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Tugas Komunikasi Data 8

Kelompok 7

Khusnil Mujib (21060113130136)

Menpo Vaso!egama "anjaitan (210601131#0122)

8$7$ %&e'ises

1. Consider a wide area network in which two hosts, A and B, are connected through a 100

km communication link with the data speed of 1 Gb/s. Host A wants to transfer the

content of a C!"#$ with %00 &b of music data while host B reser'es portions of its

10 parallel buffers, each with the capacit( of 10,000 bits. )se *igure +. and assume

that host A sends a - segment, where - %,000 and $-- %,000 and that host B

sends - 2,000 and $-- 1,000. -ketch the se3uence of segment e4change,

starting with host A sending data at time t 0. Assume host B sends AC& e'er( fi'e

frames.

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ari gambar diatas merupakan ilustrasi. )kuran tiap paket 1000 b(te karena

merupakan $-- dari Host BHost A6 $-- %000, - %000, )kuran file %00 &b %7 &B

Host B6 $-- 1000, - 2000, )kuran 8aket 100 &b %7 &Bimana data per paket 9:0 b(te

;iga tahapan dalam transfer file 6 8embentukan &oneksi, ;ransfer -egment, dan

8emutusan &oneksi

%. Consider that host 1 transfers a large file of si<e f to host % with $-- %,000 b(tes

o'er a 100 $b/s link.a. &nowing that the ;C8 se3uence number field has 2 b(tes, find f such that ;C8

se3uence numbers are not e4hausted.

 b. *ind the time it takes to transmit f. nclude the link, network, and transport headers

attached to each segment.

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a. *ield se3uence ;C8 termasuk 2 B % b. sehingga

• 5umlah b(te maksimu (ang dapat diidentifikasi di koneksi %%.

• &ita menggunakan 1 se3uence untuk pembentukan koneksi, se3=i>, dan satu

se3uence untuk pemutusan koneksi, se3=k>. ;iap b(te data diidentifikasi dengan

angka se3uence (ang khas, sehingga ?umlah maksimum b(te data (ang dapat

diidentifikasi untuk sebuah koneksi dan (ang dapat kita transfer 

¿ f =232−2=4.294 .967.294B

 b. )kuran total tiap segment %000 B. an ?uga tiap segment mempun(ai header 6 %0

B @ink %0 B 8 %0 B ;C8 :0 B, sehingga6

• )kuran maksimum data tiap segment %000 B ! :0 B 1920 B

• 5umlah maksimum segment (ang dapat dihasilkan dalam sebuah koneksi

¿ 4.294.976.294B

1940B  ≈2.213901

• )kuran total dari semua header segment 2.213 .901× (60B )=132.834 .060B

• )kuran total untuk semua header segment dan data segment

¿4.294.967.294 B+132.834.060B=4.427.801.354 B• aktu total (ang diperlukan untuk mentransfer semua segment

¿ 4.427.801.354 B ×8b /B

100×106

bit per sekon=354.21 s ≈5.9menit 

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. Assume that a ;C8 connection is established. *ind the number of round!trip times the

connection takes before it can transmit n segments, usinga. -low!start congestion control

 b. Additi'e increase congestion control

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a. &ontrol kongesti slow!start&arena ?umlah paket (ang ditransmisikan digandakan tiap waktu, maka ?umlah

 per?alanan bolak!balik untuk mencapai nadalah log2n−1

 b. &ontrol kongesti Additi'e!ncrease

&arena ?umlah paket (ang ditransmisikan meningkat se?umlah satu tiap waktu,

maka ?umlah per?alanan bolak!balik untuk mencapai nadalahn−1

2. e want to understand the fairness inde4 of resource allocations. -uppose that a

congestion!control scheme can face fi'e possible flows with the following throughput

rates6 B1 1 Gb/s, B% 1 Gb/s, B 1 Gb/s, B2 1.% Gb/s, and B7 1: Gb/s.a. Calculate the fairness inde4 for this scheme for B1, B%, and B.

 b. hat useful information does the result of part =a> pro'ide

c. ow, consider all fi'e flows, and calculate the fairness inde4 for this scheme.d. hat would the result of part =c> mean to each flow

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a. σ =(∑i=1

n

f i)2

n∑i=1

n

f i2

¿ ( f 1+ f 2+ f 3 )2

3 ∙ f 12+ f 2

2+f 32

¿  3

2

3 ∙3

=9

9

=1

 b. Best fairness

c.(1+1+1+1,2+16 )2

3 (12+12+12+1,22+162)= 408,04

781,32=0,522

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d. "esource!allocation for n7 is not so fair 

7. Assume that a ;C8 connection is established o'er a moderatel( congested link. ;he

connection loses one packet e'er( fi'e segments =packets>.

a. Can the connection sur'i'e at the beginning with the linear portion of congestion

a'oidance

 b. Assume that the sender knows that the congestion remains in the network for a long

time. ould it be possible for the sender to ha'e a window si<e greater than fi'e

segments h(

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a. &oneksi dapat bertahan diawal, namun tidak akan lama karena terdapat antrian pada router sehingga ";; setiap paket akan bertambah. $aslah akan bertambah

saat ada paket gagal (ang meminta transmisi ulang dengan paket (ang baru b. ;idak mungkin, karena bila menggunakan aloritma ";; dan window si<e dengan

hasil komputasi =D ! Do>=r ! r o> bernilai nilai negatif atau 0, maka window si<e han(a

dapat bertambah sebesar 1 paket sa?a.

