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R&D N 42/2004

Thomas Haslestad, Paal Engelstad

Wireless Local Area Network; Evolution of standard and products from IEEE 802.11 and IETF

Company INTERNAL

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Company INTERNAL Wireless Local Area Network; Evolution of standard and...

R&D Scientific Doc.

N 42/2004

Title Wireless Local Area Network; Evolution of standard and products from IEEE 802.11 and IETF

ISBN ISSN 0809-1021 Project No TFTW3 Program Security Gr. Company INTERNAL No. of pages Date 2004.04.15

Author(s) Thomas Haslestad, Paal Engelstad

Subject headings WLAN, IETF

Abstract Lyrics in abstract ...

Wireless Local Area Network; Evolution of standard and... Company INTERNAL

Telenor Communication AS 2004.04.15

All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage and retrieval system, without permission in writing from the publisher.


Contents

1 Introduction..........................................................................................1

2 Wireless Local Area Network (WLAN) ..........................................2 2.1 Standardization ...........................................................................................2 2.1.1 Approved standards.....................................................................................3 2.1.1.1 802.11a (5GHz deployment) ...................................................................3 2.1.1.2 802.11b (2.4GHz deployment) ................................................................3 2.1.1.3 802.11h (improved radio performance for 5GHz deployment) ...................4 2.1.1.4 802.11g (improved bitrates for the 2.4GHz band) .....................................4 2.1.1.5 802.11i ( improved security) ...................................................................4 2.1.2 Ongoing standardization..............................................................................5 2.1.2.1 Quality of Service from Task group e (802.11e) .......................................5 2.1.2.2 Japanese regulatory amendments from Task group j (802.11j) ...................5 2.1.2.3 Radio Resource Measurements from Task group k (802.11k) ....................5 2.1.2.4 Enhancements for Higher Effective Throughput from Task group n (802.11n) 6 2.1.2.5 Support for Fast Roaming from Task group r (802.11r).............................6 2.1.2.6 MESH Networking from Task group s (802.11s) ......................................6 2.1.3 Potentially standardized functionality ...........................................................6 2.1.3.1 WAVE –SG (Wireless Access for the Vehicular Environment) .................7 2.1.3.2 WPP –SG (Wireless Performance Prediction) ...........................................7 2.1.3.3 WNM –SG (Wireless Network Management)...........................................7 2.1.3.4 WIEN –SG (Wireless Interworking with External Network)......................7 2.2 Products .....................................................................................................8 2.2.1 Status .........................................................................................................8 2.2.2 Roadmap....................................................................................................9

3 IEEE 802 & IETF ................................................................................11 3.1 Introduction..............................................................................................11 3.2 IETF Protocols most commonly deployed in WLAN...................................11 3.2.1 EAP (Extensible Authentication Protocol) ..................................................11 3.2.2 EAP Authentication Methods .....................................................................11 3.2.3 RADIUS and DIAMETER........................................................................12 3.2.4 PPPoE (Point-to-Point Protocol over Ethernet)............................................13 3.2.5 IPsec VPN................................................................................................13 3.2.6 Virtual LAN (VLAN)................................................................................13 3.2.7 MIP..........................................................................................................13 3.3 Areas of cooperation .................................................................................14 3.3.1 CAPWAP.................................................................................................14 3.4 Products ...................................................................................................14

4 Conclusion .........................................................................................16


1 Introduction

Wireless local area network (WLAN) is in constant evolution in order to support more advanced network constellations and services of more critical character. WLAN in itself is rather useless for the end-user unless sufficient protocol functionality is supported in the network. Evolution exists also here that affects the possibilities within WLAN systems. This document identifies the recent status within the IEEE 802.11 and IETF that is related to the functionality we can exploit in a WLAN deployment. Some consideration on where and when to deploy the different technologies is maintained in the document.


2 Wireless Local Area Network (WLAN)

Wireless Local Area Networks is a dynamic and flexible option to wired local area networks. With raw bit rates upto 54 Mbps, improved security and low associated cost WLAN offers a viable alternative to wired infrastructure for the industry. The most common deployments are WLAN for local intranets within company buildings and as a flexible wireless deployment in private homes. Many alternative deployments for WLAN have appeared, but the most common of these are WLAN for public Internet access (hotspots).

