Re: Indication LSA impact

Acee Lindem <acee@CISCO.COM> Tue, 10 May 2005 12:15 UTC

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From: Acee Lindem <acee@CISCO.COM>
Subject: Re: Indication LSA impact
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Hi Kaylan,

Kalyan Bade wrote:

>I was going through rfc 1793 (demand circuit extensions for OSPF) and
>have a question regarding the generation of indication LSAs and its
>impact on the LSAs created/flooded.
>Suppose if we have three routers as shown in the setup below.
>R0 ------ R1 ------ R2
>   Area X    Area Y 
>Say if R0 is a DC uncapable router, the area X is considered DC
>uncapable. Which means that none of the routers in area X can generate
>an area scope/AS scope LSAs with DoNotAge bit set. 
>And as per the spec, an indication LSA is generated in area Y and this
>makes the area Y also as DC uncapable. So, my question is what is the
>rationale behind making area Y as DC uncapable? I understand that any
>router in area Y shouldn't generate an AS scope LSA with DoNotAge bit
>set, but why should that hold to area scope LSA's?

I don't recall all the discussions surrounding this draft. However, I 
suspect it was a design
choice to simplify the backward compatibility mechanism. On the surface, 
I see no
reason why what you are suggesting could not have been done with some 
protocol specification and state.