:. A ;C8 connection is established o'er a 1.% Gb/s link with a round!trip time of . ms.

;o transmit a file of si<e % $B, we start sending it, using 1 & packets.

a. How long does the transmission take if an additi'e increase, multiplicati'e decreasecontrol with a window si<e of Dg 700 & is used

 b. "epeat part =a>, using slow!start control.

c. *ind the throughput of this file transfer.

d. *ind the bandwidth utili<ation for this transfer.

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l=1,2Gb /s

";; , ms

)kuran file f % $B

)kuran paket 1 &B

-ehingga ?umlah total paket (ang diperlukan untuk dikirim ¿2 MB

1 KB =2000

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a. engan protocol additi'e!increase/ multiplicati'e decrease, ukuran window

meningkat se?umlah satu sampai kongesti/macet ketika ukuran window dibagi %.

-ehingga, ukuran window dimulai saat w g=1 KB  berubah hingga nilain(a6

wg=1 KB ,2 KB ,3 KB ,4 KB ,… n KB

-ehingga 6   1+2+3+…+n=2000

)ntuk mendapatkan n6

n(n+1)2

=2000

&ita dapatkan n=62.74≈63

&arena, ukuran window kongesti 700 &B tidak tercapai, maka tidak ada

multiplicati'e decrease. 5adi6

  waktutotal=63×3,3ms=207ms

)kuran window akan mencapai total dari

500×RTT =500×3,3ms=1,65 suntuk meapai500 KB

 b. engan protocol slow!start, ukuran window digandakan setiap waktu sampai

mencapai kongesti/macet. )kuran window dimulai dari wg 1 &B dan berubah

sesuai dengan waktun(a6wg=1 KB ,2 KB ,4 KB,8 KB ,…,sampai1024 KB

-ehingga, kita harus mencapai 11 per?alanan bolak!balik untuk mengirim file61+2+4+8+16+32+64+128+256+512+1024=2047

aktu total ¿11×RTT =11×3,3ms=36,3ms

)kuran windown(a men?adi 104 lebih besar.

c. engan protocol additi'e!increase/ multiplicati'e decrease, membutuhkan : ";;

untuk mengirim file % $B, sehingga!=63×3,3ms ≈208ms

r= f 

!=

 2 MB

208ms=76.9 Mbps

d. engan protocol additi'e!increase/ multiplicati'e decrease

 "u= r

B=76.9 Mbps

12Gbps  =64×10

−3

E. Consider that an established ;C8 connection has a round!trip time of appro4imatel( 0.7

second and forms a window si<e of Dg: &. ;he sending source transmits segments

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=packets> e'er( 70 ms, and the destination acknowledges each segment e'er( 70 ms.

 ow assume that a congestion state de'elops in this connection such that the

destination does not recei'e a segment. ;his loss of segment is detected b( the fast!

retransmit method at the fourth receipt of duplicate AC&.a. *ind the amount of time the sending source has lost if the source uses the arri'al of 

duplicate AC&s as a sign for mo'ing the window forward one segment.

 b. "epeat part =a>, this time under a condition that the sending source waits to recei'e

the AC& of the retransmitted packet before mo'ing the window forward one

segment.

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aktu per?alanan bolak!balik   ¿0.5 s

8aket dikirim tiap 70 ms

&ita asumsikan segment 8!11 lost. AC& pertama, AC&!10 diterima ketika 8!%1 akan

dikirim. ;idak ada AC& (ang diterima sebelum 8!%% karena 8!11 lost. &ita menerima

AC&!10 (ang keempat setelah 8!%2 dikirim. -egment loss dideteksi. ang dikirim 8!11

 bukan 8!%7.

a. 8ada kondisi ini, 8!11 dikirim dan setelah 70 ms, 8!%7 dikirim dan dan seperti

itu terus perputarann(a. -ehingga kita han(a kehilangan 70 ms. -eperti gambar 

diatas.

 b. 8ada kondisi ini, penerima menunggu AC& untuk kembali mengirim 8!11.

-ehingga harus menunggu per?alanan bolak!balik secara lengkap. -ehingga

waktu (ang hilang adalah 0,7 s.

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