1IP-TCP_METRICS(8)                    Linux                   IP-TCP_METRICS(8)
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NAME

6       ip-tcp_metrics - management for TCP Metrics
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SYNOPSIS

9       ip [ OPTIONS ] tcp_metrics { COMMAND | help }
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12       ip tcp_metrics { show | flush } SELECTOR
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14       ip tcp_metrics delete [ address ] ADDRESS
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16       SELECTOR := [ [ address ] PREFIX ]
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DESCRIPTION

20       ip tcp_metrics is used to manipulate entries in the kernel that keep
21       TCP information for IPv4 and IPv6 destinations. The entries are created
22       when TCP sockets want to share information for destinations and are
23       stored in a cache keyed by the destination address. The saved informa‐
24       tion may include values for metrics (initially obtained from routes),
25       recent TSVAL for TIME-WAIT recycling purposes, state for the Fast Open
26       feature, etc.  For performance reasons the cache can not grow above
27       configured limit and the older entries are replaced with fresh informa‐
28       tion, sometimes reclaimed and used for new destinations. The kernel
29       never removes entries, they can be flushed only with this tool.
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32   ip tcp_metrics show - show cached entries
33       address PREFIX (default)
34              IPv4/IPv6 prefix or address. If no prefix is provided all
35              entries are shown.
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38       The output may contain the following information:
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40       age <S.MMM>sec - time after the entry was created, reset or updated
41       with metrics from sockets. The entry is reset and refreshed on use with
42       metrics from route if the metrics are not updated in last hour. Not all
43       cached values reset the age on update.
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45       cwnd <N> - CWND metric value
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47       fo_cookie <HEX-STRING> - Cookie value received in SYN-ACK to be used by
48       Fast Open for next SYNs
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50       fo_mss <N> - MSS value received in SYN-ACK to be used by Fast Open for
51       next SYNs
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53       fo_syn_drops <N>/<S.MMM>sec ago - Number of drops of initial outgoing
54       Fast Open SYNs with data detected by monitoring the received SYN-ACK
55       after SYN retransmission.  The seconds show the time after last SYN
56       drop and together with the drop count can be used to disable Fast Open
57       for some time.
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59       reordering <N> - Reordering metric value
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61       rtt <N>us - RTT metric value
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63       rttvar <N>us - RTTVAR metric value
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65       ssthresh <SSTHRESH> - SSTHRESH metric value
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67       tw_ts <TSVAL>/<SEC>sec ago - recent TSVAL and the seconds after saving
68       it into TIME-WAIT socket
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71   ip tcp_metrics delete - delete single entry
72       address ADDRESS (default)
73              IPv4/IPv6 address. The address is a required argument.
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76   ip tcp_metrics flush - flush entries
77       This command flushes the entries selected by some criteria.
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80       This command has the same arguments as show.
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EXAMPLES

84       ip tcp_metrics show address 192.168.0.0/24
85           Shows the entries for destinations from subnet
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87       ip tcp_metrics show 192.168.0.0/24
88           The same but address keyword is optional
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90       ip tcp_metrics
91           Show all is the default action
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93       ip tcp_metrics delete 192.168.0.1
94           Removes the entry for 192.168.0.1 from cache.
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96       ip tcp_metrics flush 192.168.0.0/24
97           Removes entries for destinations from subnet
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99       ip tcp_metrics flush all
100           Removes all entries from cache
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102       ip -6 tcp_metrics flush all
103           Removes all IPv6 entries from cache keeping the IPv4 entries.
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SEE ALSO

107       ip(8)
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AUTHOR

111       Original Manpage by Julian Anastasov <ja@ssi.bg>
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115iproute2                          23 Aug 2012                IP-TCP_METRICS(8)
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