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Answers to the Chapter 5 "Do I Know This Already?" Quiz 725
a Layer 3 protocol because it is used for control and management of IP. IP is the core part
of the network layer of TCP/IP, so it is also considered to be a Layer 3 protocol.
2
Describe how TCP performs error recovery. What role do the routers play?
TCP numbers the first byte in each segment with a sequence number. The receiving host
uses the acknowledgment field in segments it sends back to acknowledge receipt of the
data. If the receiver sends an acknowledgment number that is a smaller number than the
sender expected, the sender believes the intervening bytes were lost, so the sender resends
them. The router plays no role unless the TCP connection ends in the router--for example,
a Telnet into a router.
3
Does FTP or TFTP perform error recovery? If so, describe the basics of how error
recovery is performed.
Both FTP and TFTP perform error recovery. FTP relies on TCP, whereas TFTP performs
application layer recovery one block of data at a time.
4
How many TCP segments are exchanged to establish a TCP connection? How many are
required to terminate a TCP connection?
A three-way connection establishment sequence is performed, and a four-flow connection
termination sequence is used.
5
Given the IP address 134.141.7.11 and the mask 255.255.255.0, what is the subnet
number?
The subnet is 134.141.7.0. The binary algorithm is shown in the following table.
6
Given the IP address 134.141.7.11 and the mask 255.255.255.0, what is the subnet
broadcast address?
The broadcast address is 134.141.7.255. The binary algorithm is shown in the following
table.
Address
134.141.7.11
1000 0110 1000 1101 0000 0111 0000 1011
Mask
255.255.255.0
1111 1111 1111 1111 1111 1111 0000 0000
Result
134.141.7.0
1000 0110 1000 1101 0000 0111 0000 0000
Address
134.141.7.11
1000 0110 1000 1101 0000 0111 0000 1011
Mask
255.255.255.0
1111 1111 1111 1111 1111 1111 0000 0000
Result
134.141.7.0
1000 0110 1000 1101 0000 0111 0000 0000
Broadcast Address
134.141.7.255
1000 0110 1000 1101 0000 0111 1111 1111
apA.fm Page 725 Monday, March 20, 2000 5:24 PM