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IEEE 802.11r Suyang Ju

IEEE 802.11r Suyang Ju. Outline. Seamless Connectivity IEEE 802.11 Architecture IEEE 802.11i IEEE 802.11e IEEE 802.11r Security Features QoS Features Performance Proposals Summary Conclusion References. Seamless Connectivity. Motivation Customer interests

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IEEE 802.11r Suyang Ju

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  1. IEEE 802.11r Suyang Ju

  2. Outline Seamless Connectivity IEEE 802.11 Architecture IEEE 802.11i IEEE 802.11e IEEE 802.11r Security Features QoS Features Performance Proposals Summary Conclusion References

  3. Seamless Connectivity • Motivation • Customer interests • Multiple applications (voice, video and data) • Anywhere and Anytime • WLAN (coffee shop or airport) • WiMAX (Highway) • GSM cellular networks (phone calls) • GPRS • “Wi-Fi plus cellular” • Goals • Supporting multiple heterogeneous radios • Continuous and ubiquitous connectivity • Requirements • Homogenous handovers • Involve transition across points of attachment (PoA– such as WLAN AP or WiMAX BS) • Heterogeneous handovers • Involve transition across different networks such as WLAN, WiMAX and Cellular networks

  4. Seamless Connectivity Issues Homogeneous environment Intelligently recognize the immediate wireless environment Automatically select the best available PoA Qos resources should be allocated Security association should be computed Heterogeneous environment Much more complicated than homogeneous environment Possible solutions Homogeneous environment (Focus on WLAN) IEEE 802.11k Provides the information to discover the best available AP IEEE 802.11r Defines the mechanisms for secure and fast transitions between APs Heterogeneous environment IEEE 802.21 Defines a common media independent handover (MIH) function between layer 2 and layer 3 Provides mechanisms for optimizing handovers across Wi-Fi, WiMax and cellular networks

  5. Media Independent Handover Handover scenarios Scenario 1: Moving client Roams to a new AP with higher-receiving signal strength Scenario 2: Load balancing Increases the overall capacity of the wireless networks Scenario 3: Service availability Provides better QoS Signal quality issues include interference, noise and path loss Media independent handover (MIH) Provides link layer intelligence Supports handover for both mobile and stationary users Mobile users: Scenario1 Stationary users: Scenario 2 or 3 Supports multiple radio standards (multimode) or more than one interface simultaneously Supports transparent service continuity when handover occurs Offers a unified interface to the upper layers Independent of the technology-specific protocol provided by the lower layers

  6. Media Independent Handover Figure 1: IEEE 802.21 MIH functions in mobility management protocol stack From: Kapil Sood, Emily H. Qi and Vivek G. Gupta “Seamless Platform Mobility Across Wireless Networks”, 2005.

  7. Multi-radio Architecture Figure 2: Multi-radio architecture in Intel mobile platform From: Kapil Sood, Emily H. Qi and Vivek G. Gupta “Seamless Platform Mobility Across Wireless Networks”, 2005.

  8. IEEE 802.11 Architecture From: Pablo Brenner, “A Technical Tutorial on the IEEE 802.11 Protocol” BSS: Basic Service Set ESS: Extended Service Set AP: Access Point DS: Distributed System • Figure 3: IEEE 802.11 architecture

  9. IEEE 802.11 Architecture Based on Cellular architecture Subdivided into cells Each cell is controlled by a Base Station Base Station are connected through backbone The whole interconnected WLAN is called Extended Service Set (ESS) Portal A device interconnects between an 802.11 and another 802 LAN • Table 1: The name comparison between the IEEE 802.11 and cellular networks

  10. Roaming Definition Roaming is the process of moving from one BSS to another without loosing connection. Differences between the IEEE 802.11 and cellular networks Comparison #1 IEEE 802.11 Packet based Cellular networks Circuit based Effect: Roaming in IEEE 802.11 is easier Comparison #2 IEEE 802.11 Temporary disconnection significantly reduces the performance Cellular networks Temporary disconnection may not affect the conversation Effect: Roaming in IEEE 802.11 is more complicated

  11. IEEE 802.11 Extensions From: www.tropos.com “802.11 Technologies: Past, Present and Future”, 2007. • Goals: • Faster • Better performance • More secure • Broader applicability • Figure 4: 802.11 Extensions

  12. IEEE 802.11i Goal Designed to correct the weakness of the Wired Equivalency Protocol (WEP) Features Includes all the capabilities of WPA (Wi-Fi Protected Access) Defines a new encryption standard using AEC-CCMP Provides dynamic encryption-key techniques Pairwise master key caching Pre-authentication Layered security method Uses Remote Access Dial-In User Service (RADIUS) Port-based network access control mechanism Methods: EAP-TLS EAP-FAST EAP-SIM PEAP Drawback: Slow (Several hundred milliseconds)

  13. IEEE 802.11i From: Sangeetha Bangolae, Carol Bell and Emily Qi, “Performance Study of Fast BS Transition using IEEE 802.11r” Figure 5: Authentication and QoS exchange process during transition • Transition process: • Discovery (Probe exchange) • 802.11 open authentication • Re-association • Authentication method • EAPOL key exchange • QoS re-negotiation

  14. IEEE 802.11e Goal: Supports QoS in IEEE 802.11 MAC Implements access control mechanism to regulate the traffic Features: Introduces a new Hybrid Coordination Function (HCF) Combines function from DCF and PCF Hybrid coordinator (HC) at AP controls channel access Contention period Contention free period HC can gain control of the channel with higher priority Supports IntServ QoS Maximum duration that an STA can use is controlled Method Allocates TX opportunity (TXOP) to STA by polling Drawback Complex

