| Network Working Group | B. Carpenter |
| Internet-Draft | Univ. of Auckland |
| Intended status: Standards Track | B. Liu |
| Expires: December 22, 2015 | Huawei Technologies Co., Ltd |
| June 20, 2015 |
A Generic Discovery and Negotiation Protocol for Autonomic Networking
draft-carpenter-anima-gdn-protocol-04
This document establishes requirements for a signaling protocol that enables autonomic devices and autonomic service agents to dynamically discover peers, 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.
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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 [RFC7575] and [RFC7576]. A reference model for autonomic networking is given in [I-D.behringer-anima-reference-model]. In order to fulfil autonomy, devices that embody autonomic service agents have specific signaling requirements. In particular they need 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 non-autonomic network. The atomic unit of synchronization or negotiation is referred to as a technical objective, i.e, a configurable parameter or set of parameters (defined more precisely in Section 3.1).
Following this Introduction, Section 2 describes the requirements for 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. Section 3.2 describes a behavior model for a protocol intended to support discovery, synchronization and negotiation. The design of Generic Discovery and Negotiation Protocol (GDNP) in Section 3 of this document is mainly based on this behavior model. The relevant capabilities of various existing protocols are reviewed in Appendix A.
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 managed networks. However, when a device starts up with no pre-configuration, it has no knowledge of the topology. 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.
Because GDNP can be used to perform a decision process among distributed devices or between networks, it must run in a secure and strongly authenticated environment.
It is understood that in realistic deployments, not all devices will support GDNP. It is expected that some autonomic service agents will directly 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.
This section discusses the requirements for discovery, negotiation and synchronization capabilities. The primary user of the protocol is an autonomic service agent (ASA), so the requirements are mainly expressed as the features needed by an ASA. A single physical device might contain several ASAs, and a single ASA might manage several technical objectives.
1. ASAs may be designed to manage anything, as required in Section 2.2. A basic requirement is therefore that the protocol can represent and discover any kind of technical objective among arbitrary subsets of participating nodes.
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. The ASA(s) inside the device are in the same situation. In some cases, when a new application session starts up within a device, the device or ASA may again lack information about relevant peers. 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. The relevant peers 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. From this background we derive the next three requirements:
2. When an ASA first starts up, it has no knowledge of the specific network to which it is attached. Therefore the discovery process must be able to support any network scenario, assuming only that the device concerned is bootstrapped from factory condition.
3. When an ASA starts up, it must require no information about any peers in order to discover them.
4. If an ASA supports multiple technical objectives, relevant peers may be different for different discovery objectives, so discovery needs to be repeated to find counterparts for each objective. Thus, there must be a mechanism by which an ASA can separately discover peer ASAs for each of the technical objectives that it needs to manage, whenever necessary.
5. Following discovery, an ASA will normally perform negotiation or synchronization for the corresponding objectives. The design should allow for this by associating discovery, negotiation and synchronization objectives. It may provide an optional mechanism to combine discovery and negotiation/synchronization in a single call.
6. 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 peers 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 provide both on-link and off-link discovery of ASAs supporting specific technical objectives.
7. The discovery process should be flexible enough to allow for special cases, such as the following:
8. The discovery process must not generate excessive (multicast) traffic and must take account of sleeping nodes in the case of a resource-constrained network [RFC7228].
As background, consider the example of routing protocols, the closest approximation to autonomic networking already in widespread use. Routing protocols use a largely autonomic model based on distributed devices that communicate repeatedly with each other. The focus is reachability, so current routing protocols mainly 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 in order for the routing algorithm to converge. Thus, routing is mainly based on information synchronization between peers, rather than on bi-directional negotiation. Other information, such as latency, congestion, capacity, and particularly unused capacity, would be helpful to get better path selection and utilization rate, but is not normally used in distributed routing algorithms. Additionally, autonomic networks need to be able to manage many more dimensions, such as security settings, power saving, load balancing, etc. 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. In general, these parameters do not apply to all participating nodes, but only to a subset.
9. 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.
10. Negotiation is a request/response process that 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 these must be defined specifically for each use case, the protocol should have some general mechanisms in support of loop and deadlock prevention, such as hop count limits or timeouts.
11. Synchronization might concern small groups of nodes or very large groups. Different solutions might be needed at different scales.
12. To avoid "reinventing the wheel", the protocol should be able to carry the message formats used by existing configuration protocols (such as NETCONF/YANG) in cases where that is convenient.
13. 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 therefore follows that the protocol, as part of the Autonomic Networking Infrastructure, must be capable of running in any device that would otherwise need human intervention.
