One document matched: draft-carpenter-anima-gdn-protocol-01.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="6" month="January" 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 mutual configurations 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 as possible
alternatives.</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 effected as a special case of negotiation.
<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 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 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. </t>
<t>It is understood that in realistic deployments, not all devices will
support GDNP. 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. In some cases, when a
new user session starts up, the device concerned 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 or configure. 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 discover the appropriate
trust anchor, i.e. the appropriate PKI authority. Logically, this is just a
specific case of discovery. However, it might be a special case requiring its own
solution. In any case, the trust anchor must be discovered before the security
environment is completely established. This question requires further study and
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"/>.</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 iteratively 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. More information, such as latency,
congestion, capacity, and particularly unused capacity, would be
helpful to get better path selection and utilization rate. Also,
autonomic networks need to be able to manage many more dimensions,
such as security settings, power saving, load balancing, etc. A basic
requirement for the protocol is therefore the ability to represent,
discover, synchronize and negotiate almost any kind of network
parameter.</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 being installed 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 being installed 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. Stated differently, the protocol must be capable of supporting
a "dry run" of a changed configuration before actually installing the
change.</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. The protocol needs to be capable of
detecting unexpected events such a negotiation counterpart failing, so
that all devices concerned can initiate a recovery process.</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 to 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 should be IP version independent.
In other words, it should be able to run over IPv6 and IPv4. Its
messages and general options should be neutral with respect to the IP
version. 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, 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.</t>
<t>Dependencies: 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 among negotiation or synchronization
procedures. Thus, there need to be clear boundaries and convergence mechanisms for these
negotiation dependencies. 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.</t>
</section>
</section>
<!-- reqts -->
<section anchor="Overview" title="GDNP Protocol Overview">
<!--1-->
<section anchor="terms" title="Terminology">
<!--2-->
<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>The following 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 exchanged but the devices do not request
their peers to change parameter settings. All other definitions
apply to both negotiation and synchronization.</t>
<t>Discovery Objective: a specific network functionality, network
element role or type of autonomic service agent (TBD) which the discovery
initiator intends to discover. One device may support multiple discovery
objectives. 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>
<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 Objective: specific technical content, which needs
to be synchronized among a number of devices. It is
naturally based on a specific service or function or action. It
could be a logical, numeric, or string value or a more complex data
structure.</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 Objective: specific technical content, which needs
to be decided in coordination with another network device. It is
naturally based on a specific service or function or action. It
could be a logical, numeric, or string value or a more complex data
structure.</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">
<!--2-->
<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 elementary version has been 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.<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.
<vspace blankLines="1"/></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
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"/>
Synchronization across a number of nodes is not a new problem and
the Trickle model that is already known to be effective and efficient is
adopted.<vspace blankLines="1"/></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>
<!--2-->
<section title="GDNP Protocol Basic Properties and Mechanisms">
<!--2-->
<section anchor="discmech" title="Discovery Mechanism and Procedures">
<!--3-->
<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 objective could be network functionalities,
role-based network elements or service agents (TBD). 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 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 to the ALL_GDNP_NEIGHBOR multicast
address (<xref target="Constants"/>). Every network
device that supports the GDNP always listens to a well-known
transport 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>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.</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.
Togther with the caching mechanism, this 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.</t>
</list></t>
</list></t>
</section>
<!--3-->
<section title="Certificate-based Security Mechanism">
<!--3-->
<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">
<!--4-->
<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>
<!--4-->
<section title="Message validation on reception">
<!--4-->
<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>
<!--4-->
<section anchor="TimeCheck" title="TimeStamp checking">
<!--4-->
<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>
<!--4-->
</section>
<!--3-->
<section anchor="negproc" title="Negotiation Procedures">
<!--3-->
<t>A negotiation initiator sends a negotiation request to
counterpart devices, which may be different according to different
negotiation objectives. 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 additionally request the negotiation
counterpart to make a matching configuration in order to set up a
successful communication with it. It may request a certain
simulation or forecast result by sending some dry run conditions.
