wifi hotspot service control design & case study overview

Copyright © 2003 Juniper Networks, Inc. Proprietary and Confidential www.juniper.net 1

WiFi Hotspot Service ControlDesign & Case Study Overview

Simon NewsteadAPAC Product [email protected]

mailto:[email protected]

2Copyright © 2003 Juniper Networks, Inc. CONFIDENTIAL www.juniper.net

Agenda Overview of different access

models Identifying the user location Secure access options Case studies (as we go)


MPLS Backbone

WiFi control - access modelsPPPoE

WiFi User with PPPoE client

(WinXP or 3rd party)

Access Controller

BRAS

Layer 2 Backhaul Transport

(Bridged1483, Metro E)

RADIUS

LNS*

PPPoE connection

AAAATerminate PPP session into VR/VRF or

tunnel on via L2TPFine grained QoS / bandwidth controlDynamic Policy Enforcement (COPS)

Lawful Intercept etc…

Policy Server


PPPoE access model - discussion Pros:

• Full per user control with inbuilt PPP mechanisms (authentication, keepalives etc.)

• Individual policy control per user simplified• Wholesale is simplified and possible at layer 2 and layer 3• Leverages the broadband BRAS model used in DSL – virtually no

changes Cons:

• Requires external client software (maybe even with XP) – no “auto launch” by default

• Only works in a bridged access environment; often not possible• Layer 3 access network requires use of native LAC client (BRAS acts

as LNS or tunnel switch) – client support issues


PPPoE access modelCase Study – Japanese Provider

WiFi Users with PPPoE client

[email protected]

Access Controller

BRAS

ATM Bridged

1483

RADIUS

Mapping of user to VR based on RADIUS, domain mapping

Bridging DSL

modem

Hotspot AP

Bridging DSL

modem

Backbone

WiFi VR

ISP VR

DSL Users with PPPoE client

[email protected]

WiFi operator network


MPLS Backbone

WiFi control - access modelsDHCP model – Web Login

WiFi User with inbuilt DHCP client.

Access Controller

BRAS

Layer 2 or Layer 3

Backhaul (any)

External DHCP

Server*DHCP

DHCP Server or Relay*Initial policy route to Web logon serverFine grained QoS / bandwidth control

Dynamic Policies (COPS)Accounting

Lawful Intercept etc…

Policy Server / Web Login Server


DHCP Web Login model - discussion Pros

• No external client software – inbuilt DHCP – lower barriers • Any access network – eg L3 wholesale DSL, routed Ethernet etc• Web Login provides extra options to operator (branding, advertising, location based content…)

Cons:• Wholesale options restricted eg- address allocation – NAT introduces complications (ALG support etc), no tunnelling with L2TP• Greater security / DoS implications – attack DHCP server, Web server• No autologon by default (manual web login process)

Need to introduce mechanisms to enable per user control in DHCP environment (mimic PPP)


DHCP / Web login Case Study – Telstra Mobile

Mobile centric service, launched in August 2003• Available in hotspot locations throughout Australia• Target of 600 hotspot locations in 2004 (Qantas, McDonalds,

Hilton etc)• International roaming through the Wireless Broadband Alliance• Time based billing; hourly rate• Login via a password delivered by SMS to a Telstra mobile

(credit card payment option for non-Telstra post-paid mobile customers)

Lowered barriers to uptake• No special WLAN subscription needed – casual pay-per-user• Captive portal logon using DHCP – no client software required


• User opens up webbrowser and triesto go to Google

• Session directedto captive portal on policy server

• Choice to entermobile phone number or username andpassword

• Mobile phonenumber entered

How it works - Step One


• One-time passwordsent via SMS touser’s mobilephone

• Received password entered into portal page

Step Two


• Upon successfulauthentication,captive portal isreleased and original webdestination isloaded.

• Mini-logout window to facilitate signoff.

