ECE 424 Embedded Systems Design Networking Connectivity Chapter 12 Ning Weng.
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Transcript of ECE 424 Embedded Systems Design Networking Connectivity Chapter 12 Ning Weng.
ECE 424 Embedded Systems
Design
Networking ConnectivityChapter 12Ning Weng
ECE 424 2
Networking Overview• Goal: key concepts and system details to
integrate network connectivity into embedded systems
Ning Weng
ECE 424 3
Global Internet Bandwidth
Ning Weng
ECE 424 4
UDP Packet Sender
Ning Weng
ECE 424 5
UDP Packet Sender in C
Ning Weng
ECE 424 6
Socket API
Ning Weng
ECE 424 7
Protocol Layers
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ECE 424 8
IP Layer Packet Headers
Ning Weng
9
Comparison: IPv4&6 header
ECE 424 10
Transport Layer Headers
Ning Weng
TCP connections
This diagram shows the start of a TCP connection.
A sends packet X withSYN. “Hello I would like to talk”.B sends a SYN, ACKpair “I got yourmessage. I wouldalso like to talk”A sends an ACK (andsome data) “Igot your message,here is some data.”
TCP Window Increase/Decrease
Transmission no
Threshold
Threshold
Congestion window
The initial doubling of thewindow size is called “slowstart”.
Timeout
ECE 424 13
Encapsulation
Ning Weng
ECE 424 14
Example of Switched Ethernet LAN
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ECE 424 15
Ethernet Frame Format
Ning Weng
ECE 424 16
Ethernet Controller
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ECE 424 17
WI-FI• Short of wireless fidelity
─ Dominant wireless LAN technologies─ Relying on availability of unlicensed radio frequency
• High f -> affected by various medium• Security: dos, unauthorized access and etc.• Wireless medium access control
Ning Weng
ECE 424 18
IEEE 802.11 Data Frame
Ning Weng
Basic Security Strategies• Block your Service Set Identifier (SSID) from being
broadcast.─ Wireless beacon so PCs can easily find the access point.
• Change the default network name in the access point.
• Change the default access point password.• Center the access point in the middle of the
building/house.
Media Access Control (MAC) Filtering
• Every network device has a unique MAC address─ Allocated by the manufacturer.
• MAC Filtering only allows certain addresses access.
• Mostly for home use.─ Tedious to implement on a large scale
Wired Equivalency Protocol (WEP)
• Basic encryption technology.─ Uses an RC4 stream cipher.
• Pseudo-random bytes.─ Two versions: 64-bit and 128-bit versions.
• Built into Wi-Fi certified equipment.─ Implemented at the MAC level.
• Protects radio signal between device and access point.─ Does not protect data beyond the access point.
• Uses static encryption keys.─ Easy to crack.
• Still better then nothing.
Wi-Fi Protected Access (WPA)• Designed to replace WEP.
─ Firmware update. ─ 128-bit Temporal Key Integrity Protocol (TKIP)
encryption. • Uses a master key that is regularly changed.
─ User authentication.─ Data Integrity.
• Protects radio signal between device and access point.
• Built into Wi-Fi certified equipment.─ Implemented at the MAC level.
• Available in two versions:─ WPA2 Personal.─ WPA2 Enterprise.
Wi-Fi Protected Access 2 (WPA2)
• Designed to replace WEP.─ 128-bit Advanced Encryption Standard (AES).
• Based on the IEEE 802.11i standard.• Provides government level security.• Also available in two versions:
─ WPA2 Personal.─ WPA2 Enterprise.
ECE 424 24
Wireless Media Access Control
• MAC protocol: shared media scheduling• maximize number of communications• Ensure fairness among all transmitters
• CSMA – carrier sensing multiple access• CD – collision detection
─ If (Transmitted_Signal != Sensed_Signal) Sender knows it’s a Collision ABORT
• Wireless problem─ Can not send and listen ─ Signal not same at same
Ning Weng
25
Bluetooth Overview• Bluetooth is a global, RF-based (ISM
band: 2.4 GHz), short-range, connectivity solution for portable, personal devices─ it is not just a radio, it is an end-to-end solution
• The Bluetooth spec comprises─ a HW & SW protocol specification─ usage case scenario profiles and interoperability
requirements
• IEEE 802.15.1 is working on standardizing the PHY and MAC layers in Bluetooth
• More Info:─ http://www.bluetooth.org ─ http://ieee802.org/15/pub/TG1.html
Bluetooth - Piconet• A collection of devices connected via
Bluetooth technology in an ad hoc fashion. • A piconet starts with two connected
devices, and may grow to eight connected devices.
• All Bluetooth devices are peer units and have identical implementations. However, when establishing a piconet, one unit will act as a Master and the other(s) as slave(s) for the duration of the piconet connection.
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Application Framework and Support
Link Manager and L2CAP
Radio & Baseband
Host Controller Interface
RF
Baseband
AudioLink Manager
L2CAP
Other TCS RFCOMM
Data
The Bluetooth protocols
• A hardware/software description• An application framework
SDP
Applications
Control
ECE 424 28
Linux Networking• Networking utilities
─ Ipcofig─ Netstat
• Socket implementations
• Networking kernel structures
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ECE 424 29
Linux Network Stack
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ECE 424 30
Struct SK_buff
Ning Weng