What is the Internet primarily viewed as?
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A service infrastructure that provides services to applications.
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What is the Internet primarily viewed as?
A service infrastructure that provides services to applications.
What components make up the network edge?
Hosts, access networks, and physical media.
What does ISP stand for?
Internet Service Provider.
What is the primary focus of Lecture 1 in the Computer Networks course?
An introduction to Computer Networks and the Internet.
What does ISP stand for?
Internet Service Provider.
What is circuit switching?
A method where end-to-end resources are allocated and reserved for a call between source and destination.
What is the Internet structure described as?
A network of networks.
What is the Internet structure described as?
A network of networks.
What is throughput in networking?
The rate (bits/time unit) at which bits are transferred between sender and receiver.
What is the typical range of wireless LANs within a building?
Approximately 100 feet.
Where can textbook resources for the course be found?
What is the Internet described as?
A network of networks.
What is the Internet structure described as?
A network of networks.
What is a protocol?
A set of rules that govern the communication between devices on a network.
What connects end systems to routers in a shared wireless access network?
A base station, also known as an access point.
What types of services does the Internet provide?
Web, VoIP, email, games, e-commerce, social networks, etc.
What is the Internet structure described as?
A network of networks.
What does the Internet provide to applications?
A programming interface with hooks for sending and receiving app programs.
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.
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.
What is the Internet described as?
A network of networks.
What does ISP stand for?
Internet Service Provider.
What is the role of access ISPs?
To connect users to the Internet.
What is the course code for the Computer Networks class?
SEHS3321.
What is an IXP?
Internet Exchange Point.
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.
What are the four sources of packet delay?
Nodal processing, queueing delay, transmission delay, and propagation delay.
What does nodal processing delay (d proc) involve?
Checking bit errors and determining the output link.
What device is used to split signals in a cable network?
Splitter.
What does average throughput refer to?
The rate over a longer period of time.
What are protocol layers?
Hierarchical layers that define how data is transmitted and received over a network.
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.
What does 'R' represent in the context of throughput?
The rate of the backbone bottleneck link in bits/sec.
What is the typical speed range for wide-area wireless access?
Between 1 and 10 Mbps.
What happens when the arrival rate to a link exceeds its transmission rate?
Packets will queue and wait to be transmitted on the link.
What is the Internet?
A global network of interconnected computers that communicate using standardized protocols.
What is the economic relationship between customer and provider ISPs?
They have an economic agreement.
What does ISP stand for?
Internet Service Provider.
What happens if one global ISP is a viable business?
There will be competitors.
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.
Who provides wide-area wireless access?
Telecommunications (telco) operators.
What is the main focus of the material covered?
An overview of the Internet and networking concepts.
Who may retransmit a lost packet?
The previous node, the source end system, or it may not be retransmitted at all.
How are different channels transmitted in frequency division multiplexing?
In different frequency bands.
What is a peering link?
A connection between ISPs for exchanging traffic.
What is a segment in networking?
The encapsulated message at the transport layer.
What is a key challenge in connecting millions of access ISPs?
Determining how to connect them together.
What is the Internet often described as?
A network of networks.
How do regional networks relate to access networks?
They connect access networks to 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.
How do end systems connect to the Internet?
Via access ISPs (Internet Service Providers).
What is the primary function of forwarding in a network?
To move packets from a router's input to the appropriate router output.
What is one reason for delay in packet transmission?
Packets queuing in router buffers while waiting for their turn to be transmitted.
What types of ISPs are mentioned?
Residential, company, and university ISPs.
What is the formula for total nodal delay?
d nodal = d proc + d queue + d trans + d prop.
What are hosts in the context of the Internet?
Hosts are end systems running network applications.
How is packet transmission delay calculated?
Time needed to transmit an L-bit packet into the link is L (bits) / R (bits/sec).
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.
What governs all communication activity on the Internet?
Protocols.
What are the key performance metrics in networking?
Loss, delay, and throughput.
What functions does the session layer provide?
Synchronization, checkpointing, and recovery of data exchange.
What is encapsulation in networking?
The process of wrapping data with protocol information at each layer of the OSI model.
What types of networks are part of the Internet infrastructure?
Mobile network, global ISP, regional ISP, home network, institutional network.
What technology allows different channels to be transmitted in a cable network?
Frequency division multiplexing.
How do end systems typically connect in an Ethernet network?
They connect into an Ethernet switch.
What is a message in the context of encapsulation?
The original data before it is encapsulated.
What is the purpose of access networks in the Internet structure?
To connect end users to the Internet.
What is the role of access networks in the Internet structure?
They connect end users to the Internet.
What does instantaneous throughput refer to?
The rate at a given point in time.
