404 lines
11 KiB
Groff
404 lines
11 KiB
Groff
.\"
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.\" Copyright (c) 2001-2003
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.\" Fraunhofer Institute for Open Communication Systems (FhG Fokus).
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" Author: Hartmut Brandt <harti@FreeBSD.org>
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.\"
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.\" $FreeBSD$
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.\"
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.\" ng_sscop(4) man page
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.\"
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.Dd October 24, 2003
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.Dt NG_SSCOP 4
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.Os
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.Sh NAME
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.Nm ng_sscop
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.Nd netgraph SSCOP node type
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.Sh SYNOPSIS
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.In netnatm/saal/sscopdef.h
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.In netgraph/atm/ng_sscop.h
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.Sh DESCRIPTION
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The
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.Nm sscop
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netgraph node type implements the ITU-T standard Q.2110.
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This standard describes
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the so called Service Specific Connection Oriented Protocol (SSCOP) that
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is used to carry signalling messages over the private and public UNIs and
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the public NNI.
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This protocol is a transport protocol with selective
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acknowledgements, and can be tailored to the environment.
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This implementation is a full implementation of that standard.
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.Pp
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After creation of the node, the SSCOP instance must be created by sending
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an
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.Dq enable
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message to the node.
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If the node is enabled, the SSCOP parameters
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can be retrieved and modified and the protocol can be started.
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.Pp
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The node is shut down either by a
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.Dv NGM_SHUTDOWN
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message, or when all hooks are disconnected.
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.Sh HOOKS
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Each
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.Nm sscop
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node has three hooks with fixed names:
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.Bl -tag -width ".Va manage"
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.It Va lower
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This hook must be connected to a node that ensures
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transport of packets to and from the remote peer node.
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Normally this is a
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.Xr ng_atm 4
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node with an AAL5 hook, but the
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.Nm sscop
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node is able to work on any packet-transporting layer, like, for example,
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IP or UDP.
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The node handles flow control messages received on
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this hook: if it receives a
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.Dv NGM_HIGH_WATER_PASSED
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message, it declares the
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.Dq "lower layer busy"
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state.
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If a
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.Dv NGM_LOW_WATER_PASSED
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message is received, the busy state is cleared.
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Note that the node does not
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look at the message contents of these flow control messages.
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.It Va upper
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This is the interface to the SSCOP user.
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This interface uses the following message format:
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.Bd -literal
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struct sscop_arg {
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uint32_t sig;
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uint32_t arg; /* opt. sequence number or clear-buff */
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u_char data[];
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};
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.Ed
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.Pp
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The
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.Va sig
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field
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is one of the signals defined in the standard:
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.Bd -literal
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enum sscop_aasig {
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SSCOP_ESTABLISH_request, /* <- UU, BR */
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SSCOP_ESTABLISH_indication, /* -> UU */
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SSCOP_ESTABLISH_response, /* <- UU, BR */
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SSCOP_ESTABLISH_confirm, /* -> UU */
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SSCOP_RELEASE_request, /* <- UU */
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SSCOP_RELEASE_indication, /* -> UU, SRC */
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SSCOP_RELEASE_confirm, /* -> */
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SSCOP_DATA_request, /* <- MU */
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SSCOP_DATA_indication, /* -> MU, SN */
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SSCOP_UDATA_request, /* <- MU */
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SSCOP_UDATA_indication, /* -> MU */
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SSCOP_RECOVER_indication, /* -> */
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SSCOP_RECOVER_response, /* <- */
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SSCOP_RESYNC_request, /* <- UU */
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SSCOP_RESYNC_indication, /* -> UU */
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SSCOP_RESYNC_response, /* <- */
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SSCOP_RESYNC_confirm, /* -> */
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SSCOP_RETRIEVE_request, /* <- RN */
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SSCOP_RETRIEVE_indication, /* -> MU */
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SSCOP_RETRIEVE_COMPL_indication,/* -> */
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};
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.Ed
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.Pp
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The arrows in the comment show the direction of the signal, whether it
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is a signal that comes out of the node
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.Pq Ql -> ,
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or is sent by the node user to the node
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.Pq Ql <- .
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The
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.Va arg
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field contains the argument to some of the signals: it is either a PDU
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sequence number, or the
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.Dv CLEAR-BUFFER
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flag.
