General Internet
Signalling Transport (GIST) <xref target="RFC5971"/>, but it is
complex, tries to solve many problems, and is also aimed at per-flow
signalling across many hops rather than at device-to-device signalling.
However, we cannot completely exclude extended RSVP or GIST as a
synchronization and negotiation protocol. They do not appear to be
directly useable for peer discovery.</t>
<t>We now consider two protocols that are works in progress at the time
of this writing. Firstly, RESTCONF <xref target="I-D.ietf-netconf-restconf"/> is a protocol intended to
convey NETCONF information expressed in the YANG language via HTTP,
including the ability to transit HTML intermediaries. While this is a
powerful approach in the context of centralised configuration of a
complex network, it is not well adapted to efficient interactive
negotiation between peer devices, especially simple ones that are
unlikely to include YANG processing already.</t>
<t>Secondly, we consider Distributed Node Consensus Protocol (DNCP)
<xref target="I-D.ietf-homenet-dncp"/>. This is defined as a generic form
of state synchronization protocol, with a proposed usage profile being the
Home Networking Control Protocol (HNCP) <xref target="I-D.ietf-homenet-hncp"/>
for configuring Homenet routers. A specific application of DNCP for autonomic
networking was proposed in <xref target="I-D.stenberg-anima-adncp"/>.
</t><t>
Specific features of DNCP include:
<list style="symbols">
<t>Every participating node has a unique node identifier.</t>
<t>DNCP messages are encoded as a sequence of TLV objects, sent over
unicast UDP or TCP, with or without (D)TLS security.</t>
<t>Multicast is used only for discovery of DNCP neighbors
when lower security is acceptable.</t>
<t>Synchronization of state is maintained by a flooding process using the Trickle algorithm.
There is no bilateral synchronization or negotiation capability.</t>
<t>The HNCP profile of DNCP is designed to operate between directly connected neighbors
on a shared link using UDP and link-local IPv6 addresses.</t>
</list>
Clearly DNCP does not meet the needs of a general
negotiation protocol, especially in its HNCP profile due to the limitation to link-local
messages and its strict dependency on IPv6. However, at the minimum it is a
very interesting test case for this style of interaction between devices
without needing a central authority, and it is a proven method of network-wide state
synchronization by flooding.</t>
<t>A proposal was made some years ago for an IP based Generic Control Protocol
(IGCP) <xref target="I-D.chaparadza-intarea-igcp"/>. This was aimed
at information exchange and negotiation but not directly at peer
discovery. However, it has many points in common with the present work.</t>
<t>None of the above solutions appears to completely meet the needs of
generic discovery, state synchronization and negotiation in a single solution.
Neither is there an obvious combination of protocols that does so.
Therefore, this document proposes the design of a
protocol that does meet those needs. However, this proposal needs to be
compared with alternatives such as extension and adaptation of GIST or
DNCP, or combination with IGCP.</t>
</section>
<!-- current -->
</back>
</rfc>
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