IP\-TCP_METRICS
Section: Linux (8)
Updated: 23 Aug 2012
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NAME
ip-tcp_metrics - management for TCP Metrics
SYNOPSIS
ip
[ OPTIONS ]
tcp_metrics
{ COMMAND |
help }
ip tcp_metrics { show | flush }
SELECTOR
ip tcp_metrics delete [ address ]
ADDRESS
SELECTOR :=
[ [ address ]
PREFIX ]
DESCRIPTION
ip tcp_metrics
is used to manipulate entries in the kernel that keep TCP information
for IPv4 and IPv6 destinations. The entries are created when
TCP sockets want to share information for destinations and are
stored in a cache keyed by the destination address. The saved
information may include values for metrics (initially obtained from
routes), recent TSVAL for TIME-WAIT recycling purposes, state for the
Fast Open feature, etc.
For performance reasons the cache can not grow above configured limit
and the older entries are replaced with fresh information, sometimes
reclaimed and used for new destinations. The kernel never removes
entries, they can be flushed only with this tool.
ip tcp_metrics show - show cached entries
- address PREFIX (default)
-
IPv4/IPv6 prefix or address. If no prefix is provided all entries are shown.
The output may contain the following information:
age <S.MMM>sec
- time after the entry was created, reset or updated with metrics
from sockets. The entry is reset and refreshed on use with metrics from
route if the metrics are not updated in last hour. Not all cached values
reset the age on update.
cwnd <N>
- CWND metric value
fo_cookie <HEX-STRING>
- Cookie value received in SYN-ACK to be used by Fast Open for next SYNs
fo_mss <N>
- MSS value received in SYN-ACK to be used by Fast Open for next SYNs
fo_syn_drops <N>/<S.MMM>sec ago
- Number of drops of initial outgoing Fast Open SYNs with data
detected by monitoring the received SYN-ACK after SYN retransmission.
The seconds show the time after last SYN drop and together with
the drop count can be used to disable Fast Open for some time.
reordering <N>
- Reordering metric value
rtt <N>us
- RTT metric value
rttvar <N>us
- RTTVAR metric value
ssthresh <SSTHRESH>
- SSTHRESH metric value
tw_ts <TSVAL>/<SEC>sec ago
- recent TSVAL and the seconds after saving it into TIME-WAIT socket
ip tcp_metrics delete - delete single entry
- address ADDRESS (default)
-
IPv4/IPv6 address. The address is a required argument.
ip tcp_metrics flush - flush entries
This command flushes the entries selected by some criteria.
This command has the same arguments as
show.
EXAMPLES
ip tcp_metrics show address 192.168.0.0/24
-
Shows the entries for destinations from subnet
ip tcp_metrics show 192.168.0.0/24
-
The same but address keyword is optional
ip tcp_metrics
-
Show all is the default action
ip tcp_metrics delete 192.168.0.1
-
Removes the entry for 192.168.0.1 from cache.
ip tcp_metrics flush 192.168.0.0/24
-
Removes entries for destinations from subnet
ip tcp_metrics flush all
-
Removes all entries from cache
ip -6 tcp_metrics flush all
-
Removes all IPv6 entries from cache keeping the IPv4 entries.
SEE ALSO
ip(8)
AUTHOR
Original Manpage by Julian Anastasov <
ja@ssi.bg>
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- ip tcp_metrics show - show cached entries
-
- ip tcp_metrics delete - delete single entry
-
- ip tcp_metrics flush - flush entries
-
- EXAMPLES
-
- SEE ALSO
-
- AUTHOR
-
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