Public Access Mobility LAN: Extending The Wireless Internet into The LAN Environment

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Public Access Mobility LAN:Extending The Wireless Internet into The LAN EnvironmentJUN LI, STEPHEN B.WEINSTEIN, JUNBIAO ZHANG,NAN TU . NEC USA Inc.

IEEE Wireless Communications June 2002報告者 : 通訊所 鍾國麟

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Introduction

Aim is to meet Ubiquitous access High data rate Local services

Need for Wireless LAN environments

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Introduction (cont’d)

Architectural guidelines for WLAN environments Large-scale IP-based Supporting mobile/portable

appliances

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Introduction (cont’d)

公眾 WLAN 目前的問題 End User 網路環境提供業者 (Hotel, 機場 , 餐廳 ..etc) ISPs

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交 200 元無線上網

User

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買 xxx 上網易付卡

漫遊 ? QoS ?

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User 的需要 :1. 帳號 , 密碼 , 帳單能統一2. Mobility3. Qos

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提供無線場地的業者1. 愈多人來上網愈好2. 設備維護3. 管理方便4. 拆帳5. 商業形像 ..etc

ISPs…

ISP 業者1. 無線環境範圍愈大愈好2. 設備維護方便3. 提供 USER 不同 QoS4. 提供 Mobility

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PamLAN

IP-based Public Access Mobility LANSupports Internet Access via WLANs Multiple air interfaces Multiple virtual operators(isp, 電信業者 ) Location dependent services Local IP mobility QoS (within wired network)

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PamLAN business model

Network operators Hotel, airport, ...

Third-party service providers (like ISPs) Franchises obtained from PamLAN

operator Also called: virtual operators

End users

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PamLAN

May have multiple LAN segments Airports, hotels, universities, ...

Can be built on existing LANs By adding wireless access points

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PamLAN vs. Cellular Systems

Even 3G mobile communication systems would not be sufficient for evolving Internet applications 384 kb/s outdoors, 2 Mb/s indoors

downstream burst rates Intrinsic problem: providing continuous

coverage in reserved spectrum Investment/Capacity scalability???

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PamLAN vs. Cellular Systems

WLANs have free spectrumProblem: Potential interfarence i.e. IEEE 802.11b & Bluetooth

Property owners may be agreed or enforced on compatibility

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Promises of PamLAN

Addresses problems in current WLANs Lack of public access Being tied down to a single access point Single air interface

Not a breakthrough in technological capacitiesCombination of available technologies

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Architecture

PamLAN/VOLAN/VLAN hierarchy PamLAN: multiple virtual operators VOLAN: Virtual Operator LAN

Extends VLAN capabilities across subnetworks

VLAN: Virtual LAN Implements user group feaures Simulates a physical LAN on a

multisegment LAN environment

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PamLAN

ISPs

VOLAN1

vlan1 vlan2vlan3 vlan4

VOLAN2

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Architecture (cont’d)

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Architecture (cont’d)

Switched Ethernet LANAccess Points Supporting IEEE, Bluetooth,

Cellular, ... IP-based access router with proxies

Gateway routers

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Architecture (cont’d)

QoS is supported by Ethernet Switches CSMA/CD + full duplex (no contention)

Integration of Cellular IP & Mobile IP for supporting mobilityMPLS (Multi-Protocol Label Switching) Brings QoS across multiple LAN segments

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Large Scale PamLAN

For single VLAN QoS can be easily supportedFor large scale WLANs? Intermediate routers work at layer 3

Layer 2 information is lost Source & destination addresses must

be used for VOLAN membership Intermediate routers must know all IP

addresses for VLAN mapping

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Large Scale PamLAN (cont’d)

Solution: MPLS Simple & efficient Access points & Internet gateways

handle VOLAN provisioning Intermediate routers are shielded

from details

VLAN for grouping traffic per VOLANMPLS for whole PamLAN

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MPLS (Multi-Protocol Label Switching)

