I agree with Robert.

Thanks,
Acee

> On Apr 23, 2025, at 8:47 AM, Robert Raszuk <[email protected]> wrote:
> 
> Hi Roger,
> 
> > But lets say some intermediate router (with a non-pleasant intention) 
> > modifies the checksum to a larger value before flooding it. 
> 
> My understanding is that both OSPF and ISIS do not have any protection from 
> insider's attacks. They are completely vulnerable protocols (modulo 
> authentication). That means that once you let a bad guy into the pool the 
> game is over. 
> 
> If I recall that check you quote in selecting which flooded LSA with the same 
> sequence number should be used is there just for area computational 
> consistency (ie. to make sure the very same LSA is used by all nodes in a 
> flooding scope). 
> 
> Thx,
> Robert
> 
> 
> On Wed, Apr 23, 2025 at 2:27 PM Roger David 
> <[email protected]> wrote:
> Dear Authors,
>  Greetings !
>  I have a question on the highlighted text of the RFC (see snip below) where 
> it clarifies that Router should select the LSA with larger checksum as the 
> most recent one.
>  As I know, originator router is the one that initializes the checksum of the 
> LSA and this shall not be modified by any intermediate routers during 
> flooding. 
>  So in an ideal situation, all routers in the network would receive this LSA 
> with the exact same checksum.
>  But lets say some intermediate router (with a non-pleasant intention) 
> modifies the checksum to a larger value before flooding it. It could cause 
> entire network to believe that this instance of the LSA is the most recent 
> one.
>  Could you pls. clarify or correct my incorrect understanding.
>   <image001.png>  Roger David
> Architect, Verification Engineering
> Reliable Tech Park | Navi Mumbai, India
> Mobile: +91 8308227212 
> <image002.png>   
> 
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