Am 15.05.2015 um 18:17 schrieb Gordon Messmer <gordon.messmer at gmail.com>: > On 05/15/2015 09:02 AM, Leon Fauster wrote: >> >> I have a public peer system (yy.yy.yy.yy) that is reachable >> via my home uplink (xx.xx.xx.xxx). >> >> 15:59:30.244199 IP xx.xx.xx.xxx.42958 > yy.yy.yy.yy.https: tcp 0 >> 15:59:30.281931 IP yy.yy.yy.yy.https > xx.xx.xx.xxx.42958: tcp 0 >> 15:59:30.281945 IP xx.xx.xx.xxx.42958 > yy.yy.yy.yy.https: tcp 0 >> 15:59:30.305020 IP xx.xx.xx.xxx.42958 > yy.yy.yy.yy.https: tcp 105 >> 15:59:30.344004 IP yy.yy.yy.yy.https > xx.xx.xx.xxx.42958: tcp 1412 >> 15:59:30.344013 IP xx.xx.xx.xxx.42958 > yy.yy.yy.yy.https: tcp 0 >> 15:59:30.344016 IP yy.yy.yy.yy.https > xx.xx.xx.xxx.42958: tcp 23 >> >> At the office we have a EL5 based router that can not reach the >> mentioned system. It does not give any hint about the problem. >> >> 15:57:51.751591 IP o.ff.i.ce.50902 > yy.yy.yy.yy.https: tcp 0 >> 15:57:54.750834 IP o.ff.i.ce.50902 > yy.yy.yy.yy.https: tcp 0 >> 15:58:00.749351 IP o.ff.i.ce.50902 > yy.yy.yy.yy.https: tcp 0 >> 15:58:12.746408 IP o.ff.i.ce.50902 > yy.yy.yy.yy.https: tcp 0 >> 15:58:36.740454 IP o.ff.i.ce.50902 > yy.yy.yy.yy.https: tcp 0 >> 15:59:24.728605 IP o.ff.i.ce.50902 > yy.yy.yy.yy.https: tcp 0 >> >> I tried to connect with a removed ecn bit [1] >> >> [1] https://en.wikipedia.org/wiki/Explicit_Congestion_Notification >> >> but this was not the solution. >> >> Any ideas? > > That's not much information to go on. Can you run > tcpdump on the "public peer system"? Does it receive > the SYN packets from your office? Well, the destination is not in my realm (different provider). Before contacting them I want to be sure that my system is not causing this. So far i just see a "tcp retransmission" while trying to establish a https connection (captured on our router): office -> destination: TCP 66 54487→443 [SYN] Seq=0 Win=5840 Len=0 MSS=1460 SACK_PERM=1 WS=8 office -> destination: TCP 66 [TCP Retransmission] 54487→443 [SYN] Seq=0 Win=5840 Len=0 MSS=1460 SACK_PERM=1 WS=8 from my home and office, I can see via traceroute that for the destination the entry hop is the same. So, the destination is not responding with SYN,ACK when the connection passes our router. But as I said it is reachable from my home, and this is confusing. Thanks, LF