Re: Proposal for Maintenance Event for VRRP [RFC-5798]

Hi Sreenatha

This ideas is based on the way the priority is defined in Section 5.2.4. and 6.1. of RFC-5798.

"
   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 time out.
"

"
   Priority              <snip>  The value of 0 (zero) is
                               reserved for the Master router to
                               indicate it is releasing responsibility
                               for the virtual router.  The range 1-254
                               (decimal) is available for VRRP routers
                               backing up the virtual router. <snip>
"

Please see my responses inline [Anurag]:

Thanks
-Anurag

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of sreenatha
Sent: Thursday, February 21, 2013 11:03 AM
To: [email protected]
Subject: Re: [VRRP] Proposal for Maintenance Event for VRRP [RFC-5798]

Hi Anurag,
     Proposed idea is good. I have some queries on this proposal:

1. On receiving new maintenance_event, priority of the router is not changed, right? So if back-up router has less priority, even if Master receives the ADVERTISEMENT from the backup router, Master will discard. 
So how the Master router state is going to change?

[Anurag] On receiving the maintenance event the priority of router (or VRID) will change to 0.

2. How much time Master router should wait to receive ADVERTISEMENT message from any backup router?

[Anurag] Master doesn't have to wait. After receiving the maintenance event it will send regular ADVERTISEMENT with Priority = 0 till some other router send back an ADVERTISEMENT message at which point it will transition to Backup.

3. Standard VRRP MIB(RFC-2787) does not allow user to configure '0' for VRRP Priority. So you are proposing to change this value also?

[Anurag] Yes. Priority 0 will have to be made a user configurable value to indicate the intention of a router to relinquish Master Status.

Thanks,
Sreenatha Setty

On 02/21/2013 01:30 AM, [email protected] wrote:
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>     1. Proposal for Maintenance Event for VRRP [RFC-5798]
>        (Anurag Kothari (ankothar))
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Tue, 19 Feb 2013 22:08:41 +0000
> From: "Anurag Kothari (ankothar)"<[email protected]> 
> To:"[email protected]"  <[email protected]>
> Subject: [VRRP] Proposal for Maintenance Event for VRRP [RFC-5798]
> Message-ID:
> 	<[email protected]>
> Content-Type: text/plain; charset="us-ascii"
>
> Hi
>
> I want to propose a new Maintenance Event (modification of Shutdown Event) for VRRP (RFC-5798] which would allow to gracefully failover the VRRP Master to Redundant (Backup Router).
>
> Problem Statement:
> VRRP preemption is not configured on the redundant / backup router. 
> How to initiate VRRP Traffic to failover to the redundant / backup 
> router gracefully without modifying the configuration on the redundant 
> / backup router (i.e. adding preemption)
>
> Proposed Solution:
> Addition to Section 6.4.3 of RFC-5798:
>
> - If a Maintenance event is received, then:
>
> + Cancel the Adver_Timer
>
> + Send an ADVERTISEMENT with Priority = 0
>
> -endif // maintenance recv
>
> Unlike Shutdown event the router will not "Transition to the {Initialize} state" and continue to be Master and forward traffic  till the backup router sends an ADVERTISEMENT (triggered by receiving an ADVERTISEMENT with Priority = 0) and becomes master.

>
> Here are couple of examples of how a maintenance event may be 
> triggered
>
>
> 1)      By some user command e.g. "maintenance-mode" in the vrrp configuration.
>
> 2)      By setting the priority = 0 for a particular VRID.
>
> Thanks
> -Anurag
>
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