How get the value of TCP connection establishment timing,retry timing in ubuntu 14

Question

how i get the value of TCP connection establishment timing ,retry timing for any TCP connection and also Quality of services parameters in Ubuntu .

Answer 1

Try this to display the values currently used for TCP communication:

sudo sysctl -ae | fgrep -i "net.ipv4.tcp"

Some Variables are documented in this man page:

man 7 tcp

Quick start:

man 7 tcp | awk '/proc interfaces/,/Socket options/ {print prev; prev=$0}'

Quality of services parameters, can be displayed with:

netstat -s 
/sbin/ifconfig

----

tcp_retries1 (integer; default: 3; since Linux 2.2)
  The number of times TCP will attempt to retransmit a packet on an established
  connection normally, without the extra effort of getting the network layers
  involved. Once we exceed this number of retransmits, we first have the network
  layer update the route if possible before each new retransmit. The default is
  the RFC specified minimum of 3. 

tcp_retries2 (integer; default: 15; since Linux 2.2)
  The maximum number of times a TCP packet is retransmitted in established
  state before giving up. The default value is 15, which corresponds to a duration
  of approximately between 13 to 30 minutes, depending on the retransmission
  timeout. The RFC 1122 specified minimum limit of 100 seconds is typically deemed
  too short. 

If you consider default values tcp_retries1=3 and tcp_retries2=15:

• in case of failure to transmit a packet, 3 (tcp_retries1) retransmitions will be attempted, without extra effort.
• after 3 attempts, the network layer is involved to update the route
• this is done up to 15 attempts maximum (tcp_retries2), then it stops.