llc2(4) File Formats llc2(4)NAMEllc2 - LLC2 Configuration file
SYNOPSIS
/etc/llc2/default/llc2.*
DESCRIPTION
The llc2 files contain information needed by LLC2 to establish the
appropriate links to the underlying MAC layer drivers as well as the
parameters necessary to configure the LLC (Logical Link Control) Class
II Station Component structures for that link.
The comments are made up of one or more lines starting with the "#"
character in column 1.
The main section consists of keyword/value pairs of the form key‐
word=value, used to initialize the particular adapter.
A sample of the llc2 is presented below:
devicename=/dev/dnet
deviceinstance=1
llc2_on=1 # LLC2: On/Off on this device
deviceloopback=1
timeinterval=0 # LLC2: Timer Multiplier
acktimer=2 # LLC2: Ack Timer
rsptimer=2 # LLC2: Response Timer
polltimer=4 # LLC2: Poll Timer
rejecttimer=6 # LLC2: Reject Timer
rembusytimer=8 # LLC2: Remote Busy Timer
inacttimer=30 # LLC2: Inactivity Timer
maxretry=6 # LLC2: Maximum Retry Value
xmitwindowsz=14 # LLC2: Transmit Window Size
rcvwindowsz=14 # LLC2: Receive Window Size
MAC specific Parameters
The llc2.ppa file contains 4 parameters directly related to the under‐
lying MAC-level driver. These are the name of the physical device, the
instance of the device, whether LLC2 can be used with this device, and
whether the device is capable of looping back data addressed to the
node's unique MAC address, broadcast address, or multicast addresses.
Setting the llc2_on parameter to 1 means that LLC2 can be used with
this device; setting it to 0 means otherwise. Setting the loopback
parameter to 1 means that the LLC2 module will loop back data addressed
to this node's unique MAC address or to a broadcast/multicast address.
The most likely use is for a media that cannot receive its own trans‐
missions (for example, ethernet) or when the MAC-level driver inten‐
tionally does not loop back data addressed to the local node under the
assumption that the upper layers have already done so.
Host-Based LLC2 Parameters
The LLC2 contains ten parameters in the configuration file
(/etc/llc2/default/llc2.ppa) that apply to configurations using the
Host-Based LLC2 component for connection-oriented operation over an
Ethernet, Token Ring, or FDDI media.
The ten parameters break down into the following four groups:
· Six parameters deal with timer settings for managing the flow of
LLC elements of procedure (PDUs) on a data link connection.
· One parameter is the multiplier that is used to determine the
period of the interval timer for the station. A value of 1 means
that each tick count represents 100 milliseconds; 5 means each
tick count is 500 milliseconds. Should the parameter be omitted,
the default value is 5, except for Token Ring links which use a
default of 1.
· One parameter indicates how many times an operation should be
retried on a data link connection.
· Two parameters are for controlling the number of unacknowledged I
PDUs to send or receive on a data link connection.
Additional information on these parameters can be found in ISO
8802-2:1989, Section 7.8.
The following table of Logical Link Control Parameters provides the LLC
configuration parameter names, default values, and ranges.
Parameter Description Default Range
timeinterval The timer ticks in 100 ms 5, except TPR - 1 0 - 10
intervals. This parameter
is used to scale the fol‐
lowing 5 timer parameters.
acktimer The connection acknowledg‐ 2 > 0
ment timer length in (100
* timeinterval) ms.
rsptimer The response acknowledg‐ 2 > 0
ment timer length in (100
* timeinterval) ms.
polltimer The connection poll timer 4 > 0
length in (100 * timein‐
terval) ms.
rejecttimer The connection reject 6 > 0
timer length in (100 *
timeinterval) ms.
rembusytimer The connection remote busy 8 > 0
timer length in (100 *
timeinterval) ms.
inacttimer The connection inactivity 30 > 0
timer length in (100 *
timeinterval) ms.
maxretry The maximum number of 6 0 - 100
retries of an action on a
connection.
xmitwindowsz The maximum number of 14 0 - 127
unacknowledged I-format
protocol data units that
can be transmitted on a
connection before awaiting
an acknowledgment.
rcvwindowsz The maximum number of 14 0 - 127
unacknowledged I-format
protocol data units that
can be received on a con‐
nection before an acknowl‐
edgment is sent.
Default values are set when the following conditions are true:
· The parameter is not set by the user.
· The user requests a default /etc/llc2/default/llc2.instance file,
where instance is the sequence number, starting with 0, of the
adapter as detected by ifconfig(1M). For example, if there are 3
adapters on the machine, the default configuration files will be
named in order as /etc/llc2/default/llc2.0,
/etc/llc2/default/llc2.1, and /etc/llc2/default/llc2.2.
· The user codes a value of 0 for a parameter.
Timer Parameter Descriptions
acktimer The acktimer parameter is used to manage the following
sample sequences:
1. Attempting to establish, reset, or disconnect a
connection.
SABME start acknowledgment timer
or -------------------------------->
DISC
The acknowledgment timer expires before the
receipt of a response.
