Basic TCP/IP knowledge and principles

Basic TCP/IP knowledge and Principles note: the following content is a secondary processing of Internet content!
I. Single-choice questions
1. Which three types of data can be sent by TCP/IP? ()
A. multicast, broadcast, and unicast
2. The services provided by TCP/IP in the TCP/IP architecture are (D)
D. Transport Layer Service and Internet layer service
3. The predecessor of the Internet is (C)
C. ARPANET
4. TCP/IP network protocols operate on layers of the OSI model (C)
C. network layer, transmission layer, and Application Layer
5. The maximum three bits of class c ip addresses, from high to low, are (B)
B. 110
6. "Three networks in one" refers to (A) three independent communication networks.
A. Telecommunication Network (Telephone Network), computer network (Digital Network), and cable TV network
7. Among the following IP addresses, the IP addresses belong to Class B are (D ).
D. 156.123.32.12
8. IP address 234.5.6.7 is in the IP address category (D)
D. D Class
9. The maximum transmission packet length of Traditional Ethernet is (B)
B .1518
10. 15 subnets need to be allocated in the CIDR block of a Class C address. Which of the following subnet masks is more suitable? (C)
C. 000000000000240
Note: 240 = 128 + 64 + 32 + 16 (11110000)
11. The logical address 202.112.108.158 indicates that the 32 address is correct in Ipv4 binary format: ()
A.11001010 01110000 01101100 10011110
12. The maximum transmit frame (data) Length over Ethernet is (D) Eight-bit group.
D. 1500.
13. The interconnection device used in OSI (C) is a router.
C. Network Layer
14. Which of the following is the correct Subnet Mask (C ).
C. Set all bits corresponding to the network address to 1.
15. The well-known port number used by Post Office Protocol POP is (C)
C.110
Note: common port numbers and functions
1. POP3 TCP 110: the abbreviation of Post Office Protocol 3, which specifies how to connect a personal computer to an Internet mail server and the electronic Protocol for downloading emails to receive emails.
2. imap tcp 143: Internet Mail Access Protocol (Interactive Mail Access Protocol), which is one of the Mail Access standard protocols similar to POP3. The difference is that after IMAP is enabled, the emails you receive on the email client are still retained on the server, and the operations on the client are reported to the server, such as deleting emails, mark as read, and the emails on the server will also take corresponding actions.
3. smtp tcp 25: The full name is "Simple Mail Transfer Protocol", that is, Simple Mail transmission Protocol. It is a set of specifications used to transmit mails from the source address to the destination address. It is used to control the transfer mode of mails. The SMTP protocol is a TCP/IP protocol cluster that helps each computer locate the next destination when sending or transferring letters. SMTP authentication is added to prevent spam attacks.
4. Telnet TCP 23: the Telnet protocol is a member of the TCP/IP protocol family and is the standard protocol and main method of the Internet remote login service. It provides users with the ability to complete remote host work on local computers. Use the telnet program on the terminal user's computer to connect to the server. End users can enter commands in the telnet program. These commands will run on the server, just as they are directly entered on the server console.
5. terminal Service TCP 3389: port 3389 is the service port of Windows 2000 (2003) Server Remote Desktop. You can use this port to connect to a remote Server by using connection tools such as "Remote Desktop, if the connection is established, you can enter the user name and password of the system administrator to operate the remote computer just like the local computer. Therefore, the remote server usually closes the port modifier.
6. tftp udp 69: TFTP (Trivial File Transfer Protocol, simple File Transfer Protocol) is a Protocol used in the TCP/IP Protocol family for simple File Transfer between the client and the server, it provides file transmission services that are not complex and costly. It is implemented based on the UDP protocol.
7. http tcp 80: Hypertext transfer protocol (HTTP-Hypertext transfer protocol) is a data transfer protocol that defines the rules for communication between browsers and web servers, and transmits World Wide Web documents over the Internet.
8. ntp udp 123: Network Time Protocol (NTP) is a Protocol used to synchronize computer Time. It can enable computers to access their servers or clock sources (such as quartzels and GPS) for synchronization, it can provide high-precision time correction (the difference between the LAN and the standard is less than 1 millisecond, And the WAN is dozens of milliseconds ), encryption validation can be used to prevent malicious protocol attacks.
