2015-09-20
Computer networking (TDDD63): Part 1 …
Kick starting science ...
Niklas Carlsson, Associate Professor
http://www.ida.liu.se/~nikca/
What do you have in the future?
What do you have in the future?
How does it keep going?
… well, cable into wall …
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2015-09-20
What happens there?
What happens there?
Or maybe more realistically …
• Work at company …
How do we build services that are …
Efficient
Secure
Important problem faced every day
by many companies, including …
Reliable
1-12
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In the computer network part we
will look at things such as …
How do we communicate with a
machine across the world?
How do we find a path?
How do we build scalable, efficient,
secure, and reliable services?
How do we find out who to talk to?
How do we avoid sending too much for
the receiver and network to handle?
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What happens at our machine? Inside the
network? Along the path?
What happens at our machine? Inside the
network? Along the path?
Roadmap
So let’s start the lecture …
Roadmap
• What is the Internet?
• Network Edge
• End systems, access networks, links
• Network Core
• Packet switching, network structure
• Protocol Layers, service models
• Network Security
• History
What’s the Internet: “Nuts and Bolts View”
• What is the Internet?
• Network Edge
• End systems, access networks, links
• Network Core
• Packet switching, network structure
• Protocol Layers, service models
• Network Security
• History
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2015-09-20
What’s the Internet: “Nuts and Bolts View”
What’s the Internet: “Service View”
Today’s service/company landscape include ...
Today’s service/company landscape include ...
1-27
Today’s service/company landscape include ...
1-28
Today’s service/company landscape include ...
Network operators
Equipment manufacturers
(also sell services and help
Operate networks)
Equipment manufacturers
(also sell services and help
Operate networks)
1-29
1-30
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Today’s service/company landscape include ...
Today’s service/company landscape include ...
Content delivery networks
Enterprise solutions
and network service
(e.g., data center
solutions and cloud
1-31
providers)
Enterprise solutions
and network service
(e.g., data center
solutions and cloud
1-32
providers)
Today’s service/company landscape include ...
End user services (e.g.,
web-based social
networks, search,
communication, and
streaming)
Some common applications today …
•
•
•
•
•
•
•
•
•
•
World Wide Web (WWW)
Remote login (telnet, rlogin, ssh)
File transfer
Peer-to-peer file sharing
Cloud computing/services
Instant messaging (chat, text messaging, etc.)
Live and video-on-demand streaming
Internet phone (Voice-Over-IP)
Distributed games
…
34
1-33
… and tomorrow
Today’s end hosts …
The 2020 vision
 Everything that can be connected will be connected
 50B devices (perhaps more like 500B ...)
 IoT and smart cities
 Machine-to-machine
 High-definition 3D streaming to heterogeneous clients
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2015-09-20
… and tomorrow’s
Internet of Things!
Roadmap
A Closer Look at Network Structure
• What is the Internet?
• Network Edge
• End systems, access networks, links
• Network Core
• Packet switching, network structure
• Protocol Layers, service models
• Network Security
• History
Access Networks and Physical Media
Access Net: Digital Subscriber Line (DSL)
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Access Net: Cable Network
Access Net: Home Network
Enterprise Access Networks (Ethernet)
Wireless Access Networks
Host: Sends Packets of Data
Physical Media
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Physical Media: Radio
Roadmap
• What is the Internet?
• Network Edge
• End systems, access networks, links
• Network Core
• Packet switching, network structure
• Protocol Layers, service models
• Network Security
• History
The Network Core
Packet Switching: Queueing Delay, Loss
Packet-Switching: Store-and-forward
Two Key Network Functions
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Internet Structure: Network of Networks
Internet Structure: Network of Networks
Internet Structure: Network of Networks
Internet Structure: Network of Networks
Internet Structure: Network of Networks
Internet Structure: Network of Networks
Tier 1 ISPs
IXP- 3rd party company sets up an
exchange point where multiple ISPs
can peer together (about 300 IXPs)
Peering Link - all traffic between two ISPs
travels through one direct connection
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Internet Structure: Network of Networks
Internet Structure: Network of Networks
Internet Structure: Network of Networks
Tier-1 ISP: Sprint
Google private network bypasses Google has over 50 data centers some with
upper tiers by peering with lower tiers over 100,000 servers, all interconnected via
directly
Googles private TCP/IP network
Roadmap
POP: ISP to ISP
connections
Sets of routers in the provider’s network
where customer ISPs can connect into provider ISP
What’s a Protocol?
• What is the Internet?
• Network Edge
• End systems, access networks, links
