RFC 1683 (rfc1683) - Page 4 of 12

Multiprotocol Interoperability In IPng

RFC 1683         Multiprotocol Interoperability In IPng      August 1994


   It is likely that many future network systems will be configured to
   support multiple protocols including IPng.  As the IPng protocol is
   deployed, it is unreasonable to expect that users will be willing to
   give up any aspect of their current connectivity for the promise of a
   better future.  In reality, most IPng installations will be made "in
   addition to" the current protocols.  The resulting systems will
   resemble Figure 1 in that they will be able to communicate with
   systems supporting several different protocols.

   Unfortunately, in most current examples, the architecture of Figure 1
   is implemented as independent protocol stacks.  This means that even
   though both TCP and CLNP exist on the system, there is no way to use
   TCP and CLNP in the same communication.  The problem with current
   implementations of architectures like Figure 1 is that they are
   designed as co-existence architectures and are not integrated
   interoperability systems.  We believe future systems should include
   mechanisms to overcome this traditional limitation.  By integrating
   the components of multiple protocol stacks in a systematic way, we
   can interoperate with hosts supporting any of the individual stacks
   as well as those supporting various combinations of the stacks.

   In order to effectively use multiple protocols, a system must
   identify which of the available protocols to use for a given
   communication task.  We call this the Protocol Determination [2]
   task.  In performing this task, a system determines the combination
   of protocols necessary to provide the needed service.  For achieving
   interoperability, protocols are selected from the intersection of
   those supported on the systems that must communicate.

4.  Multiprotocol Techniques

   In this section we identify three main techniques to dealing with
   multiprotocol networks that are in use today and will continue to be
   used in the Internet.  The first two techniques, tunneling and
   conversion, are categorized as intermediate-system techniques in that
   they are designed to achieve multiprotocol support without changing
   the end-systems.  The third technique explicitly calls for the
   support of multiple protocols in end-systems.  By describing these
   techniques here, we can motivate the need for the specific protocol
   features described in Section 5.

4.1  Encapsulation/Tunneling

   Encapsulation or tunneling is commonly used when two networks that
   support a common protocol must be connected using a third
   intermediate network running a different protocol.  Protocol packets
   from the two end networks are carried as data within the protocol of
   the intermediate network.  This technique is only appropriate when



Clark, Ammar & Calvert