{
  "topic": "http-handshake",
  "type": "single_choice",
  "schema_version": "1.0.0",
  "generated": "2026-09-02T21:20:00+08:00",
  "questions": [
    {
      "id": "sc-001",
      "type": "single_choice",
      "difficulty": 2,
      "tags": [
        "TCP",
        "三次握手"
      ],
      "question": "TCP 三次握手中，第一次握手客户端发送的标志位是什么？",
      "options": {
        "A": "SYN",
        "B": "ACK",
        "C": "FIN",
        "D": "RST"
      },
      "answer": "A",
      "explanation": "第一次握手客户端发送 SYN（Synchronize）标志，表示发起连接请求。ACK 是确认标志，FIN 是结束连接标志，RST 是重置连接标志。",
      "source": null,
      "related": []
    },
    {
      "id": "sc-002",
      "type": "single_choice",
      "difficulty": 3,
      "tags": [
        "TLS",
        "HTTPS",
        "握手"
      ],
      "question": "TLS 1.2 的握手需要多少个 RTT（往返）？",
      "options": {
        "A": "0-RTT",
        "B": "1-RTT",
        "C": "2-RTT",
        "D": "3-RTT"
      },
      "answer": "C",
      "explanation": "TLS 1.2 需要 2-RTT 完成密钥协商。TLS 1.3 优化到 1-RTT，TLS 1.3 的 0-RTT 恢复可以在恢复会话时做到 0-RTT。",
      "source": null,
      "related": []
    },
    {
      "id": "sc-003",
      "type": "single_choice",
      "difficulty": 2,
      "tags": [
        "HTTP/1.x",
        "应用层握手"
      ],
      "question": "HTTP/1.0 和 HTTP/1.1 有应用层握手吗？",
      "options": {
        "A": "有，通过 OPTIONS 请求",
        "B": "有，通过 GET 请求",
        "C": "没有，TCP 连上后直接发请求",
        "D": "有，通过 SETTINGS 帧"
      },
      "answer": "C",
      "explanation": "HTTP/1.0 和 HTTP/1.1 没有应用层握手。TCP 连接建立后，TLS 握手完成后，客户端直接发送 HTTP 请求。SETTINGS 帧是 HTTP/2 的特性。",
      "source": null,
      "related": []
    },
    {
      "id": "sc-004",
      "type": "single_choice",
      "difficulty": 3,
      "tags": [
        "HTTP/2",
        "SETTINGS"
      ],
      "question": "HTTP/2 的 SETTINGS 交换发生在哪个层？",
      "options": {
        "A": "传输层",
        "B": "安全层",
        "C": "应用层",
        "D": "物理层"
      },
      "answer": "C",
      "explanation": "HTTP/2 的 SETTINGS 交换发生在应用层，双方通过 SETTINGS 帧协商 HTTP 协议参数（如最大并发流数、窗口大小等）。它不是传输层的 TCP 握手。",
      "source": null,
      "related": []
    },
    {
      "id": "sc-005",
      "type": "single_choice",
      "difficulty": 4,
      "tags": [
        "HTTP/3",
        "QUIC"
      ],
      "question": "HTTP/3 基于 QUIC 协议，QUIC 运行在什么之上？",
      "options": {
        "A": "TCP",
        "B": "UDP",
        "C": "ICMP",
        "D": "SCTP"
      },
      "answer": "B",
      "explanation": "QUIC 运行在 UDP 之上，它把传输层握手和 TLS 1.3 握手合二为一。首次连接只需 1-RTT，恢复连接可达 0-RTT。",
      "source": null,
      "related": []
    },
    {
      "id": "sc-006",
      "type": "single_choice",
      "difficulty": 2,
      "tags": [
        "TCP",
        "三次握手"
      ],
      "question": "TCP 三次握手的本质目的是什么？",
      "options": {
        "A": "分配端口号",
        "B": "双方各确认一次收发能力",
        "C": "协商传输速率",
        "D": "加密数据"
      },
      "answer": "B",
      "explanation": "三次握手的本质是双方各确认一次收发能力，确保连接可靠。客户端确认自己能发能收，服务器确认自己能发能收。",
      "source": null,
      "related": []
    },
    {
      "id": "sc-007",
      "type": "single_choice",
      "difficulty": 3,
      "tags": [
        "TLS",
        "HTTPS",
        "重放攻击"
      ],
      "question": "TLS 1.3 的 0-RTT 恢复存在什么安全风险？",
      "options": {
        "A": "中间人攻击",
        "B": "重放攻击",
        "C": "DDoS 攻击",
        "D": "SQL 注入"
      },
      "answer": "B",
      "explanation": "0-RTT 恢复虽然快，但存在重放攻击风险。0-RTT 发送的数据不能保证幂等性，因此不适合做敏感操作（如支付）。",
      "source": null,
      "related": []
    },
    {
      "id": "sc-008",
      "type": "single_choice",
      "difficulty": 4,
      "tags": [
        "TCP",
        "三次握手"
      ],
      "question": "为什么 TCP 握手是三次而不是两次？",
      "options": {
        "A": "三次握手更快",
        "B": "两次握手无法防止已失效的连接请求到达服务器",
        "C": "三次握手更安全",
        "D": "三次握手节省带宽"
      },
      "answer": "B",
      "explanation": "两次握手无法防止已失效的连接请求到达服务器。如果客户端的旧 SYN 延迟到达，服务器会误以为是新请求并建立连接，白白浪费资源。三次握手让客户端有最后一次确认的机会。",
      "source": null,
      "related": []
    },
    {
      "id": "sc-009",
      "type": "single_choice",
      "difficulty": 3,
      "tags": [
        "TLS",
        "HTTPS"
      ],
      "question": "TLS 握手完成的三件事不包括以下哪项？",
      "options": {
        "A": "证书验证",
        "B": "密钥协商",
        "C": "加密套件确定",
        "D": "IP 地址分配"
      },
      "answer": "D",
      "explanation": "TLS 握手完成的事包括：证书验证（确认服务器身份）、密钥协商（生成对称加密密钥）、加密套件确定（双方商定使用的加密算法）。IP 地址分配是 DHCP 的工作。",
      "source": null,
      "related": []
    },
    {
      "id": "sc-010",
      "type": "single_choice",
      "difficulty": 4,
      "tags": [
        "HTTP/3",
        "QUIC",
        "TCP"
      ],
      "question": "HTTP/3 相比 HTTP/2 解决了 TCP 的什么问题？",
      "options": {
        "A": "带宽不足",
        "B": "队头阻塞",
        "C": "加密不够",
        "D": "连接数限制"
      },
      "answer": "B",
      "explanation": "HTTP/3 基于 QUIC 解决了 TCP 的队头阻塞问题——单个流丢包不影响其他流。HTTP/2 虽然有多路复用，但底层 TCP 的队头阻塞仍然存在。",
      "source": null,
      "related": []
    }
  ]
}