rfc2823.txt

著名的RFC文档,其中有一些文档是已经翻译成中文的的.

RFC 2823                  PPP SDL on SONET/SDH                  May 2000


     }

     u32
     crc32(u32 crcval, u8 cval)
     {
         int i;

         crcval ^= cval << 24;
         for (i = 8; i--; )
             crcval = crcval & 0x80000000 ? (crcval << 1) ^ POLY32 :
                 crcval << 1;
         return crcval;
     }

     u16
     crc16_special(u8 *buffer, int len)
     {
         u16 crc;

         crc = 0;
         while (--len >= 0)
             crc = crc16(crc,*buffer++);
         return crc;
     }

     u16
     crc16_payload(u8 *buffer, int len)
     {
         u16 crc;

         crc = 0xFFFF;
         while (--len >= 0)
             crc = crc16(crc,*buffer++);
         return crc ^ 0xFFFF;
     }

     u32
     crc32_payload(u8 *buffer, int len)
     {
         u32 crc;

         crc = 0xFFFFFFFFul;
         while (--len >= 0)
             crc = crc32(crc,*buffer++);
         return crc ^ 0xFFFFFFFFul;
     }





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RFC 2823                  PPP SDL on SONET/SDH                  May 2000


     void
     make_sdl_header(int packet_length, u8 *buffer)
     {
         u16 crc;

         buffer[0] = (packet_length >> 8) & 0xFF;
         buffer[1] = packet_length & 0xFF;
         crc = crc16_special(buffer,2);
         buffer[0] ^= 0xB6;
         buffer[1] ^= 0xAB;
         buffer[2] = ((crc >> 8) & 0xFF) ^ 0x31;
         buffer[3] = (crc & 0xFF) ^ 0xE0;
     }

8.2.  Error Correction Tables

   To generate the error correction table, the following implementation
   may be used.  It creates a table called sdl_error_position, which is
   indexed on CRC residue value.  The tables can be used to determine if
   no error exists (table entry is equal to FE hex), one correctable
   error exists (table entry is zero-based index to errored bit with MSB
   of first octet being 0), or more than one error exists, and error is
   uncorrectable (table entry is FF hex).  To use for eight octet
   messages, the bit index from this table is used directly.  To use for
   four octet messages, the index is treated as an unrecoverable error
   if it is below 32, and as bit index plus 32 if it is above 32.

   The program also prints out the error syndrome table shown in section
   3.10.  This may be used as part of a "switch" statement in a hardware
   implementation.

       u8 sdl_error_position[65536];

       /* Calculate new CRC from old^(byte<<8) */
       u16
       crc16_t8(u16 crcval)
       {
           u16 f1,f2,f3;

           f1 = (crcval>>8) | (crcval<<8);
           f2 = (crcval>>12) | (crcval&0xF000) | ((crcval>>7)&0x01E0);
           f3 = ((crcval>>3) & 0x1FE0) ^ ((crcval<<4) & 0xF000);
           return f1^f2^f3;
       }







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RFC 2823                  PPP SDL on SONET/SDH                  May 2000


       void
       generate_error_table(u8 *bptab, int nbytes)
       {
           u16 crc;
           int i, j, k;

           /* Marker for no error */
           bptab[0] = 0xFE;

           /* Marker for >1 error */
           for (i = 1; i < 65536; i++ )
               bptab[i] = 0xFF;

           /* Mark all single bit error cases. */
           printf("Error syndrome table:\n");
           for (i = 0; i < nbytes; i++) {
               putchar(' ');

               for (j = 0; j < 8; j++) {
                   crc = 0;
                   for (k = 0; k < i; k++)
                         crc = crc16_t8(crc);
                   crc = crc16_t8(crc ^ (0x8000>>j));
                   for (k++; k < nbytes; k++)
                         crc = crc16_t8(crc);
                   bptab[crc] = (i * 8) + j;
                   printf(" %04X",crc);
               }
               putchar('\n');
           }
       }

       int
       main(int argc, char **argv)
       {
           u8 buffer[8] = {
               0x01,0x55,0x02,0xaa,
               0x99,0x72,0x18,0x56
           };
           u16 crc;
           int i;

           generate_error_table(sdl_error_position,8);

           /* Run sample message through check routine. */
           crc = 0;
           for (i = 0; i < 8; i++)
               crc = crc16_t8(crc ^ (buffer[i]<<8));



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RFC 2823                  PPP SDL on SONET/SDH                  May 2000


           /* Output is 0000 64 -- no error encountered. */
           printf("\nError test:  CRC %04X, bit position %d\n",
             crc,sdl_error_position[crc]);
       }

9.  Security Considerations

   The reliability of public SONET/SDH networks depends on well-behaved
   traffic that does not disrupt the synchronous data recovery
   mechanisms.  This document describes framing and scrambling options
   that are used to ensure the distribution of transmitted data such
   that SONET/SDH design assumptions are not likely to be violated.

