Internet
- basic hardware and software components that make up the internet- a networking infrastructure that provides services to distributed applications
Protocol
- Set of rules governing the exchange or transmission of data between devices
- Defines format, order of messages exchanged among network entities, actions taken on message transmission, receipt or other event.- eg: TCP, IP, HTTP SKYPE, 802.11
Internet Standards
RFC: Request for commentsIETF: Internet Engineering Task Force
Network Core
Interconnected routers/network of networks
Access Networks
wired and wireless communication links
End System Interaction
Network that physically connects end system to the first router (edge router)
DSL (Digital Subsciber Line)
Use existing telephone line to exchange data with DSLAM located in telco's local central office
Cable Network
Use cable television existing infrastructure. Hybrid fiber-coaxial (HFC) network. Home share access network to cable headend. Shared broadcast medium ( every packet travels trough link/home). frequency division multiplexing: different channels transmitted in different frequency bands
Home network
Combine broadband residential access (cable modems or DSL) with inexpensive wireless LAN technologies.
Fiber to the home (FTTH)
provide an optical fiber path from the CO directly to the home
5G fixed wireless
high speed residential access without installing costly and failure-prone cabling from telco's central office to the home. Data sent wirelessly from base station to a modem in the home
Wireless access networks
Shared wireless access network connects end system torouter via access point
Data center network
high bandwith link connect hundreds to thousands of servers together to internet
Host
send packets of data
Host sending function
take app message, break into packets, transmit packets into access networks at transmission rate R
Bit
propagates between transmitter and receiver
physical link
what lies between transmitter and receiver
guided media
signal propagate in solid media E.g.: twisted-pair copper wire, coaxial cable, multimodefiber-optic cable
Unguided media
signal propagate free. eg: radio, terrestrial radio spectrum and satellite radio spectrum
twisted pair
two insulated copper wires
coaxial cable
two cocentric copper conductor, bidirectional
broadband
multiple frequency channels cable
fiber optic cable
glass fiber carrying light pulse each pulse a bit, low error rate cause immune to electromagnetic noise and repeaters spaced far apart
Packet Switching: Store-and-ForwardTransmission
router must receive entire packet before transmit it
Network core key function
routing and forwarding
Routing
determines source to destionation routes taken by packets
forwarding
move packets from router input interface to router output interface
circuit switching
connection oriented, dedicated circuit, guaranteed level of services, insufficient use of medium, single path no redundancy.
Packet switched
connectionless, shared circuit, messages divided into pakcets, effiecient use of medium, fault tolerant, multiple possible paths
End system connect to internet via
Access ISP
Evolution of network was driven by
Economics and national policies
Packet loss
cause q has limited capacity, thus packet lost, lost packe may be transmitted by previous node or source end system.
Throughput
critical performance in computer, rate which bits transferred between send-receiver
why layering
allows identification and relation of complex system, ease maintenance and system update
7. Application
Network process to application
6. Presentation
allow application to interpret meaning of data
5. Session
Interhost communication, managing session between app, sync and data recovery
4. Transport
Reliable delivery of packets between points on a network
3. Network
addressing, routing and delivery of datagrams between points on a network
2. Data link
A reliable direct point to point data connection
1. Physical
A direct point to point data connection
Malware can be
self replicate, user activate, program activated, recruit device to be part of botnet
virus
self replicate infection by receiving/executing object
worm
self replicate infection by passively receiving object that get itself execute
spyware malware
record keystrokes, webs visited, upload to site
Denial of Services : Dos
Attackers make resource unavailable to legitimate traffic by overwhelming with bogus traffic
packet sniffing
network interface that can read and record all packets
ip spoofing
send packets with false source address
Lines of defense:
authentication: proving you are who you say you are• cellular networks provides hardware identity via SIM card;no such hardware assist in traditional Internet▪ confidentiality: via encryption▪ integrity checks: digital signatures prevent/detect tampering▪ access restrictions: password-protected VPNs▪ firewalls: specialized “middleboxes” in access and corenetworks:▪ off-by-default: filter incoming packets to restrictsenders, receivers, applications▪ detecting/reacting to DOS attacks
instantaneous throughput
rate at given point in time
average throughput
rate over longer period of time