Practical Wireless IP: Concepts, Administration, and Security Brad C. Johnson & Philip Cox SystemExperts Corporation Just checking... n This is a top level bullet n This is the next level in n this would be level 3 n this would be level 4 n Can you hear? Check 1…2…3…Check n Is it too hot? Too cold? V 2.
Course Contents n What is is n Wireless, focused on n n n n IP services for laptops n and a little on handheld and cellphone Internet access n n Wireless, for understanding n What it isn’t A Radio Frequency Primer An in-depth analysis of Cellular Wireless protocols An exhaustive list of wireless providers and devices Security, configuration, and usage V 2.
Where are We? n From 50,000’ to 5’ in about 24 slides n n *NIX and Wireless Threats n Handheld Practicals n Currents n LAN Practicals n Antennas V 2.2 Copyright SystemExperts 2001,2002,2003 5 What is Wireless 10 mbps Spread Spectrum WLAN 2 mbps 1 mbps Infrared WLAN D a t a 4 mbps 128 kbps Broadband PCS 56 kbps Circuit & 19.6 kbps 9.6 kbps Packet Data Narrowband WLAN Narrowband PCS Local Coverage Area V 2.
Wireless Component Overview This Course 802.11 PDA Wired Network PSTN This Course Gateway Gateway V 2.
Single Function Device Migration n Handheld n Cellular Phone n n n n PDA n n voice and data increasing speeds more complex displays viable as stand-alone wireless device (without requiring desktop download first) Pager n interactive V 2.2 Copyright SystemExperts 2001,2002,2003 9 General Purpose Devices n HomeRF n n n n 2.4 GHz band 1.6 Mbps from a distance of about 150 feet Residential market Bluetooth n n n n 2.
802.11b n Unlicensed 2.4 GHz band n Uses direct-sequence spread-spectrum (DSSS) n n 1 - 11 Mbps from a distance of about 150 to 2000 feet (without special antenna) n n Frequency-Hopping FHSS can only be used for 1 & 2 Mbps in US because of FCC regulations …more on this later Home business and business markets V 2.2 Copyright SystemExperts 2001,2002,2003 11 802.11 Plain and Simple Application Presentation Network Operating System (NOS) 802.
802.11b n Physical Layer n n n Physical Medium Dependent (PMD) – wireless encoding Physical Layer Convergence Protocol (PLCP) – common interface n n MAC Layer n n n Inter Frame Space (IFS) Physical Carrier Sense Virtual Carrier Sense n n n n long preamble for all 802.11b systems short preamble for special case: e.g., streaming video, Voiceover IP e.g., hidden-node Frame Control Power Management Fragmentation 13 V 2.2 Copyright SystemExperts 2001,2002,2003 802.
02.11b Frame Control n 3 types of 802.11b packets n Management (type 00) n n n n n Control (01) n n {association, re-association, probe} {request, response} authentication, de-authentication, & disassociation beacon n e.g., time-stamp, traffic indication map, supported rates ATIM – Announcement Traffic Information Message n sent after each frame RTS, CTS, ACK, CF*, PS-Poll Data (10) n n ok, data! plus CF-ACK/Poll, etc. V 2.2 Copyright SystemExperts 2001,2002,2003 15 802.
802.11b BSS n Wired LAN Basic Service Set (BSS) n n Infrastructure mode Uses an AP to connect clients to a wired network V 2.2 Copyright SystemExperts 2001,2002,2003 Access Point 17 802.11b ESS n Wired LAN Extended Service Set (ESS) n n n Infrastructure mode Uses multiple APs Clients may roam between APs n Access Points …more on roaming later V 2.
Exposures n Technology problems n Theft of hardware n Insecure configuration information n Masquerading n Virus n Eavesdropping n Authorization V 2.
Theft of hardware n Wireless stuff is small n n Wireless cards fit in a shirt-pocket Most of the APs fit in a jacket pocket or are easily hidden in any kind of bag n should they be tagged like clothes in a store? n Cisco 340 cards write WEP keys to the card n If a laptop were stolen, how long would it take to re-key your Wireless network? n APs have WEP Keys in them n Data is stored locally V 2.
Lucent Client Registry Entries SSID Obfuscated or encrypted WEP Key V 2.2 Copyright SystemExperts 2001,2002,2003 23 Registry Permissions Any authenticated user Can read and copy this data L V 2.
Masquerading n Client side n n n n Access Point n n AP identifies system, not user System may be used by more than one user No authorization schemes for different user groups Clients don’t authenticate AP’s Solution n Per user authentication: EAP V 2.