9. https tcp 443: Full name: Hypertext Transfer Protocol over Secure Socket Layer) is an HTTP channel for security purposes. It is simply a Secure version of HTTP. That is, the SSL layer is added under HTTP. The Security Foundation of HTTPS is SSL, so the detailed content of encryption requires SSL. It is developed by Netscape and built in its browser. It is used to compress and decompress data and return the results of network upload and return. HTTPS actually uses Netscape's Secure Sockets Layer (SSL) as the child layer of the HTTP application layer. (HTTPS uses port 443 instead of using port 80 as HTTP to communicate with TCP/IP .) SSL uses 40-bit keywords as the RC4 stream encryption algorithm, which is suitable for business information encryption.
10. FTP control TCP 21 FTP default data TCP 20 :( FTP: File Transfer Protocol) enables files to be shared between hosts. FTP uses TCP to generate a virtual connection for controlling information, and then generates a separate TCP connection for data transmission. Control connections use TELNET-like protocols to exchange commands and messages between hosts. The file transfer protocol is used by two computers on the TCP/IP network to transfer files. FTP is one of the earliest protocols used on the TCP/IP network and the INTERNET, it belongs to the application layer of the network protocol group. The FTP client can send commands to the server to download files, upload files, and create or change directories on the server.
11. radius udp 1645: Remote Authentication Dial In User Service for short. RADIUS is a C/S-structured Protocol. Its client is initially a NAS (Net Access Server) Server, any computer running the RADIUS client software can become the RADIUS client. The original purpose was to authenticate and charge dial-up users. After several improvements, a general authentication and billing protocol was formed. The original purpose was to authenticate and charge dial-up users. After several improvements, a general authentication and billing protocol was formed.
12. DHCP server UDP 67: DHCP is short for Dynamic Host Configuration Protocol. It is one of the TCP/IP Protocol clusters and is mainly used to assign Dynamic IP addresses to network clients. These allocated IP addresses are a set of IP addresses reserved by the DHCP server in advance, and they are generally consecutive IP addresses. When using DHCP, you must have a DHCP server on the network, while other machines execute DHCP clients. When the DHCP client sends a message requesting a dynamic IP address, the DHCP server will provide an available IP address and subnet mask to the client based on the configured IP address.
13. dns udp 53 dns tcp 53: DNS stands for the Domain Name System and is a core service of the Internet. It is a distributed database that can map Domain names and IP addresses, this makes it easier for people to access the Internet without remembering the number of IP address strings that can be directly read by machines. The TCP and UDP port numbers used by DNS are both 53, mainly UDP, and TCP is used for backup between servers.
14. snmp udp 161: (SNMP, Simple Network Management Protocol) constitutes part of the Internet Protocol cluster defined by the Internet Engineering team (IETF, Internet Engineering Task Force. This protocol supports network management systems to monitor whether devices connected to the network have any management concerns. It consists of a set of network management standards, including an application layer protocol, database schema, and a set of data objects.
15. ipsec UDP 500: IPsec (Internet Protocol Security) is implemented through the IP Protocol (Internet Protocol) to protect the network transmission protocol family of the IP protocol (a set of associated Protocols ). IPsec consists of two parts: (1) Key Exchange Protocol for secure grouped streams; (2) protocol for protecting grouped streams. The former is the Internet Key Exchange (IKE) protocol. The latter includes the encapsulated Security load protocol (ESP Protocol) or authentication header protocol (AH protocol) protocol for encrypting grouped streams, which is used to ensure data confidentiality and source reliability (authentication) and provides the anti-replay service.
16 pptp tcp 1723/L2TP UDP 1701: PPP provides an effective method for managing two-point sessions. However, one disadvantage of PPP is that there is no address mechanism, therefore, a logical connection between two points can only have one PPP, that is, a group of PPP cannot be transmitted on the same logical channel. Tunneling method can achieve this. A tunnel refers to a logical channel in which a group of sessions can be transmitted, which are usually transmitted separately on a logical channel. The three most common Tunneling technologies are PPTP (Point-to-Point Tunneling Protocol), L2F (Layer Two Forwarding), and L2TP (Layer Two Tunneling Protocol, l2TP is an upgrade of PPTP and L2F, which will replace them. L2TP assigns a number to each PPP session at one end of the tunnel to differentiate different PPP sessions and reuse these PPP sessions.
16. The Header Length of IP (version 4) packets should not be greater than (C) bytes.
C. 60
Note: It is composed of IP packet headers and IP packet user data. The length of the IP packet header is generally between 20 and 60 bytes, the maximum length of an IP group cannot exceed 65535 bytes. The first 20 bytes of the packet header are fixed, and the latter is variable.

