TCP-Sequence/Selective-ACK/Cumulative-ACK
SEQ or relative seq number:
======================
10bytes of data
seq=10----ack-1-------i have sent you 10bytes of data till now--->
<-----------------------seq=1 ack=11 (1byte of data)
200 bytes of data
seq=200+10=210 ack=2-----------i have sent you 210 bytes of data till now--->
<-----------------------seq=1+1=2 ack=211(1byte of data)
seq=10----ack-1-------i have sent you 10bytes of data till now--->
<-----------------------seq=1 ack=11 (1byte of data)
200 bytes of data
seq=200+10=210 ack=2-----------i have sent you 210 bytes of data till now--->
<-----------------------seq=1+1=2 ack=211(1byte of data)
SACK: (if segment is missing)
====
without SACK
5 segments
------------------------------------1------------->
------------------------------------2------------->
----------------------------------3***
--------------------------------4------------------>
-------------------------------5-------------------->
<--------------------------ACK1 + 2 + 4--------------------
----------------------------------3--------------->
--------------------------------4------------------>
-------------------------------5-------------------->
<--------------------------ACK 3 + 4 + 5--------------------
with SACK:
------------------------------------1------------->
------------------------------------2------------->
----------------------------------3***
--------------------------------4------------------>
-------------------------------5-------------------->
<--------------------------ACK1 + 2 + 4--------------------
----------------------------------3---------------> fast-retransmit
<--------------------------ACK 3 + 4 + 5--------------------
IF SACK is OFF, then server will have to retransmit the packet from the point of packet lost.
IF SACK is ON, then server will have to retransmit only the lost packet lost.
CACK: cumulative ACK (if ACK is missing)
================
Sending one ack for n number of segments/packets at a time
( cumulative =increasing or increased in quantity, degree, or force by successive additions)
WITH CACK:-
A------------------ seq=1-------------->B
A------------------ seq=2-------------->B
......
......
A------------------ seq=10-------------->B
A<----------------------------CACK=11---B
************--CACK=11----------------
again it will send all data
A------------------ seq=1 to 10-------------->B
WITHOUT_CACK:-
A------------------ seq=1-------------->B
A------------------ seq=2-------------->B
.
.
A------------------ seq=10-------------->B
A<----------------------------ACK=1---B
A<----------------------------ACK=2---B
A<----------------------------ACK=3---B
......
.....
A<----------------------------ACK=10---B
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