Eavesdropping n Indirect: listening to the network that the wireless access point is connected to (PROMISC) n n n Remember: WEP only encrypts data between the client and the access point! Quite frankly, this is what most people are doing when they talk about “sniffing wireless” Direct: listening to the airwaves (RFMON) n n Sender can not detect eavesdropping Frequency band largely determines range n n it is quite possible that it goes outside the building special electromagnetic shielding is needed t
MAC address configuration L V 2.2 Copyright SystemExperts 2001,2002,2003 29 Notes: V 2.
Notes: V 2.2 Copyright SystemExperts 2001,2002,2003 31 Notes: V 2.
Where are We? n From 50,000’ to 5’ n *NIX and Wireless n Handheld Practicals n Currents n LAN Practicals n Antennas V 2.2 Copyright SystemExperts 2001,2002,2003 33 Section Contents n Transports n Mobile Data Services V 2.
Key Factors in Technology n Regulation n n In US “competition” was king n n Regional Bell’s and one other (1/2 each) In Europe “interoperability” was king n n n Determines who gets what and how Government owned “Bells”, so no competition, so let’s interoperate Need to exchange billing and accounting information Security was designed to protect against fraud n As opposed to protecting your data V 2.
Major Cellular Systems n n n n n n Advanced Mobile Phone System (AMPS) IS-54/IS-136 IS-95 Global System for Mobile Communications (GSM) Integrated Digital Enhanced Network (iDEN) PCS Note Telecommunications Industry Association (TIA) is the main standards carrier for the Interim Standards (IS) V 2.2 Copyright SystemExperts 2001,2002,2003 37 GSM “THE” system outside of the US n A digital system using a modified version of TDMA n Data at 9.
GSM Security n International Mobile Equipment Identity (IMEI) for each device to determine if device is allowed on the network n Shared secret: Stored in the Authentication Center (AuC) and subscriber's SIM card n n Authentication: The AuC generates a random number sends it to the mobile. Mobile uses A3 cipher and shared key to generate a signed response sent back to the AuC Encryption: Use a key derived from A8 cipher using the same pseudo random number+subscriber-key as above.
CDPD n IS-732 n n It enables analog AMPS networks to carry packetized data alongside voice n n n n Uses idle voice channel or dedicated data channel depending on network configuration CDPD is to AMPS what D-AMPS+ is to TDMA (IS-136/D-AMPS) a way to do Packet Data vice Circuit Data Operates on the 800 MHz frequency Data only, up to 19.2k Requires a modem to convert analog V 2.
Other Popular Systems n Cingular (a.k.a. Mobitex) n n n Operated by Bell South and RAM Mobile Data Data up to 8k Wide coverage n n n Australia, Belgium, Canada, Korea, Netherlands, Sweden, United Kingdom, United States Used by PALM VII and Blackberry ARDIS (DataTAC) n n n Connection oriented Two versions: MDC4800 and RD-LAP Most widely used version is Radio Data Link Access Protocol (RD-LAP) n used by Motient for Blackberry V 2.
In a box … Network Type Technology Provider Speed Packet (data) Mobitex Cingular 8k CDPD AT&T , Verizon, BC TEL Mobility, TELUS Mobility 19.2k RD-LAP Motient 19.2k iDEN Nextel Online 9.6k CDMA Verizon, Sprint PCS, Bell Mobility & Clearnet PCS, Airtouch, GTE, Bell Atlantic, Primeco, others 14.4k GSM Cingular (old PacBell), Voicestream, Omnipoint, BellSouth Mobility, Sprint, others 9.6k TDMA AT&T , BellSouth, Southwestern Bell 9.6k AMPS AT&T 19.2k iDEN Nextel (voice) 9.
Section Contents n Transports n Mobile Data Services V 2.2 Copyright SystemExperts 2001,2002,2003 47 Mobile Data Services n Currently there are three main services provided: n n n n Messaging Wireless Web Proprietary applications As time goes on, specific applications will be written or ported to provide mobile services V 2.
Mobile Data Services: Messaging n Short Messaging Service (SMS) n n n Cell Broadcast Service (CBS) n n n n Available on all digital technologies 140-260 byte messages, store and forward Available on GSM only 1,395 byte messages Limited deployment: No way to bill, it’s broadcast J Unstructured Supplementary Services Data (USSD) n n Connection oriented, GSM based (also UMTS, GSM successor) 182 bytes, uses control channel V 2.
C-HTML n Created by W3C n Simplified version of HTML n Heavily used in Japan via i-mode service n Virtually unknown elsewhere n Advantage: Displays equally well on regular browsers n Disadvantage: Not optimized for handheld limitations V 2.
Wireless Application Protocol (WAP) n An application environment n A set of communication protocols for wireless devices n Derived from Handheld Device Markup Language (HDML) by Phone.com (a.k.a. Unwired Planet) n Client/server philosophy n Uses a micro-browser and a WAP Gateway connected to the mobile network V 2.2 Copyright SystemExperts 2001,2002,2003 53 WAP Architecture HTTP WSP/WTP WAP Gateway Web Server Note: WAP Server = WAP Gateway + Web Server V 2.
