A2.1.2 · Network fundamentals
A2.1.2 · 网络基础
Modern Digital Infrastructure
现代数字基础设施
Streaming a show, paying with a tap of your phone, and a traffic light that adjusts itself for rush hour all lean on completely different pieces of modern digital infrastructure, even though none of it looks any different to the person actually using it.
在线观看电视剧、用手机轻触完成支付,以及交通信号灯根据高峰时段自动调整,这些都依赖完全不同的现代数字基础设施,即便对实际使用者来说,它们看起来毫无区别。
Explainer
讲解
A city's power grid isn't something most people think about, it just has to work, quietly, in the background, so that everything built on top of it (homes, hospitals, traffic lights) can function. Digital infrastructure plays the exact same background role for computing.
一座城市的电网并不是大多数人会去想的东西,它只需要在幕后默默运作,让建立在它之上的一切(住宅、医院、交通信号灯)得以正常运转。数字基础设施在计算领域扮演的正是完全相同的幕后角色。
Digital infrastructure refers to the underlying systems, hardware and networks that modern digital services and applications are built on top of, and depend on to function at all.
数字基础设施指的是现代数字服务与应用程序赖以建立、并且必须依靠其才能运作的底层系统、硬件与网络。
Explainer
讲解
Purpose vs benefit
目的与益处的区别
The statement asks for three genuinely separate things about each piece of infrastructure: its purpose, its benefits, and its limitations. The first two get conflated constantly, so it's worth pulling them apart before going any further.
这条考纲陈述要求针对每一项基础设施分别说明三件真正独立的事:它的目的、它的益处,以及它的局限。前两者经常被混为一谈,因此有必要先把它们区分清楚,再继续深入。
The purpose of something is the specific problem it exists to solve. A benefit is a good outcome that follows once that purpose is actually achieved. Cloud computing's purpose is letting an organisation use someone else's servers whenever it needs to, rather than owning that physical hardware itself; the fact that this happens to save money and scale up easily is a benefit that follows from achieving that purpose, not the purpose itself.
某样事物的目的是它存在所要解决的具体问题。益处则是这个目的一旦真正实现后随之而来的良好结果。云计算的目的是让组织在需要时使用他人的服务器,而不必自己拥有那些实体硬件;而它恰好能省钱、又易于扩展,这是实现该目的之后随之而来的益处,而不是目的本身。
Worked example
示例讲解
Five kinds of infrastructure
五种基础设施
Click each one to see its purpose, a genuine benefit, a genuine limitation, and a real-world example.
点击每一项,查看它的目的、一项真实的益处、一项真实的局限,以及一个真实世界的例子。
Check your understanding
检验你的理解
A ride-hailing app needs to process a car's exact GPS position the instant it changes, so the map on a passenger's phone never lags behind the car's real location. Which piece of infrastructure is built specifically for this kind of instant, low-delay processing?
一款叫车应用需要在汽车的 GPS 位置一发生变化时立即处理该数据,使乘客手机上的地图不会落后于汽车的实际位置。以下哪一项基础设施是专门为这种即时、低延迟处理而设计的?
Common mistake
常见错误
RecurringA common weak answer states a benefit where the purpose was actually asked for, for example answering "what is cloud computing's purpose?" with "it saves money and is flexible." Those are real benefits, but they're consequences of the purpose being achieved, not the purpose itself, and a question specifically asking for the purpose won't award marks for a benefit instead.
反复出现一个常见的薄弱答案会在题目实际问的是目的时,却给出了益处,例如用"它能省钱又灵活"来回答"云计算的目的是什么?"。这些确实是真实的益处,但它们是目的实现之后的结果,而不是目的本身,专门询问目的的题目不会因为写了益处而给分。
Benefit given as purpose: "The purpose of cloud computing is that it's cheaper and more flexible than buying your own servers." States real benefits, but never actually says what cloud computing DOES, which is what a "purpose" question is asking for.
