Transcript TCP Flow and Congestion Control

We Need the Functions of
IP/ATM/SONET/WDM
Charlie Rohrs
Fellow, Tellabs Research Center
Visiting Scientist, MIT
SPIE, 9/20/99
Premise: Reliability and
Accountable QoS


Currently available public internet service will be
improved somewhat as IP evolves to IP++ with
some QoS distinction and possibly MPLS
trunking. For this service, any pipe structure will
do.
There will be a large and increasing class of
customers for whom the network is mission
critical. These customers will pay $BIG for:
» Accountable (Contractual) QoS
» Highly reliable uptime for all connections
Charlie Rohrs, Tellabs Research Center
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Functions in Today’s
Mission Critical Networks
WDM - fat pipes
 SONET - reliable pipes - protection,
network reprovisioning, granular flow
segregation, static reconfigurable QoS
 ATM, FR - efficient pipes - accountable
flexible QoS, VC Segregation, pipe
granularity and flexibility
 IP - universal access format and addressing,
routing for survivability (not reliability)

Charlie Rohrs, Tellabs Research Center
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What Does IP/WDM Really
Mean?

Will mission critical network customers be
satisfied with IP/MPLS watered-down
versions of ATM or FR functions?
IP++ = ATM--

Will WDM take over SONET functions?
Charlie Rohrs, Tellabs Research Center
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IP++ QoS and Reliability
Small amounts of downtime affect bottom
line and network manager’s careers
 Guaranteed service means it can be
measured and penalties assessed for failures.
 IP efforts intentionally avoiding exactly
what mission critical networks need contractual accountability and traffic
segregation

Charlie Rohrs, Tellabs Research Center
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IP++ QoS and Reliability
Current public internet shows poor QoS and
reliability even though it rides on protected,
reliable pipes
 Current poor performance is accepted because
connectivity and end services are new. As internet
services become mission critical, “Time is money”
will be applied.
 The IPites have usurped the “We have the answer
to all the problems” position from the Bellheads.

Charlie Rohrs, Tellabs Research Center
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Optical Crossconnects and
ADMs

SONET functions are almost reconstructable
» Optical switching times slow for protection
» Problem with wavelength shifting (like
crossconnects with no time slot interchange)
» Wavelength (OC48, OC192) granularity probably
too coarse for pipe management
» Fault detection, isolation, alarming need to be
reinvented

SONET Crossconnects with WDM ports more
likely
Charlie Rohrs, Tellabs Research Center
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Why Remove Layers?
Almost everything in the removed layers
needs to be reinvented.
 Minor improvements in bandwidth
efficiency is hardly compelling

» SONET dedicated OAM channels
» ATM small cell size
If you want to save boxes put two or more
functions in a box.
 Layering functions is good!!

Charlie Rohrs, Tellabs Research Center
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