Computer Network Interview Questions

OSI and TCP/IP Model

1. What is the OSI seven-layer model? What is the function of each layer?
2. What is the TCP/IP four-layer model?
3. What are the differences between the OSI seven-layer model and the TCP/IP four-layer model?
4. How is data transmitted between layers?
5. What are encapsulation and decapsulation?

Physical Layer and Data Link Layer

6. What is the physical layer? What is its function?
7. What is the data link layer? What is its function?
8. What is a MAC address? What are the differences between MAC address and IP address?
9. What is the ARP protocol? How does ARP work?
10. What is the RARP protocol?
11. What is Ethernet?
12. What is a switch? How does a switch work?
13. What is VLAN? What is its purpose?

Network Layer

14. What is the network layer? What is its function?
15. What is the IP protocol? What are its characteristics?
16. What are the differences between IPv4 and IPv6?
17. What is an IP address? What are the classifications of IP addresses?
18. What is a subnet mask? How to calculate subnets?
19. What are public IP and private IP?
20. What is NAT (Network Address Translation)?
21. What is the ICMP protocol?
22. How does the ping command work?
23. How does the traceroute command work?
24. What is routing? What is a routing table?
25. What are static routing and dynamic routing?
26. What are common routing protocols?

Transport Layer

27. What is the transport layer? What is its function?
28. What is a port? What is the range of port numbers?
29. What are common port numbers?
30. What are the differences between TCP and UDP?
31. Why is TCP reliable transmission?
32. How does TCP ensure reliable transmission?
33. What is TCP three-way handshake? Why three times?
34. What is TCP four-way handshake? Why four times?
35. What is the TIME_WAIT state? Why is TIME_WAIT needed?
36. What is TCP sliding window?
37. What is TCP flow control?
38. What is TCP congestion control?
39. What are TCP congestion control algorithms?
40. What are slow start, congestion avoidance, fast retransmit, and fast recovery?
41. What are TCP sticky packet and packet splitting? How to solve them?
42. What are TCP long connection and short connection?
43. What is TCP Keep-Alive?
44. What are the characteristics of UDP?
45. What are the application scenarios of UDP?
46. How to implement reliable UDP transmission?

Application Layer

47. What is the application layer? What is its function?
48. What are common application layer protocols?

HTTP/HTTPS

49. What is the HTTP protocol? What are its characteristics?
50. What are HTTP request methods? What are the differences between GET and POST?
51. What are HTTP status codes? What do common status codes mean?
52. What are HTTP request message and response message?
53. What are HTTP request headers and response headers?
54. What are Cookie and Session? What are their differences?
55. What is Token? What are the differences between Token and Session?
56. What are the differences between HTTP 1.0, 1.1, and 2.0?
57. What is HTTP persistent connection? How to implement it?
58. What is HTTP pipelining?
59. What is HTTPS? How does HTTPS work?
60. What are the differences between HTTP and HTTPS?
61. What is the SSL/TLS protocol?
62. What is the encryption process of HTTPS?
63. What are symmetric encryption and asymmetric encryption?
64. What is a digital certificate? What is its purpose?
65. What is CA (Certificate Authority)?
66. How does HTTPS prevent man-in-the-middle attacks?

DNS

67. What is DNS? What is its purpose?
68. What is the DNS query process?
69. What are recursive query and iterative query?
70. What is DNS cache?
71. What is DNS hijacking? How to prevent it?
72. What are common DNS record types?

Other Application Layer Protocols

73. What is the FTP protocol? What are FTP working modes?
74. What is the SMTP protocol?
75. What are POP3 and IMAP protocols?
76. What is WebSocket? What are the differences between WebSocket and HTTP?
77. What is the MQTT protocol?

Network Security

78. What is XSS attack? How to prevent it?
79. What is CSRF attack? How to prevent it?
80. What is SQL injection? How to prevent it?
81. What is DDoS attack? How to prevent it?
82. What is SYN Flood attack?
83. What is man-in-the-middle attack?
84. What is replay attack?
85. What is a firewall?

Performance Optimization

86. How to optimize network performance?
87. What is CDN? How does CDN work?
88. What is load balancing? What are common load balancing algorithms?
89. What are reverse proxy and forward proxy?
90. What is HTTP caching? What are caching strategies?
91. What are strong cache and negotiation cache?
92. What are the functions of Cache-Control, Expires, ETag, and Last-Modified?
93. How to reduce HTTP requests?
94. What is domain sharding?
95. What are resource merging and compression?

Other Questions

96. What happens after entering a URL in the browser?
97. What is cross-origin? How to solve cross-origin problems?
98. What is the principle of CORS?
99. What is RESTful API? What are RESTful design principles?
100. What is RPC? What are the differences between RPC and HTTP?