tcp packet split

[Valdis.Kletnieks at vt.edu]

> On Sun, Jan 19, 2014 at 2:31 AM, <net.study.sea at gmail.com> wrote:

> And why it is possible for one packet to contain uncontinuous part of
> different  user protocol packets?

Whatever gave you the idea that's possible?  There's absolutely zero provision
in the Internet standards for one packet to carry data for multiple packets.
Not only are there no provisions folr multiple L3/4 headers in a packet, one of
the more interesting challenges for firewall designers is that a fragmented
packet may have *zero* L3/4 headers in it.

The only way you'd encounter this would be if you have packet encapsulation
on a VPN or similar tunnel, and it decided to pack multiple short packets
into a tunneling packet - but in that case, (a) the lower-level packet is
only carrying a stream of data and (b) the tunnelled stream is, in general,
unaware that it's being tunnelled (and thus is carrying around full L1-L4
headers).

And, in general, VPNs don't actually pack packets like that - it tends to
totally screw up RTT and jitter calculations.


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