Hi Sudhin,

You may want to have a look at this draft:
https://tools.ietf.org/html/draft-rabadan-bess-evpn-ac-df-02

Provides a solution for your use-case in EVPN, without any control plane 
changes compared to RFC7432.
There are already implementations doing that.

Thanks.
Jorge

From: BESS <[email protected]<mailto:[email protected]>> on behalf of 
sudeep g ggg <[email protected]<mailto:[email protected]>>
Date: Wednesday, November 25, 2015 at 11:18 AM
To: "[email protected]<mailto:[email protected]>" 
<[email protected]<mailto:[email protected]>>
Cc: "[email protected]<mailto:[email protected]>" 
<[email protected]<mailto:[email protected]>>, 
"[email protected]<mailto:[email protected]>" <[email protected]<mailto:[email protected]>>, 
"[email protected]<mailto:[email protected]>" 
<[email protected]<mailto:[email protected]>>
Subject: Re: [bess] REG: draft-mohanty-bess-evpn-df-election-02

Hi Satya,

Let me thank you for your mail,it is much appreciated.You will take this in to 
account in next revision, much appreciated so that all will be in same page. 
One more thought though just a random thought.I would like to bring your kind 
attention.Since section 7.1 you clearly explains that you are not taking in to 
consideration about vlan mis configuration. My thought
requires no answers from your side.But I would like to bring one case in to 
your frame of mind just sharing it.Once again big thank you for your reply.

Section 7.1

Observe that currently the VLANs are derived from local configuration
and the FSM does not provide any protection against misconfiguration
where same EVI,ESI combination has different set of VLANs on
different participating PEs or one of the PEs elects to consider
VLANs as VLAN bundle and another as separate VLANs for election
purposes (service type mismatch).

for example PE1 loopback 150.1.1.1 PE2 loopback 150.1.2.2

PE1 has vlan 2,3,4 PE2 has vlan 3,4

so DF election at present V mod N so PE1 will be DF in PE1 calculation.
in PE2 DF calculation V mod N. PE2 will be DF. So in short both PE will be DF 
for a EVI.

Regards,
Sudhin Jacob



On Wed, 25 Nov 2015 03:42:00 +0530 "Satya Mohanty (satyamoh)" wrote
>





Hi Kishore/Sudhin,






From: Kishore Tiruveedhula

Date: Tuesday, November 24, 2015 12:42 PM

To: smohanty mohanty , "Patrice Brissette (pbrisset)" , sudeep g ggg ,
"[email protected]<mailto:[email protected]>"

Subject: Re: [bess] REG: draft-mohanty-bess-evpn-df-election-02












Please see below inline…[Kishore].









1. When a new PE comes in the MH segment.


[Satya] Yes, New PE needs to wait for 3 sec. According to RFC 7438, the 
receiving PEs also need to wait for 3 secs. But, ideally, a PE that is going 
from DF to non-DF or non-DF to non-DF should become the non-DF rightaway. Only 
the
PE that is going DF really needs to wait for 3 secs. This is not explicitly 
spelled out in the draft but we are thinking along these lines.





[Kishore] Yes. The new PE need to wait for 3 seconds, but if new PE receives 
the type 4 route from the redundant PE before 3 seconds, the new PE can just 
move to DF immediately (if it becomes DF) just after receiving the type 4 
without waiting for the
3 seconds timer expiry because the otherredundant PE might have moved to Non-DF 
as there is no 3 seconds timer on the other PE which is moving from DF to 
Non-DF.
It is good idea to explicitly spell out this in this draft.




[Satya] Right. We will spell this out in the next version.












[Satya]Now, delay of BGP updates is not dependent on the above behavior. That 
depends on the network topology and queueing/processing at intermediate nodes.
With HRW, a PE coming up will result in minimal disruption of the established 
DF for various vlans (bundles) as opposed to RFC 7438 mod-based.





[Kishore] If the BGP update processing takes more time on one PE and receives 
less time from RR on the other PE, then it may be possible of both PE may 
become DF or Non-DF, so the timer value should be chosen large enough in this 
case.




[Satya] The problem is there is no "cure-all" timer value that will guarantee 
this behavior.
There was a ack based draft sometime back, but it would have introduced 
considerable overhead that caused complications.







Thanks,
Kishore









Thanks,

--Satya
























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