p.5
Overview of the Internet
What is the Internet primarily viewed as?
A service infrastructure that provides services to applications.
p.2
Network Edge and Access Networks
What components make up the network edge?
Hosts, access networks, and physical media.
p.25
Internet Structure and ISPs
What does ISP stand for?
Internet Service Provider.
p.1
Overview of the Internet
What is the primary focus of Lecture 1 in the Computer Networks course?
An introduction to Computer Networks and the Internet.
p.24
Internet Structure and ISPs
What does ISP stand for?
Internet Service Provider.
p.17
Packet Switching vs. Circuit Switching
What is circuit switching?
A method where end-to-end resources are allocated and reserved for a call between source and destination.
p.32
Performance Metrics: Loss, Delay, Throughput
What is throughput in networking?
The rate (bits/time unit) at which bits are transferred between sender and receiver.
p.1
Overview of the Internet
Where can textbook resources for the course be found?
At http://gaia.cs.umass.edu/kurose_ross/
What is a protocol?
A set of rules that govern the communication between devices on a network.
p.12
Wireless Access Networks
What connects end systems to routers in a shared wireless access network?
A base station, also known as an access point.
p.5
Overview of the Internet
What types of services does the Internet provide?
Web, VoIP, email, games, e-commerce, social networks, etc.
p.5
Overview of the Internet
What does the Internet provide to applications?
A programming interface with hooks for sending and receiving app programs.
p.24
Internet Structure and ISPs
What role do access networks play in the Internet structure?
They connect users to ISPs.
What is a protocol in general terms?
A set of specific messages sent and actions taken when messages are received or other events occur.
p.17
Packet Switching vs. Circuit Switching
How are resources allocated in circuit switching?
Resources are dedicated and not shared during the call.
What is a protocol?
A set of rules governing the exchange of information.
p.22
Internet Structure and ISPs
What does ISP stand for?
Internet Service Provider.
p.21
Internet Structure and ISPs
What is the role of access ISPs?
To connect users to the Internet.
p.20
Internet Structure and ISPs
What is the problem with connecting each access ISP directly to every other access ISP?
It doesn't scale due to O(N^2) connections.
p.28
Performance Metrics: Loss, Delay, Throughput
What are the four sources of packet delay?
Nodal processing, queueing delay, transmission delay, and propagation delay.
p.28
Performance Metrics: Loss, Delay, Throughput
What does nodal processing delay (d proc) involve?
Checking bit errors and determining the output link.
p.32
Performance Metrics: Loss, Delay, Throughput
What does average throughput refer to?
The rate over a longer period of time.
p.2
Internet Protocol Stack and OSI Model
What are protocol layers?
Hierarchical layers that define how data is transmitted and received over a network.
p.32
Performance Metrics: Loss, Delay, Throughput
If a server has a file of F bits to send, what is the link capacity denoted as?
R s bits/sec for the server and R c bits/sec for the client.
p.34
Performance Metrics: Loss, Delay, Throughput
What does 'R' represent in the context of throughput?
The rate of the backbone bottleneck link in bits/sec.
p.15
Packet Switching vs. Circuit Switching
What happens when the arrival rate to a link exceeds its transmission rate?
Packets will queue and wait to be transmitted on the link.
p.2
Overview of the Internet
What is the Internet?
A global network of interconnected computers that communicate using standardized protocols.
p.21
Internet Structure and ISPs
What is the economic relationship between customer and provider ISPs?
They have an economic agreement.
p.23
Internet Structure and ISPs
What does ISP stand for?
Internet Service Provider.
p.22
Internet Structure and ISPs
What happens if one global ISP is a viable business?
There will be competitors.
p.27
Performance Metrics: Loss, Delay, Throughput
What causes loss in packet transmission?
When the packet arrival rate temporarily exceeds the output link capacity, causing packets to be dropped if no free buffers are available.
What is an example of a computer network protocol?
TCP connection request and response.
p.12
Wireless Access Networks
Who provides wide-area wireless access?
Telecommunications (telco) operators.
p.39
Overview of the Internet
What is the main focus of the material covered?
An overview of the Internet and networking concepts.
p.31
Performance Metrics: Loss, Delay, Throughput
Who may retransmit a lost packet?
The previous node, the source end system, or it may not be retransmitted at all.
p.9
Access Network Technologies: DSL and Cable
How are different channels transmitted in frequency division multiplexing?
In different frequency bands.
p.23
Internet Structure and ISPs
What is a peering link?
