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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 directory
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 connection 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 channel (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 form given above).
If a local address is not specified, the
system will assign an unused address dynamically
(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.





PLAP(3
)
Rev:  Tue Mar 31 02:42:38 GMT 2015