Internet DRAFT - draft-ietf-vrrp-ext
draft-ietf-vrrp-ext
Network Working Group A. Celer
Internet Draft
Expiration Date: December 1999
Nortel (Northern Telecom) Ltd.
June 1999
VRRP Extention to Support Dynamic Topology Changes
of Virtual Router topology
draft-ietf-vrrp-ext-00.txt
Status of this Memo
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Abstract
This draft defines an extention to Virtual Router Redundancy Protocol
(VRRP) [1] which limits the amount of provisioning required to
support the VRRP operations. It specifically addresses the scenario
when the primary owner of the interfaces leaves the Virual Router
group.
Table of Contents
1 Introduction ............................................ 2
2 VRRP State Machine ...................................... 2
3 Sending and Receiving VRRP Packets ...................... 5
4 Security Considerations ................................. 6
5 Message Formats ......................................... 6
6 Backward Compatibility .................................. 8
7 Refrences ............................................... 8
8 Author's Address ........................................ 8
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Internet Draft ietf-draft-vrrp-ext.txt June 1999
1. Introduction
The Virtual Router Redundancy Protocol (VRRP) specifies an election
protocol that dynamically assigns responsibility for a virtual router
to one of the VRRP routers on the LAN. The VRRP router controlling
the IP address(es) associated with the virtual router is called the
Master, and forwards packets sent to these IP addresses. In case of
the Master's failure or deliberate decision to leave the group,
the back-up virtual router will assume the forwarding responsibility
for these IP addresses.
Current protocol definition does not allow for the dynamic removal
of the IP address(es) if the router decides to the leave group of
routers it belongs to. Currently, the router sends the VRRP
advertisement message, specifying priority zero for the addresses.
Another router in this virtual router group will assume ownership
over these addresses. If the IP address(es) are removed from under
Virtual Router control, all routers which participate in this
virtual router have to be de-provisioned.
The proposed extention to the protocol will allow dynamic removal of
IP address(es) associated with router which leaves the virtual
router. This draft introduces the new VRRP message type: LEAVE_GROUP
which can be used to remove the addresses from the virtual router
topology.
2. VRRP State Machine
Introduction of the new VRRP message types does not change the
Virtual Router definition of states in VRRP state machine. New
message type processing is included in appropriate sections.
2.1 Parameters
New attribute is added to discribe the 'persistance' of the IP
address. It can have one of two values: Dynamic and Static.
Dynamic - defines the IP address which should be removed from the
Virtual Router in case that shutdown event is received
Static - defines the IP address which should remain part of the
Virtual Router in case the shutdown event is received.
2.2 Timers
The set of timers does not change.
2.3 Initialize State
The Initialize state does not change.
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2.4 Backup State
The purpose of the {Backup} state is to monitor the availability and
state of the Master Router.
While in this state, a VRRP router MUST do the following:
- MUST NOT respond to ARP requests for the IP address(s) associated
with the virtual router.
- MUST discard packets with a destination link layer MAC address
equal to the virtual router MAC address.
- MUST NOT accept packets addressed to the IP address(es) associated
with the virtual router.
- If a Shutdown event is received, then:
o Cancel the Master_Down_Timer
o Transition to the {Initialize} state
endif
- If the Master_Down_Timer fires, then:
o Send an ADVERTISEMENT
o Broadcast a gratuitous ARP request containing the virtual
router MAC address for each IP address associated with the
virtual router
o Set the Adver_Timer to Advertisement_Interval
o Transition to the {Master} state
endif
- If an ADVERTISEMENT is received, then:
If the Priority in the ADVERTISEMENT is Zero, then:
o Set the Master_Down_Timer to Skew_Time
else:
If Preempt_Mode is False, or If the Priority in the
ADVERTISEMENT is greater than or equal to the local
Priority, then:
o Reset the Master_Down_Timer to Master_Down_Interval
else:
o Discard the ADVERTISEMENT
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endif
endif
endif
- If a LEAVE_GROUP is received, then:
if priority in LEAVE_GROUP message is 255, then:
o Remove the IP address(es) in the message from the database
endif
endif
2.5 Master State
While in the {Master} state the router functions as the forwarding
router for the IP address(es) associated with the virtual router.
While in this state, a VRRP router MUST do the following:
- MUST respond to ARP requests for the IP address(es) associated
with the virtual router.
- MUST forward packets with a destination link layer MAC address
equal to the virtual router MAC address.
- MUST NOT accept packets addressed to the IP address(es) associated
with the virtual router if it is not the IP address owner.
- MUST accept packets addressed to the IP address(es) associated
with the virtual router if it is the IP address owner.
