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Questions and Answers
In a ring topology, a break in the ring can disable the entire network.
In a ring topology, a break in the ring can disable the entire network.
True
A tree topology has multiple paths for data transmission between nodes.
A tree topology has multiple paths for data transmission between nodes.
False
A Personal Area Network (PAN) is designed for connecting devices over a broad geographical area.
A Personal Area Network (PAN) is designed for connecting devices over a broad geographical area.
False
The network core is composed solely of clients and servers.
The network core is composed solely of clients and servers.
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A local area network (LAN) connects computers within a limited area such as an office or university campus.
A local area network (LAN) connects computers within a limited area such as an office or university campus.
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Protocols only define the format of messages and not the order in which they are sent.
Protocols only define the format of messages and not the order in which they are sent.
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Wireless local area networks (WLANs) enable mobile access through technologies like WiFi.
Wireless local area networks (WLANs) enable mobile access through technologies like WiFi.
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A master device in a PAN serves as a gateway to connect to higher-level networks.
A master device in a PAN serves as a gateway to connect to higher-level networks.
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Wireless local area networks (WLANs) typically have a transmission range of approximately 100 miles.
Wireless local area networks (WLANs) typically have a transmission range of approximately 100 miles.
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A link's transmission delay is calculated using the formula Packet transmission delay = L/R, where L is the packet size in bits and R is the transmission rate.
A link's transmission delay is calculated using the formula Packet transmission delay = L/R, where L is the packet size in bits and R is the transmission rate.
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Guided media refers to signals that propagate freely through the air.
Guided media refers to signals that propagate freely through the air.
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The main concept of packet switching involves reserving end-to-end resources for a communication call between two parties.
The main concept of packet switching involves reserving end-to-end resources for a communication call between two parties.
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If the arrival rate to a link exceeds the transmission rate, packets may be queued or dropped in routers.
If the arrival rate to a link exceeds the transmission rate, packets may be queued or dropped in routers.
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Terrestrial microwave is a type of unguided media used for wireless communication.
Terrestrial microwave is a type of unguided media used for wireless communication.
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The network core is a mesh of interconnected routers responsible for forwarding packets.
The network core is a mesh of interconnected routers responsible for forwarding packets.
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Reflection and interference are examples of propagation effects for radio signals.
Reflection and interference are examples of propagation effects for radio signals.
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A server in the Client-Server paradigm has a dynamic IP address.
A server in the Client-Server paradigm has a dynamic IP address.
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In a Peer-to-Peer architecture, peers communicate directly with each other to provide services.
In a Peer-to-Peer architecture, peers communicate directly with each other to provide services.
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Inter-process communication can occur between processes running on different hosts without message exchange.
Inter-process communication can occur between processes running on different hosts without message exchange.
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Application-layer protocols define the types of messages and their syntax.
Application-layer protocols define the types of messages and their syntax.
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Transmission delay can be calculated using the formula $dtrans = L/R$ where $L$ is the packet length in bits and $R$ is the link transmission rate in bps.
Transmission delay can be calculated using the formula $dtrans = L/R$ where $L$ is the packet length in bits and $R$ is the link transmission rate in bps.
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All applications require 100% reliable data transfer regardless of their function.
All applications require 100% reliable data transfer regardless of their function.
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Propagation delay is higher when the length of the physical link decreases.
Propagation delay is higher when the length of the physical link decreases.
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Malware can enter a host through a virus that requires user interaction to activate.
Malware can enter a host through a virus that requires user interaction to activate.
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Proprietary protocols are defined in RFCs and are open for public access.
Proprietary protocols are defined in RFCs and are open for public access.
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Spyware malware is designed to enhance the performance of the computer by optimizing resource usage.
Spyware malware is designed to enhance the performance of the computer by optimizing resource usage.
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Transport services needed by applications include security measures such as encryption.
Transport services needed by applications include security measures such as encryption.
