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Chn ng
B mn Truyn thng v Mng my tnh
Bi ging c s dng ngun ti liu cung cp bi trng i hc Keio, Nht Bn
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Chn ng l g?
Cc nguyn l chn ngC ch chuyn tip gi tin
Quy tc Longest matching
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C bn v chn ng (1)
Khi mt my trm gi mt gi tin IP ti mt mykhc
Nu a ch ch nm trn cng mt ng truyn vt l:
Chuyn trc tip Nu a ch ch nm trn mt mng khc: Chuyn gin
tip qua b nh tuyn (chn ng)
Router Router
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ch nTmng i
ch n? Tmng i
C bn v chn ng (2)
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Chn ng l g?
C ch my trm hay b nh tuynchuyn tip gi tin t ngun n ch
Cc thnh phn ca chn ng Bng chn ng Thng tin chn ng
Gii thut, giao thc chn ng
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B nh tuyn?
Thit b chuyn tip cc gi tin gia ccmng L mt my tnh, vi cc phn cng chuyn dng
Kt ni nhiu mng vi nhau
Chuyn tip gi tin da trn bng chn ng
C nhiu giao din
Ph hp vi nhiu dng lu lng v phmvi ca mng
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Mt s v d
Cisco 2600
Cisco CRS-1
BUFFALOBHR-4RV
Router mng trc
Router ngoi vi
Router c trung
Juniper M10
Cisco 3700
Foundry NetworksNetIron 800
Hitachi
GR2000-1B
YAMAHA
RTX-1500
PLANEXGW-AP54SAG
http://www.cisco.com.vn
http://www.juniper.net/
http://www.buffalotech.com
http://www.buffalotech.com/http://www.cisco.com.vn/http://www.juniper.net/http://www.buffalotech.com/http://www.buffalotech.com/http://www.juniper.net/http://www.cisco.com.vn/ -
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Bng chn ng
Ch ra danh sch cc ng i c th,c lu trong b nh ca router
Cc thnh phn chnh ca bng chn
nga ch ch/mt n mng Router k tip
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RouterB
Network Next-hop
10.0.0.0/24 A
172.16.0.0/24 C
RouterCRouterA
10.0.0.0/24 192.168.0.0/24 172.16.0.0/24
10.0.0.0/24 172.16.0.0/24
Bng chn ng v c chchuyn tip (1)
Lu quy tc: No routes, no reachability!
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Quy tc Longest matching(1)
Gi s mt a ch mng ch li c nhiu hnmt mc trong bng chn ng
a ch ch : 11.1.2.5
Router k tip no s c s dng?
Network Next hop
11.0.0.0/8 A11.1.0.0/16 B
11.1.2.0/24 C
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Quy tc Longest matching(2)
a ch ch:11.1.2.5 = 00001011.00000001.00000010.00000101
ng i 1:
11.1.2.0/24 = 00001011.00000001.00000010.00000000ng i 2:11.1.0.0/16 = 00001011.00000001.00000000.00000000
ng i 3:
11.0.0.0/8 = 00001011.00000000.00000000.00000000
Longest matching l g?Ti sao phi cn quy tc ny?
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RouterB
Network Next-hop
10.0.0.0/24 A
172.16.0.0/24 C
192.168.0.0/24 Direct
RouterCRouterA
10.0.0.0/24 192.168.0.0/24 172.16.0.0/24
10.0.0.0/24 172.16.0.0/24
Bng chn ng v c chchuyn tip (2)
Q.M t bng chnng trn C
Nu C ni voInternet?
Internet
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ng i mc nh
Nu ng i khng tm thy trong bng chnng ng i mc nh tr n mt router kt tip
Trong nhiu trng hp, y l ng i duy nht 0.0.0.0/0
L mt trng hp c bit, ch tt c cc ng i
Internet
Router A
Router k tip lun l A
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Kt hp ng i (Routingaggregation)
200.23.1.0/24
200.23.2.0/24
200.23.3.0/24
200.23.4.0/24
200.23.0.0/22
200.23.0.0/23
200.23.2.0/23
C bao nhiu mng con trn mng Internet?
S c rt nhiu mc trong bng chn ng?
Cc mng con k tip vi cng a ch ch c th c tng
hp li lm gim s mc trong bng chn ng.
