MMT- 04-2.pdf

Trng i Hc Bch Khoa Tp.HCM Khoa Khoa Hc v K Thut My Tnh

ThS. NGUYN CAO T

E-mail:[email protected]

Bi ging

Mng my tnh

Trng i Hc Bch Khoa Tp.HCM

Khoa Khoa Hc v K Thut My Tnh

2011

MNG MY TNH CN BN

Bi ging 3 - Chng 4: Tng Mng

2

Bi ging 9: Tng Mng(t.t)

Tham kho:

Chng 4: Computer Networking A top-down approach

Kurose & Ross, 5th ed., Addison Wesley, 2010.



2011

MNG MY TNH CN BN


3

Chng 4: Tng Mng

4.1 Gii thiu

4.2 Bn trong b nh tuyn l g?

4.3 IP: Internet Protocol

nh dng gi tin

nh a ch IPv4

ICMP

IPv6

4.4 Cc gii thut nh tuyn Trng thi lin kt

Vc-t Khong cch

nh tuyn phn cp

4.5 nh tuyn trong Internet

RIP

OSPF

BGP



2011

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4

ICMP: Giao thc thng ip kim sot Internet

s dng bi my tnh v bt lin lc thng tin tng-mng

bo co li: my, mng, cng, giao thc khng lin lc c

yu cu/phn hi gi echo (s dng bi ping)

nm tng trn IP:

th/ip ICMP c mang trong gi tin IP

thng ip ICMP: loi, m cng vi 8 byte u ca gi tin IP m gy ra li

Loi M Ch gii 0 0 phn hi echo (ping) 3 0 mng ch ko lin lc c 3 1 my ch ko lin lc c 3 2 g/thc ch ko lin lc c 3 3 cng ch ko lin lc c 3 6 mng ch khng bit 3 7 my ch khng bit 4 0 gim tc ngun (kstn khng dng) 8 0 truy vn echo (ping) 9 0 qung b tuyn ng 10 0 tm tuyn ng 11 0 TTL ht hn 12 0 mo u IP b li



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5

Traceroute v ICMP

Ngun gi mt lot khc UDP cho ch

khc u tin c TTL =1

khc th 2 c TTL=2, v.v.

s cng khng c nh

Khi gi tin th n n bt n:

BT loi b gi tin

V gi li ngun mt thng ip ICMP (loi 11, m 0)

Thng ip bao gm c tn v a ch IP ca bt

Khi thng ip ICMP ti, ngun s tnh RTT

Traceroute thc hin vic ny 3 ln

iu kin ngng li

Khc UDP n c my ch

My tr v gi ICMP my ch khng ti c (loi 3, m 3)

Khi ngun nhn c nhng ICMP ny, n s dng li.



2011

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6

Chng 4: Tng Mng

4.1 Gii thiu



nh dng gi tin

nh a ch IPv4

ICMP

IPv6


Vc-t Khong cch

nh tuyn phn cp


RIP

OSPF

BGP



2011

MNG MY TNH CN BN


7

IPv6

ng lc ban u: khng gian a ch 32-bit s c cp pht ht trong t/g ngn.

ng lc khc: nh dng mo u s gip tng tc x l/chuyn tip gi tin

thay i mo u h tr QoS

nh dng gi tin IPv6:

mo u c di c nh 40 byte

khng cho php phn khc



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8

Mo u IPv6 (tt)

Mc u tin: xc nh mc u tin gia cc gi tin Nhn lung: xc nh cc gi tin trong cng lung. (khi nim lung cha thc s chun). Mo u tip theo: xc nh d liu ca giao thc tng trn



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Nhng thay i khc t IPv4

Tng kim tra: c loi b hon ton gim thi gian x l ti mi thit b

Ty chn: cho php, nhng nm ngoi phn mo u, ch nh bi trng Next Header

ICMPv6: phin bn mi ca ICMP nhng thng ip b sung, vd: Gi tin qu ln

nhng chc nng qun l nhm gi-nhiu-ch (multicast)



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10

Chuyn tip T IPv4 Ti IPv6

Khng th nng cp tt c bt ngay mt lc c Lm sao mng c th lm vic vi c cc b nh tuyn IPv4

v IPv6?

