rfc1332.txt

改文件中包含了三个协议


RFC 1332                        PPP IPCP                        May 1992


3.2.  IP-Compression-Protocol

   Description

      This Configuration Option provides a way to negotiate the use of a
      specific compression protocol.  By default, compression is not
      enabled.

   A summary of the IP-Compression-Protocol Configuration Option format
   is shown below.  The fields are transmitted from left to right.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Type      |    Length     |     IP-Compression-Protocol   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Data ...
   +-+-+-+-+

   Type

      2

   Length

      >= 4

   IP-Compression-Protocol

      The IP-Compression-Protocol field is two octets and indicates the
      compression protocol desired.  Values for this field are always
      the same as the PPP Data Link Layer Protocol field values for that
      same compression protocol.

      The most up-to-date values of the IP-Compression-Protocol field
      are specified in the most recent "Assigned Numbers" RFC [6].
      Current values are assigned as follows:

         Value (in hex)          Protocol

         002d                    Van Jacobson Compressed TCP/IP

   Data

      The Data field is zero or more octets and contains additional data
      as determined by the particular compression protocol.





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RFC 1332                        PPP IPCP                        May 1992


   Default

      No compression protocol enabled.
















































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RFC 1332                        PPP IPCP                        May 1992


3.3.  IP-Address

   Description

      This Configuration Option provides a way to negotiate the IP
      address to be used on the local end of the link.  It allows the
      sender of the Configure-Request to state which IP-address is
      desired, or to request that the peer provide the information.  The
      peer can provide this information by NAKing the option, and
      returning a valid IP-address.

      If negotiation about the remote IP-address is required, and the
      peer did not provide the option in its Configure-Request, the
      option SHOULD be appended to a Configure-Nak.  The value of the
      IP-address given must be acceptable as the remote IP-address, or
      indicate a request that the peer provide the information.

      By default, no IP address is assigned.

   A summary of the IP-Address Configuration Option format is shown
   below.  The fields are transmitted from left to right.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Type      |    Length     |           IP-Address
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
           IP-Address (cont)       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type

      3

   Length

      6

   IP-Address

      The four octet IP-Address is the desired local address of the
      sender of a Configure-Request.  If all four octets are set to
      zero, it indicates a request that the peer provide the IP-Address
      information.

   Default

      No IP address is assigned.



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RFC 1332                        PPP IPCP                        May 1992


4.  Van Jacobson TCP/IP header compression

Van Jacobson TCP/IP header compression reduces the size of the TCP/IP
headers to as few as three bytes.  This can be a significant improvement
on slow serial lines, particularly for interactive traffic.

The IP-Compression-Protocol Configuration Option is used to indicate the
ability to receive compressed packets.  Each end of the link must
separately request this option if bi-directional compression is desired.

The PPP Protocol field is set to the following values when transmitting
IP packets:

   Value (in hex)

   0021      Type IP.  The IP protocol is not TCP, or the packet is a
             fragment, or cannot be compressed.

   002d      Compressed TCP.  The TCP/IP headers are replaced by the
             compressed header.

   002f      Uncompressed TCP.  The IP protocol field is replaced by
             the slot identifier.

4.1.  Configuration Option Format

   A summary of the IP-Compression-Protocol Configuration Option format
   to negotiate Van Jacobson TCP/IP header compression is shown below.
   The fields are transmitted from left to right.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Type      |    Length     |     IP-Compression-Protocol   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Max-Slot-Id  | Comp-Slot-Id  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type

      2

   Length

      6






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RFC 1332                        PPP IPCP                        May 1992


   IP-Compression-Protocol

      002d (hex) for Van Jacobson Compressed TCP/IP headers.

   Max-Slot-Id

      The Max-Slot-Id field is one octet and indicates the maximum slot
      identifier.  This is one less than the actual number of slots; the
      slot identifier has values from zero to Max-Slot-Id.

         Note: There may be implementations that have problems with only
         one slot (Max-Slot-Id = 0).  See the discussion in reference
         [3].  The example implementation in [3] will only work with 3
         through 254 slots.

   Comp-Slot-Id

      The Comp-Slot-Id field is one octet and indicates whether the slot
      identifier field may be compressed.

         0  The slot identifier must not be compressed.  All compressed
            TCP packets must set the C bit in every change mask, and
            must include the slot identifier.

         1  The slot identifer may be compressed.

      The slot identifier must not be compressed if there is no ability
      for the PPP link level to indicate an error in reception to the
      decompression module.  Synchronization after errors depends on
      receiving a packet with the slot identifier.  See the discussion
      in reference [3].




















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RFC 1332                        PPP IPCP                        May 1992


A.  IPCP Recommended Options

   The following Configurations Options are recommended:

      IP-Compression-Protocol -- with at least 4 slots, usually 16
      slots.

      IP-Address -- only on dial-up lines.


Security Considerations

   Security issues are not discussed in this memo.


References

   [1]   Simpson, W., "The Point-to-Point Protocol", RFC 1331, May 1992.

   [2]   Postel, J., "Internet Protocol", RFC 791, USC/Information
         Sciences Institute, September 1981.

   [3]   Jacobson, V., "Compressing TCP/IP Headers", RFC 1144, January
         1990.

   [4]   Postel, J., "The TCP Maximum Segment Size Option and Related
         Topics", RFC 879, USC/Information Sciences Institute, November
         1983.

   [5]   Mogul, J., and S. Deering, "Path MTU Discovery", RFC 1191,
         November 1990.

   [6]   Reynolds, J., and J. Postel, "Assigned Numbers", RFC 1060,
         USC/Information Sciences Institute, March 1990.

   [7]   Perkins, D., and R. Hobby, "Point-to-Point Protocol (PPP)
         initial configuration options", RFC 1172, August 1990.


Acknowledgments

   Some of the text in this document is taken from RFCs 1171 & 1172, by
   Drew Perkins of Carnegie Mellon University, and by Russ Hobby of the
   University of California at Davis.

   Information leading to the expanded IP-Compression option provided by
   Van Jacobson at SIGCOMM '90.




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RFC 1332                        PPP IPCP                        May 1992


   Bill Simpson helped with the document formatting.


Chair's Address

   The working group can be contacted via the current chair:

      Brian Lloyd
      Lloyd & Associates
      3420 Sudbury Road
      Cameron Park, California 95682

      Phone: [phone]

      EMail: [e-mail]



Author's Address

   Questions about this memo can also be directed to:

      Glenn McGregor
      Merit Network, Inc.
      1071 Beal Avenue
      Ann Arbor, MI 48109-2103

      Phone: [phone]

      EMail: [e-mail]





















McGregor                                                       [Page 12]