在SSCOP協(xié)議中：Signals between SSCOP and CPCS 一節(jié)中說明如下：
This Recommendation assumes the CPCS message mode of operation without the option “corrupted data delivery”. Use of Streaming Mode is for further study.

The SSCOP makes use of two signals between the SSCOP and CPCS: CPCS-UNITDATA.invoke an
CPCS-UNITDATA.signal. SSCOP PDUs submitted for transmission to the peer are placed in the Interface Data (ID) parameter of the CPCS-UNITDATA.invoke. Messages extracted from the Interface Data (ID) parameter of the CPCS-UNITDATA.signal are received SSCOP PDUs from the peer.

上面提到SSCOP PDUs 的傳輸，sscop和cpcs之間的信號，那么如何從atm傳輸的信元中找到sscop-pdu？既然aal5可以找出cpcs-pdu,那么再如何找到SSCOP-PDU呢？謝謝！