SABME start acknowledgment timer
or -------------------------------->
DISC
stop acknowledgment timer
<-------------------------------- UA
2. Sending an FRMR in response to a received PDU
of dubious distinction:
PDU with invalid N(R)
or
I PDU with invalid N(S)
or
<------------------- PDU of invalid length
or
unexpected UA PDU
or
response PDU with
invalid P/F setting
start acknowledgment timer
FRMR -------------------------------->
Acknowledgment timer expires before the receipt
of a PDU.
start acknowledgment timer
FRMR -------------------------------->
stop acknowledgment timer
SABME, FRMR
<------------------------------- DISC, or DM
3. There is also a special case of the acknowledg‐
ment timer, referred to in this implementation
as the response acknowledgment timer (rspti‐
mer). It is used when sending an I PDU.
start response acknowledgement timer
I -------------------------------------->
Response acknowledgment timer expires before
the receipt of an acknowledgment.
start poll timer
RR -------------------------------->
polltimer The polltimer parameter is used to manage situations
where a Supervisory command PDU (RR, RNR, or REJ) is
sent with the P/F bit set. This type of PDU is typi‐
cally sent when:
· There has been a period of inactivity on a connec‐
tion in information transfer mode.
· The remote node must be notified of a local busy
condition occurring in information transfer mode.
The expiration of the poll timer causes another Super‐
visory command PDU (which may be of a different type
than the first) to be sent with the P/F bit set, pro‐
vided the retry count has not exceeded the maximum
retry value. This timer, then, provides an extended
retry mechanism for a connection in information trans‐
fer mode.
rejecttimer The rejecttimer parameter controls the frequency with
which a REJ PDU is sent to a remote node from which an
I PDU with an unexpected N(S) was received and which
has not corrected the situation by sending an I PDU
with the expected N(S).
<----------------------- I PDU with
unexpected N(S)
start reject timer
REJ ------------------------>
Reject timer expires before the receipt of an I PDU
with an expected N(S).
start reject and poll timer
REJ ----------------------------->
stop reject and poll timer
<--------------------------- I PDU with
expected N(S)
rembusytimer The rembusytimer parameter is used to determine how
long the local node should wait, after the remote node
sends an RNR to indicate it is busy, before sending a
Supervisory PDU with the P/F bit set to solicit the
current state of the remote node. If the remote node
indicates that it has cleared its busy condition before
the timer expires, the local node stops the remote busy
timer.
inacttimer The inacttimer parameter controls how much time is
allowed to elapse on a connection in information trans‐
fer mode between the issuing of command PDUs by the
local node. If the inactivity timer expires because a
command PDU has not been generated in the configured
time interval, a Supervisory PDU with the P/F bit set
is sent to the remote node to solicit its current
state, provided that the connection is in information
transfer mode. Each time a command PDU is sent by the
local node, the inactivity timer is restarted.
The following rules of thumb should apply for the timer parameters:
· The acktimer, rsptimer, and polltimer parameters should have
small relative values to allow for quick recovery from common
transient error conditions on a connection.
· The rejecttimer and rembusytimer parameters should have intermedi‐
ate relative values to allow the local and remote nodes time to
recover without resorting to possibly unnecessary polling cycles.
· The inacttimer parameter should be set to a large relative value
to provide a safety net in information transfer mode.
You may need to shift the values for the timer parameters to higher
values if bridges are included in the network or a user application
requires a substantial amount of time to respond to connection estab‐
lishment requests or handle information flow.
Maximum Retry Parameter Description
The maxretry parameter determines the number of times a recovery oper‐
ation is performed before notifying the user that an error has occurred
on a connection. Typical examples of its use include the following:
· When the remote node fails to respond to a SABME sent by the local
node to establish or reset the connection, the SABME is resent
each time the acknowledgment timer expires, up to maxretry number
of times.
· In information transfer mode, if the response acknowledgment timer
expires after an I PDU has been sent, an RR with the P/F bit set
is sent (and resent each time the poll timer expires) until the
remote node responds or maxretry number of RRs have been sent.
In general, the maxretry value should not need to be large. Since the
acknowledgment and poll timers are typically used in recovery opera‐
tions that involve the maxretry parameter, the product of maxretry and
either acktimer, rsptimer, or polltimer gives a rough estimate of the
length of time allotted for the connection to attempt internal error
recovery before notifying the user.
Window Size Parameter Descriptions
rcvwindowsz The rcvwindowsz parameter is used to set the receive
window size for I PDUs received locally on a connec‐
tion. This value should agree with the transmit window
size set for the connection at the remote node. If the
local rcvwindowsz is greater than the remote transmit
window size, I PDUs sent by the remote node are not
acknowledged quickly. If the local rcvwindowsz is less
than the remote transmit window size, there is a
greater risk of the local node generating FRMR PDUs,
requiring intervention by the user application when
transient errors on the connection require the remote
node to retransmit an I PDU. REJ PDUs are recovered
internally.
xmitwindowsz The xmitwindowsz parameter sets the local transmit win‐
dow size for a connection. It denotes the number of
unacknowledged I PDUs that the local node may have out‐
standing. The configured value should match the receive
window size for the connection at the remote node,
based on the same reasoning as for the rcvwindowsz
parameter.
In many cases, the values assigned to rcvwindowsz and xmitwindowsz for
adapters on a server node will depend on the transmit and receive win‐
dow sizes specified for another LLC implementation on a client node. In
cases where this LLC implementation is resident in both nodes, larger
values for these parameters are useful in environments where much of
the activity on a connection consists of file transfer operations.
Smaller values are warranted if analysis of LLC2 connection component
statistics reveals that connections are entering local or remote busy
state frequently.
FILES
/etc/llc2/default/llc2.*
SEE ALSOllc2_autoconfig(1), llc2_config(1), ifconfig(1M), llc2(7D)SunOS 5.10 7 Feb 2000 llc2(4)
