RSVP Operation Over IP Tunnels
RFC 2746

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Network Working Group                                          A. Terzis
Request for Comments: 2746                                          UCLA
Category: Standards Track                                    J. Krawczyk
                                               ArrowPoint Communications
                                                           J. Wroclawski
                                                                 MIT LCS
                                                                L. Zhang
                                                                    UCLA
                                                            January 2000

                     RSVP Operation Over IP Tunnels

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2000).  All Rights Reserved.

Abstract

   This document describes an approach for providing RSVP protocol
   services over IP tunnels. We briefly describe the problem, the
   characteristics of possible solutions, and the design goals of our
   approach. We then present the details of an implementation which
   meets our design goals.

1.  Introduction

   IP-in-IP "tunnels" have become a widespread mechanism to transport
   datagrams in the Internet. Typically, a tunnel is used to route
   packets through portions of the network which do not directly
   implement the desired service (e.g. IPv6), or to augment and modify
   the behavior of the deployed routing architecture (e.g. multicast
   routing, mobile IP, Virtual Private Net).

   Many IP-in-IP tunneling protocols exist today.  [IP4INIP4] details a
   method of tunneling using an additional IPv4 header.  [MINENC]
   describes a way to reduce the size of the "inner" IP header used in
   [IP4INIP4] when the original datagram is not fragmented.  The generic
   tunneling method in [IPV6GEN] can be used to tunnel either IPv4 or
   IPv6 packets within IPv6.  [RFC1933] describes how to tunnel IPv6

Terzis, et al.              Standards Track                     [Page 1]
RFC 2746             RSVP Operation Over IP Tunnels         January 2000

   datagrams through IPv4 networks.  [RFC1701] describes a generic
   routing encapsulation, while [RFC1702] applies this encapsulation to
   IPv4.  Finally, [ESP] describes a mechanism that can be used to
   tunnel an encrypted IP datagram.

   From the perspective of traditional best-effort IP packet delivery, a
   tunnel behaves as any other link. Packets enter one end of the
   tunnel, and are delivered to the other end unless resource overload
   or error causes them to be lost.

   The RSVP setup protocol [RFC2205] is one component of a framework
   designed to extend IP to support multiple, controlled classes of
   service over a wide variety of link-level technologies. To deploy
   this technology with maximum flexibility, it is desirable for tunnels
   to act as RSVP-controllable links within the network.

   A tunnel, and in fact any sort of link, may participate in an RSVP-
   aware network in one of three ways, depending on the capabilities of
   the equipment from which the tunnel is constructed and the desires of
   the operator.

      1. The (logical) link may not support resource reservation or QoS
         control at all. This is a best-effort link. We refer to this as
         a best-effort or type 1 tunnel in this note.
      2. The (logical) link may be able to promise that some overall
         level of resources is available to carry traffic, but not to
         allocate resources specifically to individual data flows.  A
         configured resource allocation over a tunnel is an example of
         this.  We refer to this case as a type 2 tunnel in this note.
      3. The (logical) link may be able to make reservations for
         individual end-to-end data flows.  We refer to this case as a
         type 3 tunnel. Note that the key feature that distinguishes
         type 3 tunnels from type 2 tunnels is that in the type 3 tunnel
         new tunnel reservations are created and torn down dynamically
         as end-to-end reservations come and go.

   Type 1 tunnels exist when at least one of the routers comprising the
   tunnel endpoints does not support the scheme we describe here. In
   this case, the tunnel acts as a best-effort link. Our goal is simply
   to make sure that RSVP messages traverse the link correctly, and the
   presence of the non-controlled link is detected, as required by the
   integrated services framework.

   When the two end points of the tunnel are capable of supporting RSVP
   over tunnels, we would like to have proper resources reserved along