• Network Core
• Packet switching, network structure
• Protocol Layers, service models
• Network Security
• History
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What’s a Protocol?
What’s a Protocol?
A Human
Protocol
Web
A Human
Protocol
What's a Protocol?
Protocol “Layers”
Problem Scenario
More Problems
Email
Bittorrent
VoIP
Bittorrent
802.11
Bluetooth
Cellular
Bittorrent
Application endpoints
may not be on the
same media
•This is a nightmare scenario
•Huge amounts of work to add new apps or media
•Limits growth and adoption
Ethernet
A Computer
Network Protocol
Ethernet
802.11
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Solution: Use Indirection
Web
Email
Bittorrent
VoIP
Layers, Protocols, Interfaces
•
Networks organized as a stack of layers
•
API
•O(1)
work toNetwork
add newAbstraction
apps, media
Magical
Layer
API limitsAPI
•Few
on new API
technology
Ethernet
802.11
Bluetooth
•
•
•
Offer services to the layer above it using a welldefined interface (programming language analogy:
libraries hide details while providing a service)
Reduces design complexity
Protocols: Logical “horizontal” conversations at any
layer (between peers)
Data Transfer: each layer passes data & control
information over the interfaces (between neighboring
layers)
Cellular
Internet Protocol Stack
The Hourglass
HTTP, FTP, RTP, IMAP, Jabber, …
TCP, UDP, ICMP
IPv4
Ethernet, 802.11x, DOCSIS, …
Fiber, Coax, Twisted Pair, Radio, …
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Layering: logical communication
Layering: logical communication
application
transport
network
link
physical
application
transport
network
link
physical
network
link
physical
application
transport
network
link
physical
application
transport
network
link
physical
data
application
transport
transport
network
link
physical
application
transport
network
link
physical
ack
data
network
link
physical
application
transport
network
link
physical
data
application
transport
transport
network
link
physical
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Layering: physical communication
Encapsulation: Layering and data
data
application
transport
network
link
physical
application
transport
network
link
physical
Each layer takes data from above
•
•
network
link
physical
application
transport
network
link
physical
adds header information to create new data unit
passes new data unit to layer below
M
data
application
transport
network
link
physical
source
destination
application
transport
network
link
physical
application
transport
network
link
physical
Encapsulation: Layering and data
Encapsulation: Layering and data
Each layer takes data from above
Each layer takes data from above
•
•
•
•
adds header information to create new data unit
passes new data unit to layer below
source
M
Ht M
application
transport
network
link
physical
adds header information to create new data unit
passes new data unit to layer below
destination
application
transport
network
link
physical
message
segment
M
Ht M
Hn Ht M
source
destination
application
transport
network
link
physical
application
transport
network
link
physical
Encapsulation: Layering and data
Encapsulation: Layering and data
Each layer takes data from above
Each layer takes data from above
•
•
•
•
adds header information to create new data unit
passes new data unit to layer below
M
Ht M
Hn Ht M
Hl Hn Ht M
source
destination
application
transport
network
link
physical
application
transport
network
link
physical
segment
datagram
frame
message
segment
datagram
adds header information to create new data unit
passes new data unit to layer below
source
message
message
M
Ht M
Hn Ht M
Hl Hn Ht M
application
transport
network
link
physical
destination
application
transport
network
Hl Hn Ht M
link
physical
message
segment
datagram
frame
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2015-09-20
Encapsulation: Layering and data
Encapsulation: Layering and data
Each layer takes data from above
Each layer takes data from above
•
•
•
•
adds header information to create new data unit
passes new data unit to layer below
source
M
Ht M
Hn Ht M
Hl Hn Ht M
passes new data unit to layer below
source
destination
application
transport
network
link
physical
application
transport
Hn Ht M
network
link
Hl Hn Ht M
physical
message
segment
datagram
frame
M
Ht M
Hn Ht M
Hl Hn Ht M
application
transport
network
link
physical
Encapsulation
Encapsulation: Layering and data
destination
application
Ht M
transport
Hn Ht M
network
link
Hl Hn Ht M
physical
message
segment
datagram
frame
Each layer takes data from above
•
•
Each layer takes data from above
•
•
adds header information to create new data unit
adds header information to create
new data unit
passes new data unit to layer below
adds header information to create new data unit
passes new data unit to layer below
source
M
Ht M
Hn Ht M
Hl Hn Ht M
destination
application
transport
network
link
physical
application
Ht
transport
Hn Ht
network
link
Hl Hn Ht
physical
M
message
M
segment
M
datagram
M
frame
Roadmap
• What is the Internet?
• Network Edge
• End systems, access networks, links
• Network Core
• Packet switching, network structure
• Protocol Layers, service models
• Network Security
• History
Network Security