2.1 Standardization

The existing standards for WLAN are today the following:

ETSI BRAN (The European Standardization organization): HiperLAN/1 & HiperLAN/2

MMAC HSWA (The Japanese Standardization organization): HiSWANa & HiSWANb

IEEE 802.11 (The American Standardization organization): The entire 802.11 series

Even though the most technologically efficient standard of the one mentioned above is HiperLAN/2 this is not the standard that has achieved market acceptance. IEEE 802.11 is today the WLAN standard family that has nearly 100% of the market. This document will therefore focus on the 802.11 standards since it is evident that this is not to change in foreseeable future.

The IEEE 802.11 specifications are wireless standards that specify an "over-the-air" interface between a wireless client and a base station or access point, as well as among wireless clients. The 802.11 standards can be compared to the IEEE 802.3 standard for Ethernet for wired LANs. The IEEE 802.11 specifications address both the Physical (PHY) and Media Access Control (MAC) layers and are tailored to resolve compatibility issues between manufacturers of Wireless LAN equipment.

Wi-Fi Alliance is an organization heavily involved in the making of the WLAN success. This organization is deployed by the WLAN industry in order to produce specifications and a test regime for the provisioning of interoperable products between the vendors to which they provide certification. Additionally this organization is heavily involved in promoting the usage of WLAN and has several initiatives in order to ensure the correct functionality for several different usage scenarios.

In order to understand the meaning of the current status of the different standards and/or amendments it is necessary to present a short introduction to the process of standardization within IEEE.802. The figure below identifies the entities involved in the standardization process. The process of raising a standard from the task group to RevCom through the working group and sponsor group is performed through a voting and commenting system called ballots.


2.1.1 Approved standards

The main IEEE 802.11 standard was approved as early as 1999 but, has and is continuously being evolved with additional functionality. This results in numerous amendments. The following relevant amendments are approved as part of the standard.

2.1.1.1 802.11a (5GHz deployment)

The scope of the project was to develop a PHY to operate in the allocated UNII band. Work has been completed on the ISO / IEC version of the original Standard as an amendment - Published as 8802-11: 1999 (E)/Amd 1: 2000 (ISO/IEC) (IEEE Std. 802.11a-1999 Edition).

Key Characteristic:

• Bitrate: 54 Mbps

• Max EIRP: 50mW

• Typical coverage: 30-50 meter (wall damping)

• Frequency band in Europe: 5,150 – 5,250 GHz

2.1.1.2 802.11b (2.4GHz deployment)

The scope of the project was to develop a standard for a higher rate PHY in the 2.4GHz band. Work has been completed and is now part of the Standard as an amendment - Published as IEEE Std. 802.11b-1999.

Key Characteristics:

• Bitrate: 11Mbps

• Max EIRP: 100mW

• Typical coverage: 50 – 150 meters


Standard

RevCom

IEEE 802 Sponsor Group

Working Group

Task Groups

Study Groups

Ad-hoc Groups

Finished

Review Process. Approve or reject

Review DRAFT. Approve or reject

Review DRAFT. Approve or reject

Debate and produce a DRAFT Std.

Gain support and submitt a Project Authorisation Request (PAR)

Initial Idea for a standard or improvement


2.1.1.3 802.11h (improved radio performance for 5GHz deployment)

The main focus of Tgh was to enhance the current 802.11 MAC and 802.11a PHY with network management and control extensions for spectrum and transmit power management in 5GHz license exempt bands, enabling regulatory acceptance of 802.11 5GHz products. Provide improvements in channel energy measurement and reporting, channel coverage in many regulatory domains, and provide Dynamic Channel Selection and Transmit Power Control mechanisms


• DFS & TPC in accordance with European regulatory constraints which allow 802.11a compatib le products to extend the transmit power and frequency band to:

o Max EIRP: 200mW for the lower band / 1W for the upper band

o Frequency band: 5,150 – 5,350 GHz / 5,470 – 5,725 GHz

2.1.1.4 802.11g (improved bitrates for the 2.4GHz band)

The scope of this group was to develop a new PHY extension to enhance the performance and the possible applications of the 802.11b compatible networks by increasing the data rate achievable by such devices. This technology will be beneficial for improved access to fixed network LAN and inter-network infrastructure (including access to other wireless LANs) via a network of access points, as well as creation of higher performance ad hoc networks.

