chap 1 + problems Flashcards
What is a computer network?
set of nodes connected by communication links, facilitating data exchange.
Key components:
* end devices (computers, printers),
* intermediary nodes (routers, switches),
* the communication links themselves (wired or wireless).
What are the types of data communication?
Simplex, half-duplex, full-duplex, multiplexing
**Simplex is
**one-way communication,
**half-duplex
**allows two-way communication but not simultaneously,
**full-duplex
**allows simultaneous two-way communication.
**Multiplexing:
**Combining multiple data streams into a single channel.
Describe the ‘nuts and bolts’ view of the Internet.
Focuses on hardware and infrastructure, like packet switches, communication links, and protocols.
It emphasizes the physical components that make up the Internet.
Describe the ‘services’ view of the Internet.
Emphasizes applications and services like the Web, streaming video, and email.
It includes the programming interfaces used to access these services.
What is a protocol in computer networks?
A set of rules governing how data is transmitted and received between devices on a network.
Protocols ensure effective communication and define the format, order, and actions during message exchange.
What are client hosts and server hosts?
Client hosts request services/resources; server hosts provide services/resources.
Example: A computer using a web browser is a client; a web server hosting websites is a server.
What is packet switching?
A method where data is divided into smaller packets, each routed independently to the destination.
It allows for more efficient use of network resources.
Explain the store-and-forward mechanism.
Requires each intermediate node to receive the entire packet before forwarding it to the next node.
This ensures that packets are completely received before they are passed on.
What is the difference between circuit switching and packet switching?
Circuit switching establishes a dedicated path for the entire session; packet switching shares network resources by sending data in packets.
Circuit switching is like a phone call, while packet switching is more efficient for bursty data.
List the four sources of packet delay.
Processing delay
* time it takes for a router or network device to process a packet upon receiving
queueing delay,
* time a packet spends waiting in a router’s output queue before being transmitted. The delay varies based on the number of packets in the queue and the rate at which packets are transmitted
transmission delay,
* time it takes to push all the bits of a packet into the link
propagation delay
* time it takes for a signal to travel from the source to the destination
Each type of delay affects the overall time it takes for a packet to reach its destination.
What is Bandwidth?
The maximum rate of data transfer across a network, typically measured in bits per second (bps).
What is a Bottleneck Link?
The link in a network path with the lowest capacity, limiting the overall throughput.
What is Circuit Switching?
A method of data transmission that establishes a dedicated communication path between two devices for the duration of the session.
What is a Client?
A device or application that requests services from a server.
What is Data Communication?
The exchange of data between two or more devices over a transmission medium.
What is Denial of Service (DoS)?
An attack that makes a resource unavailable to legitimate users by overwhelming it with bogus traffic.
What is Encryption?
The process of converting data into a coded form to prevent unauthorized access.
What is an End System (Host)?
A device connected to a network that runs applications for communication.
What is Full-Duplex?
A communication mode that allows simultaneous two-way data flow.
What is Half-Duplex?
A communication mode that allows two-way data flow, but not simultaneously.
What is the Internet?
A global network of interconnected computer networks using standardized communication protocols.
What is an Internet Service Provider (ISP)?
An organization that provides internet access to end users and businesses.
What is Latency (Delay)?
The time it takes for data to travel from source to destination across a network.
What is a Local Area Network (LAN)?
A network that connects devices within a limited geographical area.
What is a Metropolitan Area Network (MAN)?
A network that spans a metropolitan area, typically covering a city or large campus.
What is the Network Core?
The central part of a computer network that facilitates high-speed data transfer between networks.
What is the Network Edge?
The boundary of a computer network where end-user devices connect.
What is a Packet?
A small unit of data transmitted over a network.
What is a Protocol Stack?
A layered set of protocols used for network communication, with each layer responsible for specific functions.
What is a Router?
A networking device that forwards data packets between different networks.
What is Scalability?
The ability of a network to grow and adapt to increasing demands.
What is Security?
Protecting data, systems, and users from unauthorized access, damage, or disruptions.
What is a Server?
A device or application that provides services to clients.
What is Simplex?
A communication mode that allows one-way data flow.
What is a Switch?
A networking device that connects multiple devices within a network, forwarding data to specific destinations.
What is Throughput?
The rate of successful data transmission over a network, measured in bits per second (bps).
What is Topology?
The arrangement of network elements (links, nodes) in a computer network.
What is a Wide Area Network (WAN)?
A network that connects multiple LANs over a broader geographical area.
What is a protocol stack?
A protocol stack is organized into layers, with each layer responsible for specific functions related to communication between devices.
What are the two commonly known models for protocol stacks?
The two commonly known models are the OSI (Open Systems Interconnection) model and the TCP/IP model.
