ICT Core C2 資訊及通訊科技 核心課題 C2
Data is divided into packets by TCP and sent through different paths selected by IP. This allows for efficient transmission and helps avoid network congestion. 數據由TCP分割成封包，並通過IP選擇的不同路徑發送。這允許高效傳輸並有助於避免網絡擁塞。
Only the IP address identifies a device on the Internet. Domain names are translated to IP addresses by DNS. MAC addresses identify physical devices but not their location on the Internet. 只有IP地址識別互聯網上的設備。域名由DNS翻譯成IP地址。MAC地址識別物理設備，但不識別其在互聯網上的位置。
IPv4 uses 32 bits total (4 octets × 8 bits each = 32 bits). Therefore, the total number of possible addresses is 2³² (approximately 4.29 billion). IPv4總共使用32位（4個八位元組 × 每個8位 = 32位）。因此，可能的地址總數為2³²（約42.9億）。
If Ben can browse by IP but not by URL, the DNS server is likely out of service. DNS translates domain names (URLs) to IP addresses. Without DNS, domain names cannot be resolved, but direct IP access still works. 如果Ben可以通過IP瀏覽但不能通過URL，DNS伺服器可能停止服務。DNS將域名（URL）翻譯成IP地址。沒有DNS，域名無法解析，但直接IP訪問仍然有效。
SSL (Secure Sockets Layer) encrypts data during transmission, protecting sensitive information like passwords and account details from being intercepted by hackers. SSL（保密插口層）在傳輸過程中加密數據，保護密碼和帳戶詳細信息等敏感信息不被黑客截獲。
IMAP (Internet Message Access Protocol) and POP3 are used to receive emails. SMTP is used to send emails. HTTP is for web browsing, and FTP is for file transfers. IMAP（網絡信息存取協定）和POP3用於接收電子郵件。SMTP用於發送電子郵件。HTTP用於網頁瀏覽，FTP用於檔案傳輸。
TCP is responsible for dividing data into numbered packets and reassembling them at the destination. IP handles routing and adding addresses to packets. TCP負責將數據分割成編號封包並在目的地重新組裝它們。IP處理路由和為封包添加地址。
This statement is incorrect. IPv4 addresses CAN be represented in hexadecimal format, though they are typically shown in decimal notation (e.g., 192.168.1.1). IPv6 uses hexadecimal by default. 這個陳述是不正確的。IPv4地址可以用十六進制格式表示，儘管它們通常以十進制表示法顯示（例如，192.168.1.1）。IPv6默認使用十六進制。
Both URLs use HTTPS, which means they both use port 443 by default and both use SSL/TLS encryption. Whether using IP or domain name doesn't affect these protocol characteristics. 兩個URL都使用HTTPS，這意味著它們都默認使用端口443，並且都使用SSL/TLS加密。無論使用IP還是域名都不會影響這些協定特性。
SMTP (Simple Mail Transfer Protocol) is used when an email client sends emails to the email server. POP3/IMAP are for receiving emails. Webmail uses HTTP/HTTPS, not POP3/IMAP. SMTP（簡單郵遞傳送協定）用於電子郵件客戶端向電子郵件伺服器發送電子郵件。POP3/IMAP用於接收電子郵件。網絡郵件使用HTTP/HTTPS，而不是POP3/IMAP。
HTTPS uses SSL/TLS encryption to protect data during transmission. Even if hackers intercept the data, they cannot read it without the decryption key. HTTPS使用SSL/TLS加密來保護傳輸過程中的數據。即使黑客攔截數據，沒有解密密鑰也無法讀取。
IP (Internet Protocol) is responsible for routing packets, and routers are the network devices that determine the best path for packets to reach their destination. IP（互聯網協定）負責路由封包，路由器是確定封包到達目的地的最佳路徑的網絡設備。
IPv6 was introduced primarily because IPv4's 4.29 billion addresses are running out due to the rapid growth of Internet-connected devices. IPv6 provides 3.4 × 10³⁸ addresses. 引入IPv6主要是因為由於互聯網連接設備的快速增長，IPv4的42.9億個地址即將耗盡。IPv6提供3.4 × 10³⁸個地址。
In the domain structure, "hk" is the country code TLD, "edu" is the generic TLD, "abc123" is the second-level domain (registration name), and "www" is the hostname. 在域名結構中，"hk"是國家代碼頂級域名，"edu"是通用頂級域名，"abc123"是二級域名（註冊名），"www"是主機名。
All four are involved: (1) IP for packet routing, (2) DNS to translate domain name to IP address, (3) URL to specify the resource location, and (4) HTTPS for secure web page transfer. 四者都涉及：(1) IP用於封包路由，(2) DNS將域名翻譯成IP地址，(3) URL指定資源位置，(4) HTTPS用於安全網頁傳輸。
Sets of rules specifying the format and order of data sent and received between devices 指定設備之間發送和接收數據的格式和順序的規則集
Transmission Control Protocol - Divides data into numbered packets and reassembles them at destination 傳輸控制協定 - 將數據分割成編號封包並在目的地重新組裝
