Xie Xiren after-school computer network seventh edition answers
Chapter 1 Overview
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1-01 computer network to the user can provide those services? A: communication and sharing
1-02 DESCRIPTION packet switching points. A: (1) the message packet, header plus (2) forwards the storage router (3) were combined in a destination
1-03 comparator circuit switched again from various aspects, advantages and disadvantages of the main packet switching and packet switching.
A: (1) a circuit-switched: the end to end communication quality due to the agreed communication resource guarantee reliable, high-efficiency continuous transmission of large amounts of data. (2) exchange messages: walk-bandwidth, dynamic bandwidth using piecewise high efficiency burst data communication, the communication rapidly. (3) packet switching: a highly efficient packet switching, the point quickly, and each small packet routing flexibility, good network survivability.
1-04 Why the Internet is the biggest change since the printing of human communications? Xie Xiren after-school computer network seventh edition answer
A: The integration of other communication networks, play a central role in the information process, to provide the best connectivity and information sharing, provided the first real-time interactive capabilities of various forms of media.
Xie Xiren after-school computer network seventh edition answers
the development of the Internet, roughly 1-05 which is divided into several stages? Please indicate the main features of these stages.
A: From a single network APPANET to the development of the Internet; preliminary molding TCP / IP protocol is completed tertiary structure of the Internet; divided backbone, regional networks and campus networks; forming a multi-layered Internet ISP structure; ISP for the first time.
1-06 Internet standards outlined several stages?
A: (1) Draft (Internet Draft) Internet - at this stage is not the RFC documents. (2) Proposed Standard (Proposed Standard) - From the beginning of this stage becomes the RFC documents. (3) draft standard (Draft Standard) (4) Internet standards (Internet Standard)
1-07 What is the important difference lowercase and uppercase English internet and the Internet beginning in meaning?
A: (1) internet (Internet or Internet): general term that refers to a plurality of computers interconnected by a network formed by the network. ; Especially no agreement (2) Internet (Internet): terminology, refers specifically to the use of the Internet TCP / IP protocol. Difference: the latter is actually a former two-way applications
1-08 computer network Which categories? Various types of network What are the characteristics?
A: By Range: (1) a wide area network WAN: remote, high-speed, is the Internet's core network.
(2) MAN: city limits, link multiple LANs.
(3) LAN: schools, enterprises, institutions, communities.
(4) the PAN area network: a personal electronic device
by the user: the public network: for public operations. Private network:-specific mechanism.
Xie Xiren after-school computer network seventh edition answer
What is the main difference between 1-09 computers on the network backbone and local access network is?
A: The Backbone: remote coverage \ high-speed transmission \ and routers to optimize communications. Local access networks: primarily supports access to local users, achieve retail access, low rate.
1-10 Compare circuit switched and packet switched under the following conditions. Packet to be transmitted a total of x (bit). From the source to the destination point after a total of k link segment, each segment of the link propagation delay is d (s), a data rate b (b / s). Establishing a circuit in a circuit switched time is s (s). When packet-switched packet length p (bit), and each node of the waiting time can be negligible. Q. Under what conditions, delay of packet switching over circuit switching is smaller? (Hint: draw a sketch about the observation segment link k total number of nodes.)
A: The line switching delay: kd + x / b + s , packet-switched, delay: kd + (x / p) (p / b) + (k-1) (p / b), where (k-1) ( p / b) K represents the transmission period, there are (k-1) times the storage transfer delay, when s> time (k-1) (p / b), the group delay of the delay circuit switching exchange score is large, when x >> p, the opposite.
1-11 on the packet-switched network in question, provided the length of the packet and the packet length are x and (p + h) (bit) , where p is the length of the packet data portion, and h is carried by each packet fixed length control information, regardless of the size of p. The ends of the communication link after a total of k segments. Data link rate b (b / s), but the propagation delay, and node queue time may be negligible. If you are going to make a minimum total delay, packet data and asked to be taken as part of the length p how much? (Note: with reference to FIGS. 1-12, a packet switched part, the total delay observed is composed of several parts.) A: The total delay D expression, packet-switched, delay is: D = kd + (x / p) ( (p + h) / b) + (k-1) (p + h) / b D p of the derivative, so that it is equal to 0, to obtain p = [(xh) / ( k-1)] ^ 0.5
1-12 What features two major components of the Internet (the edge portion of the core portion) is? They work What are the characteristics?
