Documentation / networking / ip-sysctl.txt

Custom Search

Based on kernel version 3.2. Page generated on 2012-01-05 23:29 EST.

	/proc/sys/net/ipv4/* Variables:
	
	ip_forward - BOOLEAN
		0 - disabled (default)
		not 0 - enabled
	
		Forward Packets between interfaces.
	
		This variable is special, its change resets all configuration
		parameters to their default state (RFC1122 for hosts, RFC1812
		for routers)
	
	ip_default_ttl - INTEGER
		Default value of TTL field (Time To Live) for outgoing (but not
		forwarded) IP packets. Should be between 1 and 255 inclusive.
		Default: 64 (as recommended by RFC1700)
	
	ip_no_pmtu_disc - BOOLEAN
		Disable Path MTU Discovery.
		default FALSE
	
	min_pmtu - INTEGER
		default 552 - minimum discovered Path MTU
	
	route/max_size - INTEGER
		Maximum number of routes allowed in the kernel.  Increase
		this when using large numbers of interfaces and/or routes.
	
	neigh/default/gc_thresh3 - INTEGER
		Maximum number of neighbor entries allowed.  Increase this
		when using large numbers of interfaces and when communicating
		with large numbers of directly-connected peers.
	
	mtu_expires - INTEGER
		Time, in seconds, that cached PMTU information is kept.
	
	min_adv_mss - INTEGER
		The advertised MSS depends on the first hop route MTU, but will
		never be lower than this setting.
	
	rt_cache_rebuild_count - INTEGER
		The per net-namespace route cache emergency rebuild threshold.
		Any net-namespace having its route cache rebuilt due to
		a hash bucket chain being too long more than this many times
		will have its route caching disabled
	
	IP Fragmentation:
	
	ipfrag_high_thresh - INTEGER
		Maximum memory used to reassemble IP fragments. When
		ipfrag_high_thresh bytes of memory is allocated for this purpose,
		the fragment handler will toss packets until ipfrag_low_thresh
		is reached.
	
	ipfrag_low_thresh - INTEGER
		See ipfrag_high_thresh
	
	ipfrag_time - INTEGER
		Time in seconds to keep an IP fragment in memory.
	
	ipfrag_secret_interval - INTEGER
		Regeneration interval (in seconds) of the hash secret (or lifetime
		for the hash secret) for IP fragments.
		Default: 600
	
	ipfrag_max_dist - INTEGER
		ipfrag_max_dist is a non-negative integer value which defines the
		maximum "disorder" which is allowed among fragments which share a
		common IP source address. Note that reordering of packets is
		not unusual, but if a large number of fragments arrive from a source
		IP address while a particular fragment queue remains incomplete, it
		probably indicates that one or more fragments belonging to that queue
		have been lost. When ipfrag_max_dist is positive, an additional check
		is done on fragments before they are added to a reassembly queue - if
		ipfrag_max_dist (or more) fragments have arrived from a particular IP
		address between additions to any IP fragment queue using that source
		address, it's presumed that one or more fragments in the queue are
		lost. The existing fragment queue will be dropped, and a new one
		started. An ipfrag_max_dist value of zero disables this check.
	
		Using a very small value, e.g. 1 or 2, for ipfrag_max_dist can
		result in unnecessarily dropping fragment queues when normal
		reordering of packets occurs, which could lead to poor application
		performance. Using a very large value, e.g. 50000, increases the
		likelihood of incorrectly reassembling IP fragments that originate
		from different IP datagrams, which could result in data corruption.
		Default: 64
	
	INET peer storage:
	
	inet_peer_threshold - INTEGER
		The approximate size of the storage.  Starting from this threshold
		entries will be thrown aggressively.  This threshold also determines
		entries' time-to-live and time intervals between garbage collection
		passes.  More entries, less time-to-live, less GC interval.
	
	inet_peer_minttl - INTEGER
		Minimum time-to-live of entries.  Should be enough to cover fragment
		time-to-live on the reassembling side.  This minimum time-to-live  is
		guaranteed if the pool size is less than inet_peer_threshold.
		Measured in seconds.
	
	inet_peer_maxttl - INTEGER
		Maximum time-to-live of entries.  Unused entries will expire after
		this period of time if there is no memory pressure on the pool (i.e.
		when the number of entries in the pool is very small).
		Measured in seconds.
	
	TCP variables:
	
	somaxconn - INTEGER
		Limit of socket listen() backlog, known in userspace as SOMAXCONN.
		Defaults to 128.  See also tcp_max_syn_backlog for additional tuning
		for TCP sockets.
	
	tcp_abc - INTEGER
		Controls Appropriate Byte Count (ABC) defined in RFC3465.
		ABC is a way of increasing congestion window (cwnd) more slowly
		in response to partial acknowledgments.
		Possible values are:
			0 increase cwnd once per acknowledgment (no ABC)
			1 increase cwnd once per acknowledgment of full sized segment
			2 allow increase cwnd by two if acknowledgment is
			  of two segments to compensate for delayed acknowledgments.
		Default: 0 (off)
	
	tcp_abort_on_overflow - BOOLEAN
		If listening service is too slow to accept new connections,
		reset them. Default state is FALSE. It means that if overflow
		occurred due to a burst, connection will recover. Enable this
		option _only_ if you are really sure that listening daemon
		cannot be tuned to accept connections faster. Enabling this
		option can harm clients of your server.
	
	tcp_adv_win_scale - INTEGER
		Count buffering overhead as bytes/2^tcp_adv_win_scale
		(if tcp_adv_win_scale > 0) or bytes-bytes/2^(-tcp_adv_win_scale),
		if it is <= 0.
		Possible values are [-31, 31], inclusive.
		Default: 2
	
	tcp_allowed_congestion_control - STRING
		Show/set the congestion control choices available to non-privileged
		processes. The list is a subset of those listed in
		tcp_available_congestion_control.
		Default is "reno" and the default setting (tcp_congestion_control).
	
	tcp_app_win - INTEGER
		Reserve max(window/2^tcp_app_win, mss) of window for application
		buffer. Value 0 is special, it means that nothing is reserved.
		Default: 31
	
	tcp_available_congestion_control - STRING
		Shows the available congestion control choices that are registered.
		More congestion control algorithms may be available as modules,
		but not loaded.
	
	tcp_base_mss - INTEGER
		The initial value of search_low to be used by the packetization layer
		Path MTU discovery (MTU probing).  If MTU probing is enabled,
		this is the initial MSS used by the connection.
	
	tcp_congestion_control - STRING
		Set the congestion control algorithm to be used for new
		connections. The algorithm "reno" is always available, but
		additional choices may be available based on kernel configuration.
		Default is set as part of kernel configuration.
	
	tcp_cookie_size - INTEGER
		Default size of TCP Cookie Transactions (TCPCT) option, that may be
		overridden on a per socket basis by the TCPCT socket option.
		Values greater than the maximum (16) are interpreted as the maximum.
		Values greater than zero and less than the minimum (8) are interpreted
		as the minimum.  Odd values are interpreted as the next even value.
		Default: 0 (off).
	
	tcp_dsack - BOOLEAN
		Allows TCP to send "duplicate" SACKs.
	
