Computer Networking: Chapter 1 Introduction and Overview

Comprehensive flashcards covering introductory computer networking topics from Kurose & Ross Chapter 1, including network edge and core, switching mechanisms, delay components, throughput, protocol layering, security, and Internet history.

What is the minimum class attendance requirement specified for the course?

$$\ge 75\%$$

What policy applies to assignments that are plagiarized, copied, or submitted late?

Copied and late submissions are not allowed, and plagiarized or copied assignments will receive negative marks.

From a "nuts and bolts" perspective, what are the primary physical and logical components that constitute the Internet?

Hosts (end systems running network applications), communication links (fiber, copper, radio, satellite), and packet switches (routers and switches).

What is the definition of a network protocol?

A protocol defines the format and order of messages sent and received among network entities, as well as the actions taken on message transmission or receipt.

What do the acronyms RFC and IETF stand for in the context of Internet standards?

RFC stands for Request for Comments, and IETF stands for Internet Engineering Task Force.

What is the "service view" definition of the Internet?

An infrastructure that provides services to applications (such as Web, VoIP, email, games, and e-commerce) and provides a programming interface (API) with service options to apps.

In a Digital Subscriber Line (DSL) access network, what device at the telco central office splits voice and data signals?

The DSLAM (DSL access multiplexer).

What are the typical upstream and downstream transmission rates for DSL as cited in the lecture?

Upstream transmission rate is $< 2.5\,\text{Mbps}$ (typically $< 1\,\text{Mbps}$), and downstream transmission rate is $< 24\,\text{Mbps}$ (typically $< 10\,\text{Mbps}$).

What does the abbreviation HFC stand for in cable access networks?

Hybrid fiber coax

What key architectural difference exists between DSL and cable network access regarding line sharing?

DSL provides a dedicated line from the home to the central office, whereas cable networks use a shared access network where homes share bandwidth to the cable headend (CMTS).

What are the transmission rates supported by 802.11b/g (WiFi) wireless LANs?

$11\,\text{Mbps}$ and $54\,\text{Mbps}$

What transmission standards and speeds are associated with Category 5 and Category 6 twisted pair copper cabling?

Category 5 supports $100\,\text{Mbps}$ and $1\,\text{Gbps}$ Ethernet, while Category 6 supports $10\,\text{Gbps}$.

What is the typical end-to-end propagation delay reported for satellite radio transmission links?

$$270\,\text{msec}$$

What formula defines packet transmission delay ($d_{\text{trans}}$) for a packet of length $L$ bits over a link with transmission rate $R$ bps?

$$d_{\text{trans}} = \frac{L}{R}$$

What are the four components that constitute total nodal delay ($d_{\text{nodal}}$)?

Nodal processing delay ($d_{\text{proc}}$), queueing delay ($d_{\text{queue}}$), transmission delay ($d_{\text{trans}}$), and propagation delay ($d_{\text{prop}}$).

What formula determines propagation delay ($d_{\text{prop}}$), and what is the typical propagation speed ($s$) in physical media?

$d_{\text{prop}} = \frac{d}{s}$, where $s \approx 2 \times 10^8\,\text{m/s}$.

If a packet length is $L = 7.5\,\text{Mbits}$ and the link transmission rate is $R = 1.5\,\text{Mbps}$, what is the transmission delay on a single hop?

$5\,\text{seconds}$ (computed as $\frac{7.5\,\text{Mbits}}{1.5\,\text{Mbps}}$).

What mathematical expression defines traffic intensity, where $L$ is packet length, $a$ is average arrival rate, and $R$ is link bandwidth?

$$\frac{La}{R}$$

What behavior of queueing delay is depicted in this graph as traffic intensity approaches 1?

The average queueing delay increases exponentially, becoming very large as $\frac{La}{R} \rightarrow 1$ and tending toward infinity when $\frac{La}{R} > 1$.

How does the traceroute diagnostic program measure end-to-end delays along an Internet path?

It sends three probe packets towards each successive router $i$ on the path, and measures the elapsed round-trip time between transmission and each router's reply.

What defines the bottleneck link in an end-to-end network transmission path?

The specific link on the end-to-end path that has the lowest transmission rate, thereby constraining the overall end-to-end throughput.

What are the two primary core functions of the network layer?

Routing (determining the end-to-end route taken by packets using routing algorithms) and forwarding (moving packets from a router's input port to the appropriate output port).

What is the store-and-forward mechanism implemented in packet switches?

The router must receive the entire packet completely before it can begin transmitting any part of that packet onto the outgoing link.

Under what specific conditions does packet loss (dropping) occur at a router?

When the arrival rate to a link exceeds the link transmission rate for a duration long enough that the finite router memory buffer fills up completely.

What are the two common multiplexing techniques used to partition circuit resources in circuit switching?

Frequency Division Multiplexing (FDM) and Time Division Multiplexing (TDM).

If a circuit-switched link has a capacity of $1\,\text{Mbps}$ and each user transmits at $100\,\text{kb/s}$ when active, how many users can be simultaneously supported?

$$10\,\text{users}$$

What is an Internet Exchange Point (IXP)?

A dedicated physical switching hub where multiple commercial, regional, or content networks interconnect directly via peering agreements.

What defines a Tier-1 commercial ISP in the Internet hierarchy?

A large backbone provider with national or international coverage that can reach every network in the Internet without paying transit fees to other networks.

How do private content provider networks (such as Google or Microsoft) bypass traditional ISP hierarchies?

They operate their own private high-speed networks connecting their data centers directly to exchange points or lower-tier ISPs, bypassing Tier-1 providers to reduce costs and latency.

Which 5 layers comprise the Internet protocol stack shown in the diagram?

Application, Transport, Network, Link, and Physical.

Which two additional protocol layers are present in the 7-layer ISO/OSI reference model compared to the 5-layer Internet stack?

The Presentation layer and the Session layer.

What are the responsibilities of the Presentation layer in the ISO/OSI model?

Allowing applications to interpret data syntax and semantics through services such as data encryption, compression, and machine-specific representation conventions.

What specific names are given to the packet data units at the Application, Transport, Network, and Link layers during encapsulation?

Application: message ($M$); Transport: segment ($H_t, M$); Network: datagram ($H_n, H_t, M$); Link: frame ($H_l, H_n, H_t, M$).

What are the two major advantages of employing layered architecture in network design?

Explicit structure allows identification of relationships among complex components, and modularity makes updates and maintenance transparent to other layers.

What distinguishes a network virus from a network worm?

A virus is a self-replicating infection requiring active execution of an infected object (e.g., email attachment), while a worm self-replicates and executes automatically upon passive receipt.

What is IP spoofing?

An attack technique where a malicious host transmits packets bearing a fraudulent or forged source IP address.

What mechanism enables packet sniffing on broadcast media, and what tool was highlighted for lab use?

Putting the network interface card into promiscuous mode to read and record all passing traffic; the tool highlighted is Wireshark.

Which researcher demonstrated the fundamental effectiveness of packet-switching using queueing theory in 1961?

Leonard Kleinrock

What are the four architectural principles for interconnecting networks introduced by Vinton Cerf and Robert Kahn in 1974?

Minimalism and autonomy (no internal changes required to connect networks), best-effort service model, stateless routers, and decentralized control.

Which early computer network is shown in this historic diagram depicting four original university and research nodes?

The ARPA Network (ARPAnet), featuring original nodes at UCLA, SRI, UCSB, and UTAH.