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Iluvnetwork
Beginner

Sequence & ACK Number Question!

My understanding is

If PC A sends a packet (ACK = 80, Sequence Number = 1450, Payload = 1460), PC B will send an ACK Message (ACK = 2910, Sequence Number = RANDOM).

If I am misunderstanding, please let me know.

 

1 REPLY 1
Peter Paluch
Hall of Fame Cisco Employee

Hi,

If PC A sends a packet (ACK = 80, Sequence Number = 1450, Payload = 1460), PC B will send an ACK Message (ACK = 2910, Sequence Number = RANDOM).

The SeqNo from PC B much depends on whether PC B is also sending data to PC A because that would mean that there is some data in flight already sent by PC B but not yet seen by PC A. For simplicity purposes, if for some time in the past, PC B was silent, then PC B will send a TCP segment with AckNo=1450+1460=2910, SeqNo=80.

Best regards,
Peter