14. Human intervention in large networks is often replaced by use of a top-down network management system (NMS). It therefore follows that the protocol, as part of the Autonomic Networking Infrastructure, must be capable of running in any device that would otherwise be managed by an NMS, and that it can co-exist with an NMS, and with protocols such as SNMP and NETCONF.
15. Some features are expected to be implemented by individual ASAs, but the protocol must be general enough to allow them:
16. The protocol will 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.
17. It should be convenient for ASA designers to define new technical objectives and for programmers to express them, without excessive impact on run-time efficiency and footprint. The classes of device in which the protocol might run is discussed in [I-D.behringer-anima-reference-model].
18. The protocol should be extensible in case the initially defined discovery, synchronization and negotiation mechanisms prove to be insufficient.
19. 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.
20. The protocol must be able to access off-link counterparts via routable addresses, i.e., must not be restricted to link-local operation.
21. It must also be possible for an external discovery mechanism to be used, if appropriate for a given technical objective. In other words, GDNP discovery must not be a prerequisite for GDNP negotiation or synchronization; the prerequisite is discovering a peer's locator by any method.
22. ASAs and the signaling protocol engine need to run asynchronously when wait states occur.
23. Intent: There must be provision for general Intent rules to be applied by all devices in the network (e.g., security rules, prefix length, resource sharing rules). However, Intent distribution might not use the signaling protocol itself, but its design should not exclude such use.
24. 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 might not use the signaling protocol itself, but its design should not exclude such use.
25. The protocol needs to be fully secured against forged messages and man-in-the middle attacks, and secured as much 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.
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 [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 [RFC2119] key words.
This document uses terminology defined in [RFC7575].
The following additional terms are used throughout this document:
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.
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 Appendix A might be an option. This whole specification is subject to change as a result.
The protocol SHOULD run within a secure Autonomic Control Plane (ACP) [I-D.behringer-anima-autonomic-control-plane]. The procedure for establishing the ACP MUST provide a flag indicating to GDNP that the ACP has been established.
If there is no ACP, the protocol MUST use TLS [RFC5246] or DTLS [RFC6347] for all messages, based on a local Public Key Infrastructure (PKI) [RFC5280] managed within the autonomic network itself.
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., [I-D.pritikin-anima-bootstrapping-keyinfra], it might be impossible to secure certain messages. Such messages MUST be limited to the strictly necessary minimum.
The protocol is capable of running over UDP or TCP, except for link-local multicast discovery messages, which can only run over UDP and MUST NOT be fragmented, and therefore cannot exceed the link MTU size.
When running within a secure ACP, UDP SHOULD be used for messages not exceeding the minimum IPv6 path MTU, and TCP MUST be used for longer messages. In other words, IPv6 fragmentation is avoided. If a node receives a UDP message but the reply is too long, it MUST open a TCP connection to the peer for the reply.
When running without an ACP, TLS MUST be supported and used by default, except for multicast discovery messages. DTLS MAY be supported as an alternative but the details are out of scope for this document.
For all transport protocols, the GDNP protocol listens to the GDNP Listen Port (Section 3.4).
A negotiation initiator sends a negotiation request to a counterpart ASA, including a specific negotiation objective. 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.
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 ASAs.
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.
A negotiation procedure concerns one objective and one counterpart. Both the initiator and the counterpart may take part in simultaneous negotiations with various other ASAs, 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.
Rapid Mode (Discovery/Negotiation linkage)
A synchronization initiator sends a synchronization request to a counterpart, 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.
In the case just described, the message exchange is unicast and concerns only one synchronization objective. For large groups of nodes requiring the same data, synchronization flooding is available. For this, 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 is sent as a multicast message to the ALL_GDNP_NEIGHBOR multicast address (Section 3.4). 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 [RFC6206].
A GDNP device with multiple link-layer interfaces (typically a router) MUST support synchronization flooding on all interfaces. If it receives a multicast unsolicited Response message on a given interface, it MUST relay it by re-issuing the same Response message on its other interfaces. However, it MUST limit the total rate at which it relays Response 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 Response message which carries such a cached Session ID. These precautions avoid synchronization loops.
Note that this mechanism is unreliable in the case of sleeping nodes. Sleeping nodes that require an objective subject to synchronization flooding SHOULD periodically initiate normal synchronization for that objective.
Rapid Mode (Discovery/Synchronization linkage)
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.
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 [RFC4086].
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.
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 [I-D.ietf-homenet-dncp]).
