On Dec 6, 2007, at 11:06 AM, <[EMAIL PROTECTED]> <[EMAIL PROTECTED]> wrote:
Hello,
I have created an EtherSwitch model to replace the EtherLink.
However, I got two problems:
1) In original EtherLink model, each Interface has only one
txlink, so when Interface::recvPacket(packet) is called by
its peer, txlink->transmit(packet) is returned. But in
the EtherSwitch model, each Interface has N-1 txlinks(N is
# of systems), so function recvPacket(packet) must
determine
which txlink is needed to transmit the packet.
The idea is that each two endpoints should have an EtherInt. So each
system will have an EtherInt and then the switch should have a
separate EtherInt for each "port" that exists on the switch. The
probably should be connected with an EtherLink.
I tried to
find the destination information in the packet. I looked
through base/inet.hh and found the function dst() can
return
the destination address, so I wrote the following codes:
IpPtr p = IpPtr(packet);
uint32_t ip_address = p->dst();
But the simulator exited with error when it ran the
above codes. Can anyone know how to get the destination
information from the packet?
You should read the IEEE 802.1D ethernet standard. Not all packets
transfered across ethernet are IP packets. You need to route based on
MAC addresses, not on IP addresses. The switch model needs to keep a
list of MAC addresses behind each port and then when it receives a
packet it needs to find the appropriate port and send the packet to
it. To be complete the model also needs to detect when no port exists
and respond appropriately.
2) similar to the above problem. In original EtherLink model,
when Interface::isBusy() is called, it just returns
txlink->busy() since it has only one txlink. But in the
EtherSwitch model, isBusy doesn't know which txlink
is needed to transmit the packet and the worse is no packet
can be used to determine the destination. One feasible
solution is make sure all txlinks are free before a packet
is transmitted although only one txlink is used. My
question is how to modify the original code in order to
replace isBusy() by isBusy(packet).
I think this will be more clear when you read the above specification,
but the architecture should look something like this:
http://zeep.eecs.umich.edu/~saidi/etherswitch.pdf
Ali
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