Scheme for an internet encapsulation protocol: Version 1 (RFC1241)
Original Publication Date: 1991-Jul-01
Included in the Prior Art Database: 2001-Oct-24
Internet Society Requests For Comment (RFCs)
R.A. Woodburn: AUTHOR [+2]
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.
Network Working Group R. Woodburn
Request for Comments: 1241 SAIC
University of Delaware
A Scheme for an Internet Encapsulation Protocol:
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.
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.
The stripping of the Encapsulation Header and forwarding
of the Clear Datagram by the 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.
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 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
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.
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...