1. doc.: IEEE 802.11-02/243r0 Submission March 2002 James Kempf, DoCoMo LabsSlide 1 802.11 and IP James Kempf Seamoby WG Co-chair DoCoMo Labs USA kempf@docomolabs-usa.com

2. doc.: IEEE 802.11-02/243r0 Submission March 2002 James Kempf, DoCoMo LabsSlide 2 Outline Assumed 802.11 network deployment. Reactive Layer 3 handover drawbacks. Proactive Layer 3 handover. Context transfer and handover. IETF Seamoby Working Group work items. Suggestions for 802.11/IETF further work.

3. doc.: IEEE 802.11-02/243r0 Submission March 2002 James Kempf, DoCoMo LabsSlide 3 802.11 Deployment Assumption 802.11 assumes a flat Layer 2 deployment. Valid for small networks (SOHO market).

4. doc.: IEEE 802.11-02/243r0 Submission March 2002 James Kempf, DoCoMo LabsSlide 4 Neglected Deployment Scenario Hierarchical network with routers between subnets Valid for large networks (enterprise/telco market).

5. doc.: IEEE 802.11-02/243r0 Submission March 2002 James Kempf, DoCoMo LabsSlide 5 Layer 3 Handover Triggered by a Reassociate between two 802.11 access points on two different IP subnets. Requires changing routing reachability so packets are routed to the mobile host on the new subnet. In Mobile IPv4, the Foreign Agent performs Layer 3 handover. –Typically implemented on the router. –Not implemented on access point. In Mobile IPv6, the router performs handover. –No Foreign Agent.

6. doc.: IEEE 802.11-02/243r0 Submission March 2002 James Kempf, DoCoMo LabsSlide 6 Handover Loss Analysis Handover between access points results in connectivity loss. Total connectivity loss at handover has two components: –Layer 2 loss due to handover between access points (802.11 Reassociate). –Layer 3 loss due to IAPP + IP handover between access routers (IP handover). Layer 3 handover requires Layer 2 handover. –Longer 802.11 Reassociate + IAPP means longer IP handover. Not every handover will be a Layer 3 handover, but many will. Time Layer 2 Connectivity Lost Layer 3 Connectivity Lost 802.11 Reassociate start 802.11 Reassociate end IP handover complete IAPP + IP Handover

7. doc.: IEEE 802.11-02/243r0 Submission March 2002 James Kempf, DoCoMo LabsSlide 7 Reactive Layer 3 Handover Process Old Access RouterNew Access Router 1) Reassociate 4) Get new subnet IP address 3) IAPP 2) Drop Packets

8. doc.: IEEE 802.11-02/243r0 Submission March 2002 James Kempf, DoCoMo LabsSlide 8 Application Tolerance for Loss For data applications, 100-300 ms or more is acceptable –Example: Web browsing For voice applications, 40 ms or less for total (Layer 2 + Layer 3) loss is necessary. –If not, the user will perceive an artifact. Current 802.11 product Layer 2 handover performance is in the range from 60 - 200 ms. –Informal measurements. For supporting VoIP, total 802.11 + IP handover times less than 40 ms are crucial! This includes security and IAPP transaction (if any). Reactive Layer 3 handover will not perform adequately for VoIP.

9. doc.: IEEE 802.11-02/243r0 Submission March 2002 James Kempf, DoCoMo LabsSlide 9 Proactive Layer 3 Handover Need Layer 2 handover sequencing information at Layer 3. –At the old access router prior to Layer 2 handover. –At the new access router as soon as the mobile host shows up. Integration of router and access point can achieve this. –Current products are bridges, not routers. Separation of router and access point is still desirable. –Access points only cover a limited geographical area. –Network operator may not want to tie subnet topology to geographical coverage area of one access point. –Still need a protocol between the access point and access router and 802 is as good as any. –Bridging is still a viable option.

10. doc.: IEEE 802.11-02/243r0 Submission March 2002 James Kempf, DoCoMo LabsSlide 10 Proactive Layer 3 Handover Process Old Access RouterNew Access Router 3) Flush MAC address to IP address mapping 4) Reassociate 5) Tunnel packets under old subnet address 2) IAPP 1) Link Down 6) Get new subnet IP address

11. doc.: IEEE 802.11-02/243r0 Submission March 2002 James Kempf, DoCoMo LabsSlide 11 Context Transfer and Proactive Handover Context transfer: sending context or state involving mobile host’s network access related services to new network point of attachment. –Example: QoS attributes. To be effective, context transfer must complete before IP handover. –Otherwise, the mobile host must wait to gain network access at new point of attachment. For that to happen, the router at the old point of attachment must know prior to Layer 2 handover where the host will be moving. –At the latest, the router must know when the old link is severed. One context transfer transaction for Layer 2 and Layer 3 context is desirable, to avoid delay.

12. doc.: IEEE 802.11-02/243r0 Submission March 2002 James Kempf, DoCoMo LabsSlide 12 IETF Seamoby Working Group Charter Context Transfer. –Problem statement and Requirements complete. –Next step: Designing a protocol. Candidate access router discovery: Translation of reachable access point MAC address to router IP address. –Covers inter-domain as well as intra-domain. –Problem statement complete. –Next step: Complete requirements. IP Paging –IP protocol for awakening a host out of low power mode when a message arrives –Includes ability to track host at IP level while in low power mode. –Layer 2 support important for efficient paging. Cellular systems include Layer 2 support. –Problem statement and Requirements complete. –Next step: Architecture framework definition.

13. doc.: IEEE 802.11-02/243r0 Submission March 2002 James Kempf, DoCoMo LabsSlide 13 Suggested 802.11 Proactive Handover Support Layer 2 signal between access point and router about progress of handover. –When a host leaves an access point – includes MAC address of host and new access point. –When a host arrives at an access point – includes MAC address of host and old access point Router does all off-subnet communication. –Access point MAC address to IP address translation. –IAPP communication with old access point for resource deallocation. –Context transfer. –Authentication and authorization of host. Router can background certain tasks, e.g. access point MAC address to IP address translation. A simple version of IAPP if there is no router. –One access point could act as the “master” and take on the router’s role.

14. doc.: IEEE 802.11-02/243r0 Submission March 2002 James Kempf, DoCoMo LabsSlide 14 Specific Changes to IAPP and 802.11 Extensible op codes for access point to router communication. Extensible context blobs for IETF use. Triggering IAPP on the old access point when the power level of the mobile host falls below a certain level and new access point is known.

15. doc.: IEEE 802.11-02/243r0 Submission March 2002 James Kempf, DoCoMo LabsSlide 15 Suggestions for Further Work Collaboration between 802.11 Tgf and IETF Seamoby WG to co-ordinate protocols. Support interaction between router and access point to increase performance and reliability of re- association. –Most common deployment scenario. Ensure that a simple, easy to configure option is available for flat, SOHO style deployments.

16. doc.: IEEE 802.11-02/243r0 Submission March 2002 James Kempf, DoCoMo LabsSlide 16 Feedback?