Les,

> When an LSP is received, the receiving IS validates the checksum. If the 
> checksum is invalid, the LSP is discarded – which means the transmitter will 
> be forced to retransmit (SRM bit is not cleared).


True, but irrelevant.


> So an LSP with invalid checksum will never be placed in the receiver’s 
> database.  ISO 10589 7.3.14.2e.


True, but also irrelevant.


> Which means if a CSNP entry with that invalid checksum is received the 
> receiver will not find a match in its database and will follow ISO 10589 
> 7.3.16.2.


We are not discussing CSNPs with invalid checksums.


> If an LSP is received, checksum is validated, but the data in the LSP is in 
> some way different than what is in the LSP in the transmitters DB, then we 
> still have the actual TLV content which is in some way corrupted. In a robust 
> implementation the corrupt information would be detected and not used.


We are not discussing LSP corruption here.


> Now, you seem to be trying to equate this last case with a hash collision in 
> an HSNP where the range of LSPs covered by an HSNP advertisement incorrectly 
> collides with the hash calculated by the receiver over the same range. But in 
> such a case, we have one or more LSPs which have not been synced between the 
> two systems. Either an LSP doesn’t exist at all in one database or a 
> different version of that LSP exists – and you are trying to say that lack of 
> an entire LSP is equivalent to having the same LSP in both databases when 
> some bits in the data are different.


No.  That’s not what I’m saying at all.  Please reread my mail. The point is 
simple: CSNP’s are not 100% reliable. There can be checksum collisions.


> But I am not warming to the idea of introducing new ways to compromise 
> flooding integrity in the name of efficiency.


Your opinion is duly noted.  We are not compromising flooding integrity at all, 
but if you will not discuss reality, I cannot help you.

Regards,
Tony


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