Equipment compliant to the standard is available on the market today.


• Bitrate: 54 Mbps

• Max EIRP: 100mW

• Typical coverage: 30-50 - 150 meter (wall damping)


• Backward compatible with 802.11b

2.1.1.5 802.11i ( improved security)

The scope of this group is to enhance the 802.11 Medium Access Control (MAC) to enhance security and authentication mechanisms. The enhancements led to mechanisms that secure integrity and improve the confidentiality over the radio interface in addition to providing a layer 2 support of upper layer authentication mechanism.

The industries need of enhanced security led in 2002 the WiFi alliance to create a interim solution for increased security. It was at that time widely acknowledged that the existing security features where depreciated and the industry was in desperate need for enhanced security functionality to be standardized. WPA (WiFi Protected Access) was generated from draft 3.0 of the already initiated work on security amendment from IEEE 802.11.

WPA was released in 2003 and made mandatory functionality for interoperable certification from September 2003. WPA maintains the following key characteristics:

- Authentication and Association

- Authenticated Key Management Protocols


o 802.1x with pre-shared key or EAP authentication

- AP Broadcast of cipher suite and Authentication mode

- Encryption and Integrity check

- No Integrity check of management and control messages

- Unchanged .11MAC State machine

Due to the success of WPA the entire security amendments of 802.11i will be marketed as WPA2. WiFi Alliance is in the process of setting up the certification test for WPA2 and will within 6-12 months make WPA2 a mandatory feature for WiFi certifications. WPA2 has the following key features in addition to the ones for WPA:

- Advanced Encryption Specification AES – CCMP and the concept of pure-RSNSupport for secure fast handover

2.1.2 Ongoing standardization

The following initiatives are in various stages of standardization:

2.1.2.1 Quality of Service from Task group e (802.11e)

The scope of this group is to enhance the current 802.11 MAC to expand support for LAN applications with Quality of Service requirements. Provide improvements in security, and in the capabilities and efficiency of the protocol. These enhancements, in combination with recent improvements in PHY capabilities from 802.11a and 802.11b, will increase overall system performance, and expand the application space for 802.11. Example applications include transport of voice, audio and video over 802.11 wireless networks, video conferencing, media stream distribution, enhanced security applications, and mobile and nomadic access application.

The standard is expected to be approved by the end of 2004. The current state of the draft is considered fairly stable but still some revising and comment resolution is to be made. It is expected that the amendment is implemental in firmware.

2.1.2.2 Japanese regulatory amendments from Task group j (802.11j)

The scope of this group is to enhance the 802.11 standard and amendments in order to add channel selection for 4.9 GHz and 5 GHz in Japan to additionally conform to the Japanese rules for radio operation. A success will allow the 802.11a PHY to operate in the mentioned bands.

Have reached a reasonable stability and is expected to be approved by the end of 2004.

2.1.2.3 Radio Resource Measurements from Task group k (802.11k)

The scope of TGk is to define Radio Resource Measurement enhancements to provide interfaces to higher layers for radio and network measurements in order to support services such as roaming and coexistence to external entities. The mechanisms and functions available from this amendment will be a number of available parameters measured at the the lower layers in order for upper layer mechanisms to exploit these in for example O&M and mobility systems. TGk is cooperating with the needs of TGr in order to make available the measurements that TGn needs for achieving mobility within an ESS.

The current status shows a few unresolved issues but is in the process of voting to go to sponsor ballot.


The functionality specified within this group may be expected to be available on the market by 2005.

2.1.2.4 Enhancements for Higher Effective Throughput from Task group n (802.11n)

The scope of this project is to define an amendment that shall define modifications to both the 802.11 physical layers (PHY) and the 802.11 Medium Access Control Layer (MAC) so that modes of operation can be enabled that are capable of much higher throughputs, with a maximum throughput of at least 100Mbps, as measured at the MAC data service access point (SAP).

