Subject: Indication LSA impact

From: Kalyan Bade <[email-masked]>
Date: Tue, 10 May 2005 00:13:17 -0700

Folks,

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?

Thanks,
Kalyan.

---

From: Acee Lindem <[email-masked]>
Date: Tue, 10 May 2005 08:11:08 -0400

Hi Kaylan,

>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 
additional
protocol specification and state.

Thanks,
Acee