Jellyfish and other Interesting creatures Of the Internet
- Slides: 26
Jellyfish, and other Interesting creatures Of the Internet Scott Kirkpatrick, Hebrew University with Avishalom Shalit, Sorin Solomon, Shai Carmi, Eran Shir, and Yuval Shavitt 25 May, 2005 Copyright, Pixar, Inc. 2003
DIMES@home – Internet topology map • Previous efforts to measure the Internet have used: – One machine + Traceroute to many destinations – Many* machines, specially deployed to traceroute to many destinations • * Many <= 50 because of management headaches • Sites restricted to academic or gov’t labs, on network backbone • General perception was that Law of Diminishing Returns has set in • http: //www. netdimes. org seems to have made a breakthrough – Don’t manage machines, offer a very lightweight, limited purpose client, and collect its measurements centrally • 100 – 1000 clients via word-of-mouth (Sep 04 to April 05) • 1000 – 5000 clients achieved via press, slashdot, still in the geek community – (May 05 -- ? ) • 5000 – 50000 clients in the general public by offering services in return – Somewhere in the 5000 -10000 client range, we have the network monitoring itself, and the possibility that it can also manage itself in real time.
Contribution distribution with 2 K users, >3 K agents
Exploring the DIMES AS-graph • • We consider the Internet at the level of its autonomous systems (ASes) Previous studies have used degree as indicator to decompose networks – In particular, the Faloutsos’ “jellyfish model” • Identify core of network as maximal clique • Shells around network labeled by hop count from core (a small world) • Find unusual structure of peripheral sites • • We consider longer-range connectivity, using k-pruning. K-core, K-shell, and K-crusts result – K-shell is “derivative” of K-core, K-crust is union of K-shells – Near power-law structure of a new “inflow” region is observed – K-shells are not connected, but K-crusts have a giant cluster • For Erdos-Renyi graphs, K-core is w. h. p. K-connected. For scale free? • Result – focus attention on the capabilities of the inflow region, in support of P 2 P, chat, local traffic. Next steps – reachability is much harder than percolation. •
How does original degree map into k-shell?
K-shell decomposition
K-shell decomposition, March 2005
K-shell decomposition, April 2005
May 20, slashdot doubles DIMES users
Now offering: monthly public stats
The K-core is at least K-connected
K-shell for network visualization Using La. Net-Vi http: //xavier. informatics. indiana. edu/lanet-vi
Michalis Faloutsos’ Jellyfish Shells 3 2 1 Core • Highly connected nodes form the core • Each Shell: adjacent nodes of previous shell, except 1 degree nodes • Importance decreases as we move away from core • 1 -degree nodes hanging • The denser the 1 -degree node population the longer the stem
Meduza ( )מדוזה model In January, the inner core was at K = 30, but this picture persists to the present day, when core is >40.
K-crusts show percolation threshold These are the hanging tentacles of our (Red Sea) Jellyfish Largest cluster in each shell Data from 01. 04. 2005
Tendrils occur over a range of k-shells
Links per site of k-shells to k-core (above) and to k-crust (below)
Where do the links go in Medusa? Early shells (1 -10) link to intermediate shells as well as to the core.
Average distance between sites in a crust
K-shell participation in giant clusters
Random scale-free graphs produce the same structure • Seen in both Barabasi-style and Molloy-Reed models of scale free networks
Next steps • New data permits reexamining the clustering behavior – Much data not seen in previous BGP-based studies – This is the major deviation from simple random models – Analyze as a function of k-shell, instead of simply degree • Reachability is not percolation, but can be evaluated – Decision to transmit a message depends on sender and destination, not simply on the existence of a link – Cost of evaluating uphill-downhill reachability is comparable to shortest path
Preliminary reachability data (std data set)
Now add sideways steps at top of path
Now restrict to the 20 -crust
Sideways step less effective inside crust
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