选择次链路能够维持会话存活性，却与上游网络提供者实施的准入过滤机制之间存在冲突。

Selecting the secondary links can keep session survivability, which conflicts with the ingress filtering of the upstream Internet Service Provider.

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如果找到的路由不是纯双向链路，则源节点还需要将RACK报文沿找到的回路路由循环一次，通过RACK的传播来通知中间节点建立起相应的路由。

If it is not a pure two-way path which includes some asymmetric links, the source needs to spread the RACK along the route and inform the route-related nodes to establish the corresponding route.

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TD - HSUPA是上行链路方向针对分组业务的优化和演进，它是继TD - SCDMA HSDPA后，TD - SCDMA标准的又一次重要的演进。

HSUPA is the optimization and evolution for packet service in uplink direction. It is another great evolution of TD-SCDMA standard after HSDPA.

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