Week 2 Flashcards
What are the 2 viewpoints in describing the internet?
- Nuts and bolts view
- Service view
What is the nuts and bolts view of the internet?
The internet as a “network of networks”
Structure, components, and how they interact w/ each other.
The internet is billions of connected devices.
What is a packet switch?
Forwards packets (chunks of data)
2 types of packet switches
- router
- link layer switch
What is a network?
Collection of device, routers, links: managed by an organization.
Can send/receive data
What is the “services” view of the internet?
Internet is an infrastructure that provides services to apps: web, streaming video, multimedia
What are protocols?
Similar to “rules” that define the format and order of messages sent and received, and the actions taken on transmission.
What is the structure of the internet? (3 structures)
- Network EDGE consisting of access networks.
- Network CORE consisting of routers/links
- Network of Networks
What are the 2 types of media?
Guided Media: signals that propagate in solid media
Unguided Media: signals that propagate freely
What is Twisted Pair? What is it used in?
- 2 insulated copper wires
- Mostly used in local area networks
What is Coaxial Cable? Uses?
- 2 CO-centric COpper COnductors
- Used in Cable TV / Internet
What is a Fiber Optic Cable? Pros and Cons? Uses?
- Glass fiber carrying light pulses INSTEAD OF magnetic pulses
- Pros: immune to electromagnetic noise
- Cons: expensive
- Useful for network cores
What is Wrieless radio?
- Signal carried in various bands of the EM spectrume
- Unguided media
- Broadcast (in all directions)
Some cons of wireless radio?
Signal Attentuation
- reflection
- obstruction by objects (shadowing effect)
- interference (Multipath fading)
Different types of radio?
- Wireless LAN (10m)
- Wide Area (10km)
- Satellite
How to calculate the time it takes to transmit a packet?
L = # of bits
R = transmission rate
time = L/R
A general case of sending ONE packet from source to destination, over a path consisting of N links each with a rate R (There are N-1 routers between source and destination) is ? (in a store and forward transmission)
d = NL/R.
What is store and Forward Transmission?
the packet switch must receive the ENTIRE packet before it can begin to transmit the first bit of packet onto the outbound link.
What is packet loss?
Occurs when the buffer is full with other packets already waiting for transmission. The packet is dropped.
What are Forwarding Tables?
-used to map and index destination addresses to the router’s outbound links.
- router examines PORTIONS of the address and uses it to find the right link.
What are Routing Protocols?
- used to set forwarding tables
- may determine the shortest path from each router to eac destination
What is packet switching?
- Breaking messages into packets
- packets are forwarded from one router to the next accross links
What is circuit switching?
Each connection gets a dedicated circuit, where:
- resources are reserved for the duration of the communication
2 main ways to transfer data through the net?
- packet switching
- circuit switching
Pros and Cons of Packet Switching?
Pros: better sharing of transmission capacity, more efficient and less costly
Cons: unpredictable queuing delays
Pros and Cons of Circuit Switching?
Pros: guarantees a constant transmission speed
Cons: Expensive, requires connection setup, idle during silent periods
2 Ways to Multiplex in a CIRCUIT SWITCHED NETWORK?
- FDM (Frequency-Division Multiplexing)
- TDM (Time-Division Multiplexing)
What is FDM?
Frequency Division Multiplexing
link dedicates a frequency band to each connection. The width of the band is called the bandwidth
What is TDM?
Time Division Multiplexing
time divided into frames for a fixed duration, each connection gets its own time slot.
Transmission rate of TDM?
= bit rate / time slot
= frame rate * bits per slot
What are the 2 key network-core functions?
- Forwarding / Switching
- RoutingW
What is Forwarding / Switching?
A local action, moving arriving packets from router input link to appropriate router output link
What is routing?
Determining the entire path of a packet. Sets all the forwarding tables in a network
