Online Social Networks
CPE 401 / 601
Computer Network Systems
Mehmet Hadi Gunes
Modified from Philipa Gill
Basic definitions
• Network: (net + work, 1500’s)
• Noun:
– Any interconnected group or system
– Multiple computers and other devices connected together
to share information
• Verb:
– To interact socially for the purpose of getting connections or
personal advancement
– To connect two or more computers or other computerized
devices
What is a Social Network ?
• Network – a set of nodes, points or locations
connected
• Social Network - a social structure made up of
individuals (or organizations) called "nodes", which
are tied (connected) by one or more specific types
of interdependency, such as friendship, common
interest
• Online Social Networks – Platforms to build social
networks among people who share interest,
backgrounds, or real life connections
Source: Wikipedia
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What are (Online) Social Networks?
• Social networks are graphs of people
– Graph edges connect friends
– `Friend’ has different implications
– How hard is it to be Facebook `friends’?
• Online social networking
– Social network hosted by a Web site
– Friendship represents shared interest or trust
– Online friends may have never met
Friendship Establishment
• Facebook – befriend me
• Twitter – I follow you;
you follow me
• Flickr – ‘just post it’
http://soshable.com/twitter-vs-facebook-across-the-web/
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Social Networks
• Links denote a social interaction
– Networks of acquaintances
– collaboration networks
• actor networks
• co-authorship networks
• director networks
–
–
–
–
–
–
phone-call networks
e-mail networks
Bluetooth networks
sexual networks
home page/blog networks
…
Popular social networking sites
•
•
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•
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Art – devianART
General – Facebook, Google+, Qzonr
Microblogging – Twitter, Reddit, Sina, Tumblr
Movies – flickster, YouTube
Music – last.fm, Vkontakte
Personal sites – Myspace, Mylife, Cyworld
Photos/pictures – Flickr, Instagram, Pinterest
Professional – LinkedIn, Academia
Relationship initiation – Friendster
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Social Network Usage
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Social Media is
• Consumer generated media It is media that is
designed to be shared, sharing means that it is
easy to comment on, that it is easy to send,
there are no costs associated with viewing the
media and last but not least it is always
available.
• Social media enables people to share
information with friends and colleges using
the Internet
Social Networking
Friendship
• Keeping in
Touch
• Developing
new
relationships
Sharing
• Photos
• Links
• Interests
Community
• Causes
• Beliefs
• Advocacy
Social Network Statistics
• Facebook
– Worldwide, there are over 1.19 billion
active Facebook users
•
Source: Facebook
– 4.5 billion likes generated daily as of May
2013 which is a 67 percent increase from
August 2012
•
Source: Facebook
– There are 874 million mobile active users
which is a 45 percent increase from 2012
•
Source: Facebook
– 50% of 18-24 year-olds go on Facebook
when they wake up
•
Source: The Social Skinny
– One in five page views in the United States
occurs on Facebook
•
Source: Infodocket 2012
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Social Network Statistics
• Twitter
– 230+ million monthly active
users
– 500 million Tweets are sent per
day
– 76% of Twitter active users are
on mobile
• Google+
– ~ 540 million registered users,
300 million people active in
stream
– Over 1.5 Billion photos uploaded
every week to Google+ photos
• Linkedin
– More than 259 million members
in over 200 countries
– Professionals are signing up to
join LinkedIn at a rate of more
than two new members per
second
• Instagram
– Over 100 million users,
– total, 40 million photos are
uploaded to Instagram every
single day according to a report
by Nielsen.
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Online social network use
• Fixed broadband (Sandvine Q1 2014)
• YouTube 5.5% upload, 13.2% down
• Facebook 2.2% upload, 2.0% down
• Popular with users on the go
– Mobile (Sandvine Q1 2014)
• YouTube 3.8% up, 17.6% down
• Facebook 27.0% up, 14.0% down
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Social Networks
• Not a new concept, (6 degrees of separation)
• People typically maintain 10-20 close
relationships among thousands of
acquaintances
• The vast majority of people report the opinion
they trust most is from ‘someone like me’.
– For the first time in our history, peers have bested
the wisdom of experts
Why are social networks interesting?
• Popular way to connect
– Estimated 1.32B users online each day
– Average American spends 40 minutes/day on the
site
• Changing the flow of information
– Formerly few ``writers’’ many ``readers’’ online
– Now anyone can write!
– What does this mean for Internet traffic?
• Useful in times of disaster
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Social networks: Interdisicplinary Field
• social network analysis is an interdisciplinary social science;
– Sociologists, computer scientists, physicists and mathematicians have
made large contributions to understanding networks in general (as
graphs) and thus contributed to an understanding of social networks
• [Social network analysis] is grounded in the observation that
social actors [i.e., people] are interdependent and that the links
[i.e., relationships] among them have important consequences
for every individual [and for all of the individuals together]. ...
