Re: [IPsec] Issue #177. (was: HA/LS terminology)

"Dan Harkins" <dharkins@lounge.org> Wed, 24 March 2010 07:45 UTC

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Date: Wed, 24 Mar 2010 00:46:04 -0700 (PDT)
From: "Dan Harkins" <dharkins@lounge.org>
To: "Yoav Nir" <ynir@checkpoint.com>
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Cc: Rodney Van Meter <rdv@sfc.wide.ad.jp>, "ipsec@ietf.org" <ipsec@ietf.org>, Melinda Shore <shore@arsc.edu>, Dan Harkins <dharkins@lounge.org>
Subject: Re: [IPsec] Issue #177. (was: HA/LS terminology)
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On Tue, March 23, 2010 7:24 pm, Yoav Nir wrote:
>
> On Mar 23, 2010, at 6:05 PM, Dan Harkins wrote:
>
>>
>>  Hi,
>>
>>  "hot standby" implies a box sitting ("hot") twiddling its thumbs doing
>> little but waiting for another box to fail ("standby"). It's the VRRP
>> model.
>
> And that's exactly what I want to describe. Well, not twiddling its
> thumbs. The standby is synchronizing state with the active member, but
> it's not doing any IKE or IPsec

  Well don't use such a limiting term to describe a behavior that is
not so limited. Not all HA is that small subset you want to describe.

>>  There is a HA model which supports dynamic load balancing as well as
>> active session failover. Nodes in such a cluster are not "standby". They
>> each have loads that they can shed and add to based upon some heuristic.
>> A neat attribute of such a system is that an IPsec SA can be established
>> on node A, move to node B after a while, and come back to A some time
>> later without any actual node failure. State moves around to keep the
>> cluster balanced.
>
> Failure is just used as an example of why a certain SA failed over to
> another member. It is by no means the only reason. Still, what you are
> describing is a model that provides both high-availability and load
> balancing, and that is the reason we're moving away from calling the first
> model "high availability".

  Of course it's not the only reason. But you're missing the point. The
point is that the reason doesn't matter! You want to describe a particular
reason-- the "master" crashed and all state went over to the "hot standby"--
not the generic concept of state moving.

  So don't call it "high availability" then. But "hot standby" is worse.

>>  I would very much prefer "session failover" to "hot standby" and a
>> mild preference of "load balancing" over "load sharing". An HA model
>> doing VRRP could be termed "session failover" but the HA model described
>> above really can't be called "hot standby". And load can be shared but
>> just sharing a load can result in a mis-balanced cluster if sessions on
>> one node terminate naturally and it sits doing little while another node
>> whose sessions haven't terminated is huffing-and-puffing. Balancing can
>> imply sharing but not vice versa.
>
> "Session failover" sounds to me more like a description of an event than a
> type of cluster.

  So what? Are you suggesting that a type of cluster that is not a
"hot standby" is not worthy of terminology in IPsecME?

  Your term is severely limiting. I like "session failover". If you don't
then come up with a term that generically describes HA and not the
particular style of HA that you are accustomed to.

  Dan.