Internet Protocol - Responsible for packet transmission, adding addresses, and routing 互聯網協定 - 負責封包傳輸、添加地址和路由選擇
Small numbered units of data created by TCP for efficient transmission over networks 由TCP創建的小型編號數據單元，用於在網絡上高效傳輸
32-bit address format with 4 octets separated by periods (e.g., 192.168.1.1), providing 2³² addresses 32位地址格式，由句點分隔的4個八位元組（例如，192.168.1.1），提供2³²個地址
128-bit address format with 8 groups of hexadecimal numbers separated by colons, providing 2¹²⁸ addresses 128位地址格式，由冒號分隔的8組十六進制數字，提供2¹²⁸個地址
An 8-bit unit in IPv4 addresses, ranging from 0 to 255 in decimal notation IPv4地址中的8位單元，十進制表示法範圍從0到255
A unique numerical identifier that specifies the location of a device on a network (changeable) 指定設備在網絡上位置的唯一數字標識符（可變）
A permanent hardware identifier assigned by manufacturer to identify physical network devices 製造商分配的永久硬件標識符，用於識別物理網絡設備
Internet Corporation for Assigned Names and Numbers - Manages domain name registration globally 互聯網名稱與數字地址分配機構 - 全球管理域名註冊
Human-readable meaningful names for IP addresses (e.g., google.com) IP地址的人類可讀有意義名稱（例如，google.com）
Fully Qualified Domain Name - Complete domain name including hostname, registration name, and TLD 完整域名 - 包括主機名、註冊名和頂級域名的完整域名
Domain Name System - Translates domain names to IP addresses through name resolution 域名系統 - 通過名稱解析將域名翻譯成IP地址
Server that performs name resolution by translating domain names to IP addresses 通過將域名翻譯成IP地址來執行名稱解析的伺服器
The process of translating a domain name into its corresponding IP address 將域名翻譯成相應IP地址的過程
Generic Top-Level Domain - Common TLDs like .com, .edu, .gov, .org, .net 通用頂級域名 - 常見頂級域名如 .com, .edu, .gov, .org, .net
Country Code Top-Level Domain - Country-specific TLDs like .hk, .jp, .uk, .cn, .au 地區頂級域名 - 特定國家的頂級域名如 .hk, .jp, .uk, .cn, .au
Uniform Resource Locator - Identifies the specific location of a resource on the Internet 劃一資源定位 - 識別互聯網上資源的特定位置
Identifies specific services on a server (e.g., HTTP=80, HTTPS=443) 識別伺服器上的特定服務（例如，HTTP=80, HTTPS=443）
Hypertext Transfer Protocol - Transfers web pages over the Internet (port 80, unsecure) 超文本傳輸協定 - 通過互聯網傳輸網頁（端口80，不安全）
Secure HTTP using SSL/TLS encryption (port 443, secure) 使用SSL/TLS加密的安全HTTP（端口443，安全）
Secure Sockets Layer - Encryption technology used by HTTPS to protect data transmission 保密插口層 - HTTPS使用的加密技術，用於保護數據傳輸
Simple Mail Transfer Protocol - Sends emails to server and distributes between servers 簡單郵遞傳送協定 - 將電子郵件發送到伺服器並在伺服器之間分發
Post Office Protocol - Downloads emails to local computer, can delete from server 郵局協定 - 將電子郵件下載到本地電腦，可從伺服器刪除
Internet Message Access Protocol - Keeps emails on server, synchronises across devices 網絡信息存取協定 - 將電子郵件保留在伺服器上，在設備之間同步
File Transfer Protocol - Transfers files over network, requires authentication 檔案傳輸協定 - 通過網絡傳輸檔案，需要身份驗證
Determine whether each of the following is a valid IP address: 判斷以下每個是否為有效的IP地址：
(a) 19.29.0.256
❌ Invalid IPv4 - The value 256 exceeds the maximum value of 255 for an octet (8-bit range: 0-255) ❌ 無效的IPv4 - 值256超過八位元組的最大值255（8位範圍：0-255）
(b) 127.0.0.1
✅ Valid IPv4 - This is the loopback address (localhost) ✅ 有效的IPv4 - 這是回環地址（localhost）
(c) aa:bb:cc:dd:ee:ff
❌ Invalid IP - This is a MAC address format (6 groups of hex separated by colons), not an IP address ❌ 無效的IP - 這是MAC地址格式（6組十六進制數字用冒號分隔），不是IP地址
(d) 2001:0db8:85h3:0000:0000:8h2e:0370:7334
❌ Invalid IPv6 - Contains 'h' which is not a valid hexadecimal digit (valid hex: 0-9, a-f) ❌ 無效的IPv6 - 包含'h'，這不是有效的十六進制數字（有效的十六進制：0-9, a-f）
(e) 2001:db8::ff00:42:8329
✅ Valid IPv6 - Uses zero compression (::) to represent consecutive groups of zeros ✅ 有效的IPv6 - 使用零壓縮（::）表示連續的零組
Jacky sets up a LAN to share files with his roommates. Jacky建立了一個局域網與室友共享檔案。
(a) What must be identical on all computers for them to communicate? (a) 所有電腦必須有什麼相同才能通訊？