WAP Protocol Layers Applicaiton Wireless Application Environment (WAE) Session Wireless Session Protocol (WSP) Transaction Wireless Transaction Protocol (WTP) Security Wireless Transport Layer Security (WTLS) Transport Network V 2.2 Copyright SystemExperts 2001,2002,2003 Wireless Datagram Protocol (WDP) UDP Bearers (GSM, SMS, CDMA, CDPD, GPRS, etc.
Gap in WAP WTLS SSL HTTP SERVER WAP Gateway SSL Encrypt V 2.2 Copyright SystemExperts 2001,2002,2003 Plain Text Client Decrypt WTLS 57 VPNs n Certicom’s movianVPN n Basis for iPassConnect PDA service n n n n requires a modem and two pieces of software on the PDA lightweight version of iPass’ dialer, called iPass Synch and movianVPN n users dial up an iPass-affiliated ISP, then establish a VPN Cisco VPN concentrators will support the client Texas Instruments/SafeNet VPN V 2.
What Really Matters? n Security n Encryption options by… n n n n n n the Bearer the Application WTLS n n Device cost n n Ease of configuration, upgrades constantly changing options and services Handheld n n Where can you use it? What can you get to? Device management n Phones n Interoperability PocketPC vs. CE vs. PALM Expandability V 2.2 Copyright SystemExperts 2001,2002,2003 59 Notes: V 2.
Where are We? n From 50,000’ to 5’ n *NIX and Wireless n Handheld Practicals n Currents n LAN Practicals n Antennas V 2.2 Copyright SystemExperts 2001,2002,2003 61 Section Contents n 802.11 n Access Points 101 n Deployment Examples V 2.
Wireless LAN Technologies n Made up of three primary semi-competing technologies n n n IEEE 802.11 {802.11b is our focus} Bluetooth HomeRF V 2.2 Copyright SystemExperts 2001,2002,2003 63 Upcoming WLAN n IEEE 802.11g (Next generation WLAN) n n n n Data rates of 20+ Mbps Selected Intersil's Orthogonal Frequency Division Multiplexing (OFDM) TI's Packet Binary Convolution Coding (PBCC) technology was not selected 802.11a n …more later V 2.
802.11 Local Area Wireless n IEEE 802.11 makes up the majority of Wireless LANs n 802.11b (a.k.a. Wi-Fi™) is the current favorite n n Encodes data using DSSS (direct-sequence spread-spectrum) technology Runs in the 2.4-GHz range n n different ranges in different regions US, Europe, Japan, France, Spain Four “speed” ranges: 1-Mbps, 2-Mbps, 5.5-Mbps, and 11Mbps V 2.2 Copyright SystemExperts 2001,2002,2003 65 802.
Current 802.11 Security n Privacy n n Authentication n n n Wired Equivalent Privacy (WEP) Shared key Open system Authorization n MAC V 2.2 Copyright SystemExperts 2001,2002,2003 67 Wired Equivalent Privacy (WEP) n Purpose it to provide “privacy of a wire” n Uses RC4 for encryption n n The IV, Encrypted Message, and checksum are sent in the 802.
More on WEP Keys n Standard says 40bit, but many vendors support or 128 bit n n 40bit is actually 64bit: a 40bit key and 24-bit IV 128bit is a 104-bit key with a 24-bit IV n No key-management protocol n Also no inter AP protocol (IAPP) to pass keys V 2.2 Copyright SystemExperts 2001,2002,2003 69 Access Points and WEP Q: What does WEP do for you? A: Think of SSL and WTLS WEP Client Not WEP Wired Network Access Point SSL Client Not SSL Backend Server HTTP Server WTLS Client V 2.
WEP Encryption Steps n Integrity Check Value computed n n Checksum of payload (i.e., plaintext) using CRC32 Select encryption key n One of four keys selected Generate IV n Use RC4 to generate a keystream RC4(IV,Key) n n Note IV is prepended to key Concatenate ICV to payload, then XOR with the generated keystream to get ciphertext n Send IV+keynumber+ciphertext over the air n n Key number is the key selected in the second step 71 V 2.
WEP Decryption Steps n Use key number to get private key n Use sent IV to generate keystream n n RC4(IV,Key) XOR received ciphertext with keystream n Get ICV+Payload n Compute ICV on Payload n If new ICV == sent ICV, then packet good 73 V 2.2 Copyright SystemExperts 2001,2002,2003 WEP Decryption IV Secret Key Payload ICV RC4 XOR ICV IV Ciphertext Message V 2.
