The Internet
- Not really a network at all, vast collection of different networks that use common protocols, provide common services
- The ARPANET
- DoD wanted a command and control network that can survive nuclear war
- switching offices, small redundancy
- contract to RAND Corporation Paul Baran designed distributed fault tolerant design
- ARPA (Advanced Research Projects Agency)
- worked by issuing grants and contracts to agencies and universities
- Subnets consist of minicomputers called IMPs(Interface Message Processsors)
- connected by 56kbps transmission lines
- connect to at least two other Imps so reroute possible
- node consist of IMP and host
- host can send messages 8063 bits
- IMP breaks into packets of 1008 bits and forward them to destination
- selected BBN to contract
- Honeywell DDP-316 minicomputers
- outside of subnet software needed
- host-imp
- host-host protocol
- application software
- Hosts need software too
- Arpanet connected universities
- Arpa announced contracts to build TCP/IP on different computer platforms
- IBM, DEC, HP systems, UNIX
- TCP/IP rewritten as sockets with the 4.2 BSD release of UNIX
- DNS(Domain Name System)
- NSF(National Science Foundation)
- NSF funded CSNET 1981
- NSF started backbone network to connect 6 supercomputers
- given a little brother fuzzball
- LSI-11 microcomputer
- connected libraries, research labs, museums, universities
- big success
- NSF realized government cannot continue funding
- encouraged MERIT MCI IBM
- form nonprofit corporation ANS(Advanced Networks and Services)
- Awarded 4 different network operators to establish NAP(Network Access Point)
- packet has choice of backbone carriers
- 1990s countries and regions followed suit, EuropaNET EBONE
- Now WWW(World Wide Web)
Architecture of the Internet
- Changed from beginnings
- ISP(Internet service provider)
- connects to home computer user purchases internet access or connectivity
- connect to ISP with phone line
- DSL(Digital Subscriber Line) reuses telephone line for data transmission
- DSLAM(Digital Subscriber Line Access Multiplexer)
- converts between signals and packets
- Dial-up
- use telephone line
- Modem-Modulator Demodulator
- Send over Cable TV System
- Device at the home is cable modem
- Cable headend is called CMTS (Cable Modem Termination System)
- DSL and Cable access at rates small fraction of megabit/sec to multiple megabit/sec
- rates much greater than dial up due to more bandwidth
- broadband
- FTTH(Fiber to the Home)
- fiber optic transmission 45 Mbps
- Location at which customer packets arrive at ISP Network PoP(Point of Presence)
- Long distance transmission lines interconnect routers at PoP in different cities for ISP to serve users.
- ISPs connect networks to exchange traffic at IXPs(Internet exchange points)
- peer with each other
- room full of routers to forward to ISP backbone
- Small ISP may pay larger ISP for distant hosts, pay for transit
- Path of packet depends on peer choices
- AT&T/Sprint are large so do not pay for transit
- Companies that provide large content, Google Yahoo, locate computers in data centers, designed for computers, server farm
- Colocation, hosting
- Intranets-companies self interconnected all internal networks
Third Generation Mobile Phone Networks
- AMPS(Advanced Mobile Phone System)
- Deployed 1982 first generation
- Second Generation - voice in digital form offer text messaging
- GSM(Global System for Mobile Communications)
- deployed 1991 2G
- UMTS(Universal Mobile Telecommunications System)
- 3G systems provide rates of 2 Mbps for stationary, 384 kbps in moving vehicle
- WCDMA(Wideband Code Division Multiple Access)
- main 3G system deployed, 14 Mbps on downlink, 6 Mbps on uplink
- scarcity of spectrum led to cellular network design
- within a cell, users assigned channel that do not interfere with one another
- allows for good reuse of spectrum
- allows each cell to use all frequencies
- Architecture
- Air Interface
- radio communication protocol over air between mobile and base station
- CDMA
- Base Station with controller forms
- radio access network
- Controller node RNC(Radio Network Controller)
- Node B
- Mobile phone network carries traffic for radio access
- called core network
- evolved from 2G GSM system that came before it
- Connectionless/Connection Oriented
- connectionless packet independently routed, dynamic reconfigure
- potential router choking lose packets
- circuit camp comes from telephone, stable system higher quality of service
- rejected calls, busy signal
- Older mobile phones use circuit switched core
- UMTS network with legacy elements set up connections over PSTN(Public Switched Telephone Network)
- MSC(Mobile Switching Center)
- GSMC(Gateway Switching Center)
- MGW(Media Gateway)
- GRPS(General Packet Radio Service) in GSM
- UMTS core network nodes connect directly to packet switched network
- SGSN (Serving GPRS Support Node)
- GGSN(Gateway GPRS Support Node)
- deliver data packets to and from mobiles and interface to external packet networks like internet
- Internet protocols used to set up VoIP, change to support quality of service
- Mobility, user moves in and out of base station, handoff/handover to reroute data to new station
- soft handover is when connect before disconnect possible
- hard handover, disconnect before connection established
- HSS(Home Subscriber Server)
- knows location of each subscriber and authorization
- Sim Card
- Subscriber Identity Module defines user
- authentication of user
- 4G technologies
- LTE(Long Term evolution)
- WiMAX
- 802.16 networks
Wireless LANs: 802.11
- Laptop connected to internet easily
- WiFi 802.11
- operate in unlicensed band such as ISM bands defined by ITU-R
- made up of clients and infrastructure
- access points/base stations installed in buildings
- clients talk to each other, ad hoc networks instead of access points
- multipath fading
- signals reflected off of solid objects causing fluctuations in signals
- solve issue with path diversity
- send along multiple independent paths so at least one good signal reaches destination
- OFDM (Orthogonal Frequency Division Multiplexing)
- divides wide band spectrum into narrow slices
- CSMA(Carrier Sense Multiple Access)
- determines if transmission band is free
- ALOHA wireless network
- setup in Hawaii
- Client Mobility
- moving away between access points, cell system implemented
- Security
- WEP(Wired Equivalent Privacy)
- tried to make wireless security like wired security
- broken scheme
- WPA
- Wifi protected access
- now replaced by WPA2
RFID and Sensor Networks
- RFID(Radio frequency Identification)
- a tag that is embedded into an object or person to be tracked
- passive RFID
- no power, reflects signal
- UHF RFID (Ultra High frequency RFID)
- 902-928 Mhz
- used on shipping and driver licenses
- HF RFID(High Frequency RFID)
- 13.56 Mhz
- LF RFID (Low Frequency RFID)
- active RFID
- has power sends signal
- Readers for RFID must solve issue of multiple tags in reading range
- easy collision in return
- Security for RFID
- Sensor Network
- monitor physical world
- multihop network
- relays messages between each other, self organization before sending to data collection point
