Chapter 1 Flashcards
What is the internet?
It is a combination of software and hardware.
Network infrastructure that provides services to different apps.
Hosts/end systems
any device connected to the internet
Communication Links consist of what?
Coax, copper wire, optical fibre, and radio spectrum
Transmission Rate
measured in bits/sec
Packets
segments of data with header
Packet switches
routers or link-layer switches
Distributed apps
involve multiple end systems that exchange data with each other
Internet Apps
run on end systems
API
specifies how a program on a end system asks internet infrastructure to deliver data to a specific destination program running on another end system
What is a protocol
It is a set of actions specified to define the format/order of messages exchanged between two or more communicating entities
Access Network
physically connects end systems to first router on a path from the end system to any other distant end systems
Home Access Exmaples
DSL, Cable, FTTH, Dial-up, Satellite
DSLAM
DSL access multiplexing- converts signal from digital to analog
Cable network
requires DSLAM from analog to digital and terminates at CMTS
Wifi
most prevalent in corporate, university, and home networks
3G/LTE
Uses a base station to connect phones
Physical media types
radio, satellite, cable
Example of unguided vs guided medium
Wifi-unguided, cable-guided
End to End Delay Example
N-Number of links
R-transmission rate
L-length of one packet
How does the router determine which link to forward to?
1) forwarding table: maps dest address to routers outbound links
2) end-to-end: asks directions
Circuit Vs Packet Switched networks
Circuit-resources are reserved for a duration of the session
Packet switched-resources are not reserved
FDM
Frequency is divided among established connections
TDM
Divides the time into frames of fixed duration and each frame is divided and has a fixed number of time slots
Does the ISP provide internet services?
No, Service provider does
Types of ISPS
Regional, Tier 1
Regional-connects regions of ISP’s
Tier 1-connects regional to Tier 1
Throughput
Amount of data that can be transfered
Processing Delay
Time requested to examine packet’s header and determine where to direct the packet, time check for bit-level errors
Queuing delay
packet waits in queue
Transmission Delay
Time requested to propogate
D Nodal delay formula
delay = delay(Proc + Queue + Trans + Prop)
When is queuing delay large?
WHEN TRAFFIC INTENSITY IS GREATER THAN 1
Service Model
1) Perform Action
2) Use services (layers above)
What is a protocol stack?
Protocols of various layers (taken together)
Top Down Approach
App –> Trans –> Net –> Link –> Phys
Consists of only five layers
What is the application layer?
Where apps and app layer protocols reside
ex) HTTP, FTP, and DNS
What is the transport layer?
Transports app messages
EX) TCP, UDP
What is the Network Layer?
Responsible for moving datagrams from 1 host to another
What is a datagram
Network layer packets
What is the Link Layer?
Delivers datagram to next node and frames link layer packets
What is the physical layer?
Move individual bits inframe from 1 node to the next
OSI Model?
7 layers
What is encapsulation?
To enclose or append data
