- Slides: 10
The Internet as a computing surface Avogadro-scale Computing MIT, April 17, 2008 Scott Kirkpatrick Hebrew University of Jerusalem and CBA, MIT
Questions … • Based on 4 yrs of Internet measurement activity – DIMES, ETOMIC, EVERGROW and Internet Archive • Is the Internet Avogadro-scale? • Routing IS asynchronous conformal computing – analyze it. • But the Internet is multi-layered – Data is centrally managed and closely-held • The current direction of growth is towards greater local independence • Independence and asynchrony have their costs – The details (data model, computational model, geographic distribution) are critical
Is the Internet really Avogadro-scale? • Avogadro’s number is really 2^78. 99 ~ 80 bits • Internet addresses: – IPv 4 2^32, IPv 6 2^128, IPv 4 with NAT ~ 2^64 – China takes NAT-ing the furthest, with only a very few entry points, huge internal address space. • Web content: modern search engines crawl 10^6 web pages/sec, ~2. 5 x 10^12 pages each month before discarding. “Deep web” maybe 100 x larger. • IPv 4 operates in layers, divided by subnetworks (ASes). • AS-AS uses BGP routing, inside AS uses shortest-path with link-state, may conceal all under MPLS…
Next discuss how the Internet is connected • K-shell analysis shows an interesting kind of hierarchical structure on the largest scale, gives unambiguous identification of the “nucleus. ” • It’s fractal, so the structure – if it has actually evolved to be a solution to more general problems – can be applied on many scales. • Percolation properties show that both local and long-ranged connectivity coexist
K-shell for network visualization DIMES monitoring project: www. netdimes. org
K-shell picture gives unique nucleus + fractal Carmi et al. , PNAS 2007
Meduza ( )מדוזה model This picture has been stable from January ‘ 04 (kmax = 30) to present day, with little change in the nucleus composition. The precise definition of the tendrils: sites isolated from the largest cluster in all the crusts – connect only to the core.
“Disruptive” Alternatives to today’s Protocols • The Medusa structure has consequences: routing, viewed as a computation, is changing… • Monitoring becomes a function in which every router participates. • Information shared beyond today’s “customer-provider privilege” – even one step helps a lot • Regional networking reduces dependence on long-haul carriers in the nucleus. • Each trend is towards more local interchange in a flatter “surface”
Synchronization and in-band Control • Roughening is an issue with distributed data-intensive CA-style computation. Can graded longer-range communications eliminate it? Are occasional small-world links enough? Which is more effective for the headaches required? SK, Science Perspective, 2004
Compute-intensive CA’s are different beasts • Single data source, serial execution algorithms (like sort) suffer no synchronization overheads. • Load and unload are critical • Ultimate “wallpaper computing” will develop its own models • Hierarchy ain’t going away anytime soon!