The TCP window seems to get smaller if the connection stays up for a long time. I closed the connection and started it again, so you can see the connection start. The receive and send socket buffer was set to 8192 on both sides. The other side is running FreeBSD. I probably shouldn't set that and keep the default value though. During the connection start, we seem to announce window of 7248, but after some time it seems to drop to 1772 instead, while the other end stays at 8192 bytes. Why does this happen? Is it normal? Is there some way to make it bigger? Here is a part of the tcpdump: 02:50:31.296551 3ffe:80c0:220::b.2661 > 3ffe:80c0:200:2:250:b7ff:fe13:be.194: SWE [tcp sum ok] 1728100735:1728100735(0) win 5680 <mss 1420,sackOK,timestamp 549723502 0,nop,wscale 0> (len 40, hlim 64) 02:50:31.422685 3ffe:80c0:200:2:250:b7ff:fe13:be.194 > 3ffe:80c0:220::b.2661: S [tcp sum ok] 2460983586:2460983586(0) ack 1728100736 win 8456 <mss 1440,nop,wscale 0,nop,nop,timestamp 1254163271 549723502> [flowlabel 0xaf77f] (len 40, hlim 62) 02:50:31.422727 3ffe:80c0:220::b.2661 > 3ffe:80c0:200:2:250:b7ff:fe13:be.194: . [tcp sum ok] 1:1(0) ack 1 win 5680 <nop,nop,timestamp 549723515 1254163271> (len 32, hlim 64) 02:50:31.509676 3ffe:80c0:220::b.2661 > 3ffe:80c0:200:2:250:b7ff:fe13:be.194: P [tcp sum ok] 1:100(99) ack 1 win 5680 <nop,nop,timestamp 549723524 1254163271> (len 131, hlim 64) 02:50:31.728099 3ffe:80c0:200:2:250:b7ff:fe13:be.194 > 3ffe:80c0:220::b.2661: . [tcp sum ok] 1:1(0) ack 100 win 8357 <nop,nop,timestamp 1254163302 549723524> [flowlabel 0xaf77f] (len 32, hlim 62) 02:50:35.418518 3ffe:80c0:200:2:250:b7ff:fe13:be.194 > 3ffe:80c0:220::b.2661: . [tcp sum ok] 1:1209(1208) ack 100 win 8357 <nop,nop,timestamp 1254163670 549723524> [flowlabel 0xaf77f] (len 1240, hlim 62) 02:50:35.418592 3ffe:80c0:220::b.2661 > 3ffe:80c0:200:2:250:b7ff:fe13:be.194: . [tcp sum ok] 100:100(0) ack 1209 win 7248 <nop,nop,timestamp 549723915 1254163670> (len 32, hlim 64) ... 04:25:06.870113 3ffe:80c0:200:2:250:b7ff:fe13:be.194 > 3ffe:80c0:220::b.2661: P [tcp sum ok] 7787:8117(330) ack 20 win 8192 <nop,nop,timestamp 1254730880 550291035> [flowlabel 0xaf77f] (len 362, hlim 62) 04:25:06.870306 3ffe:80c0:220::b.2661 > 3ffe:80c0:200:2:250:b7ff:fe13:be.194: . [tcp sum ok] 20:20(0) ack 8117 win 1772 <nop,nop,timestamp 550291047 1254730880> (len 32, hlim 64) 04:25:06.992062 3ffe:80c0:200:2:250:b7ff:fe13:be.194 > 3ffe:80c0:220::b.2661: P [tcp sum ok] 8117:8258(141) ack 20 win 8192 <nop,nop,timestamp 1254730892 550291047> [flowlabel 0xaf77f] (len 173, hlim 62) 04:25:06.992309 3ffe:80c0:220::b.2661 > 3ffe:80c0:200:2:250:b7ff:fe13:be.194: . [tcp sum ok] 20:20(0) ack 8258 win 1772 <nop,nop,timestamp 550291059 1254730892> (len 32, hlim 64) Kurt - : send the line "unsubscribe linux-net" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
