例外(exception）とは何か

Answer of Exercise 9
Page 1
1. Give the main features of IP (Internet Protocol).
Answer: IP is connectionless and provides best effort delivery, i.e., IP datagram may be
delayed, duplicated, delivered out-of-order and lost. It can accommodate all possible networks.
2. An IP datagram has arrived with the following information in the header (in hexadecimal):
45 00 00 54 00 03 00 00 20 06 00 00 7C 4E 03 02 B4 0E 0F 02
a. Are there any options?
No
b. What is the size of the data? Total Len= 54h=84 bytes, Data size=84-20=64 bytes
c. How many more routers can the packet travel to? 20h=32 routers
d. What is the identification number of the packet?
0003
e. What is the type of upper layer protocol? 06TCP
3. Suppose the network of an organization
is shown in the following figure. Give
a routing table of router R1.
150.100.13.128/25
150.100.13.129
R2
150.100.12.1
150.100.12.0/26
150.100.12.5
H1
R1
150.100.14.3
150.100.14.1
150.100.14.0/24
150.100.14.2
150.100.14.4
R4
150.100.0.1
R3
150.100.15.33
150.100.15.32/27
Outside
Internet
Answer of Exercise 9
Answser:
Destination
127.0.0.0
150.100.12.0
150.100.14.0
150.100.13.128
150.100.15.32
all others
Netmask
255.0.0.0
255.255.255.192
255.255.255.0
255.255.255.128
255.255.255.224
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Page 2
Router/Gateway
127.0.01 (R1 itself)
deliver to a host
deliver to a host
150.100.14.3 (R2)
150.100.14.4 (R3)
150.100.14.1 (R4)
4. How many responses does a computer expect to receive when it broadcasts an ARP
request? Why? How does a computer (attached an Ethernet) know whether an arriving
frame contains an IP datagram or an ARP message?
Answer: No response if computer with the specified IP address in the ARP request does
not exist, or one response if such computer exists. Each hardware frame has a
type field such as type=806ARP message and type=800IP datagram for Ethernet.
5. Order the following ARP events correctly.
a. Host in procession of IP address sends computer physical address
b. Transmission of data to correct host
c. IP address is broadcast
d. IP address and computer address stored in cache memory
Answer: cabd

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