10.  References

   [1]   Simpson, W., Editor, "The Point-to-Point Protocol (PPP)", STD
         51, RFC 1661, July 1994.

   [2]   Simpson, W., Editor, "PPP in HDLC-like Framing", STD 51, RFC
         1662, July 1994.

   [3]   Malis, A. and W. Simpson, "PPP over SONET/SDH", RFC 2615, June
         1999.

   [4]   "American National Standard for Telecommunications -
         Synchronous Optical Network (SONET) Payload Mappings," ANSI
         T1.105.02-1995.

   [5]   ITU-T Recommendation G.707, "Network Node Interface for the
         Synchronous Digital Hierarchy (SDH)," March 1996.

   [6]   Doshi, B., Dravida, S., Hernandez-Valencia, E., Matragi, W.,
         Qureshi, M.,  Anderson, J., Manchester, J.,"A Simple Data Link
         Protocol for High Speed Packet Networks", Bell Labs Technical
         Journal, pp. 85-104, Vol.4 No.1, January-March 1999.

   [7]   Demers, A., S. Keshav, and S. Shenker, "Analysis and simulation
         of a fair queueing algorithm," ACM SIGCOMM volume 19 number 4,
         pp. 1-12, September 1989.

   [8]   Floyd, S. and V. Jacobson, "Random Early Detection Gateways for
         Congestion Avoidance," IEEE/ACM Transactions on Networking,
         August 1993.

   [9]   Simpson, W., Editor, "PPP LCP Extensions", RFC 1570, January
         1994.





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RFC 2823                  PPP SDL on SONET/SDH                  May 2000


   [10]  ITU-T Recommendation I.432.1, "B-ISDN User-Network Interface -
         Physical Layer Specification: General Characteristics,"
         February 1999.

   [11]  ITU-T Recommendation V.41, "Code-independent error-control
         system," November 1989.

   [12]  ITU-T Recommendation G.783, "Characteristics of synchronous
         digital hierarchy (SDH) equipment functional blocks," April
         1997.

11.  Acknowledgments

   PPP over SONET was first proposed by Craig Partridge (BBN) and is
   documented by Andrew Malis and William Simpson as RFC 2615.

   Much of the material in this document was supplied by Lucent.

   Other length-prefixed forms of framing for PPP have gone before SDL,
   such as William Simpson's "PPP in Ether-like Framing" expired draft.

12.  Working Group and Chair Address

   The working group can be contacted via the mailing list (ietf-
   [e-mail]; send mail to [e-mail] to subscribe),
   or via the current chair:

   Karl Fox
   Extant, Inc.
   3496 Snouffer Road, Suite 100
   Columbus, Ohio 43235

   EMail:  [e-mail]

13.  Intellectual Property Notices

   The IETF takes no position regarding the validity or scope of any
   intellectual property or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
   might or might not be available; neither does it represent that it
   has made any effort to identify any such rights.  Information on the
   IETF's procedures with respect to rights in standards-track and
   standards-related documentation can be found in BCP-11.  Copies of
   claims of rights made available for publication and any assurances of
   licenses to be made available, or the result of an attempt made to





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RFC 2823                  PPP SDL on SONET/SDH                  May 2000


   obtain a general license or permission for the use of such
   proprietary rights by implementors or users of this specification can
   be obtained from the IETF Secretariat.

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights which may cover technology that may be required to practice
   this standard.  Please address the information to the IETF Executive
   Director.

14.  Authors' Addresses

   James Carlson
   Sun Microsystems, Inc.
   1 Network Drive MS UBUR02-212
   Burlington MA  01803-2757

   Phone:  [phone]
   Fax:    [phone]
   EMail:  [e-mail]


   Paul Langner
   Lucent Technologies Microelectronics Group
   555 Union Boulevard
   Allentown PA  18103-1286

   EMail:  [e-mail]


   Enrique J. Hernandez-Valencia
   Lucent Technologies
   101 Crawford Corners Rd.
   Holmdel NJ  07733-3030

   EMail:  [e-mail]


   James Manchester
   Lucent Technologies
   101 Crawford Corners Rd.
   Holmdel NJ  07733-3030

   EMail:  [e-mail]







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RFC 2823                  PPP SDL on SONET/SDH                  May 2000


15.  Full Copyright Statement

   Copyright (C) The Internet Society (2000).  All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph are
   included on all such copies and derivative works.  However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than
   English.

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assigns.

   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

   Funding for the RFC Editor function is currently provided by the
   Internet Society.



















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