• Usage billed to user’s mobile phone bill once finished

Step Three


• Allow greater flexibility of services eg-• Free access to Internet for 15 mins without

login… or• Internet access only, mail port blocked…or• Internet access but only at 64kbps…or• Walled garden content only

• Bandwidth can be dynamically increased and restrictions moved on user authentication and login

• Also helps protect against abusive or Worm users (eg- dynamically limit users down on sliding window basis; consumed more than x MB in past 15 mins)

Dynamic Policies


Per user control in a DHCP environment

Objective - make an IP host on single aggregated interface appear like its own IP interface• Treat hosts as separate logical (demultixed) IP interfaces

aka “Subscriber Interfaces”• Individual policy control on subscriber interface (linked to

policy server) – eg filters, bandwidth control • Ties into DHCP dynamically

VLAN 101

L3 Switch

User A:192.168.1.1

User B:192.168.1.2

Subscriber Interface AIP Demux 192.168.1.1Rate Limit Internet to

512k

Subscriber Interface BIP Demux 192.168.1.2

Rate Limit Internet to 2MPrioritise VoIP to strict

priority queueAdd firewall policies

Access Controller

BRAS


Access Controlle

rBRAS

1. IP assignments through DHCP & subscriber interface come up – Dynamic SI

DHCP relay point

Upstream Router

RoutingLayerAP

GE GE GEFE

2. HTTP redirected and show the portal web page3. Input subscriber ID and password

Radius

Weblogin - Policy

Server

Switch Layer

4. Radius authentication4. Download policies

Internet & service access

inbuilt DHCP server

1. (Access the portal & click on logout button) or (DHCP lease expired)

WEB login sequence

WEB logout sequence

2. Radius accounting2. (Reset policies) or (Delete subscriber interface) – Dynamic SI

Generic Web Login process


Location information – why?? Generates portal pages based on hotspot location Enables targeted advertising. eg- promotions for the

owner of the hotspot location, revenue sharing (charging models) etc…

Hotspot –Cafe

Hotspot –Train StationPortal - Free access

to timetables, fares..

Portal - Free sports news..

Access Controlle

rBRAS

Weblogin - Policy

Server


Location information – how? PPPoE model

• Easy – layer 2 circuit per hotspot to AC/BRAS• RADIUS will contain NAS Port ID etc…map back

centrally

DHCP model (rely on relay to provide)• Gateway address (GiAddr field)• Option 82 information, suboptions (ala RADIUS VSAs)• Or even layer 3 GRE tunnel back if access network

can’t provide info required (also simplifies routing)


Side topic – routing back to WiFi userin DHCP environment

Use location based info to allocate users from address pools; one pool per • Aggregate routes• Static, redistributed to IGP; simplified

Central pools ok but..• Require DHCP relay to store state - snoop address coming back from the server in DHCP offer / ACK• Also requires redistribution into IGP; scaling issues with that…


Secure access Why?

• Various access vulnerabilities in simple models

• Session hijacking / spoofing, man in the middle

Two main approaches:• IPSEC tunneling model• 802.1x/EAP


MPLS Backbone

WiFi secured accessIPSEC option

WiFi User with inbuilt IPSEC clientEg- Win2k, WinXP

Access Controller

BRAS

Any Backhaul Transport

RADIUS

LNS*

L2TP/IPSEC connection (RFC3193)

Terminate IPSECBRAS control of PPP session

Policy Server


IPSEC WiFi access Pros

• No external client software – inbuilt into Windows• PPP model gives full per user control (eg- terminate IPSEC and tunnel on L2TP)• Integrates well into a VPN environment; user sessions terminated to MPLS VPNs at AC/BRAS (PE)• Can use digital certificates to ensure identity (server and maybe clients also)

Cons:• Client issues – overhead, PDA support (eg- WinCE today only supports MSCHAPv2?)


IPSEC WiFi accessJapan Case Study

Integration of VPN access for mobile corporate users regardless of access type

Outsource remote access management from corporates, and aggregate users in a layer 3 VPN – common point of subscriber management

Network diagram:

Access Controller- BRAS (PE)

WiFi User with native Windows Client

IPSEC / L2TP (RFC 3193)

3G and 2G users

MPLS Backbone

LACGGSN

NativeL2TP

Users mapped into corporate VPNs

VRFs

PE

Corp HQ CE

GE VLAN


MPLS Backbone

WiFi secured access802.1/EAP option

WiFi User with EAP/802.1x client

eg- WinXP, iPass, Odyssey..

Access Controller

BRAS

Any Backhaul Transport

RADIUSEAPoL

802.1x

Policy Server

EAP/RADIUS

EAP

AP

Note- DHCP happens after EAP authentication


Option - Authentication using802.1X and EAP on 802.11 - overview

RADIUSServer

EAPOW-Start

EAP-Response/IdentityRadius-Access-Challenge

EAP-Response (credentials)

Access blockedAssociation

Radius-Access-Accept

EAP-Request/Identity

EAP-RequestRadius-Access-Request

Radius-Access-Request

RADIUS

EAPOW

802.11802.11 Associate-Request

EAP-Success

Access allowedEAPOW-Key (WEP..)