The group has finished the requirement document and issued a call for proposals where the total of 62 proposals where received. The planned steps are currently the following:

September 2004 - Proposal presentations

July 2005 - First Letter Ballot

May 2006 - First Sponsor Ballot

November 2006 - Excom approval

The draft standard is planned to reach stability 2-3Q 2006

2.1.2.5 Support for Fast Roaming from Task group r (802.11r)

The scope of this project are enhancements to the 802.11 Medium Access Control (MAC) layer to minimize or eliminate the amount of time data connectivity between the Station (STA) and the Distribution System (DS) is absent during a Basic Service Set (BSS) transition, limited to the state necessary for the operation of the MAC. The Project Authorization Request (PAR) applies only to the STA<->Access Point (AP) state within the same Extended Service Set (ESS), and not to the Independent Basic Service Set (IBSS) case. Security shall not be decreased as a result of the enhancement. The Task Group will define timing criteria and timing conditions.

The draft standard is planned to reach stability 2-3Q 2006

2.1.2.6 MESH Networking from Task group s (802.11s)

The groups plan is to develop an Extended Service Set (ESS) Mesh with an Wireless Distribution System (WDS) using the IEEE 802.11 MAC/PHY layers that supports both broadcast/multicast and unicast delivery over self-configuring multi-hop topologies. The IEEE 802.11-1999 (2003 edition) standard provides a four-address frame format for exchanging data packets between APs for the purpose of creating a Wireless Distribution System (WDS), but does not define how to configure or use a WDS. The purpose of the project is to provide a protocol for auto-configuring paths between APs over self-configuring multi-hop topologies in a WDS to support both broadcast/multicast and unicast traffic in an ESS Mesh using the four-address frame format or an extension.

The group is recently established and is in the process of defining a requirement document. It aims to reach a stable draft during 2006 for submission to REVCOM in January 2007

2.1.3 Potentially standardized functionality In order to investigate the need, possibility and the interest of placing additional functionality within the 802.11, study groups on various issues are formed.


2.1.3.1 WAVE –SG (Wireless Access for the Vehicular Environment)

In 1999, the FCC allocated 75MHz of spectrum at 5.850-5.925 GHz, right above the UNII band, for a “wireless link to transfer information between vehicles and roadside systems” and between vehicle systems. This study group aims to provide enough ground to form a new task group in order to develop an amendment to extend and modify the 5GHz PHY for the DSRC (Dedicated Short Range Communication) band, and incorporate necessary MAC changes. MAC changes apply only to the use of this specific PHY in this band. The existing IEEE 802.11 standards must be amended to make them suitable for interoperable communication to and between vehicles. The transport environment, which includes the speed of the vehicles (speeds up to a minimum of 200 km/h must be supported) and the very short latencies (some applications must complete multiple data exchanges within 4 to 50ms) are the primary, but not the only reasons for this amendment.

The group has currently finalized the PAR and 5 criteria. The creation of a task group has been delayed due to disagreements within the working group whether this should be a task group or a working group of its own. The ASTM standard E2213 (Telecommunication and information exchange between roadside and vehicle systems) exists as an unofficial draft in IEEE format. The initial plan for this work was to achieve a stable draft for approval late 2006.

2.1.3.2 WPP –SG (Wireless Performance Prediction)

Due to the number of amendments and new states/functionalities that are incorporated into the standard it becomes hard to predict the achieved performance. In short: The sum of the sub-component specifications is NOT equal to the End-to-End system performance. The performance experienced in real installation environments varies significantly because of a number of complicated, and interrelated factors. Currently there is no generally accepted method for predicting or evaluating this performance. What is needed is a end user, device level, test and analysis method(s) that provides a good degree of confidence in predicting the coverage, throughput and directivity performance of IEEE 802.11 (and potentially other) wireless devices.

The group has achieved an approved PAR and 5 criteria and will at the next meeting become a task group of its own. It will then initiate the work on defining test schemes requirements. WNM –SG (Wireless Network Management)

Produce a document that will provide Wireless Network Management enhancements to the 802.11 MAC and PHY, to extend prior work in radio resource measurement to effect a complete and coherent interface for managing wireless networks. The security issues related to remote management are currently within the scope of the work.

The group is working on its par and 5 criteria for adoption of its whish to become a task group, which have already been defeated ones at the working group plenary.

2.1.3.4 WIEN –SG (Wireless Interworking with External Network)

The purpose of this group is to define necessary amendments to the base standard in order to establish a harmonized approach for interworking with external networks such as xDSL and 3G networks. The group continues on the work done in ETSI BRAN and WIG which initiated the 3G-WLAN interworking concept. The focus is to maintain the functions within the WLAN environment which the 3GPP regards as a black box in the interworking scenario. Current status is that a number of issues that is necessary for 802.11 to deal with is identified and a PAR and 5 criteria is going to be completed within September giving the possibility for establishing a task group in November this year.


