PLAP(3) PLAP(3)
NAME
plap - USR/3Com Edgeserver packet bus link access protocol
SYNOPSIS
bind -a '#X' /net
/net/plap/clone
/net/plap/n/ctl
/net/plap/n/data
/net/plap/n/local
/net/plap/n/remote
/net/plap/n/status
/net/plap/n/listen
DESCRIPTION
The plap driver serves a three-level directory giving access
to the link level protocol used by an Edgeserver card to
communicate with other cards in a USR/3Com chassis. On
first attach (usually by a bind(1) to /net) the driver opens
a connection to the packet bus device #Y described in
pbus(3). It multiplexes that connection using a specialised
member of the LAP family of protocols.
The top level directory contains a single directory naming
the protocol, plap. It contains a clone file and a set of
conversation directories numbered from 0 to 127; only active
conversation directories are present.
Opening the clone file allocates a new conversation direc-
tory n. The file descriptor will point to the control file,
ctl, of that directory. Reading the file returns a text
string giving the conversation number.
Each conversation directory contains six files. The connec-
tion is controlled by writing text strings to the ctl file.
Once a connection has been established, data is exchanged
with the remote peer by reading and writing the data file.
A plap address has the form:
[ slot. ] chan!sap
where slot is a chassis slot number, chan is a logical chan-
nel (eg, a modem number), and sap is a number representing a
`service access point'.
The following control messages are supported:
connect remoteaddr [ localaddr ]
Make a connection to the given remote address (of the
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PLAP(3) PLAP(3)
form given above). If a local address is not speci-
fied, the system will assign an unused address dynami-
cally (the local chassis slot number is of course
fixed). Connect fails if the connection is already
announced or connected, or localaddr is already in use.
announceaddress
Set the local address to address and accept incoming
calls to that address. If no address is specified, all
incoming calls to addresses not explicitly announced
will be accepted by this connection. Announce fails if
the connection is already announced or connected, or
the local address specified is already in use.
The remote and local files contain the remote and local
addresses for the connection in the full address form
slot.chan!sap. The status file returns a line giving the
directory name, number of active opens, and the state of the
connection.
A process listens for incoming calls by opening the listen
file using sys-open(2). The open will block until a call
arrives, when it will return a file descriptor open on the
ctl file of the newly accepted connection, which can be read
to find the directory number and thus the other files.
The device follows the conventions that allow dial, announce
and listen of dial(2) to do the work needed to establish and
manipulate network connections.
SOURCE
/os/pc/devplap.c
SEE ALSO
pbus(3)
BUGS
The driver cannot be included in the public distribution.
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