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

From: "Fabiana moreno" <fvmoreno@xxxxxxxxx>
Date: Sat, 12 Apr 2008 22:46:56 +0100
im trying to calculate the end to end delay....if i have the id i can determine what packet is missing

On 12/04/2008, Guy Harris <guy@xxxxxxxxxxxx> wrote:
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.

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