	tcp_ecn - INTEGER
		Enable Explicit Congestion Notification (ECN) in TCP. ECN is only
		used when both ends of the TCP flow support it. It is useful to
		avoid losses due to congestion (when the bottleneck router supports
		ECN).
		Possible values are:
			0 disable ECN
			1 ECN enabled
			2 Only server-side ECN enabled. If the other end does
			  not support ECN, behavior is like with ECN disabled.
		Default: 2
	
	tcp_fack - BOOLEAN
		Enable FACK congestion avoidance and fast retransmission.
		The value is not used, if tcp_sack is not enabled.
	
	tcp_fin_timeout - INTEGER
		Time to hold socket in state FIN-WAIT-2, if it was closed
		by our side. Peer can be broken and never close its side,
		or even died unexpectedly. Default value is 60sec.
		Usual value used in 2.2 was 180 seconds, you may restore
		it, but remember that if your machine is even underloaded WEB server,
		you risk to overflow memory with kilotons of dead sockets,
		FIN-WAIT-2 sockets are less dangerous than FIN-WAIT-1,
		because they eat maximum 1.5K of memory, but they tend
		to live longer.	Cf. tcp_max_orphans.
	
	tcp_frto - INTEGER
		Enables Forward RTO-Recovery (F-RTO) defined in RFC4138.
		F-RTO is an enhanced recovery algorithm for TCP retransmission
		timeouts.  It is particularly beneficial in wireless environments
		where packet loss is typically due to random radio interference
		rather than intermediate router congestion.  F-RTO is sender-side
		only modification. Therefore it does not require any support from
		the peer.
	
		If set to 1, basic version is enabled.  2 enables SACK enhanced
		F-RTO if flow uses SACK.  The basic version can be used also when
		SACK is in use though scenario(s) with it exists where F-RTO
		interacts badly with the packet counting of the SACK enabled TCP
		flow.
	
	tcp_frto_response - INTEGER
		When F-RTO has detected that a TCP retransmission timeout was
		spurious (i.e, the timeout would have been avoided had TCP set a
		longer retransmission timeout), TCP has several options what to do
		next. Possible values are:
			0 Rate halving based; a smooth and conservative response,
			  results in halved cwnd and ssthresh after one RTT
			1 Very conservative response; not recommended because even
			  though being valid, it interacts poorly with the rest of
			  Linux TCP, halves cwnd and ssthresh immediately
			2 Aggressive response; undoes congestion control measures
			  that are now known to be unnecessary (ignoring the
			  possibility of a lost retransmission that would require
			  TCP to be more cautious), cwnd and ssthresh are restored
			  to the values prior timeout
		Default: 0 (rate halving based)
	
	tcp_keepalive_time - INTEGER
		How often TCP sends out keepalive messages when keepalive is enabled.
		Default: 2hours.
	
	tcp_keepalive_probes - INTEGER
		How many keepalive probes TCP sends out, until it decides that the
		connection is broken. Default value: 9.
	
	tcp_keepalive_intvl - INTEGER
		How frequently the probes are send out. Multiplied by
		tcp_keepalive_probes it is time to kill not responding connection,
		after probes started. Default value: 75sec i.e. connection
		will be aborted after ~11 minutes of retries.
	
	tcp_low_latency - BOOLEAN
		If set, the TCP stack makes decisions that prefer lower
		latency as opposed to higher throughput.  By default, this
		option is not set meaning that higher throughput is preferred.
		An example of an application where this default should be
		changed would be a Beowulf compute cluster.
		Default: 0
	
	tcp_max_orphans - INTEGER
		Maximal number of TCP sockets not attached to any user file handle,
		held by system.	If this number is exceeded orphaned connections are
		reset immediately and warning is printed. This limit exists
		only to prevent simple DoS attacks, you _must_ not rely on this
		or lower the limit artificially, but rather increase it
		(probably, after increasing installed memory),
		if network conditions require more than default value,
		and tune network services to linger and kill such states
		more aggressively. Let me to remind again: each orphan eats
		up to ~64K of unswappable memory.
	
	tcp_max_ssthresh - INTEGER
		Limited Slow-Start for TCP with large congestion windows (cwnd) defined in
		RFC3742. Limited slow-start is a mechanism to limit growth of the cwnd
		on the region where cwnd is larger than tcp_max_ssthresh. TCP increases cwnd
		by at most tcp_max_ssthresh segments, and by at least tcp_max_ssthresh/2
		segments per RTT when the cwnd is above tcp_max_ssthresh.
		If TCP connection increased cwnd to thousands (or tens of thousands) segments,
		and thousands of packets were being dropped during slow-start, you can set
		tcp_max_ssthresh to improve performance for new TCP connection.
		Default: 0 (off)
	
	tcp_max_syn_backlog - INTEGER
		Maximal number of remembered connection requests, which have not
		received an acknowledgment from connecting client.
		The minimal value is 128 for low memory machines, and it will
		increase in proportion to the memory of machine.
		If server suffers from overload, try increasing this number.
	
	tcp_max_tw_buckets - INTEGER
		Maximal number of timewait sockets held by system simultaneously.
		If this number is exceeded time-wait socket is immediately destroyed
		and warning is printed. This limit exists only to prevent
		simple DoS attacks, you _must_ not lower the limit artificially,
		but rather increase it (probably, after increasing installed memory),
		if network conditions require more than default value.
	
	tcp_mem - vector of 3 INTEGERs: min, pressure, max
		min: below this number of pages TCP is not bothered about its
		memory appetite.
	
		pressure: when amount of memory allocated by TCP exceeds this number
		of pages, TCP moderates its memory consumption and enters memory
		pressure mode, which is exited when memory consumption falls
		under "min".
	
		max: number of pages allowed for queueing by all TCP sockets.
	
		Defaults are calculated at boot time from amount of available
		memory.
	
	tcp_moderate_rcvbuf - BOOLEAN
		If set, TCP performs receive buffer auto-tuning, attempting to
		automatically size the buffer (no greater than tcp_rmem[2]) to
		match the size required by the path for full throughput.  Enabled by
		default.
	
	tcp_mtu_probing - INTEGER
		Controls TCP Packetization-Layer Path MTU Discovery.  Takes three
		values:
		  0 - Disabled
		  1 - Disabled by default, enabled when an ICMP black hole detected
		  2 - Always enabled, use initial MSS of tcp_base_mss.
	
	tcp_no_metrics_save - BOOLEAN
		By default, TCP saves various connection metrics in the route cache
		when the connection closes, so that connections established in the
		near future can use these to set initial conditions.  Usually, this
		increases overall performance, but may sometimes cause performance
		degradation.  If set, TCP will not cache metrics on closing
		connections.
	
	tcp_orphan_retries - INTEGER
		This value influences the timeout of a locally closed TCP connection,
		when RTO retransmissions remain unacknowledged.
		See tcp_retries2 for more details.
	
		The default value is 8.
		If your machine is a loaded WEB server,
		you should think about lowering this value, such sockets
		may consume significant resources. Cf. tcp_max_orphans.
	
	tcp_reordering - INTEGER
		Maximal reordering of packets in a TCP stream.
		Default: 3
	
	tcp_retrans_collapse - BOOLEAN
		Bug-to-bug compatibility with some broken printers.
		On retransmit try to send bigger packets to work around bugs in
		certain TCP stacks.
	
	tcp_retries1 - INTEGER
		This value influences the time, after which TCP decides, that
		something is wrong due to unacknowledged RTO retransmissions,
		and reports this suspicion to the network layer.
		See tcp_retries2 for more details.
	