To ng hm: IPv6 c mang nh l d liu ca gi tin IPv4 gia cc bt IPv4



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11

To ng hm

A B E F

IPv6 IPv6 IPv6 IPv6

ng hm Gc nhn lun l:

Gc nhn vt l: A B E F

IPv6 IPv6 IPv6 IPv6 IPv4 IPv4



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12

To ng hm

A B E F

IPv6 IPv6 IPv6 IPv6

ng hm Gc nhn lun l:

Gc nhn vt l: A B E F

IPv6 IPv6 IPv6 IPv6

C D

IPv4 IPv4

Flow: X Src: A Dest: F data



Src:B Dest: E


Src:B Dest: E

A-ti-B: IPv6

E-ti-F: IPv6

B-ti-C: IPv6 bn trong

IPv4

B-ti-C: IPv6 bn trong

IPv4



2011

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13

Chng 4: Tng Mng

4.1 Gii thiu



nh dng gi tin

nh a ch IPv4

ICMP

IPv6


Vc-t Khong cch

nh tuyn phn cp


RIP

OSPF

BGP



2011

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14

1 2 3

0111

gi tr trong mo u ca gi ti

gii thut nh tuyn

bng chuyn tip cc b

gtr mo u u ra

0100

0101

0111

1001

3

2

2

1

Tng tc gia nh tuyn, chuyn tip



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15

u

y x

w v

z 2

2 1

3

1

1

2

5 3

5

th: G = (N,E) N = tp cc bt = { u, v, w, x, y, z } E = tp cc g lin kt ={ (u,v), (u,x), (v,x), (v,w), (x,w), (x,y), (w,y), (w,z), (y,z) }

Tru tng ha bng th

Lu : Tru tng ha bng th cng hu dng trong nhng phm tr mng khc V d: P2P, vi N l tp cc thnh vin v E l tp cc kt ni TCP



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16

Tru tng ha bng th: chi ph

u

y x

w v

z 2

2 1

3

1

1

2

5 3

5 c(x,x) = chi ph ca ng (x,x) - vd: c(w,z) = 5 chi ph c th lun bng 1, hoc nghch o vi bng thng, hoc nghch o vi tc nghn

chi ph ca ng i c(x1, x2, x3,, xp) = c(x1,x2) + c(x2,x3) + + c(xp-1,xp)

Cu hi: ng i no t chi ph nht gia u v z ?

Gii thut nh tuyn: tm ra ng i t tn km nht



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17

Phn loi gii thut nh tuyn

Thng tin tng qut hay phn tn?

Tng qut:

tt c bt u c thng tin y v hnh mng v chi ph lin kt

g/thut trang thi kt ni

Phn tn:

bt bit hng xm kt ni vt l ti n, chi ph ti h

qu trnh tnh ton, trao i thng tin vi hng xm c lp i lp li

g/thut vc t khong cch

Tnh hay ng?

Tnh:

tuyn ng chm thay i theo t/gian

ng:

tuyn ng thay i nhanh hn cp nht theo chu k

phn nh li s thay i trong chi ph ng lin kt



2011

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18

Chng 4: Tng Mng

4.1 Gii thiu



nh dng gi tin

nh a ch IPv4

ICMP

IPv6


Vc-t Khong cch

nh tuyn phn cp


RIP

OSPF

BGP



2011

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19

Mt g/thut trng thi-lin kt

gii thut Dijkstra tt c nt u bit hnh

mng, chi ph lin kt

thc hin bi pht tn trng thi lin kt

mi nt c cng th/tin

tnh tuyn ng r nht t 1 nt ti tt c nt khc

to bng chuyn tip cho nt

lp: sau k ln lp, bit c tuyn ng r nht ti k ch

K hiu:

c(x,y): chi ph t nt x ti y; = nu khng phi hng xm trc tip

D(v): gi tr hin ti ca chi ph ca tuyn ng t ngun ti ch v

p(v): nt lin trc trn ng i t ngun ti v

N': tp cc nt m bit c ng i xc nh r nht ti chng



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Gii thut Dijsktra

1 Khi to: 2 N' = {u}

3 vi mi nt v 4 nu v k vi u 5 th D(v) = c(u,v) 6 ngoi ra D(v) = 7

8 Lp 9 tm w khng thuc N' sao cho D(w) l min 10 thm w vo N' 11 cp nht D(v) cho tt c v k vi w v ko thuc N' : 12 D(v) = min( D(v), D(w) + c(w,v) )