A connection between ISPs for exchanging traffic.
p.38
Internet Protocol Stack and OSI Model
What is a segment in networking?
The encapsulated message at the transport layer.
p.19
Internet Structure and ISPs
What is a key challenge in connecting millions of access ISPs?
Determining how to connect them together.
p.24
Internet Structure and ISPs
How do regional networks relate to access networks?
They connect access networks to ISPs.
p.20
Internet Structure and ISPs
What does O(N^2) signify in the context of ISP connections?
It indicates that the number of connections grows quadratically with the number of ISPs.
What do protocols define in network communication?
The format, order of messages sent and received among network entities, and actions taken on message transmission and receipt.
p.18
Internet Structure and ISPs
How do end systems connect to the Internet?
Via access ISPs (Internet Service Providers).
p.16
Routing and Forwarding in Networks
What is the primary function of forwarding in a network?
To move packets from a router's input to the appropriate router output.
p.27
Performance Metrics: Loss, Delay, Throughput
What is one reason for delay in packet transmission?
Packets queuing in router buffers while waiting for their turn to be transmitted.
p.18
Internet Structure and ISPs
What types of ISPs are mentioned?
Residential, company, and university ISPs.
p.28
Performance Metrics: Loss, Delay, Throughput
What is the formula for total nodal delay?
d nodal = d proc + d queue + d trans + d prop.
p.3
Overview of the Internet
What are hosts in the context of the Internet?
Hosts are end systems running network applications.
p.13
Performance Metrics: Loss, Delay, Throughput
How is packet transmission delay calculated?
Time needed to transmit an L-bit packet into the link is L (bits) / R (bits/sec).
p.16
Routing and Forwarding in Networks
What is a routing algorithm used for?
To determine the best path for packets to travel from source to destination.
How do human protocols differ from network protocols?
Human protocols involve communication between people, while network protocols govern communication between machines.
p.2
Performance Metrics: Loss, Delay, Throughput
What are the key performance metrics in networking?
Loss, delay, and throughput.
p.36
Internet Protocol Stack and OSI Model
What functions does the session layer provide?
Synchronization, checkpointing, and recovery of data exchange.
p.38
Internet Protocol Stack and OSI Model
What is encapsulation in networking?
The process of wrapping data with protocol information at each layer of the OSI model.
p.5
Overview of the Internet
What types of networks are part of the Internet infrastructure?
Mobile network, global ISP, regional ISP, home network, institutional network.
p.9
Access Network Technologies: DSL and Cable
What technology allows different channels to be transmitted in a cable network?
Frequency division multiplexing.
p.11
Access Network Technologies: DSL and Cable
How do end systems typically connect in an Ethernet network?
They connect into an Ethernet switch.
p.38
Internet Protocol Stack and OSI Model
What is a message in the context of encapsulation?
The original data before it is encapsulated.
p.25
Internet Structure and ISPs
What is the purpose of access networks in the Internet structure?
To connect end users to the Internet.
p.22
Access Network Technologies: DSL and Cable
What is the role of access networks in the Internet structure?
They connect end users to the Internet.
p.32
Performance Metrics: Loss, Delay, Throughput
What does instantaneous throughput refer to?
The rate at a given point in time.
p.28
Performance Metrics: Loss, Delay, Throughput
What is the typical duration of nodal processing delay?
Typically less than 1 millisecond.
p.37
Internet Protocol Stack and OSI Model
What is the purpose of encapsulation in networking?
To wrap data with protocol information at each layer.
p.10
Access Network Technologies: DSL and Cable
What does CMTS stand for?
Cable Modem Termination System.
p.27
Performance Metrics: Loss, Delay, Throughput
What happens to packets if there are no free buffers in a router?
Arriving packets are dropped, resulting in loss.
p.31
Performance Metrics: Loss, Delay, Throughput
What is a buffer in networking?
A waiting area for packets before they are transmitted.
p.33
Performance Metrics: Loss, Delay, Throughput
What does R_s represent in the context of throughput?
R_s represents the source throughput in bits per second.
p.3
Overview of the Internet
What does bandwidth refer to?
The transmission rate of communication links.
p.10
Access Network Technologies: DSL and Cable
How do homes connect to the ISP router in a cable network?
Through a network of cable and fiber.
p.15
Packet Switching vs. Circuit Switching
What is queuing delay in packet switching?
The time packets spend waiting in a queue before being transmitted.
p.30
Performance Metrics: Loss, Delay, Throughput
What happens when La/R > 1?
