Difference between tcp recv buffer and tcp receive window size?
- by pradeepchhetri
The command shows the tcp receive buffer size in bytes.
$ cat /proc/sys/net/ipv4/tcp_rmem
4096 87380 4001344
where the three values signifies the min, default and max values respectively.
Then I tried to find the tcp window size using tcpdump command.
$ sudo tcpdump -n -i eth0 'tcp[tcpflags] & (tcp-syn|tcp-ack) == tcp-syn and port 80 and host google.com'
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 65535 bytes
16:15:41.465037 IP 172.16.31.141.51614 > 74.125.236.73.80: Flags [S], seq 3661804272, win 14600, options [mss 1460,sackOK,TS val 4452053 ecr 0,nop,wscale 6], length 0
I got the window size to be 14600 which is 10 times the size of MSS.
Can anyone please tell me the relationship between the two.