PSTN Architecture Overview (1)

PSTN Architecture Overview (1) PSTN: Public SwitchedTelephone Network History: From American Bellto AT&T Hierarchical and layerstructures Planned as a national network Design for Ilities– Service availability,– Sound Quality, Early realization of necessarybasic research on ilitiesSatellite linksSubmarinecablesInternational gatewayexchange (Centre de Transit 3)InternationalnetworkNational tandem exchanges(Tertiary trunk switchingcenters)Trunk networkRegional tandem exchanges(Secondary trunk switchingcenters)Local tandem exchanges(Primary trunk ber linesFigure by MIT OCW. 2005 Student: Jijun Lin, Daniel Livengood, Chintan Vaishnav, Engineering Systems Division, Massachusetts Institute of Technology1

PSTN Architecture Overview (2) Switching Hierarchy–––––RCRegional CenterSectional CenterPrimary CenterToll CenterEnd OfficeESESRCTrunk Circuit 0.5 to 1.5dBVNLSCSCClass 2 OfficesTrunk Circuit 0.5 to 1.5dBVNLPCPCClass 3 OfficesTrunk Circuit 0.5 to 1.5dBVNLTCTCVNL 2EOClass 1 OfficesJunction Circuit 2 to 4dBJunction CircuitJunction CircuitJunction CircuitTxSubscriberTClass 4 OfficesEOClass 5 OfficesJunction CircuitFinal RouteHigh UsageRouteESEcho SuppressorTandem OfficeSCSectional CentreAveAverageTCToll CentreEOEnd (Local) OfficeRCRegional CentreVNLVia Net LossPCPrimary CentreREGIONAL CENTERSFigure by MIT OCW.Regional Centers (1972)(12)Figure by MIT OCW.Five level switching plan in use from 1950s 2005 Student: Jijun Lin, Daniel Livengood, Chintan Vaishnav, Engineering Systems Division, Massachusetts Institute of Technology2

PSTN History(Collection by Prof. Whitney) Classification divides the PSTN into 5 levels (post1950):–––––Class 1: Regional Center, top level, 8 centers in 1930, 12 centers in 1972Class 2: Sectional Center (not a part of the 1930 network)Class 3: Primary CenterClass 4: Toll CenterClass 5: End OfficeImage removed for copyright reasons.Map of a U.S. telephone network.What/Where is the Data behind this Graphic? 2005 Student: Jijun Lin, Daniel Livengood, Chintan Vaishnav, Engineering Systems Division, Massachusetts Institute of Technology3

PSTN Definitions and Metrics Our network definitions– Node: Switching center– Link: Cable connecting switching centers Our metric focus– Geodesic length between two points: with mechanical switches,the goal was to have this be 3 or less– Bandwidth: where are the choke points? ntial Attachment (911? Critical infrastructure lines)Motifs 2005 Student: Jijun Lin, Daniel Livengood, Chintan Vaishnav, Engineering Systems Division, Massachusetts Institute of Technology4

Historical Connection PlansConnection plan to help decrease thegeodesic length in 1930 V (notice themotifs) and 1950 -- Class 1Regional CenterClass 2Sectional CenterNationalClass 3Primary CenterClass 4Toll CenterLocalClass 5End OfficeFive-level toll switching plan in use from the 1950s.A variety of routings was possible with a maximumof nine trunks in tandem.Figure by MIT OCW. After Andrews & Hatch, 1971.Figure by MIT OCW.Improved quality via level skipping 2005 Student: Jijun Lin, Daniel Livengood, Chintan Vaishnav, Engineering Systems Division, Massachusetts Institute of Technology5

Questions and Supporting DataPredicting/Explaining StructureWhich algorithms does the analysis of the actual structuresubstantiate?Data available: Switching Centers, Links in between, bandwidthsPredicting/Explaining PropertiesWhat are the properties of the structure as a result of addingavailability?Data available: 911-Tandem Links, Diverse Routing, LocationRouting NumbersObserving systemsWhat motifs do we see?Data available: Hierarchical view constructed from the dataSourcesTelcordia LERG Database, Quest Current Access Line Counts Database,Bellcore’s BOC Notes on intraLATA Network 2005 Student: Jijun Lin, Daniel Livengood, Chintan Vaishnav, Engineering Systems Division, Massachusetts Institute of Technology6

Telephone Network History: From American Bell to AT&T Hierarchical and layer structures Planned as a national network Design for Ilities – Service availability, – Sound Quality, Early realization of necessary basic research on ilities Figure by MIT OCW. Internat