Re: [VRRP] vrrp Digest, Vol 81, Issue 3

"Anurag Kothari (ankothar)" <ankothar@cisco.com> Fri, 22 February 2013 19:26 UTC

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From: "Anurag Kothari (ankothar)" <ankothar@cisco.com>
To: Thirumavalavan Periyannan <tperiyannan@extremenetworks.com>, "vrrp@ietf.org" <vrrp@ietf.org>
Thread-Topic: [VRRP] vrrp Digest, Vol 81, Issue 3
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Date: Fri, 22 Feb 2013 19:26:35 +0000
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References: <mailman.7259.1361533310.3383.vrrp@ietf.org> <14CA6619-DB7C-40ED-85E4-535CB689AC86@extremenetworks.com> <A2BB90B33FFDF740876C5AAE307D83DB1C292B8C@xmb-rcd-x05.cisco.com> <F547EC1D-C8F0-4468-AFB9-CC1115833704@gmail.com> <A2BB90B33FFDF740876C5AAE307D83DB1C292D70@xmb-rcd-x05.cisco.com> <91BD27DC-D555-49C7-8B40-F74F4D8B596F@extremenetworks.com>
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Subject: Re: [VRRP] vrrp Digest, Vol 81, Issue 3
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Hi Thirumavalavan

Here are couple of points:

1) With something like "disable vrrp" or "shutdown vrrp" it will not be graceful as the router will treat it as a shutdown event (which is a break before you make approach) and the router will "Transition to the {Initialize} state". The backup router will wait for "Skew_Time" before it becomes master; So we probably will have traffic loss for a period approximately equal to "Skew_Time". Even with Default configuration this will be close to 609 ms which would be a duration long enough for to impact time sensitive applications (e.g. voice calls). For sure the actual failover time will depend upon the size of the Network and the switches in between but with the method proposed below we can try to improve that time.

2) This will also improve convergence in scenarios where we want the failover to trigger because of up uplink interface from the router going down (tracking interface and decrementing the priority).

I am not sure if you saw the modified proposal which was sent out today early morning. Here is the link to it in case you need it http://www.ietf.org/mail-archive/web/vrrp/current/msg01489.html

Thanks
~Anurag

-----Original Message-----
From: Thirumavalavan Periyannan [mailto:tperiyannan@extremenetworks.com] 
Sent: Friday, February 22, 2013 12:41 PM
To: Anurag Kothari (ankothar)
Cc: Peter Hunt; vrrp@ietf.org
Subject: Re: [VRRP] vrrp Digest, Vol 81, Issue 3

Hi Anurag,

If customer wants to do any maintenance work then they can do "disable vrrp" on MASTER Router which will generate VRRP Advertisement with "priority 0" and one among the backup router will become master based on the priority or higher interface IP addres.


Sent from my iPhone

On 22-Feb-2013, at 10:59 PM, "Anurag Kothari (ankothar)" <ankothar@cisco.com>; wrote:

