Internet DRAFT - draft-stenberg-anima-adncp
draft-stenberg-anima-adncp
ANIMA M. Stenberg
Internet-Draft
Intended status: Standards Track March 5, 2015
Expires: September 6, 2015
Autonomic Distributed Node Consensus Protocol
draft-stenberg-anima-adncp-00
Abstract
This document describes the Autonomic Distributed Node Consensus
Protocol (ADNCP), a profile of Distributed Node Consensus Protocol
(DNCP) for autonomic networking.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 2
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. DNCP Profile . . . . . . . . . . . . . . . . . . . . . . . . 3
5. Point-To-Point Operations . . . . . . . . . . . . . . . . . . 4
6. Distributed Operations . . . . . . . . . . . . . . . . . . . 5
6.1. Discovery . . . . . . . . . . . . . . . . . . . . . . . . 5
6.2. Negotiation / Synchronization . . . . . . . . . . . . . . 5
6.3. Intent Distribution . . . . . . . . . . . . . . . . . . . 5
7. Area Support . . . . . . . . . . . . . . . . . . . . . . . . 6
7.1. Area Boundaries . . . . . . . . . . . . . . . . . . . . . 6
7.2. Area Identifier . . . . . . . . . . . . . . . . . . . . . 6
7.3. Area Formation . . . . . . . . . . . . . . . . . . . . . 6
7.4. Import/Export . . . . . . . . . . . . . . . . . . . . . . 8
8. Security Considerations . . . . . . . . . . . . . . . . . . . 8
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
10.1. Normative references . . . . . . . . . . . . . . . . . . 8
10.2. Informative references . . . . . . . . . . . . . . . . . 9
Appendix A. Open Issues . . . . . . . . . . . . . . . . . . . . 9
Appendix B. Changelog . . . . . . . . . . . . . . . . . . . . . 10
Appendix C. Draft Source . . . . . . . . . . . . . . . . . . . . 10
Appendix D. Acknowledgements . . . . . . . . . . . . . . . . . . 10
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
DNCP [I-D.ietf-homenet-dncp] provides a single-area link state
database for arbitrary use. ADNCP extends DNCP in several ways and
makes it implementable by defining a profile.
ADNCP allows for several types of point-to-point exchanges that match
typical autonomic operations. The shared state within ADNCP itself
is used to also facilitate some autonomic operations. Whether point-
to-point or multi-party algorithms are used is left up to the
specification of particular objectives.
To provide for better scalability than the base DNCP, ADNCP also
defines (optionally zero-configuration) multi-area system.
2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
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3. Terminology
Reader is assumed to be familiar with the autonomic networking
terminology described in
[I-D.irtf-nmrg-autonomic-network-definitions] and
[I-D.ietf-homenet-dncp].
(ADNCP) area: A set of ADNCP running nodes that are directly
connected using a set of DNCP connections. In other words, DNCP
network. They share a link state database, and may also have some
other data from other areas but no actual topology of the other
areas.
(ADNCP) network: A set of connected ADNCP areas.
area owner: The ADNCP node with the highest Node Identifier within
the ADNCP area.
connection owner: Either ADNCP node with the highest Node Identifier
on a multicast-capable link the connection maps to, or the unicast
"server" node that other nodes connect.
per-area: Applicable to the nodes in a particular area.
area-wide: Distribution scope in which content is made available to
nodes in only one area.
per-net: Applies to the whole (ADNCP) network.
net-wide: Distribution scope in which content is made available to
nodes in all areas.
4. DNCP Profile
ADNCP is defined as a profile of DNCP [I-D.ietf-homenet-dncp] with
the following parameters:
o ADNCP uses UDP datagrams on port ADNCP-UDP-PORT as a multicast
transport over IPv6 using group All-ADNCP-Nodes-6, or IPv4 using
group All-ADNCP-Nodes-4. TLS [RFC5246] on port ADNCP-TCP-PORT is
used for unicast transport. Non-secure unicast transport MUST NOT
be used and therefore is not defined at all. In a typical case,
multicast transport SHOULD be link-local scoped, although other
scopes MAY be also used and supported if multicast routing is
available.
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o ADNCP operates over either unicast connections, or over multicast-
capable interfaces. Therefore the value encoded in the DNCP
Connection Identifier is left up to the implementation.
o ADNCP nodes MUST support the X.509 PKI-based trust method, and MAY
support the DNCP Certificate Based Trust Consensus method.
o ADNCP nodes MUST use the leading 128 bits of SHA256 [RFC6234] as
DNCP non-cryptographic hash function H(x).
o ADNCP uses 128-bit node identifiers (DNCP_NODE_IDENTIFIER_LENGTH =
128). A node implementing ADNCP MUST generate their node
identifier by applying the SHA256 to their public key. If the
node receives a Node State TLV with the same node identifier and a
higher update sequence number multiple times, an error SHOULD be
made visible to an administrator.
o ADNCP nodes MUST NOT send multicast Long Network State messages,
and received ones MUST be ignored
o ADNCP nodes use the following Trickle parameters:
* k SHOULD be 1, given the timer reset on data updates and
retransmissions should handle packet loss.
