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Network Working Group                                          R. HindenRequest for Comments: 1955                        Ipsilon Networks, Inc.Category: Informational                                        June 1996New Scheme for Internet Routing and Addressing (ENCAPS) for IPNGStatus 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.Abstract   This document was submitted to the IETF IPng area in response toRFC1550.  Publication of this document does not imply acceptance by the   IPng area of any ideas expressed within.  Comments should be   submitted to the big-internet@munnari.oz.au 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.INTRODUCTION   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.CONTEXT   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   possible.   I propose this scheme as a new medium term solution.NEW SCHEME   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   better.   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 wouldHinden                       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.   The reason why I would chose to get more than one network number to   use to represent the AD address is I would use them to organize the   ADs.  Let's call them commonwealths.  Each commonwealth would only   have to know the detail of it's own ADs.   Next I would have the border routers inject these AD addresses into   the Intra-AD routing of transit ADs.  They would tell the routers   inside of the transit AD that they (the border routers) were the   route to each appropriate AD network.  Commonwealths that have   multiple interconnects (probably the common case) could by the use of   careful assignment of the AD addresses use subnetting to support   reasonable routing between the commonwealths.  This is where OSPF or   IS-IS might be better than BGP.  Also, IS-IS, with its ability to   route on actual end points might be the best.   The motivation behind injecting the AD addresses into the Intra-AD   routing of the transit ADs, is that the routers in these ADs can   forward the AD-Headers without knowing that they are special.  Only   the entrance and exit border routers are required to do anything   different.   Finally when a AD-Header is received at the last (exit) border router   it strips off the AD-Header and sends the datagram to the final   destination.   This scheme is based around the idea that IP addresses are globally   unique.  I think that we will not actually run out of IP addresses   for a long time and that we can live with the current addressing   until we can deploy a long term solution.   This scheme could be extended to not require globally unique IP   address.  Effectively the combination of AD-Address and IP-Address is   the globally unique address.  To use this scheme without globally   unique IP-Addresses and without changing in the hosts would require a   NAT mechanism in the border routers.  I think it would be preferable   to change the hosts to have them do the DNS query and add the AD-   header.  This could be the basis for the long term solution.   Another interesting aspect of this scheme is that if we were to relax   the current architecture where one IP-Address is always in only one   AD, to allow an IP-Address to be in more than one AD, it would   provide a solution to the issue of allowing a IP entity to getHinden                       Informational                      [Page 3]

RFC 1955                       IP Encaps                       June 1996   service from more than one service provider.SUMMARY OF CHANGES REQUIRED   The DNS needs to be extended to add an AD-Address entry for each   name.  These will be used by the entry and exit border routers to get   the AD-Addresses to use when building the AD-Headers.   Border routers need to be extended to do the DNS lookup, perform AD-   Header encapsulation, run an inter-AD routing algorithm using AD-   Addresses, and be able to AD-Header de-encapsulation.CONCLUSION   I believe that this scheme has may advantages.  These are:      - Only border routers and the DNS need change.  No changes are        required in hosts or non-border routers.      - No performance impact on datagram forwarding except at entry        and exit border routers.      - Only a small impact on bandwidth utilization on transit        networks due the addition of a 20 byte IP header to each        datagram.      - Removes the Inter-AD routing from Intra-AD routing and as a        result solves the routing load (table size and computation)        problem for the foreseeable future.      - The routing load on the border routers is manageable because        border routers only need to know the detail of the routing        commonwealth they are a member of.  Other commonwealths appear        as single addresses.      - No requirement for new routing protocols to be designed or        deployed.      - No translation of packets from one address scheme to another.      - Uses the current IP addressing structure.      - It scales well even if there is on the order of one AD per IP        network, because the AD-Addresses can be assigned logically.Hinden                       Informational                      [Page 4]

RFC 1955                       IP Encaps                       June 1996   It does have some disadvantages.  These are (at least):      - It is not a long term solution in its initial form.      - It assumes that the current IP-Addresses can remain globally        unique for a long time.REFERENCES   [ROAD] Gross, P., and P. Almquist, "IESG Deliberations on Routing          and Addressing",RFC 1380, ANS, Stanford University,          November 1992.SECURITY CONSIDERATIONS   Security issues are not discussed in this memo.AUTHOR'S ADDRESS   Robert M. Hinden   Ipsilon Networks, Inc.   2191 East Bayshore Road   Suite 100   Palo Alto, CA 94303   USA   EMail: hinden@ipsilon.com   Phone: +1 (415) 846-4604Hinden                       Informational                      [Page 5]