Average queueing delay becomes large, and more work is arriving than can be serviced.
p.26
Internet Structure and ISPs
What types of ISPs connect to Tier-1 ISPs?
Regional ISPs and access ISPs.
p.35
Internet Protocol Stack and OSI Model
What does the link layer handle?
Data transfer between neighboring network elements.
p.13
Packet Switching vs. Circuit Switching
What does the host do with the application message?
It breaks it into smaller chunks known as packets.
p.2
Packet Switching vs. Circuit Switching
What is the difference between packet switching and circuit switching?
Packet switching divides data into packets for transmission, while circuit switching establishes a dedicated communication path.
p.10
Access Network Technologies: DSL and Cable
What technology is used for TV transmission over a shared cable distribution network?
Different frequencies transmitted over a cable modem splitter.
p.11
Access Network Technologies: DSL and Cable
What are the common transmission rates for Ethernet?
10 Mbps, 100 Mbps, 1 Gbps, and 10 Gbps.
p.17
Packet Switching vs. Circuit Switching
Where is circuit switching commonly used?
In traditional telephone networks.
p.26
Internet Structure and ISPs
What are Tier-1 commercial ISPs?
Well-connected large networks that provide national and international coverage.
What do protocols control in the Internet?
The sending and receiving of messages.
p.3
Overview of the Internet
What types of communication links are used in the Internet?
Fiber, copper, radio, and satellite.
p.31
Performance Metrics: Loss, Delay, Throughput
What is packet loss?
The phenomenon where packets are dropped when arriving at a full queue.
Name an example of an Internet protocol.
TCP, IP, HTTP, Skype, or 802.11.
p.26
Internet Structure and ISPs
What role does Google play in the Internet structure?
It operates as a content provider network.
p.26
Internet Structure and ISPs
What is the function of an Internet Exchange Point (IXP)?
To facilitate the exchange of Internet traffic between different networks.
p.3
Overview of the Internet
What devices can connect to the Internet?
Smartphones, PCs, servers, laptops, and mobile networks.
p.35
Internet Protocol Stack and OSI Model
What are some examples of protocols in the link layer?
Ethernet, 802.11 (WiFi), and PPP.
p.8
Performance Metrics: Loss, Delay, Throughput
What is the typical downstream transmission rate for DSL?
Typically less than 10 Mbps, with a maximum of < 24 Mbps.
p.17
Packet Switching vs. Circuit Switching
What happens to circuit segments in circuit switching when not in use?
They remain idle and are not shared with other calls.
p.17
Packet Switching vs. Circuit Switching
In a circuit-switched network diagram, how many circuits does each link have?
Each link has four circuits.
p.17
Packet Switching vs. Circuit Switching
What type of performance does circuit switching provide?
Guaranteed performance, similar to a dedicated circuit.
p.9
Access Network Technologies: DSL and Cable
What is the function of a cable headend in a cable network?
It serves as the central point for receiving and distributing cable signals.
p.36
Internet Protocol Stack and OSI Model
If presentation and session services are needed, where must they be implemented in the Internet stack?
In the application layer.
p.39
Network Edge and Access Networks
What are the three main components of a network?
Network edge, core, and access network.
p.18
Internet Structure and ISPs
What drives the evolution of the Internet's complex structure?
Economics and national policies.
p.37
Internet Protocol Stack and OSI Model
What is a frame in networking?
A unit of data at the Link layer.
p.38
Internet Protocol Stack and OSI Model
What is a datagram?
The encapsulated segment at the network layer.
p.39
Performance Metrics: Loss, Delay, Throughput
What aspects of performance are discussed in networking?
Loss, delay, and throughput.
p.4
Internet Structure and ISPs
What organization is responsible for Internet standards?
IETF (Internet Engineering Task Force).
p.35
Internet Protocol Stack and OSI Model
Which protocols are used in the network layer?
IP and routing protocols.
p.29
Performance Metrics: Loss, Delay, Throughput
What is the formula for transmission delay (d trans)?
d trans = L/R, where L is packet length in bits and R is link bandwidth in bps.
p.29
Performance Metrics: Loss, Delay, Throughput
What is the formula for propagation delay (d prop)?
d prop = d / s, where d is the length of the physical link and s is the propagation speed (~2x10^8 m/sec).
p.31
Performance Metrics: Loss, Delay, Throughput
What happens when a packet arrives at a full queue?
The packet is dropped (aka lost).
