| Network Working Group | B. Carpenter |
| Internet-Draft | Univ. of Auckland |
| Intended status: Standards Track | S. Jiang |
| Expires: April 16, 2015 | B. Liu |
| Huawei Technologies Co., Ltd | |
| October 13, 2014 |
A Generic Discovery and Negotiation Protocol for Autonomic Networking
draft-carpenter-anima-gdn-protocol-00
This document defines a new protocol that enables intelligent devices to dynamically discover peer devices, to synchronize state with them, and to negotiate mutual configurations with them. This document only defines a general protocol as a negotiation platform, while the negotiation objectives for specific scenarios are to be described in separate documents.
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The success of the Internet has made IP-based networks bigger and more complicated. Large-scale ISP networks have become more and more problematic for human based management. Also operational costs are growing quickly. Consequently, there are therefore increased requirements for autonomy in the networks. General aspects of autonomic networks are discussed in [I-D.irtf-nmrg-autonomic-network-definitions] and [I-D.irtf-nmrg-an-gap-analysis]. In order to fulfil autonomy, devices that are more intelligent need to be able to discover each other, to synchronize state with each other, and negotiate directly with each other.
Following this Introduction and the definition of useful terminology, Section 3 describes the requirements and application scenarios for network device negotiation. Then the negotiation capabilities of various existing protocols are reviewed in Section 4. State synchronization, when needed, can be considered as a special case of negotiation. Prior to negotiation or synchronization, devices must discover each other. Section 5.1 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 5 of this document is mainly based on this behavior model.
Although many negotiations may happen between horizontally distributed peers, the main target scenarios are still hierarchical networks, which is the major structure of current large-scale networks. Thus, where necessary, we assume that each network element has a hierarchical superior. Of course, the protocol itself is capable of being used in a small and/or flat network structure such as a small office or home network, too.
This document defines a Generic Discovery and Negotiation Protocol (GDNP), that can be used to perform decision process among distributed devices or between networks. The newly defined GDNP in this document adapts a tight certificate-based mechanism, which needs a Public Key Infrastructure (PKI, [RFC5280]) system. The PKI may be managed by an operator or be autonomic. The document also introduces a new discovery mechanism, which is based on a neighbor learning process and is oriented towards negotiation objectives.
It is understood that in realistic deployments, not all devices will support GDNP. Such mixed scenarios are not discussed in this specification.
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 section discusses the requirements for discovery, negotiation and synchronization capabilities.
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 discover peer devices. These devices might be immediate neighbors on the same layer 2 link or they might be more distant and only accessible via layer 3.
The relevant peer devices may be different for different discovery 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, discovery process may follow up by negotiation process. Correspondently, the discovery objective may associate with the negotiation objective.
In most networks, as mentioned above, there will be some hierarchical structure. A special case of discovery is that each device must be able to discover its hierarchical superior for each negotiation objective that it is capable of handling.
During initialisation, a device must be able to discover the appropriate trust anchor. Logically, this is just a specific case of discovery. However, it might be a special case requiring its own solution. This question requires further study.
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 announcements (in either direction), rather than on bi-directional negotiation. The only focus is reachability, so current routing protocols only consider simple link status, as 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.
Human intervention in complex situations is costly and error-prone. Therefore, a negotiation model without human intervention is desirable whenever the coordination of multiple devices can provide better overall network performance. Therefore a requirement for the protocol is to be capable of being installed in any device that would otherwise need human intervention.
Human intervention in large networks is often replaced by use of a top-down network management system (NMS). It 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.
Since the goal is no 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.
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.
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.
The protocol needs to be able to deal with a wide variety of negotiation 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.
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.
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.
The analysis does not include discovery protocols. While numerous protocols include some form of discovery, these all appear to be very specific in their applicability.
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 also signalling 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 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.
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 HomeNet Control Protocol (HNCP) [I-D.ietf-homenet-hncp]. This is defined as "a minimalist state synchronization protocol for Homenet routers." Specific features are:
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.
A proposal has been made for an IP based Generic Control Protocol (IGCP) [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.
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, the remainder of 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.
This section describes a behavior model and some considerations for designing a generic discovery and negotiation protocol, which would act as a platform for different negotiation objectives.
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 Section 4 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. This whole specification is subject to change as a result.
