Dynamic Host Configuration (DHC) T. Mrugalski
Internet-Draft ISC
Intended status: Informational K. Kinnear
Expires: December 12, 2013 Cisco
June 10, 2013
DHCPv6 Failover Requirements
draft-ietf-dhc-dhcpv6-failover-requirements-05
Abstract
The DHCPv6 protocol, defined in [RFC3315] allows for multiple servers
to operate on a single network, however it does not define any way
the servers could share information about currently active clients
and their leases. Some sites are interested in running multiple
servers in such a way as to provide increased availability in case of
server failure. In order for this to work reliably, the cooperating
primary and secondary servers must maintain a consistent database of
the lease information. [RFC3315] allows for but does not define any
redundancy or failover mechanisms. This document outlines
requirements for DHCPv6 failover, enumerates related problems, and
discusses the proposed scope of work to be conducted. This document
does not define a DHCPv6 failover protocol.
Status of This Memo
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This Internet-Draft will expire on December 12, 2013.
Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved.
Mrugalski & Kinnear Expires December 12, 2013 [Page 1]
Internet-Draft DHCPv6 Failover Requirements June 2013
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Table of Contents
1. Requirements Language . . . . . . . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Scope of work . . . . . . . . . . . . . . . . . . . . . . . . 5
4.1. Alternatives to Failover . . . . . . . . . . . . . . . . 5
4.1.1. Short-lived addresses . . . . . . . . . . . . . . . . 5
4.1.2. Redundant servers . . . . . . . . . . . . . . . . . . 5
4.1.3. Distributed databases . . . . . . . . . . . . . . . . 6
4.1.4. Load Balancing . . . . . . . . . . . . . . . . . . . 6
5. Failover Scenarios . . . . . . . . . . . . . . . . . . . . . 6
5.1. Hot Standby Model . . . . . . . . . . . . . . . . . . . . 7
5.2. Geographically Distributed Failover . . . . . . . . . . . 7
5.3. Load balancing . . . . . . . . . . . . . . . . . . . . . 7
5.4. 1-to-1, m-to-1 and m-to-m models . . . . . . . . . . . . 7
5.5. Split prefixes . . . . . . . . . . . . . . . . . . . . . 8
5.6. Long lived connections . . . . . . . . . . . . . . . . . 8
5.7. Partial server communication loss . . . . . . . . . . . . 8
6. Principles of DHCPv6 Failover . . . . . . . . . . . . . . . . 8
6.1. Failure modes . . . . . . . . . . . . . . . . . . . . . . 9
6.1.1. Server Failure . . . . . . . . . . . . . . . . . . . 9
6.1.2. Network partition . . . . . . . . . . . . . . . . . . 9
6.2. Synchronization mechanisms . . . . . . . . . . . . . . . 10
6.2.1. Lockstep . . . . . . . . . . . . . . . . . . . . . . 10
6.2.2. Lazy updates . . . . . . . . . . . . . . . . . . . . 11
7. DHCPv4 and DHCPv6 Failover Comparison . . . . . . . . . . . . 11
8. DHCPv6 Failover Requirements . . . . . . . . . . . . . . . . 12
8.1. Features out of scope . . . . . . . . . . . . . . . . . . 13
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