Re: RFC 2370 Update and a Proposed Change to Stub Area Behavior

Acee Lindem <acee@CISCO.COM> Tue, 16 August 2005 01:08 UTC

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Date: Mon, 15 Aug 2005 21:08:39 -0400
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From: Acee Lindem <acee@CISCO.COM>
Subject: Re: RFC 2370 Update and a Proposed Change to Stub Area Behavior
To: OSPF@PEACH.EASE.LSOFT.COM
In-Reply-To: <43010905.8070208@cisco.com>
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Hi Russ,

Russ White wrote:

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>First, I'll comment that I believe stub areas are still useful....
>
>  
>
>>If an application requires an area flooding scope, typically its LSA will
>>have the U-bit set so that the LSA be flooded as if it was understood and
>>avoiding the requirement that all routers understand the new LSA. With the
>>current specification in 2740, we cannot define new LSA with area flooding
>>scope for Stub / NSSA unless the U-bit is clear therefore this cause two
>>issues
>>
>>- We cannot have incremental deployment for a given application
>>- We would be defining two LS type for the same application as U-bit will be
>>set for regular areas and U-bit will be clear for Stub/ NSSA where all
>>routers have to understand the new LSA
>>    
>>
>
>Correct.
>  
>
I agree completely here.

>I do see some merit in suggesting that an implemenation MAY filter
>unknowns at a stub area ABR, as long as the network implementor is
>willing to accept the possible negative consequences from this action.
>  
>
For stub areas, the ABR still won't allow any AS scoped LSAs to enter 
the area. The LSAs
in question are always understood and originated by at least one router 
in the stub or NSSA
area.

Thanks,
Acee

>:-)
>
>Russ
>
>- -- 
>riw@cisco.com CCIE <>< Grace Alone
>
>
>
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