To be a generic platform, GDNP should be IP version independent. In other words, it should be able to run over IPv6 and IPv4. Its messages and general options are 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. For these parts, the document defines support for both IP versions separately.
A certification based security mechanism provides security properties for CDNP:
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.
A Request message MUST carry a Certificate option, defined in Section 5.7.6. 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.
Every message MUST carry a signature option, defined in Section 5.7.7.
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 should be far shorter than the normal packet MTU within a modern network.
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 [RFC4270], a mechanism for negotiating the use of more secure hashes in the future is provided.
In addition to hash algorithm agility, a mechanism for signature algorithm agility is also provided.
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.
So far, the algorithm agility is supported by one-way notification, rather than negotiation mode. As defined in Section 5.7.7, 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. To avoid downgrade attacks it MUST NOT fall back to an algorithm considered weak.
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.
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 [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, defined in Section 5.4.
The recipient MUST now authenticate the sender by verifying the Signature and checking a timestamp, as specified in Section 5.2.3.3. 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.
The signature field verification MUST show that the signature has been calculated as specified in Section 5.7.7. 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.
Only the messages that get through both the signature verifications and timestamp check are accepted and continue to be handled for their contained CDNP options. Messages that do not pass the above tests MUST be discarded as insecure messages.
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.
The timestamp is defined in the Signature Option, Section 5.7.7. To facilitate timestamp checking, each recipient SHOULD store the following information for each sender:
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:
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.
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 will be defined separately for each type of negotiation objective.
If the counterpart can immediately apply the requested configuration, it will give a positive (yes) answer. This will normally end the negotiation phase immediately. Otherwise it will give a negative (no) answer. Normally, this will not end the negotiation phase.
In the negative (no) case, the negotiation counterpart should be able to 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.
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.
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.
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.
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 by the network administrator, 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.
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.
The tag value is formed by taking a SHA-1 hash algorithm over the corresponding device certificate and taking the leftmost 128 bits of the hash result.
A 24-bit opaque value used to distinguish multiple sessions between the same two devices. A new Session ID SHOULD be generated for every new Request message. All follow-up messages in the same negotiation procedure, which is initiated by the request message, SHOULD 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.
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.
All GDNP messages share an identical fixed format header and a vaiable 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.
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 | Session ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Device Certificate Tag |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Options (variable length) |
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
MESSAGE_TYPE Identifies the GDNP message type. 8-bit.
Session ID Identifies this negotiation session, as defined in
Section 6. 24-bit.
Device Certificate Tag
Present the Device Certificate, which identifies
the negotiation devices, as defined in Section 5.4.
The Device Certificate Tag is 128 bit, also defined
in Section 5. It is used as index key to find the
device certificate.
Options GDNP Options carried in this message. Options are
definded in Section 5.7, 5.8 and 5.9.
DISCOVERY (1) 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 a discovery objective
option defined in Section 5.8.
A DISCOVERY message MAY include one or more negotiation
objective option(s) (defined in Section 5.9) to indicate
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.
RESPONSE (2) A node which receives a DISCOVERY message sends a
Response message to respond to a discovery.
If the responding node itself is the discovery objective
of the discovery, it MUST include at least one kind of
locator option (defined in 5.7.8) 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 is NOT the discovery
objective, but it knows the locator of the discovery
objective, then it SHOULD respond to the discovery with a
divert option (defined in 5.7.2) embedding a locator
option or a combination of multiple kinds of locator
options which indicate the locator(s) of the discovery
objective.
REQUEST (3) A negotiation requesting node sends the REQUEST message
to the unicast address (directly stored or resolved
from the FQDN) of the negotiation counterpart (selected
from the discovery results).
NEGOTIATION (4)A negotiation counterpart sends a NEGOTIATION
message in response to a REQUEST message, a
Negotiation message, or a DISCOVERY message
in a negotiation process which may need
multiple steps.
NEGOTIATION-ENDING (5)
A negotiation counterpart sends an NEGOTIATION-EDNING
message to close the negotiation. It MUST contain
one, but only one of accept/decline option,
defined in Section 8. It could be sent either by the
requesting node or the responding node.
CONFIRM-WAITING (6)
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 option defined in Section 8.5.
This section defines the GDNP general option for the negotiation protocol signalling. Option type 10~64 is 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) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-code An unsigned integer identifying the specific option
type carried in this option.
Option-len An unsigned integer giving the length of the
option-data field in this option in octets.
