H3C Technologies H3C WX3000E Series Wireless Switches - Manual (Page 97)

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Configuring WLAN roaming
WLAN roaming overview
Inter AC Tunneling Protocol (IACTP) is a proprietary protocol of H3C which defines how access
controllers (ACs) communicate with each other. Based on the standard TCP client/server model, this
protocol generically encapsulates and transports communications securely between ACs.
You can use IACTP to create and maintain AC groups, termed mobility groups, which can include up to
8 ACs. IACTP provides a secure control tunnel for applications such as roaming that allow sharing and
exchanging messages. IACTP can be used with either IPv4 or with IPv6.
When a station first associates with an AC in a mobility group, that AC becomes the station's Home-AC
(HA). The connection request goes through 802.1X authentication followed by 11 Key exchange, and the
station information is then synchronized across the other ACs in the mobility group.
When the station roams to another AC in the mobility group (a Foreign-AC (FA)), the HA information is
used to fast-forward station authentication by skipping 802.1X authentication and performing only
802.11 key exchange. This method facilitates seamless roaming within a mobility group.
Terminology
• HA—The AC to which a wireless station is connected by associating with an AP for the first time is
the HA of the station.
• FA—An AC that is other than the HA and to which a station is currently connected is an FA of the
station.
• Fast-roam capable station—A wireless station that associates to an AC in the mobility-group and
supports fast roaming (only key caching is supported).
• Roam-out station—A wireless station that has associated with an AC other than the HA in the
mobility-group is a roam-out station at its HA.
• Roam-in station—A wireless station that has associated with an AC other than the HA in the
mobility-group is a roam-in station at the FA.
• Intra-AC roaming—A procedure where a wireless station roams from one AP to another AP, which
are connected to the same AC.
• Inter-AC roaming—A procedure where a wireless station roams from one AP to another AP, which
are connected to different ACs.
• Inter-AC fast roaming capability—If a station uses 802.1X (RSN) authentication through negotiation
and supports key caching, this station has inter-AC fast roaming capability.
WLAN roaming topologies
WLAN Roaming topologies consist of:
• Intra-AC roaming topology
• Inter-AC roaming topology
• Intra-FA roaming topology