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.</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 one or more Negotiation
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 Negotiation message for rapid processing, if the discovery
objective 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>
<!--3-->
<section anchor="synchproc" title="Synchronization Procedure">
<!--3-->
<t>A synchronization initiator sends a synchronization request to
counterpart devices, which may be different according to different
synchronization objectives. The counterpart responds with a Response
message containing the current value(s) of the requested synchronization
objective. No further messages are needed, but otherwise the procedure
operates as a subset of the negotiation procedure. If no Response
message is received, the synchronization request MAY be repeated
after a suitable timeout.</t>
<t>A synchronization responder MAY send an unsolicited Response message containing
a synchronization objective, if and only if the specification of this objective
permits it. This MAY be sent as a multicast message to the ALL_GDNP_NEIGHBOR multicast
address (<xref target="Constants"/>). In this case the Trickle algorithm
<xref target="RFC6206"/> MUST be used to avoid excessive multicast
traffic. The parameters Imin, Imax and k of the Trickle algorithm
will be specified as part of the specification of the synchronization
objective concerned. </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. 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>
<!--3-->
</section>
<!--2-->
<section anchor="Constants" title="GDNP Constants">
<!--2-->
<t><list style="symbols">
<t>ALL_GDNP_NEIGHBOR (TBD1)<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 port that
every GDNP-enabled network device always listens to.</t>
</list></t>
</section>
<!--2-->
<section anchor="DeviceID" title="Device Identifier and Certificate Tag">
<!--2-->
<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>
<!--2-->
<section anchor="SessionID" title="Session Identifier (Session ID)">
<!--2-->
<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>
<!--2-->
<section anchor="GDNPMessages" title="GDNP Messages">
<!--2-->
<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">
<!--3-->
<t>All GDNP messages share an identical fixed format header and a
variable format area for options. Every Message carries the Device
Certificate Tag of its sender and a Session ID. Options are
presented serially in the options field, with no padding between the
options. Options are byte-aligned.</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 | Session ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Device Certificate Tag |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Options (variable length) |
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure></t>
<t><list style="hanging">
<t hangText="MESSAGE_TYPE:"> Identifies the GDNP message type. 8-bit.
</t>
<t hangText="Session ID:"> Identifies this negotiation 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 = 1):</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 a discovery objective
option (<xref target="DisobjOption"/>).
</t><t>
A DISCOVERY message MAY include one or more negotiation
objective option(s) (<xref target="ObjOption"/>) to indicate
to the discovery objective that it could directly return to
the discovery initiatior with a Negotiation message for
rapid processing, if the discovery objective could act as
the corresponding negotiation counterpart, and similarly
for synchronization.
</t>
</section>
<section anchor="ResponseMessage" title="Response Message">
<t>RESPONSE (MESSAGE_TYPE = 2):</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.
</t><t>
If the response contains synchronization data, this will
be in the form of a GDNP Option for the specific
synchronization objective.</t>
</section>
<!--3-->
<section anchor="RequestMessage" title="Request Message">
<!--3-->
<t>REQUEST (MESSAGE_TYPE = 3):</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>
</section>
<!--3-->
<section anchor="NegotiationMessage" title="Negotiation Message">
<!--3-->
<t>NEGOTIATION (MESSAGE_TYPE = 4):</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>
</section>
<!--3-->
<section anchor="NegotiationEndingMessage" title="Negotiation-ending Message">
<!--3-->
<t>NEGOTIATION-ENDING (MESSAGE_TYPE = 5):</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>
<!--3-->
<section anchor="ConfirmWaitingMessage" title="Confirm-waiting Message">
<!--3-->
<t>CONFIRM-WAITING (MESSAGE_TYPE = 6):</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>
<!--3-->
</section>
<!--2-->
<section anchor="GDNPOptions" title="GDNP General Options">
<!--2-->
<t>This section defines the GDNP general option for the negotiation
and synchronization protocol signalling. Option types 10~63 are reserved for GDNP general
options defined in the future.</t>
<section title="Format of GDNP Options">
<!--3-->
<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>
<!--3-->
<section anchor="DivertOption" title="Divert Option">
<!--3-->
<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 (1).
</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>
<!--3-->
<section anchor="AcceptOption" title="Accept Option">
<!--3-->
<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 (2)
</t>
<t hangText="Option-len:"> 0
</t></list></t>
</section>
<!--3-->
<section anchor="DeclineOption" title="Decline Option">
<!--3-->
<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 (3)
</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 Response 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>
<!--3-->
<section anchor="WaitingTimeOption" title="Waiting Time Option ">
<!--3-->
<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.</t>
<t>The counterpart SHOULD send a Response message or another
Confirm-waiting message before the current waiting time expires. If
not, the initiator SHOULD 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 (4)
</t>
<t hangText="Option-len:"> 4, in octets
</t>
<t hangText="Time:"> Time in milliseconds
</t></list></t>
</section>
<!--3-->
<section anchor="CertOption" title="Certificate Option">
<!--3-->
<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>
<!--3-->
<section anchor="SignOption" title="Signature Option">
<!--3-->
<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>
<!--3-->
<section anchor="LocatorOption" title="Locator Options">
<!--3-->
<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>
<section title="Locator IPv4 address option">
<!--4-->
<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 (7)
</t>
<t hangText="Option-len:"> 4, in octets
</t>
<t hangText="IPv4-Address:"> The IPv4 address locator of the device/interface
</t></list></t>
</section>
<!--4-->
<section title="Locator IPv6 address option">
<!--4-->
<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 (8)
</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>
<!--4-->
<section title="Locator FQDN option">
<!--4-->
<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 (9)
</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>
</section>
<!--4-->
</section>
<!--3-->
<!---->
</section>
<!--2-->
<section anchor="DisobjOption" title="Discovery Objective Option">
<t>The discovery objective option is to express the discovery
objectives that the initiating node wants to discover
and to confirm them in a Response message.</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_DISOBJ | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Expression of Discovery Objectives (TBD) |
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure></t>
<t><list style="hanging">
<t hangText="Option-code:"> OPTION_DISOBJ (TBD)
</t>
<t hangText="Option-len:"> The total length in octets
</t>
<t hangText="Expression of Discovery Objectives (TBD):">
This field is to express the discovery objectives
that the initiating node wants to discover. It might
be network functionality, role-based network element
or service agent.