2.2 Products

The main drivers of the WLAN market today are companies like Intersil, Cisco, Intel, D-Link and Nortel. .

Intersil have been the main chip vendor together with Agere who has been struggling lately. Intel with their centrino chip is gradually becoming one of the largest players on the chip market for WLAN.

Cisco has the main operator market for larger WLAN constellations due to their advanced management systems but it is D-Link who has the largest market share on WLAN hardware with their main consumers within the private segment. D-Link uses chipsets from both Texas Instrument and Agere.

All companies mentioned here are vendors of both terminal equipments and access points.

2.2.1 Status

Standardized functionality:

• Products supporting all of the functionalities identified above in 2.1.1 are available on the market today with the exemption of WPA2, which will be available shortly.

o 801.11a compliant products are not allowed to exploit the entire 5GHz band unless implemented with the 802.11h amendment in Europe. 802.11a products have less than 1% market share according to a Synergy Research.

o 802.11g products shall be backward compatible with existing 802.11b products if certified by WiFi Alliance. Together with 802.11b has 802.11g products the majority of the market shares

o WPA functionality may be upgraded on existing equipment through software.

§ Note. If new equipment is purchased with WPA functionality, the hardware may be scaled for a simple software upgrade to WPA2. If no hardware adjustments are done for migration towards WPA2, new equipment will be necessary to purchase.

• Access points in support of all three PHY-layer functionalities (a, b& g) simultaneously are available from several vendors.

Proprietary functionality/solutions:

• Proprietary support of fast roaming in support of VoIP solutions exists from a number of vendors such as Cisco.

• Proprietary solutions for the creation of “switched WLAN” exist from several vendors such as Proxim and Aruba. A switched WLAN network creates support for fast mobility within the network and centralizes the MAC level functionality in the network, which may provide for lower implementation costs compared to a more conventional “fat-AP” structure.

Additional related functionality:

• An access point may today have distributed power over Ethernet which most vendors support in order to lower the implementation cost of WLAN. (i.e. no cost of electrical cabling)


2.2.2 Roadmap

In chapter 2.1.2 it was identified 5 new amendments of the standard expected to be approved within a 3 years period. These amendments are to provide enhanced QoS, RRM and higher throughput in addition to support for Fast Roaming and MESH functionality. Estimation of when such functionality is available on the market is very much dependent upon three factors:

• The expected market uptake. Does a demand for the functionality exist?

• The amendments impact on existing products

• WiFi alliances ability to set up certification routines for interoperability.

Quality of Service support over the radio interface has been expected to be in demand due to its inherent improvements in networks that are experiencing heavy loading and due to its need for future and existing time sensitive applications such as Voice over IP. The QoS amendment is a pure MAC layer amendment and will therefore not require new hardware when upgrading existing infrastructure. The WiFi Alliance has not indicated when and if QoS support will be mandated for certification. It is however reasonable to believe that products supporting QoS and QoS upgrades is available during 2005.

Radio Resource management is a functionality that clearly is in demand from the operators of larger WLAN constellation. This amendment provides a platform to incorporate specialised management services independently of the vendors. It is so far uncertain whether or not the amendment will affect the existing hardware products or become a pure firmware upgrade. WiFi alliance has not indicated any associated timeline for this upgrade in their certification roadmap. The availability of products on the market with RRM functionality is therefore highly uncertain. Larger vendors like Cisco have today proprietary solutions for this type of functionality and are maintaining a large market share due to this.

Higher Throughput is a natural evolution of the systems capabilities. It is believed to be a necessity in order to be a competitive solution for in-house cabling. The corporate market will require higher throughput capabilities due to the increasing load that is put upon the corporate networks. For public hotspots and the private households the need for higher throughput is questionable. The main bottleneck is today not the radio interface but the feeding link to the spot. It is on the other hand more than sufficient argument to believe that this amendment will find its way to the marketplace within 2007.