What is an example of a human protocol?
Greeting someone with 'Hi' or asking for the time.
p.25
Internet Structure and ISPs
What role do content provider networks play in the Internet structure?
They bring services and content close to end users.
p.5
Overview of the Internet
How is the Internet's service options analogous?
It is analogous to postal service.
p.31
Performance Metrics: Loss, Delay, Throughput
What is the capacity of the queue (buffer) preceding a link?
The queue has finite capacity.
p.28
Performance Metrics: Loss, Delay, Throughput
What is queueing delay (d queue)?
The time a packet spends waiting at the output link for transmission, depending on the router's congestion level.
p.16
Routing and Forwarding in Networks
What does routing determine in a network?
The source-destination route taken by packets.
p.14
Packet Switching vs. Circuit Switching
What is the store-and-forward mechanism in packet switching?
The entire packet must arrive at the router before it can be transmitted on the next link.
p.27
Performance Metrics: Loss, Delay, Throughput
What contributes to the delay experienced by packets in a router?
The time spent in queues waiting for transmission.
p.33
Performance Metrics: Loss, Delay, Throughput
What does R_c represent in the context of throughput?
R_c represents the capacity of the bottleneck link in bits per second.
p.33
Performance Metrics: Loss, Delay, Throughput
What is the average end-to-end throughput when R_s is less than R_c?
The average end-to-end throughput is R_s bits/sec.
p.36
Internet Protocol Stack and OSI Model
What is the role of the presentation layer in the OSI model?
It allows applications to interpret the meaning of data, including encryption and compression.
p.21
Internet Structure and ISPs
What is the purpose of connecting each access ISP to a global transit ISP?
To facilitate global Internet connectivity.
p.18
Internet Structure and ISPs
Why must access ISPs be interconnected?
So that any two hosts can send packets to each other.
p.37
Internet Protocol Stack and OSI Model
What is a datagram?
A unit of data at the Network layer.
p.15
Packet Switching vs. Circuit Switching
What can occur if the memory (buffer) fills up due to excessive packet arrival?
Packets can be dropped (lost).
What does the command 'Get http://www.awl.com/kurose-ross <file>' represent?
A request to retrieve a file from a web server using HTTP.
p.39
Packet Switching vs. Circuit Switching
What is the difference between packet-switching and circuit-switching?
Packet-switching divides data into packets for transmission, while circuit-switching establishes a dedicated communication path.
p.23
Internet Structure and ISPs
What happens if one global ISP is viable?
There will be competitors that must be interconnected.
p.35
Internet Protocol Stack and OSI Model
What is the main function of the network layer?
Routing of datagrams from source to destination.
p.30
Performance Metrics: Loss, Delay, Throughput
What does La/R > 1 imply about average delay?
Average delay becomes infinite.
p.37
Internet Protocol Stack and OSI Model
What are the layers of the Internet Protocol Stack?
Application, Transport, Network, Link, Physical.
p.25
Internet Structure and ISPs
Name some examples of content provider networks.
Google, Microsoft, Akamai.
p.36
Internet Protocol Stack and OSI Model
What is a notable difference between the OSI model and the Internet stack?
The Internet stack is missing the presentation and session layers.
What does TCP stand for?
Transmission Control Protocol.
p.38
Internet Protocol Stack and OSI Model
What analogy is used to explain encapsulation?
Matryoshka dolls (stacking dolls).
p.37
Internet Protocol Stack and OSI Model
What is a segment in networking?
A unit of data at the Transport layer.
p.23
Internet Structure and ISPs
What is the purpose of an IXP?
To interconnect different ISPs.
p.16
Routing and Forwarding in Networks
What is a local forwarding table?
A table used by routers to make forwarding decisions based on header values.
p.30
Performance Metrics: Loss, Delay, Throughput
What is the formula for traffic intensity?
Traffic intensity = La/R.
p.30
Performance Metrics: Loss, Delay, Throughput
What does La/R ~ 0 indicate about average queueing delay?
It indicates a small average queueing delay.
p.33
Performance Metrics: Loss, Delay, Throughput
What is the average end-to-end throughput when R_s is greater than R_c?
The average end-to-end throughput is constrained by the bottleneck link, which is R_c bits/sec.
p.39
Overview of the Internet
What will follow after the overview of networking?
More depth and detail on the topics covered.
p.29
Performance Metrics: Loss, Delay, Throughput
What are the four sources of packet delay?
