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    User-Session Routing Overview

    The MobileNext Broadband Gateway supports user-session routing to dynamically redirect create session requests received on the broadband gateway to another mobile network gateway, when appropriate. You configure a service-selection profile on the broadband gateway to define the conditions that trigger a redirect action to reroute user sessions. The Broadband Gateway supports user-session routing for GTP v0, GTPv1, and GTPv2.

    User-session routing is enabled on the broadband gateway when the configured service selection profile for the APN includes the redirect-peer ip-address then method. When a create session request arriving on the broadband gateway triggers a redirect (the create session request indicates a match with one of the from conditions configured in service-selection profile), the broadband gateway off loads the create session request to another gateway on the mobile network that has the capability to service the create session request.

    A broadband gateway might route a create session request to a more appropriate gateway to anchor create session requests in the following cases:

    • A configured policy, session load, or system status (for example, maintenance mode) on the receiving broadband gateway adversely impacts the ability of the broadband gateway to service the create session request.
    • A configuration on the broadband gateway prevents the gateway from meeting service, billing, or other requirements for the create session request.

    Note: After a create session request is off loaded from the broadband gateway to another gateway (the broadband gateway receives a create session response), the broadband gateway has no further responsibility for the off-loaded subscriber session, and any subsequent data traffic or session modifications are handled by the new gateway.

    The following sequence describes the call flow for user session routing:

    1. The SGW sends a create session request (source IP SGW, destination IP PGW1, source port SGW1, destination port 2123)
    2. PGW1 decides to redirect the request to PGW2
    3. PGW1 sends the create session request to PGW2 (source IP PGW1, destination IP PGW2, source port PGW1, destination port 2123)
    4. PGW2 sends a create session response to PGW1 (source IP PGW2, source port 2123, Destination IP PGW1, destination port PGW1)
    5. PGW1 replies to SGW (source IP PGW1, source port 2123, destination IP SGW, destination port SGW)

    In the preceding call flow sequence, PGW1 applies a service selection profile to a Create Session Request (at Step 2) to redirect the Create Session Request message to PGW2. PGW1 operates as a proxy for the SGW (at Step 3) by inserting its network address as an SGW network address within the Create Session Request. With PGW1 acting as a proxy, PGW2 can operate as if communicating with the SGW (at Step 4) according to conventional methods without having to support new functionality. Upon receiving a successful response from PGW2, PGW1 (at Step 5) sends a Create Session Response message to the SGW, directing the SGW to use PGW2 for future communications. As a result, any data and control traffic will travel directly between the SGW and PGW2 without any interaction from PGW1.

    Published: 2011-11-22