</t></list></t>
</section>
<!--2-->
<section anchor="ObjOption" title="Negotiation and Synchronization Objective Options and Considerations">
<!--2-->
<t>Negotiation and Synchronization Objective Options MUST be assigned
an option type greater than 64 in the GDNP option table.</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.
</t>
<t>For most scenarios, there SHOULD be initial values in the
negotiation requests. Consequently, the Negotiation Objective options SHOULD
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 title="Organizing of GDNP Options">
<!--3-->
<t>Naturally, a negotiation objective, which is based on a specific
service or function or action, SHOULD be organized as a single GDNP
option. It is NOT RECOMMENDED to organize multiple negotiation
objectives into a single option.</t>
<t>A negotiation objective may have multiple parameters. Parameters
can be categorized into two class: the obligatory ones presented as
fixed fields; and the optional ones presented in TLV sub-options. 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>
<!--3-->
<section title="Vendor Specific Options ">
<!--3-->
<t>Option codes 128~159 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.</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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Private Enterprise Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Contents |
. (variable length) .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure></t>
<t><list style="hanging">
<t hangText="Option-code:"> OPTION_vendor (128~159)
</t>
<t hangText="Option-len:"> Length of PEN plus option contents in octets
</t></list></t>
</section>
<!--3-->
<section title="Experimental Options">
<!--3-->
<t>Option code 176~191 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>
<!--3-->
</section>
<!--2-->
<section title="Items for Future Work">
<!--2-->
<t>There are various design questions that are worthy of more work
in the near future, as listed below:</t>
<t><list style="symbols">
<t>UDP vs TCP: For now, this specification has chosen UDP as
message transport mechanism. However, this is not closed yet. UDP
is good for short conversations, fitting the discovery and divert scenarios
well. However, it may have issues with large packets. 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 may be necessary.</t>
<t>Message encryption: should GDNP messages be (optionally)
encrypted as well as signed, to protect against internal
eavesdropping or monitoring within the network?</t>
<t>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. </t>
<t>Should discuss lifetime of discovery cache, and what to do when discovery fails
(timeout and repeat?).</t>
<t>Timeout for lost Negotiation Ending and other messages to be added.</t>
<t>We mention convergence mechanisms and say "Also some mechanisms are needed to
avoid loop dependencies." These issues need more work. </t>
<t>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>Would use of MDNS have any impact on the Locator FQDN option?</t>
<t>Need to add a section describing the minimum requirements for
the specification of an individual discovery, synchronization or
negotiation objective. Maybe a formal information model is needed.</t>
<t>Is it reasonable to consider that a Discovery Objective is really
just a set of specific Negotiation and/or Synchronization Objectives? In other words,
if a GDNP node supports Negotiation and/or Synchronization Objectives A, B and C,
then its corresponding Discovery Objective is a shorthand for "A+B+C". </t>
<t>Would a DISCOVERY(ANY) mechanism be useful during bootstrapping, i.e. used by
all GDNP-capable routers to find all their neighbours that support any GDNP
discovery objective?.</t>
<t>Would it be reasonable to allow an unsolicited Response message with
Discovery Objective content, to speed up discovery during bootstrapping? </t>
<t>Is there a risk that the relaying of discovery messages (<xref target="discmech"/>)
will lead to loops or multicast storms? At least we should consider throttling
discovery relays to a maximum rate. Or is there a better method for zeroconf discovery
with no predefined hierarchy?</t>
<t>Should we consider a distributed or centralised DNS-like approach to
discovery (after the initial discovery needed for bootstrapping)?</t>
<t>Need to discuss automatic recovery mechanism as required by <xref target="synchreq"/>
and management monitoring, alerts and intervention in general.</t>
<t>The Decline Option (<xref target="DeclineOption"/>) includes a note that
a counterpart could use a Response message to indicate "Decline but try again".