把益处当成了目的: "云计算的目的是它比自己购买服务器更便宜、更灵活。" 陈述了真实的益处,却始终没有说明云计算实际上做了什么,而这正是"目的"类问题所要问的。
Purpose stated directly, benefit kept separate: "Cloud computing exists so that an organisation can use another company's remote servers, whenever it needs to, instead of owning that hardware itself. This brings real benefits, like being cheaper and easier to scale, but those are results of the purpose, not the purpose itself." Answers the actual question asked, then correctly separates out the benefit as a second, related point.
直接说明目的,并将益处分开陈述: "云计算的存在是为了让组织在需要时使用另一家公司的远程服务器,而不必自己拥有那些硬件。这带来了真实的益处,比如更便宜、更容易扩展,但这些都是实现该目的之后的结果,而不是目的本身。" 先正面回答了题目实际问的问题,再正确地把益处作为第二个相关要点分开陈述。
Revision questions
复习题
Past-paper style. Write an answer, then reveal the marking points and mark yourself.
采用历年真题风格。写下答案,然后展开评分要点给自己打分。
[2]Describe the primary purpose of edge computing.
[2]描述边缘计算的主要目的。
Marking points
评分要点
- Edge computing processes data close to where it is generated, on or near the device, rather than sending it all to a distant data centre.
- This cuts the delay before a result is available and reduces the amount of data sent across the network.
- 边缘计算在数据产生的地方附近(在设备上或靠近设备)处理数据,而不是把全部数据发送到遥远的数据中心。
- 这缩短了拿到结果之前的延迟,并减少了跨网络发送的数据量。
[4]A cryptocurrency blockchain has no single central server, yet keeps working even if many individual computers on its network go offline. Explain which piece of digital infrastructure this describes, and why that architecture makes it resilient.
[4]某加密货币的区块链没有单一的中央服务器,但即使其网络中许多独立的计算机离线,它仍能继续运作。解释这描述的是哪一种数字基础设施,以及为什么这种架构使其具有韧性。
Marking points
评分要点
- This describes a distributed system (or the internet as a decentralised infrastructure).
- There is no single central server; the work and the data are spread across many computers (nodes) that coordinate over the network.
- Every node holds a full copy of the blockchain, so if some nodes go offline the remaining nodes still hold the whole ledger and keep verifying and adding transactions.
- There is no single point whose failure stops the system.
- 这描述的是一个分布式系统(或作为去中心化基础设施的互联网)。
- 没有单一的中央服务器;工作和数据分散在许多通过网络协调的计算机(节点)上。
- 每个节点都保存区块链的完整副本,所以如果一些节点下线,其余节点仍然持有整个账本,继续验证和添加交易。
- 没有哪个单一节点的故障会让系统停止。
[4]A small school is deciding whether to buy and maintain its own physical servers, or subscribe to a cloud computing service instead. Discuss one benefit and one limitation of choosing cloud computing for this school.
[4]一所小型学校正在决定是购买并维护自己的实体服务器,还是改为订阅云计算服务。讨论该学校选择云计算的一项益处与一项局限。
Marking points
评分要点
- One benefit: the school avoids the large up-front cost of buying servers and does not have to maintain, cool or replace the hardware itself; it can also scale capacity up or down as needed.
- One limitation: the service depends entirely on a reliable internet connection, so if the connection is slow or down the school cannot reach its systems; there is also an ongoing subscription cost and the school depends on the provider.
- 一个益处:学校避免了购买服务器的大笔前期成本,也不必自己维护、散热或更换硬件;还能按需扩大或缩小容量。
- 一个局限:该服务完全依赖可靠的互联网连接,所以连接慢或断时,学校就访问不到自己的系统;此外还有持续的订阅费用,而且学校要依赖服务商。
Flashcards
记忆卡片
Active recall for this statement’s key terms.
针对本条考纲陈述关键术语的主动回忆练习。
Keep this statement’s practice with you
把这条考纲陈述的练习保存下来
Free account: unlock every revision question and flashcard for A2.1.2, and every other IB CS 2027 statement.
免费账户:解锁 A2.1.2 以及所有其他 IB CS 2027 考纲陈述的全部复习题和记忆卡片。