13 /* chi ph mi ti v hoc l chi ph c ti v hoc l chi ph 14 tuyn ngn nht ti w cng vi chi ph t w ti v */ 15 ti khi tt c cc nt u thuc N'



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21

Gii thut Dijkstra: V d

Bc 0

1

2

3

4

5

N'

u

ux

uxy

uxyv

uxyvw

uxyvwz

D(v),p(v)

2,u

2,u

2,u

D(w),p(w)

5,u

4,x

3,y

3,y

D(x),p(x)

1,u

D(y),p(y)

2,x

D(z),p(z)

4,y

4,y

4,y

u

y x

w v

z 2

2 1

3

1

1

2

5 3

5



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Gii thut Dijkstra: v d (2)

u

y x

w v

z

Kt qu cy ng i ngn nht t u:

v

x

y

w

z

(u,v)

(u,x)

(u,x)

(u,x)

(u,x)

ch lin kt

Kt qu bng chuyn tip ti u:



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23

Gii thut Dijkstra, tho lun

phc tp gii thut: n nt

mi ln lp: phi kim tra tt c n nt, w, ko thuc N

thc hin n(n+1)/2 ln so snh: O(n2)

c kh nng hin thc tt hn: O(nlogn)

Dng khc:

vd, chi ph lin kt = lng lu lng s dng

A

D

C

B

1 1+e

e 0

e

1 1

0 0

A

D

C

B

2+e 0

0 0 1+e 1

A

D

C

B

0 2+e

1+e 1 0 0

A

D

C

B

2+e 0

e 0 1+e 1

khi u tnh li nh tuyn

tnh li tnh li



2011

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24

Chng 4: Tng Mng

4.1 Gii thiu



nh dng gi tin

nh a ch IPv4

ICMP

IPv6


Vc-t Khong cch

nh tuyn phn cp


RIP

OSPF

BGP



2011

MNG MY TNH CN BN


25

Gii thut Vc t-Khong cch

Phng trnh Bellman-Ford (lp trnh ng)

Xc nh

dx(y) := ch ph ca tuyn ng r nht t x ti y

Khi

dx(y) = min {c(x,v) + dv(y) }

vi min c ly trn tt c hng xm v ca x

v



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26

V d Bellman-Ford

u

y x

w v

z 2

2 1

3

1

1

2

5 3

5 R rng, dv(z) = 5, dx(z) = 3, dw(z) = 3

du(z) = min { c(u,v) + dv(z), c(u,x) + dx(z), c(u,w) + dw(z) } = min {2 + 5, 1 + 3, 5 + 3} = 4

node m t c gi tr min s l node tip theo trong tuyn ng ngn nht bng chuyn tip

phng trnh B-F:



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Dx(y) = chi ph thp nht t x ti y

node x bit chi ph ti mi hng xm v: c(x,v)

node x duy tr vc t khong cch Dx = [Dx(y): y N ]

node x cng duy tr cc vc t khong cch ca hng xm Cho mi hng xm v, x duy tr

Dv = [Dv(y): y N ]



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tng cn bn:

Qua thi gian, mi node gi o c VTKC ca n ti cc hng xm

Khng ng b

Khi mt node x nhn c DV mi t hng xm, n cp nht DV ca n s dng p/trnh B-F:

Vi vi iu kin nh, gi tr ca Dx(y) s hi t ti gi tr chi ph nh nht thc t dx(y)

Dx(y) minv{c(x,v) + Dv(y)} vi mi node y N



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Gii thut Vc t-Khong cch (5)