> Hi Peter
>
> Please See my responses inline [Anurag]
>
> Thanks
> -Anurag
>
> -----Original Message-----
> From: Peter Hunt [mailto:pfhunt@gmail.com]
> Sent: Friday, February 22, 2013 11:59 AM
> To: Anurag Kothari (ankothar)
> Cc: Thirumavalavan Periyannan; vrrp@ietf.org
> Subject: Re: [VRRP] vrrp Digest, Vol 81, Issue 3
>
> Sorry to jump in here, but I'm having trouble understanding the motivation for the maintenance event.
>
> It seems like its behaviour is to relinquish mastership immediately to a backup if it exists, but remain master silently otherwise. Is that correct?
>
> [Anurag] The master will not remain silent it will keep sending Advertisements with Priority = 0 until some backup router takes over as Master.
>
> If so, why is that desirable behaviour? It seems to me that you would either want to take the node out of the vrrp cluster completely, or have it participate at a reduced priority. What situation makes a silent-but-active master preferable?
>
> [Anurag] Many mobile service providers disable preemption for VRRP as they do not like the idea of unplanned traffic switch when a router with higher priority comes up. They only want traffic to switch in the event of a failure or as part of a planned activity in a maintenance window.
> Now here is an example: A site has PE1 and PE2 configured to backup each other. Now if I want to perform any maintenance work on the say PE1 (Code upgrade / HW upgrade etc.) I want to take it out of the traffic path gracefully. Now the only way to Gracefully failover the traffic to PE2 is to configure preemption on it and reduce the priority on PE1 (or increase it on PE2) and remove it at the end of the maintenance work. But most service providers do not like the idea of touching (making changes to configuration) on both the boxes within the same maintenance window. So the idea here is to be able to failover the traffic to the backup router without enabling preemption on the Backup router.  If the backup router exists it will take over immediately if it doesn't exist the existing Master will continue to provide service. A lack of failover will indicate to the operator that backup is missing / not working and he will have to troubleshoot the situation.
>
> Peter
>
>
> On Feb 22, 2013, at 7:55 AM, "Anurag Kothari (ankothar)" <ankothar@cisco.com>; wrote:
>
>> Yes that is correct.
>>
>> The intention is to be able to switch the traffic to the backup router (with minimal traffic interruption) when preemption is not configured on the backup router without shutting down the interface or VRRP on Master.
>>
>> Thanks
>> ~Anurag
>>
>> -----Original Message-----
>> From: vrrp-bounces@ietf.org [mailto:vrrp-bounces@ietf.org] On Behalf 
>> Of Thirumavalavan Periyannan
>> Sent: Friday, February 22, 2013 8:56 AM
>> To: vrrp@ietf.org
>> Cc: vrrp@ietf.org
>> Subject: Re: [VRRP] vrrp Digest, Vol 81, Issue 3
>>
>> Hi Anurag,
>>
>> You meant to say that when we do graceful failover on VRRP Master then traffic needs switch to VRRP backup router without waiting for Master_Down_Interval time.
>>
>> Please correct me if I am wrong.
>>
>> Sent from my iPhone
>>
>> On 22-Feb-2013, at 5:11 PM, "vrrp-request@ietf.org"; <vrrp-request@ietf.org>; wrote:
>>
>>> If you have received this digest without all the individual message 
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>>> or, via email, send a message with subject or body 'help' to
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>>> When replying, please edit your Subject line so it is more specific 
>>> than "Re: Contents of vrrp digest..."
>>>
>>>
>>> Today's Topics:
>>>
>>> 1. Re: Proposal for Maintenance Event for VRRP [RFC-5798]
