Re: loss of original packet type info when tracing multiple protocols.

[Sjoerd Janssen <s.a.janssen@student.utwente.nl>]

Hi, thanks for your fast reply. You're right. But what do you think would be the
best solution in case I do wish to use the ns/cmu trace objects to trace Packets
at mulitple protocol layers?

regards, Sjoerd Janssen.



Satish Kumar wrote:

> Only packets generated by the mac-802.11 protocol such as RTS, CTS and ACK
> packets have PT_MAC as the packet type in the common header (if you look at
> mac-802_11.cc, you'll notice the packet type is set to PT_MAC only in sendRTS,
> sendCTS and sendACK methods). I dont think the packet type is changed to
> PT_MAC for packets generated by higher layer protocols.
>
> Satish
>
> > Hi,
> >
> > - How does one retain the original information in the common header -
> > the packet type being the most important- when using nodes consisting of
> > multiple protocol layers and tracing for some of these layers is
> > required?
> >
> > Consider for example a node containing a MAC layer and a TCP agent.. The
> > ns/cmu trace objects generate their traces by looking at the packet type
> > field in the common header. For a MAC packet, the type therefore needs
> > to be changed from PT_TCP  to PT_MAC in the sending MAC object (I know
> > this is being done in mac-802_11.cc when a Packet is passed to the
> > channel). On the receiving MAC side, the packet type should be changed
> > back to PT_TCP but I don't see how this information can be retained. I
> > also don't see how / if  this is being done by the MAC object in
> > mac-802_11.cc
> >
> > I guess there are ways to avoid it, e.g. packing the original (TCP/IP)
> > packet into the data field of the Packet transmitted by MAC (and
> > unpacking at the MAC receiver) or using an additional header to store
> > the information contained in the original common header,  but I'd really
> > like to know how the people from CMU did this in mac-802_11
> >
> > Regards, Sjoerd Janssen.
> >
> >
> >
> >
> >