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TCP retransmission and dup acks [message #11974]

Fri, 13 April 2007 12:08

hvdkamer
Messages: 40
Registered: July 2006

Member

While investigating a problem with tcpdump I saw a lot of retransmissions and duplicate acks:

No.     Time        Source                Destination           Protocol Info
      8 0.864699    192.168.13.41         192.168.13.146        TCP      52339 > www [SYN] Seq=0 Ack=0 Win=5840 Len=0 MSS=1460 TSV=3815361250 TSER=0 WS=7
      9 0.864719    192.168.13.41         192.168.13.146        TCP      52339 > www [SYN] Seq=0 Ack=0 Win=747520 Len=0 MSS=1460 TSV=3815361250 TSER=0 WS=7
     10 0.864752    192.168.13.146        192.168.13.41         TCP      www > 52339 [SYN, ACK] Seq=0 Ack=1 Win=5792 Len=0 MSS=1460 TSV=3815361250 TSER=3815361250 WS=7
     11 0.864759    192.168.13.146        192.168.13.41         TCP      www > 52339 [SYN, ACK] Seq=0 Ack=1 Win=741376 Len=0 MSS=1460 TSV=3815361250 TSER=3815361250 WS=7
     12 0.864775    192.168.13.41         192.168.13.146        TCP      52339 > www [ACK] Seq=1 Ack=1 Win=5888 Len=0 TSV=3815361250 TSER=3815361250
     13 0.864779    192.168.13.41         192.168.13.146        TCP      [TCP Dup ACK 12#1] 52339 > www [ACK] Seq=1 Ack=1 Win=5888 Len=0 TSV=3815361250 TSER=3815361250

Later on this leads to retransmissions. Is this normal? Or must I be worried Smile