802.11 Associate-Response

Source: Microsoft


EAP/802.1x WiFi access Pros

• EAP/802.1x built into WinXP • Flexible authentication architecture – many different EAP

options eg- GSM SIM using EAP/SIM, EAP-MD5, LEAP, Smartcards etc…

• Can handle interAP roaming with 802.11f• Adopted in the corporate market

Cons:• Doesn’t address core network / VPN portion, just secures

access layer• Today uses session keys vs temporal (WPA, coming in 802.11i)• Need smarts to keep per user control in the network without

double logon


Maintaining subscriber control when using 802.1x/EAP environment“RADIUS relay” concept 802.1x access points have Radius client, EAP messages encapsulated in Radius messages Host MAC address in the calling-station-attribute Radius relay (BRAS) uses @domain name to forward Radius request to an external EAP capable Radius proxy or server BRAS relay stores Host MAC address (and maybe user) and awaits authorization data (VR to use, IP pool/address to use, filters, etc) DHCP request, based on the host MAC address, creates subscriber interface in proper context allocates IP address, assign default policies. Policy server control with no Web login Access point creates Radius authentication and accounting (stop)

RadiusRelay

DHCP

802.1x APAny Backhaul

Transport

Policy Server

RADIUS Server


Summary Which access model?

• PPPoE is nice, but often not practical• DHCP – web login models now can provide good per

user control, and location info etc Where am I? Location information

• Key for WiFi business models eg- generate content based on location (virtualised)

Security• IPSEC is a good end-end mechanism, integration

with VPNs• EAP is flexible and useful in access, but needs to tie

in with core network and per user control


Thank you…!

Contact: [email protected]


802.11 variants 802.11a 5.4MHz, OFDM, 54 Mbps, 10+ channels 802.11b 2.4GHz, DSSS, 11 Mbps, 3 channels 802.11d Enhancements to meet country specific regulations 802.11e Quality of Service 802.11f Inter-Access Point Protocol, handover between close APs 802.11g 2.4GHz, OFDM, 54Mbps, 3 channels 802.11h Specifically for 5GHz; power control and frequency

selection 802.11i Security framework, reference to 802.1x and EAP

See PowerPoint comments page below for more details


Wireless LAN Technologies802.11b 802.11a HiperLAN2

2.4 GHzPublic

5 GHz / Public / Private 5 GHz

Worldwide US/AP Europe

1-11 Mbps 20-54 Mbps (1-2 yrs) 100+ Mbps (future) 20-54 Mbps (1-2 yrs)

Freq.Band

Coverage

DataRate

802.11g

2.4 GHz Public

Worldwide

1-54 Mbps


PWLAN and Security WEP encryption (Wireless Equivalent Protocol) much

criticized in enterprise• Also it uses static keys which is not valid for PWLAN as

keys would need to be published 802.1x and EAP delivers improved security for PWLAN

• Introduces dynamic keys at start of session, and PWLAN sessions are short lived (unlike enterprise)

802.11i• Uses 802.1x which uses EAP and allows dynamic keys• Firmware upgrade for TKIP then hardware upgrade for

improved AES encryption• Poses transition complexity for existing user base

WPA (Wi-Fi Protected Access) is an interim step to 802.11i• Uses 802.1x and EAP and TKIP but no AES


802.1x Overview Make up for deficiencies in WEP which uses static keys IEEE 802.1x-2001: Port-Based Network Access Control

• Prior to authentication traffic is restricted to the authentication server RFC 2284 (1998): PPP Extensible Authentication Protocol (EAP)

• EAP encapsulated in Radius for transport to EAP enabled AAA server• Many variations EAP/TLS and EAP-PEAP supported by Microsoft, MD5,

OTP, LEAP (Cisco), and SIM (GSM Subscriber Identity Module) IEEE 802.11i Framework Specification

• Specifies use of 802.1x and EAP for authentication and encryption key

• New encryption in access point• Access Points need firmware upgrade to TKIP then new hardware for AES


