Cisco Aironet Access Point Proxy Mobile IP
Layer 2 and Layer 3 Roaming Types
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L2 Roaming (IAPP)
L3 Roaming (Mobile IP)
© 2003, Cisco Systems, Inc. All rights re
Proxy Mobile IP
■ Layer 2 Roaming / IAPP: Network designers working with mobile users in a large area will often find it necessary to deploy more than one access point. The 802.11 standard does not define how access points track moving users or how to negotiate a handoff from one access point to the next, a process referred to as roaming. Several companies have introduced proprietary Inter-Access Point Protocols (IAPP) to support roaming. IAPP accomplishes roaming within a subnet; however, it does not address how the wireless system tracks users moving from one subnet to another when the same session must be maintained, as in the case of voice calls.
■ Layer 3 Roaming / Mobile IP: Where wireless is being deployed across multiple subnets, there are options to achieve seamless roaming. Wireless client adapters can contain proprietary client IP stacks that understand mobility and allow roaming between subnets.
— All mobile users on the network must have this software installed.
■ Layer 3 Roaming / Proxy Mobile IP: Another option is to have the wireless infrastructure contain the intelligence to perform the task. Cisco's Proxy Mobile IP delivers this functionality. Mobile IP is designed for use in even the most complex network environments. As the wireless station leaves one area and enters the next, the new access point informs the home agent of its new association and the home agent is responsible for maintaining a record of this association location.
Introduction to Proxy Mobile IP
Before Roam After Roam
Client is in the subnet of AP Client IP address does not change
All traffic directly connecting to client Since AP is in a different subnet all traffic must go through router for directions
© 2003, Cisco Systems, Inc. All rights reserved. AWLF v3.1—3-44
Before Roam After Roam
Client is in the subnet of AP Client IP address does not change
All traffic directly connecting to client Since AP is in a different subnet all traffic must go through router for directions
© 2003, Cisco Systems, Inc. All rights reserved. AWLF v3.1—3-44
Before Roaming
The laptop (1.1.1.39) and the access point (1.1.1.30) belong to the same subnet and all network traffic between the access point and the laptop is directed by the switch.
After Roaming
The laptop (1.1.1.39) and the access point (2.2.2.157) belong to different subnets and all network traffic between the access point and the laptop now requires assistance from the router. The router must have firmware on it that supports the Home Agent/Foreign Agent (HA/FA) function. The HA/FA function allows the router to create a tunnel between the two access points on different subnets and manage the whereabouts of roaming clients. So when the access point (1.1.1.30) has data to deliver to the laptop the data is sent through the tunnel to the access point (2.2.2.157) and the data is delivered to the laptop (1.1.1.39).
Proxy Mobile IP
Standard Mobile IP requires code for client
Proxy Mobile IP allows access point to do work for client
No special code needed for clients
Requires very little setup on access point (mostly on routers)
© 2003, Cisco Systems, Inc. All rights reserved. AWLF v3.1—3-45
Standard Mobile IP
Standard Mobile IP requires IT personnel to install Mobile IP client software on all clients. Proxy Mobile IP
Proxy Mobile IP does not require IT personnel to install client software on every client. However it does require firmware to be installed and configured on the Routers to support the Home Agent / Forwarding Agent function. The access points will also need to be configured to support Proxy Mobile IP. Addresses of wireless clients authorized for Mobile IP operation must be entered into Security Association table or access point must have a RADIUS server authorize Security Associations.
Continue reading here: Cisco Aironet Structured Wireless Aware Network SWAN
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