 
17. In the same Autonomous System, the protocol that automatically transmits accessible information between routers and selects routes is called (B ).
B. BGP
Note: although the BGP protocol is designed for routing between autonomous systems, it can also be used inside autonomous systems and is a type of Dual Routing Protocol. Two BGP adjacent nodes that can communicate between autonomous systems must exist on the same physical link. Border Gateway Protocol (BGP) is a routing protocol for autonomous systems running on TCP. BGP is the only protocol used to process networks like the Internet. It is also the only protocol that can properly handle multi-channel connections between related routing domains.
18. In computer networks, programs running on hosts and hosts can be identified by (.
A. IP address and port number.
19. ARP request frames are sent in (B) mode in the physical network.
B. Broadcast
20. Some fields in the IP Message are used to describe the life cycle of the message, that is, the TTL value. The maximum value is ().
A.255 B .256 C.63 D.64
21. TCP uses (C) To differentiate different connections.
C. IP address + port number
22. Which of the following names does not meet the requirements of the TCP/IP Domain Name System? ().
A. www-nankai-edu-cn
24. The protocol for obtaining emails is (C)
C. POP3 protocol
25. Which ports are well-known ports? ()
A.1-1023
26. In a network with a subnet mask of 255.255.255.240.0, (D) is not a valid host address.
D.150.150.47.255
27. Which of the following statements about how TCP works is false? ().
A. the TCP packet segment is transmitted as an IP datagram, and the arrival of the IP datagram may be out of order, so the arrival of the TCP packet segment may also be out of order. In this case, the data received by the application layer is also out of order.
28. In TCP/IP, TCP-based applications include (B ).
B. SMTP
Note:
TCP: HTTP, FTP, SMTP, TENET, POP3, Finger, NNTP, IMAP4,
UDP: BOOTP, DHCP, NTP, TFTP, SNMP
DNS can be based on TCP or UDP ~~ ·
29. RIP packets are encapsulated in (C) datagram for transmission.
C. UDP
30. The well-known port number used by SMTP is (B ).
B .25
31. The two-byte IP protocol type in the IP header indicates the content carried by the IP data packet, and the value of the TCP packet is ().
A.6
Note: The Protocol field determines the upper-layer protocol transmitted within the data packet. Similar to the port number, the IP protocol uses the Protocol Number to distinguish the upper-layer protocol. The TCP protocol is 0x06, And the UDP protocol is 0x11. Icmp: 0x01; iGmp 0x02: EGP 0x08; iGP 0x09; IPV6 41; OSPF 89
 
32. Which of the following statements about UDP datagram is false? (D ).
D. Provide message feedback
33. The Simple Network Management Protocol works on the (B) layer and communicates with each other using the (B) layer protocol.
B. Application Layer and Transmission Layer
34. The TRACERT protocol is (C ).
C. TCP
35. Route table (D) In the router ).
D. The path to the destination network must be included.
36. The services provided by TCP/IP in the TCP/IP architecture are (D)
D. Transport Layer Service and Internet layer service
37. The IP protocol provides the (B) type.
B. connectionless datagram Service
 
38. The purpose of using subnet planning is (D ).
A. Divide A large network into multiple smaller networks. B. Improve IP address utilization.
C. Enhanced network manageability D. All of the above are
39. for IP addresses 192.168.168.0, 192.168.169.0, 192.168.170.0, and 192.168.171.0, the combination of these four class C addresses into a supernetwork should use a subnet mask (C ).
C.20.240.248.0
40. The ethernet address can be in the following format: ()
A. unicast, broadcast, and Multicast
41. Which of the following statements is true? ().
A. FTP can be based on TCP or UDP
 