		RFC 1122 recommends at least 3 retransmissions, which is the
		default.
	
	tcp_retries2 - INTEGER
		This value influences the timeout of an alive TCP connection,
		when RTO retransmissions remain unacknowledged.
		Given a value of N, a hypothetical TCP connection following
		exponential backoff with an initial RTO of TCP_RTO_MIN would
		retransmit N times before killing the connection at the (N+1)th RTO.
	
		The default value of 15 yields a hypothetical timeout of 924.6
		seconds and is a lower bound for the effective timeout.
		TCP will effectively time out at the first RTO which exceeds the
		hypothetical timeout.
	
		RFC 1122 recommends at least 100 seconds for the timeout,
		which corresponds to a value of at least 8.
	
	tcp_rfc1337 - BOOLEAN
		If set, the TCP stack behaves conforming to RFC1337. If unset,
		we are not conforming to RFC, but prevent TCP TIME_WAIT
		assassination.
		Default: 0
	
	tcp_rmem - vector of 3 INTEGERs: min, default, max
		min: Minimal size of receive buffer used by TCP sockets.
		It is guaranteed to each TCP socket, even under moderate memory
		pressure.
		Default: 1 page
	
		default: initial size of receive buffer used by TCP sockets.
		This value overrides net.core.rmem_default used by other protocols.
		Default: 87380 bytes. This value results in window of 65535 with
		default setting of tcp_adv_win_scale and tcp_app_win:0 and a bit
		less for default tcp_app_win. See below about these variables.
	
		max: maximal size of receive buffer allowed for automatically
		selected receiver buffers for TCP socket. This value does not override
		net.core.rmem_max.  Calling setsockopt() with SO_RCVBUF disables
		automatic tuning of that socket's receive buffer size, in which
		case this value is ignored.
		Default: between 87380B and 4MB, depending on RAM size.
	
	tcp_sack - BOOLEAN
		Enable select acknowledgments (SACKS).
	
	tcp_slow_start_after_idle - BOOLEAN
		If set, provide RFC2861 behavior and time out the congestion
		window after an idle period.  An idle period is defined at
		the current RTO.  If unset, the congestion window will not
		be timed out after an idle period.
		Default: 1
	
	tcp_stdurg - BOOLEAN
		Use the Host requirements interpretation of the TCP urgent pointer field.
		Most hosts use the older BSD interpretation, so if you turn this on
		Linux might not communicate correctly with them.
		Default: FALSE
	
	tcp_synack_retries - INTEGER
		Number of times SYNACKs for a passive TCP connection attempt will
		be retransmitted. Should not be higher than 255. Default value
		is 5, which corresponds to ~180seconds.
	
	tcp_syncookies - BOOLEAN
		Only valid when the kernel was compiled with CONFIG_SYNCOOKIES
		Send out syncookies when the syn backlog queue of a socket
		overflows. This is to prevent against the common 'SYN flood attack'
		Default: FALSE
	
		Note, that syncookies is fallback facility.
		It MUST NOT be used to help highly loaded servers to stand
		against legal connection rate. If you see SYN flood warnings
		in your logs, but investigation	shows that they occur
		because of overload with legal connections, you should tune
		another parameters until this warning disappear.
		See: tcp_max_syn_backlog, tcp_synack_retries, tcp_abort_on_overflow.
	
		syncookies seriously violate TCP protocol, do not allow
		to use TCP extensions, can result in serious degradation
		of some services (f.e. SMTP relaying), visible not by you,
		but your clients and relays, contacting you. While you see
		SYN flood warnings in logs not being really flooded, your server
		is seriously misconfigured.
	
	tcp_syn_retries - INTEGER
		Number of times initial SYNs for an active TCP connection attempt
		will be retransmitted. Should not be higher than 255. Default value
		is 5, which corresponds to ~180seconds.
	
	tcp_timestamps - BOOLEAN
		Enable timestamps as defined in RFC1323.
	
	tcp_tso_win_divisor - INTEGER
		This allows control over what percentage of the congestion window
		can be consumed by a single TSO frame.
		The setting of this parameter is a choice between burstiness and
		building larger TSO frames.
		Default: 3
	
	tcp_tw_recycle - BOOLEAN
		Enable fast recycling TIME-WAIT sockets. Default value is 0.
		It should not be changed without advice/request of technical
		experts.
	
	tcp_tw_reuse - BOOLEAN
		Allow to reuse TIME-WAIT sockets for new connections when it is
		safe from protocol viewpoint. Default value is 0.
		It should not be changed without advice/request of technical
		experts.
	
	tcp_window_scaling - BOOLEAN
		Enable window scaling as defined in RFC1323.
	
	tcp_wmem - vector of 3 INTEGERs: min, default, max
		min: Amount of memory reserved for send buffers for TCP sockets.
		Each TCP socket has rights to use it due to fact of its birth.
		Default: 1 page
	
		default: initial size of send buffer used by TCP sockets.  This
		value overrides net.core.wmem_default used by other protocols.
		It is usually lower than net.core.wmem_default.
		Default: 16K
	
		max: Maximal amount of memory allowed for automatically tuned
		send buffers for TCP sockets. This value does not override
		net.core.wmem_max.  Calling setsockopt() with SO_SNDBUF disables
		automatic tuning of that socket's send buffer size, in which case
		this value is ignored.
		Default: between 64K and 4MB, depending on RAM size.
	
	tcp_workaround_signed_windows - BOOLEAN
		If set, assume no receipt of a window scaling option means the
		remote TCP is broken and treats the window as a signed quantity.
		If unset, assume the remote TCP is not broken even if we do
		not receive a window scaling option from them.
		Default: 0
	
	tcp_dma_copybreak - INTEGER
		Lower limit, in bytes, of the size of socket reads that will be
		offloaded to a DMA copy engine, if one is present in the system
		and CONFIG_NET_DMA is enabled.
		Default: 4096
	
	tcp_thin_linear_timeouts - BOOLEAN
		Enable dynamic triggering of linear timeouts for thin streams.
		If set, a check is performed upon retransmission by timeout to
		determine if the stream is thin (less than 4 packets in flight).
		As long as the stream is found to be thin, up to 6 linear
		timeouts may be performed before exponential backoff mode is
		initiated. This improves retransmission latency for
		non-aggressive thin streams, often found to be time-dependent.
		For more information on thin streams, see
		Documentation/networking/tcp-thin.txt
		Default: 0
	
	tcp_thin_dupack - BOOLEAN
		Enable dynamic triggering of retransmissions after one dupACK
		for thin streams. If set, a check is performed upon reception
		of a dupACK to determine if the stream is thin (less than 4
		packets in flight). As long as the stream is found to be thin,
		data is retransmitted on the first received dupACK. This
		improves retransmission latency for non-aggressive thin
		streams, often found to be time-dependent.
		For more information on thin streams, see
		Documentation/networking/tcp-thin.txt
		Default: 0
	
	UDP variables:
	
	udp_mem - vector of 3 INTEGERs: min, pressure, max
		Number of pages allowed for queueing by all UDP sockets.
	
		min: Below this number of pages UDP is not bothered about its
		memory appetite. When amount of memory allocated by UDP exceeds
		this number, UDP starts to moderate memory usage.
	
		pressure: This value was introduced to follow format of tcp_mem.
	
		max: Number of pages allowed for queueing by all UDP sockets.
	
