24 Questions
What is the primary function of an ISP?
To provide access to the Internet for individuals and organizations
What is the main difference between ADSL and DSL?
ADSL is an asymmetric form of DSL, while DSL is a symmetric form of ADSL
What is the role of the IETF in the development of the Internet?
To develop and publish standards for the Internet
What is the primary function of IP?
To route data packets over the Internet
What is the relationship between Wi-Fi and IEEE 802.11?
Wi-Fi is a marketing term for IEEE 802.11, which is a type of wireless network
What is the primary function of TCP?
To ensure error-free data transfer over the Internet
What is the primary role of an ISP in providing Internet services?
To act as an intermediary between applications and the Internet infrastructure
What type of ISP is typically used by home users?
Local ISP
Which of the following is NOT a type of ISP?
Postal ISP
What is the primary function of a national ISP?
To connect regional ISPs to the global Internet infrastructure
Which type of ISP is typically used by large businesses and organizations?
Enterprise ISP
What is the role of a global ISP in providing Internet services?
To manage and regulate the Internet infrastructure globally
What is the primary difference between a regional ISP and a national ISP?
The scope of their services
Which type of ISP is responsible for connecting mobile devices to the Internet?
Mobile ISP
What type of ISP provides internet connection to homes and small businesses?
Local ISP
What is the main function of a central office in a DSL access network?
To transmit voice and data signals to the ISP
What is the primary function of a DSLAM in a DSL access network?
To multiplex data signals
What is the typical transmission rate of a DSL access network?
24-52 Mbps
What type of network is used to connect end systems to a router?
Wireless access network
What is the typical transmission rate of a wireless local area network (WLAN)?
54-450 Mbps
What type of network is used to connect companies and universities to the internet?
Enterprise network
What is the primary function of a router in an enterprise network?
To connect to the ISP
What type of network is used to connect mobile devices to the internet?
Wide-area cellular access network
What is the typical transmission rate of a 4G/5G cellular network?
10’s Mbps
Study Notes
Physical Layer Technologies
- Fiber optic cable has the highest transmission rate and lowest bit error rate in practice.
Jargon and Abbreviations
- Nuts and bolts: the basic practical details.
- HTTP: HyperText Transfer Protocol.
- Wi-Fi: actually IEEE 802.11, but a marketing firm suggested the name Wi-Fi which resembles Hi-Fi.
- There are many types of Wi-Fi: b, a, g, n, ac (wave 1,2), ax.
- TCP: Transmission Control Protocol.
- IP: Internet Protocol.
- ISP: Internet Service Provider.
- IETF: Internet Engineering Task Force.
- RFC: Request for Comments.
- IEEE: Institute of Electrical and Electronics Engineers.
- IoT: Internet of Things.
- DSL: Digital Subscriber Line.
- ADSL: Asymmetric DSL.
Access Networks
- Residential access networks.
- Institutional access networks (school, company).
- Mobile access networks (Wi-Fi, 4G/5G).
Digital Subscriber Line (DSL)
- Uses existing telephone line to central office DSLAM.
- Data over DSL phone line goes to the Internet.
- Voice over DSL phone line goes to the telephone network.
- 24-52 Mbps dedicated downstream transmission rate.
- 3.5-16 Mbps dedicated upstream transmission rate.
Home Networks
- Wireless and wired devices.
- Often combined in a single box.
- Cable or DSL modem.
- WiFi wireless access point (54, 450 Mbps).
- Wired Ethernet (1 Gbps).
- Router, firewall, NAT.
Wireless Access Networks
- Shared wireless access network connects end system to router.
- Via base station aka “access point”.
- Wireless local area networks (WLANs) typically within or around a building (~30 m).
- 802.11b/g/n (WiFi): 11, 54, 450 Mbps transmission rate.
- Wide-area cellular access networks provided by mobile, cellular network operator (10’s km).
- 10’s Mbps transmission rate.
Enterprise Networks
- Companies, universities, etc.
- Enterprise link to ISP (Internet).
- Institutional router.
- Ethernet switch.
- Institutional mail, web servers.
- IEEE: Institute of Electrical and Electronics Engineers.
- WiFi.
The Internet: A “Services” View
- Infrastructure that provides services to applications.
- Provides programming interface to distributed applications.
- “Hooks” allowing sending/receiving apps to “connect” to, use Internet transport service.
- Provides service options, analogous to the postal service.
Assess your understanding of physical layer technologies in computer networks, including transmission rates and bit error rates.
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