atmtcp - set up ATM over TCP connections
atmtcp [-d] [-v] command ...
The main purpose of atmtcp is to establish TCP connections and to
configure them as virtual ATM devices. Such pairs of "ATM over TCP"
devices are connected as if they were real ATM adapters linked by a
cable or fiber, i.e. SDUs sent on a given VPI/VCI are received at the
other end on the same VPI/VCI.
Virtual interfaces and ATM over TCP connections are called links.
Other link types supported by atmtcp are real interfaces, files for
recording and playback of ATM traffic, and printing a hex dump of the
PDU content on standard output. Any pair of such links can be connected
with atmtcp. If additional links are attached to such a connection,
they send to all other links, except to the first link and the
respective sender, and they receive from all other links.
atmtcp can operate with two types of virtual interfaces: ephemeral or
persistent. By default, atmtcp interfaces are ephemeral. When the
atmtcp process that created an interface terminates, the virtual ATM
device is removed as soon all VCs are closed. However, if the interface
was previously created as a persistent interface, only the
communication stops, but the interface and all VCs on it remain intact.
Attempts to send data on an atmtcp interface in this state fail
silently, i.e. the interface behaves just like a real ATM interface
without a wire. A new atmtcp process can then attach to the interface
and resume operation. Persistent interfaces need to be removed
If atmtcp has any readable links after processing the command line, it
enters a loop to perform the data forwarding. If no readable links have
been specified, atmtcp terminates after processing the command line. If
any setup operation fails, atmtcp terminates at this point and does not
attempt to cancel previous operations (e.g. creation of permanent
-d print detailed progress information on standard error.
-v print some progress information on standard error.
-V print version number of atmtcp on standard output and exit.
create a persistent interface. If no interface number is
specified, atmtcp uses the default value 0.
remove a persistent interface. If the interface is still in use,
it is marked as ephemeral and will be removed as soon as all VCs
are closed. If no interface number is specified, atmtcp uses the
default value 0.
link to the corresponding virtual (ATM over TCP) interface. If
no interface number is specified, the kernel assigns the first
link to the corresponding ATM interface. If no interface number
is specified, atmtcp uses the default value 0. If a link
requests that a VC be opened, atmtcp will attempt to open a VC
with the specified QoS parameters on that interface. If the
operation succeeds, data can be sent or received on that VC. If
the operation fails, an error code is returned to the requester.
Note that only data arriving on open VCs can be received and
that a real ATM interface never initiates a connection. atmtcp
can share ATM interfaces with other applications.
connect host [port]
connect to an instance of atmtcp running on the specified host.
If the port argument is omitted, atmtcp uses the default port
switch host line [port]
like connect, but connects to an ATM over TCP "switch" and
selects the specified virtual line.
listen for an incoming ATM over TCP connection. If the port
argument is omitted, atmtcp uses the default port 2812. atmtcp
waits until the connection is established. Only one connection
is accepted per listen command.
like listen, but run in background after beginning to listen.
read file [stream]
play back all streams from the specified file. If a stream
number is specified, only that stream is played back.
record the traffic of all links in the specified file. The PDUs
from each link are stored in a stream with the same number as
print print a hex dump of the content of all received PDUs on standard
bg continue to run in background (i.e. in a forked child process).
wait for the specified number of seconds. If no time is
specified, atmtcp waits for a newline on standard input.
Due to recent protocol changes, atmtcp is currently not compatible with
the ATM over TCP "switch".
Only AAL SDUs are exchanged, no segmentation or reassembly is
performed. That implies that using different AALs (e.g. AAL5 and AAL0)
on either side will reveal limitations of this emulation.
The atmtcp process needs to run during the the whole lifetime of the
Create a pair of virtual ATM over TCP interfaces on the local host and
# session A
atmtcp virtual listen
# session B
atmtcp virtual connect localhost
Create virtual interface 1, connect it to real ATM interface 0, then
start atmsigd on the virtual interface, and log all the traffic in a
atmtcp virtual 1 real 0 write /tmp/log
Take the previously created file and examine the traffic sent from
atmsigd using saaldump:
# session A
atmtcp virtual 1 read /tmp/log 0 wait
# session B
# press [Enter] in session A
Werner Almesberger, EPFL ICA <Werner.Almesberger@epfl.ch>