Wireshark-users: Re: [Wireshark-users] No indication about UDP checksum

From: Jaap Keuter <jaap.keuter@xxxxxxxxx>
Date: Mon, 02 Feb 2009 07:26:55 +0100

Hi,

Then either the UDP packet was fragmented or the capture was limited to a
certain length, not including all data. In these cases also Wireshark can't
verify the checksum, hence can't say it's either good or bad.

Thanx,
Jaap

Yuxin Zhuang wrote:
> Hi, Jaap, 
> 
> Thanks for your reply!
> 
> But the content of Checksum is not 0x0000. The output is as follows:
> 	Checksum: 0xd87e
> 		Good Checksum: False
> 		Bad Checksum: False
> 
> I can't figure out whether the checksum is correct or not. Lots of other packets' checksum are not zero either and the result is similar.
> 
> Thanks,
> Yuxin
> 
> -----Original Message-----
> From: wireshark-users-bounces@xxxxxxxxxxxxx [mailto:wireshark-users-bounces@xxxxxxxxxxxxx] On Behalf Of Jaap Keuter
> Sent: 2009年2月2日 14:00
> To: Community support list for Wireshark
> Subject: Re: [Wireshark-users] No indication about UDP checksum
> 
> Hi,
> 
> In UDP the checksum is optional. So if it's set to 0x0000 that means it's not calculated by the sender and cannot be checked by the receiver.
> For Wireshark that results in "Checksum: 0x0000 (none)" and it can't be neither good or bad, since there's is no checksum.
> 
> Thanx,
> Jaap
> 
> Yuxin Zhuang wrote:
>> Hi,
>>  
>> While i'm analyzing some captured pkts, i notice that lots of UDP pkts 
>> have no indication on 'checksum' and both good and bad checksum are 
>> 'false'. What does this mean?
>>  
>> The output is as follows:
>>  
>>  
>> Thanks a lot!
>> Yuxin
>>