One document matched: draft-fbb-mpls-tp-data-plane-00.xml
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<rfc category="std" docName="draft-fbb-mpls-tp-data-plane-00"
ipr="trust200902">
<front>
<title abbrev="MPLS-TP Data Plane Architecture">MPLS Transport
Profile Data Plane Architecture
</title>
<author fullname="Dan Frost" initials="D" role="editor" surname="Frost">
<organization>Cisco Systems</organization>
<address>
<email>danfrost@cisco.com</email>
</address>
</author>
<author fullname="Stewart Bryant" initials="S" role="editor"
surname="Bryant">
<organization>Cisco Systems</organization>
<address>
<email>stbryant@cisco.com</email>
</address>
</author>
<author fullname="Matthew Bocci" initials="M" role="editor"
surname="Bocci">
<organization>Alcatel-Lucent</organization>
<address>
<email>matthew.bocci@alcatel-lucent.com</email>
</address>
</author>
<date year="2010" />
<area>Routing</area>
<workgroup>MPLS</workgroup>
<keyword>MPLS</keyword>
<keyword>Internet-Draft</keyword>
<abstract>
<t>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 specifies the subset of these functions that comprises
the MPLS-TP data plane: the architectural layer concerned with the
encapsulation and forwarding of packets within an MPLS-TP
network.</t>
<t>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.</t>
</abstract>
<note title="Requirements Language">
<t>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 <xref
target="RFC2119">RFC 2119</xref>.</t>
</note>
</front>
<middle>
<section title="Introduction">
<t>The MPLS Transport Profile (MPLS-TP) <xref
target="I-D.ietf-mpls-tp-framework" /> is the set of protocol
functions that meet the requirements <xref target="RFC5654" /> for
the application of MPLS to the construction and operation of
packet-switched transport networks. Packet transport networks are
defined and described in <xref target="I-D.ietf-mpls-tp-framework"
/>.</t>
<t>This document specifies the subset of protocol functions that
comprises the MPLS-TP data plane: the architectural layer concerned
with the encapsulation and forwarding of packets within an MPLS-TP
network.</t>
<t>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.</t>
<section title="Scope">
<t>This document has the following purposes:
<list style="symbols">
<t>To identify the data-plane functions within the MPLS
Transport Profile</t>
<t>To indicate which of these data-plane functions an MPLS-TP
implementation is required to support</t>
</list>
Note that the MPLS-TP functions discussed in this document are
considered OPTIONAL unless stated otherwise.</t>
</section>
<section title="Terminology">
<texttable align="left" style="headers">
<ttcol>Term</ttcol>
<ttcol>Definition</ttcol>
<c>G-ACh</c>
<c>Generic Associated Channel</c>
<c>GAL</c>
<c>G-ACh Label</c>
<c>LER</c>
<c>Label Edge Router</c>
<c>LSP</c>
<c>Label Switched Path</c>
<c>LSR</c>
<c>Label Switching Router</c>
<c>MAC</c>
<c>Media Access Control</c>
<c>MPLS-TP</c>
<c>MPLS Transport Profile</c>
<c>OAM</c>
<c>Operations, Administration and Maintenance</c>
<c>PW</c>
<c>Pseudowire</c>
<c>QoS</c>
<c>Quality of Service</c>
</texttable>
<t>Additional definitions and terminology can be found in <xref
target="I-D.ietf-mpls-tp-framework" /> and <xref target="RFC5654"
/>.</t>
</section>
</section>
<section title="MPLS-TP Packet Encapsulation and Forwarding">
<t>This document defines the encapsulation and forwarding functions
applicable to packets traversing an MPLS-TP Label Switched Path
(LSP), Pseudowire (PW), or Section (see <xref target="entities" />
for the definitions of these transport entities). Encapsulation and
forwarding functions for packets outside an MPLS-TP LSP, PW, or
Section, and mechanisms for delivering packets to or from MPLS-TP
LSPs, PWs, and Sections, are outside the scope of this document.</t>
</section>
<section title="MPLS-TP Transport Entities" anchor="entities">
<t>The MPLS Transport Profile includes the following data-plane
transport entities:
<list style="symbols">
<t>Label Switched Paths (LSPs)</t>
<t>Sections</t>
<t>Pseudowires (PWs)</t>
</list>
</t>
<section title="Label Switched Paths">
<t>MPLS-TP LSPs are ordinary MPLS LSPs as defined in
<xref target="RFC3031" /> except as specifically noted otherwise
in this document.</t>
<section title="LSP Packet Encapsulation and Forwarding">
<t>Encapsulation and forwarding of packets traversing MPLS-TP
LSPs MUST follow standard MPLS packet encapsulation and
forwarding as defined in <xref target="RFC3031" /> and <xref
target="RFC3032" />, except as explicitly stated otherwise in
this document.</t>
<t>Data-plane support for Internet Protocol (IP) packet
encapsulation, addressing, and forwarding is OPTIONAL.</t>
<t>Data-plane Quality of Service capabilities are included in
the MPLS-TP in the form of the MPLS Differentiated Services
(DiffServ) architecture <xref target="RFC3270" />. Both E-LSP
and L-LSP MPLS DiffServ modes are included. The Traffic Class
field (formerly the EXP field) of an MPLS label follows the
definition of <xref target="RFC5462" /> and <xref
target="RFC3270" /> and MUST be processed according to the rules
specified in those documents.</t>
<t>The Pipe and Short Pipe DiffServ tunneling and TTL processing
models described in <xref target="RFC3270" /> and
<xref target="RFC3443" /> are included in the MPLS-TP. The
Uniform model is outside the scope of the MPLS-TP.</t>
<t>Per-platform, per-interface or other context-specific label
space <xref target="RFC5331" /> MAY be used for MPLS-TP LSPs.