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Denial of Service (DoS) attacks work by making legitimate resources available to attackers.
Denial of Service (DoS) attacks work by making legitimate resources available to attackers.
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Modularization in systems improves their maintenance and updating capabilities.
Modularization in systems improves their maintenance and updating capabilities.
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IP spoofing involves sending packets with a legitimate source address.
IP spoofing involves sending packets with a legitimate source address.
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Queueing delay is not affected by the congestion level of a router.
Queueing delay is not affected by the congestion level of a router.
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The Internet protocol stack includes five layers, with the physical layer responsible for transmitting bits over a physical medium.
The Internet protocol stack includes five layers, with the physical layer responsible for transmitting bits over a physical medium.
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Web caching is primarily designed to involve the origin server in servicing client requests.
Web caching is primarily designed to involve the origin server in servicing client requests.
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HTTP/2 introduces the capability to send unrequested objects to the client.
HTTP/2 introduces the capability to send unrequested objects to the client.
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A conditional GET request will always result in an object transmission, regardless of the cache status.
A conditional GET request will always result in an object transmission, regardless of the cache status.
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Web caches can be positioned to reduce the distance between the server and the client.
Web caches can be positioned to reduce the distance between the server and the client.
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HTTP/1.1's object transmission is prioritized based on the size of the objects being sent.
HTTP/1.1's object transmission is prioritized based on the size of the objects being sent.
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TCP provides reliability, flow control, and congestion control.
TCP provides reliability, flow control, and congestion control.
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UDP guarantees the delivery of data packets between sender and receiver.
UDP guarantees the delivery of data packets between sender and receiver.
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In non-persistent HTTP, multiple objects require a single TCP connection.
In non-persistent HTTP, multiple objects require a single TCP connection.
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The HTTP HEAD method is used to download the entire content of a web page.
The HTTP HEAD method is used to download the entire content of a web page.
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A 404 Not Found status code indicates that the requested document exists on the server.
A 404 Not Found status code indicates that the requested document exists on the server.
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The POST method sends user input in the URL of the HTTP request message.
The POST method sends user input in the URL of the HTTP request message.
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Persistent HTTP allows multiple objects to be sent over a single TCP connection.
Persistent HTTP allows multiple objects to be sent over a single TCP connection.
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Cookies are used to store user preferences and session information in web applications.
Cookies are used to store user preferences and session information in web applications.
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Study Notes
Client and Server
- A client is any computer hardware or software that requests a service from a server.
- A server is a computer program or device that provides a service to another computer program or user.
Network Devices
- Switch: Connects network devices, responsible for directing data to the correct destination device.
- Router: Directs data packets to their intended destination.
Communication Types
- Simplex: One-way communication (e.g., television).
- Half-duplex: Two-way communication, but only one device can send data at a time (e.g., walkie-talkie).
- Full-duplex: Two-way communication where both devices can send data simultaneously (e.g., telephone).
Mesh Topology
- A fully connected mesh network.
- Formula for calculating the number of physical connections: [n(n-1)] / 2
- Disadvantages:
- Installation and reconfiguration are difficult.
- Requires more wiring than other topologies, potentially exceeding available space.
- Expensive hardware for connections.
Star Topology
- Advantages:
- Cheaper than a mesh topology.
- Easy to install.
- Easy to identify faults.
- Disadvantages:
- If the central controller fails, the entire network will go down.
- Needs more cables than a ring or tree topology.
Bus Topology
- One cable, the backbone, connects all devices.
- Devices connect to the main cable through drop lines and taps.
- Advantages:
- Easy to Install
- Requires less cable compared to a mesh, star and tree topology.
- Disadvantages:
- Difficult reconfiguration and fault isolation.
- A break in the cable disrupts transmission for all devices on the same side.
Ring Topology
- Each device is connected to its two neighboring devices only.
- Advantages:
- Relatively easy to install.
- Adding or deleting a device modifies two connections only.
