Re: [OSPF] draft-acee-ospfv3-lsa-extend-00

Anton Smirnov <> Fri, 03 May 2013 17:27 UTC

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Date: Fri, 03 May 2013 17:53:49 +0200
From: Anton Smirnov <>
Organization: Cisco Systems
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To: Acee Lindem <>
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Subject: Re: [OSPF] draft-acee-ospfv3-lsa-extend-00
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    Hi Acee,

 > As far as calling it OSPFv4, I don't think we need to do this since
 > only the encoding of the LSAs change.

Yes I understand the reasoning but that is exactly where I have a 
problem with this approach.
As it is said - “For every problem there is a solution which is simple, 
fast and wrong.”
I believe approach taken while architecturing OSPFv3 was exactly that - 
simple, fast and wrong. Exactly the reason why we have to talk right now 
about creating non-backward-compatible change is because OSPFv3 
inherited from OSPFv2 rigid LSA structure in the name of simplicity.

I just want to make sure we will not repeat the same mistake again - 
create non-backward-compatible revision of the protocol which missed 
opportunity to implement anything but only single change.

So understand me right - I fully agree with you that OSPFv3 is not 
extendable, I have no big problem with semantics of proposed extended 
LSAs, I am even ready to accept non-backward-compatible change (just 
because I do not see any other exit from dead end we cornered ourselves 
But I have big problem with approach "lets do minimum changes possible". 
Solution - since it is non-backward-compatible - must first of all be 
RIGHT and only then, if possible, simple.

So what I am advocating is - lets acknowledge protocol needs major 
non-backward-compatible uplift and see what else can be fit into such 
protocol upgrade. Yes, it is going to be slow - but then result will be 


On 05/03/2013 05:14 PM, Acee Lindem wrote:
> Hi Anton,
> Thanks for introducing the draft - I had meant to do it but am chronically pressed for time. Here is the link:
> You are correct that the draft does require a deployment upgrade. A mixed deployment will require separate OSPFv3 routing domains and multiple OSPFv3 instances at least at the boundaries. The alternative was to require both the existing LSAs and the Extended-LSAs to be originated in mixed deployments. This adds quite a lot of complexity and will not be scalable in many networks. It is definitely possible but is the is the sort of backward compatibility mechanism people who don't write or maintain routing software propose.
> As far as calling it OSPFv4, I don't think we need to do this since only the encoding of the LSAs change. We were careful not to change the LSA semantics in the interest of rapid acceptance, implementation, and, hopefully, deployment. I believe the OSPFv3 moniker should be reserved for a version of the protocol with far more changes (including deprecation of virtual links ;^).
> Thanks,
> Acee
> On May 3, 2013, at 9:01 AM, Anton Smirnov wrote:
>>    Hi all,
>>    I saw this draft was published a few days ago and I wanted to discuss the approach taken by authors. In brief, this draft deeply changes OSPFv3 by totally reworking LSA encodings but stops short of calling it a new version of OSPF protocol. Per draft routers supporting new LSA encodings do not mix with RFC 5340 OSPFv3 routers and do not talk to them. So from deployment point of view section of the draft describing backward compatibility can be reduced to simply "Totally not backward compatible".
>>    I think no one will object that OSPFv3 rigid LSA format became big obstacle in introducing new features and even simply catching up with ISIS.
>>    I personally fully agree that OSPFv3 has to be deeply reworked.
>>    But in my opinion this draft is presenting OSPFv4 without calling it so - and carries into the new version of the protocol some outdated features of OSPFv2.
>>    Isn't it a time to admit that OSPFv3 is failure of epic proportions? And to admit that stance 'to introduce minimum changes into the protocol' taken when developing OSPFv3 architecture was deeply flawed, sacrificed long-term benefits of introducing new protocol version to short-term benefits of quick standardization and will continue causing difficulties unless addressed (with LSA encodings being the most obvious but not the only one)?
>> --
>> Anton
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