ACN Slide 8 - Lecture notes 8 PDF

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Advance Computer Network slides for lecture 8...

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TCP Reno: Problem CWND = 1 CWND = 2

CWND = 4

CWND = 8

initial_ ssthresh = 20

0 1 2

7 8 . . 15 16 17 .26 27 28

A N E X A in . S c ) a . i i H n n S a l i a E Pil its-p R A S ad.b P . T b r I a r B D ( yde h 3 4 5 6

7 8 9 10 11 12 13 14

.

CWND = 15

CWND = a

. .

CWND = b

T=7,CWND =c

@. a n . e x psa

CWND = d

. .

a = 15 b = 15 c = 10 d = 19 e = 32

Duplicate ACKs 14

Fast Retransmit Fast Recovery

e BITS Pilani, Hyderabad Campus

Ack rcvd from packet #

Old Cwnd

Total number of unack packets

New Cwnd

Packet sent #

Ack types (new/d upack)

State

ssthr

0

1

0

2

1,2

new

Slow S

20

1

2

1

3

3,4

new

Slow S

20

2

3

2

4

5,6

new

Slow S

20

3

4

3

5

7,8

new

Slow S

20

4

5

4

6

9,10

new

Slow S

20

5

6

5

7

11,12

new

Slow S

20

6

7

6

8

13,14

new

Slow S

20

7

8

7

9

15,16

new

Slow S

20

8

9

8

10

17,18

new

Slow S

20

9

10

9

11

19,20

new

Slow S

20

10

11

10

12

21,22

new

Slow S

20

11

12

11

13

23,24

new

Slow S

20

12

13

12

14

25,26

new

Slow S

20

13

14

13

15

27,28

new

Slow S

20

A in . c i.a n ila

BITS Pilani, Hyderabad Campus

Ack rcvd from packet #

Old Cwnd

Total number of unack packets

New Cwnd

Packet sent #

Ack types (new/d upack)

State

ssthr

15

15

15

15

-

dup

Slow S

20

16

15

15

15

-

dup

Slow S

20

17

15

15

10

14

dup

Slow S

7

18

10

15

11

-

dup

Fast R

7

19

11

15

12

-

dup

Fast R

7

20

12

15

13

-

dup

Fast R

7

21

13

15

14

-

dup

Fast R

7

22

14

15

15

-

dup

Fast R

7

23

15

15

16

29

dup

Fast R

7

24

16

16

17

30

dup

Fast R

7

25

17

17

18

31

dup

Fast R

7

27

18

18

19

32

dup

Fast R

7

14

19

19

7

-

new

CA

7

A in . c i.a n ila

BITS Pilani, Hyderabad Campus

Lab Project • Groups: 3-4 students per group •

•

A N E Send group details to [email protected] A names, ids and pilani.ac.in. Please include the in email of . S c ) all the group members. H .a i i n S ilan -pila E R s t P i A Submit groupPdetails (number .bof members, Name, S d a 17:00). . T b r I ID) by 1 December (Tuesday, a D (B yder h st

@ • 5 marks penalty for na late submission of group details e x a ps

BITS Pilani, Hyderabad Campus

TCP Reno: Issues (Multiple Losses in a Window) CWND = 1 CWND = 2

CWND = 4

CWND = 5

CWND = 5 CWND = 5

0 ACK(1) 1 ACK(2) 2 ACK(3)

A N E X A ) c.in S .a i i H n S ilan -pila E R P .bits A S P d a . T Dr (BI yderab h dupACKs

3 ACK(4) 4 5 6 7 ACK(4) 8 ACK(4)

Wait for the TimeOut !!

a@ n e x a ps

TimeOut for 4 BITS Pilani, Hyderabad Campus

TCP Reno: Issues (Loss during Fast Recovery) CWND = 1 CWND = 2

CWND = 4

CWND = 5 CWND = 6 CWND = 6 CWND = 6 CWND = 6 CWND = 7 CWND = 8

CWND = 9 CWND = 10

0 ACK(1) 1 ACK(2) 2 ACK(3)

A N E X A ) c.in S .a i i H n S ilan -pila E R P .bits A S P d a . T Dr (BI yderab h 3 ACK(4) 4 ACK(5) 5 6 ACK(5) 7 ACK(5) 8 ACK(5) 9 ACK(5) 10ACK(5)

5 Fast Retransmit 11 ACK(5) 12 ACK(5) Fast Recovery ACK(5) 13 14 ACK(5)

a@ n e x a ps

and so wait until the time out !! BITS Pilani, Hyderabad Campus

TCP Reno: Issues (Loss during Fast Recovery) CWND = 1

0 1 2

ACK(1)

A N E X A ) c.in S .a i i H n S ilan -pila E R P .bits A S P d a . T Dr (BI yderab h CWND = 2

CWND = 4

CWND = 5 CWND = 6

SSTHRESH = 3

Fast Retransmit Fast Recovery

CWND = 6 CWND = 6 CWND = 6 CWND = 7

@ a n Exit Fast Recovery CWND = SSTHRESHe= 3 x a s p

ACK(2) ACK(3)

3 4 5 6 7 8 9 10

ACK(4) ACK(5)

5 11

ACK(6)

ACK(5) ACK(5) ACK(5) ACK(5)

ACK(6)

Congestion Avoidance

and so wait until the time out !! BITS Pilani, Hyderabad Campus

Multiple Losses in a Window • 2 Losses: Reno will occasionally timeout • • •

A N E 3 Losses: Reno will usually timeout X A ) c.in S i.a 4 losses: GuaranteedS toHtimeout n !! i n la i a E l p i R st P i A b .window, S P d With three ore more losses in a Tahoe typically a . T b r I out performs D Reno(B!! ydera h a@ n e x a ps

BITS Pilani, Hyderabad Campus

A N E X A ) c.in S .a i i H n S ilan -pila E R End ofPLecture s t i A .b S P d a . T b r I a D (B yder h a@ n e x a ps

BITS Pilani, Hyderabad Campus...