Summer Workshop on Cyber Security

Computer Networks Security (Part 1)

Dr. Hamed Mohsenian-Rad

University of California at Riverside and Texas Tech UniversityJuly 14- 18, 2014

Supported by National Science Foundation

2Summer Workshop on Cyber Security July 14 - 18 , 2014 – Network Security, UCR & TTU

Internet: Millions of connected computing devices:

• End systems / Hosts (Running Net Apps)

• Communication Links (Wired or Wireless)

• Routers and Switches (Forward “Packets”)

mobile network

global ISP

regional ISP

home network

institutional network

Overview of Computer Networks

3Summer Workshop on Cyber Security July 14 - 18 , 2014 – Network Security, UCR & TTU

Network of Networks• ISPs• Institutional Networks• Home Networks• Mobile Networks

Internet Protocols: • Control Sending & Receiving of Messages

• E.g.: TCP, IP, HTTP, 802.11

mobile network

global ISP

regional ISP

home network

institutional network

Overview of Computer Networks

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What is a Protocol?

Summer Workshop on Cyber Security July 14 - 18 , 2014 – Network Security, UCR & TTU

Human Protocol: • “What time is it?”, “I have a question.”, …

Network Protocols: • Machines instead of humans.

Protocols define format and order of messages sent and received among network entities, and actions taken on message transmission and message receipt.

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What is a Protocol?

Summer Workshop on Cyber Security July 14 - 18 , 2014 – Network Security, UCR & TTU

Protocols define the interaction sequences over time:

Hi

Hi

Got thetime?2:00

TCP connectionresponse

Get http://www.awl.com/kurose-ross

<file>Time

TCP connectionrequest

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Protocol Layers

Summer Workshop on Cyber Security July 14 - 18 , 2014 – Network Security, UCR & TTU

Networks are complex with many “pieces”: • Hosts• Routers• Wired Links • Wireless Links• Applications• Protocols• Hardware• Software• …

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Protocol Layers

Summer Workshop on Cyber Security July 14 - 18 , 2014 – Network Security, UCR & TTU

Networks are complex with many “pieces”: • Hosts• Routers• Wired Links • Wireless Links• Applications• Protocols• Hardware• Software• …

Q: How can we organize the structure of networks?

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Example: Organization of Air Travel

Summer Workshop on Cyber Security July 14 - 18 , 2014 – Network Security, UCR & TTU

A series of steps are taken at different “layers” :

ticket (purchase)

baggage (check)

gates (load)

runway takeoff

airplane routing

ticket (complain)

baggage (claim)

gates (unload)

runway landing

airplane routing

airplane routing

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Example: Organization of Air Travel

Summer Workshop on Cyber Security July 14 - 18 , 2014 – Network Security, UCR & TTU

Each layer implements a “service”:

Via its own “internal-layer” actions.

ticket (purchase)

baggage (check)

gates (load)

runway (takeoff)

airplane routing

departureairport

arrivalairport

intermediate air-trafficcontrol centers

airplane routing airplane routing

ticket (complain)

baggage (claim

gates (unload)

runway (land)

airplane routing

ticket

baggage

gate

takeoff/landing

airplane routing

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Internet Protocol Stack

Summer Workshop on Cyber Security July 14 - 18 , 2014 – Network Security, UCR & TTU

Application

Transport

Network

Link

Physical

There are five layers in Internet Protocol Stack with different functionalities and protocols.

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Internet Protocol Stack

Summer Workshop on Cyber Security July 14 - 18 , 2014 – Network Security, UCR & TTU

Application: Supporting network apps FTP, HTTP, SMTP, Skype

Application

Transport

Network

Link

Physical

12

Internet Protocol Stack

Summer Workshop on Cyber Security July 14 - 18 , 2014 – Network Security, UCR & TTU

Application: Supporting network apps FTP, HTTP, SMTP, Skype

Application

Transport

Network

Link

Physical

13

Internet Protocol Stack

Summer Workshop on Cyber Security July 14 - 18 , 2014 – Network Security, UCR & TTU

Application: Supporting network apps FTP, HTTP, SMTP, Skype

Application

Transport

Network

Link

Physical

14

Internet Protocol Stack

Summer Workshop on Cyber Security July 14 - 18 , 2014 – Network Security, UCR & TTU

Application: Supporting network apps FTP, HTTP, SMTP, Skype

Transport: Process-to-process data transfer TCP, UDP

Application

Transport

Network

Link

Physical

15

Internet Protocol Stack

Summer Workshop on Cyber Security July 14 - 18 , 2014 – Network Security, UCR & TTU