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There are a number of special sequence numbers for some operations:
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.Pp
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.Bl -tag -width ".Dv SSCOP_RETRIEVE_UNKNOWN" -offset indent -compact
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.It Dv SSCOP_MAXSEQNO
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maximum legal sequence number
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.It Dv SSCOP_RETRIEVE_UNKNOWN
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retrieve transmission queue
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.It Dv SSCOP_RETRIEVE_TOTAL
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retrieve transmission buffer and queue
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.El
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.Pp
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For signals that carry user data (as, for example,
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.Dv SSCOP_DATA_request )
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these two fields are followed by the variable sized user data.
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.Pp
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If the
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.Va upper
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hook is disconnected and the SSCOP instance is not in the idle
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state, and the
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.Va lower
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hook is still connected, an
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.Dv SSCOP_RELEASE_request
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is executed to release the SSCOP connection.
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.It Va manage
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This is the management interface defined in the standard.
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The data structure used here is:
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.Bd -literal
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struct sscop_marg {
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uint32_t sig;
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u_char data[];
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};
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.Ed
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.Pp
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Here
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.Va sig
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is one of
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.Bd -literal
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enum sscop_maasig {
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SSCOP_MDATA_request, /* <- MU */
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SSCOP_MDATA_indication, /* -> MU */
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SSCOP_MERROR_indication, /* -> CODE, CNT */
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};
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.Ed
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.Pp
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The
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.Dv SSCOP_MDATA
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signals are followed by the actual management data, where the
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.Dv SSCOP_MERROR
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signal has the form:
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.Bd -literal
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struct sscop_merr {
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uint32_t sig;
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uint32_t err; /* error code */
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uint32_t cnt; /* error count */
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};
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.Ed
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.El
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.Sh CONTROL MESSAGES
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The
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.Nm sscop
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node understands the generic control messages, plus the following:
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.Bl -tag -width indent
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.It Dv NGM_SSCOP_SETPARAM
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Sets operational parameters of the SSCOP instance and takes the
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following structure:
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.Bd -literal
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struct ng_sscop_setparam {
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uint32_t mask;
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struct sscop_param param;
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};
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.Ed
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.Pp
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The sub-structure
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.Va param
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contains the parameters to set, and the
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.Va mask
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field contains a bit mask, telling which of the parameters to set, and which
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to ignore.
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If a bit is set, the corresponding parameter is set.
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The parameters are:
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.Bd -literal
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struct sscop_param {
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uint32_t timer_cc; /* timer_cc in msec */
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uint32_t timer_poll; /* timer_poll im msec */
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uint32_t timer_keep_alive;/* timer_keep_alive in msec */
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uint32_t timer_no_response;/*timer_no_response in msec */
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uint32_t timer_idle; /* timer_idle in msec */
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uint32_t maxk; /* maximum user data in bytes */
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uint32_t maxj; /* maximum u-u info in bytes */
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uint32_t maxcc; /* max. retransmissions for control packets */
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uint32_t maxpd; /* max. vt(pd) before sending poll */
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uint32_t maxstat; /* max. number of elements in stat list */
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uint32_t mr; /* initial window */
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uint32_t flags; /* flags */
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};
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.Ed
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.Pp
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The
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.Va flags
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field contains the following flags influencing SSCOP operation:
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.Pp
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.Bl -tag -width ".Dv SSCOP_POLLREX" -offset indent -compact
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.It Dv SSCOP_ROBUST
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enable atmf/97-0216 robustness enhancement
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.It Dv SSCOP_POLLREX
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send POLL after each retransmission
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.El
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.Pp
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The bitmap has the following bits:
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.Pp
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.Bl -tag -width ".Dv SSCOP_SET_POLLREX" -offset indent -compact
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.It Dv SSCOP_SET_TCC
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set
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.Va timer_cc
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.It Dv SSCOP_SET_TPOLL
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set
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.Va timer_poll
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.It Dv SSCOP_SET_TKA
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set
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.Va timer_keep_alive
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.It Dv SSCOP_SET_TNR
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set
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.Va timer_no_response
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.It Dv SSCOP_SET_TIDLE
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set
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.Va timer_idle
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.It Dv SSCOP_SET_MAXK
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set
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.Va maxk
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.It Dv SSCOP_SET_MAXJ
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set
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.Va maxj
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.It Dv SSCOP_SET_MAXCC
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set
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.Va maxcc
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.It Dv SSCOP_SET_MAXPD
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set
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.Va maxpd
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.It Dv SSCOP_SET_MAXSTAT
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set
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.Va maxstat
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.It Dv SSCOP_SET_MR
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set the initial window
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.It Dv SSCOP_SET_ROBUST
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set or clear
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.Dv SSCOP_ROBUST
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.It Dv SSCOP_SET_POLLREX
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set or clear
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.Dv SSCOP_POLLREX
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.El
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.Pp
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The node responds to the
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.Dv NGM_SSCOP_SETPARAM
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message with the following response:
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.Bd -literal
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struct ng_sscop_setparam_resp {
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uint32_t mask;
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int32_t error;
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};
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.Ed
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.Pp
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Here
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.Va mask
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contains a bitmask of the parameters that the user requested to set,
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but that could not be set and
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.Va error
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is an
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.Xr errno 2
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code describing why the parameter could not be set.