What does the Physical Layer (Layer 1) deal with?
The Physical Layer deals with the physical connection between devices and specifies the electrical and mechanical characteristics of transmission.
What is the responsibility of the Data Link Layer (Layer 2)?
reliable transmission of data frames between directly connected nodes over a physical link.
What protocols operate at the Data Link Layer?
Ethernet and Wi-Fi operate at the Data Link Layer.
What does the Network Layer (Layer 3) handle?
logical addressing, routing, and forwarding of data between devices across different networks.
Which protocol is key at the Network Layer?
IP (Internet Protocol) is a key protocol at the Network Layer.
What is the function of the Transport Layer (Layer 4)?
provides end-to-end communication between devices on different hosts, ensuring reliable and orderly data transfer.
Which protocols operate at the Transport Layer?
TCP (Transmission Control Protocol) and UDP (User Datagram Protocol) operate at the Transport Layer.
What does the Session Layer (Layer 5) manage?
establishes, manages, and terminates sessions between applications.
What is the role of the Presentation Layer (Layer 6)?
- data translation
- encryption
- compression.
What does the Application Layer (Layer 7) provide?
provides network services directly to end-users or applications.
What are some protocols included in the Application Layer?
Protocols for tasks such as email (SMTP), file transfer (FTP), and web browsing (HTTP) are included in the Application Layer.
What is the Link Layer equivalent to in the OSI model?
Physical + Data Link Layers in the OSI model.
What is the Internet Layer equivalent to in the OSI model?
Network Layer in the OSI model.
What is the Transport Layer equivalent to in the OSI model?
Transport Layer in the OSI model.
What does the Application Layer correspond to in the OSI model?
Presentation + Application Layers in the OSI model.
What is Bus Topology?
All data transmitted between nodes in the network is transmitted over a common transmission medium. All nodes in the network receive the data simultaneously.
How does data travel in Bus Topology?
Signal containing the address of the intended machine travels from the source machine in both directions to all machines connected to the bus until it finds the intended recipient.
What are the advantages of Bus Topology?
- Only one wire so less expensive.
- Suitable for temporary network.
- A node failure does not affect other nodes.
- Easy to add new devices to the network.
What are the disadvantages of Bus Topology?
- Limited cable length so size impacted.
- No security.
- Does not provide fault tolerance; if the central cable fails, the entire network may be affected.
What is Ring Topology?
bus topology in a closed loop where each device is connected to exactly two other devices.
How does data circulate in Ring Topology?
Data circulates in one direction around the ring until it reaches its destination.
What are the advantages of Ring Topology?
- Better performance than bus topology.
- All nodes have equal access.
- No central hub or switch, reducing the risk of a single point of failure.
- The path that data takes is predictable and easy to understand.
What are the disadvantages of Ring Topology?
- If there is a break in the ring, the entire network may be affected.
- Expanding the network can be challenging, and adding or removing devices can disrupt the network.
- As more devices are added, the performance of the network may decrease.
What is Star Topology?
Every node is connected to a central node called a switch or hub. Centralized management. All traffic should pass through the hub switch.
What are the disadvantages of Star Topology?
- Single point of failure affects the whole network.
- Bottleneck to overloaded hub/switch.
- Increase cost due to hub/switch.
What are the advantages of Star Topology?
- Easy to design and implement.
- Centralized administration.
- It is relatively easy to expand the network by adding more devices.
What is Mesh Topology?
Each node is directly connected to every other node in the network. It is fault tolerant and reliable.
What are the advantages of Mesh Topology?
- Fault tolerant as it withstands failures in individual links or devices without affecting the overall network.
- Reliable as if one link or device fails, alternative paths are available.
- With multiple paths, the network can support high data transfer rates.
What are the disadvantages of Mesh Topology?
- Issue with broadcasting messages.
- Expensive and impractical for large networks.
- adding more devices can become challenging and costly.
What is Hybrid Topology?
A combination of two or more topologies that benefits from all kinds of topologies.
What are the advantages of Hybrid Topology?
- More flexible, scalable, and secure.
- The ability to manage high traffic volumes.
What are the disadvantages of Hybrid Topology?
- High costs.
- Installation challenges.
- More hardware requirement.
Header Information (packet switching)
Each packet includes a header containing:
1. source and destination addresses
2. packet sequence number
3. error checking information.
Frequency Division Multiplexing
(FDM) (circuit switching)
▪ optical, electromagnetic frequencies
divided into (narrow) frequency
bands
Time Division Multiplexing (TDM) (circuit switching)
▪ time divided into slots
▪ each call allocated its own band, can
transmit at max rate of that narrow
band
▪ each call allocated periodic slot(s), can
transmit at maximum rate of (wider)
frequency band (only) during its time
slot(s)
Jitter: (performance measure)
Variation in latency, impacting real-time applications like video conferencing.