Lp, khng ng b: mi vng lp cc b gy ra bi:

thay i chi ph lin kt cc b

thng ip cp nht DV t hng xm

Phn tn: mi node thng bo cho

hng xm ch khi DV ca n thay i

hng xm khi s li thng bo cho hng xm ca chng, nu cn

ch cho (thay i trong chi ph ca lin kt cc b hoc t/ip t hng xm)

tnh li cc o c

nu DV ti bt k ch no thay i, thng bo cho hng xm

Mi node:



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x y z

x

y

z

0 2 7

t

c.ph ti

t

t

x y z

x

y

z

0

t

c.ph ti

x y z

x

y

z

c.ph ti

x y z

x

y

z

7 1 0

c.ph ti

2 0 1

2 0 1

7 1 0

t

x z

1 2

7

y

bng node x

bng node y

bng node z

Dx(y) = min{c(x,y) + Dy(y), c(x,z) + Dz(y)}

= min{2+0 , 7+1} = 2

Dx(z) = min{c(x,y) +

Dy(z), c(x,z) + Dz(z)}

= min{2+1 , 7+0} = 3

3 2



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31

x y z

x

y

z

0 2 7

t

c.ph ti

t

t

x y z

x

y

z

0 2 3

t

c.ph ti x y z

x

y

z

0 2 3

t

c.ph ti

x y z

x

y

z

c.ph ti

x y z

x

y

z

0 2 7

t

c.ph ti

x y z

x

y

z

0 2 3

t

c.ph ti

x y z

x

y

z

0 2 3

t

c.ph ti

x y z

x

y

z

0 2 7

t

c.ph ti

x y z

x

y

z

7 1 0

c.ph ti

2 0 1

2 0 1

7 1 0

2 0 1

7 1 0

2 0 1

3 1 0

2 0 1

3 1 0

2 0 1

3 1 0

2 0 1

3 1 0

t

x z

1 2

7

y

bng node x

bng node y

bng node z

Dx(y) = min{c(x,y) + Dy(y), c(x,z) + Dz(y)} = min{2+0 , 7+1} = 2

Dx(z) = min{c(x,y) + Dy(z), c(x,z) + Dz(z)} = min{2+1 , 7+0} = 3



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VTKC: chi ph lin kt thay i

Chi ph lin kt thay i: node nhn ra s thay i chi ph trong lin

kt cc b

cp nht t/tin nh tuyn, tnh li vc t KC

nu DV thay i, thng bo hng xm

tin tt truyn nhanh

x z 1 4

50

y 1

ti t0, y pht hin thay i chi ph lk, cp nht DV ca n, v thng bo hng xm. ti t1, z nhn c cp nht ca y v cp nht bng ca n. N tnh chi ph thp nht ti x v gi cho hng xm DV ca n. ti t2, y nhn c cp nht ca z v cp nht DV ca n. tuyn ng chi ph thp nht ca y khng i v vy n khng gi thng ip no cho z.



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Vc t KC: chi ph lin kt thay i

Chi ph lin kt thay i: tin tt truyn nhanh

tin xu truyn chm vn m ti v cng!

44 vng lp trc khi gii thut n nh

S nhim c ngc: Nu Z i qua Y ti X:

Z ni Y khong cch ca n ti X l v tn (vy Y s khng i qua Z ti X)

liu cch ny c gii quyt hon ton vn m ti v cng khng?

x z 1 4

50

y 60



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34

So snh cc gii thut LS v DV

S phc tp ca th/ip LS: vi n node, E lin kt, O(nE)

th/ c gi

DV: ch trao i gia hng xm vi nhau

t/gian hi t thay i

Tc hi t LS: O(n2) gii thut cn O(nE)

thng ip

c th c dao ng

DV: thi gian hi t thay i

c th c vng lp nh tuyn

vn m-ti-v-cng

Sc chu ng: nu bt trc trc?

LS:

node c th qung b chi ph lin kt sai

mi node ch tnh ton bng ca ring n

DV:

node DV c th qung b chi ph tuyn ng sai

mi bng ca node c dng bi cc node khc

li lan truyn trong mng

Documents

MMT- 04-2.pdf