Every GDNP message carries a Session ID. Options are presented serially in the options field, with padding to 4-byte alignment.
The following diagram illustrates the format of GDNP messages:
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) | . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
DISCOVERY (MESSAGE_TYPE = G1):
A discovery initiator sends a DISCOVERY message to initiate a discovery process.
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).
A DISCOVERY message MUST include exactly one of the following:
RESPONSE (MESSAGE_TYPE = G2):
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.
If the responding node supports the discovery objective of the discovery, it MUST include at least one kind of locator option (Section 3.7.7) to indicate its own location. A combination of multiple kinds of locator options (e.g. IP address option + FQDN option) is also valid.
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 (Section 3.7.2) embedding a locator option or a combination of multiple kinds of locator options which indicate the locator(s) of the discovery objective.
A node which receives a synchronization request sends a Response message with the synchronization data, in the form of GDNP Option(s) for the specific synchronization objective(s).
REQUEST (MESSAGE_TYPE = G3):
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).
A request message MUST include the relevant objective option, with the requested value in the case of negotiation.
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 (Section 3.6.7), the initiator will consider that the negotiation has failed when the timer expires.
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.
NEGOTIATION (MESSAGE_TYPE = G4):
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.
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.
NEGOTIATION-ENDING (MESSAGE_TYPE = G5):
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 Section 3.7.3 and Section 3.7.4. It could be sent either by the requesting node or the responding node.
CONFIRM-WAITING (MESSAGE_TYPE = G6):
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 (Section 3.7.5).
This section defines the GDNP general options for the negotiation and synchronization protocol signaling. Additional option types are reserved for GDNP general options defined in the future.
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) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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.
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.
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 Target(s) | . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The accept option is used to indicate to the negotiation counterpart that the proposed negotiation content is accepted.
The accept option MUST only be encapsulated in Negotiation-ending messages. If found elsewhere, it SHOULD be silently ignored.
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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The decline option is used to indicate to the negotiation counterpart the proposed negotiation content is declined and end the negotiation process.
The decline option MUST only be encapsulated in Negotiation-ending messages. If found elsewhere, it SHOULD be silently ignored.
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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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.
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.
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 (Section 3.6.4).
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.
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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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:
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) . . . | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
These locator options are used to present reachability information for an ASA, a device or an interface. They are Locator IPv4 Address Option, Locator IPv6 Address Option and Locator FQDN (Fully Qualified Domain Name) Option.
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.
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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Note: If an operator has internal network address translation for IPv4, this option MUST NOT be used within the Divert option.
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 | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Note: A link-local IPv6 address MUST NOT be used when this option is used within the Divert option.
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) | . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Note: Any FQDN which might not be valid throughout the network in question, such as a Multicast DNS name [RFC6762], MUST NOT be used when this option is used within the Divert option.
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:
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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | flags | loop-count | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ value | . (variable length) . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Objective Options MUST be assigned an option type greater than G63 in the GDNP option table.
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.
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.
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.
Synchronization Objective Options are similar, but MUST be carried by Discovery, Request or Response messages only. They include value fields only in Response messages.
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.
A synchronization objective SHOULD also be organized as a single GDNP option.
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).
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.
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.
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.
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) [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.
In the case of a vendor-specific objective, the loop count and flags, if present, follow the PEN.
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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | flags | loop-count | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ value | . (variable length) . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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.
These option codes are also RECOMMENDED for use in documentation examples.
There are various unresolved design questions that are worthy of more work in the near future, as listed below (statically numbered in historical order for reference purposes, with the resolved issues retained for reference):
RESOLVED by changing security model.
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.
- Authentication
- Privacy and confidentiality
- DoS Attack Protection
- Security during bootstrap and discovery
Section 3.4 defines the following link-local multicast addresses, which have been assigned by IANA for use by GDNP:
Section 3.4 defines the following UDP and TCP port, which has been assigned by IANA for use by GDNP:
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 [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.
Initial values for these registries are given below. Future assignments are to be made through Standards Action or Specification Required [RFC5226]. Assignments for each registry consist of a type code value, a name and a document where the usage is defined.
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.
GDNP Messages table. The values in this table are 16-bit unsigned integers. The following initial values are assigned in Section 3.6 in this document:
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 |
GDNP Options table. The values in this table are 16-bit unsigned integers. The following initial values are assigned in Section 3.7 and Section 3.8.1 in this document:
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 |Locator IPv4 Address Option | this document
G38 |Locator IPv6 Address Option | this document
G39 |Locator 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 |
A major contribution to the original version of this document was made by Sheng Jiang.