PWLAN and Mobile 3GPP standards org defined five scenarios for PWLAN integration with 3G

• From common authentication to seamless handover of voice service• Specified 802.1x based authentication• Part of 3GPP Release 6, specified in TS 23.234

But, real deployments are occurring well in advance of 3GPP R6……so:

GSM Association WLAN Task Force issued guidelines for pre Release 6• Wed based login initially transitioning to 3GPP release 6 spec

A SIM located in WLAN cards will use authentication based on EAP/SIM• Eg- Use of SIM dongle

EAP to SS7 gateways will allow mobile HLR / HSSs to authenticate the WLAN card


Authenticating against the GSM HLR Existing database with all mobile subscriber information Existing provisioning and customer care systems are used EAP/SIM can offer GSM equivalent authentication and encryption Gateway between RADIUS/IP and MAP/SS7 is required

• Eg Funk Software Steel Belted Radius/SS7 Gateway• Ulticom Signalware SS7 software• Sun server E1/T1 interface card• An overview of the product is in this attachment:

• Major vendors Ericsson, Siemens, Nokia all have or are developing their own offer


802.1x EAP/SIM authentication from HLRTransparent RADIUS relay

BRAS AC, (RADIUS Relay)Authenticator

RADIUS/SS-7 GW HLR

EAPoL RADIUS

RADIUS Gr Interface

DHCP Discover

Client

DHCP Request

DHCP Offer

DHCP Ack {address = End User address from GGSN}

Client - Authentication

Client – IP Address Assignment

GW HLRMAPSS7


Tight integration proposed by 3GPP

GGSNAccess Controller,

RADIUS RelayAuthenticatorRADIUS/SS-7

GW HLR

EAPoL RADIUSRADIUS Gr Interface

Create PDP Context {IP, transparent mode APN, IMSI/NSAPI, MSISDN, dynamic address requested}

Create PDP Context Response {End User Address}

DHCP Discover

Client

DHCP Request

DHCP Offer

DHCP Ack {address = End User address from GGSN} Lease

expirationDelete PDP Context Request

Client - Authentication

Client – IP Address Assignment

GGSN

HLR

GPRS Tunneling Protocol


Real time handover… Many access types – WLAN, 3G, GPRS… Mobile IP could provide reasonable real-time macro roaming

between cellular and WLAN access types (also alternates such as 802.16/WiMax)

Supported for dual mode CPE/handsets• Eg- Dual Mode NEC cellphone with WLAN as trialed in DoCoMo• PDAs with WLAN and CDMA 1x/EVDO or GPRS/WCDMA• Notebooks with cellular data or dual mode cards

Off the shelf client software available today – IPUnplugged, Birdstep Challenges- VoIP, WLAN automated logon (eg- 802.1x could solve

this), applications/OS can handle address changes


Overview of Mobile IPv4 (RFC2002)

1. MN discovers Foreign Agent (FA) 2. MN obtains COA (FA - Care Of Address) 3. MN registers with FA which relays registration to HA 4. HA tunnels packets from CN to MN through FA 5. FA forwards packets from MN to CN or reverse tunnels through HA

(RFC3024)

HA FA

1. and 2. 3.MN

CN

5. 4.

Internet


Mobile IP Interworking with UMTS/GPRS

Recommends use of FA Care Of Addresses (CoA), not collocated, to conserve IPv4 addresses

Source:3GPP


Registration Process to GGSN FA

5. Activate PDPContext Accept

(no PDP address)

4. Create PDPContext Response(no PDP address)

2. Activate PDP Context Request

( APN=MIPv4FA )

IPv4 - Registration UMTS/GPRS + MIP , FA care-of address

TE MT HomeNetwork

SGSN GGSN/FA

3. Create PDPContext Request

( APN=MIPv4FA )

6. Agent Advertisement

7. MIP Registration Request

9. MIP Registration Reply10. MIP Registration Reply

1. AT Command (APN)

8. MIP Registration Request

A. Select suitable GGSN


Overview of Mobile IPv6Removes need for external FA in future 3GPP systems

1. MN obtains IP address using stateless or stateful autoconfiguration 2. MN registers with HA 3. HA tunnels packets from CN to MN 4. MN sends packets directly to CN or via tunnel to HA

• Binding Update from MN to CN removes HA from path.

HA

1. 2.MN

CN

4. 3.

Internet

wifi hotspot service control design & case study overview

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