The router must be able to move a stream of bits from one type of service, such as ISDN, to another, such as a T1, and change the data link encapsulation from PPP to Frame Relay.

• 路由器必须能够从一种服务型态；例如ISDN；移动位元流到另一种服务型态；例如T1；并且资料链结封装从PPP改变成讯框中继.