ECE 424 Embedded Systems Design Networking Connectivity Chapter 12 Ning Weng

Networking Overview Goal: key concepts and system details to integrate network connectivity into embedded systems Ning WengECE 4242

Global Internet Bandwidth Ning WengECE 4243

UDP Packet Sender Ning WengECE 4244

UDP Packet Sender in C Ning WengECE 4245

Socket API Ning WengECE 4246

Protocol Layers Ning WengECE 4247

IP Layer Packet Headers Ning WengECE 4248

9 Comparison: IPv4&6 header

Transport Layer Headers Ning WengECE 42410

TCP connections  This diagram shows the start of a TCP connection. A sends packet X with SYN. “Hello I would like to talk”. B sends a SYN, ACK pair “I got your message. I would also like to talk” A sends an ACK (and some data) “I got your message, here is some data.”

TCP Window Increase/Decrease Transmission no Threshold Congestion window The initial doubling of the window size is called “slow start”. Timeout

Encapsulation Ning WengECE 42413

Example of Switched Ethernet LAN Ning WengECE 42414

Ethernet Frame Format Ning WengECE 42415

Ethernet Controller Ning WengECE 42416

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 WengECE 42417

IEEE Data Frame Ning WengECE 42418

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 i standard. Provides government level security. Also available in two versions: ─ WPA2 Personal. ─ WPA2 Enterprise.

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 WengECE 42424

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 is working on standardizing the PHY and MAC layers in Bluetooth More Info: ─ ─

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.

27 Application Framework and Support Link Manager and L2CAP Radio & Baseband Host Controller Interface RF Baseband Audio Link Manager L2CAP OtherTCSRFCOMM Data The Bluetooth protocols A hardware/software description An application framework SDP Applications Control

Linux Networking Networking utilities ─ Ipcofig ─ Netstat Socket implementations Networking kernel structures Ning WengECE 42428

Linux Network Stack Ning WengECE 42429

Struct SK_buff Ning WengECE 42430