Post on 07-Jan-2016
description
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