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llttab - LLT configuration file
/etc/llttab
The
/etc/llttab
file contains information used by
lltconfig
to configure the LLT protocol stack.
The system administrator is responsible for maintaining this
file correctly and consistently across all systems in the
cluster.
A pound sign (#) in the first column of a line means that the
line is a comment. Blank lines are ignored.
A minimal configuration must set the systemid and specify
a network link.
The
/etc/llttab
file supports the following commands:
-
set-node systemid
-
Set the systemid. This is a required command.
systemid
may be an integer in the valid range of systemids, or it may be a symbolic
name (it is translated via
/etc/llthosts
to a systemid).
systemid
also may be a filename beginning with a slash (/); the first
word from the file is used as a symbolic name and translated via
/etc/llthosts
to a systemid. Systemids must be unique within a cluster. If LLT detects
a configuration in which another system is using the same systemid, it
disables the protocol until the system is rebooted.
-
set-cluster clusterid
-
Set the clusterid to a number between 0 and 65535.
This command is needed only if more than one cluster is
sharing network hardware being used by LLT. In this case, each cluster
needs its own clusterid (or, alternately, a unique SAP), so that the clusters
do not interfere with each other. Machines with different clusterids
cannot communicate with each other. The default clusterid is 0.
-
link tag device_name systemid_range link_type sap mtu_size
-
Configure a network interface link below LLT and give it a
tag
for use in subsequent commands and for reference by
lltstat.
This link is bound to the LLT SAP and is used to send heartbeats
and data to other nodes. The
device_name
is the name under
/dev
of the network device; it may be followed by
a colon (:) and an integer specifying which unit or PPA to attach to.
systemid_range
represents the range of systems for which the command is valid. If the
link
command is valid for all systems, specify a dash (-). The defaults for
sap
or
mtu_size
are specified by a dash (-). The
link_type
should be
ether
At least one
link
command is required for LLT to operate.
sap
specifies the SAP to bind on the network links.
mtu_size
specifies the maximum transmission unit to use for sending packets on network links. Note that the links that LLT uses must be isolated or else LLT
will report missing heartbeat messages on the console.
-
link-lowpri tag device_name systemid_range link_type sap
-
mtu_size
Configure a network interface link below LLT and give it a
tag
for use in subsequent commands and for reference by
lltstat.
This link is bound to the LLT SAP and is used to send heartbeats
and data to other systems. The
device_name
is the name under
/dev
of the network device; it may be followed by
a colon (:) and an integer specifying which unit or PPA to attach to.
systemid_range
represents the range of systems for which the command is valid. If the
link
command is valid for all systems, specify a dash (-). The defaults for
sap
or
mtu_size
are specified by a dash (-). The
link_type
should be
ether
At least one
link
command is required for LLT to operate.
sap
specifies the SAP to bind on the network links.
mtu_size
specifies the maximum transmission unit to use for sending packets on
network links.
A link differs from a link-lowpri in that it will send heartbeats
always but will only send data as a last resort when all of the non-lowpri
links are down. If more than one cluster is sharing the same network
using a lowpri link
(usually the public network) then it is extremely important for each cluster
to have a unique clusterid. Also, if there is more than one lowpri
link configured on a system and sharing the same network, then
each must use a unique SAP or else LLT will generate messages
referring to lost heartbeats on the console, since links are normally
required to be completely isolated.
-
set-addr systemid tag address
-
Manually set the
address
for a
system
on a particular link identified by
tag.
The
address
is a MAC address. Use this command when LLT is using links that do not
support broadcast, and thus do not support its automatic address discovery.
Such a configuration needs a list of
addresses
for each system on each link to be set; set them with this command. This command must
follow the
link
command, which defines its
tag.
-
set-verbose 0 | 1
-
Set the verbose mode of
lltconfig,
which causes informational messages to be displayed while it processes
commands. The default is 0.
-
set-warn warning_level
-
Set warning mode, which causes warning messages to be sent
to the
/var/adm/messages
file. The default is 0.
-
include systemid_range
-
Set a
systemid_range
of systemids valid for participation in the cluster.
This command alters the limits of systemids that applications may
use to prevent attempts to communicate with non-existent
systems. The
systemid_range
is specified as two integers separated by a dash (-).
The default is to include 0-nn, where -nn is the maximum supported systemid as determined by the kernel configuration.
-
exclude systemid_range
-
Set a
systemid_range
of systemids not valid for participation in the cluster.
This command alters the limits of systemids that applications may
use to prevent attempts to communicate with non-existent
systmes. The
systemid_range
is specified as two integers separated by a dash (-).
The default is to include 0-nn, where -nn is the maximum supported systemid as determined by the kernel configuration.
-
set-arp 0 | 1
-
Set the LLT-ARP mode. If it is set, LLT automatically discovers
the MAC addresses of other nodes in the cluster so that they do
not have to be set manually with the
set-addr
command. This option only has meaning when set-bcsathb is 0.
The default is 0.
-
set-bcasthb 0 | 1
-
Set the broadcast heartbeat mode. If it is set, LLT uses the broadcast
capabilities of the underlying network links to send heartbeats and LLT-ARP
discovery packets to other
systems, instead of sending them to each system individually.
This option is valid only when all underlying network links support broadcast.
The default is 1.