(b) How do switches and computers identify devices in the network? (b) 交換機和電腦如何識別網絡中的設備？
(a)
The communication protocol (TCP/IP) must be identical on all computers for them to communicate properly. 通訊協定（TCP/IP）必須在所有電腦上相同才能正常通訊。
(b)
Switches use MAC addresses to identify physical devices. Computers use IP addresses to identify the location of devices in the network. 交換機使用MAC地址識別物理設備。電腦使用IP地址識別設備在網絡中的位置。
Mr Cheung needs to choose an email protocol for different scenarios: 張先生需要為不同情況選擇電子郵件協定：
(a) The email server only provides 1GB storage. Which protocol should be used and why? (a) 電子郵件伺服器只提供1GB儲存空間。應該使用哪種協定？為什麼？
(b) He needs to access emails from any computer. Which protocol should be used and why? (b) 他需要從任何電腦訪問電子郵件。應該使用哪種協定？為什麼？
(a)
POP3 should be used. POP3 downloads emails to the local computer and can delete them from the server after download, freeing up server storage space. 應該使用POP3。POP3將電子郵件下載到本地電腦，並可在下載後從伺服器刪除，釋放伺服器儲存空間。
(b)
IMAP should be used. IMAP keeps emails on the server and synchronises them across multiple devices, allowing access from any computer. 應該使用IMAP。IMAP將電子郵件保留在伺服器上並在多個設備之間同步，允許從任何電腦訪問。
Lily types "superbeducation.tv" in her browser. Describe the steps involved in displaying the web page, including IP addresses: Lily在瀏覽器中輸入"superbeducation.tv"。描述顯示網頁所涉及的步驟，包括IP地址：
Step 1: DNS Request 步驟1：DNS請求
Lily's browser sends a DNS request to the DNS server (IP: 19.23.44.98) to translate the domain name "superbeducation.tv" into the web server's IP address (23.32.53.122). Lily的瀏覽器向DNS伺服器（IP：19.23.44.98）發送DNS請求，將域名"superbeducation.tv"翻譯成網絡伺服器的IP地址（23.32.53.122）。
Step 2: HTTP Request 步驟2：HTTP請求
The browser sends an HTTP request to the web server (IP: 23.32.53.122) to request the web page. 瀏覽器向網絡伺服器（IP：23.32.53.122）發送HTTP請求以請求網頁。
Step 3: Web Page Display 步驟3：網頁顯示
The web server sends the requested web page back to the browser, which then displays it to Lily. 網絡伺服器將請求的網頁發送回瀏覽器，然後瀏覽器將其顯示給Lily。
Amy wants to set up an online store. Amy想建立一個網上商店。
(a) Why should she use a domain name instead of just an IP address? (a) 為什麼她應該使用域名而不是僅使用IP地址？
(b) She registers "starshop.org.hk". Is this appropriate for a commercial retail website? Explain. (b) 她註冊了"starshop.org.hk"。這對於商業零售網站是否合適？解釋。
(a)
Domain names are meaningful and easy to remember for customers, while IP addresses are long numerical strings that are difficult to remember. A domain name like "starshop.com.hk" is more professional and user-friendly than an IP address like "23.45.67.89". 域名對客戶來說有意義且容易記住，而IP地址是難以記住的長數字串。像"starshop.com.hk"這樣的域名比像"23.45.67.89"這樣的IP地址更專業和用戶友好。
(b)
No, it is not appropriate. The ".org" top-level domain is intended for general organisations (non-profit), not for commercial or retail businesses. For a commercial online store, ".com.hk" would be more appropriate (e.g., "starshop.com.hk"). 不，這不合適。".org"頂級域名用於一般組織（非營利），而不是商業或零售企業。對於商業網上商店，".com.hk"會更合適（例如，"starshop.com.hk"）。
Describe how a photo is transmitted from your computer to a server using TCP/IP. 描述如何使用TCP/IP將照片從您的電腦傳輸到伺服器。
Step 1: Data Division by TCP 步驟1：TCP分割數據
The photo is divided into smaller numbered packets by TCP for efficient transmission. 照片被TCP分割成較小的編號封包以實現高效傳輸。
Step 2: Adding IP Addresses 步驟2：添加IP地址
Each packet is given the source IP address (your computer) and destination IP address (server) by IP. 每個封包由IP添加源IP地址（您的電腦）和目的地IP地址（伺服器）。
Step 3: Routing Through Network 步驟3：通過網絡路由
The packets are routed through different paths in the network. Routers select the best paths to avoid congestion. 封包通過網絡中的不同路徑路由。路由器選擇最佳路徑以避免擁塞。
Step 4: Reassembly at Destination 步驟4：在目的地重新組裝
When all packets arrive at the destination server, TCP reassembles them back into the original photo. 當所有封包到達目的地伺服器時，TCP將它們重新組裝成原始照片。