draft-ietf-vrrp-ipv6-spec-00.txt   draft-ietf-vrrp-ipv6-spec-01.txt 
INTERNET-DRAFT R. Hinden/Nokia INTERNET-DRAFT R. Hinden/Nokia
October 22, 2001 November 20, 2001
Virtual Router Redundancy Protocol for IPv6 Virtual Router Redundancy Protocol for IPv6
<draft-ietf-vrrp-ipv6-spec-00.txt> <draft-ietf-vrrp-ipv6-spec-01.txt>
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of [RFC2026]. all provisions of Section 10 of [RFC2026].
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Abstract Abstract
This memo defines the Virtual Router Redundancy Protocol (VRRP) for This memo defines the Virtual Router Redundancy Protocol (VRRP) for
IPv6. It is version three (3) of the protocol. It is based on the IPv6. It is version three (3) of the protocol. It is based on the
original version of VRRP (version 2) for IPv4 that is defined in original version of VRRP (version 2) for IPv4 that is defined in
RFC2238. RFC2338.
VRRP specifies an election protocol that dynamically assigns VRRP specifies an election protocol that dynamically assigns
responsibility for a virtual router to one of the VRRP routers on a responsibility for a virtual router to one of the VRRP routers on a
LAN. The VRRP router controlling the IP address associated with a LAN. The VRRP router controlling the IP address associated with a
virtual router is called the Master, and forwards packets sent to virtual router is called the Master, and forwards packets sent to
this IP address. The election process provides dynamic fail over in this IP address. The election process provides dynamic fail over in
the forwarding responsibility should the Master become unavailable. the forwarding responsibility should the Master become unavailable.
The advantage gained from using VRRP for IPv6 is a quicker switch The advantage gained from using VRRP for IPv6 is a quicker switch
over to back up routers than can be obtained with standard IPv6 over to back up routers than can be obtained with standard IPv6
Neighbor Discovery [ND] mechanisms. Neighbor Discovery [ND] mechanisms.
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IPv6 hosts on a LAN will usually learn about one or more default IPv6 hosts on a LAN will usually learn about one or more default
routers by receiving Router Advertisements sent using the IPv6 routers by receiving Router Advertisements sent using the IPv6
Neighbor Discovery protocol [ND]. The Router Advertisements are Neighbor Discovery protocol [ND]. The Router Advertisements are
multicast periodically at a rate that the hosts will learn about the multicast periodically at a rate that the hosts will learn about the
default routers in a few minutes. They are not sent frequently enough default routers in a few minutes. They are not sent frequently enough
to rely on the absence of the router advertisement to detect router to rely on the absence of the router advertisement to detect router
failures. failures.
Neighbor Discovery (ND) includes a mechanism called Neighbor Neighbor Discovery (ND) includes a mechanism called Neighbor
Unreachablity Detection to detect the failure of a neighbor node Unreachability Detection to detect the failure of a neighbor node
(router or host) or the forwarding path to a neighbor. This is done (router or host) or the forwarding path to a neighbor. This is done
by sending unicast ND Neighbor Solicitation messages to the neighbor by sending unicast ND Neighbor Solicitation messages to the neighbor
node. To reduce the overhead of sending Neighbor Solicitations, they node. To reduce the overhead of sending Neighbor Solicitations, they
are only sent to neighbors to which the node is actively sending are only sent to neighbors to which the node is actively sending
traffic and only after there has been no positive indication that the traffic and only after there has been no positive indication that the
router is up for a period of time. Using the default parameters in router is up for a period of time. Using the default parameters in
ND, it will take a host about 38 seconds to learn that a router is ND, it will take a host about 38 seconds to learn that a router is
unreachable before it will switch to another default router. This unreachable before it will switch to another default router. This
delay would be very noticeable to users and cause some transport delay would be very noticeable to users and cause some transport
protocol implementations to timeout. protocol implementations to timeout.
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with its real address on an interface, and may also be configured with its real address on an interface, and may also be configured
with additional virtual router mappings and priority for virtual with additional virtual router mappings and priority for virtual
routers it is willing to backup. The mapping between VRID and it's routers it is willing to backup. The mapping between VRID and it's
IPv6 address must be coordinated among all VRRP routers on a LAN. IPv6 address must be coordinated among all VRRP routers on a LAN.