  15. IEEE 802.11e Figure 6: A typical superframe in IEEE 802.11e • From: Stefan Mangold, Sunghyun Choi, Peter May, Ole Klein, Guido, Hiertz and Lothar Stibor, “IEEE 802.11e Wireless LAN fro Quality of Service”

  16. IEEE 802.11r: WLAN Fast Roaming Goal Minimize BSS transition time while providing the service offered by 802.11i and 802.11e Issues Provides both security and Qos features while fast roaming may be tricky “Security is easy. Mobility is hard” Method Performs the authentication processes before the station actually begins roaming Eliminates much of the handshaking overhead Advantages: Security: Robust authentication and encryption QoS: Fast roaming Authentication using 802.11i: several hundreds milliseconds Authentication using 802.11r: about 50ms Possible application of IEEE 802.11r Time-sensitive application: Vo-Fi

  17. IEEE 802.11r: Security Features New key-management hierarchy Multi-level setup Several security domain form a security mobility domain (SMD) Rules: The highest-level key holder has access to the original cryptographic material Higher-level entity derive the keys for the next level down Lower-level entity can not decipher the upper-level key Benefit: Securely cache and distribute encryption keys Eliminates the needs to perform a full 802.1X authentication with each AP Key-derivation algorithm Based on one-way hash function Purpose: Ensures lower-level key holder can not decipher the original master key

  18. IEEE 802.11r: Security Features Figure 7: IEEE 802.11r key hierarchy • MSK: Master session key • PSK: Pre-shared shared key • PMK: Pairwise master key • From: Sangeetha Bangolae, Carol Bell and Emily Qi, “Performance Study of Fast BS Transition using IEEE 802.11r”

  19. IEEE 802.11r: Security Features key-management hierarchy Highest-level key will be same within the same SMD SMD defines the boundary in which a station can perform fast hand-off Ideas Authentication occurs only once, when entering the mobility domain Subsequent cryptographic material derived from the initial authentication Procedures Initialization: Perform the key derivation for all layers in the key hierarchy All APs in this SMD need to know the corresponding level key Roaming: No IEEE 802.1X authentication is required Benefits: Decreases roam times Reduces load on back-end authentication servers

  20. IEEE 802.11r: Security Features From: Dava Molta, “802.11r: Wireless LAN Fast Roaming”, 2007 Figure 8: A comparison between IEEE 802.11i and IEEE 802.11r

  21. IEEE 802.11r: QoS Features Option #1 Method: Requests QoS resources at the time of re-association Time During re-association Benefit Avoids a separate message exchange to reserve the needed resource Drawback Takes a long time if the QoS server is slow Option #2 Method: Reserves QoS resources prior to committing to re-association Time Before re-association Benefit Faster if the QoS server is heavily loaded Avoids failed re-association attempts Drawback Might waste some resources

  22. IEEE 802.11r: Performance Figure 9: A comparison between the 802.11i and 802.11r • From: Sangeetha Bangolae, Carol Bell and Emily Qi, “Performance Study of Fast BS Transition using IEEE 802.11r”

  23. IEEE 802.11r: Performance Figure 10: IEEE 802.11r performance • From: Sangeetha Bangolae, Carol Bell and Emily Qi, “Performance Study of Fast BS Transition using IEEE 802.11r”

  24. IEEE 802.11r: Performance Table 2: A comparison between the 802.1X and 802.11r • From: Sangeetha Bangolae, Carol Bell and Emily Qi, “Performance Study of Fast BS Transition using IEEE 802.11r”

  25. IEEE 802.11r: Summary Proposals Fast BSS-Transition Tunnel TAP (Transition Acceleration Protocols) Fast Roaming Using Multiple Conhurrent Associations Motorola TGr Fast Handover Proposal PEKM (Post-EAP Key Management Protocol) Proposal for Fast Inter-BBS Transitions AP Scanning Just-In-Time 2 Phase Association ) The formal 802.11r standard is scheduled to be published in June 2008. From: www.wikipedia.com

  26. IEEE 802.11r: Other proposals Figure 11: Fast BSS-Transition Tunnel • From: Haixiang He and Darwin Engwer, “Fast BSS-Transition Tunnel”, 2004

  27. IEEE 802.11r: Other proposals Idea: STA is allowed to be associated with multiple AP simultaneously Problems Duplicated packets might be received by the STA The bandwidth might be wasted Practically, wired infrastructure in IEEE 802.11 might prevent multiple APs receive the same packets Method: Several APs need to maintain the information for the particular STA The information might need to be coherent Change APs might not be aware of roaming The information for the STA will not be deleted from its database Drawback More memory is needed in the AP

  28. IEEE 802.11r: Conclusion IEEE 802.11r is used to provide fast hand-off IEEE 802.11r considers both the security and QoS IEEE 802.11r reduces the transition time significantly

  29. References [1] Kapil Sood, Emily H. Qi and Vivek G. Gupta “Seamless Platform Mobility Across Wireless Networks”, 2005. [2] Pablo Brenner, “A Technical Tutorial on the IEEE 802.11 Protocol” [3] www.tropos.com “802.11 Technologies: Past, Present and Future”, 2007. [4] Sangeetha Bangolae, Carol Bell and Emily Qi, “Performance Study of Fast BS Transition using IEEE 802.11r” [5] Stefan Mangold, Sunghyun Choi, Peter May, Ole Klein, Guido, Hiertz and Lothar Stibor, “IEEE 802.11e Wireless LAN fro Quality of Service” [6] Dava Molta, “802.11r: Wireless LAN Fast Roaming”, 2007 [7] Haixiang He and Darwin Engwer, “Fast BSS-Transition Tunnel”, 2004 [8] www.wikipedia.com

  30. Thank you.Questions?

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