Packet Loss (performance measure)
- Rate at which data packets fail to reach their destination
- Common causes of packet loss
1. include network congestion,
2. inadequate bandwidth
3. network interference
4. hardware failures
5. errors in data transmission
Security Measures (7):
- Access control
- Data encryption:
- Network security:
- Application security:
- System hardening: Configuring systems and applications securely, minimizing attack
- Data backup and recovery:
- Security awareness and training:
IP spoofing
injection of packet with false source address
packet “sniffing”
promiscuous network interface reads/records all packets (e.g.,
including passwords!) passing by
What is encapsulation in networking?
process where each layer in the protocol stack adds a header to the data it receives from the layer above.
(ex) (think of stacking russian dolls)
The application-layer message (M) is encapsulated with a transport-layer header (Ht), creating a transport-layer segment (Ht M).
encapsulation (forms of data)
Message: application-layer message (M), such as an email or a web page request.
*
Segment: The transport layer encapsulates the message by adding a transport layer header (Ht) to the message M, creating a segment (Ht M).
*
Datagram: The network layer encapsulates the segment by adding a network layer header (Hn) to the segment (Ht M), creating a datagram (Hn [Ht | M]).
*
Frame: The link layer encapsulates the datagram by adding a link layer header (Hl) to the datagram (Hn [Ht | M]), creating a frame (Hl [Hn | [Ht | M]])
Propagation Delay Equation:
Propagation Delay = Distance(meters) / Propagation Speed
Example: A fiber-optic cable connecting two locations 150 kilometers apart has a speed of light of approximately 2 * 10^8 meters per second. The propagation delay is calculated as (150 * 1000 meters) / (2 * 10^8 meters per second) = 0.00075 seconds.
Transmission Delay Equation:
Transmission Delay = Packet size (bits) / Transmission rate (bits/second)
1GBytes=8Gbits
Example: Transmitting a 1 gigabyte (GB) file over a network with a bandwidth of 100 megabits per second (Mbps) results in a transmission delay of (1 GB * 8) / 100 Mbps = 80 seconds
Processing Delay Equation:
Processing Delay = Time to Examine + Time for Lookup + Queuing Delay + Time to Buffer
*
Example: A router with a Time to Examine of 2 milliseconds, Time for Forwarding Table Lookup of 1 millisecond, Queuing Delay of 0.5 milliseconds, and Time to Buffer of 1 millisecond has a processing delay of 2 ms + 1 ms + 0.5 ms + 1 ms = 4.5 milliseconds
Queueing Delay Equation:
Queueing Delay = Number of Bits in the Queue / Transmission Rate
Example: transmission rate of 2 Mbps and a queueing delay of 4 milliseconds
0.004 seconds * 2 * 10^6 bps
Total Delay Equation:
Total Delay = Propagation Delay + Transmission Delay + Processing Delay + Queueing Delay
*
Example: A packet with a Propagation Delay of 5 milliseconds, Transmission Delay of 10 milliseconds, Processing Delay of 2 milliseconds, and Queueing Delay of 3 milliseconds experiences a total delay of 5 ms + 10 ms + 2 ms + 3 ms = 20 milliseconds
Throughput Equation:
Throughput = Amount of Data / Time(Ms)
*
Example: If a network link with a bandwidth of 100 Mbps has an average end-to-end delay of 200 milliseconds for a 4 MB file, the throughput is (4 MB * 8 bits) / 200 ms = 160 Mbps
Ring topology (cable and port calc)
Cables = N
ports = 2x N
star topology (cable and port calc)
cables = N
ports = N
bus topology (cable and port calc)
cables = N
ports=N
mesh topology (cable and port calc)
Cables = N * (N-1)/2
Ports= N * ( N-1)
Bytes(Gb) to bits
1 GB = 8 bits
transmission rate
of MBps x 10^6 bps
seconds to millseconds
seconds×10^3
=milliseconds(ms)
Kilometers to Meters
km×1000=meters(m)
Storage Area Network(SAN)
is a dedicated network separate from
(LAN) or (WAN).
designed specifically for storage-related tasks
Physical media
physical communication channels or transmission
media used to transport data between devices
Guided media
known as wired media, is a communication
route that transmits signals by physical cables or wires. E.g. Twisted Pair
Cable (TP), Coaxial Cable, Fiber Optic Cable
Unguided media
known as wireless media, refers to the transmission
of signals across the air without the usage of physical wires. E.g. Radio
Waves, Microwaves, Infrared, Satellite Communication
Components of computer network
Nodes, media, services