- Disadvantages:
- A break in the ring disrupts transmission for all devices.
Tree Topology
- A central node (the trunk) with several branches.
- Each node connects to the central node through a single path.
PAN and LAN
- PAN (Personal Area Network): Connects personal devices (e.g., computers, smartphones, tablets)
- LAN (Local Area Network): Interconnects computers within a limited area (e.g., residence, school).
Internet from a Service View
- Infrastructure for web, video streaming, email, games, e-commerce, social media, and inter-connected appliances.
- Provides a programming interface to distribute applications.
Network Edge and Core
- Network Edge: Hosts (clients and servers), often in data centers.
- Network Core: Interconnected routers.
Packet Switching
- Hosts break application-layer messages into packets.
- Packets are forwarded from one router to the next, across links on the path to the destination.
- Each packet is transmitted at maximum link capacity.
Packet Queuing and Loss
- If packet arrival rate exceeds transmission rate, packets will queue.
- Packets can be dropped if the memory buffer fills up.
Circuit Switching
- End-to-end resources allocated to a call.
- Common in traditional telephone networks.
- Frequency Division Multiplexing (FDM): Divides electromagnetic frequencies into narrow bands for each call.
- Time Division Multiplexing (TDM): Divides time into slots for calls.
Modern Internet Structure
- Tier-1 ISPs (global transit ISPs) connect to each other.
- Regional ISPs connect to Tier-1 ISPs.
- Access ISPs connect to regional ISPs, providing access to end users.
- IXPs (Internet Exchange Points) are meeting points for ISPs to exchange traffic between networks.
Malware
- Viruses: Self-replicating infections.
- Worms: Self-replicating infections that actively spread.
- Spyware: Records keystrokes and visits websites, potentially uploading this data or enrolling the host in a botnet.
- Denial of Service (DoS): Overwhelms resources (servers, bandwidth).
Packet Delay
- Nodal Processing: Checking bits, determining the output link (<1 msec).
- Queuing Delay: Waiting at output link (depends on congestion level).
- Transmission Delay: Packet length (bits)/link transmission rate (bps).
- Propagation Delay: Distance/propagation speed (~2x10^8 m/s).
Throughput
- Rate of bits sent from sender to receiver.
- Can be instantaneous or average.
- In end-to-end throughput—the minimum rate among the links is the rate between end systems.
HTTP Connections
- Non-Persistent HTTP: Opens a new TCP connection for each object requested.
- Persistent HTTP: Uses a single TCP connection for multiple objects.
HTTP Response Time
- Non-persistent HTTP: 2 round-trip times (RTTs) + file transmission time.
HTTP Request Types
- GET: Retrieve data from URL.
- POST: Submit data to a server.
- PUT: Upload data to a specific URL.
- HEAD: Retrieve HTTP headers (only).
HTTP Response Codes
- Common codes like 200 OK, 301 Moved Permanently, 400 Bad Request, 404 Not Found, 505 HTTP Version Not Supported.
Cookies
- Web sites store state between transactions on clients via cookies
- Clients use cookies to maintain a state between transactions.
Web Caching
- Caching acts as both a client and server for the original request.
- Reduces response time for clients and reduces traffic on the institution’s access link.
Conditional GET
- Avoids unnecessary transmissions if the cached version is up-to-date.
HTTP/1.1 with Multiple Object Pipelining
- Introduces multiple pipelined GETs (First Come First Served),
- Possible head-of-line (HOL) blocking; objects behind large objects will have to wait.
HTTP/2 Goal
- Multi-object requests with decreased delay
- Flexible transmission of objects to mitigate HOL blocking. Objects transmitted in order based on priority.
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Description
Test your knowledge of networking concepts including clients, servers, common communication types, and network topologies such as mesh. This quiz covers fundamental principles that are essential for understanding how different network devices interact. Challenge yourself to see how well you grasp these key concepts!
