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1、1 CHAPTER 1 Introduction Exercises 1. As of January 2009, the RFC with the highest number is RFC 5459, titled RTP Pay- load Format Update. 3. RFC 2014: This RFC discusses the IRTF working group guidelines and proce- dures. 5. RFC 3692 and RFC 1410 are two examples of experimental RFCs. 7. The main R
2、FC for FTP is RFC 959 that has become the standard STD0009. 9. The main RFC related to TCP is RFC 793 (J. Postel) that has become the standard STD0007. 2 1 CHAPTER 2 The OSI Model and the TCP/IP Protocol Suite Exercises 1. The International Standards Organization (ISO) is a multinational body dedica
3、ted to worldwide agreement on international standards. An ISO standard that covers all aspects of network communications is the Open Systems Interconnection (OSI) model. 3. a. Transport layer b. Network layer c. Data link layer d. Application layer e. Physical layer 5. a. Presentation layer b. Sessi
4、on layer c. Data link and transport layers d. Session layer e. Presentation layer 7. If we think about the switch as a passive one (not a bridge), Figure 2.E7 shows the solution. Chapter02.fm Page 1 Saturday, June 13, 2009 8:05 PM 2 9. The header at the transport layer should at least include the so
5、urce and destination port number. This means the size of the header is at least 2 + 2 = 4 bytes. 11. The header at the data link layer should at least include the physical source and destination addresses. This means the size of the header is at least 6 + 6 = 12 bytes. 13. At the physical layer, the
6、 signal representing the bit stream is broadcast to all sta- tions in a network. Every station receives it; there is no need for addresses in this layer. 15. The destination address is needed to define the recipient of the message; the source address is needed if the receiver of the message has to r
7、espond or the intermediate nodes has to report any error the source. Figure 2.E7Solution to Exercise 7 A Physical Physical Data link Data link R1 B B Network Network Transport Transport Application Application Message D5D5D5D5 Message AR1 Link 2Link 1 Chapter02.fm Page 2 Saturday, June 13, 2009 8:05
8、 PM 1 CHAPTER 3 Underlying Technologies Exercises 1. We know that D = T V, where D is the distance, T is the time, and V is the veloc- ity or speed. In other words, T = D / V. We insert the corresponding values to find the time needed for a bit to travel the cable. 3. Assume that the minimum frame s
9、ize is 65 bytes or 520 bits. We have L = T R, where L is the length of the frame, T is the time, and the R is the data rate. We can say T = L / R. The time can be calculated as 5. The padding needs to make the size of the data section 46 bytes. If the data received from the upper layer is 42 bytes,
10、we need 46 42 = 4 bytes of padding. 7. a. Similarities: Each station has an equal right to the medium. Each station senses the medium. b. Differences: CSMA/CD: A station can send if it senses no signal on the line. CSMA/CA: A station needs to inform other stations that it needs the medium for a spec
11、ific amount of time. CSMA/CD: A collision can occur. CSMA/CA: Collisions are avoided. T = D / V = (2500 meters) / (200,000,000 meters/second) = 0.0000125 s = 12.5 s T = L / R = (520 bits) / (10,000,000) bits/second = 0.000052 s = 52 s 2 8. See Table 3.E8. Table 3.E8Exercise 8 FieldsIEEE 802.3IEEE 80
12、2.11 Destination address6 Source address6 Address 16 Address 26 Address 36 Address 46 FC2 D/ID2 SC2 PDU length2 Data and padding1500 Frame body2312 FCS (CRC)4 4 1 CHAPTER 4 Introduction to Network Layer Exercises 1. We mention one advantage and one disadvantage for a connectionless service: a. The c
13、onnectionless service has at least one advantage. A connectionless service is simple. The source, destination, and the routers need to deal with each packet individually without considering the relationship between them. This means there are no setup and teardown phases. No extra packets are exchang
14、ed between the source and the destination for these two phases. b. The connectionless service has at least one disadvantage. The packets may arrive out of order; the upper layer that receive them needs to reorder them. 3. An n-bit label can create 2n different virtual-circuit identifier. 5. Each pac
15、ket started from the source needs to have a fragmentation identification, which is repeated in each fragment. The destination computer use this identifica- tion to reassemble all fragments belonging to the same packet. 7. The delay in the connection-oriented service is always more than the delay in
16、the connectionless service no matter the message is long or short. However, the ratio of the overhead delay (setup and teardown phases) to the data transfer delay (trans- mission and propagation) is smaller for a long message than a short message in a connection-oriented service. 9. A router is normally connected to different link (networks), each with different MTU. The link from which the packet is received may have a larger MTU than the link to which the packet is sent, which m
