Computer Networking 面试题与答案
问题 26. What are the different type of networking / internetworking devices?
Repeater: Also called a regenerator, it is an electronic device that operates only at physical
layer. It receives the signal in the network before it becomes weak, regenerates the
original bit pattern and puts the refreshed copy back in to the link.
Bridges: These operate both in the physical and data link layers of LANs of same type. They
divide a larger network in to smaller segments. They contain logic that allow them to
keep the traffic for each segment separate and thus are repeaters that relay a frame
only the side of the segment containing the intended recipent and control congestion.
Routers: They relay packets among multiple interconnected networks (i.e. LANs of different
type). They operate in the physical, data link and network layers. They contain
software that enable them to determine which of the several possible paths is the
best for a particular transmission.
Gateways: They relay packets among networks that have different protocols (e.g. between a
LAN and a WAN). They accept a packet formatted for one protocol and convert it to a
packet formatted for another protocol before forwarding it. They operate in all seven
layers of the OSI model.
问题 27. What is ICMP?
ICMP is Internet Control Message Protocol, a network layer protocol of the TCP/IP suite used by hosts and gateways to send notification of datagram problems back to the sender. It uses the echo test / reply to test whether a destination is reachable and responding. It also handles both control and error messages.
问题 28. What are the data units at different layers of the TCP / IP protocol suite?
The data unit created at the application layer is called a message, at the transport layer the data unit created is called either a segment or an user datagram, at the network layer the data unit created is called the datagram, at the data link layer the datagram is encapsulated in to a frame and finally transmitted as signals along the transmission media.
问题 29. What is difference between ARP and RARP?
The address resolution protocol (ARP) is used to associate the 32 bit IP address with
the 48 bit physical address, used by a host or a router to find the physical address of
another host on its network by sending a ARP query packet that includes the IP
address of the receiver.
The reverse address resolution protocol (RARP) allows a host to discover its Internet address when it knows only its physical address.
问题 30. What is the minimum and maximum length of the header in the TCP segment and IP datagram?
The header should have a minimum length of 20 bytes and can have a maximum length of 60 bytes.
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