-
set-timer timer:value
-
Set the values of the protocol timers. Valid values for
timer
are
heartbeat,
peertrouble,
peerinact,
oos,
retrans,
service,
and
arp.
These timers are the heartbeat, peer inactivity, out-of-sequence,
retransmit, service procedure, and arp expiration timers, respectively. The
value
is specified in 1/100ths
of a second. The timer values should not be changed haphazardly, or the
protocol may fail to operate.
-
set-flow parameter:value
-
Set the values of the flow control limits. Valid values for
parameter
are
lowwater,
highwater,
xportlowwater,
xporthighwater,
rportlowwater,
rporthighwater,
window,
ackval,
sws
and
linkburst.
These limits are
the node low water mark, node high water mark, port transmit low water mark
port transmit high water mark, port receive low water mark, port receive
high water mark, window size, packets to wait (during receive) before
sending explict ACK, packets to queue (during transmit) to avoid
silly window syndrome and packets to be sent per link consecutively before
moving onto the next available link respectively. The
value
is specified in number of packets. The flow control limits should
not be changed haphazardly, or the protocol may fail to operate.
-
set-nofastpath 0 | 1
-
Used to disable fastpath mode. If set to 1 LLT does not use the "fastpath"
interface to NICs even if it exists. This must precede any link or
link-lowpri commands. The default is 0 i.e. LLT attempts to use
"fastpath" interface if it exists.
-
set-checksum 0 | 1 | 10 | 2 | 20
-
Set checksum mode. When set to 1, LLT checksums each packet it sends to
peer to guard against packet corruption on-the-wire. LLT will also offload
checksum calculation to hardware if the underlying NIC supports it.
In case checksum verification fails on the receiver LLT will drop
that packet causing the sender to retransmit it.
Setting to 10 is same as setting to 1 except that LLT will strictly
do checksums in software and will NOT offload checksumming to NIC
even if it is capable of doing so.
When set to 2, LLT also checksums the whole data buffer submitted by
the client to be verified by the peer before delivering it to peer-client.
In case the checksum verification fails on the receiver, LLT will
panic the machine. This is purposefully done to help in analysis
of memory corruption from a crash dump.
Setting to 20 is same as setting to 2 except that LLT will strictly
do checksums in software and will NOT offload checksumming to NIC
even if it is capable of doing so.
Level 2 and level 20 checksums should only be used when diagnosing memory
corruption under the advisement of the support center, since it does have
the ability to panic the machine.
The default is 0 (no checksums) as LLT depends on the NIC's hardware to
guarantee packet accuracy. Level 1 checksums may be enabled if the private
network is suspected of packet corruption on-the-wire or in the NIC. There
may be some tradeoff of peformance due to the CPU cycles needed to perform
the checksum in addition to those performed by the NIC hardware.
Currently checksum offloading is only implemented on Linux and only for
transmitting packets.
-
set-tracesize size_in_kb
-
Set trace buffer size. The size is specified in KB.
-
set-tracelevel 0 | 1 | 3
-
Set trace level.
If set to 1 (the default), LLT will trace all events (upcalls, flow-control,
link and connection state changes) in an internal circular buffer (called as
trace buffer).
When set to 3, LLT will also trace packets that are received or transmitted.
This has an overhead and may impact performance. Hence should be used only
to debug.
Setting to 0 disables tracing.
-
set-strictsrc 0 | 1
-
Enable strict source address checking.
If set to 1, LLT will check the source address of incoming packets and
drop packets from unknown sources. When set to 0 this check is not
performed.
This option is only applicable when UDP links are configured. For ethernet
this will be ignored (even if set to 1). If left unspecified this option
will be set to 1 automatically if UDP links are configured.
The following example shows a typical
/etc/llttab
file with two links:
# look up my node ID in /etc/llthosts
set-node system1
link qfe1 /dev/qfe:1 - ether - -
link qfe3 /dev/qfe:3 - ether - -
The following example shows an
/etc/llttab
file with two links, one of which is used only as a last resort:
# take the name in /etc/nodename and look
# up my system ID in /etc/llthosts
set-node /etc/nodename
# heartbeats only on this link unless the other one fails
link-lowpri le0 /dev/le:0 - ether 0xCAFE -
link qfe0 /dev/qfe:0 - ether 0xCAFE -
In the example above, the last dash (-) directs LLT to assign a default value
to
mtu_size.
The following example shows an
/etc/llttab
file for a cluster of two systems connected by two
links that do not support broadcasting:
# set my system ID numerically
set-node 2
link scid0 /dev/scid:0 - ether - -
link scid1 /dev/scid:1 - ether - -
# MAC addresses on link 0
set-addr 1 scid0 00:00:00:01
set-addr 2 scid0 00:00:00:02
# MAC addresses on link 1
set-addr 1 scid1 00:00:01:01
set-addr 2 scid1 00:00:01:02
set-arp 0
set-bcasthb 0
Manual editing of the GAB and LLT configuration files is not recommended.
Refer to the documentation for your clustering solution for information
and guidelines on configuring LLT and GAB.
-
/etc/llttab
-
LLT configuration file
-
/etc/llthosts
-
LLT host name database
-
/opt/VRTSllt/sample-llttab
-
Sample LLT configuration file
lltconfig(1M)
Last updated: March 2006
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