42. If the subnet mask of A Class A address is 255.255.240. 0, A total of (D) bits are used to divide subnets.
D.12
43. At the network layer, the IP Module determines which module to send the data in the datagram to for processing based on the protocol value in the IP datagram header. When the Protocol value is (D ), data should be handed over to the UDP module for processing
D.17
44. At the network layer, the IP Module determines the data in the datagram to which module for processing based on the protocol value in the IP datagram header. When the Protocol value is (C ), data should be handed over to the TCP module for processing
C.6
45. The Transport Layer Protocol and default port used by the TELNET server are: (D)
D. UDP/23
46. Table items that use the host's IP address as the destination address are referred to as (B ).
B. Specific Host Routing

 
47. If the starting serial number of A data segment is 1, the receiver's confirmation number of this data segment is 1000, indicating ().
A. You have successfully received 999 bytes.
48. Which of the following statements about IP addresses are true? ).
A.34.45.67.111/8 is A Class A address.
49. Which of the following is NOT the tag (E) in the beginning of TCP ).
E. DF
50. OSPF packets are encapsulated in (D) datagram for transmission.
D. TCP
51. Which of the following protocols belong to the network layer protocol? (D)
D. ICMP and IP
53. When TFTP transfers a file, each file is fixed D.
D. 512 K
54. Boot Protocol BOOTP is a boot protocol designed for non-disk nodes on the network. When a non-disk node is started, it needs to obtain the following information from the Internet: (D)
A. Your own IP address B. IP address of the file server
C. Run the initial memory image D. All the above are
55. The difference between r1_1 and r1_2 is (D)
A. Support for more IP addresses B. extend the support for subnet routing by passing the subnet mask
C. The maximum number of hops specified is different D. None of the above
Note:
1. r1_1 is a class routing protocol, r1_2 is a class Routing Protocol 2. r1_1 cannot support VLSM, r1_2 can support VLSM 3. r12001 does not have the authentication function. r00002 supports authentication and has two types of authentication: plaintext and MD5. r1_1 does not have the manual summary function. r1_2 can manually summarize r1_1 when the automatic summary function is disabled. r1_1 is a broadcast update, r1_2 is a multicast update, and 6. r12001 does not mark a route. r00002 can tag a route for filtering and policy 7. the updata sent by r12001 can carry up to 25 route entries, and r12002 can carry up to 24 routes under authentication. the next-hop attribute is not included in the updata package sent by r12001, and r12002 has the next-hop attribute, which can be customized with the route update.
 
56. IP communication between a source IP host and multiple IP hosts in the network is called (B)
A. unicast B. multicast C. Broadcast D. Live Broadcast
57. The purpose of MIME is ().
A. To allow non-ASCII data to be transmitted by EMAIL.
Note: The full name of MIME is "Multipurpose Internet Mail Extensions" multi-purpose Internet Mail extension, which is an Internet standard, MIME supports mail messages in multiple formats, including non-ASCII characters and binary format attachments.
58. If 172.16.100.0/24 and 172.16.106.0/24 addresses are aggregated, select the expression. (D)
D. 172.16.96.0/20
59. What types of IP addresses does DHCP support? (D)
A. Automatic Allocation B. Dynamic Allocation C. Manual allocation D. All above are
60. Main HTTP Communication Methods: (D)
A. Point-to-point approach B. Intermediate server approach
C. cache mode D. The above are
 