* Imin SHOULD be 200 milliseconds but SHOULD NOT be lower. Note:
Earliest transmissions may occur at Imin / 2.
* Imax SHOULD be 7 doublings of Imin (i.e. 25.6 seconds) but
SHOULD NOT be lower.
o ADNCP nodes MUST use the keep-alive extension on all multicast
interface-based connections. The default keep-alive interval
(DNCP_KEEPALIVE_INTERVAL) is 20 seconds, the multiplier
(DNCP_KEEPALIVE_MULTIPLIER) MUST be 2.1, the grace-interval
(DNCP_GRACE_INTERVAL) SHOULD be equal to DNCP_KEEPALIVE_MULTIPLIER
times DNCP_KEEPALIVE_INTERVAL.
5. Point-To-Point Operations
For point-to-point operations such as discovery, negotiation, and
synchronization, a single new class of DNCP messages is defined (TBD
- more detail?). It is identified by the presence of an objective-
specific TLV, and if specified by the objective, it SHOULD be
responded to only via unicast at most. Therefore, if an ADNCP
implementation does not recognize a message, it MUST be silently
ignored. These messages SHOULD NOT in and of themselves establish a
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DNCP-style bidirectional peering relationship between nodes, and
therefore SHOULD NOT contain Node Connection TLV..
Such objective-specific messages should either define some
transaction id scheme (TBD - should it be here), or include the
request verbatim within the replies, if any.
6. Distributed Operations
6.1. Discovery
If point-to-point discovery (using either multicast-capable
interface(s), or known unicast peers) is not chosen, discovery can be
handled also either by participating in the ADNCP network, or by
performing point-to-point operation with a node participating in the
ADNCP.
Presence (or lack) of content with ADNCP can be used to discover
nodes that support particular objectives in some specific way; for
example, an objective might specify TLV which contains an address of
some particular type of server (for example, DHCPv6 PD), and
therefore by just using ADNCP information, "closest" node (in terms
of areas / in terms of routing of the address) could be determined.
6.2. Negotiation / Synchronization
ADNCP is not suitable for (especially net-wide) transmission of any
data that changes rapidly. Therefore it should be used to sparingly
publish data that changes at most gradually.
With that limitation in mind, ADNCP can be used to implement
arbitrary multi-party algorithms, such as Prefix Assignment
[I-D.ietf-homenet-prefix-assignment]. Given appropriate per-area
hierarchical assignment (published net-wide), it could be also
employed net-wide though, as the per-net prefix assignments would
change only rarely.
For rapidly changing data, point-to-point exchanges (as needed)
should be used instead and just e.g. relevant IP addresses published
via ADNCP.
6.3. Intent Distribution
Arbitrary (operator-supplied) objective-specific intent can be
supplied as TLVs within ADNCP, either per-area or per-network.
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7. Area Support
Area support for DNCP is added so that non-area-capable
implementations can benefit from it, but cannot support more than one
interface (for same DNCP instance at any rate), as they cannot handle
the logic for transferring data between areas.
Areas are uniquely identified by a 32-bit Area Identifier.
7.1. Area Boundaries
A single connection always belongs to exactly one area. Therefore
the boundaries of the areas are within nodes that have multiple
connections, and can transfer data between them.
For every remote area detected (=on other connections, not on that
particular connection), a node should include a Remote Area TLV which
contains an Area Identifier, a Node Identifier of the area owner, and
pared down (recursive) list of Remote Area TLVs from that area, that
MUST be loop free. An exception to the rule is the current area; if
the current area is advertised elsewhere, it MUST be included if and
only if the owner's Node Identifier differs from the local one.
Longer paths to particular areas with matching owner Node Identifier
MAY be also omitted.
TBD: Remote Area TLV - area id, area owner (+container for more
Remote Area TLVs recursively)
7.2. Area Identifier
Area Identifier for every connection is chosen by the connection
owner. The link is owned by the node with the highest Node
Identifier on a connection which consists of a multicast-capable
link, or the "server" node which other nodes are connecting to in
case of an unicast link.
TBD: Area Identifier TLV - just area id - originated by the area
owner, and then included in every unicast message on link.
7.3. Area Formation
Areas by definition are connected parts of the network. An operator
may set explicit values for the Area Identifiers, thereby forming the
areas, or alternatively an automatic formation process described here
can be used by the connection owners. Non connection owners on a
particular connection should simply follow the connection owner's
lead.
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If the connection owner does not have an area on a particular
connection yet, it may use an existing area from some other
connection if and only if following suitability criteria are met:
o The current set of links covered by that area (calculated by
traversing through the neighbor graph) is not more than TBD.
o The number of nodes in that area is not more than TBD.
o The area owner does not publish an Area Full TLV.
If nothing suitable is present, areas connected directly to other
nodes within the area can be also considered. For them, the
suitability criteria are:
o A node within current area exists which publishes Remote Area TLV
with the Area Identifier of the area.
o No published Area Full TLV for the area.