		Default is calculated at boot time from amount of available memory.
	
	udp_rmem_min - INTEGER
		Minimal size of receive buffer used by UDP sockets in moderation.
		Each UDP socket is able to use the size for receiving data, even if
		total pages of UDP sockets exceed udp_mem pressure. The unit is byte.
		Default: 1 page
	
	udp_wmem_min - INTEGER
		Minimal size of send buffer used by UDP sockets in moderation.
		Each UDP socket is able to use the size for sending data, even if
		total pages of UDP sockets exceed udp_mem pressure. The unit is byte.
		Default: 1 page
	
	CIPSOv4 Variables:
	
	cipso_cache_enable - BOOLEAN
		If set, enable additions to and lookups from the CIPSO label mapping
		cache.  If unset, additions are ignored and lookups always result in a
		miss.  However, regardless of the setting the cache is still
		invalidated when required when means you can safely toggle this on and
		off and the cache will always be "safe".
		Default: 1
	
	cipso_cache_bucket_size - INTEGER
		The CIPSO label cache consists of a fixed size hash table with each
		hash bucket containing a number of cache entries.  This variable limits
		the number of entries in each hash bucket; the larger the value the
		more CIPSO label mappings that can be cached.  When the number of
		entries in a given hash bucket reaches this limit adding new entries
		causes the oldest entry in the bucket to be removed to make room.
		Default: 10
	
	cipso_rbm_optfmt - BOOLEAN
		Enable the "Optimized Tag 1 Format" as defined in section 3.4.2.6 of
		the CIPSO draft specification (see Documentation/netlabel for details).
		This means that when set the CIPSO tag will be padded with empty
		categories in order to make the packet data 32-bit aligned.
		Default: 0
	
	cipso_rbm_structvalid - BOOLEAN
		If set, do a very strict check of the CIPSO option when
		ip_options_compile() is called.  If unset, relax the checks done during
		ip_options_compile().  Either way is "safe" as errors are caught else
		where in the CIPSO processing code but setting this to 0 (False) should
		result in less work (i.e. it should be faster) but could cause problems
		with other implementations that require strict checking.
		Default: 0
	
	IP Variables:
	
	ip_local_port_range - 2 INTEGERS
		Defines the local port range that is used by TCP and UDP to
		choose the local port. The first number is the first, the
		second the last local port number. Default value depends on
		amount of memory available on the system:
		> 128Mb 32768-61000
		< 128Mb 1024-4999 or even less.
		This number defines number of active connections, which this
		system can issue simultaneously to systems not supporting
		TCP extensions (timestamps). With tcp_tw_recycle enabled
		(i.e. by default) range 1024-4999 is enough to issue up to
		2000 connections per second to systems supporting timestamps.
	
	ip_local_reserved_ports - list of comma separated ranges
		Specify the ports which are reserved for known third-party
		applications. These ports will not be used by automatic port
		assignments (e.g. when calling connect() or bind() with port
		number 0). Explicit port allocation behavior is unchanged.
	
		The format used for both input and output is a comma separated
		list of ranges (e.g. "1,2-4,10-10" for ports 1, 2, 3, 4 and
		10). Writing to the file will clear all previously reserved
		ports and update the current list with the one given in the
		input.
	
		Note that ip_local_port_range and ip_local_reserved_ports
		settings are independent and both are considered by the kernel
		when determining which ports are available for automatic port
		assignments.
	
		You can reserve ports which are not in the current
		ip_local_port_range, e.g.:
	
		$ cat /proc/sys/net/ipv4/ip_local_port_range
		32000	61000
		$ cat /proc/sys/net/ipv4/ip_local_reserved_ports
		8080,9148
	
		although this is redundant. However such a setting is useful
		if later the port range is changed to a value that will
		include the reserved ports.
	
		Default: Empty
	
	ip_nonlocal_bind - BOOLEAN
		If set, allows processes to bind() to non-local IP addresses,
		which can be quite useful - but may break some applications.
		Default: 0
	
	ip_dynaddr - BOOLEAN
		If set non-zero, enables support for dynamic addresses.
		If set to a non-zero value larger than 1, a kernel log
		message will be printed when dynamic address rewriting
		occurs.
		Default: 0
	
	icmp_echo_ignore_all - BOOLEAN
		If set non-zero, then the kernel will ignore all ICMP ECHO
		requests sent to it.
		Default: 0
	
	icmp_echo_ignore_broadcasts - BOOLEAN
		If set non-zero, then the kernel will ignore all ICMP ECHO and
		TIMESTAMP requests sent to it via broadcast/multicast.
		Default: 1
	
	icmp_ratelimit - INTEGER
		Limit the maximal rates for sending ICMP packets whose type matches
		icmp_ratemask (see below) to specific targets.
		0 to disable any limiting,
		otherwise the minimal space between responses in milliseconds.
		Default: 1000
	
	icmp_ratemask - INTEGER
		Mask made of ICMP types for which rates are being limited.
		Significant bits: IHGFEDCBA9876543210
		Default mask:     0000001100000011000 (6168)
	
		Bit definitions (see include/linux/icmp.h):
			0 Echo Reply
			3 Destination Unreachable *
			4 Source Quench *
			5 Redirect
			8 Echo Request
			B Time Exceeded *
			C Parameter Problem *
			D Timestamp Request
			E Timestamp Reply
			F Info Request
			G Info Reply
			H Address Mask Request
			I Address Mask Reply
	
		* These are rate limited by default (see default mask above)
	
	icmp_ignore_bogus_error_responses - BOOLEAN
		Some routers violate RFC1122 by sending bogus responses to broadcast
		frames.  Such violations are normally logged via a kernel warning.
		If this is set to TRUE, the kernel will not give such warnings, which
		will avoid log file clutter.
		Default: FALSE
	
	icmp_errors_use_inbound_ifaddr - BOOLEAN
	
		If zero, icmp error messages are sent with the primary address of
		the exiting interface.
	
		If non-zero, the message will be sent with the primary address of
		the interface that received the packet that caused the icmp error.
		This is the behaviour network many administrators will expect from
		a router. And it can make debugging complicated network layouts
		much easier.
	
		Note that if no primary address exists for the interface selected,
		then the primary address of the first non-loopback interface that
		has one will be used regardless of this setting.
	
		Default: 0
	
	igmp_max_memberships - INTEGER
		Change the maximum number of multicast groups we can subscribe to.
		Default: 20
	
		Theoretical maximum value is bounded by having to send a membership
		report in a single datagram (i.e. the report can't span multiple
		datagrams, or risk confusing the switch and leaving groups you don't
		intend to).
	
		The number of supported groups 'M' is bounded by the number of group
		report entries you can fit into a single datagram of 65535 bytes.
	