Option-data The data for the option; the format of this data
depends on the definition of the option.
The divert option is used to redirect a GDNP request to another node, which may be more appropriate for the intended negotiation. It may redirect to an entity that is known as a specific negotiation counterpart or a default gateway or a hierarchically upstream devices. The divert 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_DIVERT | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Locator Option (s) of Diversion Device(s) |
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-code OPTION_DIVERT (1).
Option-len The total length of diverted destination
sub-option(s) in octets.
Locator Option (s) of Diverted Device(s)
Embedded Locator Option(s), defined in Section 5.7.8,
that point to diverted destination device(s).
The accept option is used to indicate 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Option-code OPTION_ACCEPT (2). Option-len 0.
The decline option is used to indicate 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Option-code OPTION_DECLINE (3). Option-len 0.
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.
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.
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.
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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Option-code OPTION_WAITING (4). Option-len 4, in octets. Time The time is counted in millisecond as a unit.
The Certificate option carries the certificate of the sender. The format of the Certificate 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 Certificate | option-len | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | . Certificate (variable length) . . . | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Option-code OPTION_CERT_PARAMETER (5) Option-len Length of certificate in octets Public key A variable-length field containing a certificate
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:
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) .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-code OPTION_SIGNATURE (6)
Option-len 12 + Length of Signature field in octets.
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.
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.
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.
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:
1. The GDNP message header.
2. All GDNP options including the Signature option
(fill the signature field with zeroes).
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.
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.
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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Option-code OPTION_LOCATOR_IPV4ADDR (7) Option-len 4, in octets. IPv4-Address The IPv4 address locator of the device/interface.
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 | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Option-code OPTION_LOCATOR_IPV6ADDR (8). Option-len 16, in octets. IPv6-Address The IPv6 address locator of the device/interface.
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) | . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Option-code OPTION_FQDN (9). Option-len Length of Fully Qualified Domain Name in octets. Domain-Name The Fully Qualified Domain Name of the entity.
The discovery objective option is to express the discovery objectives that the initiating node wants to discover.
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) |
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-code OPTION_DISOBJ (TBD).
Option-len The total length in octets.
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.
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. Objective options SHOULD be assigned an option type greater than 64 in the GDNP option table.
For most scenarios, there SHOULD be initial values in the negotiation requests. Consequently, the Objective options SHOULD always be completely presented in a Request message. 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.
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.
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.
Option codes 128~159 have been reserved for vendor specific options. Multiple option codes have been assigned because a single vendor may 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. They are not suitable for unmanaged networks such as home networks.
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. They are not suitable for unmanaged networks such as home networks.
There are a few open design questions that are worthy of more work in the near future, as listed below:
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. Security considerations are in the following aspects as the following.
- Authentication
- Privacy
- DoS Attack Protection
Section 5.3 defines the following multicast addresses, which have been assigned by IANA for use by GDNP:
Section 5.3 defines the following UDP port, which have been assigned by IANA for use by GDNP:
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.
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.
GDNP Messages table. The values in this table are 16-bit unsigned integers. The following initial values are assigned in Section 5.6 in this document:
Type | Name | RFCs
---------+-----------------------------+------------
0 |Reserved | this document
1 |Request Message | this document
2 |Negotiation Message | this document
3 |Negotiation-end Message | this document
4 |Confirm-waiting Message | this document
Section 5.7 and Section 5.9 in this document:
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 |Sigature Option | this document
7 |Device IPv4 Address Option | this document
8 |Device IPv6 Address Option | this document
9 |Device FQDN Option | this document
10~64 |Reserved for future CDNP | this document
|General Options |
128~159 |Vendor Specific Options | this document
176~191 |Experimental Options | this document
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 name, a value and a document where the algorithm is defined.
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:
Name | Value | RFCs
---------------------+-----------+------------
Reserved | 0x0000 | this document
SHA-1 | 0x0001 | this document
SHA-256 | 0x0002 | this document
Name | Value | RFCs
---------------------+-----------+------------
Reserved | 0x0000 | this document
RSASSA-PKCS1-v1_5 | 0x0001 | this document
Valuable comments were received from Zhenbin Li, Dacheng Zhang, Rene Struik, Dimitri Papadimitriou, and other participants in the ANIMA and NMRG working group.
This document was produced using the xml2rfc tool [RFC2629].
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. |
| [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. |