Fast Roaming is a name of the intended functionality that is incorrect in a cellular context. The intended functionality is to provide for mobility between different APs (not necessarily different operators) in a manner that can support real time applications. This type of functionality is by all means favourable for the intended mobile future that is foreseen for the corporate and the public market by most communities. For the private household this is highly unlikely to become a feature that is wanted.

MESH is a feature that may be used for extending the coverage of the WLAN network and may provide a method for deploying more dynamic networks. For public operators this is a particular interesting feature but requires careful implementations. Private users and corporate users may find the feature useful for several purposes such as creating ad- hoc networks. The main drivers for this feature will on the other hand be the public operators due to the potential complexity of understanding the feature for the private users. So far any ad-hoc networking with for example bluetooth have not been in demand from the private users. It is therefore questionable if this feature will be on the market at the time the standard is completed.


3 IEEE 802 & IETF

3.1 Introduction

IEEE and IETF are two organisations that are extremely well suited to each other. IEEE being the organisation behind Ethernet bases much of their work towards an Ethernet interface. IETF has IP as their main protocol and IP is streamlined with Ethernet. It is therefore natural that most of the two organisations new standards co-operate in a manner that only can be described as good. Additionally both organisations are contribution driven at a personal rather than company level of often the same persons in both organisations.

3.2 IETF Protocols most commonly deployed in WLAN

In the below sub-chapters a number of different IETF produced protocols are presented. The commonality between these protocols is that they are capable of playing a vital role in a commercially available WLAN network.

3.2.1 EAP (Extensible Authentication Protocol)

Security and authentication are areas in constant change. Security requirements and usage requirements can vary and new authentication methods are developed to address new demands. The purpose of EAP was to provide a generic protocol to wrap nearly any kind of authentication method into it. Thus, by letting the link layer (e.g. 802.11 WLAN) support EAP, it can easily accommodate any authentication method developed for EAP.

The encapsulation of EAP over 802.11 WLAN is defined in 802.11i and in WPA (WiFi Protected Access). This encapsulation is often referred to as 802.1X, since it is very similar to the 802.1X used on wired media. (The enhancements of 802.1X for WLAN are reflected in the generic specification of 802.1aa).

EAP also provides an architectural authentication framework, where the WLAN STA acts as a "supplicant" and the WLAN AP acts as an "authenticator". The authenticator will often not participate in the actual authentication of the supplicant. Instead, all EAP traffic is passed through to an "Authentication Server". As a de facto standard today, the authenticator uses the RADIUS protocol to speak to the authentication server, which is then called a RADIUS server.

Furthermore, EAP also provides a generic key hierarchy and a framework for key management.

The new EAP specification can be found in RFC 3748.

3.2.2 EAP Authentication Methods A large number of EAP authentication methods have been developed or are under development. These include EAP TLS, EAP SIM, EAP AKA, EAP TTLS, PEAP, LEAP, EAP SRP, EAP GSS and so forth. In particular, it is especially worth mentioning


• EAP-TLS: TLS (defined in RFC 2246) is a de facto standard for authentication with 802.11i, since it is well tested, widely deployed, and fulfils all requirements of 802.11i. Unlike other widely used methods, TLS works well in an 802.11i setting. EAP-TLS (defined in RFC 2716) is simply a TLS handshake conducted over EAP. TLS can provide both mutual and one-way authentication, requiring a certificate on either side or on only one side, respectively.

• EAP TTLS (Tunneled TLS) / PEAP (Protected EAP): The principle is that you only have a few certificates to perform an initial one-way TLS authentication of the network to the user. After a secure tunnel is established, other EAP methods based on for example tokens or passwords can be used for further authentication. However, an attack that eliminates the benefits of PEAP was recently identified.

• EAP SIM/EAP-AKA: The objective of EAP-SIM is to reuse existing GSM-style authentication, and run in over EAP as unchanged as possible. A problem of SIM authentication, however, is that it produces a session key of only 64 bits, while an EAP master key requires at least 128 bits. As a solution, the SIM sends multiple challenges during the EAP process, and each challenge results in a 64-bit key. Each 64-bit key is combined to form the EAP master key. EAP-SIM also introduces the concept of IMSI-privacy, where the server and the mobile device agree on a pseudonym to be used for the next authentication. Finally, SIM authentication is originally one-way, while 802.11i requires mutual authentication. As a solution, the mobile device provides a nonce value at the start of the negotiation. The network must return this value in an encrypted form by the end of the negotiation. EAP-AKA is based on quintets instead of triplets, which is an important feature of UMTS. It also provides mutual authentication (i.e. also of the network), and provides a higher layer of security, e.g. in terms of using stronger keys.

