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Sept 9, 2002 ISI 30th -- Bob Braden -- New Arch 1 Rethinking the Internet Architecture Bob Braden USC Information Sciences Institute 30th Anniversary Sept 9, 2002
Sept 9, 2002 ISI 30th -- Bob Braden -- New Arch 1
Rethinking the Internet Architecture
Bob Braden
USC Information Sciences Institute 30th Anniversary
Sept 9, 2002
Sept 9, 2002 ISI 30th -- Bob Braden -- New Arch 2
What is “Network Architecture” ?
• A set of fundamental design principles to guide the detailed [protocol] engineering.
Architecture: both a science and an art.
Sept 9, 2002 ISI 30th -- Bob Braden -- New Arch 3
Network Architecture
• Informal architectural ideas guided the design of the Internet protocols, but formal discussion of the Internet architecture only came 10 years later... – “The Design Philosophy of the DARPA Internet Protocols”,
David D. Clark, SIGCOMM ‘88, p.106.
• The boundaries of “architecture” are fuzzy:
– Bounded from “above” by requirements – Bounded from “below” by engineering.
Sept 9, 2002 ISI 30th -- Bob Braden -- New Arch 4
Network Architecture
• The “Network architecture” metaphor emerged from mathematical sciences (CS), not from engineering. – Simplicity is vital, and elegance is desirable
• Builds upon Computer-Sciencey kinds of concepts... – Modularity – Naming -- global vs. local – [Communication] state -- Where & how? – Indirection – Resource allocation – Security boundaries -- Where and how? – Etc...
Sept 9, 2002 ISI 30th -- Bob Braden -- New Arch 5
Foundation of the Internet architecture: The End-to-End Principle
“Dumb network, smart end systems”
(Exact opposite of telephone network!)
• Dumb network: – Provides only least common service across all technologies
• Datagram service: no connection state in routers • Best effort: all packets treated equally.
– Network can lose, duplicate, reorder packets.
• Smart hosts: – Maintain state to enhance network service (e.g., reliability, ordering...) – “Fate-sharing”: If a host crashes and loses comm state, applications that
are communicating share this fate.
Sept 9, 2002 ISI 30th -- Bob Braden -- New Arch 6
So, Where are We?
• The Internet design has been very successful – Scaled into a huge worldwide infrastructure – Adapted to many new comm technologies
• Frame Relay, ATM, wireless, optical, ...
– Easily adapted to unforeseen applications -- Web, P2P – Adapts over a huge dynamic range -- O(106)
• BUT... – Serious new challenges -- new requirements and issues – An increasing loss of technical coherence
Sept 9, 2002 ISI 30th -- Bob Braden -- New Arch 7
New Challenges to Architecture
• Commercial Internet – Business models -- ISPs need to be able to make money – Need to harness competition to drive innovation – Legal, political, and public policy issues
• Erosion of trust (Loss of innocence) – Spam/viruses/worms/DDoS attacks/...
• New technologies and applications – Optical networking – IP telephony
Sept 9, 2002 ISI 30th -- Bob Braden -- New Arch 8
Loss of Technical Coherence
• Equipment vendors want to sell boxes – They are busily designing point solutions to specific
problems; often in conflict, lacking in generality. – Looks like a downward spiral into technical chaos.
Sept 9, 2002 ISI 30th -- Bob Braden -- New Arch 9
Internet Architectural Principles
P1. Multiplexing P2. Transparency P3. Universal connectivity P4. End-to-End argument P5. Subnet heterogeneity P6. Common Bearer
Service P7. Forwarding context P8. Global addressing
P9. Routing P10. Regions P11. Protocol Layering P12. Minimal Dependency P13. Security P14. Congestion P15. Resource Allocation P16. Mobility
(Trust me ...)
Sept 9, 2002 ISI 30th -- Bob Braden -- New Arch 10
Ooops...
Every one of these 16 architectural principle categories is problematic in some manner! (a) Being broken for commercial reasons (b) Being broken to obtain additional functionality (c) Protected against unwise optimization only by
constant struggle in the IETF. (d) Represent real unmet requirements (e) Mods urged by mysterious government agencies
Sept 9, 2002 ISI 30th -- Bob Braden -- New Arch 11
NewArch -- the Dream
• Could a new Internet architecture restore some technical coherence and meet new requirements? – A small DARPA-funded project, NewArch, has been
trying to answer this question. • Objective: to figure out what the Internet
architecture would have been if we had known in 1979 what we know today.
