to TCP or not to TCPto TCP or not to TCP

D. TowsleyD. Towsley

U. MassachusettsU. Massachusetts

Observations on TCPObservations on TCP TCP TCP 1/p 1/p½½ (defined as a response function)(defined as a response function)

not appropriate for region of low pnot appropriate for region of low p

redefine response function for small p redefine response function for small p

~ 1/p ~ 1/p 0.84 0.84 p < 0.001 p < 0.001 (S. Floyd)(S. Floyd)

or ~ 1/p , p < 0.001 or ~ 1/p , p < 0.001 (T. Kelly)(T. Kelly)

both do well!both do well! at least 1Gbpsat least 1Gbps fairness?fairness?

Enhanced TCP CC algorithm robustEnhanced TCP CC algorithm robust

thro

ughp

ut

loss prob.

Observations on Transport Observations on Transport

several successful transport protocolsseveral successful transport protocols even TCP (carefully tuned)!even TCP (carefully tuned)! > 1 GBs > 1 GBs

current limitations lie outside transport current limitations lie outside transport protocolprotocol access BW (1GE)access BW (1GE) NIC issuesNIC issues I/O (disk to NIC)I/O (disk to NIC) OS issuesOS issues the hard stuff!

Observations on Transport (ctd.)Observations on Transport (ctd.)

need for standardized protocolneed for standardized protocol reduces net admin costsreduces net admin costs

frees up money for researchfrees up money for research specialized vs. general purposespecialized vs. general purpose scalable protocolsscalable protocols

10Gbs – 40 GBs – 160Gbs – 640Gbs10Gbs – 40 GBs – 160Gbs – 640Gbs bit errors? bit errors? congestion notification?congestion notification?

startup, fairnessstartup, fairness

thro

ughp

ut

loss prob.

HSTCP?

1/p

What do workloads look like?What do workloads look like?