# ip-tcp_metrics(8) - man - phpMan

[IP-TCP_METRICS(8)](https://www.chedong.com/phpMan.php/man/IP-TCPMETRICS/8/markdown)                               Linux                              [IP-TCP_METRICS(8)](https://www.chedong.com/phpMan.php/man/IP-TCPMETRICS/8/markdown)



## 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 informa‐
       tion 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 in‐
       formation, sometimes reclaimed and used for new destinations. The kernel never removes en‐
       tries, 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 sock‐
       ets. 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)](https://www.chedong.com/phpMan.php/man/ip/8/markdown)


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



iproute2                                     23 Aug 2012                           [IP-TCP_METRICS(8)](https://www.chedong.com/phpMan.php/man/IP-TCPMETRICS/8/markdown)