What is the typical duration of nodal processing delay?
Typically less than 1 millisecond.
What is the purpose of encapsulation in networking?
To wrap data with protocol information at each layer.
What does CMTS stand for?
Cable Modem Termination System.
What is an IXP?
Internet Exchange Point.
What happens to packets if there are no free buffers in a router?
Arriving packets are dropped, resulting in loss.
What is a buffer in networking?
A waiting area for packets before they are transmitted.
What is HFC in the context of cable networks?
Hybrid Fiber Coax.
What does R_s represent in the context of throughput?
R_s represents the source throughput in bits per second.
What does bandwidth refer to?
The transmission rate of communication links.
How do homes connect to the ISP router in a cable network?
Through a network of cable and fiber.
What is queuing delay in packet switching?
The time packets spend waiting in a queue before being transmitted.
What happens when La/R > 1?
Average queueing delay becomes large, and more work is arriving than can be serviced.
What types of ISPs connect to Tier-1 ISPs?
Regional ISPs and access ISPs.
What does the link layer handle?
Data transfer between neighboring network elements.
What does the host do with the application message?
It breaks it into smaller chunks known as packets.
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.
What is the length of each packet referred to in the text?
L bits.
What is the Internet described as?
A network of networks.
What technology is used for TV transmission over a shared cable distribution network?
Different frequencies transmitted over a cable modem splitter.
What are the common transmission rates for Ethernet?
10 Mbps, 100 Mbps, 1 Gbps, and 10 Gbps.
Where is circuit switching commonly used?
In traditional telephone networks.
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.
What does 'R' represent in the context of network traffic?
Link bandwidth (bps).
What types of communication links are used in the Internet?
Fiber, copper, radio, and satellite.
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.
What types of data can be transmitted through a cable network?
Video and data.
In a one-hop numerical example, what is the size of the packet (L)?
7.5 Mbits.
What role does Google play in the Internet structure?
It operates as a content provider network.
In a one-hop numerical example, what is the transmission rate (R)?
1.5 Mbps.
What is the function of an Internet Exchange Point (IXP)?
To facilitate the exchange of Internet traffic between different networks.
What devices can connect to the Internet?
Smartphones, PCs, servers, laptops, and mobile networks.
What are some examples of protocols in the link layer?
Ethernet, 802.11 (WiFi), and PPP.
What is the typical downstream transmission rate for DSL?
Typically less than 10 Mbps, with a maximum of < 24 Mbps.
What happens to circuit segments in circuit switching when not in use?
They remain idle and are not shared with other calls.
What is the primary component used in a cable network for internet access?
Cable modem.
In a circuit-switched network diagram, how many circuits does each link have?
Each link has four circuits.
What are the transmission rates for 802.11b/g/n (WiFi)?
11, 54, and 450 Mbps.
What type of performance does circuit switching provide?
Guaranteed performance, similar to a dedicated circuit.
What is the function of a cable headend in a cable network?
It serves as the central point for receiving and distributing cable signals.
What is an IXP?
Internet Exchange Point.
If presentation and session services are needed, where must they be implemented in the Internet stack?
In the application layer.
What are the three main components of a network?
Network edge, core, and access network.
What drives the evolution of the Internet's complex structure?
Economics and national policies.
What is a frame in networking?
A unit of data at the Link layer.
What is a datagram?
The encapsulated segment at the network layer.
What aspects of performance are discussed in networking?
Loss, delay, and throughput.
What organization is responsible for Internet standards?
IETF (Internet Engineering Task Force).
What devices operate at the Link layer?
Switches.
Which protocols are used in the network layer?
IP and routing protocols.
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.
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).
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.
What role do content provider networks play in the Internet structure?
They bring services and content close to end users.
How is the Internet's service options analogous?
It is analogous to postal service.
What is the capacity of the queue (buffer) preceding a link?
The queue has finite capacity.
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.
What is the Internet often referred to as?
A 'network of networks'.
What does routing determine in a network?
The source-destination route taken by packets.
In practice, what is often the bottleneck in a connection scenario?
Rc or Rs.
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.
What contributes to the delay experienced by packets in a router?
The time spent in queues waiting for transmission.
What does 'L' stand for in network traffic analysis?
Packet length (bits).
What does R_c represent in the context of throughput?
R_c represents the capacity of the bottleneck link in bits per second.
What does RFC stand for?
Request for Comments.
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.
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.
What is the purpose of connecting each access ISP to a global transit ISP?
To facilitate global Internet connectivity.
What is the transmission rate at which packets are sent into the access network?
R bits per second.
What is the Internet structure described as?
A network of networks.
Why must access ISPs be interconnected?
So that any two hosts can send packets to each other.
What technologies are associated with wide-area wireless access?
