Capitolo 6
Il livello rete dell’architettura TCP/IP
Copyright © 2002 - The McGraw-Hill Companies srl
Telnet
FTP
SMTP
HTTP
RTP
SNMP
TCP
IGMP
ARP
NFS
Applicazione
XDR
Presentazione
RPC
Sessione
Trasporto
UDP
Protocolli
di routing
IP
ICMP
Rete
Data link
Copyright © 2002 - The McGraw-Hill Companies srl
32 bit
VER HLEN
ToS
Identifier
TTL
Total Length
Flag
Fragment
Offset
Protocol Checksum (su intestazione)
Source Address
Destination Address
Options
PAD
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20 byte
1480 byte
Intestazione
Intestazione
(da 1 a 600)
Payload (campo dati)
Primi 600 byte
Intestazione
(da 601 a 1200)
Altri 600 byte
Ultimi
(da 1201 a 1480) 280 byte
Intestazione
Copyright © 2002 - The McGraw-Hill Companies srl
32 bit
Network prefix Host part
Copyright © 2002 - The McGraw-Hill Companies srl
1 23
24 25 27
11111111
255
.
. 255
11000000
192
11111111
10101000
11111111
.
.
255
00001010
.
.
. 168
.
10
Prefisso di Rete
32
11000000
.
.
192
Netmask
01000101
.
.
69
Indirizzo
Host
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1 23
24 26 27
32
1 0 Prefisso naturale Ident. sottorete Host
11111111
255
.
. 255
10110000
176
11111111
00010001
11111111
.
.
255
00001010
.
.
. 17
.
10
Prefisso di Rete
11000000
.
.
192
Netmask
01000101
.
.
Indirizzo
69
Host
Copyright © 2002 - The McGraw-Hill Companies srl
LIS #1
LIS #2
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H
R
IP
R
Pacchetto IP
Ethernet
H
0800
R
Pacchetto IP
FCS
Fisico
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H
ARP Cache
.....
Gg
.....
4
3
h
ARP Reply: da (G,g) per (H,h)
r
1
ARP Request: da (H,h) per (G,?)
.....
Hh
.....
R
2
g
ARP Cache
.....
Hh
.....
G
Indirizzo
Ethernet
Indirizzo IP
Copyright © 2002 - The McGraw-Hill Companies srl
192.168.1.5
Int.
Intestazione IP Dati IP FCS
PPP 172.18.1.6
R2
192.168.15.1
192.168.15.2
192.168.1.5
0800
R1 H1
172.18.1.2
R1
H1
192.168.1.1
192.168.1.5
Intestazione IP Dati IP FCS
172.18.1.6
Intestazione IP Dati IP FCS
172.18.1.6
H2
172.18.1.6
0800
R2 H2
192.168.1.5
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LAN/
WAN
H1
R
H2
192.168.1.1 192.168.2.1
192.168.1.5
192.168.2.3
Copyright © 2002 - The McGraw-Hill Companies srl
LAN/
WAN
R
H2
H1
192.168.1.1
192.168.1.5
192.168.2.1
192.168.2.3
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R
H2
H1
192.168.1.1
192.168.1.5
192.168.1.129
192.168.1.130
Copyright © 2002 - The McGraw-Hill Companies srl
R
H1
192.168.1.1/25
192.168.1.5/24
H2
192.168.1.129/25
192.168.1.130/25
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Autonomous
System 2
v
Autonomous
System 1
Interior gateway
B
Exterior gateway
A
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R4
Backbone area
Internal
router
AS boundary
router
Backbone
router
R5
Area 1
D1
R1
R3
R6
R2
Area 0
R7
R8
Area 2
Area
border router
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Interior gateway
Border gateway
AS 6
R7
D1
R5
R1
R4
R6
R2
AS 1
AS 4
R3
AS 2
R8
Sessione E-BGP
Sessione I-BGP
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(a)
(b)
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23 bit
Indirizzo IP multicast
1110
X X
Y Y
Z Z
Indirizzo MAC multicast
0 1
0 0
5 E
0 X X
Y Y
Z Z
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Mrouter
Normal Router
Tunnel
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R
Indirizzo Ethernet corrispondente a H
Indirizzo IP multicast di tutte le stazioni
Host Membership Query (H,h)
Host Membership Report (G,g)
4
Host
Membership
Report (F,f)
2
1
3
Copyright © 2002 - The McGraw-Hill Companies srl