If choosing to use a particular area, the node MUST wait random
[TBD1, TBD2] seconds before making the actual assignment, and ensure
that the suitability criteria are still matched when it makes the
assignment. If not, this process should be repeated again, starting
from evaluating the candidates.
If no area is found at all, a new area should be created, with a
random delay of [TBD1, TBD2] seconds before announcing. At the end
of the interval, the presence of available areas to join should be
checked before publishing the Area Identifier TLV.
Once the area owner notices that the directly connected suitability
criteria enumerated above are no longer filled by the local area (=it
is too large), the area owner MUST publish an Area Full TLV. It MAY
be removed at later point, but if and only if the area is
substantially below the maximum desired size in terms of number of
links and number of nodes.
If the owner of an area detects the presence of a Remote Area TLV
with an Area Identifier identical to that of the area it is
advertising and with an owner having a higher Node Identifier than
itself, then the area owner MUST choose a new (random) Area
Identifier.
TBD: Area Full TLV - no content, but net-wide.
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7.4. Import/Export
There is no explicit exporting of TLVs; any TLV type that has highest
bit set (0x8000) will be considered area-originated, and spread net-
wide, as opposed to the default area-wide node-originated. It is
important to note that currently node identifier of the originating
node is lost as it transitions to another area (TBD), but within the
area the originator is still visible.
Given the node is on an area boundary, for all areas it is in, it
must recursively traverse all Remote Area TLVs announced within the
area, and keep track of the shortest recursion depth at which a
particular area is first encountered. The Node Identifier of the
Remote Area TLV originator is used for tie-breaking, with the higher
one preferred. If encountering Remote Area TLV with the local area's
Area Identifier, that TLV MUST NOT be recursed into to avoid loops.
For any areas for which the node is identified as the importer (by
having shortest path of areas, or winning tie-break), the node MUST
import Remote Area Content TLV from the first-hop remote area
verbatim if there are other areas on the path. If the node is
directly connected to the remote area, it MUST create and maintain
Remote Area Content TLV which contains all TLVs marked for export.
When Remote Area Content TLV changes, or is no longer present in the
"upstream" area, it must be also updated/removed by the importer.
TBD: Remote Area Content TLV - area id (+container for any exported
TLVs from that area)
8. Security Considerations
TBD
9. IANA Considerations
TBD - TLVs values here + ADNCP-UDP-PORT, ADNCP-TCP-PORT
All-ADNCP-Nodes-4, All-ADNCP-Nodes-6
10. References
10.1. Normative references
[I-D.ietf-homenet-dncp]
Stenberg, M. and S. Barth, "Distributed Node Consensus
Protocol", draft-ietf-homenet-dncp-00 (work in progress),
January 2015.
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[RFC6234] Eastlake, D. and T. Hansen, "US Secure Hash Algorithms
(SHA and SHA-based HMAC and HKDF)", RFC 6234, May 2011.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, August 2008.
10.2. Informative references
[I-D.ietf-homenet-prefix-assignment]
Pfister, P., Paterson, B., and J. Arkko, "Distributed
Prefix Assignment Algorithm", draft-ietf-homenet-prefix-
assignment-03 (work in progress), February 2015.
[I-D.irtf-nmrg-autonomic-network-definitions]
Behringer, M., Pritikin, M., Bjarnason, S., Clemm, A.,
Carpenter, B., Jiang, S., and L. Ciavaglia, "Autonomic
Networking - Definitions and Design Goals", draft-irtf-
nmrg-autonomic-network-definitions-05 (work in progress),
December 2014.
Appendix A. Open Issues
Should hierarchical PA be defined here or not?
[I-D.ietf-homenet-prefix-assignment], with cross-area hierarchical
extension, would facilitate even very large scale PA (with
potentially multiple upstreams). Perhaps the current mention is
enough.
Should areas importers / area ID choice TLVs include precedence
value?
Should we include node-data signatures or not? They improve
security, but are not visible across areas in any case - it would
need per-TLV signature(!) in that case with a hefty footprint due to
needing to include way to identify the public key too. So I think
not.
Should some way to publish certificate id / raw public key be
defined? So it can be verified that e.g. node identifier is really
generated based on one. Perhaps..
Should some sort of more granular delta transfer scheme be defined?
For a large network, the current scheme's TLV set published by a
single node can grow to substantial size. This may occur either here
or in DNCP.
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Appendix B. Changelog
draft-stenberg-anima-adncp-00: Initial version.
Appendix C. Draft Source
As usual, this draft is available at https://github.com/fingon/ietf-
drafts/ in source format (with nice Makefile too). Feel free to send
comments and/or pull requests if and when you have changes to it!
Appendix D. Acknowledgements
Thanks to Pierre Pfister, Mark Baugher and Steven Barth for their
contributions to the draft.
Author's Address
Markus Stenberg
Helsinki 00930
Finland
Email: markus.stenberg@iki.fi
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