3G, 4G, and LTE.
What is a datagram?
A unit of data at the Network layer.
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 ' represent?
A request to retrieve a file from a web server using HTTP.
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.
What happens if one global ISP is viable?
There will be competitors that must be interconnected.
What is the main function of the network layer?
Routing of datagrams from source to destination.
What does La/R > 1 imply about average delay?
Average delay becomes infinite.
What are the layers of the Internet Protocol Stack?
Application, Transport, Network, Link, Physical.
What is the formula for per-connection end-to-end throughput in a scenario with 10 connections sharing a backbone link?
min(Rc, Rs, R/10)
Name some examples of content provider networks.
Google, Microsoft, Akamai.
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.
What analogy is used to explain encapsulation?
Matryoshka dolls (stacking dolls).
What is a segment in networking?
A unit of data at the Transport layer.
What is the purpose of an IXP?
To interconnect different ISPs.
What is a local forwarding table?
A table used by routers to make forwarding decisions based on header values.
What is the transmission rate of link A?
100 Mb/s.
What is the formula for traffic intensity?
Traffic intensity = La/R.
What is the transmission rate of link B?
1.5 Mb/s.
What does La/R ~ 0 indicate about average queueing delay?
It indicates a small average queueing delay.
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.
What is the one-hop transmission delay in the given example?
5 seconds.
What will follow after the overview of networking?
More depth and detail on the topics covered.
What does the physical layer represent?
Bits 'on the wire'.
What are the four sources of packet delay?
Transmission delay, propagation delay, processing delay, and queueing delay.
Where does voice over a DSL phone line go?
To the telephone network.
What type of networks are typically used in companies and universities?
Enterprise access networks (Ethernet).
What is the 'nuts and bolts' view of the Internet?
It refers to the billions of connected computing devices and their components.
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.
Can you name some examples of Tier-1 ISPs?
Level 3, Sprint, AT&T, NTT.
How does cable access differ from DSL?
Cable shares access to the cable headend, while DSL has dedicated access to a central office.
What are examples of packet switches?
Routers and switches.
What is a bottleneck link?
A link on the end-to-end path that constrains end-to-end throughput.
What is the role of the central office in a DSL network?
It connects the DSL line to the DSLAM and the Internet.
What is the typical upstream transmission rate for DSL?
Typically less than 1 Mbps, with a maximum of < 2.5 Mbps.
How many connections are sharing the backbone bottleneck link in the given scenario?
10 connections.
How long does it take to transmit an L-bit packet into a link at R bps?
It takes L / R seconds.
What is a content provider network?
A private network that connects data centers to the Internet, often bypassing Tier-1 and regional ISPs.
What devices operate at the Network layer?
Routers.
What is the purpose of service models in networking?
To define how services are provided and consumed in a network.
How are voice and data transmitted over a DSL line?
At different frequencies over a dedicated line to the central office.
What role does an institutional router play in an Ethernet network?
It connects the institutional link to the ISP (Internet).
What are the downstream and upstream transmission rates for cable networks?
Up to 30 Mbps downstream and 2 Mbps upstream.
What is the purpose of the application layer in the Internet protocol stack?
Supporting network applications like FTP, SMTP, and HTTP.
What information does the header value in a packet provide?
The destination address in the arriving packet's header.
What is the role of packet switches in the Internet?
They forward packets, which are chunks of data.
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.
What is packet loss in the context of packet switching?
The situation where packets are dropped due to buffer overflow.
What is the formula for end-to-end delay assuming zero propagation delay?
End-to-end delay = 2L / R.
How does data over a DSL phone line reach the Internet?
It goes to the central office DSLAM.
What devices are commonly found in an Ethernet network setup?
Ethernet switch, institutional mail, web servers, and institutional router.
What approach is suggested to describe the current Internet structure?
A stepwise approach.
What protocols are associated with the transport layer?
TCP and UDP.
What types of networks can be part of the Internet?
Global ISPs, regional ISPs, home networks, and institutional networks.
What is the significance of La/R in queuing theory?
It helps determine the average queueing delay based on traffic intensity.
What does propagation delay (d prop) depend on?
It depends on the length of the physical link (d) and the propagation speed (s).
What equipment is used to separate voice and data signals in a DSL setup?
DSL modem splitter.
What is a frame in networking?
The encapsulated datagram at the data link layer.
What does layering refer to in networking?
The organization of network protocols in layers to simplify communication.
What does DSL stand for?
Digital Subscriber Line.
What device is used to manage voice and data transmission in a DSL network?
DSLAM (Digital Subscriber Line Access Multiplexer).
What is the equation for total nodal delay (d nodal)?
d nodal = d proc + d queue + d trans + d prop.
