如何判斷調製解調器是否啟用了 PPP 壓縮？

我在嵌入式系統上使用 Debian Linux，我們ppp通過 CDMA 調製解調器連接到 WAN。我想知道ppp.

在我的/var/log/messages我看到這條線：

kernel: [   54.740000] PPP Deflate Compression module registered

但在/var/log/debug我看到這個：

pppd[2433]: Protocol-Reject for 'Compression Control Protocol' (0x80fd) received

的輸出pppstats -z是：

IN:  COMPRESSED  INCOMPRESSIBLE   COMP | OUT: COMPRESSED  INCOMPRESSIBLE   COMP
   BYTE   PACK     BYTE   PACK  RATIO |     BYTE   PACK     BYTE   PACK  RATIO
      0      0        0      0   0.00 |        0      0        0      0   0.00

那麼上述是否意味著啟用了壓縮？

您可以使用該命令pppstats -z顯示壓縮統計資訊。如果它顯示全零，則表示未啟用壓縮。

摘自手冊頁

  -z     Instead of the standard display, show statistics indicating the 
         performance of the packet compression algorithm in use.

  When the -z option is specified, instead displays the following fields,
  relating to the packet compression algorithm currently in use.   If
  packet compression is not in use, these fields will all display zeroes.  
  The fields displayed on the input side are:

  COMPRESSED BYTE
         The number of bytes of compressed packets received.

  COMPRESSED PACK
         The number of compressed packets received.

  INCOMPRESSIBLE BYTE
         The number of bytes of incompressible packets (that is, those 
         which were transmitted in uncompressed form) received.

  INCOMPRESSIBLE PACK
         The number of incompressible packets received.

  COMP RATIO
         The  recent  compression ratio for incoming packets, defined as 
         the uncompressed size divided by the compressed size (including 
         both compressible and incompressible packets).

  The fields displayed on the output side are:

  COMPRESSED BYTE
         The number of bytes of compressed packets transmitted.

  COMPRESSED PACK
         The number of compressed packets transmitted.

  INCOMPRESSIBLE BYTE
         The number of bytes of incompressible packets transmitted (that 
         is, those which were transmitted in uncompressed form).

  INCOMPRESSIBLE PACK
         The number of incompressible packets transmitted.

  COMP RATIO
         The recent compression ratio for outgoing packets.

引用自：https://unix.stackexchange.com/questions/117172