Tunnels traffic between gateways & access points Intermediate routers only examine MPLS

labels, which imposes a path

Forwarding Equivalence Class (FEC) Formed based on VOLAN membership &

QoS

FEC is inserted in MPLS label Used for 802.1p priority within VLAN

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MPLS (cont’d)

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MPLS (cont’d)

Traffic engineered paths can be set up among access points and Internet gateways according to service contracts between PamLan & virtual operators

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Protocol Stack

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Security Issues

Mutual authentication user 和 AP 都需經過 Virtual operators‘s

RADIUS 認證Secure Channel Establishement Public-key-based secure channel

establishment

Authorization Filtering at the access point

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Mutual Authentication

IP-based authentication 5 Basic Steps: MN 經由 AP 取得 IP (DHCP) MN Login session

access point: relay agent to virtual operator(ISP’s RADIUS)

Challenge-responce protocol for authentication

Public key for securing channel

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Mutual Authentication (cont’d)

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MN AP/Radius client Radius(RS)UID

A(UID,Krc)Krc 是 ap 和 Radius serve 互相知道的 key

A(M,k) MD5 系統

UserID

A(UID,s1,E(E(s1,kmu),krc)),krc)Kmu 是 MN 和 RS 之間的 keyUID,s1( 亂數 )

UID,s1,E(s1,kmu),s2A((UID,E(s1,kmu),s2,krc)

A((UID,s1,E(E(s1,kmu),krc),Pkmu),krc)

Pkmu 是 mn 的 public key

UID,EP((E(s2,kmu),SK,Pkmu)

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Securing Channel

After authentication AP 有 user 的 profile (public key, qos 等

級 , 會員資料等 ..) AP sends session key encrypted

under the corresponding public key IPSEC together with ESP can be used

for security at IP layer depending on user requests

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Authorization Control

Based on user credentials, packets can be filtered at the access point 使用者可以經由 PamLAN 上 Internet 使用者可以使用當地的 printer 或是其他服

務

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Accounting

3 possible charging policies Flat-fee based

PamLAN 管理員和 ISP 收取一定費用，則該 isp user 可以無限制使用

Per-session ISP 依 USER 使用時間收錢 .(IDLE….? )

Usage based( 計量 ) Avoidance dispute by digital signature

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Mobility Issues

Micromobility Roaming within PamLAN

Possible approaches Cellular IP: refreshing router contents

can be a burden for too many users MPLS based: only end points have to

update location Old, new access points and Internet

gateway need to be informed

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Mobility Issues

Fast handoff 一個 MN 移動到了新的 AP 還要在做一次認

證是很浪費時間的

Move user profile from old AP to the new AP

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Fast handoff flow

新 AP 向舊 AP 拿取 user 的 profile(Public-key, Session-key,IP, policies….)舊 AP 向 Radius 發出訊息終止現在的 session 計費 .新的 AP 產生新的 Session key, 在將新的 S-KEY和舊的 S-key 用 user 的 Public-key 封裝給 user.User 比對 Session key 資料 , 用新的 S-key 和新AP 傳輸資料新 AP 上的 IP filter 資料由舊 AP 取得 , 同時發訊息給 Radius 開始計費 .

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Experimental Implementation

一台 12port switch 三台 PC,OS:Linux 二台 PC 裝了 802.11b 卡當成是 AP

測試方法 1. 確認 Vlan 和 diffserv 可以在 switch 上使

用 2. 結合 cellular ip protocol 在這個網路上 3. 實作基本的 AAA 功能

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Experimental Implementation

Mobility Cellular IP

Linux Kernel(AP) IP Filter IPSEC

OpenSource Radius client(AP)

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Further work

MPLS-based MobilityQoS admission control

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Conclusion

ExtensibleMultiple servicesMultiple air interfacesAre all appliances capable of handling PKC opreations?