Repeater, also known as repeater, is the simplest but most used interconnection equipment. Repeater is only suitable for Ethernet and can interconnect two or more Ethernet segments. The repeater only regenerates and amplifies the data signals transmitted on the cable, and then forwards them to other cable segments. For protocols above the link layer, there is no difference between several cables interconnected by repeaters and a single cable (except that the interrupter itself will cause a certain time delay).
The bridge works at the data link layer, connects two LANs, and forwards frames according to the MAC address (physical address), which can be regarded as the "bottom router" (the router works at the network layer and forwards according to the network address such as IP address). It can effectively connect two LANs, limit local communication to this network segment, and forward corresponding signals to another network segment. Bridges are usually used to connect a small number of network segments of the same type. Bridges usually include transparent bridges and source routing bridges.
Routing refers to the activity of moving information from the source location to the target location through the Internet. Generally speaking, in the routing process, information will pass through at least one or more intermediate nodes. Usually, people compare routing and switching, mainly because in the eyes of ordinary users, their functions are exactly the same. In fact, the main difference between routing and switching is that switching takes place at the second layer (data link layer) of the OSI reference model, while routing takes place at the third layer, namely the network layer. This difference determines that routing and switching need to use different control information in the process of moving information, so the ways to realize their respective functions are also different.
They work in physical layer, data link layer and network layer respectively.
[Question 2]: TCP and UDP are two transport layer protocols in TCP/IP protocol. They use IP routing function to send packets to the destination, thus providing network services for applications and application layer protocols (including HTTP, SMTP, SNMP, FTP and Telnet). TCP provides connection-oriented reliable data stream transmission, while UDP provides non-connection-oriented unreliable data stream transmission. Connection-oriented protocols establish point-to-point connections before any data transmission. ATM and Frame Relay are connection-oriented protocols, but they work at the data link layer instead of the transport layer. Ordinary audio phones are also connection-oriented.
[Question 3]: In order to ensure the high reliability of public network, X.25 adopts three-layer protocol and uses virtual circuit technology to build a reliable connection-oriented public network. In the X.25 network, the data transmission between every two nodes must be checked and confirmed to realize the error retransmission mechanism, and reliability measures have been taken at the network layer and data link layer.
The disadvantage is that X.25 consumes a lot of network resources and increases the delay, because it must operate the packet layer between layers, group and reassemble messages, and confirm and retransmit between adjacent nodes.
The answer to this exercise is absolutely correct, so I got full marks.
Question 4: Why are Ethernet and Token Ring not suitable for WAN?
Because Ethernet and Token Ring belong to LAN technology, and LAN technology is designed for networking between computers in a place, which provides network communication between a few computers. Its most fatal limitation is scale, that is, a LAN cannot handle any number of computers, nor can it connect computers distributed in any number of places.
The characteristic of WAN is that it can be continuously expanded to meet the networking needs of multiple computers in multiple locations in a vast area. Moreover, WAN should have enough capacity to enable multiple computers in the same direction to communicate at the same time.
Question 5: What is network management and what are its main functions?
Network management is about planning, supervising, designing and controlling the use of network resources and various activities of the network. The basic goal of network management is to integrate all management subsystems and provide a single control mode for administrators.
The five functions of network management are: configuration management, fault management, performance management, security management and billing management.
[Question 6]:1) is composed of physical layer, link layer, network layer, transport layer and application layer.
(2) The physical layer mainly provides physical connection for the link layer, so that the bit stream can be transmitted transparently.
(3) Link layer mainly realizes error-free communication with "neighbor nodes".
(4) The network layer mainly realizes the correct information transmission between end nodes.
(5) The transport layer mainly completes the reliable transmission service from one terminal endpoint to another.
(6) The application layer provides a convenient and effective network application environment for network users.
[Question 7]: The concepts of service and protocol, and the relationship between them.
A: A service is a set of functional support provided by this layer to the next layer. It defines what operations this layer is going to perform on behalf of its users, regardless of their specific implementation.
Protocol, a set of rules that define the format and meaning of data packet exchange between peer entities at the same level, and entities implement services according to the protocol.
Question 8: Why are Ethernet and Token Ring not suitable for WAN?
Because Ethernet and Token Ring belong to LAN technology, and LAN technology is designed for networking between computers in a place, which provides network communication between a few computers. Its most fatal limitation is scale, that is, a LAN cannot handle any number of computers, nor can it connect computers distributed in any number of places.
The characteristic of WAN is that it can be continuously expanded to meet the networking needs of multiple computers in multiple locations in a vast area. Moreover, WAN should have enough capacity to enable multiple computers in the same direction to communicate at the same time.
(The landlord repeated this question)
Question 9: What is network management and what are its main functions?
Network management is about planning, supervising, designing and controlling the use of network resources and various activities of the network. The basic goal of network management is to integrate all management subsystems and provide a single control mode for administrators.
The five functions of network management are: configuration management, fault management, performance management, security management and billing management.
(Landlord, you are in a hurry. Question 5 repeats this point. Don't worry. )
[Question 10]: Why is TCP/IP protocol important to the Internet?
Due to the characteristics of the Internet, it is necessary to solve the problem of datagram loss and delay in network transmission. In the TCP/IP protocol series, the transmission control protocol TCP provides more reliable transmission services than other general transmission protocols. Specifically, TCP provides a completely reliable (no data duplication or loss), connection-oriented full-duplex streaming service. Allow two applications to establish a connection, send data in both directions and then terminate the connection. Every TCP connection is established reliably and terminated perfectly, and all data before termination will be transmitted reliably. Reliability is the basis of many applications of the Internet, so the importance of TCP/IP protocol to the Internet is self-evident.
[Question 1 1]: What are the main features of computer networks, and what are the components of computer networks?
(1) The main feature of computer network is that computers with information and hardware resources are connected with each other through communication channels, and they can enjoy all kinds of resources on the network.
(2) It consists of three parts: computer network communication subnet, computer network high-level service and computer network application service.
[Question 12]: Briefly describe what simplex communication, duplex communication and half-duplex communication are, and illustrate their practical applications with examples.
A: The so-called single-duplex communication means that information is always one-way. Listening to radio and watching TV are typical examples of single-duplex communication.
The so-called half-duplex communication means that the information flow can be transmitted in two directions, but only in one direction at the same time. Intercom, remember that communication is half-duplex communication.
The so-called full-duplex communication means that two-way communication can be carried out at the same time, that is, one party of communication can receive information while sending it. The communication between computers is mostly full-duplex communication, and QQ chat and phone call are typical examples.
I sent it to you first. I've been doing it for a long time. I'm afraid you can't wait. I'll add it later. Except for the second question, which may be a bit overdone, the others are the answers to the exercises. It takes 1 hour to complete. Sweating like a pig.