RFC 3089 (rfc3089) - Page 2 of 12

A SOCKS-based IPv6/IPv4 Gateway Mechanism

RFC 3089        SOCKS-based IPv6/IPv4 Gateway Mechanism       April 2001


2. Basic SOCKS-based Gateway Mechanism

   Figure 1 shows the basic SOCKS-based gateway mechanism.

                  Client C       Gateway G     Destination D
               +-----------+     (Server)
               |Application|
           +-->+===========+  +-------------+  +-----------+
      same-+   |*SOCKS Lib*|  |  *Gateway*  |  |Application|
       API +-->+===========+  +=====---=====+  +-----------+
               | Socket DNS|  | Socket  DNS |  | Socket DNS|
               +-----------+  +-------------+  +-----------+
               | [ IPv X ] |  |[IPvX]|(IPvY)|  | ( IPv Y ) |
               +-----------+  +-------------+  +-----------+
               |Network I/F|  | Network I/F |  |Network I/F|
               +-----+-----+  +---+-----+---+  +-----+-----+
                     |            |     |            |
                     +============+     +------------+
                       socksified           normal
                       connection         connection
                      (ctrl)+data          data only

                Fig. 1 Basic SOCKS-based Gateway Mechanism

   In this figure, the Client C initiates the communication to the
   Destination D.  Two new functional blocks are introduced and they
   compose the mechanism.

   One, *Socks Lib*, is introduced into the client side (Client C) (this
   procedure is called "socksifying").  The *Socks Lib* is located
   between the application layer and the socket layer, and can replace
   applications' socket APIs and DNS name resolving APIs (e.g.,
   gethostbyname(), getaddrinfo() etc.).  There is a mapping table in it
   for a "DNS name resolving delegation" feature (described below).
   Each socksified application has its own *Socks Lib*.

   The other, *Gateway*, is installed on the IPv6 and IPv4 dual stack
   node (Gateway G).  It is an enhanced SOCKS server that enables any
   types of protocol combination relays between Client C (IPvX) and
   Destination D (IPvY).  When the *Socks Lib* invokes a relay, one
   corresponding *Gateway* process (thread) is spawned from the parent
   *Gateway* to take charge of the relay connection.

   The following four types of combinations of IPvX and IPvY are
   possible in the mechanism.






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