draft-ietf-homenet-prefix-assignment-03.txt   draft-ietf-homenet-prefix-assignment-04.txt 
Network Working Group P. Pfister Network Working Group P. Pfister
Internet-Draft B. Paterson Internet-Draft B. Paterson
Intended status: Standards Track Cisco Systems Intended status: Standards Track Cisco Systems
Expires: August 12, 2015 J. Arkko Expires: September 23, 2015 J. Arkko
Ericsson Ericsson
February 8, 2015 March 22, 2015
Distributed Prefix Assignment Algorithm Distributed Prefix Assignment Algorithm
draft-ietf-homenet-prefix-assignment-03 draft-ietf-homenet-prefix-assignment-04
Abstract Abstract
This document specifies a distributed algorithm for automatic prefix This document specifies a distributed algorithm for automatic prefix
assignment. Given a set of delegated prefixes, it ensures that at assignment. Given a set of delegated prefixes, it ensures that at
most one prefix is assigned from each delegated prefix to each link. most one prefix is assigned from each delegated prefix to each link.
Nodes may assign available prefixes to the links they are directly Nodes may assign available prefixes to the links they are directly
connected to, or for other private purposes. The algorithm connected to, or for other private purposes. The algorithm
eventually converges and ensures that all assigned prefixes do not eventually converges and ensures that all assigned prefixes do not
overlap. overlap.
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on August 12, 2015. This Internet-Draft will expire on September 23, 2015.
Copyright Notice Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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4.4. Other Events . . . . . . . . . . . . . . . . . . . . . . 11 4.4. Other Events . . . . . . . . . . . . . . . . . . . . . . 11
5. Prefix Selection Considerations . . . . . . . . . . . . . . . 12 5. Prefix Selection Considerations . . . . . . . . . . . . . . . 12
6. Implementation Capabilities and Node Behavior . . . . . . . . 14 6. Implementation Capabilities and Node Behavior . . . . . . . . 14
7. Algorithm Parameters . . . . . . . . . . . . . . . . . . . . 14 7. Algorithm Parameters . . . . . . . . . . . . . . . . . . . . 14
8. Security Considerations . . . . . . . . . . . . . . . . . . . 15 8. Security Considerations . . . . . . . . . . . . . . . . . . . 15
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 16 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 16
11.1. Normative References . . . . . . . . . . . . . . . . . . 16 11.1. Normative References . . . . . . . . . . . . . . . . . . 16
11.2. Informative References . . . . . . . . . . . . . . . . . 16 11.2. Informative References . . . . . . . . . . . . . . . . . 16
Appendix A. Static Configuration Example . . . . . . . . . . . . 16 Appendix A. Static Configuration Example . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18
1. Introduction 1. Introduction
This document specifies a distributed algorithm for automatic prefix This document specifies a distributed algorithm for automatic prefix
assignment. Given a set of delegated prefixes, nodes may assign assignment. Given a set of delegated prefixes, nodes may assign
available prefixes to links they are directly connected to, or for available prefixes to links they are directly connected to, or for
their private use. The algorithm ensures that the following their private use. The algorithm ensures that the following
assertions are eventually true: assertions are eventually true:
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overlapping prefix with a higher assignment priority, or the topology overlapping prefix with a higher assignment priority, or the topology
changes and renumbering cannot be avoided. changes and renumbering cannot be avoided.
2. Terminology 2. Terminology
In this document, the key words "MAY", "MUST, "MUST NOT", "OPTIONAL", In this document, the key words "MAY", "MUST, "MUST NOT", "OPTIONAL",
and "SHOULD", are to be interpreted as described in [RFC2119]. and "SHOULD", are to be interpreted as described in [RFC2119].
This document makes use of the following terminology: This document makes use of the following terminology:
Node: An entity executing the algorithm specified in this document
and able to communicate with other nodes using the Flooding
Mechanism.
Link: An object the distributed algorithm will assign prefixes to. Link: An object the distributed algorithm will assign prefixes to.
A Node may only assign prefixes to Links it is directly connected A Node may only assign prefixes to Links it is directly connected
to. A Link is either Shared or Private. to. A Link is either Shared or Private.
Private Link: A Private Link is an abstract concept defined for the Private Link: A Private Link is an abstract concept defined for the
sake of this document. It allows nodes to make assignments for sake of this document. It allows nodes to make assignments for
their private use or delegation. For instance, every DHCPv6-PD their private use or delegation. For instance, every DHCPv6-PD
[RFC3633] client MAY be considered as a different Private Link. [RFC3633] requesting router MAY be considered as a different
Private Link.
Shared Link: A Link multiple nodes may be connected to. Most of Shared Link: A Link multiple nodes may be connected to. Most of
the time, a Shared Link would consist in a multi-access link or the time, a Shared Link would consist in a multi-access link or
point-to-point link, virtual or physical, requiring prefixes to be point-to-point link, virtual or physical, requiring prefixes to be
assigned to. assigned to.
