Wireshark · Wireshark-users: Re: [Wireshark-users] Fwd: sequence number and packet id

[Guy Harris <guy@xxxxxxxxxxxx>]

Fabiana moreno wrote:
> Thank you very much for your help. I have been reading about all this 
> the whole day, it´s just confusing somehow. I just need my packets 
> fragmented so i can have the packet id so i can do some 
> calculations....

What are the calculations you're trying to do, and why you need a packet ID?

> From what i have read the kernel version 2.6 dont 
> fragment packets

No.

The 2.6 kernel will fragment packets if necessary.

Furthermore, even if it - or any *OTHER* IP implementation - sends an IP 
packet that doesn't have the "don't fragment" bit set, it can't assume 
that some *other* host along the route to the destination won't fragment 
the packet, so, regardless of whether the host sending the packet 
fragments it, if the packet doesn't have "don't fragment" set, it has to 
give the packet as close to a unique IP ID as it can.

However, if the "don't fragment" bit is set, it doesn't have to give the 
packet a unique IP ID - and at least some versions of the Linux kernel, 
and possibly some versions of some other kernels, don't give those 
packets unique IP ID's.