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.It Dv NGM_SSCOP_GETPARAM
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This message returns the current operational parameters of the SSCOP
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instance in a
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.Vt sscop_param
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structure.
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.It Dv NGM_SSCOP_ENABLE
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This message creates the actual SSCOP instance and initializes it.
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Until this is done, parameters may neither be retrieved nor set, and all
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messages received on any hook are discarded.
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.It Dv NGM_SSCOP_DISABLE
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Destroy the SSCOP instance.
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After this, all messages on any hooks are
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discarded.
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.It Dv NGM_SSCOP_SETDEBUG
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Set debugging flags.
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The argument is a
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.Vt uint32_t .
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.It Dv NGM_SSCOP_GETDEBUG
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Retrieve the actual debugging flags.
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Needs no arguments and responds with a
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.Vt uint32_t .
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.It Dv NGM_SSCOP_GETSTATE
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Responds with the current state of the SSCOP instance in a
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.Vt uint32_t .
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If the node is not enabled, the retrieved state is 0.
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.El
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.Sh FLOW CONTROL
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Flow control works on the upper and on the lower layer interface.
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At the lower
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layer interface, the two messages,
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.Dv NGM_HIGH_WATER_PASSED
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and
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.Dv NGM_LOW_WATER_PASSED ,
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are used to declare or clear the
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.Dq "lower layer busy"
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state of the protocol.
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.Pp
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At the upper layer interface, the
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.Nm sscop
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node handles three types of flow control messages:
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.Bl -tag -width indent
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.It Dv NGM_HIGH_WATER_PASSED
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If this message is received, the SSCOP stops moving the receive window.
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Each time a data message is handed over to the upper layer, the receive
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window is moved by one message.
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Stopping these updates
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means that the window will start to close and if the peer has sent
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all messages allowed by the current window, it stops transmission.
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This means that the upper layer must be able to still receive a full window
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amount of messages.
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.It Dv NGM_LOW_WATER_PASSED
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This will re-enable the automatic window updates, and if the space indicated
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in the message is larger than the current window, the window will be opened
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by that amount.
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The space is computed as the difference of the
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.Va max_queuelen_packets
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and
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.Va current
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members of the
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.Vt ngm_queue_state
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structure.
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.It Dv NGM_SYNC_QUEUE_STATE
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If the upper layer buffer filling state, as indicated by
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.Va current ,
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is equal to or greater than
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.Va high_watermark
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then the message is ignored.
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If this is not the case, the amount
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of receiver space is computed as the difference of
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.Va max_queuelen_packets
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and
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.Va current
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if automatic window updates are currently allowed, and as the difference of
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.Va high_water_mark
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and
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.Va current
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if window updates are disabled.
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If the resulting value is larger than the current window, the current window
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is opened up to this value.
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Automatic window updates are enabled if they
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were disabled.
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.El
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.Sh SEE ALSO
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.Xr netgraph 4 ,
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.Xr ng_atm 4 ,
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.Xr ng_sscfu 4 ,
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.Xr ngctl 8
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.Sh AUTHORS
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.An Harti Brandt Aq harti@FreeBSD.org
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