Networking Glossary

網路相關術語與概念的主題式整理。

網路設備 (Network Devices)

Hub

Hubs are simply multi-port Repeaters. Facilitates scaling communication between additional hosts. Everyone receives everyone else’s data.

Bridge

Bridges sit between Hub-connected hosts. Only have two ports and learn which hosts are on each side.

Switch

Switches are combination of Hubs and Bridges. Facilitate communication within a network. Switching is the process of moving data within networks.

• L2 Devices: Only use L2 header to make decision
• Use and Maintain MAC Address Table
• Multiple Ports
• Learn which hosts are on each port

Switch Steps

1. Learn: Update MAC address Table with mapping of Switch Port to Source MAC
2. Flood: Duplicate and send frame out all switch ports (except receiving port)
3. Forward: Use MAC address Table to deliver Frame to appropriate switch port

Router

Facilitate communication between networks. Routing is the process of moving data between networks.

• Known as Routes: Stored in Routing Table
• Router has an IP address and a MAC address on each Interface
• Router forwards packets not destined to themselves

Routing Table

When Router receives packets with an unknown Destination IP, packet is dropped.

Populated Methods:

• Directly Connected: Routes for the Networks which are attached
• Static Routes: Routes manually provided by an Administrator
• Dynamic Routes: Routes learned automatically from other Routers

ARP Table

Router also has ARP Tables - Mapping of L3 to L2 address.

Subnetting

Repeater

中繼器 - Regenerate Signals, allows communications across greater distances.

一個將輸入訊號增強放大的裝置。中繼器是用來加強纜線上的訊號，把訊號送得更遠，以延展網路長度。

Gateway

Each host’s way out of their local Network.

Other Devices

All networking devices perform Routing and/or Switching:

• Access Points
• Firewalls
• Load Balancers
• Virtual Switches
• Layer 3 Switches
• IDS / IPS
• Proxies
• Virtual Router

網路基礎 (Network Fundamentals)

Networks

A network is what transports traffic between Hosts.

Host Hierarchy

IP Address

IP address = 32 bits (IPv4)

• Octet: 一個八位元組 (bit)
• Represented as Four Octets
• Each Octet can be 0-255

IP 位址轉換 (Decimal to Binary Conversion)

這是進行 IP 位址（IPv4）轉換時的基礎知識。每個 IP 位址由 4 組數字組成（例如 192.168.1.1），每一組數字都是一個 8位元 (8-bit) 的區塊（稱為 Octet）。

8-bit 轉換表

十進制轉二進制

口訣：比大小，減法，填 1 或 0。

1. 比較 (Compare)： 將十進制數字與當前位置的「位值」進行比較
2. 判斷 (Decision)：
   • 若數字 < 位值： 填寫 0，移動到下一個位置
   • 若數字 ≥ 位值： 減去該位值，填寫 1，帶餘數移動到下一個位置
3. 重複 (Loop)： 直到第 8 個位置結束

範例：133 → 10000101

結果： 10000101

二進制轉十進制

方法：加總所有為 1 的位值

範例：00100001 → 33

計算：32 + 1 = 33

VLANs (Virtual Local Area Networks)

• Divides Switch Ports into isolated groups
• Divides Switches into multiple “mini-switches”
• Switches do all three actions within each VLAN

進位制與單位 (Number Systems & Units)

Carry (進位)

不同進位制的轉換：

Decimal to Binary

將十進位數除以二，取餘數
152 / 2 = 76 ...0
76 / 2 = 38 ...0
38 / 2 = 19 ...0
19 / 2 = 9 ...1
9 / 2 = 4 ...1
4 / 2 = 2 ...0
2 / 2 = 1 ...0

結果：1001 1000

Computer Memory Units

協定與 API (Protocols & APIs)

REST

REST is not a framework or a library but an architectural style describing an interface based on the URL structure and the HTTP protocol. It describes a stateless, cacheable, convention-based architecture for client-server interaction.

gRPC

The gRPC framework is based on a client-server model of remote procedure calls. A client application can directly call methods on a server application as if it was a local object.

GraphQL

Provides a query language for developing APIs with a framework for fulfilling those queries.

CORS (Cross-Origin Resource Sharing)

跨來源資源共用 - 一種使用額外 HTTP 標頭，令目前瀏覽網站的使用者代理取得存取其他來源（網域）伺服器特定資源權限的機制。

HATEOAS

Hypermedia as the Engine of Application State - RESTful API 設計原則之一。

網路術語 (Networking Terms)

ABS (Adaptive Bitrate Streaming)

自適性串流 - 一種在電腦網路使用的串流技術。過去的串流媒體技術多使用 RTP/RTSP，但現在的技術則大多基於 HTTP，並為更高效在大型分散式 HTTP 網路（例如網際網路）分發而設計。

Buffer

簡單的說，buffer 是一塊暫時儲存著資料的內存（記憶體）。

Simply put, a buffer is a chunk of memory that stores packets temporarily when there is too much data sent to a network interface than what can be transmitted on the physical medium.

CDN (Content Delivery Network)

內容傳遞網路 - 分散式伺服器網路，用於更快速地傳遞內容給使用者。

CIDR (Classless Inter-Domain Routing)

無類別域間路由 - 一種 IP 地址分配方法，可提高網際網路上的資料路由效率。連線至網際網路的每台機器、伺服器和最終使用者裝置都有一個與之關聯的不重複編號，稱為 IP 地址。

Echo Cancellation

回音消除 - 用於通訊中消除回音的技術。

Encoder / Encoding

• Encoder：編碼器 - 將資料轉換為特定格式的裝置或程式
• Encoding：編碼法 - ASCII, Big5, Unicode 等

Head-of-line Blocking

隊頭阻塞 - 當封包必須按順序處理時，前面的封包延遲會影響後面所有封包。

Jitter

在 IP 網路中，封包到達目的地的時間長短不一，稱為 jitter（抖動）。

Narrowband / Wideband

• Narrowband：窄頻 - 相對於寬頻，頻寬較小的通訊方式
• Wideband：寬頻 - 相對於窄頻，頻寬較大的通訊方式

Network Partition

網路分區 - CAP 理論中的 Partition Tolerance。

Opcode

運算程式碼 (Operation Code) - 指令中指定要執行操作的部分。

PLC (Packet Loss Concealment)

封包遺失掩飾 - 用於隱藏封包丟失對音訊/視訊品質影響的技術。

Same Origin Policy

同源政策 - 瀏覽器安全機制，限制不同來源之間的資源存取。

Session & Cookie

URI/URL/URN

URI (Uniform Resource Identifier) - 統一資源標誌符

• URI is an identifier that might not provide enough information to access the resource it identifies
• Generic Form (absolute path): scheme:[//[user[:password]@]host[:port][/path][?query][#fragment]

URL (Uniform Resource Locator) - 統一資源定位符

• URL is an identifier that includes information about how to access the resource it identifies
• Relative path

Common Schemes