汇接接入层的用户流量，进行数据转发和交换

B、根据接入层的用户流量，进行流量均衡、安全控制等处理

C、提供用户访问Internet所需要的路由服务

D、根据处理结果把用户流量转发到核心交换层

-The user access layer tandem traffic, the data forwarding and exchange B, according to the access layer of the user traffic, the traffic balancing, security, control, handling C, offers users access to Internet routing services needed to D, according to the results the user forward traffic to the core switching layer