A: The edge portion: composed by the host computer, the user directly performs information processing and sharing information; low speed connected to the core network. The core part: each router networking, is responsible for providing high-speed packet switching for the edge of the remote section.
Xie Xiren after-school computer network seventh edition answer
What is the main difference between the communication of client-server mode 1-13 with a peer that? Is there the same place?
A: The former is the strict distinction between services and service providers, the latter no such distinction. The latter is actually a two-way application of the former.
What are common performance indicators 1-14 have a computer network?
A: The rate, bandwidth, throughput, delay, delay-bandwidth product, the RTT round trip time, utilization
1-15 assume that the network utilization rate of 90%. Try to estimate what is now the network delay is the number of times its minimum value?
Solution: Let the network utilization U. Network delay is D, the minimum network delay is D0U = 90%; D = D0 / (1-U) ----> D / D0 = 10 is the minimum network delay is now 10 times
1- What are the performance characteristics of 16 non-computer communication networks have? Non-performance features and performance characteristics What is the difference?
A: The symptoms: macroscopic evaluation of the network's overall external performance. Performance: specific quantitative description of the technical performance of the network.
1-17 transmission distance between the ends of the transceiver 1000km, the signal propagation speed in the medium is 2 × 108m / s. Transmission delay and propagation delay Calculate the following two scenarios:
(1) the data length of 107bit, the data transmission rate of 100kb / s.
(2) Data length 103bit, the data transmission rate of 1Gb / s.
What conclusions can be obtained from the above calculation?
Solutions: (1) Send Delay: ts = 107/105 = 100s = 106 propagation delay TP / (2 × 108) = 0.005s
(2) transmission delay ts = 103/109 = 1μs propagation delay: tp = 106 / (2 × 108) = 0.005s
Conclusion: If large data length low transmission rate, the total delay, the transmission delay is often greater than propagation delay. However, if the data length of short high transmission rate, the propagation delay may be the major component of total delay.
1-18 assumed that the signal propagation speed in the medium is 2 × 108m / s are medium length L:.
(. 1) 10cm (network interface card) (2) 100m (Local Area Network)
(. 3) 100km (Metropolitan Area Network) ( 4) 5000km (WAN)
calculate the number of bits in the above medium when the data rate is 1Mb / s and 10Gb / s being propagated.
Xie Xiren after-school computer network seventh edition answers
Solutions: (1) 1Mb / s: propagation delay = 0.1 / (2 × 108) = 5 × 10-10 bit number = 5 × 10-10 × 1 × 106 = 5 × 10-4 1Gb / s: number of bits 10-10 of × ×. 5. 1 = 109 × × = 10-1. 5
(2) 1Mb / S: propagation delay = 100 / (2 × 108) = 5 × 10-7 bit number = 5 × 10-7 × 1 × 106 = 5 × 10-1 1Gb / s: number of bits. 5 × 10-7 ×. 1 = 109 × 102 ×. 5 =
(. 3) 1Mb / S: propagation delay = 100000 / (2 × 108) = 5 × 10 -4 number of bits = 5 × 10-4 × 1 × 106 = 5 × 1021Gb / s: the number of bits. 5 × 10-4 ×. 1 = 109 × 105 ×. 5 =
(. 4) 1Mb / S: propagation delay = 5000000 / (2 × 108) = 2.5 × 10-2 bit number = 2.5 × 10-2 × 1 × 106 = 5 × 1041Gb / s: number of bits. 1 × 10-2 × 2.5 = 109 × 107 ×. 5 =
1-19 length the transport layer to the application layer data is transmitted 100 bytes, plus the required 20 byte TCP header. And then to the transport network layer, for an 20-byte IP header. Finally, to the data link layer Ethernet transport, working together with header and trailer 18 bytes. Find the data transmission efficiency. Data transmission efficiency means the total data (i.e., plus a variety of application data and header overhead tail) divided by the transmitted application layer data transmitted. If the application layer data length of 1000 bytes, data transmission efficiency is the number?
Solutions: (1) 100 / (100 + 20 + 20 + 18) = 63.3%
(2) 1000 / (1000 + 20 + 20 + 18) = 94.5%
Why 1-20 Network Architecture to adopt a hierarchical structure? Try and give some thought layered architecture similar to everyday life. A: The benefits of stratification: ① between the layers are independent. One layer can use the service provided by its next level without the need to know how the service is implemented. ② good flexibility. When a layer is changed, the same relationship as long as the interface, the layers above or below this layer are not affected. ③ cut the separable structure. The layers may be the most appropriate technology to achieve ④ easy to implement and maintain. ⑤ can promote standardization. With the idea of a layered architecture similar to the daily life of postal systems, logistics systems.