However, there is no restriction against reusing a VRID with a However, there is no restriction against reusing a VRID with a
different address mapping on different LANs. The scope of each different address mapping on different LANs. The scope of each
virtual router is restricted to a single LAN. virtual router is restricted to a single LAN.
To minimize network traffic, only the Master for each virtual router To minimize network traffic, only the Master for each virtual router
sends periodic VRRP Advertisement messages. A Backup router will not sends periodic VRRP Advertisement messages. A Backup router will not
attempt to pre-empt the Master unless it has higher priority. This attempt to preempt the Master unless it has higher priority. This
eliminates service disruption unless a more preferred path becomes eliminates service disruption unless a more preferred path becomes
available. It's also possible to administratively prohibit all pre- available. It's also possible to administratively prohibit all
emption attempts. The only exception is that a VRRP router will preemption attempts. The only exception is that a VRRP router will
always become Master of any virtual router associated with address it always become Master of any virtual router associated with address it
owns. If the Master becomes unavailable then the highest priority owns. If the Master becomes unavailable then the highest priority
Backup will transition to Master after a short delay, providing a Backup will transition to Master after a short delay, providing a
controlled transition of the virtual router responsibility with controlled transition of the virtual router responsibility with
minimal service interruption. minimal service interruption.
VRRP defines three types of authentication providing simple VRRP defines three types of authentication providing simple
deployment in insecure environments, added protection against deployment in insecure environments, added protection against
misconfiguration, and strong sender authentication in security misconfiguration, and strong sender authentication in security
conscious environments. Analysis of the protection provided and conscious environments. Analysis of the protection provided and
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(3 * Advertisement_Interval) + Skew_time (3 * Advertisement_Interval) + Skew_time
Preempt_Mode Controls whether a higher priority Backup Preempt_Mode Controls whether a higher priority Backup
router preempts a lower priority Master. router preempts a lower priority Master.
Values are True to allow preemption and Values are True to allow preemption and
False to prohibit preemption. Default is False to prohibit preemption. Default is
True. True.
Note: Exception is that the router that owns Note: Exception is that the router that owns
the IPv6 address associated with the virtual the IPv6 address associated with the virtual
router always pre-empts independent of the router always preempts independent of the
setting of this flag. setting of this flag.
Authentication_Type Type of authentication being used. Values Authentication_Type Type of authentication being used. Values
are defined in section 5.3.6. are defined in section 5.3.6.
Authentication_Data Authentication data specific to the Authentication_Data Authentication data specific to the
Authentication_Type being used. Authentication_Type being used.
6.2 Timers 6.2 Timers
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Thomas Narten, and Steve Deering for their his helpful suggestions. Thomas Narten, and Steve Deering for their his helpful suggestions.
13. IANA Considerations 13. IANA Considerations
VRRP for IPv6 needs an IPv6 link-local scope multicast address VRRP for IPv6 needs an IPv6 link-local scope multicast address
assigned by the IANA for this specification. The IPv6 multicast assigned by the IANA for this specification. The IPv6 multicast
address should be of the following form: address should be of the following form:
FF02:0:0:0:0:0:XXXX:XXXX FF02:0:0:0:0:0:XXXX:XXXX
The values assgned address should be entered into section 5.2.2. The values assigned address should be entered into section 5.2.2.
A convenient assignment of this link-local scope multicast would be: A convenient assignment of this link-local scope multicast would be:
FF02:0:0:0:0:0:1:2 FF02:0:0:0:0:0:0:12
as this would be consistent with the IPv4 assignment for VRRP. as this would be consistent with the IPv4 assignment for VRRP.
14. References 14. References
[802.1D] International Standard ISO/IEC 10038: 1993, ANSI/IEEE Std [802.1D] International Standard ISO/IEC 10038: 1993, ANSI/IEEE Std
802.1D, 1993 edition. 802.1D, 1993 edition.
[ADD-ARH] Hinden, R., S. Deering, "IP Version 6 Addressing [ADD-ARH] Hinden, R., S. Deering, "IP Version 6 Addressing
Architecture", RFC2373, July 1988. Architecture", RFC2373, July 1988.
 End of changes. 

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