[Relationships] provide individuals with opportunities and, at
the same time, potential constraints on their behavior. ... Social
network analysis involves theorizing, model building and
empirical research focused on uncovering the patterning of
links among actors. It is concerned also with uncovering the
antecedents and consequences of recurrent patterns.
Linton C. Freeman
Social Network Examples
• Effects of urbanization on individual wellbeing
• World political and economic system
• Community elite decision-making
• Social support, Group problem solving
• Diffusion and adoption of innovations
• Belief systems, Social influence
• Markets, Sociology of science
• Exchange and power
• Email, Instant messaging, Newsgroups
• Co-authorship, Citation, Co-citation
• SocNet software, Friendster
• Blogs and diaries, Blog quotes and links
Social Networks Basic Questions
• Balance: important in exchange networks
– In a two-person network (dyad), exchange of goods, services and cash
should be balanced.
– More generally, exchanges of “favors” or “support” are likely to be
quite balanced.
• Role: what role does the actor perform in the network?
– Role is defined in terms of Actors’ neighborhoods.
– The neighborhood is the set of ties and actors connected directly to
the current actor.
– Actors with similar or identical neighborhoods are assigned the same
role.
• Paradigm: interchangability. Actors with the same role are
interchangable in the network.
Social Networks Basic Questions
• Prestige: How important is the actor in the network?
– Related notions are status and centrality.
• Centrality reifies the notion of “peripheral vs. central
participation” from communities of practice.
– Key notions of centrality were developed in the 1970’s, e.g.
“eigenvalue centrality” by Bonacich.
• Most of these measures were rediscovered as quality
measures for web pages:
– Indegree
– Pagerank = eigenvalue centrality
– HITS ?= two-mode eigenvalue centrality
How are links distributed
Mislove et al. 2007
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User relationships on Twitter
• Broadcasters
• News outlets, radio
stations
• No reason to follow
anyone
• Post playlists,
headlines
Mislove et al. 2007
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User relationships on Twitter
• Acquaintances
• Similar number of
followers and
following
• Along the diagonal
• Green portion is top
1-percentile of
tweeters
Mislove et al. 2007
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User relationships on Twitter
• Miscreants?
• Some people follow
many users
(programmatically)
• Hoping some will
follow them back
• Spam, widgets,
celebrities (at top)
Mislove et al. 2007
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On User Arrival - MySpace
 What does user ID say about account creation time?

Plot user ID vs. last login of that user for all our users
Public users
Torkjazi et al 2009
Private users
On User Arrival - MySpace
• 32% of public and 18% of private users are tourists
• Discovery of “tourists” enables accurate estimation
of user account creation time based on their
associated user ID
Tourists
“Clean edge”
=
users whose last login
is shortly after their
account creation time
=
“MySpace tourists”
Torkjazi et al 2009
On User Departure - MySpace
 Are newer users more likely to leave than older ones?
 More public and private profiles
in the first half of ID space
 More invalid profiles in the
second half of ID space
 Users joining the system earlier have been more likely to keep
their accounts than newer users
Torkjazi et al 2009
MySpace Life Cycle
Possible reasons behind MySpace’s decline?
• Slow-down in the growth
rate of MySpace is related
to emergence of Facebook
• Informal evidence
(Alexa.com): Daily accesses
to Facebook surpassed that
of MySpace, at around April
2008
Torkjazi et al 2009
Categories of pages
Schneider et al 2009
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Session Characteristics
Schneider et al 2009
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HTTP Traces
Schneider et al 2009
Action popularity
Schneider et al 2009
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Feature sequences
Schneider et al 2009
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Types and Amounts of Info. Disclosed
Gross et al 2005
Picture Posting Pattern
1000
Photo Size (KB)
100
10
1
1
Erdin et al 2014
10
100
Number of posts
1000
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Video Posting Pattern
100000
Video Size (KB)
10000
1000
100
10
1
10
Number of posts
100
Erdin et al 2014
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Non-Multimedia Post Frequency
Number of Non-Multimedia Posts
Posting Events
100
10
1
55
60
65
70
75
80
85
Number of Online Friends
90
95
100
Erdin et al 2014
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Multimedia Data to Download
As the time between logins increases, the total amount of data the user might download from
friends increases. In extreme cases, it is observed 1GB of data when the user has not logged in for
about a day.
Photo and Video PostsBetweenLogins
1000
TotalSize(MB)
100
10
1
0.1
0.01
0.010.1110
Erdin et al 2014
Time between Logins(Hours)
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OSNs: Wrap up
• Many different types of OSNs
– Photos, video, profile-based
• Some extremely popular source of much Internet
traffic
– Facebook, YouTube
• New ones emerging
– Instagram, snapchat
• Old ones fading
– MySpace, Friendster
• Studying their properties can inform how we build
networks and systems to support them!
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