Xie Xiren after-school computer network seventh edition answer
any difference 1-21 protocols and services? What is the relationship? A: The network protocols: Rules for data exchange network and established standards or conventions. It consists of three elements:
(1) Syntax: i.e., the structure or format of data and control information.
(2) semantics: what needs to send control information, i.e., what operation is completed and how to make a response.
(3) Synchronization: the event to achieve a detailed description of the order. Protocol control two peer entities communicate the rules set. Under the control of the protocol, communication between two peer entities so that this layer can serve up layer, and to achieve this layer protocol, also need to use the following layer provides services.
The difference among the protocols and services:
1, to ensure that the protocol can be implemented up layer provides services. Service users can only see this level of service can not be seen following protocol. The following protocol is transparent to the above service users.
2, the protocol is "horizontal", i.e. the protocol control two peer entities communicate the rules. But the service is "vertical", i.e., from the lower service is provided through the interface to the upper interlayer. Services provided by the upper use some commands must be exchanged with the underlying, these commands are called service primitives In OSI.
What are the three elements 1-22 network protocol that? What have meaning? Xie Xiren after-school computer network seventh edition answer
A: Network Protocol: Rules for data exchange network and established standards or conventions. It consists of three elements:
(1) Syntax: i.e., the structure or format of data and control information.
(2) semantics: what needs to send control information, i.e., what operation is completed and how to make a response.
(3) Synchronization: the event to achieve a detailed description of the order.
1-23 Why is a network protocol must be a variety of adverse circumstances are taken into account?
A: Because the network protocol if you do not take full account of adverse circumstances, when the situation changes, the agreement will remain Ideally, wait forever! Like two good friends dating on the phone, 15:00 meet at the park, and agreed there or be square. This agreement is very scientific, because either party can not come if there is a delay, we can not notify the other party and the other party must wait forever! So look at a computer network is correct, we can not just correct under normal circumstances, but also must be very careful inspection protocols can cope with all kinds of anomalies.
1-24 are discussed with five points protocol network architecture, comprising a main function of each layer. Xie Xiren after-school computer network seventh edition answer
A: integrated OSI and TCP / IP advantage, to adopt a principle of architecture. The main function layers: a physical layer tasks is transparently bitstream. (Note: the physical transfer of media information, such as twisted pair, coaxial cable, fiber optic cable, the physical layer in the following, as the 0-th layer) and the definition of the physical layer also connected in-line cable plugs. Task Data Link Layer The data link layer is on the line between two adjacent nodes to transfer error-free frame (Frame) data units. Each frame comprising data and control information necessary. Network Layer The network layer tasks is to select the appropriate routing, transport layer passed down packet transmission station can be
Correctly in accordance with the address to find the destination station, and delivered to the transport layer destination station. Task transport layer The transport layer is a layer upward between the two processes is performed to provide a reliable communication service end to end, so that they can not see the details of the data communication transport layer below. Application layer directly provide services to users of the application process.
Everyday life "transparent" This term test cited an example about 1-25.
A: TV, computer windows operating system, industrial and agricultural products
1-26 Explain the following terms: protocol stack entities, peer layer protocol data unit, a service access point, client, server, client - server approach.
A: The entity (entity) represents any hardware or software process can send or receive information. Protocol control two peer entities communicate the rules set. Client (client) and server (server) refers to two application processes are involved in the communication. Customers are requesting party services, server services provider. Client-server approach is described in the service of the service and relationships between processes. Stack: refers to a computer network system structure uses the hierarchical model, the main function of each layer is achieved from the running layer protocol peer, so each can be used to characterize some of the major protocols, with several levels like a stack Videos layer structure like: in the network architecture, both the communication layers to achieve the same function.
PDU: peer entity data unit of information exchange service access point: the entity of two adjacent layers in the same system for local interaction (ie exchange of information). SAP service access point is an abstract concept, it is a logical interface entity.
1-27 explain the meaning of everything over IP and IP over everthing is. Xie Xiren answer after-school computer network seventh edition
TCP / IP protocol may provide services (so-called everything over ip) answer to a wide range of applications: Allows IP protocols running (on a wide range of so-called network of Internet ip over everything)
Original link: https://blog.csdn.net/gjggj/article/details/90815130