Application: Supporting network apps FTP, HTTP, SMTP, Skype

Transport: Process-to-process data transfer TCP, UDP

Application

Transport

Network

Link

PhysicalThey all use TCP Protocol for “reliable” data transmission. (Socket Programming) (Each socket has a port #)

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Internet Protocol Stack

Summer Workshop on Cyber Security July 14 - 18 , 2014 – Network Security, UCR & TTU

Application: Supporting network apps FTP, HTTP, SMTP, Skype

Transport: Process-to-process data transfer TCP, UDP

Network: Routing from source to destination IP, Routing Protocols

Application

Transport

Network

Link

Physical

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Internet Protocol Stack

Summer Workshop on Cyber Security July 14 - 18 , 2014 – Network Security, UCR & TTU

Application: Supporting network apps FTP, HTTP, SMTP, Skype

Transport: Process-to-process data transfer TCP, UDP

Network: Routing from source to destination IP, Routing Protocols

Application

Transport

Network

Link

Physical

18

Internet Protocol Stack

Summer Workshop on Cyber Security July 14 - 18 , 2014 – Network Security, UCR & TTU

Application: Supporting network apps FTP, HTTP, SMTP, Skype

Transport: Process-to-process data transfer TCP, UDP

Network: Routing from source to destination IP, Routing Protocols

Application

Transport

Network

Link

Physical

19

Internet Protocol Stack

Summer Workshop on Cyber Security July 14 - 18 , 2014 – Network Security, UCR & TTU

Application: Supporting network apps FTP, HTTP, SMTP, Skype

Transport: Process-to-process data transfer TCP, UDP

Network: Routing from source to destination IP, Routing Protocols

Link: Routing from source to destination Ethernet, IEEE 802.11 (WiFi)

Application

Transport

Network

Link

Physical

20

Internet Protocol Stack

Summer Workshop on Cyber Security July 14 - 18 , 2014 – Network Security, UCR & TTU

Application: Supporting network apps FTP, HTTP, SMTP, Skype

Transport: Process-to-process data transfer TCP, UDP

Network: Routing from source to destination IP, Routing Protocols

Link: Routing from source to destination Ethernet, IEEE 802.11 (WiFi)

Application

Transport

Network

Link

Physical

21

Internet Protocol Stack

Summer Workshop on Cyber Security July 14 - 18 , 2014 – Network Security, UCR & TTU

Application: Supporting network apps FTP, HTTP, SMTP, Skype

Transport: Process-to-process data transfer TCP, UDP

Network: Routing from source to destination IP, Routing Protocols

Link: Routing from source to destination Ethernet, IEEE 802.11 (WiFi)

Physical: Bit-by-bit transmission

Application

Transport

Network

Link

Physical

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Packets

Summer Workshop on Cyber Security July 14 - 18 , 2014 – Network Security, UCR & TTU

Network communications are essentially 0-1 bit streams:

But we break down bit streams to small bit chunks = packets.

The packet at each layer:

Can have different names (frame, segment, etc.)

Can have different sizes

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Packets

Summer Workshop on Cyber Security July 14 - 18 , 2014 – Network Security, UCR & TTU

Application

Transport

Network

Link

Physical

Application

Transport

Network

Link

Physical

Message

Segment

Datagram

Frame

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Packet Headers

Summer Workshop on Cyber Security July 14 - 18 , 2014 – Network Security, UCR & TTU

Protocol at each layer adds its own “headers” for “control data”.

Application

Transport

Network

Link

Physical

25

Packet Headers

Summer Workshop on Cyber Security July 14 - 18 , 2014 – Network Security, UCR & TTU

Protocol at each layer adds its own “headers” for “control data”.

Application

Transport

Network

Link

Physical

Message

26

Packet Headers

Summer Workshop on Cyber Security July 14 - 18 , 2014 – Network Security, UCR & TTU

Protocol at each layer adds its own “headers” for “control data”.

Application

Transport

Network

Link

Physical

Message HT

Used by TCP and UDP

Segment

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Packet Headers

Summer Workshop on Cyber Security July 14 - 18 , 2014 – Network Security, UCR & TTU

Protocol at each layer adds its own “headers” for “control data”.

Application

Transport

Network

Link

Physical

Message HT HN

Used by IP, Routing

Datagram

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Packet Headers

Summer Workshop on Cyber Security July 14 - 18 , 2014 – Network Security, UCR & TTU

Protocol at each layer adds its own “headers” for “control data”.

Application

Transport

Network

Link

Physical

Message HT HN HL

Used by Ethernet, …

Frame