>>> (sreenatha)  2. Re: Proposal for Maintenance Event for VRRP [RFC-5798]
>>>    (Anurag Kothari (ankothar))
>>>
>>>
>>> --------------------------------------------------------------------
>>> -
>>> -
>>>
>>> Message: 1
>>> Date: Fri, 22 Feb 2013 09:55:35 +0530
>>> From: sreenatha <sreenatha.setty@ibtechnology.com>;
>>> To: "Anurag Kothari (ankothar)" <ankothar@cisco.com>;
>>> Cc: "vrrp@ietf.org"; <vrrp@ietf.org>;
>>> Subject: Re: [VRRP] Proposal for Maintenance Event for VRRP 
>>> [RFC-5798]
>>> Message-ID: <5126F33F.1080005@ibtechnology.com>;
>>> Content-Type: text/plain; charset="iso-8859-1"; Format="flowed"
>>>
>>> Hi Anurag,
>>>  Your proposal is:
>>>
>>> - If a Maintenance event is received, then:
>>>
>>> + Cancel the Adver_Timer
>>>
>>> + Send an ADVERTISEMENT with Priority = 0
>>>
>>> -endif // maintenance recv
>>>
>>>
>>>   And you mentioned that router need to send regular ADVERTISEMENT message till it receives the ADVERTISEMENT message from the backup router.
>>>
>>> "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."
>>>
>>> If Advert_Timer is cancelled, how regular ADVERTISEMENT messages are sent?
>>>
>>> So i am suggesting slight changes in the Proposal:
>>>
>>> - If a Maintenance event is received, then:
>>>
>>> + Change the router priority to 0
>>>
>>> + Send an ADVERTISEMENT with Priority = 0
>>>
>>> + Reset the Adver_Timer
>>>
>>> -endif // maintenance recv
>>>
>>> This will ensure that:
>>> 1. ADVERTISEMENT message with priority 0 is sent  immediately on receiving Maintenance event.
>>> 2. Master router will send regular Advertisement message till it receives the ADVERTISEMENT message from any backup routers.
>>>
>>> Thanks,
>>> Sreenatha Setty
>>>
>>>
>>>
>>>
>>> On 02/21/2013 10:12 PM, Anurag Kothari (ankothar) wrote:
>>>> 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: vrrp-bounces@ietf.org [mailto:vrrp-bounces@ietf.org] On 
>>>> Behalf Of sreenatha
>>>> Sent: Thursday, February 21, 2013 11:03 AM
>>>> To: vrrp@ietf.org
>>>> 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, vrrp-request@ietf.org wrote:
>>>>> If you have received this digest without all the individual 
>>>>> message attachments you will need to update your digest options in 
>>>>> your list subscription.  To do so, go to
>>>>>
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>>>>>
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>>>>> "Get MIME or Plain Text Digests?" to MIME.  You can set this 
>>>>> option globally for all the list digests you receive at this point.
>>>>>
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>>>>>
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>>>>>
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>>>>>   https://www.ietf.org/mailman/listinfo/vrrp
>>>>> or, via email, send a message with subject or body 'help' to
>>>>>   vrrp-request@ietf.org
>>>>>
>>>>> You can reach the person managing the list at
>>>>>   vrrp-owner@ietf.org
>>>>>
>>>>> When replying, please edit your Subject line so it is more 
>>>>> specific than "Re: Contents of vrrp digest..."
>>>>>
>>>>>
>>>>> Today's Topics:
>>>>>
>>>>>   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)"<ankothar@cisco.com>; 
>>>>> To:"vrrp@ietf.org"  <vrrp@ietf.org>;
>>>>> Subject: [VRRP] Proposal for Maintenance Event for VRRP [RFC-5798]
>>>>> Message-ID:
>>>>>   <A2BB90B33FFDF740876C5AAE307D83DB1C290327@xmb-rcd-x05.cisco.com>;
>>>>> 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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>>>>>
>>>>> ------------------------------
>>>>>
>>>>> _______________________________________________
>>>>> vrrp mailing list
>>>>> vrrp@ietf.org
>>>>> https://www.ietf.org/mailman/listinfo/vrrp
>>>>>
>>>>>
