MPLS D. Frost, Ed.
Internet-Draft S. Bryant, Ed.
Intended status: Standards Track Cisco Systems
Expires: April 23, 2012 M. Bocci, Ed.
Alcatel-Lucent
October 21, 2011
MPLS-TP Next-Hop Ethernet Addressing
draft-fbb-mpls-tp-ethernet-addressing-00
Abstract
The Multiprotocol Label Switching (MPLS) Transport Profile (MPLS-TP)
is the set of MPLS protocol functions applicable to the construction
and operation of packet-switched transport networks. This document
presents considerations for link-layer addressing of Ethernet frames
carrying MPLS-TP packets.
This document is a product of a joint Internet Engineering Task Force
(IETF) / International Telecommunication Union Telecommunication
Standardization Sector (ITU-T) effort to include an MPLS Transport
Profile within the IETF MPLS and PWE3 architectures to support the
capabilities and functionalities of a packet transport network.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 23, 2012.
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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1. Introduction
The MPLS Transport Profile (MPLS-TP) [RFC5921] is the set of protocol
functions that meet the requirements [RFC5654] for the application of
MPLS to the construction and operation of packet-switched transport
networks. The MPLS-TP data plane consists of those MPLS-TP functions
concerned with the encapsulation and forwarding of MPLS-TP packets
and is described in [RFC5960].
This document presents considerations for link-layer addressing of
Ethernet frames carrying MPLS-TP packets. Since MPLS-TP packets are
MPLS packets, existing procedures ([RFC3032], [RFC5332]) for the
encapsulation of MPLS packets over Ethernet apply. Because IP
functionality is optional in an MPLS-TP network, however, IP-based
protocols for Media Access Control (MAC) address learning, such as
the Address Resolution Protocol (ARP) [RFC0826] and IP version 6
Neighbor Discovery [RFC4861], may not be available. This document
specifies the options for determination and selection of next-hop
Ethernet MAC addressing under these circumstances.
This document is a product of a joint Internet Engineering Task Force
(IETF) / International Telecommunication Union Telecommunication
Standardization Sector (ITU-T) effort to include an MPLS Transport
Profile within the IETF MPLS and PWE3 architectures to support the
capabilities and functionalities of a packet transport network.
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1.1. Terminology
Term Definition
------- -------------------------------------------
ARP Address Resolution Protocol
G-ACh Generic Associated Channel
GAL G-ACh Label
LSP Label Switched Path
LSR Label Switching Router
MAC Media Access Control
MPLS-TP MPLS Transport Profile
OAM Operations, Administration, and Maintenance
Additional definitions and terminology can be found in [RFC5960] and
[RFC5654].
1.2. 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. Point-to-Point Link Addressing
When two MPLS-TP nodes are connected by a point-to-point Ethernet
link, the question arises as to what destination Ethernet Media
Access Control (MAC) address should be specified in Ethernet frames
transmitted to the peer node over the link. The problem of
determining this address does not arise in IP/MPLS networks because
of the presence of the Ethernet Address Resolution Protocol (ARP)
[RFC0826] or IP version 6 Neighbor Discovery protocol [RFC4861],
which allow the unicast MAC address of the peer device to be learned
dynamically.
If existing mechanisms are available in an MPLS-TP network to
determine the destination unicast MAC addresses of peer nodes -- for
example, if the network also happens to be an IP/MPLS network -- such
mechanisms SHOULD be used. The remainder of this section discusses
the available options when this is not the case.
Each node MAY be statically configured with the MAC address of its
peer. Note however that static MAC address configuration can present
an administrative burden and lead to operational problems. For
example, replacement of an Ethernet interface to resolve a hardware
fault when this approach is used requires that the peer node be
manually reconfigured with the new MAC address. This is especially
problematic if the peer is operated by another provider.
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The Ethernet broadcast address FF-FF-FF-FF-FF-FF MAY be used as the
destination MAC address in frames carrying MPLS-TP packets over a
link that is known to be point-to-point. This may, however, lead to
excessive frame distribution and processing at the Ethernet layer.
Broadcast traffic may also be treated specially by some devices and
this may not be desirable for MPLS-TP data frames.
The approach which SHOULD be used, in view of these considerations,
is therefore to use as the destination MAC address an Ethernet
multicast address reserved for MPLS-TP for use over point-to-point
links. The address allocated for this purpose by the Internet
Assigned Numbers Authority (IANA) is 01-00-5E-XX-XX-XX. An MPLS-TP
implementation MUST process Ethernet frames received over a point-to-
point link with this destination MAC address by default.
The use of broadcast or multicast addressing is applicable only when
the attached Ethernet link is known to be point-to-point. If a link
is not known to be point-to-point, these forms of addressing MUST NOT
be used.
