Subject: Fragment Header

From: "Vishwas Manral" <[email-masked]>
Date: Thu, 24 Nov 2005 03:24:10 -0800

Hi folks,

I have a doubt regarding the fragment header. Why do we need the M flag
in the "fragment header" at all for IPv6? Having the fragment header
itself would tell it's a fragment and would distinguish between the
first fragment and a non-fragment.

In IPv4 we did not have a fragment header, so the M flag was logical to
have for distinguishing the first and a non fragment.

That said; how should the case where we have the fragment header and
both the Fragment Offset and the M flag is 0 be treated?

Thanks,

Vishwas

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From: "Radhakrishnan.S" <[email-masked]>
Date: Thu, 24 Nov 2005 18:01:37 -0800

That said; how should the case where we have the fragment header and 
both the Fragment Offset and the M flag is 0 be treated?
=> The one and only fragment.  :-) Doesnt make sense unless u want to 
test the reassembling capability of the receiver of the fragments. The 
presence of a fragment header is used in NAT-PT IPv4->IPv6 to indicate 
that the packet is fragmentable. (case where DF bit is NOT set in IPv4 
header).

Why do we need the M flag in the "fragment header" at all for IPv6? 
Having the fragment header itself would tell it's a fragment and would 
distinguish between the first fragment and a non-fragment.
=> M flag is used to distinguish last frag from others!!!! Its used for 
identifying the last frag when computing the length during reassembly.

>
> Vishwas Manral wrote:
>
>> Hi folks,
>>
>>  
>>
>> I have a doubt regarding the fragment header. Why do we need the M 
>> flag in the "fragment header" at all for IPv6? Having the fragment 
>> header itself would tell it's a fragment and would distinguish 
>> between the first fragment and a non-fragment.
>>
>>  
>>
>> In IPv4 we did not have a fragment header, so the M flag was logical 
>> to have for distinguishing the first and a non fragment.
>>
>>  
>>
>>------------------------------------------------------------------------
>>