Sequence Numbers 32 Bits, Unsigned> for bytes not packets! Circular Comparison b Max 0 Max 0 b< a a< b Why So Big? For sliding window, must have Sequence Space>Sending Window +Receiving Window Also, want to guard against stray packets With IP, packets have maximum lifetime of 120s Sequence number would wrap around in this time at 286MB/s=- 2. 3Gbit/s ecture 17: TCP Congestion Control5 Lecture 17: TCP & Congestion Control Sequence Numbers • 32 Bits, Unsigned → for bytes not packets! • Circular Comparison • Why So Big? • For sliding window, must have • |Sequence Space| > |Sending Window| + |Receiving Window| • No problem • Also, want to guard against stray packets • With IP, packets have maximum lifetime of 120s • Sequence number would wrap around in this time at 286MB/s =~ 2.3Gbit/s (hmm!) Max 0 a b a < b Max 0 b a b < a