		M = 65536-sizeof (ip header)/(sizeof(Group record))
	
		Group records are variable length, with a minimum of 12 bytes.
		So net.ipv4.igmp_max_memberships should not be set higher than:
	
		(65536-24) / 12 = 5459
	
		The value 5459 assumes no IP header options, so in practice
		this number may be lower.
	
		conf/interface/*  changes special settings per interface (where
		"interface" is the name of your network interface)
	
		conf/all/*	  is special, changes the settings for all interfaces
	
	log_martians - BOOLEAN
		Log packets with impossible addresses to kernel log.
		log_martians for the interface will be enabled if at least one of
		conf/{all,interface}/log_martians is set to TRUE,
		it will be disabled otherwise
	
	accept_redirects - BOOLEAN
		Accept ICMP redirect messages.
		accept_redirects for the interface will be enabled if:
		- both conf/{all,interface}/accept_redirects are TRUE in the case
		  forwarding for the interface is enabled
		or
		- at least one of conf/{all,interface}/accept_redirects is TRUE in the
		  case forwarding for the interface is disabled
		accept_redirects for the interface will be disabled otherwise
		default TRUE (host)
			FALSE (router)
	
	forwarding - BOOLEAN
		Enable IP forwarding on this interface.
	
	mc_forwarding - BOOLEAN
		Do multicast routing. The kernel needs to be compiled with CONFIG_MROUTE
		and a multicast routing daemon is required.
		conf/all/mc_forwarding must also be set to TRUE to enable multicast
		routing	for the interface
	
	medium_id - INTEGER
		Integer value used to differentiate the devices by the medium they
		are attached to. Two devices can have different id values when
		the broadcast packets are received only on one of them.
		The default value 0 means that the device is the only interface
		to its medium, value of -1 means that medium is not known.
	
		Currently, it is used to change the proxy_arp behavior:
		the proxy_arp feature is enabled for packets forwarded between
		two devices attached to different media.
	
	proxy_arp - BOOLEAN
		Do proxy arp.
		proxy_arp for the interface will be enabled if at least one of
		conf/{all,interface}/proxy_arp is set to TRUE,
		it will be disabled otherwise
	
	proxy_arp_pvlan - BOOLEAN
		Private VLAN proxy arp.
		Basically allow proxy arp replies back to the same interface
		(from which the ARP request/solicitation was received).
	
		This is done to support (ethernet) switch features, like RFC
		3069, where the individual ports are NOT allowed to
		communicate with each other, but they are allowed to talk to
		the upstream router.  As described in RFC 3069, it is possible
		to allow these hosts to communicate through the upstream
		router by proxy_arp'ing. Don't need to be used together with
		proxy_arp.
	
		This technology is known by different names:
		  In RFC 3069 it is called VLAN Aggregation.
		  Cisco and Allied Telesyn call it Private VLAN.
		  Hewlett-Packard call it Source-Port filtering or port-isolation.
		  Ericsson call it MAC-Forced Forwarding (RFC Draft).
	
	shared_media - BOOLEAN
		Send(router) or accept(host) RFC1620 shared media redirects.
		Overrides ip_secure_redirects.
		shared_media for the interface will be enabled if at least one of
		conf/{all,interface}/shared_media is set to TRUE,
		it will be disabled otherwise
		default TRUE
	
	secure_redirects - BOOLEAN
		Accept ICMP redirect messages only for gateways,
		listed in default gateway list.
		secure_redirects for the interface will be enabled if at least one of
		conf/{all,interface}/secure_redirects is set to TRUE,
		it will be disabled otherwise
		default TRUE
	
	send_redirects - BOOLEAN
		Send redirects, if router.
		send_redirects for the interface will be enabled if at least one of
		conf/{all,interface}/send_redirects is set to TRUE,
		it will be disabled otherwise
		Default: TRUE
	
	bootp_relay - BOOLEAN
		Accept packets with source address 0.b.c.d destined
		not to this host as local ones. It is supposed, that
		BOOTP relay daemon will catch and forward such packets.
		conf/all/bootp_relay must also be set to TRUE to enable BOOTP relay
		for the interface
		default FALSE
		Not Implemented Yet.
	
	accept_source_route - BOOLEAN
		Accept packets with SRR option.
		conf/all/accept_source_route must also be set to TRUE to accept packets
		with SRR option on the interface
		default TRUE (router)
			FALSE (host)
	
	accept_local - BOOLEAN
		Accept packets with local source addresses. In combination with
		suitable routing, this can be used to direct packets between two
		local interfaces over the wire and have them accepted properly.
		default FALSE
	
	rp_filter - INTEGER
		0 - No source validation.
		1 - Strict mode as defined in RFC3704 Strict Reverse Path
		    Each incoming packet is tested against the FIB and if the interface
		    is not the best reverse path the packet check will fail.
		    By default failed packets are discarded.
		2 - Loose mode as defined in RFC3704 Loose Reverse Path
		    Each incoming packet's source address is also tested against the FIB
		    and if the source address is not reachable via any interface
		    the packet check will fail.
	
		Current recommended practice in RFC3704 is to enable strict mode
		to prevent IP spoofing from DDos attacks. If using asymmetric routing
		or other complicated routing, then loose mode is recommended.
	
		The max value from conf/{all,interface}/rp_filter is used
		when doing source validation on the {interface}.
	
		Default value is 0. Note that some distributions enable it
		in startup scripts.
	
	arp_filter - BOOLEAN
		1 - Allows you to have multiple network interfaces on the same
		subnet, and have the ARPs for each interface be answered
		based on whether or not the kernel would route a packet from
		the ARP'd IP out that interface (therefore you must use source
		based routing for this to work). In other words it allows control
		of which cards (usually 1) will respond to an arp request.
	
		0 - (default) The kernel can respond to arp requests with addresses
		from other interfaces. This may seem wrong but it usually makes
		sense, because it increases the chance of successful communication.
		IP addresses are owned by the complete host on Linux, not by
		particular interfaces. Only for more complex setups like load-
		balancing, does this behaviour cause problems.
	
		arp_filter for the interface will be enabled if at least one of
		conf/{all,interface}/arp_filter is set to TRUE,
		it will be disabled otherwise
	
	arp_announce - INTEGER
		Define different restriction levels for announcing the local
		source IP address from IP packets in ARP requests sent on
		interface:
		0 - (default) Use any local address, configured on any interface
		1 - Try to avoid local addresses that are not in the target's
		subnet for this interface. This mode is useful when target
		hosts reachable via this interface require the source IP
		address in ARP requests to be part of their logical network
		configured on the receiving interface. When we generate the
		request we will check all our subnets that include the
		target IP and will preserve the source address if it is from
		such subnet. If there is no such subnet we select source
		address according to the rules for level 2.
		2 - Always use the best local address for this target.
		In this mode we ignore the source address in the IP packet
		and try to select local address that we prefer for talks with
		the target host. Such local address is selected by looking
		for primary IP addresses on all our subnets on the outgoing
		interface that include the target IP address. If no suitable
		local address is found we select the first local address
		we have on the outgoing interface or on all other interfaces,
		with the hope we will receive reply for our request and
		even sometimes no matter the source IP address we announce.
	
		The max value from conf/{all,interface}/arp_announce is used.
	
