ip-tcp_metrics(8) — Linux manual page


IP-TCP_METRICS(8)                 Linux                IP-TCP_METRICS(8)

NAME         top

       ip-tcp_metrics - management for TCP Metrics

SYNOPSIS         top

       ip [ OPTIONS ] tcp_metrics { COMMAND | help }

       ip tcp_metrics { show | flush } SELECTOR

       ip tcp_metrics delete [ address ] ADDRESS

       SELECTOR := [ [ address ] PREFIX ]

DESCRIPTION         top

       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

       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         top

       ip tcp_metrics show address
           Shows the entries for destinations from subnet

       ip tcp_metrics show
           The same but address keyword is optional

       ip tcp_metrics
           Show all is the default action

       ip tcp_metrics delete
           Removes the entry for from cache.

       ip tcp_metrics flush
           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         top


AUTHOR         top

       Original Manpage by Julian Anastasov <ja@ssi.bg>

COLOPHON         top

       This page is part of the iproute2 (utilities for controlling
       TCP/IP networking and traffic) project.  Information about the
       project can be found at 
       If you have a bug report for this manual page, send it to
       netdev@vger.kernel.org, shemminger@osdl.org.  This page was
       obtained from the project's upstream Git repository
       ⟨https://git.kernel.org/pub/scm/network/iproute2/iproute2.git⟩ on
       2024-06-14.  (At that time, the date of the most recent commit
       that was found in the repository was 2024-06-11.)  If you
       discover any rendering problems in this HTML version of the page,
       or you believe there is a better or more up-to-date source for
       the page, or you have corrections or improvements to the
       information in this COLOPHON (which is not part of the original
       manual page), send a mail to man-pages@man7.org

iproute2                       23 Aug 2012             IP-TCP_METRICS(8)

Pages that refer to this page: ip(8)