ATM网络中使用信元作为传输数据的基本单位，当信元从用户端进入网络中第一个交换机后，信元头中修改的部分是(19)。信元传输采用(20)。当进行VP交换时， VPI和VCI的变化情况是(21)。当需要传输压缩的视频流数据时，采用的服务类别最好是(22)。当AAL层采用AAL5协议传输数据时，可以达到的有效数据传输率(除去开销)为(23)。

(82)

(81)

(79)

(80)

(71) In the strength of the carrier signal is varied to represent binary 1 or 0.

  (72) is a system that can map a name to an address and conversely an address to an name.

  (73) is a three-way handshaking authentication protocol that it's packets are encapsulated in the point-to-point protocol

  (74) is an approach that enables an ATM Switch to behave like a LAN switch.

  (75) is an guided media which is made of glass or plastic and transmits signals in the form. of light.

(76)

(77)

(74)

(75)

(72)