2. Fill in blank questions
1. There are two methods for domain name resolution on the TCP/IP Internet: recursive query and repeated query.
2. IPv4 addresses are composed of 32-bit binary numbers, and IPv6 addresses are composed of 128-bit binary numbers.
3. TCP/IP model (in the order from high to low) application layer, transmission layer, network layer, and network interface layer.
4. Email sending using the email protocol (such as SMTP, POP3, or IMAP) requires the participation of the user agent, client email server, and email server.
5. The two-byte IP protocol type in the IP header indicates the content carried by the IP data packet, and the value of the TCP packet is 6.
6. In TCP/IP networks, physical addresses are related to the data link layer, logical addresses are related to the network layer, and port addresses are related to the application layer.
7. the RIP Protocol uses the _ distance vector _ algorithm.
The RIP Protocol has the following features:
(1) RIP is the internal protocol used by the autonomous system, that is, the internal gateway protocol, and uses the distance vector algorithm.
(2) RIP uses UDP port 520 for communication between RIP processes.
(3) There are two major versions of RIP: r1_1 and r1_2. The specific description of r12001 protocol is in RFC1058, and r12002 is an improvement of r12001 protocol. The specific description of the Protocol is in RFC1723.
(4) the RIP Protocol uses the number of hops as the network metric value.
(5) the RIP Protocol uses broadcast or multicast for communication. r1_1 only supports broadcast, while r1_2 also supports broadcast.
(6) The RIP protocol supports passive host mode, that is, the RIP Protocol allows the host to only receive and Update route information without sending information.
　　
(7) RIP supports default route propagation.
(8) the RIP Protocol has a network diameter of no more than 15 hops and is suitable for small and medium networks. 16 hops are considered inaccessible.
(9) r12001 is a classless routing protocol, and r12002 is a classless routing protocol, that is, r00002 packets contain mask information. [1]
The routing algorithm used by RIP is the Bellman-Ford algorithm, which was first used in a computer network in 1969 and was used as the initial routing algorithm of ARPANET.
8. In the Ipv6 address structure, each IP address is 128 characters in length.
9. the maximum number of hops specified by RIP is 15. If the number of hops is 16, the hop cannot be reached.
10. If the host part of the IP address is all 1, it indicates the broadcast address. If the host part of the IP address is all 0, it indicates the network address. 127.0.0.1 is called the loopback address.
11. port numbers can be considered as the egress for communication between computers and the outside world. Generally, servers are identified by well-known port numbers. For example, for every t c p/I P implementation, the FTP server port number is 21, each Telnet server port number is 23, and each TFTP (simple File Transfer Protocol) the Port Number of the server is 59.
12. RFC (Request For Comments) refers to Request annotations. It is a series of technical documents about the Internet.
13. The host address 101.11.100.100/255.255.252.0 broadcast address is 101.11.103.255.
14. SMTP communication involves three phases: establish a connection, send mail, and release a connection.
15. In TCP/IP, information has different names at different levels. In a physical channel, the transmission format is bit stream, the link layer information transmission format is data frame, the network layer information format is datagram, and the transmission layer information format is grouping.
16. The maximum transmission packet length of Traditional Ethernet is 1518.
17. Routing Protocols can be divided into two categories: Internal Gateway Protocol and Border Gateway Protocol. The former is used in an interconnected network that can be managed by autonomous systems, and the latter is used between autonomous systems.
18. The DNS server can receive two types of resolution: recursive resolution and repeated resolution.
19. The most basic reliability technologies adopted by TCP include traffic control, congestion control, and error control. Among them, traffic control mainly uses the sliding window protocol.
20. In the communication system, the sender is called the source, and the receiver is called the sink.
21. The Internet is a unified and consistent network that connects existing and heterogeneous networks through network interconnection technology.
22. tcp syn Flood Network Attacks use the three handshakes required during TCP connection establishment to attack the target.
23. The IP Datagram Protocol Identifier Field specifies the protocol for IP datagram encapsulation. When the Identifier Field is 6, TCP is encapsulated, when the ID field is 17, UDP protocol is encapsulated. When the ID field is 1, ICMP protocol is encapsulated.
 
Iii. Answer questions
2. Use the same TCP connection for FTP commands and data. (×)
7. the uniqueness of an IP address means that any computer connected to the Internet can have only one IP address. (×)
8. The switch works at the OSI model network layer. (×)
9. The HTTP service port must be set to 80. (×)
12. The Common File Transfer Protocol (TFTP) uses the TCP Service. (×)
17. UDP is an unreliable communication protocol, so it does not need to provide verification fields for its header information. (×)
18. TCP congestion control uses the sender's window to control the speed of the data stream injected into the network. After the data flow injected into the network is slowed down, the congestion will be removed. (×)
19. Dynamic Host Configuration Protocol BOOTP is developed based on the DHCP protocol. It enables clients to obtain relevant configuration information on TCP/IP networks. (×)
Iv. Short answer
1. Draw out the ing between the Open System Interconnection Model of the International Standardization Organization and the TCP/IP protocol layer
A:

2. Draw the relationship between each protocol module of the TCP/IP protocol cluster.


3. What is a non-Class address? What are the requirements for classless block?
A: classless addresses remove the concepts of Class A addresses, Class B addresses, and class C addresses. They are no longer predefined by the first few bits of the addresses. Each address only contains the network number and host number. The whole IP address space is divided into blocks of different sizes. Each block corresponds to a physical network.
The requirement for each classless block is that the block consists of 2 MB consecutive IP addresses. The starting address of the block must be an address that can be divisible by 2 MB.
 
