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On the Geographic Location of Internet Resources. CSCI 780, Fall 2005. Motivation. Physical structure of the Internet Geometry of the Internet infrastructure Geographic locations of Internet routers, links, and ASes. Question is. Approach is. Two sets of questions. Where are the routers? - PowerPoint PPT Presentation
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On the Geographic Location of Internet Resources
CSCI 780, Fall 2005
Motivation Physical structure of the Internet
Geometry of the Internet infrastructure
Geographic locations of Internet routers, links, and ASes
Question is
Approach is
Two sets of questions Where are the routers?
What is the relationship between population and density of routers?
Where are the routers
Population vs Routers Router density per person varies
widely across economic regions Raito of on-line people to routers
shows much less variability In economic homogeneous region
The number of routers per person is higher in areas of high population density
Superlinear relationship
Link density vs distance Large majority of link formation is
influenced by geographical distance Link (connectivity) patterns show a
strong relationship to distance 75%-95% of links are distance-sensitive
A small fraction of links is insensitive to distance Play an important structural role
Distance preference function
Two classes of links
Autonomous Routing Domains
A collection of physical networks glued togetherusing IP, that have a unified administrativerouting policy.
• Campus networks• Corporate networks• ISP Internal networks• …
Autonomous Systems (ASes)
AS is a set of routers under a single technical administration
An autonomous system is an autonomous routing domainthat has been assigned an Autonomous System Number (ASN).
RFC 1930: Guidelines for creation, selection, and registration of an Autonomous System
… the administration of an AS appears to other ASes to have a single coherent interior routing plan and presents a consistent picture of what networks are reachable through it.
AS Numbers (ASNs)
ASNs are 16 bit values.
64512 through 65535 are “private”
• Genuity: 1 • MIT: 3• Harvard: 11• UC San Diego: 7377• AT&T: 7018, 6341, 5074, … • UUNET: 701, 702, 284, 12199, …• Sprint: 1239, 1240, 6211, 6242, …• …
ASNs represent units of routing policy
Over 11,000 in use.
Two geographic properties of ASes Number of distinct locations
spanned by an AS Size of AS
Geographical dispersion of an AS’s components (routers) How an AS place its routers
Size of AS Number of degree in the AS-graph
(done before, SIGCOMM’99) Number of routers within one AS
(done before, CCR’01) Number of distinct locations
spanned by one AS
Observed distribution is highly variable, with long tail spanning many orders of magnitude (Power-law)
How does AS place its routers? Majority of ASes (around 80%)
have either one or two locations (zero area)
Among the remaining ASes, there is considerable variability in geographical dispersion
Geographic dispersion Small to medium Ases show wide
variability in their geographical dispersal
Largest Ases (exceeding certain threshold) are maximally dispersed geographically
Domain and Link length Inter-domain link vs intra-domain
link Inter-domain links tend to be twice as
long as intra-domain links Majority of links (83% or more) are
intra-domain. Average length of inter-domain links
approaches or exceeds the limit of distance sensitivity