Tips for TCP/IP monitoring and tuning to make your network sing

Q: Which of the TCP protocol counters are worth watching? How can I
tell if there is a problem, and what should I tune?

--Fin_wait Freda

A: TCP/IP is simple in concept, but the reality of making it work reliably
in a wide range of conditions adds a lot more complexity. There are a
large number of protocol counters that can be viewed with netstat
-s, but only a small number of them are of general interest.
There is another set of values that can be obtained and set using the
ndd command.

The netstat -s command lists several protocols, but I just
show the TCP data that is reported by Solaris 2.5.1.

TCP     tcpRtoAlgorithm     =     4     tcpRtoMin           =   200
        tcpRtoMax           = 60000     tcpMaxConn          =    -1
        tcpActiveOpens      =  3283     tcpPassiveOpens     =   234
        tcpAttemptFails     =     0     tcpEstabResets      =   100
        tcpCurrEstab        =     6     tcpOutSegs          = 80370
        tcpOutDataSegs      = 57395     tcpOutDataBytes     =9854298
        tcpRetransSegs      =  4826     tcpRetransBytes     =644526
        tcpOutAck           = 23486     tcpOutAckDelayed    =  5081
        tcpOutUrg           =    34     tcpOutWinUpdate     =     3
        tcpOutWinProbe      =     5     tcpOutControl       =  7066
        tcpOutRsts          =   132     tcpOutFastRetrans   =   196
        tcpInSegs           = 96006
        tcpInAckSegs        = 52302     tcpInAckBytes       =9856462
        tcpInDupAck         =  9887     tcpInAckUnsent      =     0
        tcpInInorderSegs    = 63348     tcpInInorderBytes   =20318851
        tcpInUnorderSegs    =     0     tcpInUnorderBytes   =     0
        tcpInDupSegs        =     0     tcpInDupBytes       =     0
        tcpInPartDupSegs    =     0     tcpInPartDupBytes   =     0
        tcpInPastWinSegs    =     0     tcpInPastWinBytes   =     0
        tcpInWinProbe       =     6     tcpInWinUpdate      =     4
        tcpInClosed         =    15     tcpRttNoUpdate      =  1286
        tcpRttUpdate        = 20744     tcpTimRetrans       =  1514
        tcpTimRetransDrop   =     0     tcpTimKeepalive     =   168
        tcpTimKeepaliveProbe=     0     tcpTimKeepaliveDrop =     0
        tcpListenDrop       =     0

To make sense of this, and to pick out the data of interest, I'll
start with a simplified description of TCP, and relate this to the data
reported by netstat -s.

TCP is a reliable, connection-oriented protocol.

Sign up for ITworld's Daily newsletter
Follow ITworld on Twitter @IT_world

• Email
• Print
• Share
  • Slashdot
  • Digg
  • Stumble
  • Reddit
  • Newsvine