Quoting Guy Harris <gharris@xxxxxxxxxxxx>:
> On Thu, Jan 04, 2001 at 08:16:27PM +0100, Michael
Tüxen wrote:
> > Having an SCTP packet with two M3UA packet a
protocol tree like
> >
> > IP
> > SCTP
> > M3UA
> > M3UA
> >
> > would suggest that M3UA is transported inside M3UA.
>
> It *might* suggest that it's transported inside M3UA,
or it might not.
>
> We already have protocols where you can have more than
one PDU within a
> frame; consider, for example, the OSI CLNP - I've seen
one capture file
> that has at least one CLNP PDU with two COTP PDUs in
it.
>
> We currently display that as
>
> Frame
> IEEE 802.3
> LLC
> CLNP
> COTP
> COTP
>
> We do the same with the NetBIOS-over-TCP session
service - there can be
> more than one NBSS PDU within a TCP segment. That
could theoretically
> occur with *any* protocol that runs atop TCP, as TCP
segment boundaries
> aren't visible to the protocol above TCP.
>
> I'd be inclined to show something like
>
> > The problem is, that SCTP supports the bundling of
multiple M3UA packets
> in
> > on SCTP packet. Furthermore in the SCTP packet there
are some bytes
> belonging
> > to SCTP, then the M3UA stuff of packet 1, then SCTP
bytes and then the
> M3UA
> > stuff of packet 2 and so on.
> > So the byte sequence does not correspond to the
linear structure of the
> > protocol stack.
>
> as
>
> ...
>
> SCTP
> M3UA
> SCTP
> M3UA
>
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>
OK, let us think about the last solution. When starting
dissecting the SCTP packet I create a sctp_tvb. Now
after some processing, I have a parameter_tvb,
a subset of sctp_tvb, when I detect that it contains
a M3UA packet. Then I have to set the length of
the SCTP tree accoring this distinction. So can I
calculate the offset of parameter_tvb inside sctp_tvb?
Best regards
Michael
