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.
![Page 1: ECE 424 Embedded Systems Design Networking Connectivity Chapter 12 Ning Weng.](https://reader035.fdocuments.us/reader035/viewer/2022062408/56649e2f5503460f94b1f8b7/html5/thumbnails/1.jpg)
ECE 424 Embedded Systems
Design
Networking ConnectivityChapter 12Ning Weng
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ECE 424 2
Networking Overview• Goal: key concepts and system details to
integrate network connectivity into embedded systems
Ning Weng
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ECE 424 3
Global Internet Bandwidth
Ning Weng
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ECE 424 4
UDP Packet Sender
Ning Weng
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ECE 424 5
UDP Packet Sender in C
Ning Weng
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ECE 424 6
Socket API
Ning Weng
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ECE 424 7
Protocol Layers
Ning Weng
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ECE 424 8
IP Layer Packet Headers
Ning Weng
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9
Comparison: IPv4&6 header
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ECE 424 10
Transport Layer Headers
Ning Weng
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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.”
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TCP Window Increase/Decrease
Transmission no
Threshold
Threshold
Congestion window
The initial doubling of thewindow size is called “slowstart”.
Timeout
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ECE 424 13
Encapsulation
Ning Weng
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ECE 424 14
Example of Switched Ethernet LAN
Ning Weng
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ECE 424 15
Ethernet Frame Format
Ning Weng
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ECE 424 16
Ethernet Controller
Ning Weng
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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
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ECE 424 18
IEEE 802.11 Data Frame
Ning Weng
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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.
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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
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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.
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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.
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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.
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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
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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
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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
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ECE 424 28
Linux Networking• Networking utilities
─ Ipcofig─ Netstat
• Socket implementations
• Networking kernel structures
Ning Weng
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ECE 424 29
Linux Network Stack
Ning Weng
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ECE 424 30
Struct SK_buff
Ning Weng