Transmission delay, propagation delay, processing delay, and queueing delay.
p.8
Access Network Technologies: DSL and Cable
Where does voice over a DSL phone line go?
To the telephone network.
p.11
Access Network Technologies: DSL and Cable
What type of networks are typically used in companies and universities?
Enterprise access networks (Ethernet).
p.3
Overview of the Internet
What is the 'nuts and bolts' view of the Internet?
It refers to the billions of connected computing devices and their components.
p.13
Network Edge and Access Networks
What is the link transmission rate also known as?
Link capacity or link bandwidth.
What is a service model in networking?
A framework that defines how services are provided to users over a network.
What is a protocol in networking?
A set of rules that govern data communication.
What is the purpose of a TCP connection?
To establish a reliable communication channel between computers.
p.26
Internet Structure and ISPs
Can you name some examples of Tier-1 ISPs?
Level 3, Sprint, AT&T, NTT.
p.10
Access Network Technologies: DSL and Cable
How does cable access differ from DSL?
Cable shares access to the cable headend, while DSL has dedicated access to a central office.
p.33
Performance Metrics: Loss, Delay, Throughput
What is a bottleneck link?
A link on the end-to-end path that constrains end-to-end throughput.
p.8
Access Network Technologies: DSL and Cable
What is the role of the central office in a DSL network?
It connects the DSL line to the DSLAM and the Internet.
p.8
Performance Metrics: Loss, Delay, Throughput
What is the typical upstream transmission rate for DSL?
Typically less than 1 Mbps, with a maximum of < 2.5 Mbps.
p.26
Internet Structure and ISPs
What is a content provider network?
A private network that connects data centers to the Internet, often bypassing Tier-1 and regional ISPs.
p.39
Overview of the Internet
What is the purpose of service models in networking?
To define how services are provided and consumed in a network.
p.8
Access Network Technologies: DSL and Cable
How are voice and data transmitted over a DSL line?
At different frequencies over a dedicated line to the central office.
p.11
Access Network Technologies: DSL and Cable
What role does an institutional router play in an Ethernet network?
It connects the institutional link to the ISP (Internet).
p.10
Access Network Technologies: DSL and Cable
What are the downstream and upstream transmission rates for cable networks?
Up to 30 Mbps downstream and 2 Mbps upstream.
p.35
Internet Protocol Stack and OSI Model
What is the purpose of the application layer in the Internet protocol stack?
Supporting network applications like FTP, SMTP, and HTTP.
p.16
Routing and Forwarding in Networks
What information does the header value in a packet provide?
The destination address in the arriving packet's header.
p.3
Overview of the Internet
What is the role of packet switches in the Internet?
They forward packets, which are chunks of data.
p.4
Overview of the Internet
What are the different types of networks mentioned in the 'nuts and bolts' view of the Internet?
Mobile network, global ISP, regional ISP, home network, institutional network.
p.15
Packet Switching vs. Circuit Switching
What is packet loss in the context of packet switching?
The situation where packets are dropped due to buffer overflow.
p.14
Packet Switching vs. Circuit Switching
What is the formula for end-to-end delay assuming zero propagation delay?
End-to-end delay = 2L / R.
p.8
Access Network Technologies: DSL and Cable
How does data over a DSL phone line reach the Internet?
It goes to the central office DSLAM.
p.11
Access Network Technologies: DSL and Cable
What devices are commonly found in an Ethernet network setup?
Ethernet switch, institutional mail, web servers, and institutional router.
p.3
Overview of the Internet
What types of networks can be part of the Internet?
Global ISPs, regional ISPs, home networks, and institutional networks.
p.30
Performance Metrics: Loss, Delay, Throughput
What is the significance of La/R in queuing theory?
It helps determine the average queueing delay based on traffic intensity.
p.29
Performance Metrics: Loss, Delay, Throughput
What does propagation delay (d prop) depend on?
It depends on the length of the physical link (d) and the propagation speed (s).
p.38
Internet Protocol Stack and OSI Model
What is a frame in networking?
The encapsulated datagram at the data link layer.
p.39
Internet Protocol Stack and OSI Model
What does layering refer to in networking?
The organization of network protocols in layers to simplify communication.
p.8
Access Network Technologies: DSL and Cable
What device is used to manage voice and data transmission in a DSL network?
DSLAM (Digital Subscriber Line Access Multiplexer).
p.29
Performance Metrics: Loss, Delay, Throughput
What is the equation for total nodal delay (d nodal)?
d nodal = d proc + d queue + d trans + d prop.