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Kt hp ng i (2)
V d v Viettel Khng gian a ch IP: kh ln
203.113.128.0-203.113.191.255
kt ni n mt mng con ca Vietel (khchhng): Ch cn ch ra ng i n mng Viettel
ng i mc nh chnh l mt dng ca vic
kt hp ng 0.0.0.0/0
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V d v bng chn ng my trm
C:\Documents and Settings\hongson>netstat -rn
Route Table
===========================================================================
Interface List
0x1 ........................... MS TCP Loopback interface0x2 ...08 00 1f b2 a1 a3 ...... Realtek RTL8139 Family PCI Fast Ethernet NIC -
===========================================================================
Active Routes:
Network Netmask Gateway Interface Metric
0.0.0.0 0.0.0.0 192.168.1.1 192.168.1.34 20
127.0.0.0 255.0.0.0 127.0.0.1 127.0.0.1 1
192.168.1.0 255.255.255.0 192.168.1.34 192.168.1.34 20192.168.1.34 255.255.255.255 127.0.0.1 127.0.0.1 20
192.168.1.255 255.255.255.255 192.168.1.34 192.168.1.34 20
224.0.0.0 240.0.0.0 192.168.1.34 192.168.1.34 20
255.255.255.255 255.255.255.255 192.168.1.34 192.168.1.34 1
Default Gateway: 192.168.1.1
===========================================================================
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#show ip route
Prefix Next Hop
203.238.37.0/24 via 203.178.136.14
203.238.37.96/27 via 203.178.136.26203.238.37.128/27 via 203.178.136.26
203.170.97.0/24 via 203.178.136.14
192.68.132.0/24 via 203.178.136.29
203.254.52.0/24 via 203.178.136.14202.171.96.0/24 via 203.178.136.14
V d v bng chn ng Router (trch)
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Chn ng tnh v chnng ng
Chn ng tnhChn ng ng
u im nhc im
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Router B
Network Next-hop
10.0.0.0/24 A
172.16.0.0/24 C
Router CRouter A
10.0.0.0/24 192.168.0.0/24 172.16.0.0/24
Network Next-hop
10.0.0.0/24 B
192.168.0.0/24 B
Network Next-hop
192.168.0.0/24 B
172.16.0.0/24 B
Vn cp nht bng chn ng S thay i cu trc mng: thm mng mi, mt nt mng
b mt in S cn thit phi cp nht bng chn ng
Cho tt c cc nt mng (v l thuyt) Thc t, ch mt s nt mng phi cp nht
172.16.1.0/24
172.16.1.0/24 B 172.16.1.0/24 C
New Network
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Lm th no cp nht?
Chn ng tnh Cc mc trong bng chn ng c sa i
th cng bi ngi qun tr
Chn ng ng T ng cp nht bng chn ng
Bng cc giao thc chn ng
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Chn ng tnh
Khi c s c: Khng th ni vo
Internet k c khi c tnti ng i d phng
Ngi qun tr mng cnthay i
Internet
Next-hop 10.0.0.3
10.0.0.1
10.0.0.3 10.0.0.2
Next-hop 10.0.0.1
Bng chn ng ca 10.0.0.1 (1 phn)
Prefix Next-hop
0.0.0.0/0 10.0.0.3
Kt ni b li
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Chn ng ng
Khi c s c: ng i thay th c cp
nht mt cch t ng
Bng chn ng ca 10.0.0.1 (1 phn)
Prefix Next-hop
0.0.0.0/0 10.0.0.2
0.0.0.0/0 10.0.0.3 Kt ni b li
Kt ni d phng
Internet
Next-hop 10.0.0.3
10.0.0.1
10.0.0.3 10.0.0.2
Next-hop 10.0.0.1
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c im ca chn ng tnh
u n nh An ton
Khng b nh hng bi cc yu t tc ng
Nhc
Cng nhc Khng th s dng t ng kt ni d phng Kh qun l
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Chn ng ng
u D qun l
T ng s dng kt ni d phng
Nhc Tnh an ton
Cc giao thc chn ng phc tp v kh hiu Kh qun l
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Cc gii thut v giaothc chn ng
Gii thut Dijkstra v Bellman-FordGiao thc dng link-state v dng
distance-vector
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Biu din mng bi th
u
yx
wv
z2
2
13
1
1
2
53
5
th vi cc nt (b nh tuyn) v cc cnh (linkt)
Chi ph cho vic s dng mi lin kt c(x,y) Bng thng, tr, chi ph, mc tc nghn
Gi thut chn ng: Xc nh ng i ngn nhtgia hai nt bt k
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Cy ng i ngn nht - SPT
SPT Shortest Path Tree Cc cnh xut pht t nt gc v ti cc l ng i duy nht t nt gc ti nt v, l ng i ngn nht
gia nt gc v nt v Mi nt s c mt SPT ca ring nt
yx
w
u zu
yx
wv
z2
2
1 3
1
1
2
53
5
v
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Tp trung hay phn tn
Tp trung Thu thp thng tin vo mt nt mng S dng cc gii thut tm ng i trn th Phn b bng chn ng t nt trung tm ti
cc nt
Phn tn Mi nt t xy dng bng chn ng ring Giao thc chn ng: Link-state hoc distance-
vector
c s dng ph bin trong thc t
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Tp trung hay phn tn
Thng tin chn ngl cn thit xy dngbng chn ng
Tp trung hay phn tn?
