CrossLayer Optimisations for Survivable Networking Piyush Upadhyay, Manolis Sifalakis, David Hutchis

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Cross-Layer Optimisations for Survivable
NetworkingPiyush Upadhyay, Manolis Sifalakis,
David Hutchison, James P.G. Sterbenz
www.ittc.ku.edu/resilinets
Protocol Layering
2-Layer Model E2EHBH

• Traditional strict layer boundaries
• good architectural abstraction
• layers based on network roles
• separation of concerns
• e.g. IP over any link layer (802.n, SONET,)
• Strict layering results in poor performance
• too much information hiding
• need translucency between layers
• implicit assumptions ? improper response
• e.g. TCP over wireless throttles on corruption
• limits cross-layer modular-reuse of functions

application knobs/dials
E2E context
E2E context
E2E
E2E
vertical explicit signalling
cross-layer in-band signalling
horizontal explicit signalling
HBH context
HBH context
HBH
HBH
HBH
HBH
HBH
physical environment dials/knobs

• Initial ns-2 model end-to-end hop-by-hop
• other layers (e.g. path routing) later
• Gain fundamental understanding
• cost (complexity) vs. benefit (performance)

Cross-Layer Optimisations
Performance Gains

• Relax layer semantics fuzzy boundaries
• improve performance and survivability
• while retaining most benefits of layering
• Cross-layer control loops
• dials expose characteristics below
• knobs influence behaviour
• e.g. error control based on loss characteristics
• Composable protocol functionality
• new modules (e.g. FEC, ARQ) as needed
• functionality may reused by multiple layers

LTN 250ms 1-way 1.5Mb/s competing 4?UDP CBR
0.25Mb/s on/off exp mean 0.5s 30 min. run 536B
segment 2400 seg window

• Performance bound (perfect information)
• cause of loss explicitly signalled to TCP
• previous TCP ETEN work KrishnanSterbenz2004