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Generic Routing Encapsulation (GRE) (RFC1701)

IP.com Disclosure Number: IPCOM000002540D
Original Publication Date: 1994-Oct-01
Included in the Prior Art Database: 2019-Feb-12
Document File: 8 page(s) / 9K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

S. Hanks: AUTHOR [+3]

Related Documents

10.17487/RFC1701: DOI

Abstract

This document specifies a protocol for performing encapsulation of an arbitrary network layer protocol over another arbitrary network layer protocol. This memo provides information for the Internet community. This memo does not specify an Internet standard of any kind.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 28% of the total text.

Network Working Group S. Hanks Request for Comments: 1701 NetSmiths, Ltd. Category: Informational T. Li D. Farinacci P. Traina cisco Systems October 1994

Generic Routing Encapsulation (GRE)

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.

Abstract

This document specifies a protocol for performing encapsulation of an arbitrary network layer protocol over another arbitrary network layer protocol.

Introduction

A number of different proposals [RFC 1234, RFC 1226] currently exist for the encapsulation of one protocol over another protocol. Other types of encapsulations [RFC 1241, SDRP, RFC 1479] have been proposed for transporting IP over IP for policy purposes. This memo describes a protocol which is very similar to, but is more general than, the above proposals. In attempting to be more general, many protocol specific nuances have been ignored. The result is that this proposal is may be less suitable for a situation where a specific "X over Y" encapsulation has been described. It is the attempt of this protocol to provide a simple, general purpose mechanism which is reduces the problem of encapsulation from its current O(n^2) problem to a more manageable state. This proposal also attempts to provide a lightweight encapsulation for use in policy based routing. This memo explicitly does not address the issue of when a packet should be encapsulated. This memo acknowledges, but does not address problems with mutual encapsulation [RFC 1326].

In the most general case, a system has a packet that needs to be encapsulated and routed. We will call this the payload packet. The payload is first encapsulated in a GRE packet, which possibly also includes a route. The resulting GRE packet can then be encapsulated in some other protocol and then forwarded. We will call this outer

Hanks, Li, Farinacci & Traina [Page 1]

RFC 1701 Generic Routing Encapsulation (GRE) October 1994

protocol the delivery protocol. The algorithms for processing this packet are discussed later.

Overall packet

The entire encapsulated packet would then have the form:

--------------------------------- | | | Delivery Header | | | --------------------------------- | | | GRE Header | | | --------------------------------- | | | Payload packet | | | ---------------------------------

Packet header

The GRE packet header has the form:

0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |C|R|K|S|s|Recur| Flags | Ver | Protocol Type | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Checksum (optional) | Offset (optional) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Key (optional) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sequence Number (optional) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |...

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