Valuable comments were received from Michael Behringer, Jeferson Campos Nobre, Laurent Ciavaglia, 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.
This document was produced using the xml2rfc tool [RFC2629].
draft-carpenter-anima-discovery-negotiation-protocol-04, 2015-06-21:
Tuned wording around hierarchical structure.
Changed "device" to "ASA" in many places.
Reformulated requirements to be clear that the ASA is the main customer for signaling.
Added requirement for flooding unsolicited synch, and added it to protocol spec. Recognized DNCP as alternative for flooding synch data.
Requirements clarified, expanded and rearranged following design team discussion.
Clarified that GDNP discovery must not be a prerequisite for GDNP negotiation or synchronization (resolved issue 13).
Specified flag bits for objective options (resolved issue 15).
Clarified usage of ACP vs TLS/DTLS and TCP vs UDP (resolved issues 9,10,11).
Updated DNCP description from latest DNCP draft.
Editorial improvements.
draft-carpenter-anima-discovery-negotiation-protocol-03, 2015-04-20:
Removed intrinsic security, required external security
Format changes to allow ADNCP co-existence
Recognized DNS-SD as alternative discovery method.
Editorial improvements
draft-carpenter-anima-discovery-negotiation-protocol-02, 2015-02-19:
Tuned requirements to clarify scope,
Clarified relationship between types of objective,
Clarified that objectives may be simple values or complex data structures,
Improved description of objective options,
Added loop-avoidance mechanisms (loop count and default timeout, limitations on discovery relaying and on unsolicited responses),
Allow multiple discovery objectives in one response,
Provided for missing or multiple discovery responses,
Indicated how modes such as "dry run" should be supported,
Minor editorial and technical corrections and clarifications,
Reorganized future work list.
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.
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.
| [RFC2119] | Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. |
| [RFC4086] | Eastlake, D., Schiller, J. and S. Crocker, "Randomness Requirements for Security", BCP 106, RFC 4086, June 2005. |
| [RFC5246] | Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) Protocol Version 1.2", RFC 5246, August 2008. |
| [RFC5280] | Cooper, D., Santesson, S., Farrell, S., Boeyen, S., Housley, R. and W. Polk, "Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile", RFC 5280, May 2008. |
| [RFC6347] | Rescorla, E. and N. Modadugu, "Datagram Transport Layer Security Version 1.2", RFC 6347, January 2012. |
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.
Numerous protocols include some form of discovery, but these all appear to be very specific in their applicability. Service Location Protocol (SLP) [RFC2608] provides service discovery for managed networks, but requires configuration of its own servers. DNS-SD [RFC6763] combined with mDNS [RFC6762] provides service discovery for small networks with a single link layer. [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.
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.
Simple Network Management Protocol (SNMP) [RFC3416] uses a command/response model not well suited for peer negotiation. Network Configuration Protocol (NETCONF) [RFC6241] uses an RPC model that does allow positive or negative responses from the target system, but this is still not adequate for negotiation.
There are various existing protocols that have elementary negotiation abilities, such as Dynamic Host Configuration Protocol for IPv6 (DHCPv6) [RFC3315], Neighbor Discovery (ND) [RFC4861], Port Control Protocol (PCP) [RFC6887], Remote Authentication Dial In User Service (RADIUS) [RFC2865], Diameter [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.
There are some signaling protocols with an element of negotiation. For example Resource ReSerVation Protocol (RSVP) [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 [RFC3209]. A more generic design is General Internet Signalling Transport (GIST) [RFC5971], but it is complex, tries to solve many problems, and is also aimed at per-flow signaling across many hops rather than at device-to-device signaling. 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.
We now consider two protocols that are works in progress at the time of this writing. Firstly, RESTCONF [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.
Secondly, we consider Distributed Node Consensus Protocol (DNCP) [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) [I-D.ietf-homenet-hncp] for configuring Homenet routers. A specific application of DNCP for autonomic networking was proposed in [I-D.stenberg-anima-adncp].
DNCP "is designed to provide a way for each participating node to publish a set of TLV (Type-Length-Value) tuples, and to provide a shared and common view about the data published... DNCP is most suitable for data that changes only infrequently... If constant rapid state changes are needed, the preferable choice is to use an additional point-to-point channel..."
Specific features of DNCP include:
DNCP does not meet the needs of a general negotiation protocol, because it is designed specifically for flooding synchronization. Also, in its HNCP profile it is limited to link-local messages and to 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.
A proposal was made some years ago for an IP based Generic Control Protocol (IGCP) [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.
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.