128-bit Version (WEP2) n Stronger Key n Non-standard, but in wide use n 104-bit key instead of 40-bit in standard WEP V 2.
The Major WEP Problems n Key Generators n Keystream Reuse n RC4 Key Scheduling Algorithm n Message Authentication V 2.
Problem: Keystream Reuse n The shared key is static and rarely changed n Randomness of key stream depends on IV n n n When IV is reused, then you have two messages encrypted with same keystream (a collision) 2^24 possible IV, so repeated after ~16 million packets Most clients reset IV to 0 and increment by 1 for each packet n lots of collisions V 2.2 Copyright SystemExperts 2001,2002,2003 79 Problem: Keystream Reuse Attack n Attacker sends you a known packet (i.e.
Problem: Key Scheduling Algorithm of RC4 n Documented by Scott Fluhrer, Itsik Mantin and Adi Shamir n n n Paper indicated that an attacker could gain access to an entire WLAN in less than 15 minutes Requires between 1 million and 8 million packets, and does not require significant CPU power Main problem is a weakness in the way the RC4 encryption algorithm is implemented in WEP n n By having a “known” plaintext prepended on the key (I.e.
Problem: Message Authentication n The Cyclical Redundancy Check (CRC) chosen for the authentication is weak n It is designed for errors, not authentication n It is possible to modify a message such that the CRC will be valid for the messages, but is not the messages that was sent n Can also inject messages in much the same manner V 2.2 Copyright SystemExperts 2001,2002,2003 83 Current Status of WEP IEEE 802.
Current Status of WEP (cont) Use AES vice RC4 n 802.1X rekey be accepted as normative text n “WEP2” to be known as “Temporal Key Integrity Protocol (TKIP)” n V 2.2 Copyright SystemExperts 2001,2002,2003 85 Current 802.11b Authentication n Two specified in the standard: Open and Shared n Open system authentication: This is the default n n any client can associate with the access point n doesn’t mean the get an IP though Shared key authentication: Uses a shared secret key (i.e.
Other 802.11b Authentication Mechanisms n Closed network (no broadcast SSID) n Enhanced Security Network (ESN) n n Many call it 802.1x inappropriately Captive Portals n NoCat V 2.2 Copyright SystemExperts 2001,2002,2003 87 Current 802.11 Authorization n MAC Layer n n Can configure the AP to talk to specific MAC addresses Controls access to wired network not wireless V 2.
ESN: The Wireless Security Future? Defined in the 802.11 Security Baseline n Depends on 802.1X n n n Provides n n n n Enhanced authentication Key management algorithms Dynamic, association-specific WEP keys Open authentication method n n Protocol definitions between client and bridge and bridge and authentication server Looks like many vendors are using RADIUS Uses EAP encapsulated in 802.11b Frames n EAP is defined in RFC 2284 V 2.
Future 802.11 Security Enhancements n Standard 128-bit WEP encryption (WEP2) n n n Advanced Encryption Standard (AES) for WEP Standard key exchange and distribution n n Already implemented by all of the major vendors but has not been standardized yet EAP & LEAP seem to be the wave of the future Improved data integrity via keyed message authentication n Better message integrity checking V 2.
Let’s take a look…J n 802.11b packets n n n n Beacon Probe Request Open Authentication n n Shared Authentication No WEP WEP MAC Header FC 2 bytes ID 2 bytes Add 1 6 bytes Protocol 2 bits Type 2 bits SubType 4 bits b0 b1 b2 b3 Add 2 6 bytes Add 3 6 bytes To DS From DS 1 bit 1 bit b4 b5 b6 b7 V 2.
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Section Contents n 802.11 n Access Points 101 n Deployment Examples V 2.2 Copyright SystemExperts 2001,2002,2003 97 Access Points 101 n Access Points (AP) broadcast their service (beacon) n FCC (US) allows 11 channels for Direct Sequence Spread Spectrum (DSSS) n n in North America and Europe, they start at 2412 MHz (2.412 GHz) The spread spectrum for DSSS crosses over several channels n i.e.
Frequency Overlap 5 10 4 9 3 8 7 2 1 2400 6 11 Frequency (US) 2500 Channels start at 2414MHz, increase by 5MHz, and have about a 20MHz range up to 2483.5MHz V 2.2 Copyright SystemExperts 2001,2002,2003 99 Access Point Usage n Number of clients supported depends on device “memory” size, aggregation, congestion, noise, quality, etc., etc., etc. n n As we’ll see later, the Apple Airport AP (e.g.
Extension Point Range Wireless Extension Point V 2.2 Copyright SystemExperts 2001,2002,2003 101 Access Point Placement n Roaming can be achieved by having slightly overlapping APs on different channels n n 2.4Ghz contains 80MHz of spectrum n n …more on roaming in just a bit 25MHz to minimize interference Only 3 equivalent-width non-overlapping DSSS channels V 2.
