rfc1705.txt

著名的RFC文档,其中有一些文档是已经翻译成中文的的.

   Source TA:  64 Bits.
         The Source Transport Address.  The concatenation of the 24
         bit IEEE assigned Ethernet address and the 40 bit
         representation of the machines serial number for the local
         node.

   Destination Port Number:  28 Bits.
         Identifies the specific application on the remote node.

   Ver:  4 bits.

         This parameter the UDP version number in use within this
         packet.




Carlson & Ficarella                                            [Page 22]

RFC 1705     Six Virtual Inches to the Left: IPng Problems  October 1994


   Source Port Number:  28 Bits.
         Identifies the specific application on the local node.

   QoS:  4 bits.
         The Quality of Service parameter may be set by the user
         application and passed down to a network layer that
         supports different levels of service.

   Length:  16 bits
         The length parameter represents the length of the data area
         in octets.  This value will be set to zero if no data is
         sent within this packet.

   Checksum:  16 bits
         The checksum parameter has the same meaning as in the
         current version of UDP.  The current 96 bit pseudo header
         is NOT used in calculating the checksum.  The checksum
         covers only the information present in this header.  The
         checksum field itself is set to zero for the calculation.

   Data: Variable
         This is the area in which the data for the datagram will be
         sent.  The length of this data in octets is specified by
         the length parameter above.



























Carlson & Ficarella                                            [Page 23]

RFC 1705     Six Virtual Inches to the Left: IPng Problems  October 1994


Appendix D


          ______                         ______
         |      |                       |      |
         |  H1  |                       |  H2  |
         |      |                       |      |
         |______|                       |______|
              \                          /    \
               \                        /      \
            =========================  /        \
           "                         "/         |
           "       (SIPP)            "          |
           "                         "          |
           "========================="          |
                                                |
                                   ====================
                ______            "                    "
               |      |           "       CLNP         "
               |  H4  |           "                    "
               |      |           "===================="
               |______|                    |
                     \                     |
                      \                    |
             ===================        ___|___
            "                  "       |       |
            "                  "-------|  H3   |
            "     IPv4         "       |       |
            "                  "       |_______|
            "=================="


   Example 1: H1 Wishes to Establish Communication with H4 (Refer to the
   figure above.)

      1.  A user on host H1 attempts to communicate with a user
          on host H4 by referencing H4 s fully qualified domain name.

      2.  The TCP on H1 makes a DNS call to determine the TA
          address of H4.

      3.  The DNS call returns only the IPv4 address since H4 is
          determined to be an IPv4 only host.

      4.  The H1 TCP builds a transmission control block (TCB)
          setting the C-Bit (compatibility) "ON" since H4 is an IPv4
          host.  Included in the TCB will also be DA = IP-H4, SA =
          TA1, DP = 1234, SP = 5000 and any state parameters



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RFC 1705     Six Virtual Inches to the Left: IPng Problems  October 1994


          describing the connection (port numbers are for example
          purposes only).

      5.  The IP on H1 makes a DNS call to determine the network
          IP address of H4 and correspondingly caches both the TA
          address from the TCP as well as the network IP address for
          later use.

      6.  The packet is now routed using standard SIPP procedures
          to H2 this is the only path H1 has to H4.

      7.  H2 receives the packet from H1.  The TCP on H2 checks
          the destination TA of the packet and compares it to its
          own.  In this case it does not match, therefore the packet
          should be forwarded.

      8.  H2 s TCP will interrogate the supported network
          layer(s) and determines the packet must be forwarded to H3.

      9.  The TCP must now pass the packet the CLNP network
          layer.  The network layer checks its cache to determine if
          there is a route specified for DA = IP-H4 already in the
          cache.  If so the cache entry is used, if not an entry is
          created.  H2 then routes the packet to H3 via NA3a, which
          is the network layer address for IP-H4.

      10.  H3 receives the packet from H2. The TCP on H3 checks
           the destination TA of the packet and compares it to its
           own. Once again, it does not match.

      11.  H3, realizing that the destination address is an IPv4
           host, and knowing that it itself is directly connected to
           the IPv4 network constructs an IPv4 compatible header.  H3
           also constructs a TCB to manage the IPv4 connection.

      12.  The packet is sent down to be routed to the IP using
           standard IP routing procedures.

      13.  H4 receives the packet at which point the IP on it
           determines that the destination address is its own and thus
           proceeds to strip off the IP header and pass the packet up
           to the TCP layer.

      14.  The TCP layer than opens the corresponding IPV4_DP
           port (2311) which forms the first half of the connection to
           the application.





Carlson & Ficarella                                            [Page 25]

RFC 1705     Six Virtual Inches to the Left: IPng Problems  October 1994


      15.  H4 will now reply with a connection accept message,
           sending the packet back to H3.

      16.  H3 s TCP receives the packet and based on information
           in the TCB determines the packet should be delivered to H1.
           H3 uses the steps outlined above to route the packet back
           through the network structure.

   Example 2: H2 Wishes to Establish Communication with H3 (Refer to the
   figure above.)

      1.  A user on host H2 attempts to communicate with a user
          on host H3 by referencing H3 s fully qualified domain name.

      2.  The TCP on H2 makes a DNS call to determine the TA
          address of H3.

      3.  The DNS call returns the TA address for H3.

      4.  The H2 TCP builds a transmission control block (TCB)
          setting the C-Bit (compatibility) "OFF" since H3 is an IPng
          host.  Included in the TCB will also be DA = TA3, SA = TA2,
          DP = 1111, SP = 2222 and any state parameters describing
          the connection (port numbers are for example purposes
          only).

      5.  The IPng on H2 makes a DNS call to determine the
          network IPng address of H3 and correspondingly caches both
          the TA address from the TCP as well as the network IPng
          address for later use.

      6.  The packet is now routed to H3 over the IPng supported
          on that network.

      7.  H3 receives the packet from H2.  The TCP on H3 checks
          the destination TA of the packet and compares it to its
          own.  In this case it matches.

      8.  H3 s TCP will construct a TCB and respond with an open
          accept message.

      9.  H3 s TCP will interrogate the supported network
          layer(s) to determine the packet must be delivered to H2
          using NA2b which is specified in its cache.







Carlson & Ficarella                                            [Page 26]

RFC 1705     Six Virtual Inches to the Left: IPng Problems  October 1994


Security Considerations

   Security issues are not discussed in this memo.

Authors' Addresses

   Richard Carlson
   Argonne National Laboratory
   Electronics and Computing Technologies
   Argonne,  IL  60439

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


   Domenic Ficarella
   Motorola

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































Carlson & Ficarella                                            [Page 27]