Browse Prior Art Database

Scheme for an internet encapsulation protocol: Version 1 (RFC1241) Disclosure Number: IPCOM000002057D
Original Publication Date: 1991-Jul-01
Included in the Prior Art Database: 2001-Oct-24
Document File: 18 page(s) / 41K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

R.A. Woodburn: AUTHOR [+1]


For several years researchers in the Internet community have needed a means of "tunneling" between networks. A tunnel is essentially a Source Route that circumvents conventional routing mechanisms. Tunnels provide the means to bypass routing failures, avoid broken gateways and routing domains, or establish deterministic paths for experimentation. (Download file contains alternative document formats.)

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 9% of the total text.

Network Working Group                                       R. Woodburn

Request for Comments: 1241                                         SAIC

                                                               D. Mills

                                                 University of Delaware

                                                              July 1991

            A Scheme for an Internet Encapsulation Protocol:

                               Version 1

1. Status of this Memo

   This memo defines an Experimental Protocol for the Internet

   community.  Discussion and suggestions for improvement are requested.

   Please refer to the current edition of the "IAB Official Protocol

   Standards" for the standardization state and status of this protocol.

   Distribution of this memo is unlimited.

2. Glossary

   Clear Datagram -

     The unmodified IP datagram in the User Space before


   Clear Header -

     The header portion of the Clear Datagram before

     Encapsulation.  This header includes the IP header and

     possibly part or all of the next layer protocol header,

     i.e., the TCP header.

   Decapsulation -

     The stripping of the Encapsulation Header and forwarding

     of the Clear Datagram by the Decapsulator.

   Decapsulator -

     The entity responsible for receiving an Encapsulated

     Datagram, decapsulating it, and delivering it to the

     destination User Space.  Delivery may be direct, or via

     Encapsulation.  A Decapsulator may be a host or a gateway.

   Encapsulated Datagram -

     The datagram consisting of a Clear Datagram prepended with

     an Encapsulation Header.

   Encapsulation -

     The process of mapping a Clear Datagram to the

     Encapsulation Space, prepending an Encapsulation Header to

     the Clear Datagram and routing the Encapsulated Datagram

Woodburn & Mills                                                [Page 1]

RFC 1241                 Internet Encapsulation                July 1991

     to a Decapsulator.

   Encapsulation Header -

     The header for the Encapsulation Protocol prepended to the

     Clear Datagram during Encapsulation.  This header consists

     of an IP header followed by an Encapsulation Protocol


   Encapsulation Protocol Header -

     The Encapsulation Protocol specific portion of the

     Encapsulation Header.

   Encapsulation Space -

     The address and routing space within which the

     Encapsulators and Decapsulators reside.  Routing within

     this space is accomplished via Flows.  Encapsulation

     Spaces do not overlap, that is, the address of any

     Encapsulator or Decapsulator is unique for all

     Encapsulation Spaces.

   Encapsulator -

     The entity responsible for mapping a given User Space

     datagram to the Encapsulation Space, encapsulating the

     datagram, and forwarding the Encapsulated Datagram to a

     Decapsulator.  An Encapsulator may be a host or a gateway.

   Flow -

     Also called a "tunnel."  A flow is the end-to-end path in

     the Encapsulation Space over which Encapsulated Datagrams

     travel.  There may be several Encapsulator/Decapsulator

     pairs along a given flow.  Note that a Flow does not

     denote what User Space gateways are traversed along the


   Flow ID -

     A 32-bit identifier which uniquely distinguishes a flow in

     a given Encapsulator or Decapsulator.  Flow IDs are

     specific to a single Encapsulator/Decapsulator Entity and

     are not global quantities.

   Mapping Function -

     This is the function of mapping a Clear Header to a

     particular Flow.  All encapsulators along a given Flow are

     required to map a gi...