1.2 The network edge

Summary

This video delves into the network's edge, focusing on access networks that link edge devices to the internet via the first hop router. It distinguishes between residential, institutional, and mobile access networks, highlighting their varying bit transmission rates and user sharing requirements. The script also explores physical media like copper wires, fiber optics, and radio for data transmission, touching on wired technologies like Ethernet and DSL, and wireless technologies including Wi-Fi and cellular networks. The discussion sets the stage for deeper explorations in later chapters, providing a foundational understanding of how data moves from devices to the broader internet.

Takeaways

• 🌐 The video discusses the network edge, focusing on access networks and physical media, which are essential for connecting edge devices to the larger internet.
• 🏠 Access networks are categorized into residential, institutional, and mobile networks, each with different characteristics and operators.
• 📶 Residential access networks include cable and DSL, with cable networks being asymmetric and typically faster for downstream data transmission.
• 📡 Mobile access networks are operated by cellular carriers and include Wi-Fi and cellular technologies like 3G, 4G, and upcoming 5G.
• 🏢 Institutional networks are operated by companies, educational institutions, or municipalities and may have different configurations and scales compared to residential networks.
• 🔌 Physical media for network transmission includes copper wires, fiber optics, and radio, each with distinct properties affecting data transmission.
• 📈 The transmission rate (bit rate) and the degree of network sharing among users are critical factors in the performance of access networks.
• 💾 Home networks typically consist of a modem, router, and various wired and wireless links to connect devices within the home.
• 📊 The video script introduces the concept of packets, which are chunks of data sent over a network with added packet headers for routing and management.
• 📚 The script provides a high-level overview of the physical characteristics of transmission media, touching on topics like bit loss, signal interference, and propagation delays without delving into the technical specifics.

Q & A

What is the primary focus of the second video in the series?

The second video focuses on the network's edge, discussing access networks and physical media.

What are the two main topics covered in the video?

The two main topics covered are access networks and physical media, including copper wires, fiber, and radio.

What is an access network?

An access network is the network that connects edge devices to the first hop router into the larger internet.

What are the three types of access networks mentioned in the video?

The three types of access networks are residential, institutional, and mobile access networks.

How does frequency division multiplexing (FDM) work in cable access networks?

In cable access networks, FDM allows signals to be sent at different frequencies without interference, similar to how different FM radio stations operate.

Why are cable access networks typically asymmetric?

Cable access networks are asymmetric because they are designed to transmit data faster in the downstream direction to the home rather than upstream, reflecting the fact that users tend to consume more data than they produce.

What is DSL and how does it differ from cable access networks?

DSL (Digital Subscriber Line) uses existing phone lines to connect directly to a central office, unlike cable networks which are shared. DSL lines are also asymmetric with dedicated upstream and downstream transmission rates.

What are the typical transmission rates for cable and DSL networks?

Cable networks typically have downstream rates of 40 megabits per second to 1.2 gigabits per second and upstream rates of 30 to 100 megabits per second. DSL networks have downstream rates of 24 to 52 megabits per second and upstream rates of 3.5 to 16 megabits per second.

What are the two classes of wireless networks discussed in the video?

The two classes of wireless networks are local wireless networks like Wi-Fi and wide area networks like 3G, 4G, and 5G cellular networks.

How does the physical media affect the transmission of bits?

Physical media can be guided, like copper or fiber optic cables, or unguided, like radio waves. The type of media affects bit loss, signal interference, and propagation delays.

What are some challenges associated with wireless transmission?

Wireless transmission faces challenges such as signal fading over distance, reflection and blocking by objects, interference from other RF signals, and the need for broadcast security.