New Scheme for Internet Routing and Addressing (ENCAPS) for IPNG
RFC 1955

Document Type RFC - Informational (June 1996; No errata)
Author Bob Hinden 
Last updated 2013-03-02
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Network Working Group                                          R. Hinden
Request for Comments: 1955                        Ipsilon Networks, Inc.
Category: Informational                                        June 1996

    New Scheme for Internet Routing and Addressing (ENCAPS) for IPNG

Status of This Memo

   This memo provides information for the Internet community.  This memo
   does not specify an Internet standard of any kind.  Distribution of
   this memo is unlimited.


   This document was submitted to the IETF IPng area in response to RFC
   1550.  Publication of this document does not imply acceptance by the
   IPng area of any ideas expressed within.  Comments should be
   submitted to the mailing list.

   This memo describes a proposal made to to the Routing and Addressing
   group [ROAD] January 1992 by Robert Hinden.  It was originally sent
   as an email message.  It proposes a medium term solution to the
   Internet's routing and addressing problems.


   I would like to propose a new scheme which I believe is a good medium
   term solution to the routing and address problems of the internet.
   It has the following positive attributes:

      - No Changes to Hosts
      - No Changes to Most Routers
      - No New Routing Protocols
      - No New Internet Protocols
      - No Translation of Addresses in Packets
      - Reduces the Routing Table Size in All Routers
      - Uses the Current Internet Address Structure

   It is not a solution good for all time, because it does impose some
   size limits and does not support new internet services such as
   guaranteed bandwidth, delay, etc.  It does require border routers to
   do additional processing, but does not require any packet
   translation.  I believe that this scheme will give us enough time to
   put into place a long term solution (i.e. pick one or more of CLNP,
   *NAT, IDPR, IDRP, Nimrod, Unified, NewIP, etc.)

Hinden                       Informational                      [Page 1]
RFC 1955                       IP Encaps                       June 1996

   This scheme is based on the ideas presented by Deborah Estrin (route
   on ADs), Martha Steenstrup (encapsulation), and probably steals from
   ideas put forward by Noel Chiappa, Van Jacobson , Ross Callon, Dave
   Oran, and everyone else in the ROAD group.


   I think that we (the ROAD group) agree that in the short term we need
   to make better use of the IP address space.  I think we also (mostly)
   agree that in the long term we need a solution that can deal with a
   very large number of end points and routes, as well as support new
   services such as guarantees of service, source selected routes, etc.
   We do not agree on any of the details of this but do agree that we
   can not figure out a long term solution before March.  We do agree
   that we should start working on a long term solution(s).

   What this leaves is the need for a good medium term solution which
   can keep the Internet going until we can design and deploy a long
   term solution.  The medium term solution wants to be the most "cost
   effective".  It should buy us the most time to develop a long term
   solution and do it with as little change to the existing Internet as

   I propose this scheme as a new medium term solution.


   The basic idea is that inter-domain routing be done by routing on
   autonomous domains (AD).  The key is how this is done.  The mechanism
   to do this is for the border routers to encapsulate the original IP
   datagrams with another IP header.  The source and destination
   addresses in the new header (I will call it the AD-Header from here
   on) represent the source and destination ADs.

   When the first (entrance) border router receives a datagram from a
   host or router without an AD-Header it looks at the source and
   destination address and does a DNS lookup to get the addresses for
   the AD-Header.  It then adds an AD-Header and forwards the
   encapsulated datagram to its proper destination AD.

   The border routers would compute AD routes by running a routing
   protocol between themselves.  BGP or even IS-IS or OSPF for that
   matter, would work fine.  As you will see later, they might even be

   The addresses I propose to use for the AD addresses are plain old IP
   addresses.  A small number of Class A and Class B addresses would be
   reserved for this purpose.  The network number of the address would

Hinden                       Informational                      [Page 2]
RFC 1955                       IP Encaps                       June 1996

   indicate that it was an AD identifier.  The local part of the address
   would indicate the actual AD.  This would allow for many ADs to be
   supported.  For example, 10 Class-A and 10 Class-B addresses could
   accommodate (10*2^24 + 10*2^16) 168,427,500 ADs.  We clearly don't
   need that many for a long time.
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