		Increasing the restriction level gives more chance for
		receiving answer from the resolved target while decreasing
		the level announces more valid sender's information.
	
	arp_ignore - INTEGER
		Define different modes for sending replies in response to
		received ARP requests that resolve local target IP addresses:
		0 - (default): reply for any local target IP address, configured
		on any interface
		1 - reply only if the target IP address is local address
		configured on the incoming interface
		2 - reply only if the target IP address is local address
		configured on the incoming interface and both with the
		sender's IP address are part from same subnet on this interface
		3 - do not reply for local addresses configured with scope host,
		only resolutions for global and link addresses are replied
		4-7 - reserved
		8 - do not reply for all local addresses
	
		The max value from conf/{all,interface}/arp_ignore is used
		when ARP request is received on the {interface}
	
	arp_notify - BOOLEAN
		Define mode for notification of address and device changes.
		0 - (default): do nothing
		1 - Generate gratuitous arp requests when device is brought up
		    or hardware address changes.
	
	arp_accept - BOOLEAN
		Define behavior for gratuitous ARP frames who's IP is not
		already present in the ARP table:
		0 - don't create new entries in the ARP table
		1 - create new entries in the ARP table
	
		Both replies and requests type gratuitous arp will trigger the
		ARP table to be updated, if this setting is on.
	
		If the ARP table already contains the IP address of the
		gratuitous arp frame, the arp table will be updated regardless
		if this setting is on or off.
	
	
	app_solicit - INTEGER
		The maximum number of probes to send to the user space ARP daemon
		via netlink before dropping back to multicast probes (see
		mcast_solicit).  Defaults to 0.
	
	disable_policy - BOOLEAN
		Disable IPSEC policy (SPD) for this interface
	
	disable_xfrm - BOOLEAN
		Disable IPSEC encryption on this interface, whatever the policy
	
	
	
	tag - INTEGER
		Allows you to write a number, which can be used as required.
		Default value is 0.
	
	Alexey Kuznetsov.
	kuznet@ms2.inr.ac.ru
	
	Updated by:
	Andi Kleen
	ak@muc.de
	Nicolas Delon
	delon.nicolas@wanadoo.fr
	
	
	
	
	/proc/sys/net/ipv6/* Variables:
	
	IPv6 has no global variables such as tcp_*.  tcp_* settings under ipv4/ also
	apply to IPv6 [XXX?].
	
	bindv6only - BOOLEAN
		Default value for IPV6_V6ONLY socket option,
		which restricts use of the IPv6 socket to IPv6 communication
		only.
			TRUE: disable IPv4-mapped address feature
			FALSE: enable IPv4-mapped address feature
	
		Default: FALSE (as specified in RFC3493)
	
	IPv6 Fragmentation:
	
	ip6frag_high_thresh - INTEGER
		Maximum memory used to reassemble IPv6 fragments. When
		ip6frag_high_thresh bytes of memory is allocated for this purpose,
		the fragment handler will toss packets until ip6frag_low_thresh
		is reached.
	
	ip6frag_low_thresh - INTEGER
		See ip6frag_high_thresh
	
	ip6frag_time - INTEGER
		Time in seconds to keep an IPv6 fragment in memory.
	
	ip6frag_secret_interval - INTEGER
		Regeneration interval (in seconds) of the hash secret (or lifetime
		for the hash secret) for IPv6 fragments.
		Default: 600
	
	conf/default/*:
		Change the interface-specific default settings.
	
	
	conf/all/*:
		Change all the interface-specific settings.
	
		[XXX:  Other special features than forwarding?]
	
	conf/all/forwarding - BOOLEAN
		Enable global IPv6 forwarding between all interfaces.
	
		IPv4 and IPv6 work differently here; e.g. netfilter must be used
		to control which interfaces may forward packets and which not.
	
		This also sets all interfaces' Host/Router setting
		'forwarding' to the specified value.  See below for details.
	
		This referred to as global forwarding.
	
	proxy_ndp - BOOLEAN
		Do proxy ndp.
	
	conf/interface/*:
		Change special settings per interface.
	
		The functional behaviour for certain settings is different
		depending on whether local forwarding is enabled or not.
	
	accept_ra - INTEGER
		Accept Router Advertisements; autoconfigure using them.
	
		It also determines whether or not to transmit Router
		Solicitations. If and only if the functional setting is to
		accept Router Advertisements, Router Solicitations will be
		transmitted.
	
		Possible values are:
			0 Do not accept Router Advertisements.
			1 Accept Router Advertisements if forwarding is disabled.
			2 Overrule forwarding behaviour. Accept Router Advertisements
			  even if forwarding is enabled.
	
		Functional default: enabled if local forwarding is disabled.
				    disabled if local forwarding is enabled.
	
	accept_ra_defrtr - BOOLEAN
		Learn default router in Router Advertisement.
	
		Functional default: enabled if accept_ra is enabled.
				    disabled if accept_ra is disabled.
	
	accept_ra_pinfo - BOOLEAN
		Learn Prefix Information in Router Advertisement.
	
		Functional default: enabled if accept_ra is enabled.
				    disabled if accept_ra is disabled.
	
	accept_ra_rt_info_max_plen - INTEGER
		Maximum prefix length of Route Information in RA.
	
		Route Information w/ prefix larger than or equal to this
		variable shall be ignored.
	
		Functional default: 0 if accept_ra_rtr_pref is enabled.
				    -1 if accept_ra_rtr_pref is disabled.
	
	accept_ra_rtr_pref - BOOLEAN
		Accept Router Preference in RA.
	
		Functional default: enabled if accept_ra is enabled.
				    disabled if accept_ra is disabled.
	
	accept_redirects - BOOLEAN
		Accept Redirects.
	
		Functional default: enabled if local forwarding is disabled.
				    disabled if local forwarding is enabled.
	
	accept_source_route - INTEGER
		Accept source routing (routing extension header).
	
		>= 0: Accept only routing header type 2.
		< 0: Do not accept routing header.
	
		Default: 0
	
	autoconf - BOOLEAN
		Autoconfigure addresses using Prefix Information in Router
		Advertisements.
	
		Functional default: enabled if accept_ra_pinfo is enabled.
				    disabled if accept_ra_pinfo is disabled.
	
	dad_transmits - INTEGER
		The amount of Duplicate Address Detection probes to send.
		Default: 1
	
	forwarding - INTEGER
		Configure interface-specific Host/Router behaviour.
	
		Note: It is recommended to have the same setting on all
		interfaces; mixed router/host scenarios are rather uncommon.
	
		Possible values are:
			0 Forwarding disabled
			1 Forwarding enabled
	
		FALSE (0):
	
		By default, Host behaviour is assumed.  This means:
	
		1. IsRouter flag is not set in Neighbour Advertisements.
		2. If accept_ra is TRUE (default), transmit Router
		   Solicitations.
		3. If accept_ra is TRUE (default), accept Router
		   Advertisements (and do autoconfiguration).
		4. If accept_redirects is TRUE (default), accept Redirects.
	
		TRUE (1):
	
		If local forwarding is enabled, Router behaviour is assumed.
		This means exactly the reverse from the above:
	
		1. IsRouter flag is set in Neighbour Advertisements.
		2. Router Solicitations are not sent unless accept_ra is 2.
		3. Router Advertisements are ignored unless accept_ra is 2.
		4. Redirects are ignored.
	