That seems strange - why not use a Negotiation message for this case?</t>
<t>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>
<t>DoS Attack Protection needs work.</t>
<t>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>We currently assume that there is only one counterpart for each
discovery action. If this is false or one negotiation request
receives multiple different responses, how does the initiator
choose between them? Could it split them into multiple follow-up
negotiations?</t>
<t>Alternatives to TLV format. It may be useful to provide a
generic method of carrying negotiation objectives in a high-level
format such as YANG or XML schema. It may also be useful to
provide a generic method of carrying existing configuration
information such as DHCP(v6) or IPv6 RA messages. These features
could be provided by encapsulating such messages in their own
TLVs, but large messages would definitely need a TCP mode instead of UDP.</t>
</list></t>
</section>
<!--2-->
</section>
<!--1-->
<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 should be capable
of proving its identity and authenticating its messages. GDNP
proposes a certificate-based security mechanism to provide
authentication and data integrity protection.</t>
<t>The timestamp mechanism provides an anti-replay function.</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.</t>
</list></t>
<t>- Privacy<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. may be negotiated, which could be of interest for traffic
analysis. Also, carriers generally want to conceal details of their
network topology and traffic density from outsiders. Therefore,
since insider attacks cannot be prevented in a large carrier
network, the security mechanism for the negotiation protocol needs
to provide message confidentiality.</t>
</list></t>
<t>- DoS Attack Protection<list style="hanging">
<t>TBD.</t>
</list></t>
</section>
<section anchor="iana" title="IANA Considerations">
<t><xref target="Constants"/> defines the following 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)</t>
<t hangText="ALL_GDNP_NEIGHBOR multicast address">(IPv4): (TBD2)</t>
</list></t>
<t><xref target="Constants"/> defines the following UDP 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 defined a new General Discovery and Negotiation
Protocol. The IANA is requested to create a new GDNP registry. 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>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
---------+-----------------------------+------------
0 |Reserved | this document
1 |Discovery | this document
2 |Response | this document
3 |Request Message | this document
4 |Negotiation Message | this document
5 |Negotiation-end Message | this document
6 |Confirm-waiting Message | this document
]]></artwork>
</figure>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
---------+-----------------------------+------------
0 |Reserved | this document
1 |Divert Option | this document
2 |Accept Option | this document
3 |Decline Option | this document
4 |Waiting Time Option | this document
5 |Certificate Option | this document
6 |Signature Option | this document
7 |Device IPv4 Address Option | this document
8 |Device IPv6 Address Option | this document
9 |Device FQDN Option | this document
10~63 |Reserved for future GDNP | this document
|General Options |
128~159 |Vendor Specific Options | this document
176~191 |Experimental Options | this document
]]></artwork>
</figure>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>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
Zhenbin Li,
Dimitri Papadimitriou,
Michael Richardson,
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-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.6206'?>
<?rfc include='reference.RFC.3174'?>
</references>
<references title="Informative References">
<?rfc include='reference.RFC.2629'?>
<?rfc include='reference.RFC.5226'?>
<?rfc include='reference.RFC.4270'?>
<?rfc include='reference.RFC.5905'?>
<?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.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 section 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. </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 HomeNet Control Protocol (HNCP) <xref target="I-D.ietf-homenet-hncp"/>. This is defined as "a minimalist
state synchronization protocol for Homenet routers."
</t><t>NOTE: HNCP is under revision at the time of this
writing, so the following comments will soon be out of date.</t><t>
Specific features
are: <list style="symbols">
<t>Every participating node has a unique node identifier.</t>
<t>"HNCP is designed to operate between directly connected neighbors
on a shared link using link-local IPv6 addresses."</t>
<t>Currency of state is maintained by spontaneous link-local
multicast messages.</t>
<t>HNCP discovers and tracks link-local neighbours.</t>
<t>HNCP messages are encoded as a sequence of TLV objects, sent over
UDP.</t>
<t>Authentication depends on a signature TLV (assuming public keys
are associated with node identifiers).</t>
<t>The functionality covered initially includes: site border
discovery, prefix assignment, DNS namespace discovery, and routing
protocol selection.</t>
</list> Clearly HNCP does not completely meet the needs of a general
negotiation protocol, especially due to its limitation to link-local
messages and its strict dependency on IPv6, but at the minimum it is a
very interesting test case for this style of interaction between devices
without needing a central authority.</t>
<t>A proposal has been made for an IP based Generic Control Protocol
(IGCP) <xref target="I-D.chaparadza-intarea-igcp"/>. This is 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
discovery, state synchronization and negotiation in the general case.
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
confronted with alternatives such as extension and adaptation of GIST or
HNCP, or combination with IGCP.</t>
</section>
<!-- current -->
</back>
</rfc>
| PAFTECH AB 2003-2026 | 2026-04-22 12:33:50 |