Tp trung: Mi router c thng tin y v trng thi ca mng
Gii thut dnglink state
Phn tn:
Cc nt ch bit c trng thi ca lin kt vt l ti nt kbn
Lin tc lp li vic tnh ton v trao i thng tin vi nt kbn
Gii thut dngdistance vector
Bn ca bn cng l bn
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K hiu
G = (V,E) : th vi tp nh Vv tp cnh E
c(x,y):chi ph ca lin kt xti y; = nu khngphi 2 nt k nhau
d(v):chi ph hin thi ca ng i t nt ngun tint ch. v
p(v):nt ngay trc nt vtrn ng i t ngun tich
T:Tp cc nt m ng i ngn nht c xcnh
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Cc th tc
Init():
Vi mi nt v, d[v]= , p[v]= NIL
d[s]= 0
Improve(u,v), trong d (u,v) u, v l mt cnhno ca Gifd[v] > d[u] + c(u,v) then
d[v] = d[u] + c(u,v)
p[v] = u
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Dijsktras Algorithm
1. Init() ;2. T= ;3. Repeat4. u: u T | d(u)l b nht ;5. T = T {u};6. for all vneighbor(u) v vT7. update(u,v) ;
8. UntilT = V
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Dijkstras algorithm: V d
Step0
1
2
3
45
Tu
ux
uxy
uxyv
uxyvwuxyvwz
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
yx
w
u z
u
yx
wv
z
2
21
3
1
1
2
53
5
vv
x
y
w
z
(u,v)
(u,x)
(u,x)
(u,x)
(u,x)
destination link
Bng chn ng ca u:
SPT ca u:
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Gii thut dng distance-vector (1)
Phng trnh Bellman-Ford (quy hoach ng)
nh ngha
dx(y) := chi ph ca ng i ngn nhtt x ti y
Ta c
dx(y) = min {c(x,v) + dv(y) }
cho tt c cc v l hng xm ca x
v
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Minh ha Bellman-Ford Eq.
u
yx
wv
z2
21
3
1
1
2
53
5
D thy, 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
Nt no lm gi tr trn nh nhtLa chn lnt k tip trong bng chn ng
B-F eq. cho ta bit:
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Gii thut dng distance-vector (2)
tng c bn: DV: Vector khong cch, tm coi l
ng i ngn nht ca t mt nt tinhng nt khc
Mi nt nh k gi DV ca n ti ccnt bn cnh
Khi nt x nhn c 1 DV, n s cpnht DV ca n qua pt Bellman-ford
Vi mt s iu kin, c lng Dx(y)s hi t dn n gi tr nh nhtdx(y)
Ch(Thay i trong DV cant bn cnh)
Tnh lic lng DV
Nu DV thay i, Bochont bn cnh
Mi nt:
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D ( ) i { ( ) D ( ) ( ) D ( )} D (z) min{c(x y)
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x y z
x
y
z
0 2 7
t
chi ph ti
t
t
x y zx
y
z
0 2 3
t
chi ph tix y z
x
y
z
0 2 3
t
chi ph ti
x y zx
y
z
chi ph ti
x y zx
y
z
0 2 7
t
chi ph ti
x y z
x
y
z
0 2 3
t
chi ph ti
x y z
x
y
z
0 2 3
t
chi ph tix y z
x
y
z
0 2 7
t
chi ph ti
x y z
x
y
z 7 1 0
chi 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
thigian
x z12
7
y
nt x
nt y
nt 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
S h ii th t LS DV
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So snh cc gii thut LS v DV
Thng ip trao i LS:n nt, E cnh, O(nE)thng ip
DV: Ch trao i gia cchng xm
Thi gian hi t thayi
Tc hi t LS:Thut ton: O(n2) cn
O(nE) thng ip DV: Thay i
S chc chn:Gii s mtrouter hot ng sai
LS:
nt gi cc chi ph sai
Mi nt tnh ring bng
chn ng -> c v chcchn hn
DV:
DV c th b gi sai
Mi nt tnh ton da trncc nt khc
Li b lan truyn trongmng