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July 17, 2004
Wrapped Sequence
Have you thought about sequence wrapped (cycled) in TCP connection yet?
In fact it can threaten TCP reliablity if we have high transfer rate , the sequence numbers may eventually be reused in the same connection at the short time and it causes duplicate sequence numbers.
we need a life time for segment which it should be shorter than the time it takes to cycle the sequence space.The maximum segment lifetime (MSL) defined 2^31 / B > MSL (secs) , B is bandwidth byte per second for prevent wrapped sequence .
you can see the following table which explains MSL for some important bandwidth :
Network B*8 B Twrap
bits/sec bytes/sec secs
_______ _______ ______ ______
ARPANET 56kbps 7KBps 3*10**5 (~3.6 days)
DS1 1.5Mbps 190KBps 10**4 (~3 hours)
Ethernet 10Mbps 1.25MBps 1700 (~30 mins)
DS3 45Mbps 5.6MBps 380
FDDI 100Mbps 12.5MBps 170
Gigabit 1Gbps 125MBps 17
Posted by Mehrdad at July 17, 2004 10:32 PM