• LEAP (Lightweight EAP): This method is a proprietary approach introduced by Cisco to assist with the key management of WEP (Wired Equivalent Privacy). As such, LEAP was the first WiFi related security approach to be based on IEEE 802.1X and has been deployed in many corporate sites

3.2.3 RADIUS and DIAMETER

For home users it is feasible to configure same pre-shared key on both the WLAN AP and the WLAN STA. For network operators (such as telecom operators, Internet Service Providers, Hot Spot operators etc.) where the mobile user can associate with a large number of access point, storing a key for each user on each access point mounts to a nearly unmanageable task. Instead, network operators store the subscribers' keys on a centralized authentication server.

RADIUS is the de facto standard for communication of EAP over IP, and hence the standard for communication between an access point (such as a WLAN AP) and the authentication server. It provides message types and message formats, and a number of attributes to be included in the messages. The RADIUS specification is found in RFC 2865.

RADIUS was originally designed for wired dial-up usage, where users called the same phone number and always connected to the same RADIUS server. DIAMETER was developed to address the lack of support for a roaming scenario where a roaming user would associate with a WLAN AP that is not directly associated with the RADIUS server of the user.

Status: Due to the high implementation base of RADIUS servers, it has proved hard to covert to DIAMETER. RADIUS (with extensions to better support roaming) will probably


still be used in the future. The AAA WG of the IETF is, however, has recently been initiating work on a future AAA protocol, based on the DIAMETER specification.

3.2.4 PPPoE (Point-to-Point Protocol over Ethernet)

PPPoE was developed to run PPP (the Point to Point protocol) over an IEEE 802.3 Ethernet. As 802.11 uses 802.2 and complies with 802.3, PPPoE can be used also over a WLAN. PPPoE specifies a way to send PPP messages over an Ethernet frame. It also specifies a discovery mechanism used to allow nodes to discover that PPPoE can be run on the Ethernet to with the node is connected.

A network operator may run PPPoE on a WLAN AP. The WLAN AP can then relay the PPP session (e.g. via PPP-over-ATM) to an access router further back in the core network. As for the client side (i.e. the WLAN STA), Microsoft supports PPPoE on their newest operating systems.

3.2.5 IPsec VPN

802.11 WEP was broken many years ago, and provides virtually no security of much value. While waiting for 802.11i and WPA to address the need of WLAN security, many corporations have solved security issues at the IP layer, instead.

With this security solution, the WLAN access is considered not secure. Instead, the clients (or WLAN STA) uses the WLAN AP to get access to a VPN server further back in the network. The VPN is normally based on IPsec secure tunnels. Furthermore, IKE (which also belongs to the IPsec suite of protocols) is often used to set up a secure session with security associations and so forth with the VPN server.

3.2.6 Virtual LAN (VLAN) Isolation of traffic from access points is a crucial technique to improve security. A common technique (to avoid having to run new cables) is to reuse the existing network and to use Ethernet Virtual LAN to link various access points to the same Ethernet segment. VLAN is thus a protocol that will often be used together with the IPsec VPN solution described above.

3.2.7 MIP Mobile IPv4 (MIP4) is a standard that allows users to roam between different WLAN APs, using the same IP address (called the MIP4 Home Address). The STA registers with its home agent (HA) and will get incoming traffic forwarded to the MIP4 Foreign Agent located on the WLAN AP. When moving to a new WLAN AP, it re-registers again with the HA, and get traffic of ongoing sessions forwarded via the new AP.

MIPv4 is not widely deployed. For users surfing the WWW or accessing E-mail or acting as clients to other services provided on the Internet, being continuously available by its home address is not of particular interest. Furthermore, the sessions are of so short duration that it often would be over-engineering to deploy MIP4 to avoid breakage in the session during a change of WLAN AP.


MIPv4 can be of interest for users implementing Voice over IP, where the session is ongoing and where the user wants to be continuously available. For this purpose, SIP provides a session-specific solution.

Solutions have been proposed to run MIP4 in environments with NATs and VPNs.

