开发过CDC类设备的看过来

在http://www.devusb.com/bbs这个论坛上看到有人发帖说开发完成了CDC类（Communication Device Class）设备，并帖除了描述符。
现在我想了解一下做CDC类设备的东东，哪位有经验能帮我回答一下几个问题：
1、这这个描述符中，作者使用了一个中断传输端点和两个批量传输端点，但是描述符中间有这么一段
   Unknown Descriptor
      bDescriptorType 0x24
      bLength 0x04
      04 24 04 06
   请问这个东东怎么解释？我在另外一个CDC类设备中也看到了这一段类似的东东。
2、开发CDC设备是否要自己写驱动程序？同其他类设备最大的区别是什么？


Device Descriptor:
bcdUSB: 0x0110
bDeviceClass: 0x02
bDeviceSubClass: 0x00
bDeviceProtocol: 0x00
bMaxPacketSize0: 0x20 (32)
idVendor: REPLACE WITH YOUR VID
idProduct: REPLACE WITH YOUR PID
bcdDevice: 0x0000
iManufacturer: 0x01
0x0409: "HHP"
iProduct: 0x02
0x0409: "IT4600"
iSerialNumber: 0x08
0x0409: "XXXXXX"
bNumConfigurations: 0x01

ConnectionStatus: DeviceConnected
Current Config Value: 0x01
Device Bus Speed: Full
Device Address: 0x03
Open Pipes: 3

Endpoint Descriptor:
bEndpointAddress: 0x83
Transfer Type: Interrupt
wMaxPacketSize: 0x0020 (32)
bInterval: 0x02

Endpoint Descriptor:
bEndpointAddress: 0x81
Transfer Type: Bulk
wMaxPacketSize: 0x0040 (64)
bInterval: 0x00

Endpoint Descriptor:
bEndpointAddress: 0x02
Transfer Type: Bulk
wMaxPacketSize: 0x0040 (64)
bInterval: 0x00

Configuration Descriptor:
wTotalLength: 0x003E
bNumInterfaces: 0x02
bConfigurationValue: 0x01
iConfiguration: 0x03
0x0409: "Default"
bmAttributes: 0xA0 (Bus Powered Remote Wakeup)
MaxPower: 0xBB (374 Ma)

Interface Descriptor:
bInterfaceNumber: 0x00
bAlternateSetting: 0x00
bNumEndpoints: 0x01
bInterfaceClass: 0x02
bInterfaceSubClass: 0x02
bInterfaceProtocol: 0x01
iInterface: 0x04
0x0409: "CDC-ACM Comm"

Unknown Descriptor:
bDescriptorType: 0x24
bLength: 0x05
05 24 00 10 01

Unknown Descriptor:
bDescriptorType: 0x24
bLength: 0x05
05 24 01 03 01

Unknown Descriptor:
bDescriptorType: 0x24
bLength: 0x04
04 24 02 06

Endpoint Descriptor:
bEndpointAddress: 0x83
Transfer Type: Interrupt
wMaxPacketSize: 0x0020 (32)
bInterval: 0x02

Interface Descriptor:
bInterfaceNumber: 0x01
bAlternateSetting: 0x00
bNumEndpoints: 0x02
bInterfaceClass: 0x0A
bInterfaceSubClass: 0x00
bInterfaceProtocol: 0x00
iInterface: 0x05
0x0409: "CDC-ACM Data"

Endpoint Descriptor:
bEndpointAddress: 0x81
Transfer Type: Bulk
wMaxPacketSize: 0x0040 (64)
bInterval: 0x00

Endpoint Descriptor:
bEndpointAddress: 0x02
Transfer Type: Bulk
wMaxPacketSize: 0x0040 (64)
bInterval: 0x00

顶到有人看到为止！

很少有人做CDC类设备吗？怎么看的人这么少啊？