Note that the requirements of a particular LSP type may dictate
which label spaces it can use.</t>
<t>Per-packet Equal-Cost Multi-Path (ECMP) load-balancing is
outside the scope of the MPLS-TP.</t>
<t>Penultimate Hop Popping (PHP) MUST be disabled by default on
MPLS-TP LSPs.</t>
<t>Fragmentation procedures as specified in
<xref target="RFC3032" /> are outside the scope of the
MPLS-TP.</t>
</section>
<section title="LSP Payloads">
<t>The MPLS-TP includes support for the following LSP payload
types:
<list style="symbols">
<t>Network-layer protocol packets</t>
<t>Pseudowire packets</t>
</list>
</t>
<t>The rules for processing LSP payloads that are network-layer
protocol packets SHALL be as specified in <xref target="RFC3032"
/> except as specifically noted otherwise in this document.</t>
<t>The rules for processing LSP payloads that are pseudowire
packets SHALL be as specified in <xref target="RFC3985" /> and
the attendant standards defined by the IETF Pseudowire Emulation
Edge-to-Edge (PWE3) Working Group.</t>
<t>Note that the payload of an MPLS-TP LSP may be a packet type
that itself contains one or more MPLS labels. This is true, for
instance, when the payload is a pseudowire or another MPLS-TP
LSP. From the data-plane perspective, however, an MPLS-TP
packet is an MPLS packet as specified in <xref target="RFC3032"
/>, and so in particular has precisely one label stack, and one
label in the stack with its S (Bottom of Stack) bit set to
1.</t>
</section>
<section title="LSP Types">
<t>The MPLS-TP includes the following LSP types:
<list style="symbols">
<t>Point-to-point unidirectional</t>
<t>Point-to-point associated bidirectional</t>
<t>Point-to-point co-routed bidirectional</t>
<t>Point-to-multipoint unidirectional</t>
</list>
</t>
<t>Point-to-point unidirectional LSPs are supported by the basic
MPLS architecture <xref target="RFC3031" /> and are REQUIRED to
function in the same manner in the MPLS-TP data plane except as
explicitly stated otherwise in this document.</t>
<t>A point-to-point associated bidirectional LSP between LSRs A
and B consists of two unidirectional point-to-point LSPs, one
from A to B and the other from B to A, which are regarded as a
pair providing a single logical bidirectional transport path.
