Ch. 1 - Intro to Computer Networks Flashcards
Internet overview, protocols, networks, performance, layering
What is the Internet?
Millions of connected computing devices.
Network Protocols
Define the format and order of messages sent/received among network entities, and actions taken on message transmission and receipt.
Network structure
Network edge, access networks, physical media, and network core
Network Edge
- hosts, access network, physical media
- Devices connected to the network, such as computers, smartphones, and IoT devices.
Network core
mesh of interconnected routers; network of networks
Performance
loss, delay, throughput
Key Network Core functions (2)
- forwarding (a.k.a. “switching”)
- routing
Store-and-Forward
entire packet must arrive at router before it can be transmitted on the next link
Packet queueing and loss
if arrival rate (in bps) to link exceeds transmission rate (bps) of link for some period of time:
* packets will queue, waiting to be transmitted on output link
* packets can be dropped (lost) if memory (buffer) in router fills up
How are end systems connected to edge routers?
Via access networks/nets
DSL
Digital Subscriber Line. A method of connecting to the Internet via a phone line. Voice goes over the DSL to the telephone net, and Data goes over to the internet.
Frequency Division Multiplexing
different channels transmitted in different frequency bands
Time Division Multiplexing
each call allocated periodic slot(s), can transmit at maximum rate of (wider) frequency band (only) during its time slot(s)
What is The difference between DSL and HFC
For HFC homes share access network to cable headend, where as DSL (digital subscriber line) has dedicated access
Hybrid Fiber Coax (HFC)
A network architecture that typically uses fiberoptic cables to bring signals to selected areas of the system called nodes, which are usually based on number of subscribers to be served.
Wireless access networks
Connects end system to router via base station (“access point”)
Packet switching
Where the host breaks application-layer messages into packets
Circuit switching
end-end resources allocated to and reserved for “call” between source and destination
What methods are used for resource allocation?
Packet switching and Circuit switching
What can a ‘bad guy’ do in network security?
Eavesdrop, impersonate, hijack, and DoS.
DoS
Denial of service. Attackers make resources (server, bandwidth) unavailable to legitimate traffic by overwhelming resources.
What is packet sniffing?
An application/device monitors and reads network packets as they transverse the network. Plaintext/Cleartext can be read.
What is IP spoofing?
Sending information into the network with false “Sender IP” information.
Communication links
fiber, copper, radio, satellite
transmission rate = bandwidth
What are Networks?
Collection of devices, routers, links: managed by an organization
