Wireless Networking

04 September 2004Quintin Krisp

Overview

Wireless LAN Applications

Wireless LAN Technology

IEEE 802.11 Standard

IEEE 802.11 Protocol Architecture

IEEE 802.11 Relatives

Wi-Fi Security

Wireless LAN ApplicationsLAN Extension: Buildings with large open areas (e.g. Manufacturing

plants, Warehouses) Historical buildings: may not damage building Small offices: wired LANs not economical May be mixed with fixed wiring system (hence LAN

extension) Either a single-cell or multiple-cell wireless LAN

Cross-building interconnection: Point-to-point wireless link between buildings (e.g. Rural

Monash Campuses) Typically connecting bridges or routers Used where cable connection not possible (e.g. across a

street)

Single Cell Wireless LAN

Control module (CM) and User Module (UM).

Multi-Cell Wireless LAN

Wireless LAN ApplicationsNomadic access: Between a LAN hub and mobile

data terminal (e.g. laptop) Transfer of data from laptop to

server Campus or cluster of buildings

Ad hoc networks: Peer-to-peer (no centralized

server) Temporary connection (e.g.

conference)

a) Infrastructure Wireless LAN

b) Ad hoc LAN

Wireless LAN TechnologyInfrared (IR) LANs: Individual cell of IR LAN limited to single room IR light does not penetrate opaque walls More immune to electromagnetic interference (radio transmission or

microwave ovens) No licenses required

Spread spectrum LANs: Mostly operate in ISM (industrial, scientific, and medical) bands No Federal Communications Commission (FCC) licensing is required

in USA

Narrowband microwave: Microwave frequencies but not use spread spectrum Some require FCC licensing

Electromagnetic Spectrum for Telecommunications

802.11 StandardIEEE 802 committee began in 1987 within the IEEE 802.4 group

Initial interest developing ISM-based wireless LAN using equivalent of token-passing bus MAC protocol

Token bus not suitable for radio medium, caused inefficient use of the radio frequency spectrum

IEEE 802.11 formed in 1990 as new working group devoted specifically to wireless LANs

802.11 Protocol ArchitectureDistributed Coordination Function DFC Lower MAC sublayer, uses Ethernet contention

algorithm to provide access to all traffic Contention protocol designed to handle two or

more stations accessing network traffic simultaneously

Point Coordination Function (PCF) Centralized MAC algorithm to provide contention-

free service AP polls according to list, no collisions occur

Logical Link Control (LLC) Provide an interface to higher layers Performs basic link-layer functions such as error

control

802.11 Protocol Architecture

802.11 Relatives802.11d: Modification to comply with other countries

802.11e: Add Quality of Service (QOS)

802.11f: Improve communication between APs for authentication

802.11h: Modification to comply with Europe

802.11i: Improve WLAN security

802.11j: Modification to comply with Japan

802.11k: Provide measurement info of APs

802.11m: Minor Mods to previous Pubs

802.11 Relatives802.11n: Increase WLAN raw throughput802.11p: Utilize 5.9 GHz band for Intelligent Transportation System802.11o: Faster handoff, prioritize voice traffic over data802.11q: Frame tagging for VLAN segregation802.11r: Standardize fast-hand-off802.11s: Self-healing/self-configuring Mesh networks802.11t: Performance prediction

802.11 Relatives802.11d: New Countries Where 802.11 family not allowed to operate Specification similar to 802.11b Main difference, configuration fine-tuned at MAC level

to comply with rules of country or district network to operate

Rules subject to variation include allowed: frequencies, power levels, and signal bandwidth

802.11 Relatives802.11e: Quality of Service (QOS) Goal: Develop QOS technology to help Wi-Fi networks

avoid problems when transmitting time-sensitive data like voice and video

One 802.11e innovation starting to be used: frame bursting or packet burning

Improves ratio of data-to-network overhead by sending larger amounts of data in individual frames

Can only speed up mixed 802.11b/802.11g networks Initial improvement better if all equipment from same

manufacturer

802.11 Relatives802.11f: Inter-Access Point Communication Communication between Wi-Fi APs a problem depending

on manufacture APs will be able to offer fast handoff Eliminates break in service when roaming Some features tie with 802.11i security standard

802.11h: Compatibility with European Regs Supplementary to MAC layer, comply w/5Ghz WLANs Require transmission power control (TPC), limits

minimum power required to reach furthest user Require dynamic frequency selection (DFS), selects

radio channel at AP to minimize interference with other systems

802.11 Relatives802.11i: Security Specifications Replaces wired equivalent privacy (WEP)

encryption with temporal key integrity protocol (TKIP)