>>>>> End of vrrp Digest, Vol 81, Issue 1
>>>>> ***********************************
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>>> ------------------------------
>>>
>>> Message: 2
>>> Date: Fri, 22 Feb 2013 11:41:47 +0000
>>> From: "Anurag Kothari (ankothar)" <ankothar@cisco.com>;
>>> To: sreenatha <sreenatha.setty@ibtechnology.com>;
>>> Cc: "vrrp@ietf.org"; <vrrp@ietf.org>;
>>> Subject: Re: [VRRP] Proposal for Maintenance Event for VRRP 
>>> [RFC-5798]
>>> Message-ID:
>>>
>>> <A2BB90B33FFDF740876C5AAE307D83DB1C292974@xmb-rcd-x05.cisco.com>;
>>> Content-Type: text/plain; charset="us-ascii"
>>>
>>> Hi Sreenatha
>>>
>>> My bad, by cancel I meant reset the timer.
>>>
>>> I would prefer defining maintenance event itself as (or being triggered by) priority being set to 0 for a VRID. So probably we can rephrase the proposal as:
>>>
>>>
>>> - If a Maintenance event is received, then:
>>>
>>>
>>>
>>> + Send an ADVERTISEMENT
>>>
>>>
>>>
>>> + Reset the Adver_Timer to Advertisement_Interval
>>>
>>>
>>>
>>> -endif // maintenance recv
>>>
>>> Thanks
>>> -Anurag
>>>
>>> From: sreenatha [mailto:sreenatha.setty@ibtechnology.com]
>>> Sent: Thursday, February 21, 2013 11:26 PM
>>> To: Anurag Kothari (ankothar)
>>> Cc: vrrp@ietf.org
>>> Subject: Re: [VRRP] Proposal for Maintenance Event for VRRP 
>>> [RFC-5798]
>>>
>>> Hi Anurag,
>>> Your proposal is:
>>>
>>>
>>>
>>> - If a Maintenance event is received, then:
>>>
>>>
>>>
>>> + Cancel the Adver_Timer
>>>
>>>
>>>
>>> + Send an ADVERTISEMENT with Priority = 0
>>>
>>>
>>>
>>> -endif // maintenance recv
>>>
>>>
>>>
>>>
>>>
>>>  And you mentioned that router need to send regular ADVERTISEMENT message till it receives the ADVERTISEMENT message from the backup router.
>>>
>>>
>>>
>>> "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."
>>>
>>>
>>>
>>> If Advert_Timer is cancelled, how regular ADVERTISEMENT messages are sent?
>>>
>>>
>>>
>>> So i am suggesting slight changes in the Proposal:
>>>
>>>
>>>
>>> - If a Maintenance event is received, then:
>>>
>>>
>>>
>>> + Change the router priority to 0
>>>
>>>
>>>
>>> + Send an ADVERTISEMENT with Priority = 0
>>>
>>>
>>>
>>> + Reset the Adver_Timer
>>>
>>>
>>>
>>> -endif // maintenance recv
>>>
>>>
>>>
>>> This will ensure that:
>>>
>>> 1. ADVERTISEMENT message with priority 0 is sent  immediately on receiving Maintenance event.
>>>
>>> 2. Master router will send regular Advertisement message till it receives the ADVERTISEMENT message from any backup routers.
>>>
>>>
>>>
>>> Thanks,
>>>
>>> Sreenatha Setty
>>>
>>>
>>>
>>>
>>>
>>>
>>> On 02/21/2013 10:12 PM, Anurag Kothari (ankothar) wrote:
>>>
>>> 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: vrrp-bounces@ietf.org<mailto:vrrp-bounces@ietf.org>
>>> [mailto:vrrp-bounces@ietf.org] On Behalf Of sreenatha
>>>
>>> Sent: Thursday, February 21, 2013 11:03 AM
>>>
>>> To: vrrp@ietf.org<mailto:vrrp@ietf.org>
>>>
>>> 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, vrrp-request@ietf.org<mailto:vrrp-request@ietf.org> wrote:
>>>
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>>> Today's Topics:
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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)"<ankothar@cisco.com><mailto:ankothar@cisco.com>
>>>
>>> To:"vrrp@ietf.org"<mailto:vrrp@ietf.org>
>>> <vrrp@ietf.org><mailto:vrrp@ietf.org>
>>>
>>> Subject: [VRRP] Proposal for Maintenance Event for VRRP [RFC-5798]
>>>
>>> Message-ID:
>>>
>>>
>>> <A2BB90B33FFDF740876C5AAE307D83DB1C290327@xmb-rcd-x05.cisco.com><mai
>>> l t 
>>> o:A2BB90B33FFDF740876C5AAE307D83DB1C290327@xmb-rcd-x05.cisco.com>
>>>
>>> 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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