Delegated Prefix: A prefix provided to the algorithm and used as a Delegated Prefix: A prefix provided to the algorithm and used as a
prefix pool for Assigned Prefixes. prefix pool for Assigned Prefixes.
Node ID: A value identifying a given participating node. The set Node ID: A value identifying a given participating node. The set
of identifiers MUST be strictly and totally ordered (e.g., using of identifiers MUST be strictly and totally ordered (e.g., using
the alphanumeric order). the alphanumeric order).
Flooding Mechanism: A mechanism implementing reliable broadcast and Flooding Mechanism: A mechanism allowing participating nodes to
used to advertise published Assigned Prefixes. reliably share information with all other participating nodes.
Flooding Delay: Value which SHOULD be provided by the Flooding Flooding Delay: Value which SHOULD be provided by the Flooding
Mechanism indicating a deterministic or likely upper bound of the Mechanism indicating a deterministic or likely upper bound of the
information propagation delay. When the Flooding Mechanism does information propagation delay. When the Flooding Mechanism does
not provide a value, it is set to DEFAULT_FLOODING_DELAY not provide a value, it is set to DEFAULT_FLOODING_DELAY
(Section 7). (Section 7).
Advertised Prefix: A prefix advertised by another node and Advertised Prefix: A prefix advertised by another node and
delivered to the local node by the Flooding Mechanism. It has an delivered to the local node by the Flooding Mechanism. It has an
Advertised Prefix Priority and, when assigned to a directly Advertised Prefix Priority and, when assigned to a directly
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nodes from making colliding assignments by delaying the creation nodes from making colliding assignments by delaying the creation
of new Assigned Prefixes or the advertisement of adopted Assigned of new Assigned Prefixes or the advertisement of adopted Assigned
Prefixes by a random amount of time. Prefixes by a random amount of time.
Renumbering: Event occurring when an Assigned Prefix which was Renumbering: Event occurring when an Assigned Prefix which was
applied is destroyed. It is undesirable as it usually implies applied is destroyed. It is undesirable as it usually implies
reconfiguring routers or hosts. reconfiguring routers or hosts.
3. Applicability statement 3. Applicability statement
Each node MUST have a set of disjoint Delegated Prefixes. This set Each node MUST have a set of disjoint Delegated Prefixes (i.e., which
MAY change over time and be different from one node to another at do not include each other). This set MAY change over time and be
some point, but nodes MUST eventually have the same set of disjoint different from one node to another at some point, but nodes MUST
Delegated Prefixes. eventually have the same set of disjoint Delegated Prefixes.
Given this set of disjoint Delegated Prefixes, nodes may assign Given this set of disjoint Delegated Prefixes, nodes may assign
available prefixes from each Delegated Prefix to the Links they are available prefixes from each Delegated Prefix to the Links they are
directly connected to. The algorithm ensures that at most one prefix directly connected to. The algorithm ensures that at most one prefix
from a given Delegated Prefix is assigned to a given Link. from a given Delegated Prefix is assigned to a given Link.
The algorithm can be applied to any address space and can be used to The algorithm can be applied to any address space and can be used to
manage multiple address spaces simultaneously. For instance, an manage multiple address spaces simultaneously. For instance, an
implementation can make use of IPv4-mapped IPv6 addresses [RFC4291] implementation can make use of IPv4-mapped IPv6 addresses [RFC4291]
in order to manage both IPv4 and IPv6 prefix assignment using a in order to manage both IPv4 and IPv6 prefix assignment using a
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This section specifies the behavior of nodes implementing the prefix This section specifies the behavior of nodes implementing the prefix
assignment algorithm. assignment algorithm.
4.1. Algorithm Terminology 4.1. Algorithm Terminology
The algorithm makes use of the following terms: The algorithm makes use of the following terms:
Current Assignment: For a given Delegated Prefix and Link, the Current Assignment: For a given Delegated Prefix and Link, the
Current Assignment is the Assigned Prefix (if any) included in the Current Assignment is the Assigned Prefix (if any) included in the
Delegated Prefix and assigned to the given Link. Delegated Prefix and assigned to the given Link by the node
executing the algorithm. At some point in time, Current
Assignment from different nodes may differ, but the algorithm
ensures that eventually, all nodes directly connected to a Link
have the same Current Assignment for any given Delegated Prefix.
Precedence: An Advertised Prefix takes precedence over an Assigned Precedence: An Advertised Prefix takes precedence over an Assigned
Prefix if and only if: Prefix if and only if:
* The Assigned Prefix is not published. * The Assigned Prefix is not published.
* The Assigned Prefix is published and the Advertised Prefix * The Assigned Prefix is published and the Advertised Prefix
Priority from the Advertised Prefix is strictly greater than Priority from the Advertised Prefix is strictly greater than
the Advertised Prefix Priority from the Assigned Prefix. the Advertised Prefix Priority from the Assigned Prefix.
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