Supplement TKIP with advanced encryption system (AES)

Adds pre-authentication, enables user logged into a corporate-style network connected roaming capability while maintaining connection

Relies on inter-access point communication provided by 802.11f

802.11 Relatives802.11j: 5 GHz Operations in Japan Main intent, add channels in the RF band of 4.9

GHz to 5 GHz Implement changes to satisfy Japanese legal

requirements concerning: transmitter output power, operational modes, channel arrangements, and spurious emission levels

Like 802.11a networks Provide speeds up to 54 Mbps Employ OFDM Transfer Method

802.11 Relatives802.11k: Radio Resource Management Address lack of standard for managing WLANs Focuses on two key elements: AP and PC cards Goal: make measurements from physical and data

link layers available to upper layers Allow upper layers to make decisions about the

radio environment and what can be accomplished in that environment

One feature allow better traffic distribution, produce higher speed for the original AP and redirected users

802.11 Relatives802.11m: 802.11 Housekeeping Perform editorial maintenance, corrections, improvements,

clarifications, and interpretations, relative to 802.11 family specification documentation

802.11n: Inter-access Point Communications Objective: increase overall and throughput speed of future

802.11 protocols Real speed 100 Mbps 250 Mbps in PHY level 4-5 times faster than 802.11g 50 times faster than 802.11b Better operating distance

802.11 Relatives802.11o: Vo Wi-Fi Faster Handoff A proposed IEEE group to beSpun out of the

802.11i group Focus for standard for a fast handoff that is fully

secure and compatible with 802.11i and Wi-Fi Protected Access (WPA)

Current supported roaming causes brief break in data stream

802.11i implementation will exacerbate the situation

Handover time (70 milliseconds) make voice calls impossible

802.11 Relatives802.11p: Intelligent Transportation System Established for wireless access in vehicular

environments (WAVE) Dedicated short range communications (DRC) is a

general purpose communications link between the vehicle and roadside (or between vehicles) using 802.11p protocol

Protocols just months old Improves on dedicated 5.9 GHz range (1,000 ft.) and

transmission speed (6 Mbps) Protocol aimed at vehicles: toll collection, vehicle

safety, commerce transactions via cars Government pushing forward to cover highways with

APs that support this new type of extra-secure hotspots that ride over 5.9 GHz

Manufactures expect to install chips, initially in high-end vehicles, in 2007 or 2008 time frame

802.11 Relatives802.11q: VLAN Management Defines mechanisms for tagging frames, allow them to be

segregated into separate VLANs VLANs extend into WLAN by adding 802.11q awareness to the AP Frames destined for different VLANs are transmitted by the AP

wirelessly on different SSIDs with different WEP keys Only the client associated with the VLAN receives those packets Conversely, packets coming from a client associated with a

certain VLAN are tagged with 802.11q before they are forwarded into the wired network

802.11 Relatives802.11r: Fast BSS – Transition Recently founded to address fast roaming

among APs Some experts think technology emerging from

802.11i and 802.11k will render 802.11r group unnecessary

Group still defining scope and does not have a draft yet

802.11 Relatives802.11s: ESS Mesh Networking Aims to define a MAC and PHY for mesh networks Improve coverage with no single point of failure APs relay information hop-by-hop, router like fashion Adding nodes, scalable and redunant Can serve as indoor or outdoor networks Example: Municipalities extend fiber networks or all

outdoor enterprises such as construction sites

802.11t: Wireless Performance Prediction Enable testing, comparison, and deployment planning

of 802.11 WLAN devices Based on common accepted set of performance

metrics, measurement methodologies and test conditions

Wi-Fi SecurityRobust Security Network (RSN) Defined by 802.11i specification Replaces wired equivalent privacy (WEP) Backward compatible support of Wi-Fi protected

access (WPA) based on temporal key integrity protocol (TKIP)

Uses advanced encryption system (AES) in addition to TKIP

AES method combines a key and a 128-bit block of unencrypted data to produce a block of different encrypted data.

WEP only uses 40-bit key

Wi-Fi Security802.11i Standard Acceptance Impact Business community interest expected to

skyrocket in next year or two Vendors already rolling out firmware enabling

802.11 compliant security protocols Immediate impact by eliminating VPN

infrastructure except when connected remotely, such as a hotel

Performance penalty for 802.11i functionality unknown

Summary

Wireless LAN Applications

Wireless LAN Technology

IEEE 802.11 Standard

IEEE 802.11 Protocol Architecture

IEEE 802.11 Relatives

Wi-Fi Security