臺灣博碩士論文加值系統

在今日，越來越多的使用者透過行動裝置使用無線網路。越來越多的咖啡廳、學校、飯店以及其他業者提供無線上網的服務。在咖啡廳和商店這類型小型無線熱點的服務中，透過本論文提出的存取控制閘道器來維持無線網路的服務是一個好的解決方案，因為它成本低且方便管理。即使是學校這類型較大規模的無線熱點，也可透過多個存取控制閘道器搭配WiNOC管理系統，達到理想的網路服務品質。

本篇論文描述如何在OpenWrt平台上實作一個無線網路熱點的存控制閘道器。此存取控制閘道器具有(1)RADIUS client功能可與RADIUS server溝通；(2)captive portal機制控管使用者；(3)DDNS client功能方便連結這些動態IP位址的機器。除此之外，為了讓使用者可以更方便迅速的存取網路，此閘道器也加入IP Plug and Play的功能。

Wireless Networks have been widely used by people with mobile device or laptop nowadays. There are more and more coffee shops, universities, hotels, and other business that provide services of accessing the Internet via wireless LAN. In the small-scale hotspot, like coffee shops and store, using common access gateway to provide service will be a good choice because of low cost and ease to construct.

In this thesis we will describe how to implement a wireless hotspot access control gateway under the OpenWrt platform. This gateway will have (1) RADIUS client to communicate with RADIUS server, (2) captive portal mechanism to strengthen access control, (3) dynamic DNS client to be easily connected and managed without the inconvenience of dynamic IP address. And it will also have SSH connectivity and web page GUI to be configured and managed via Internet. In addition, IP PnP (IP plug and play) will be in the gateway for convenience of use.

CHAPTER1 INTRODUCTION 1
1.1 BACKGROUND AND MOTIVATION 1
1.2 GOAL 3
1.3 THESIS OUTLINE 4
CHAPTER 2 BACKGROUND AND RELATED WORKS 6
2.1 RADIUS 6
2.2 CAPTIVE PORTAL 8
2.3 DYNAMIC DNS 10
2.4 IP PLUG AND PLAY 12
2.5 PACKET FORWARDING 12
2.6 WINOC MANAGEMENT SYSTEM 14
CHAPTER 3 SYSTEM ARCHITECTURE 16
3.1 HOTSPOT NETWORK ARCHITECTURE 16
3.2 HOTSPOT NETWORK WITH CAPTIVE PORTAL 17
3.3 DYNAMIC DNS ARCHITECTURE 18
3.4 ACCESS GATEWAY ARCHITECTURE 20
3.5 THE OPEN SOURCE PROJECT OPENWRT 21
CHAPTER 4 IMPLEMENTATION OF NETWORK ACCESS CONTROL GATEWAY 23
4.1 LINKSYS WRT54GL 23
4.2 HOW TO DEVELOPMENT OPENWRT FIRMWARE 25
4.2.1 Download OpenWrt 25
4.2.2 The directory structure 26
4.2.3 Building OpenWrt 28
4.2.4 Using the SDK 31
4.3 INTEGRATION OF CAPTIVE PORTAL INTO OPENWRT 33
4.3.1 ChilliSpot 33
4.3.2 Installing ChilliSpot on OpenWrt 36
4.3.3 Setup RADIUS server and HTTPD server 39
4.3.4 Modify ChilliSpot Config File 42
4.4 INTEGRATION OF DYNAMIC DNS CLIENT INTO OPENWRT 43
CHAPTER 5 IMPLEMENTATION OF IP PLUG AND PLAY 45
5.1 DESIGN CONCEPT OF IP PLUG AND PLAY 45
5.1.1 Proxy ARP for Client’s Gateway Address 45
5.1.2 IP Route and Host Link 46
5.1.3 DNS Server 47
5.2 IMPLEMENTATION OF IP PLUG AND PLAY 48
5.2.1 Iptables in OpenWrt 48
5.2.2 IP PnP configuration 52
5.2.3 Operations when IP PnP user connects to the gateway 53
5.2.4 Some Problems 54
CHAPTER 6 CONCLUSION AND FUTURE WORK 56
6.1 CONCLUSION 56
6.2 FUTURE WORK 56
REFERENCE 58

[1] C. Rigney, et al. “Remote Authentication Dial In User Service (RADIUS),” RFC 2865, June 2000.
[2] C. Rigney, et al. “RADUIS Accounting,” RFC 2866, June 2000.
[3] C. Rigney, et al. “RADUIS Extensions,” RFC 2869, June 2000.
[4] FreeRADIUS Website
http://www.freeradius.org/
[5] P. Vixie, et al. “Dynamic Updates in the Domain Name System (DNS UPDATE)” RFC 2136, April 1997.
[6] YesTurnkey WNOC Management System Website
http://www.yesturnkey.com/
[7] No-IP.com (Dynamic DNS) Website
http://www.No-IP.com/
[8] OpenWrt Website
http://openwrt.org/
[9] ChilliSpot Website
http://www.chillispot.info/
[10] Yen-Cheng Chou, “Implementation of Network Access Control Gateway”, Dept. of Electrical Engineering of National Taiwan University, June 2007
[11] Chiung-Lin Chen, “Implementation of Wireless Hotspot Access Control Gateway”, Graduate Institute of Networking and Multimedia of National Taiwan University, June 2007
[12] Florian Fainelli ,“The OpenWrt embedded development framework”, Jan. 2008
[13] Netfilter, “NAT HOWTO”
http://www.netfilter.org/unreliable-guides/NAT-HOWTO/.
[14] Netfilter, “Packet Filtering HOWTO”
http://www.netfilter.org/unreliable-guides/packet-filtering-HOWTO/.
[15] Win-Bin See, “Design and Implementation of an Embedded Software Development Platform”, Dept. of Electrical Engineering of National Taiwan University, July 2003
[16] Juan Caballero and Daniel Malmkvist, “Experimental Study of a Network Access Server for a Public WLAN Access Network,” Master’s Thesis, Dept. of Microelectronics and Information Technology, Royal Institute of Technology, KTH, January 2002
[17] David Alvén and Reza Farhang, “Analysis of the WLAN from a WISP perspective,” Master’s Thesis, Dept. of Microelectronics and Information Technology, Royal Institute of Technology, KTH, February 2002