3. Multipoint Link Addressing
When a multipoint Ethernet link serves as a section [RFC5960] for a
point-to-multipoint MPLS-TP LSP, and multicast destination MAC
addressing at the Ethernet layer is used for the LSP, the addressing
and encapsulation procedures specified in [RFC5332] SHALL be used.
When a multipoint Ethernet link -- that is, a link which is not known
to be point-to-point -- serves as a section for a point-to-point
MPLS-TP LSP, unicast destination MAC addresses MUST be used for
Ethernet frames carrying packets of the LSP. According to the
discussion in the previous section, this implies the use of either
static MAC address configuration or a protocol that enables peer MAC
address discovery.
4. MAC Address Determination via the G-ACh Advertisement Protocol
The G-ACh Advertisement Protocol (GAP) [I-D.fbb-mpls-gach-adv]
provides a simple means of informing listeners on a link of the
sender's capabilities and configuration. When used for this purpose
on an Ethernet link, GAP messages are multicast to the address 01-00-
5e-80-00-0d. If these messages contain the unicast MAC address of
the sender, then listeners can learn this address and use it in the
future when transmitting frames containing MPLS-TP packets. Since
the GAP does not rely on IP, this provides a means of unicast MAC
discovery for MPLS-TP nodes without IP support.
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This document defines a new GAP application, "Ethernet Interface
Parameters", to support the advertisement of Ethernet-specific
parameters associated with the sending interface. It defines several
Type-Length-Value (TLV) objects for this application, as follows:
Unicast MAC Address: The Value of this object is a canonical 48-
bit Ethernet unicast MAC address assigned to one of the interfaces
of the sender that is connected to this data link.
Maximum Frame Size: The Value of this object is 32-bit unsigned
integer encoded in network byte order that specifies the maximum
frame size supported by the sending interface, in octets.
[Editor's note: Other objects may be added here.]
5. Security Considerations
The use of broadcast or multicast Ethernet destination MAC addresses
for frames carrying MPLS-TP data packets can potentially result in
such frames being distributed to devices other than the intended
destination node or nodes when the Ethernet link is not point-to-
point. The operator SHOULD take care to ensure that MPLS-TP nodes
are aware of the Ethernet link type (point-to-point or multipoint).
In the case of multipoint links, the operator SHOULD either ensure
that no devices are attached to the link that are not authorized to
receive the frames, or take steps to mitigate the possibility of
excessive frame distribution, for example by configuring the Ethernet
switch to appropriately restrict the delivery of multicast frames to
authorized ports.
6. IANA Considerations
6.1. Ethernet Multicast Address Allocation
IANA is requested to allocate an Ethernet Multicast Address from the
Ethernet Multicast Addresses table in the ethernet-numbers registry
for use by MPLS-TP LSRs over point-to-point links as described in
Section 2. The entry should specify an address of the form 01-00-5E-
XX-XX-XX, a Type Field of 8847/8848, and a usage "MPLS-TP point-to-
point (this draft)".
6.2. G-ACh Advertisement Protocol Allocation
IANA is requested to allocate a new Application ID in the "G-ACh
Advertisement Protocol Applications and Data Types" registry, along
with several associated data types, as follows:
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Application Description Type Name Type Reference
ID ID
----------- ------------------- -------------------- ------ ---------
(TBD) Ethernet Interface Unicast MAC Address 0 (this
Parameters draft)
Maximum Frame Size 1 (this
draft)
7. References
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y.,
Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack
Encoding", RFC 3032, January 2001.
[RFC5332] Eckert, T., Rosen, E., Aggarwal, R., and Y. Rekhter, "MPLS
Multicast Encapsulations", RFC 5332, August 2008.
[RFC5654] Niven-Jenkins, B., Brungard, D., Betts, M., Sprecher, N.,
and S. Ueno, "Requirements of an MPLS Transport Profile",
RFC 5654, September 2009.
[RFC5960] Frost, D., Bryant, S., and M. Bocci, "MPLS Transport
Profile Data Plane Architecture", RFC 5960, August 2010.
7.2. Informative References
[RFC0826] Plummer, D., "Ethernet Address Resolution Protocol: Or
converting network protocol addresses to 48.bit Ethernet
address for transmission on Ethernet hardware", STD 37,
RFC 826, November 1982.
[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
September 2007.
[RFC5921] Bocci, M., Bryant, S., Frost, D., Levrau, L., and L.
Berger, "A Framework for MPLS in Transport Networks",
RFC 5921, July 2010.
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Authors' Addresses
Dan Frost (editor)
Cisco Systems
Email: danfrost@cisco.com
Stewart Bryant (editor)
Cisco Systems
Email: stbryant@cisco.com
Matthew Bocci (editor)
Alcatel-Lucent
Email: matthew.bocci@alcatel-lucent.com
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