Placement (cont.) V 2.2 Copyright SystemExperts 2001,2002,2003 103 Placement (cont.) n Developing configurations to maximize roaming and minimize interference is hard n n Remember it’s 3 dimensional broadcasts Remember it goes through walls! n out to the street, to your neighbor, to your competitor! V 2.
Placement, 3 Dimensional V 2.2 Copyright SystemExperts 2001,2002,2003 105 Capacity and Bandwidth n Maximum of 11Mbps n n Not really: since the Physical Layer Convergence Protocol (PLCP) layer is always transmitted at 1Mpbs, 802.11b is only 85% efficient as the physical layer Goes down because of n Distance, barriers, collisions, interference, congestion, capacity usage V 2.
Capacity and Bandwidth n (cont.) Stays “higher” because of n n n Reducing size of coverage areas Reducing client-to-AP ratio Using aggregation n increasing AP-to-client ratio and using load balancing V 2.2 Copyright SystemExperts 2001,2002,2003 107 Bandwidth Aggregation V 2.
Anatomy of 802.11b n Looking at some of the guts of the protocol to help us understand: n n Modulation determines speed/distance What effects the transmission rate n n n n other than distance or barriers Congestion resolution Hidden nodes The MAC layer is our friend! V 2.2 Copyright SystemExperts 2001,2002,2003 109 Anatomy of 802.11b: the bits n As we said before, data is encoded using DSSS n n i.e.
Anatomy of 802.11b: the wave n …then the wireless radio generates a 2.4 GHz wave and modulates it… n n n n 1Mbps is done using Binary Phase Shift Keying 2Mbps uses Quadrature Phase Shift Keying (QPSK) 5.5 & 11Mbps use Complementary Sequences (vs.
Congestion (cont.) n Each station listens to the network n 1 st station to finish it’s allocated slot times sends data n If another station “hears” another station talk, it stops counting down its back-off timer n In addition to the MAC back-off, 802.11 adds another back-off to ensure fairness n When in this “contention window” it uses these back-off timers 113 V 2.2 Copyright SystemExperts 2001,2002,2003 Congestion (cont.
Anatomy of 802.11b: Hidden Node Problem n AP P sees A, B, and C, but A and C can’t see each other (see means, the packets don’t reach) n n Optional feature of RTS/CTS added to 802.11b RTS packet includes target address n n CTS includes sender address n n A sends: “This is for B” (C doesn’t see this) B sends: “Please send A” (C DOES see this) This feature is significant overhead but a very common condition that needs to be accounted for 115 V 2.
Hidden Node Problem: Let’s try it again n 802.11 n n n basically designed for indoor, relatively short distances, active and long-lived connected clients, and low noise level but 802.11 (“wi-fi”) is “winning” in the wireless arena and being increasingly used as well in outdoor, long distant, occasionally connected, potentially high noise level environments So what does that mean to hidden nodes? n The key is the need to minimize the amount of overhead you introduce to manage them V 2.
Surprising Results What does this mean? In certain circumstances, the method used makes a HUGE difference! Polling with RTS/CTS V 2.2 Copyright SystemExperts 2001,2002,2003 119 What Does This Mean? n Media reservation systems (e.g., RTS/CTS) work “better” in stable environments with expectations of full/long-lived connectivity n n e.g., in your office building, point-to-point connections, small number of nodes Adaptive systems (e.g., polling) work “better” in other environments n n e.g.
Anatomy of 802.11b: Roaming n More than 1 AP providing signals to a single client n The client is responsible for choosing the best AP n n signal strength (#1) and network utilization (#2) When existing signal degrades (to poor), it tries to find another AP n n either passively listening or actively probing the other channels and getting a response once it finds one, it tries to authenticate and associate V 2.2 Copyright SystemExperts 2001,2002,2003 121 Roaming (cont.
Important Concepts: Strength vs. Quality n Received Signal Strength n Signal energy at the location of the station n n (i.e., the power level) Received Signal Quality n Ability to coherently interpret the signal n (i.e., the usability level) V 2.2 Copyright SystemExperts 2001,2002,2003 123 Roaming Activities n IAPP or Inter Access Point Protocol is intended to standardize roaming features and protocol n n n Started by Aironet (Cisco), Digital Ocean, and Lucent 802.
IEEE IAPP n Accomplishes roaming within a subnet n n 2 transfer protocols n n n Basically, within a corporate wireless LAN 1 for single logical LANs 1 for crossing router boundaries Crossing subnets is a vendor specific solution n n It requires mobile IP software on every client Cisco, e.g., is expected to release Mobile IP V 2.
