Internet DRAFT - draft-srinivas-intarea-gre-gach
draft-srinivas-intarea-gre-gach
Internet Area Working Group P. Srinivas, Ed.
Internet-Draft D. Frost, Ed.
Intended status: Standards Track Cisco Systems
Expires: March 30, 2012 September 27, 2011
GRE Generic Associated Channel
draft-srinivas-intarea-gre-gach-00.txt
Abstract
RFC 5586 defines a Generic Associated Channel (G-ACh) mechanism for
MPLS paths that enables multiplexing of auxiliary traffic over such
paths along with the user traffic they carry. Such auxiliary traffic
is commonly used for Operations, Administration, and Maintenance
protocols that enable monitoring and management of the path. This
document describes the applicability of the G-ACh mechanism to
Generic Routing Encapsulation (GRE) tunnels.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on March 30, 2012.
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Copyright (c) 2011 IETF Trust and the persons identified as the
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . . 3
2. G-ACh Packet Encapsulation over GRE . . . . . . . . . . . . . . 3
2.1. Structure of a GRE Encapsulated G-ACh Packet . . . . . . . 3
2.2. GRE Header . . . . . . . . . . . . . . . . . . . . . . . . 4
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
4. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
5. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.1. Normative References . . . . . . . . . . . . . . . . . . . 5
5.2. Informative References . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6
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1. Introduction
Generic Routing Encapsulation (GRE) [RFC2784] is a means of
encapsulating one network layer protocol over another. This practice
is commonly referred to as "tunneling". GRE deployments typically
take the form of one or more logical point-to-point or point-to-
multipoint tunnels.
As with other kinds of network links, a problem with logical tunnels
is how they are monitored and managed. In some cases no special
functionality is needed for this purpose beyond that provided by the
underlying network layer. In other cases, however, more robust
Operations, Administration, and Maintenance (OAM) functionality may
be required. For example, a tunnel may be carrying critical traffic
that is subject to a strict service level agreement, one that
requires the service provider to monitor the tunnel continuously for
connectivity faults and performance degradations.
A mechanism to facilitate such OAM functionality, the Generic
Associated Channel (G-ACh), has been defined for tunnels based on
Multiprotocol Label Switching (MPLS) in [RFC5586]. The G-ACh
provides an auxiliary "side-channel" associated with each tunnel that
can be used to carry a variety of OAM protocols over the tunnel so
that it can be monitored and managed. Examples of OAM protocols
defined for use over the G-ACh include Bidirectional Forwarding
Detection (BFD) [RFC5880] and protocols for precision measurement of
packet loss, delay, and throughput [RFC6374].
This document describes how the existing G-ACh mechanism can be used
for GRE tunnels. The scope of this document is limited to
description of the mechanism itself, and does not include discussions
on applicability of specific G-ACh protocols to GRE tunnels.
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
2. G-ACh Packet Encapsulation over GRE
2.1. Structure of a GRE Encapsulated G-ACh Packet
As shown in [RFC2784], a GRE packet has the following form, with the
outermost encapsulation layer shown at the top:
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+-------------------------------+
| Delivery Header |
+-------------------------------+
| GRE Header |
+-------------------------------+
| Payload Packet |
| |
+-------------------------------+
The Delivery Header is the header for the underlying network layer
over which the GRE packet is transported. It may be an IPv4 header
or an IPv6 header. The GRE Header [RFC2890] follows the Delivery
Header and identifies the format of the payload packet.
When the payload is a G-ACh message, the GRE packet has the following
form:
+------------------------------------+
| Delivery Header |
+------------------------------------+
| GRE Header |
+------------------------------------+
| Associated Channel Header (ACH) |
+------------------------------------+
| G-ACh Payload |
| |
+------------------------------------+
As specified in [RFC5586], the Associated Channel Header identifies
the format of the G-ACh payload that follows.
2.2. GRE Header
The presence of the Associated Channel Header (ACH) is indicated by
the Protocol Type field in the GRE header ([RFC2784] and [RFC2890]).
The value of the Protocol Type field is an EtherType as used for
next-layer protocol type identification in Ethernet frames. The
EtherType registry is maintained by the Institute of Electrical and
Electronics Engineers (IEEE) and also documented in the IANA
"Ethernet Numbers" registry. The IEEE has allocated an EtherType for
G-ACh packets as follows:
EtherType Meaning
----------- ---------------------------------------------------
(TBD) Generic Associated Channel (G-ACh) packet [RFC5586]
The format of the GRE header as documented in [RFC2890], when the
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payload is a G-ACh packet beginning with an Associated Channel
Header, is:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|C| |K|S| Reserved0 | Ver | Protocol Type = G-ACh |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Checksum (optional) | Reserved1 (Optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Key (optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number (Optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3. IANA Considerations
IANA is requested to verify that the IANA "Ethernet Numbers" registry
reflects the IEEE allocation for the G-ACh EtherType.
4. Security Considerations
This document indicates how a Generic Associated Channel protocol
packet can be carried inside a GRE packet. This encapsulation itself
poses no security risks beyond those already documented for GRE and
the G-ACh. When a G-ACh protocol is used for Operations,
Administration, and Maintenance of GRE tunnels, the security
considerations of that protocol also apply.
5. References
5.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P.
Traina, "Generic Routing Encapsulation (GRE)", RFC 2784,
March 2000.
[RFC2890] Dommety, G., "Key and Sequence Number Extensions to GRE",
RFC 2890, September 2000.
[RFC5586] Bocci, M., Vigoureux, M., and S. Bryant, "MPLS Generic
Associated Channel", RFC 5586, June 2009.
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5.2. Informative References
[RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
(BFD)", RFC 5880, June 2010.
[RFC6374] Frost, D. and S. Bryant, "Packet Loss and Delay
Measurement for MPLS Networks", RFC 6374, September 2011.
Authors' Addresses
Prashant Srinivas (editor)
Cisco Systems
1414 Massachusetts Ave
Boxborough, MA 01719
USA
Email: prasrini@cisco.com
Dan Frost (editor)
Cisco Systems
Email: danfrost@cisco.com
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