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sys_attrs_inet(5)
NAME
sys_attrs_inet - inet subsystem attributes
DESCRIPTION
This reference page lists and describes attributes for the Internet (inet)
kernel subsystem. Refer to the sys_attrs(5) reference page for an
introduction to the topic of kernel subsystem attributes.
icmp_rejectcodemask
A bit mask that designates the ICMP codes that the system should
reject. For example, to reject ICMP redirects, you would set the mask
bit position for the ICMP_REDIRECT code (5), which is 2^5 (32) in
integer, or 0x20 in hexadecimal. Multiple masks can be combined to
reject more than one code. Code definitions can be found in the
/usr/sys/include/netinet/ip_icmp.h file.
Default value: 0 (bits)
Minimum value: 0
Maximum value: 131072, or 0x2000 in hexadecimal
inifaddr_hsize
The number of hash buckets in the kernel interface alias table
(in_ifaddr). The value of the inifaddr_hsize attribute is always
rounded down to the nearest power of 2. The maximum value is 512.
Default value: 32 (hash buckets)
Minimum value: 16
Maximum value: 512
ipdefttl
The default Internet Protocol (IP) time-to-live value.
Default value: DEFTTL, or 64 (router hops)
Minimum value: 0
Maximum value: 255
ipdirected_broadcast
A value that enables (1) or disables (0) a check to determine whether
an IP datagram whose destination address is a directed broadcast
address has been received on the interface corresponding to that
broadcast address.
Default value: 0 (disabled)
ipforwarding
A value that enables (1) or disables (0) a system's ability to forward
IP packets that are not addressed to the system. You can also enable
this functionality by using the /usr/sbin/iprsetup command.
Default value: 0 (disabled)
For systems functioning as routers, both ipforwarding and ipgateway
attributes must be 1.
ipfragttl
Maximum time an IP fragment can spend waiting to be reassembled.
Default value: IPFRAGTTL (60, in units of .5 seconds, or 30 seconds)
Minimum value: 1
Maximum value: INT_MAX, or 2 billion
ipgateway
A value that enables (1) or disables (0) a system's ability to forward
IP packets that are not addressed to the system. This functionality is
usually enabled by using the /usr/sbin/iprsetup command.
Default value: 0 (disabled)
For systems functioning as routers, both ipforwarding and ipgateway
attributes must be 1.
ipport_userreserved
The number of times a system can simultaneously make outgoing
connections to other systems. The number of outgoing ports is the
value of the ipport_userreserved attribute minus the value of the
ipport_userreserved_min attribute. The default value of the attribute
is 5000; therefore, the default number of outgoing ports is 3976.
Default value: 5000
Minimum value: 1
Maximum value: 65535
ipport_userreserved_min
The lower limit of range of port numbers available for use by a TCP or
UDP application. The number of outgoing ports is the value of the
ipport_userreserved attribute minus the value of the
ipport_userreserved_min attribute. The default value of the attribute
is 5000; therefore, the default number of outgoing ports is 3976.
Default value: 1024
Minimum value: 1
Maximum value: 65535
ipqmaxlen
Maximum length of the IP input queue (ipintrq) before input packets are
dropped.
Default value: 1024 (bytes)
Minimum value: 1024
Maximum value: 65535
ipqs
Maximum number of IP input queues.
Default value: 1 (queues)
Minimum value: 1
Maximum value: 64
ipsendredirects
A value that enables (1) or disables (0) the sending of ICMP redirect
messages.
Default value: 1 (enabled)
ipsrcroute
Enables (1) or disables (0) source routing.
Default value: 1 (enabled)
pmtu_decrease_intvl
Time to wait after a decrease in a PMTU value before attempting to
determine if the PMTU value has increased.
Default value: PMTU_DECREASE_INTVL, or 1200 (in units of .5 seconds)
Minimum value: 1
Maximum value: UINT_MAX, or 4 billion
pmtu_enabled
A value that enables (1) or disables (0) discovery of the path maximum
transfer unit (PMTU).
Default value: 1 (enabled)
pmtu_increase_intvl
Time to wait after an increase in a PMTU value before attempting to
determine if the PMTU has increased.
Default value: PMTU_INCREASE_INTVL, or 240 (in units of .5 seconds)
Minimum value: 1
Maximum value: UINT_MAX, or 4 billion
pmtu_rt_check_intvl
The timer processing interval for routes participating in the PMTU
discovery process.
Default value: PMTU_RT_CHECK_INTVL, or 20 (in units of .5 seconds)
Minimum value: 1
Maximum value: UINT_MAX, or 4 billion
subnetsarelocal
A value that enables (1) or disables (0), consideration of all IP
addresses in the same network as being local. When this value is 1,
all IP addresses that are in different subnets but in the same network
are considered local. When this value is 0, only the IP addresses that
match a directly connected subnet are considered local.
Default value: 1 (enabled)
tcbhashnum
The number of Transmission Control Protocol (TCP) hash tables.
Default value: 1 (table)
Minimum value: 1
Maximum value: 64
tcbhashsize
The number of buckets in the TCP inpcb hash table.
Default value: 512 (buckets)
Minimum value: 0
Maximum value: INT_MAX, or 2 billion
tcbquicklisten
Enables (1) or disables (0) optimization of the listen path for server
sockets.
Default value: 1 (enabled)
tcp_compat_42
A value that enables (1) or disables (0) 4.2 BSD-compatible behavior
for the initial send sequence of numbers and keepalives.