• Ignore compatibility/transition issues.
Sept 9, 2002 ISI 30th -- Bob Braden -- New Arch 12
The NewArch Players
Primary participants have been: • At ISI: Bob Braden, Ted Faber, Aaron Falk, & Venkata
Pingali. • At MIT: Dave Clark, John Wroclawski, Karen Sollins, & a
cast of GRAs. • At ICIR (UCB): Mark Handley & Scott Shenker • At AT&T: Steve Bellovin • Noel Chiappa
Sept 9, 2002 ISI 30th -- Bob Braden -- New Arch 13
NewArch -- the Process (1)
• Re-examine the requirements and assumptions, and how they have changed.
• Try to understand implications for the Internet architecture of economic, political, and social forces.
• Examine a set of propositions of the form: • What if we relaxed assumption X? • What if we added assumption Y?
and pursue a few of the promising Xs and Ys.
Sept 9, 2002 ISI 30th -- Bob Braden -- New Arch 14
Original Internet Requirements
• Survivability (robustness) – Messages must get through, “no matter what”.
• Service generality – Support widest possible set of applications and service
models, from FTP to Telnet to packet video and voice. • Diverse network [“sub-net”] technologies
– Heterogeneity is fundamental: must communicate across arbitrary interconnection of links - LANs, WANs, wireless, satellite, ...
Sept 9, 2002 ISI 30th -- Bob Braden -- New Arch 15
Led to a Network of [sub-]networks
R
R
R
Host
Hosts
Host
subnet
subnet
subnet
packet
INTERNET
Router [gateway]
Sept 9, 2002 ISI 30th -- Bob Braden -- New Arch 16
Sept 9, 2002 ISI 30th -- Bob Braden -- New Arch 17
Internet Architecture: Deep Assumptions
• Packet switching – Unit of data is a packet – Packets are statistically multiplexed
• Strict protocol layering – Successive layers of functional abstraction – Header encapsulation
• Headers added/removed in strict LOFO order -- “Stack”model.
• Hop-by-hop forwarding – More robust than source-routed or connection-oriented networks.
Sept 9, 2002 ISI 30th -- Bob Braden -- New Arch 18
Erosion of the End-to-End Principle
A current architectural battleground…
• “Middle boxes” process user packets inside the network. – E.g., web caches and proxies, application-level firewalls, NAT
boxes, performance-enhancing proxies, …
– They perform useful functions but violate the E2E Principle.
– That is more than religion -- they reduce robustness, generality, extensibility, and simplicity.
Sept 9, 2002 ISI 30th -- Bob Braden -- New Arch 19
NewArch -- the Process (2)
• Re-examine the requirements and assumptions, and how they have changed.
• Try to understand implications for the Internet architecture of economic, political, and social forces.
I don’t have time to talk about this today. See: “Tussle in Cyberspace: Defining Tomorrow’s Internet”, D. Clark, J. Wroclawski, K. Sollins, & R. Braden. ACM SIGCOMM 2002, Aug 02.
Sept 9, 2002 ISI 30th -- Bob Braden -- New Arch 20
NewArch -- the Process (3)
• Re-examine the requirements and assumptions, and how they have changed.
• Try to understand implications for the Internet architecture of economic, political, and social forces.
• Examine a set of propositions of the form: • What if we relaxed assumption X? • What if we added assumption Y?
and pursue a few of the promising Xs and Ys.
Sept 9, 2002 ISI 30th -- Bob Braden -- New Arch 21
Sample of Propositions Considered
• Relaxed assumption X =: • Only packets (e.g., no bit streams) • Protocol layering • Network locator identical to end-point identifier
• Added assumption Y=: • Provide regions of trust • Support ubiquitous mobility • Carry congestion state in packet headers • Empower users to choose ISPs (=> competition)
Sept 9, 2002 ISI 30th -- Bob Braden -- New Arch 22
NewArch -- the Results
• A lot of talk... – 18 3-hour teleconferences, 3 face-face meetings – 28 internal working papers
• A few conference papers • Some new research directions • Quite a lot of overlap with earlier work, but within
a broader framework. • Too many ideas, too little time... !