Wi-FI Roaming n (cont.) 802.11b n n n Boot up with correct SSID for Wi-Fi network Local WISP login screen n n n n which details charges separate window tracks session information V 2.2 Copyright SystemExperts 2001,2002,2003 802.1x n Boot up Prompted with username/password for local WISP Windows XP is only 1x implementation available today 127 WISPr WECA is looking to form a set of relationships and network standards between wireless ISP’s that will eventually enable Wireless 802.
Configuring an Access Point n How to manage it n n Security Settings n n n n HTTP, Telnet, SNMP or Serial Interface SSID, WEP, & EAP RADIUS servers and shared key MAC layer Filters Making it work easily with clients n DHCP V 2.
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Section Contents n 802.11 n Access Points 101 n Deployment Examples V 2.2 Copyright SystemExperts 2001,2002,2003 133 Wireless at Home n Goals n n n n Extend network capabilities without physical alterations and costs – other than wireless Share existing resources without specialized or unique (weird) configuration setup Allow visitors easy access to the home network resources (e.g., ISDN, printers) Feel comfortable about the security of the additional wireless services V 2.
Wireless at a Conference n Goals n n n n Reduce time to setup fully functional temporary network resources Scale down terminal room requirements Reduce effort and cost to provide Internet access to tutorial instructors and their students Allow attendees ubiquitous access to the Internet within a reasonable distance to the conference center V 2.
CyberCafe n Typically an Open AP n Use a captive portal to allow access n Costly n Starbucks is one of the first n n n Use MobileStar as their ISP Seem to use a combo of special SSID and captive portal Watch for Neighborhood Area Networks V 2.2 Copyright SystemExperts 2001,2002,2003 137 Architectural Considerations n n Need to have a defined goal Segregate the wireless infrastructure n n Use appropriate data protection mechanisms n n n n n Isolated sub-network/DMZ VPNs SSL SSH etc.
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Where are We? n From 50,000’ to 5’ n *NIX and Wireless n Handheld Practicals n Currents n LAN Practicals n Antennas V 2.
Linux Sniffer: How-To Directions at Tim Newsham’s site http://www.lava.net/~newsham/wlan n Get an SMC2632W wireless card n Get a wlan-ng driver with RF monitoring code n n n Get ethereal-0.8.17 n n Get linux-wlan-ng-0.1.8-pre13 and apply wlan-monitor.patch Or linux-wlan-ng-0.1.6.tar.gz Apply patches from wlan-mods.tgz Get Libpcap-0.6.2 or Prismdump n Apply LibPcap patches from wlan-mods.tgz V 2.2 Copyright SystemExperts 2001,2002,2003 143 How-To (cont.
Sniffer Observations n It works! Its Linux! Its free! n Only one channel at a time L n n You can write a script to change that J You have to type “prism” as the interface for ethereal if you use LibPcap V 2.
Home Spun Access Point n What is it n A system that gateways between the wireless and wired networks n n n n n n a.k.a. Wireless Gateway Implements IBSS (Ad-hoc) or BSS modes Typically provides DHCP and firewall/NAT services May provide authentication and authorization Usually some flavor of Unix (Linux or FreeBSD) What does it entail n n n Get the equipment Install the software Tweak a bit V 2.2 Copyright SystemExperts 2001,2002,2003 147 Building your own AP C o n d e n s e d f r o m http://www.
Directions (cont.) n Harden the rest of the system (read: TURN OFF ALL UNUSED SERVICES) n n Reboot and see what you broke J n n Keep the PCMCIA, firewall, and DHCP services running Probably should reboot before the firewall and DHCP install/configure Setup clients V 2.
My Observations n Functionality is limited in some instances n IBSS only n n WLAN-NG supposedly supports BSS, I never got it to work Functionality is enhanced in others n Firewall and potential authentication/authorization hub n If education and experience is what you want, then this is the way to go n If a up and running or many-client is what you want, then buy an AP n Especially for people with limited time and/or experience V 2.
OpenAP n OpenAP http://opensource.instant802.com/ n n n Has the ability to: n n Do multipoint to multipoint wireless bridging, while simultaneously serving 802.11b stations (i.e. and AP) Runs on Eumitcom WL11000SA- N board based AP’s n n n Open-source software Fully 802.11b compliant wireless access point US Robotics (USR 2450) (tested) SMC 2652W EZconnect Wireless AP (tested) Why use it? n n n You have the source It is customizable It can do anything that Linux can do V 2.
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Where are We? n From 50,000’ to 5’ n *NIX and Wireless n Handheld Practicals n Currents n LAN Practicals n Antennas V 2.2 Copyright SystemExperts 2001,2002,2003 157 IEEE 802.