field of network security
 how bad “entities” can attack computer networks
 how we can defend networks against attacks
 how to design architectures that are immune to
attacks
Internet not originally designed with (much) security
in mind
 original vision: “a group of mutually trusting users
attached to a transparent network” 
 Internet protocol designers playing “catch-up”
 security considerations in all layers!
Introduction 1-90
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Bad guys/girls/organizations (“entities”):
can put malware into hosts via Internet
Denial of Service (DoS): attackers make resources
(server, bandwidth) unavailable to legitimate traffic by
overwhelming resource with bogus traffic

malware can get in host from a virus, worm, or
Trojan horse.

spyware malware can record keystrokes, web sites
visited, upload info to collection site.

infected host can be enrolled in botnet, used for
spam and DDoS attacks.

Bad “entities” can attack servers and
network infrastructure
1. select target
2. break into hosts around the
network (see botnet)
3. send packets to target from
compromised hosts
target
malware often self-replicating: from one infected
host, seeks entry into other hosts
Introduction 1-91
Introduction 1-92
Bad “entities” can use false source
addresses
Bad “entities” can “sniff”
IP spoofing: send packet with false source address
Broadcast medium allow packet
sniffers (in promiscuous mode)
to listen to packets to others
C
A
C
A
src:B dest:A
payload
B
src:B dest:A
payload
B
Introduction 1-93
Bad “entities” can record and playback
record-and-playback: sniff sensitive info (e.g.,
password), and use later
C
A
src:B dest:A
user: B; password: foo
B
… AND lots more …
Introduction 1-94
Roadmap
• What is the Internet?
• Network Edge
• End systems, access networks, links
• Network Core
• Packet switching, network structure
• Protocol Layers, service models
• Network Security
• History
Introduction 1-95
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Internet History
Internet History
Internet History
Internet History
DNS - Domain Name Server
Internet History
Internet History
2,9 billion users 2014 ??
2,7 billion users 2013
2,9 billion users 2014 ??
2,7 billion users 2013
1.23 billion users2014
1.11 billion users March 2013
1.23 billion users2014
1.11 billion users March 2013
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2015-09-20
Extra slides ...
Internet Hosts 1981-2013
Number of hosts
advertised in the DNS
July 2012: 908,585,739
July 2013: 996,230,757
July 2014: 1,028,544,414
Sweden: Host #
2014: 5,891,385
2004
2005
2006
2008
2010
Sweden 945 221 2 701 456 2 958 000 3 579 000 5 727 000
2012
Sweden: 5,727,000
2011 Country Rank: 18
2014: 9,723,809 users
Rank: 44+ 94,8% penetration!
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