		Default: 0 (disabled) if global forwarding is disabled (default),
			 otherwise 1 (enabled).
	
	hop_limit - INTEGER
		Default Hop Limit to set.
		Default: 64
	
	mtu - INTEGER
		Default Maximum Transfer Unit
		Default: 1280 (IPv6 required minimum)
	
	router_probe_interval - INTEGER
		Minimum interval (in seconds) between Router Probing described
		in RFC4191.
	
		Default: 60
	
	router_solicitation_delay - INTEGER
		Number of seconds to wait after interface is brought up
		before sending Router Solicitations.
		Default: 1
	
	router_solicitation_interval - INTEGER
		Number of seconds to wait between Router Solicitations.
		Default: 4
	
	router_solicitations - INTEGER
		Number of Router Solicitations to send until assuming no
		routers are present.
		Default: 3
	
	use_tempaddr - INTEGER
		Preference for Privacy Extensions (RFC3041).
		  <= 0 : disable Privacy Extensions
		  == 1 : enable Privacy Extensions, but prefer public
		         addresses over temporary addresses.
		  >  1 : enable Privacy Extensions and prefer temporary
		         addresses over public addresses.
		Default:  0 (for most devices)
			 -1 (for point-to-point devices and loopback devices)
	
	temp_valid_lft - INTEGER
		valid lifetime (in seconds) for temporary addresses.
		Default: 604800 (7 days)
	
	temp_prefered_lft - INTEGER
		Preferred lifetime (in seconds) for temporary addresses.
		Default: 86400 (1 day)
	
	max_desync_factor - INTEGER
		Maximum value for DESYNC_FACTOR, which is a random value
		that ensures that clients don't synchronize with each
		other and generate new addresses at exactly the same time.
		value is in seconds.
		Default: 600
	
	regen_max_retry - INTEGER
		Number of attempts before give up attempting to generate
		valid temporary addresses.
		Default: 5
	
	max_addresses - INTEGER
		Maximum number of autoconfigured addresses per interface.  Setting
		to zero disables the limitation.  It is not recommended to set this
		value too large (or to zero) because it would be an easy way to
		crash the kernel by allowing too many addresses to be created.
		Default: 16
	
	disable_ipv6 - BOOLEAN
		Disable IPv6 operation.  If accept_dad is set to 2, this value
		will be dynamically set to TRUE if DAD fails for the link-local
		address.
		Default: FALSE (enable IPv6 operation)
	
		When this value is changed from 1 to 0 (IPv6 is being enabled),
		it will dynamically create a link-local address on the given
		interface and start Duplicate Address Detection, if necessary.
	
		When this value is changed from 0 to 1 (IPv6 is being disabled),
		it will dynamically delete all address on the given interface.
	
	accept_dad - INTEGER
		Whether to accept DAD (Duplicate Address Detection).
		0: Disable DAD
		1: Enable DAD (default)
		2: Enable DAD, and disable IPv6 operation if MAC-based duplicate
		   link-local address has been found.
	
	force_tllao - BOOLEAN
		Enable sending the target link-layer address option even when
		responding to a unicast neighbor solicitation.
		Default: FALSE
	
		Quoting from RFC 2461, section 4.4, Target link-layer address:
	
		"The option MUST be included for multicast solicitations in order to
		avoid infinite Neighbor Solicitation "recursion" when the peer node
		does not have a cache entry to return a Neighbor Advertisements
		message.  When responding to unicast solicitations, the option can be
		omitted since the sender of the solicitation has the correct link-
		layer address; otherwise it would not have be able to send the unicast
		solicitation in the first place. However, including the link-layer
		address in this case adds little overhead and eliminates a potential
		race condition where the sender deletes the cached link-layer address
		prior to receiving a response to a previous solicitation."
	
	icmp/*:
	ratelimit - INTEGER
		Limit the maximal rates for sending ICMPv6 packets.
		0 to disable any limiting,
		otherwise the minimal space between responses in milliseconds.
		Default: 1000
	
	
	IPv6 Update by:
	Pekka Savola <pekkas@netcore.fi>
	YOSHIFUJI Hideaki / USAGI Project <yoshfuji@linux-ipv6.org>
	
	
	/proc/sys/net/bridge/* Variables:
	
	bridge-nf-call-arptables - BOOLEAN
		1 : pass bridged ARP traffic to arptables' FORWARD chain.
		0 : disable this.
		Default: 1
	
	bridge-nf-call-iptables - BOOLEAN
		1 : pass bridged IPv4 traffic to iptables' chains.
		0 : disable this.
		Default: 1
	
	bridge-nf-call-ip6tables - BOOLEAN
		1 : pass bridged IPv6 traffic to ip6tables' chains.
		0 : disable this.
		Default: 1
	
	bridge-nf-filter-vlan-tagged - BOOLEAN
		1 : pass bridged vlan-tagged ARP/IP/IPv6 traffic to {arp,ip,ip6}tables.
		0 : disable this.
		Default: 1
	
	bridge-nf-filter-pppoe-tagged - BOOLEAN
		1 : pass bridged pppoe-tagged IP/IPv6 traffic to {ip,ip6}tables.
		0 : disable this.
		Default: 1
	
	
	proc/sys/net/sctp/* Variables:
	
	addip_enable - BOOLEAN
		Enable or disable extension of  Dynamic Address Reconfiguration
		(ADD-IP) functionality specified in RFC5061.  This extension provides
		the ability to dynamically add and remove new addresses for the SCTP
		associations.
	
		1: Enable extension.
	
		0: Disable extension.
	
		Default: 0
	
	addip_noauth_enable - BOOLEAN
		Dynamic Address Reconfiguration (ADD-IP) requires the use of
		authentication to protect the operations of adding or removing new
		addresses.  This requirement is mandated so that unauthorized hosts
		would not be able to hijack associations.  However, older
		implementations may not have implemented this requirement while
		allowing the ADD-IP extension.  For reasons of interoperability,
		we provide this variable to control the enforcement of the
		authentication requirement.
	
		1: Allow ADD-IP extension to be used without authentication.  This
		   should only be set in a closed environment for interoperability
		   with older implementations.
	
		0: Enforce the authentication requirement
	
		Default: 0
	
	auth_enable - BOOLEAN
		Enable or disable Authenticated Chunks extension.  This extension
		provides the ability to send and receive authenticated chunks and is
		required for secure operation of Dynamic Address Reconfiguration
		(ADD-IP) extension.
	
		1: Enable this extension.
		0: Disable this extension.
	
		Default: 0
	
	prsctp_enable - BOOLEAN
		Enable or disable the Partial Reliability extension (RFC3758) which
		is used to notify peers that a given DATA should no longer be expected.
	
		1: Enable extension
		0: Disable
	
		Default: 1
	
	max_burst - INTEGER
		The limit of the number of new packets that can be initially sent.  It
		controls how bursty the generated traffic can be.
	
		Default: 4
	
	association_max_retrans - INTEGER
		Set the maximum number for retransmissions that an association can
		attempt deciding that the remote end is unreachable.  If this value
		is exceeded, the association is terminated.
	
		Default: 10
	
	max_init_retransmits - INTEGER
		The maximum number of retransmissions of INIT and COOKIE-ECHO chunks
		that an association will attempt before declaring the destination
		unreachable and terminating.
	