- If a Shutdown event is received, then:
o Cancel the Adver_Timer
o If none of the routers in the Virtual Router group runs VRRPv.2
o send an LEAVE_GROUP message with the list of the interfaces
to be removed from the Virtual Router; priority is set to
255
endif
o send an ADVERTISEMENT with Priority = 0
o Transition to the {Initialize} state
endif
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- If the Adver_Timer fires, then:
o Send an ADVERTISEMENT
o Reset the Adver_Timer to Advertisement_Interval
endif
- If an ADVERTISEMENT is received, then:
If the Priority in the ADVERTISEMENT is Zero, then:
o Send an ADVERTISEMENT
o Reset the Adver_Timer to Advertisement_Interval
else:
If the Priority in the ADVERTISEMENT is greater than the
local Priority,
or
If the Priority in the ADVERTISEMENT is equal to the local
Priority and the primary IP Address of the sender is greater
than the local primary IP Address, then:
o Cancel Adver_Timer
o Set Master_Down_Timer to Master_Down_Interval
o Transition to the {Backup} state
else:
o Discard ADVERTISEMENT
endif
endif
endif
- If LEAVE_GROUP is received, then:
If Priority in the LEAVE_GROUP message is 255, then
o remove included IP addresses from the database
endif
endif
3. Sending and Receiving VRRP Packets
The rules for sending and receiving VRRP packets do not differ
from those defined in [1] .
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4. Security Considerations
The rules do not differ from those defined in [1] .
5. Message Formats
This section defines the format of the VRRP packet. Relevant fields
in the IP header are the same as described in [1].
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Version| Type | Virtual Rtr ID| Priority | Count IP Addrs|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Auth Type | Adver Int | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IP Address (1) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| . |
| . |
| . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IP Address (n) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Authentication Data (1) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Authentication Data (2) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
5.1 Version
The version field specifies the VRRP protocol version of this packet.
This document defines version 3.
5.2 Type
The type field specifies the type of this VRRP packet. There are two
packet types defined:
1 ADVERTISEMENT
2 LEAVE_GROUP
A packet with unknown type MUST be discarded.
5.3 Virtual Rtr ID (VRID)
The Virtual Router Identifier (VRID) field identifies the virtual
router this packet is reporting status for.
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5.2 Type
The type field specifies the type of this VRRP packet. There are two
packet types defined:
1 ADVERTISEMENT
2 LEAVE_GROUP
A packet with unknown type MUST be discarded.
5.3 Virtual Rtr ID (VRID)
The Virtual Router Identifier (VRID) field identifies the virtual
router this packet is reporting status for.
5.4 Priority
The priority field specifies the sending VRRP router's priority for
the virtual router. Higher values equal higher priority. This field
is an 8 bit unsigned integer field.
The priority value for the VRRP router that owns the IP address(es)
associated with the virtual router MUST be 255 (decimal).
VRRP routers backing up a virtual router MUST use priority values
between 1-254 (decimal). The default priority value for VRRP routers
backing up a virtual router is 100 (decimal).
The priority value zero (0) has special meaning indicating that the
current Master has stopped participating in VRRP. This is used to
trigger Backup routers to quickly transition to Master without having
to wait for the current Master to timeout.
In case of LEAVE_GROUP message priority is set to 255 .
5.5 Count IP Addrs
The number of IP addresses contained in this VRRP advertisement.
5.6 Authentication Type
This draft does not change definition of the Authentication types
as defined in [1].
5.7 Advertisement Interval (Adver Int)
This draft does not change definition of the advertisement interval
as defined in [1].
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5.8 Checksum
This draft does not change definition of the checksum as defined in [1].
5.9 IP Address(es)
This draft does not change definition of the IP address(es) as
defined in [1].
5.10 Authentication Data
This draft does not change definition of the authentication data as
defined in [1].
6. Backward Compatibility
This extension is backward compatible.
The router which implements version 3 of VRRP protocol will recognize
the presence of version 2 compatible routers in the group, and if it
receives the {shutdown} event, it will send the ADVERTISEMENT message
with pririty zero (0) only. LEAVE_GROUP message, if removal
of its IP address(es) is required will be sent only when all routers
which are members of the Virtual Router run VRRP v.3 .
In case that at least one router in Vritual Router group does not
recognize LEAVE_GROUP message, runs VRRP v.2, it will drop the
message, and take ownership of the IP address(es) which belonged to
router leaving the Virtual Router group. To remove the IP address(es)
from the list, all routers in Virtual Router group will have to go
through {shutdown} event.
7. References
[1] RFC2338 Virtual Router Redundancy Protocol
8. Author's Address
Alicja Celer
Nortel (Northern Telecom), Ltd.
PO Box 3511 Station C
Ottawa ON K1Y 4H7
Canada
EMail: aceler@nortelnetworks.com
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