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Recursive Network Architecture (RNA): One Protocol, Many Layers

Explore the impact of layering with RNA, a metaprotocol that fills gaps between layers and stacks, supporting interlayer cooperation and runtime composition. Challenges, features, and how RNA extends X-Bone's choices model.

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Recursive Network Architecture (RNA): One Protocol, Many Layers

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  1. One Protocol / Many Layers: A Recursive Network Architecture Joe Touch Postel Center DirectorUSC/ISI Research Assoc. Prof.USC CS & EE/Systems Depts.

  2. Outline • Motivation • Observations that lead to RNA • Features of RNA • Challenges • Related Work

  3. Motivation • Layers of a stack becoming more similar • Security, soft-state, pacing, retransmission • Desire to support interlayer cooperation • Message boundary, cong. control, compression vs. encryption interactions • Desire to support overlay layers • Clearly needed, but don’t map to 1-7

  4. Goals • Explore impact of layering • More than an code artifact • Support reuse • Avoid reimplementation of features • Support coordination • Simpler to interface ‘to yourself’ • Support runtime composition • Extends X-Bone’s Choices model

  5. Internet Extensions Accused of ossification, but: • Ossification = stability • Plenty of extensions refute bad connotation: • Shim layers: • HIP, SHIM6, IPsec, TLS • Muxing layers: • SCTP, RDDP, BEEP • Connections: • MPLS, GRE, IKE, BEEP, SCTP • Virtualization: • L2VPN, L3VPN/X-Bone/RON/Detour, L7-DHTs

  6. Challenges: • Which to add… • IPv4/IPv6, TCP/DCCP/SCTP • When to add… • Security, muxing, cong. control • Real vs. virtual • What’s the difference?

  7. RNA – fills the gaps • Between layers (left, from Choices) • Affects next-layer • Between stacks (right, from Padlipsky) • Affects next-hop

  8. SharedState Security FlowControl Next LayerResolution RNA Metaprotocol • Template of basic protocol service:

  9. Observations • Services are relative • A template can avoid recapitulation • Composition requires coordination

  10. Application Presentation Session Transport Network Data link Physical The OSI 7-layer Model • Layer indicates function • But… • Functions are recapitulated: • Formatting at link and presentation • Muxing attransport and session

  11. What makes a layer a layer? • Its endpoints • A hop in a layer is the entire extent of the layer below (E2E argument goes here) • The layer above • What services this layer provides • The layer below • What services this layer requires

  12. Host App Program Trans Net Process Service is defined by context • Shared state exists at many layers, but supports different services • App binding • Transport delivery • Net security • Difference is scope • Endpoints vary

  13. HTTP IPsec HTTP XDR XDR BEEP BEEP TCP TCP Virt. IP IP Virt. IP 802.3 IP 100bT 802.3 100bT Adding Services is Hard • Wedge between (IPsec, left) or replicate (virtualization, right)

  14. Recapitulation • Component services repeat: • handshake / state management • security • policy (admission control, filtering) • multiplexing and demultiplexing • retransmission • reordering • pacing / congestion control • switching / forwarding • Compounded by virtualization • Layer on layer on layer

  15. Composition Requires Coordination • Many services integrate layers • Congestion control • Message boundaries • Security • State establishment • Current interlayer interface is limited • Defined by each layer • No general security, state, etc. interface

  16. Features • As many layers as you need • Context sensitivity • Extends Choices’ Multi-Domain Communication Model (MDCM)

  17. RNA mp-4 RNA mp-3 RNA mp-2 RNA mp-1 physical RNA Stack • Only needed layers • With only needed services • One MP, many instances • Configurable like TP++ • Retain layers to limit scope

  18. RNA mp-4 RNA mp-4 RNA mp-3 RNA mp-3 RNA mp-2 RNA mp-2 RNA mp-1 RNA mp-1’ wireless optical Layer Context Sensitivity • E.g., mp-1 morphs varies when over wireless vs. optical • Opportunity for auto-tuning

  19. LAYER(DATA, SRC, DST) Process DATA, SRC, DST into MSG WHILE (Here <> DST) IF (exists(lower layer))Select a lower layer Resolve SRC/DST to lower layer S’,D’      LAYER(MSG, S’, D’) ELSE FAIL /* can’t find destination */ ENDIF ENDWHILE /* message arrives here */ RETURN {up the current stack} Next-hopResolution Next LayerResolution MDCM from Choices • One template for ARP, BGP, IP, DNS • Also for BARP • Structured template • With plug-in funcs.

  20. Components of RNA MP Instantiate MDCM’s “Process DATA” • Establish / refresh state • Encrypt / decrypt message • Apply filtering • Determine whether to proceed based on flow control • On input, determine whether to proceed based on reordering • Multiplex/demultiplex as indicated (includes switching/forwarding)

  21. Challenges • MP design • Building a sensible, generic template • Stack management • Supporting instantiation and composition • Supporting interlayer coordination • Designing a sensible, recursive API • Supporting context sensitivity • Detecting environment and autotuning

  22. Related Work • Modular protocol environments • Click, x-Kernel, Netgraph, Flexible Protocol Stacks • RNA adds a constrained template • Template protocol models • MDCM, RBA • RNA adds structured sequence of services • Context-sensitive protocols • PEPs, Shims, intermediate overlay layers, etc. • RNA incorporates this into the stack directly • Configurable protocols • XTP, TP++, SCTP • RNA makes every layer configurable, but keeps multiple layers.

  23. Current Status • Funding started 9/15/06 ;-) • (watch this space for future news)

  24. And now for somethingcompletely different…

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