		Default: 8
	
	path_max_retrans - INTEGER
		The maximum number of retransmissions that will be attempted on a given
		path.  Once this threshold is exceeded, the path is considered
		unreachable, and new traffic will use a different path when the
		association is multihomed.
	
		Default: 5
	
	rto_initial - INTEGER
		The initial round trip timeout value in milliseconds that will be used
		in calculating round trip times.  This is the initial time interval
		for retransmissions.
	
		Default: 3000
	
	rto_max - INTEGER
		The maximum value (in milliseconds) of the round trip timeout.  This
		is the largest time interval that can elapse between retransmissions.
	
		Default: 60000
	
	rto_min - INTEGER
		The minimum value (in milliseconds) of the round trip timeout.  This
		is the smallest time interval the can elapse between retransmissions.
	
		Default: 1000
	
	hb_interval - INTEGER
		The interval (in milliseconds) between HEARTBEAT chunks.  These chunks
		are sent at the specified interval on idle paths to probe the state of
		a given path between 2 associations.
	
		Default: 30000
	
	sack_timeout - INTEGER
		The amount of time (in milliseconds) that the implementation will wait
		to send a SACK.
	
		Default: 200
	
	valid_cookie_life - INTEGER
		The default lifetime of the SCTP cookie (in milliseconds).  The cookie
		is used during association establishment.
	
		Default: 60000
	
	cookie_preserve_enable - BOOLEAN
		Enable or disable the ability to extend the lifetime of the SCTP cookie
		that is used during the establishment phase of SCTP association
	
		1: Enable cookie lifetime extension.
		0: Disable
	
		Default: 1
	
	rcvbuf_policy - INTEGER
		Determines if the receive buffer is attributed to the socket or to
		association.   SCTP supports the capability to create multiple
		associations on a single socket.  When using this capability, it is
		possible that a single stalled association that's buffering a lot
		of data may block other associations from delivering their data by
		consuming all of the receive buffer space.  To work around this,
		the rcvbuf_policy could be set to attribute the receiver buffer space
		to each association instead of the socket.  This prevents the described
		blocking.
	
		1: rcvbuf space is per association
		0: recbuf space is per socket
	
		Default: 0
	
	sndbuf_policy - INTEGER
		Similar to rcvbuf_policy above, this applies to send buffer space.
	
		1: Send buffer is tracked per association
		0: Send buffer is tracked per socket.
	
		Default: 0
	
	sctp_mem - vector of 3 INTEGERs: min, pressure, max
		Number of pages allowed for queueing by all SCTP sockets.
	
		min: Below this number of pages SCTP is not bothered about its
		memory appetite. When amount of memory allocated by SCTP exceeds
		this number, SCTP starts to moderate memory usage.
	
		pressure: This value was introduced to follow format of tcp_mem.
	
		max: Number of pages allowed for queueing by all SCTP sockets.
	
		Default is calculated at boot time from amount of available memory.
	
	sctp_rmem - vector of 3 INTEGERs: min, default, max
		Only the first value ("min") is used, "default" and "max" are
		ignored.
	
		min: Minimal size of receive buffer used by SCTP socket.
		It is guaranteed to each SCTP socket (but not association) even
		under moderate memory pressure.
	
		Default: 1 page
	
	sctp_wmem  - vector of 3 INTEGERs: min, default, max
		Currently this tunable has no effect.
	
	addr_scope_policy - INTEGER
		Control IPv4 address scoping - draft-stewart-tsvwg-sctp-ipv4-00
	
		0   - Disable IPv4 address scoping
		1   - Enable IPv4 address scoping
		2   - Follow draft but allow IPv4 private addresses
		3   - Follow draft but allow IPv4 link local addresses
	
		Default: 1
	
	
	/proc/sys/net/core/*
	dev_weight - INTEGER
		The maximum number of packets that kernel can handle on a NAPI
		interrupt, it's a Per-CPU variable.
	
		Default: 64
	
	/proc/sys/net/unix/*
	max_dgram_qlen - INTEGER
		The maximum length of dgram socket receive queue
	
		Default: 10
	
	
	UNDOCUMENTED:
	
	/proc/sys/net/irda/*
		fast_poll_increase FIXME
		warn_noreply_time FIXME
		discovery_slots FIXME
		slot_timeout FIXME
		max_baud_rate FIXME
		discovery_timeout FIXME
		lap_keepalive_time FIXME
		max_noreply_time FIXME
		max_tx_data_size FIXME
		max_tx_window FIXME
		min_tx_turn_time FIXME

• [ networking ]
• 00-INDEX
• 3c359.txt
• 3c505.txt
• 3c509.txt
• 6pack.txt
• alias.txt
• arcnet-hardware.txt
• arcnet.txt
• atm.txt
• ax25.txt
• batman-adv.txt
• baycom.txt
• bonding.txt
• bridge.txt
• [ caif ]
• can.txt
• cops.txt
• cs89x0.txt
• cxacru-cf.py
• cxacru.txt
• cxgb.txt
• dccp.txt
• de4x5.txt
• decnet.txt
• depca.txt
• dl2k.txt
• DLINK.txt
• dm9000.txt
• dmfe.txt
• dns_resolver.txt
• driver.txt
• e100.txt
• e1000.txt
• e1000e.txt
• eql.txt
• ewrk3.txt
• fib_trie.txt
• filter.txt
• fore200e.txt
• framerelay.txt
• gen_stats.txt
• generic-hdlc.txt
• generic_netlink.txt
• gianfar.txt
• ieee802154.txt
• ifenslave.c
• igb.txt
• igbvf.txt
• ip-sysctl.txt
• ip_dynaddr.txt
• ipddp.txt
• iphase.txt
• ipv6.txt
• ipvs-sysctl.txt
• irda.txt
• ixgb.txt
• ixgbe.txt
• ixgbevf.txt
• l2tp.txt
• lapb-module.txt
• LICENSE.qla3xxx
• LICENSE.qlcnic
• LICENSE.qlge
• ltpc.txt
• mac80211-injection.txt
• [ mac80211_hwsim ]
• Makefile
• multicast.txt
• multiqueue.txt
• netconsole.txt
• netdev-features.txt
• netdevices.txt
• netif-msg.txt
• nfc.txt
• olympic.txt
• operstates.txt
• packet_mmap.txt
• phonet.txt
• phy.txt
• pktgen.txt
• PLIP.txt
• policy-routing.txt
• ppp_generic.txt
• proc_net_tcp.txt
• radiotap-headers.txt
• ray_cs.txt
• rds.txt
• README.ipw2100
• README.ipw2200
• README.sb1000
• regulatory.txt
• rxrpc.txt
• s2io.txt
• scaling.txt
• sctp.txt
• secid.txt
• skfp.txt
• smc9.txt
• smctr.txt
• spider_net.txt
• stmmac.txt
• tc-actions-env-rules.txt
• tcp-thin.txt
• tcp.txt
• [ timestamping ]
• timestamping.txt
• tlan.txt
• tms380tr.txt
• tproxy.txt
• tuntap.txt
• udplite.txt
• vortex.txt
• vxge.txt
• x25-iface.txt
• x25.txt
• xfrm_proc.txt
• xfrm_sync.txt
• xfrm_sysctl.txt
• z8530drv.txt
•