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Deploy Examination / deploy (push) Successful in 31s
Cover 9 subtopics from the computer networking documentation: - http-handshake: TCP/TLS/HTTP2/HTTP3 handshakes - http-connection-cost: connection resource overhead & million concurrency - connection-pooling: pool reuse, HTTP/1.1 vs HTTP/2 - http-keepalive: Keep-Alive principle, head-of-line blocking - keepalive-scenarios: when to enable/disable Keep-Alive - domain-sharding: HTTP/1.1 hack, HTTP/2 obsolescence - cdn: edge nodes, caching, DDoS protection - cors: same-origin policy, preflight requests - go-build-strip: -s -w flags, binary size optimization
213 lines
6.2 KiB
JSON
213 lines
6.2 KiB
JSON
{
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"topic": "http-connection-cost",
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"type": "single_choice",
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"schema_version": "1.0.0",
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"generated": "2026-09-02T21:20:00+08:00",
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"questions": [
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{
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"id": "sc-001",
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"type": "single_choice",
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"difficulty": 2,
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"tags": [
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"TCP",
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"内存",
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"内核"
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],
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"question": "操作系统为每个 TCP 连接分配的内核内存大约是多少？",
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"options": {
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"A": "300-1000 KB",
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"B": "3-10 KB",
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"C": "1-2 KB",
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"D": "50-100 KB"
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},
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"answer": "B",
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"explanation": "操作系统为每个 TCP 连接分配的内核内存大约是 3-10 KB，包括发送/接收缓冲区和 TCP 控制块。50-100 KB 是 HTTPS 场景下 TLS 会话的额外消耗。",
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"source": null,
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"related": []
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},
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{
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"id": "sc-002",
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"type": "single_choice",
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"difficulty": 3,
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"tags": [
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"线程模型",
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"协程模型"
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],
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"question": "传统线程模型（Java BIO）每连接的内存消耗大约是多少？",
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"options": {
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"A": "约 4 KB",
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"B": "约 10 KB",
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"C": "约 1 MB",
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"D": "约 10 MB"
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},
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"answer": "C",
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"explanation": "传统线程模型每连接约 1 MB（主要是线程栈），协程模型（Go/async）仅需约 4 KB，异步事件驱动（Nginx）约 2 KB。",
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"source": null,
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"related": []
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},
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{
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"id": "sc-003",
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"type": "single_choice",
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"difficulty": 4,
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"tags": [
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"百万并发",
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"内存"
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],
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"question": "百万并发场景下，使用传统线程模型需要多少内存？",
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"options": {
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"A": "约 10 GB",
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"B": "约 50 GB",
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"C": "约 1 TB",
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"D": "约 4 GB"
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},
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"answer": "C",
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"explanation": "传统线程模型每连接约 1 MB，百万并发需要约 1 TB 内存，这在物理上不可行。协程模型约 4 GB 是可行的。",
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"source": null,
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"related": []
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},
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{
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"id": "sc-004",
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"type": "single_choice",
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"difficulty": 2,
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"tags": [
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"TCP",
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"端口"
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],
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"question": "客户端临时端口的理论上限是多少？",
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"options": {
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"A": "1024",
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"B": "32768",
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"C": "65535",
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"D": "1048576"
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},
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"answer": "C",
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"explanation": "客户端端口是 16 位整数，理论上限 65535。每个 TCP 连接需要一个唯一的四元组（源IP:源端口:目标IP:目标端口）。",
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"source": null,
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"related": []
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},
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{
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"id": "sc-005",
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"type": "single_choice",
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"difficulty": 3,
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"tags": [
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"Go",
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"goroutine",
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"协程"
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],
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"question": "Go goroutine 的初始栈大小是多少？",
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"options": {
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"A": "1 KB",
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"B": "2 KB",
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"C": "4 KB",
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"D": "8 KB"
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},
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"answer": "B",
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"explanation": "Go goroutine 初始栈大小为 2 KB（可动态增长到 1 GB），Java 线程默认栈大小为 1 MB。相同内存下 Go 能创建的并发单元数量是 Java 的约 500 倍。",
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"source": null,
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"related": []
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},
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{
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"id": "sc-006",
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"type": "single_choice",
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"difficulty": 3,
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"tags": [
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"TLS",
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"HTTPS",
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"内存"
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],
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"question": "HTTPS 场景下 TLS 会话缓存每个连接额外消耗多少内存？",
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"options": {
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"A": "3-10 KB",
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"B": "50-100 KB",
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"C": "200-500 KB",
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"D": "1-2 MB"
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},
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"answer": "B",
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"explanation": "HTTPS 场景下 TLS 会话缓存每个连接额外消耗 50-100 KB 内存，百万并发下可能吃掉 50 GB 内存。因此考虑在 CDN 边缘终止 TLS。",
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"source": null,
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"related": []
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},
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{
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"id": "sc-007",
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"type": "single_choice",
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"difficulty": 2,
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"tags": [
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"文件描述符",
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"ulimit"
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],
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"question": "每个 TCP 连接占多少个文件描述符？",
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"options": {
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"A": "0 个",
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"B": "1 个",
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"C": "2 个",
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"D": "4 个"
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},
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"answer": "B",
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"explanation": "每个 TCP 连接占 1 个文件描述符（fd），受系统 ulimit 限制。百万并发需要调大 ulimit 到至少 1048576。",
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"source": null,
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"related": []
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},
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{
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"id": "sc-008",
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"type": "single_choice",
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"difficulty": 4,
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"tags": [
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"异步模型",
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"Nginx",
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"事件驱动"
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],
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"question": "异步事件驱动模型（如 Nginx）每连接的内存消耗大约是多少？",
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"options": {
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"A": "约 1 MB",
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"B": "约 10 KB",
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"C": "约 4 KB",
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"D": "约 2 KB"
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},
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"answer": "D",
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"explanation": "异步事件驱动模型（Nginx）每连接约 2 KB，几乎不占位置。这是最高效的连接模型，但编程复杂度最高。",
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"source": null,
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"related": []
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},
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{
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"id": "sc-009",
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"type": "single_choice",
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"difficulty": 3,
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"tags": [
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"Epoll",
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"Kqueue",
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"IO多路复用"
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],
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"question": "撑住百万并发的关键手段中，Epoll/Kqueue 的作用是什么？",
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"options": {
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"A": "为每个连接开一个线程",
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"B": "不为每个连接开线程，一个线程监控百万 fd",
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"C": "加密所有连接",
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"D": "压缩数据传输"
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},
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"answer": "B",
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"explanation": "Epoll/Kqueue 是 IO 多路复用机制，不为每个连接开线程，一个线程就能监控百万文件描述符，是撑住百万并发的关键手段之一。",
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"source": null,
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"related": []
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},
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{
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"id": "sc-010",
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"type": "single_choice",
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"difficulty": 2,
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"tags": [
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"TCP",
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"资源"
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],
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"question": "TCP 连接的四元组中不包括以下哪项？",
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"options": {
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"A": "源 IP",
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"B": "源端口",
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"C": "协议号",
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"D": "目标端口"
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},
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"answer": "C",
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"explanation": "TCP 连接的四元组是：源 IP、源端口、目标 IP、目标端口。协议号（TCP=6）是固定的，不属于四元组。",
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"source": null,
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"related": []
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}
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]
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} |