Important: The ASN Gateway is a licensed product and requires an Access Service Network Gateway support license.
Important: Both the anchor gateway session and non-anchor gateway sessions are counted towards the session license separately. Licensed session limits are enforced based on the total number of anchor and non-anchor sessions.
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•Important: Minimum hardware requirements consist of four processing cards (3 Active, 1 Standby). When session recovery is enabled, overall system capacity may be reduced, depending upon configuration.
Once a primary IP address is assigned dynamically to the WiMAX CPE, additional IP addresses are assigned dynamically to other IP hosts. Each of the IP hosts is identified by its unique 6-byte MAC address. The DHCP proxy on the ASN Gateway manages the IP addresses by mapping them to the unique MAC addresses supplied by the client in the chaddr option field in DHCP DISCOVER or REQUEST messages.The dynamic IP address allocation procedure for primary node and secondary hosts is described below:
• The primary IP address is the first IP address assigned to the WiMAX CPE. The DHCP DISCOVER and REQUEST messages for this must contain the WiMAX R6 MSID as the chaddr field. After this IP address is assigned, the session goes into Connected state and is ready to accept DHCP requests for additional IP addresses for other IP hosts.
• R3 Reference Point—Consists of the set of control plane protocols between the ASN and the CSN to support AAA, policy enforcement, and mobility management capabilities. It also encompasses the bearer plane methods (for example, tunneling) to transfer user data between the ASN and the CSN. R3 supports three types of clients: PMIPv4, CMIPv4, CMIPv6 (this is IPv4 and IPv6 support for Proxy Mobile IP (PMIP)) and Client Mobile IP (CMIP).
• R4 Reference Point—Consists of the set of control and bearer plane protocols originating and terminating in various functional entities of an ASN that coordinate MS mobility between ASNs and ASN Gateways. R4 is the only interoperable RP between similar or heterogeneous ASNs.
• R5 Reference Point—Consists of the set of control plane and bearer plane protocols for internetworking between the CSN operated by the home NSP and that operated by a visited NSP.
• R6 Reference Point—Consists of the set of control and bearer plane protocols for communication between the base station and the ASN Gateway. The bearer plane is an intra-ASN datapath between the base station and ASN gateway. The control plane includes protocols for datapath establishment, modification, and release control, in accordance with the MS mobility events. R6, in combination with R4, may serve as a conduit for exchange of MAC state information between base stations that cannot interoperate over R8.
• R7 Reference Point—Consists of an optional set of control plane protocols, for example, AAA and policy coordination in the ASN gateway as well as other protocols for coordination between the two groups of functions identified in R6. The decomposition of the ASN functions using the R7 protocols is optional.Important: To provide high throughput and high density call processing, the ASN Gateway integrates both the Decision Point and Enforcement Point functions. Therefore, the R7 reference point is not exposed.
• Passive Relay: In this type of message relay, when the ASN Gateway receives a message on an R4 or R6 interface, it retrieves the destination ID and forwards the same request message to the given destination.
• Active Relay: In this type of message relay, upon receiving the message on R4/R6 interface, the ASN Gateway creates a similar R4/R6 message on the basis of original message and relays it to the destination. For example, if during the inter-ASN Gateway handover a non-anchor ASN Gateway receives the data path registration request from the target base station, it creates a new data path registration request and sends it to the anchor ASN Gateway. After receiving the duplicate message, the anchor ASN Gateway sends the data path registration response to the non-anchor ASN Gateway. When it receives that message, the non-anchor ASN Gateway creates a new response message and sends the new data path registration response to the target base station.
• Profile-B: ASN Profile-B removes the ASN Gateway altogether and pushes all its functionality into the base station. This functionality includes the following:
• Profile-C: ASN Profile-C functionality is a subset of Profile-A with following functionality in Base Station:
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• Serving DP Function: The subscriber data is not processed in the non-anchor GW. It relays the subscriber data to anchor ASN Gateway over R4. When the inner IP packet emerges from R6 tunnel at the non-anchor ASN Gateway, the packet is sent over R4 data path tunnel to the Anchor ASN Gateway.
• Serving SFA Function: No packet classification is performed in this function. It provides only tunnel switching between R4 to R6 or vice versa.
• DHCP Proxy relay Function: DHCP messages are not processed in the non-anchor GW and relayed to the DHCP proxy in the anchor ASN Gateway over R4. When the inner IP packet emerges from the R6 tunnel at the non-anchor ASN Gateway, a check is made to see if DHCP proxy is co-located in the ASN Gateway. and whether to process DHCP packet locally or not. If the session is not anchored locally, that is, the DHCP proxy is not co-located, the non-anchor ASN Gateway sends the DHCP packet over an R4 data path tunnel to the anchor ASN Gateway.
• Relay Function: The non-anchor ASN Gateway provides relay functions to distribute received messages and subscriber information. The message relay is supported for following functions:
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To disable this default behavior use the policy ms-unexpected-network-reentry command in the ASN Gateway Service Configuration Mode. For more information regarding this command, refer to the Cisco Systems Command Line Interface Reference.
• Message Relay: The ASN Gateway provides the passive relay function for HO Request, HO Response, HO Ack, HO Confirm, and HO Complete messages in a stateless fashion. The gateway keeps the statistics of the different types of messages it has relayed. Retransmission of these messages is handled by the BS.
• Security Context Retrieval: The ASN Gateway supports the retrieval of the security context using Context Request and Context Report messages. This retrieval is also stateless. The context retrieval operation can be performed at any time during the lifetime of a call.
• Data Path Registration: After Pre-Registration, the target BS performs Data Path Registration. Data Path Registration is performed using a 3-way handshake. If Pre-Registration has occurred, the Data Path Registration messages do not contain any service flow information.
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