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