Transcript virtual hosts

Internet Statistics – Facts
and Figures
1st Tutorial Session for CEG3180B
January 18th, 2005
Stejarel Veres <[email protected]>
First things first: Internet?
 Probably the most used example
when it comes to Wide Area Networks
(WANs)
 Originally a DoD project [1], it has
become the most widely used public
internetwork
 It is the most technologically
heterogeneous network ever to exist,
short for one aspect: TCP/IP
Stejarel Veres <[email protected]>
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Why Internet Statistics?
 Question: Why would we be
interested in the Internet host count
trends?
 Several pertinent answers:
 Curiosity 
 Bandwidth consumption (i.e., traffic)
forecasting
 Address space usage forecasting
 … etc.
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Well, how many are they?
 How many what?
 Hosts
 Originally, a host was a single computer on the
network
 With the introduction of virtual hosts, however,
a single computer could represent more than
one host
 So… should we count virtual hosts too or not?
 According to the ISC, in June 2004 there
were about 300 million hosts in the
Internet
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What does this survey tell us?
 Basically, that the number of hosts in the
Internet is growing exponentially:
Y (t )  361735e
0.0472t
 This means that the “Internet population”
doubles approximately…
ln 2
t
 14.7
0.0472
 … every 15 months!
Stejarel Veres <[email protected]>
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How does the survey work?
 It is a Domain Name System (DNS) [3] survey
 What is the Domain Name System?
 A hierarchical (i.e., similar to the postal address
system) way to name hosts in order to set a
correspondence between domain names and IP [4]
addresses
 Top-level domains: .com, .net, .edu, .mil, .gov, .org,
.int (and the more recent .biz, .info, .to etc.) and the
country top-level domains
 Second-level domains: usually (but not always)
organizations
 E.g., www.uottawa.ca means ‘the web server’
(www) ‘of the University of Ottawa’ (uottawa) ‘which
is in Canada’ (ca)
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How does the survey work? (2)
 Two methods:
 Walking the domain name tree and doing
zone transfers of domain data in order to
discover hosts and further subdomains
(original method, used until 1997)
 Walking the reverse delegation zones
(i.e., in-addr.arpa) and counting all
addresses that have been assigned a
domain name (new method, used since
1998)
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Is the survey accurate?
 Question: How far can we trust these
results?
 Answer: They will have to do it.
 Neither of the two survey methods is
free of errors – it is virtually
impossible to know the exact number
of hosts in the internet
 However, a good approximation
should be sufficient
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Is the survey accurate? (2)
 Reasons for the surveys not being able to
provide error-free results:
 Many DNS servers do not allow for whole zone
transfers
 Not all hosts are registered in a domain name
server
 Poorly configured DNS servers can lead to bogus
entries
 Just because a hostname is assigned an IP
address or vice-versa, does not mean that the
host actually exists
 Poor connectivity can pose difficulties to the
data collection process
Stejarel Veres <[email protected]>
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Interesting facts
 What has the number of hosts in a certain
country to do with its economic status?
 More .net hosts than .com hosts – does this
mean that there are more hosts for
“infrastructure” than for “services”?
 The top 2 host names: ~ 1 million www, ~
400k mail
 Canada has about 3.5 million hosts in 21k
domains
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Conclusions
 The “Internet population” is growing
at an exponentially rate
 Keeping track of the number of hosts
in the Internet is important, for
several reasons
 However, an extremely accurate
counting is virtually impossible
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References
1. http://www.isoc.org/internet/history
2. http://www.isc.org/ds
3. P. V. Mockapetris, STD0013/RFC1034:
Domain names – concepts and facilities
4. J. Postel, STD0005/RFC0791: Internet
Protocol
5. S. Deering, R. Hinden, RFC2460: Internet
Protocol, Version 6 (IPv6) Specification
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