2.11a Spectrum Band USA/ Europe France Spain Japan 200mW Canada n 5 . 1 5 0 -5.250 50mW 200mW 200mW 200mW 5 . 2 5 0 -5.350 250mW 200mW 200mW 200mW 5 . 7 2 5 -5.825 1W 3 primary non-contiguous bands n 100MHz each band with power restrictions n n n n split into 20MHz channels 5.15-5.25 GHz: Indoor, short-range 5.25-5.35 GHz: Indoor or outdoor, medium range(campus-type networks) 5.725-5.825 GHz: Outdoor, long-range (several km) V 2.2 Copyright SystemExperts 2001,2002,2003 802.
802.11a Coverage Tech Data Rate Throughput Range and Data Shared 802.11b 11Mbps 5- 7 M b p s 100m @ 11Mbps Yes 802.11g 24Mbps 1 0- 1 1 M b p s 100m @ 12Mbps Yes 802.11a 54Mbps 31Mbps 50m @ 9Mbps Yes 3 0- 4 0 m @ 9 - 1 2 M b p s Yes 1 0- 1 5 m @ 3 6 -5 4 M b p s Yes n 802.
802.11a Problems n Use of 5 GHz band will cause contention in different parts of the world n n Remember the problems with spectrums in handhelds Coverage will cost n n Number of APs Power (i.e., battery life) V 2.2 Copyright SystemExperts 2001,2002,2003 163 802.11 Thoughts n Usage n n n Coexistence n n Use 802.11a for dense populations and high speeds Use 802.11b/g for greater coverage Likely to be working together for many years to come Price n 802.
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Where are We? n From 50,000’ to 5’ n *NIX and Wireless n Handheld Practicals n Currents n LAN Practicals n Antennas V 2.2 Copyright SystemExperts 2001,2002,2003 167 Antennas: The Skinny n 2.
Antennas: Basics n A radiation pattern is a diagram that allows us to visualize in what directions the energy will radiate from an antenna n n n If an antenna radiates in all directions equally we say it is an “isotropic radiator” The radiation pattern is split into two perpendicular planes called Azimuth and Elevation When RF energy is concentrated, it means the antenna has “gain” over a portion of the radiator n gain is measured in decibels and written dBi V 2.
Antennas: Dipole n Most common antenna and the default type on most APs n n n Usually a 1-inch radiating element Note: the higher the frequency, the smaller the antenna and the wavelength become Radiation pattern n n “Donut” like Radiates in equally in all directions around its axis but NOT along the length of the wire n also called omnidirectional V 2.2 Copyright SystemExperts 2001,2002,2003 171 Dipole Radiation V 2.
Antennas: Directional n Directional antenna concentrate their energy into a cone n n Known as a beam Radiation pattern n It depends on what kind of directional antenna you have V 2.2 Copyright SystemExperts 2001,2002,2003 173 Directional Radiation: Biquad V 2.
Antennas: PCMCIA Cards n Their terrible, awful, did I mention yuck? n n n n It’s hard to form antennas onto the card The effective gain is low They tend to be VERY directional These are some of the reasons that your signal strength can change dramatically with small changes V 2.2 Copyright SystemExperts 2001,2002,2003 175 Typical PCMCIA Radiation V 2.
Antennas: More Facts n Constant trade-off of range and throughput n n n Remember that the “low” speed of 1 Mbps is slightly slower than a T1 connection (1.544 Mbps) Remember that the top speed of 11 Mbps is only over the air: the Ethernet it’s connected to is 10 Mbps and then you have contention, etc. Current client cards have only 1 radio in them n that means half-duplex (they can’t listen and talk at the same time) V 2.
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Review n Why is it basically impossible to get full 2, 5.5, or 11 Mbps? n What’s the common management interface to ALL APs? n What’s the difference between AP aggregation and AP DoS? n What are the security implications of broadcast SSID? n What is the problem with MAC based ACL security? V 2.
The End n Thank you for attending! n Please fill out the Instructor Evaluation Form!! n Thank you for your comments! n www.SystemExperts.com/ tutors/wirelessip.pdf V 2.2 Copyright SystemExperts 2001,2002,2003 183 Thanks to … n David Lounsbury n n Lynda McGinley n n n Vice President of Research for The Open Group University of Colorado Coordinator or USENIX wireless services Richard Rothschild n Director Ariba Network Operations for Ariba V 2.
References n Access Points n n n n n www.cisco.com/warp/public/cc/pd/witc/ao340ap/ www.apple.com/airport/specs.html www.wavelan.com/template.html?section=m58&pag e=103&envelope=94 www.3com.com/products/proddatasheet/datasheet/ 3CRWE74796B.pdf Cell Phone Internet Services n n n n www.sprintpcs.com/wireless www.verizonwireless.com www.attws.com/personal/explore/pocketnet www.nextel.com/phone_services/wirelessweb V 2.2 Copyright SystemExperts 2001,2002,2003 185 References (cont.