The nodes A and B are REQUIRED to be aware of this pairing
relationship, but other nodes need not be.</t>
<t>A point-to-point co-routed bidirectional LSP is a
point-to-point associated bidirectional LSP with the additional
constraint that its two unidirectional component LSPs follow the
same path in the network. This means that if one of the
component LSPs follows the path through the nodes N0, ..., Nk,
originating on N0 and terminating on Nk, then the path of the
other component LSP is Nk, ..., N0, and that at each node an
ingress interface of one component LSP is an egress interface of
the other. In addition, each node along the path is REQUIRED to
be aware of the pairing relationship between the component
LSPs.</t>
<t>A point-to-multipoint unidirectional LSP functions in the
same manner in the data plane, with respect to basic label
processing and packet-switching operations, as a point-to-point
unidirectional LSP, with one difference: an LSR may have more
than one (egress interface, outgoing label) pair associated with
the LSP, and any packet it transmits on the LSP is transmitted
out all associated egress interfaces. Point-to-multipoint LSPs
are described in <xref target="RFC4875" /> and
<xref target="RFC5332" />.</t>
</section>
</section>
<section title="Sections">
<t>Two MPLS-TP LSRs are considered to be topologically adjacent at
a particular layer n >= 0 of the MPLS-TP LSP hierarchy if there
exists a link between them at the next lowest network layer. Such
a link, if it exists, will be either an MPLS-TP LSP (if n > 0)
or a data-link provided by the underlying server layer network (if
n = 0), and is referred to as an MPLS-TP Section at layer n of the
MPLS-TP LSP hierarchy. Thus, the links traversed by a layer n+1
MPLS-TP LSP are layer n MPLS-TP sections.</t>
<t>Note that the MPLS label stack associated with an MPLS-TP
section at layer n consists of n labels, in the absence of stack
optimisation mechanisms such as PHP. Note also that in order for
two LSRs to exchange MPLS-TP control packets over a section, an
additional label, the Generic Associated Channel Label (GAL) (see
<xref target="gach" />) must appear at the bottom of the label
stack.</t>
</section>
<section title="Pseudowires">
<t>The data-plane architectures for Single-Segment Pseudowires
<xref target="RFC3985" />, Multisegment Pseudowires <xref
target="RFC5659" /> and Point-to-Multipoint Pseudowires <xref
target="I-D.ietf-pwe3-p2mp-pw-requirements" />, and the associated
data-plane pseudowire protocol functions, as defined by the IETF
Pseudowire Emulation Edge-to-Edge (PWE3) Working Group, are
included in the MPLS-TP.</t>
<t>This document specifies no modifications or extensions to
pseudowire data-plane architectures or protocols.</t>
</section>
</section>
<section title="MPLS-TP Generic Associated Channel" anchor="gach">
<t>The MPLS Generic Associated Channel (G-ACh) mechanism is
specified in <xref target="RFC5586" /> and included in the MPLS-TP.
The G-ACh provides an auxiliary logical data channel associated with
MPLS-TP Sections, LSPs, and PWs in the data plane. The primary
purpose of the G-ACh in the context of MPLS-TP is to support
control, management, and OAM traffic associated with MPLS-TP
transport entities. The G-ACh MUST NOT be used to transport client
layer network traffic in MPLS-TP networks.</t>
</section>
<section title="Media-Specific Considerations">
<t>This section discusses considerations for support of the MPLS-TP
data plane by specific underlying server layer media.</t>
<section title="Ethernet">
<section title="Destination MAC Address Determination">
<t>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) <xref target="RFC0826" /> or IP
version 6 Neighbor Discovery protocol <xref target="RFC4861" />,
which allow the unicast MAC address of the peer device to be
learned dynamically.</t>
<t>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.</t>
<t>One possibility is for each node to be statically configured
with the MAC address of its peer. Static MAC address
configuration MAY be used in an MPLS-TP network, but can present
an administrative burden and lead to operational problems.</t>
<t>Another possibility is to use the Ethernet broadcast address,
but this may 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.</t>
<t>The preferred approach is therefore to use as the destination
MAC address an Ethernet multicast address reserved for MPLS-TP.
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 with this
destination MAC address by default.</t>
<t>[Editor's note: Decide what to say about multipoint Ethernet
and switched links. Decide if there is a need for protocol
mechanisms to support learning of the Ethernet unicast MAC
addresses of MPLS-TP peers that are not also IP peers.]</t>
</section>
</section>
<section title="Other Media">
<t>[Editor's note: Decide whether any considerations for media
other than Ethernet need to be mentioned.]</t>
</section>
</section>
<section title="Security Considerations">
<t>TBD</t>
</section>
<section title="IANA Considerations">
<t>A future version of this document will detail IANA considerations
for the allocation of a standard Ethernet multicast MAC address for
use in MPLS-TP networks.</t>
</section>
</middle>
<back>
<references title="Normative References">
<?rfc include='reference.RFC.2119'?>
<?rfc include='reference.RFC.3031'?>
<?rfc include='reference.RFC.3032'?>
<?rfc include='reference.RFC.5654'?>
<?rfc include='reference.RFC.5586'?>
<?rfc include='reference.RFC.3270'?>
<?rfc include='reference.RFC.3443'?>
<?rfc include='reference.RFC.5462'?>
<?rfc include='reference.RFC.5331'?>
<?rfc include='reference.RFC.4875'?>
<?rfc include='reference.RFC.5332'?>
</references>
<references title="Informative References">
<?rfc include='reference.I-D.ietf-mpls-tp-framework'?>
<?rfc include='reference.I-D.ietf-pwe3-p2mp-pw-requirements'?>
<?rfc include='reference.RFC.3985'?>
<?rfc include='reference.RFC.5659'?>
<?rfc include='reference.RFC.0826'?>
<?rfc include='reference.RFC.4861'?>
</references>
</back>
</rfc>
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