Aruba Networks, Inc. 7
Enabling High-Performance for Apple iPads in the Enterprise Aruba White Paper
We used applications, including Skype, YouTube, iTunes and iSIP voice over IP, that require constant, high-quality
network availability while moving around the building. This movement forced iPad to roam between APs about every
1 to 1.5 minutes. While on the move, we continuously monitored the quality of the application experience using
status indicators. We also took note of any disruptions or decline in the service quality. During our tests, no
applications experienced any decline in quality while roaming.
Aruba’s IP Mobility to Support Layer 3 Roaming for Apple Clients
To support Layer 3 roaming for iPad and other Apple clients, IP mobility must be enabled on the Aruba Mobility
Controller. Otherwise, an Apple client will not renew its IP address when moving from an AP on one subnet to an AP
on another subnet. Since the Apple client retains its original IP address, network connectivity will fail and will not
recover automatically.
Aruba Layer 3 IP mobility allows a client that is moving between AP subnets to retain its original IP address, which
addresses the connectivity issue. When IP mobility is congured, the client keeps the same IP address as it moves
between AP subnet A and subnet B. Without IP mobility enabled, the client must get a different IP as it travels from
AP subnet A to subnet B.
Table 3 shows the results of Aruba’s roaming tests with iPad.
Roaming
Layer 2: Intra-controller VLAN Mobility Pass
Layer 3: Inter-controller IP Mobility Pass
Table 3
Validate PMKID Should be Enabled for All Apple Clients
Opportunistic key caching (OKC), also called proactive key caching, can be used to restore latency and overhead in
the authentication process when roaming between APs. iPad, however, does not support OKC. Instead, Pairwise
Master Key ID (PMKID) is used to facilitate fast, secure roaming.
With validate PKMID enabled, the AP will check if the client supports OKC. If the client doesn’t support OKC (which
iPad does not), the AP will start the authentication process in the absence of the PMKID.
Maximizing the Battery Life of iPad
Users can increase the battery life of iPad and other dual-mode handsets by three to ve times by taking advantage
of several Aruba capabilities. Aruba supports a full network-side implementation of Wi-Fi Multimedia Power Save
(WMM Power Save), a Wi-Fi Alliance certication based on IEEE 802.11e Unscheduled Automatic Power Save
Delivery (U- APSD).
Aruba WLAN implements proxy ARP where the ARP request for a wireless client IP address is answered by the
Aruba infrastructure. This prevents the need for wireless clients, including Apple iPad, to “wake up” and process the
ARP request, hence conserving battery life. Multicast and broadcast ltering further helps clean the air from trafc
that requires processing by all wireless clients.
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