4. Draw the format of the TCP segment.
 
 
5. format the IP datagram.

 
6. The whole process of obtaining an IP address (domain name resolution) from a domain name on the workstation.
A: (1) After obtaining the domain name, the upper-layer network process on the workstation first checks whether there is a corresponding record in the local DNS cache. If yes, it is directly resolved to an IP address.
(2) If the local cache does not exist, a DNS request datagram is constructed, and the preferred DNS location is set based on the Local TCP/IP protocol to send a recursive resolution request to the DNS.
(3) After receiving the request, if it is a domain name in the local region, the preferred DNS will query the corresponding records in the local region. If there is no corresponding record, an error indicating that the domain name does not exist will be returned.
(4) If it is not a domain name in the local region, first query whether the corresponding records in the local cache should be matched. If there is a domain name, it will be resolved directly. If not, the system sends a repeated resolution request to the root domain server, starting from the root domain server to perform a top-down search until the final resolution result or failure response is obtained.
(5) If the preferred DNS server is inaccessible, a resolution request is sent to the backup DNS server.
 
7. The Chinese meaning of ARP is (Address Resolution Protocol). Use a simple language to describe how ARP works.
A: 1) First, each host creates an ARP list in its ARP buffer to indicate the correspondence between the IP address and the MAC address.
2 ). when the source host needs to send a packet to the target host, it first checks whether the MAC address corresponding to this IP address exists in its ARP list, if yes, the packet is directly sent to the MAC address. If no, a broadcast packet for the ARP request is sent to the subnet segment to query the MAC address of the target host. This ARP request packet includes the IP address of the source host, the hardware address, and the IP address of the target host.
3). When all hosts in the network receive this ARP request, they will check whether the destination IP address in the packet is consistent with their own IP address. Ignore this packet if they are different. If they are the same, the host first adds the MAC address and IP address of the sender to its ARP list. If the ARP table already contains information about this IP address, overwrite it, and then send an ARP response packet to the source host, telling the other host that it is the MAC address it needs to find;
4) after the source host receives the ARP response packet, it adds the IP address and MAC address of the target host to its ARP list and uses this information to start data transmission. If the source host has not received the ARP response packet, ARP query fails.
 
8. Compare the Differences Between TCP and UDP.
A: (1) UDP is a connectionless transmission protocol and TCP is a connectionless transmission protocol;
(2) TCP ensures data correctness, UDP may cause packet loss, TCP ensures data order, and UDP does not guarantee
(3) There are many requirements for system resources over TCP and fewer UDP;
(4) There is a certain delay in TCP transmission, and the UDP response speed is slightly faster.
 
9. Working Principles of Mobile IP addresses
A: the working principle of the Mobile IP protocol is implemented by the following steps:
(1) The owner proxy and external proxy in the Mobile IP system continuously send Agent Advertisement messages to the Internet.
(2) the mobile node that receives the message knows the existence of the owner proxy and the external region proxy in the environment, and determines whether it is on the Internet or in the external area.
(3) If the mobile node receives a message from the owner proxy, it means that it is still on the Internet. At this time, the mobile function is not enabled.
(4) When the mobile node detects that it is moving to the Internet, it obtains a temporary IP address from the Internet, that is, the forwarding address.
(5) then the mobile node registers with the owner proxy, indicating that it has left the owner network and notifies the owner proxy of the obtained associated address. The owner agent can obtain the current location information of the mobile node at any time.
(6) After registration, when the communication end sends a message to the mobile node, it uses the fixed IP address of the mobile node. The packet will be routed to the VPC of the mobile node and intercepted by the owner proxy. The owner proxy encapsulates the packet and sends the packet to the outbound network of the mobile node through a tunnel.
 
10. A Class B network on the Internet has a subnet mask 255.255.255.240.0. What is the maximum number of hosts in each subnet?
A: For a class B network, a high-end 16-bit network number is formed. The low-end 16-bit is a subnet or host domain. In the low-end 16 bits of the subnet mask, the maximum valid 4 bits is 1111, so the remaining 12 bits (3rd bits and 4th bits) are used for the host number. Therefore, there are 4096 host addresses, but since all 0 and 1 are special addresses, the maximum number of hosts should be 4094.