30
PSTN Hierarchy cont.
nLocal (example,
within a city)
nSubscriber
connections
nSwitching within the
local exchange
nSwitching to other
exchanges
nTransit (county
level, say between Tampere and Helsinki)
nSwitching traffic
between different geographical areas within one country
nInternational
nGateway-type traffic
between
ndifferent
countries
nDWDM (Dense
Wavelength Division Multiplexing) routes
nRates can follow SONET or SDH standard
SDH
- transport of 1.5/2/6/34/45/140 Mbps within a transmission rate of 155.52 Mbps
- carries for instance ATM and IP within rates that are integer multiples of 155.52 Mbps
- transport of 1.5/2/6/34/45/140 Mbps within a transmission rate of 155.52 Mbps
- carries for instance ATM and IP within rates that are integer multiples of 155.52 Mbps