References (cont.) n Reference material n n n n n n n n n n www.cmu.edu/computing/wireless/index.html www.teleport.com/~samc/psuwireless/ www.hpl.hp.com/personal/Jean_Tourrilhes/Linux/ Linux.Wireless.drivers.html www.proxim.com/wireless/glossary/index.shtml www.motorola.com/SPS/WIRELESS/information/glossary.html www.wireless-online.com/glossary.htm www.zdnet.com/pcmag/stories/reviews/0,6755,2603595,00.ht ml http://allnetdevices.com/faq/ www.wapforum.org/ www.ntia.doc.gov/osmhome/allochrt.
Wireless Stuff n Wireless performance article n n IEEE 802.11 page n n www.networkcomputing.com/1113/1113f2full.html www.ieee802.org/11/ 802.11b Primer n www.personaltelco.net/download/802.11bprimer.pdf V 2.2 Copyright SystemExperts 2001,2002,2003 189 Mailing Lists n Bay Area Wireless Users Group n http://lists.bawug.org/mailman/listinfo/wireless/ NOTE: This is THE list to watch! n Aironet n n http://csl.cse.ucsc.edu/mailman/listinfo/aironet O’Reilly n http://oreilly.wirelessdevnet.
Glossary 3G (third generation) An industry term used to describe the next, still-to-come generation of wireless applications. It represents a move from circuit-switched communications (where a device user has to dial in to a network) to broadband, high-speed, packet-based wireless networks (which are always "on"). The first generation of wireless communications relied on analog technology, followed by digital wireless communications.
Glossary (cont.) GPRS (general packet radio service) A technology that sends packets of data across a wireless network at speeds of up to 114Kbps. It is a step up from the circuit-switched method; wireless users do not have to dial in to networks to download information. With GPRS, wireless devices are always on—they can receive and send information without dial-ins. GPRS is designed to work with GSM.
Glossary (cont.) WCDMA (wideband CDMA) A third-generation wireless technology under development that allows for high-speed, high-quality data transmission. Derived from CDMA, WCDMA digitizes and transmits wireless data over a broad range of frequencies. It requires more bandwidth than CDMA but offers faster transmission because it optimizes the use of multiple wireless signals—not just one, as with CDMA.
Apple Airport Gold 128 bit card Silver 64 bit card V 2.2 Copyright SystemExperts 2001,2002,2003 197 Building your own AP Condensed from http://www.oreillynet.com/pub/a/wireless/2001/03/06/recipe.html n Equipment n n 1 desktop PC, 386 or better At least one 802.
Building your own AP n Operating System n A Unix-like operating system n n n (cont.) Linux and FreeBSD seem to be the OS of choice Clients can be anything that can do Ad-Hoc Hints n n n Use an ISA-PCMCIA adapter Lucent cards work great and have ability to have external antenna Be prepared to spend time debugging n depending on the OS level V 2.2 Copyright SystemExperts 2001,2002,2003 199 Building your own AP (cont.
Directions (cont.) n Update the kernel n n n n n Enable loadable module support Enable support for your other NIC cards Enable kernel firewall support Enable IP masquerading (i.e., NAT) Enable Wireless Networking (also known as "nonham") n n do not select any modules When compiling a 2.4.x kernel Disable PCMCIA support n we’ll use the external pcmcia-cs package V 2.2 Copyright SystemExperts 2001,2002,2003 201 Directions (cont.
Directions (cont.) n Configure wireless IP options n n n n Configure NIC IP options n n n /etc/pcmcia/network.opts Use private IP range Set IP, netmask, and broadcast /etc/sysconfig/network-scripts/eth0 Set it to DHCP or static IP values Install or configure the firewall/NAT package n n Configure it to masquerade packets from your wireless network to the outside Ensure that you do proper “security” filtering (i.e., drop spoofed IP packets) V 2.
Floppy based Wireless Gateway n Same basic hardware requirements n n System, ISA-PCMCIA, NIC, Wireless card NIC cards are much more sensitive n Trinux experience helps when adding modules n http://nocat.net/ezwrp.html n My Problems n n n n Got it up quickly Problems with DHCP Never got it passing traffic Unclear how to manage firewall rules V 2.
WFG Internals (cont.) n IP Filtering n n n OpenBSD's IPF software IP routing is enabled Packet filtering between the wireless and external network interfaces n n static filters are configured on boot up n limit initial wireless network access n NTP, DNS, DHCP, and ICMP n for all users: selected email servers, VPN, and web When a user authenticates, they are allowed unrestricted access V 2.2 Copyright SystemExperts 2001,2002,2003 207 WFG Internals (cont.
Notes: V 2.2 Copyright SystemExperts 2001,2002,2003 209 Notes: V 2.
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