MIP6 is mobile IP for IPv6, and its deployment depends on deployment of IPv6.

3.3 Areas of cooperation

3.3.1 CAPWAP A hierarchical network design is often preferred in systems that require coordination between the access points. For example, a hierarchical design is useful in a cellular system with frequency reuse; in systems that requires roaming and fast mobility between different access points, and so forth. 802.11 WLAN, on the other hand, has no build in hierarchical design. Normally a WLAN AP is stand-alone, and is co-located with a router. Although the standard allows for several WLAN AP interconnected by a backend distribution system (and a portal to a backend router), there is no concept of a back-end Access Point Controller.

CAPWAP is a working group of IETF that use a hierarchical architectural model where many WLAN APs are connected to the same back-end AP controller. The amount of WLAN control and management traffic that shall be passed through the WLAN AP and handled by the controller is an issue under discussion.

If management messages such association messages or authentication messages are passed through, STAs will automatically be allowed to move freely between different access points under the same controller, and no re-authentication is required. The controller may also control and optimise the frequency channels used by the different APs.

3.4 Products

IP-related WLAN products can be divided into three product categories for software and hardware: host-products (for the STA), access-router-products (for the AP) and backend server products.

Furthermore, the WLAN market can be divided into three market segments: the private segment (e.g. WLAN equipment for SOHO users), the public access segment (e.g. WLAN-equipment for hotspot users) and the corporate segment (e.g. WLAN equipment for the infrastructure of companies).

Host-products and access-router-products are sold in all market segments, while backend-server-products are often not useful for SOHO users, and most important in the public access and corporate market segments.

The STA-functionality is normally implemented in hardware, while the IP-related host-products running on top is normally implemented in software. Thus, Microsoft comprises an important vendor to support these products. Some products, however, such as VPN-clients and MIP-clients, may be offered by third party suppliers. The vendors are numerous but some examples on MIP-clients are Birdstep & Qualcom, and for VPN-clients companies like Cisco and Certicom are good examples.


Since most APs are incorporating an IP-layer router, the access-router-products are shipped with the WLAN AP. Thus, the vendors of these products are mainly the same as the vendors of WLAN AP: Cisco, Intel, Nortel, Intersil, and also a long list of small vendors.

Most of the AP-vendors (small or big) are offering router-access-products for the private market. The router software supports NAT-functionality, DHCP and so forth. Today WEP is used for authentication, but in the short future most products will probably incorporate support for 802.1X and EAP in order to at least support WPA authentication with pre-shared keys. Since some WLANs use PPP over the access line, some WLAN products also supports PPPoE.

Some AP-vendors target specifically the public access and corporate market segments that requires backend functionality. They may support Authenticator (Network Access Server) software for 802.1X/EAP-based authentication, or base the security solution on VLAN-tagging to play together with the IPsec VPN gateway located in the backend.

In addition to PPPoE, the router may also support other functionality for interworking with a backend system, such as RADIUS. Mobile IP will probably be first implemented in the public access and corporate market segments, and the Home Agent and Foreign Agent will then normally also be implemented in the AP. Note, however, that both the Home Agent and the Foreign Agent normally requires a public IP address to operate correctly.

Backend products are mainly targeted at managed networks, i.e. at the public access and the corporate market segments. The main vendors of RADIUS servers are companies like Funk, Cisco, Lucent and Alcatel, but also telco vendors like Ericsson and Nokia have their own Radius products. The main vendors of VPN gateways include Cisco, Nortel IPunplugged etc... The vendors of VPN gateways deliver also VPN client products.

CAPWAP is anticipated to be mainly targeted at the public access and corporate market segments where interaction and co-operation between many APs owned by the same organisation are required. How CAPWAP technology will be realized in the marketplace is still uncertain as CAPWAP technology is still immature. Aruba is a company on the other hand that has proprietary solutions for switched WLAN giving similar functionality to that of CAPWAP.


4 Conclusion

This document has indicated the recent evolution of WLAN and related technology in order to implement WLAN as an access technology in large and small scale.

It is shown a massive growth in functionality, which allows the operators great flexibility in the deployment and business offering. The great variety of functionality requires on the other hand knowledge and well thought through decisions when rolling out WLAN in order to be both future proof and cost effective in relation to the chosen business plan.

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