Re: DB Synchronization

[Rikki Nguyen <[e-mail]>]

You seem to be correct.  I missed the part about the netmasks.
The zero and negative-zero (0xff) has the same affect on
the checksum, hence they end up being the same.  I don't see
any other way of correcting this besides forcibly sending
LS-Requests for self-originated LSA's.

Parag Deshpande wrote:
> I ran a small program with the following values -
>
> In this case the checksums are always the same! because
> m1 & m2 are multiple of 8.
> m1= 16 m2 = 24. ( also 8, 32)
>
> CK_SUM({00, 00, 00, FF}, 4) = CK_SUM( {00,00,FF,FF}, 4)
> = CK_SUM( {00,FF,FF,FF},  4) = CK_SUM( {FF,FF,FF,FF}, 4)
> = 0xFFFF
>
> (It does not matter what N1 is)
>
> Or I am goofing up somewhere :-)
>
> Parag
>
> ----- Original Message -----
> From: Rikki Nguyen <[e-mail]>
> To: <[e-mail]>
> Sent: Friday, August 29, 2003 12:53 PM
> Subject: Re: DB Synchronization
>
>
>
>>Parag Deshpande wrote:
>>
>>>Hi,
>>>
>>>I had a doubt ->
>>>
>>>2 routers A and B have an ospf adjacency.
>>>
>>>Router A sends an ASExt lsa for network N1/m1 with LSID = N1.
>>>Then Router A goes down & comes up again & reoriginates
>>>ASExt lsa for network N1/m2 with LSID = N1 and then
>>>gets adjacent with Router B.
>>>
>>>**where m1 != m2 & they are multiple of 8. (/8, /16..)
>>>also assuming that all other parameters are same.
>>>
>>>However in this case the DB Exchange will fail to
>>>synchronize these LSAs bcoz they appear
>>>to be similar- LSID, SeqNum, Checksums being equal**
>>>and thus will have to wait for the LSA to get refreshed.
>>
>>The checksum is computed over the entire LSA body,
>>this includes the netmask.  Since the netmasks are
>>different, it would be difficult for the checksum
>>to be the same.
>>
>>
>>>I was wondering whether this can be resolved faster.
>>>
>>>Thanks
>>>Parag
>>>
>>
>