Default value: 1 (enabled)
tcp_cwnd_segments
The number of initial segments to send during congestion window
negotiation.
Default value: 2 (segments)
Minimum value: 1
Maximum value: INT_MAX, or 2 billion
tcp_dont_winscale
A value that enables (0) or disables (1) window scaling.
Default value: 0 (enabled)
Note
The values for disabling and enabling are the reverse of what they
are for most other attributes.
tcp_keepalive_default
A value that enables (1) or disables (0) TCP keepalive for all sockets.
TCP keepalive supports the periodic transmission of messages on a
connected socket in order to keep connections active. If keepalive is
enabled, sockets that do not exit cleanly are cleaned up when the
keepalive interval expires. If keepalive is not enabled, those
sockets will continue to exist until you reboot the system.
Default value: 0 (disabled)
Applications enable keepalive for sockets by setting the setsockopt()
function's SO_KEEPALIVE option. Use the tcp_keepalive_default
attribute to override programs that do not set keepalive on their own,
particularly if you have no access to the sources for those programs.
tcp_keepcnt
Maximum number of keepalive probes that can be sent before a connection
is dropped.
Default value: TCPTV_KEEPCNT, or 8 (probes)
Minimum value: 1
Maximum value: 32767
tcp_keepidle
Idle time before the first keepalive probe.
Default value: TCPTV_KEEP_IDLE, or 14400 (in units of .5 seconds)
Minimum value: 2
Maximum value: 32767
tcp_keepinit
Initial connect timeout.
Default value: TCPTV_KEEP_INIT, or 150 (in units of .5 seconds)
Minimum value: 2
Maximum value: 32767
tcp_keepintvl
Time between keepalive probes.
Default value: TCPTV_KEEP_INTVL, or 150 (in units of .5 seconds)
Minimum value: 2
Maximum value: 32767
tcp_msl
The maximum lifetime of a TCP segment.
Default value: 60 (in units of .5 seconds)
Minimum value: 1
Maximum value: 2 billion
tcp_mssdflt
Default maximum segment size.
Default value: TCP_MSS, or 536 (bytes)
Minimum value: 1
Maximum value: 2 billion
tcp_recvspace
Default receive buffer size for TCP sockets.
Default value: TCP_RECVSPACE, or 61440 (bytes)
Minimum value: 1
Maximum value: 4 billion (cannot be larger than sb_max)
tcp_rexmit_interval_min
Minimum amount of time between TCP retransmissions.
Default value: 2 (in units of .5 seconds), or 1 second
Minimum value: 1
Maximum value: 2 billion
tcp_rexmtmax
The maximum amount of time between TCP retransmissions.
Default value: 128 (in units of .5 seconds), or 64 seconds
Minimum value: 1
Maximum value: INT_MAX, or 2 billion
tcp_rttdflt
Initial assumed round-trip time, in seconds.
Default value: 3 (seconds)
Minimum value: 0
Maximum value: INT_MAX, or 2 billion
tcp_sendspace
Default send buffer size, in bytes, for TCP sockets.
Default value: TCP_SENDSPACE, or 61440 (bytes)
Minimum value: 1
Maximum value: UINT_MAX, or 4 billion (cannot be larger than sb_max)
tcp_ttl
IP time-to-live, in router hops, for TCP packets.
Default value: TCP_TTL, or 60 (router hops)
Minimum value: 0
Maximum value: 255
tcp_urgent_42
A value that enables (1) or disables (0) 4.2 BSD-compatible behavior
for an urgent pointer. The urgent pointer is a pointer to the first
octet of data past the urgent section. When disabled, the urgent
pointer is a pointer to the last octet of data in the urgent section.
Default value: 1 (enabled)
tcpnodelack
A value that enables (0) or disables (1) delayed acknowledgments.
Default value: 0 (enabled)
Note
The values for disabling and enabling are the reverse of what they
are for most other attributes.
tcprexmtthresh
Number of duplicate acknowledgments (ACKs) before retransmission.
Default value: TCPREXMTTHRESH, or 3 (duplicate acknowledgements)
Minimum value: 1
Maximum value: INT_MAX, or 2 billion
tcptwreorder
A value that enables (1) or disables (0) the movement of TCP inpcbs in
the TIME_WAIT state to the end of the inpcb list.
Default value: 0 (disabled)
udp_recvspace
Default receive buffer size, in bytes, for UDP sockets.
Default value: UDP_RECVSPACE, or 42240 (bytes)
Minimum value: 1
Maximum value: UINT_MAX, or 4 billion (cannot be larger than sb_max)
udp_sendspace
Default send buffer size, in bytes, for UDP sockets.
Default value: UDP_SENDSPACE, or 9216 (bytes)
Minimum value: 1
Maximum value: UINT_MAX, or 4 billion (cannot be larger than sb_max)
udp_ttl
IP time-to-live, in router hops, for UDP packets.
Default value: UDP_TTL, or 30 (router hops)
Minimum value: 0
Maximum value: 255
udpcksum
A value that enables (1) or disables (0) checksumming in the Internet
user datagram protocol (UDP).
Default value: 1 (enabled)
SEE ALSO
sys_attrs(5)
Tuning Tru64 UNIX for Internet Servers at the following location:
http://www.digital.com/internet/document/ias/tuning.html.
System Configuration and Tuning
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