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IETF RFC 6002
Generalized MPLS (GMPLS) Data Channel Switching Capable (DCSC) and Channel Set Label Extensions
Last modified on Monday, October 11th, 2010
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Internet Engineering Task Force (IETF) L. Berger
Request for Comments: 6002 LabN
Updates: 3471, 3473, 3945, 4202, 4203, 5307 D. Fedyk
Category: Standards Track Alcatel-Lucent
ISSN: 2070-1721 October 2010
Generalized MPLS (GMPLS) Data Channel Switching Capable (DCSC)
and Channel Set Label Extensions
 Abstract
This document describes two technology-independent extensions to
Generalized Multi-Protocol Label Switching (GMPLS). The first
extension defines the new switching type Data Channel Switching
Capable. Data Channel Switching Capable interfaces are able to
support switching of the whole digital channel presented on single
channel interfaces. The second extension defines a new type of
generalized label and updates related objects. The new label is
called the Generalized Channel_Set Label and allows more than one
data plane label to be controlled as part of a Label Switched Path
(LSP).
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/RFC 6002.
Berger & Fedyk Standards Track PAGE 1 
RFC 6002 GMPLS DCSC Channel Extensions October 2010
Copyright Notice
Copyright (c) 2010 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
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction ....................................................2
1.1. Conventions Used in This Document ..........................3
2. Data Channel Switching ..........................................3
2.1. Compatibility ..............................................4
3. Generalized Channel_Set Label Related Formats ...................4
3.1. Generalized Channel_Set LABEL_REQUEST Object ...............4
3.2. Generalized Channel_Set LABEL Object .......................4
3.3. Other Label-Related Objects ................................7
3.4. Compatibility ..............................................7
4. IANA Considerations .............................................8
4.1. Data Channel Switching Type ................................8
4.2. Generalized Channel_Set LABEL_REQUEST Object ...............8
4.3. Generalized Channel_Set LABEL Object .......................8
5. Security Considerations .........................................9
6. References ......................................................9
6.1. Normative References .......................................9
6.2. Informative References ....................................10
Acknowledgments ...................................................10
1. Introduction
This document describes two technology-independent extensions to
Generalized Multi-Protocol Label Switching (GMPLS). Both of these
extensions were initially defined in the context of Ethernet
services, see [RFC 6004] and [RFC 6005], but are generic in nature and
may be useful to any switching technology controlled via GMPLS.
The first extension defines a new switching type, which is called
Data Channel Switching Capable (DCSC). DCSC interfaces are able to
support switching of the whole digital channel presented on single
channel interfaces. The second extension defines a new type of
Berger & Fedyk Standards Track PAGE 2
RFC 6002 GMPLS DCSC Channel Extensions October 2010
generalized label and updates related objects. The new label is
called the Generalized Channel_Set Label and allows more than one
data plane label to be controlled as part of a GMPLS Label Switched
Path (LSP).
1.1. Conventions Used in This Document
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 [RFC 2119].
2. Data Channel Switching
Current GMPLS switching types are defined in [RFC 3945] and [RFC 3471]
and support switching at the packet (PSC), frame (L2SC), time-slot
(TDM), frequency (LSC), and fiber (FSC) granularities. Parallel
definitions for these switching types are also made in [RFC 4202],
[RFC 4203], and [RFC 5307].
One type of switching that is not well represented in this current
set is switching that occurs when all data received on an ingress
port is switched through a network to an egress port. While there
are similarities between this level of switching and the "opaque
single wavelength" case, described in Section 3.5 of [RFC 4202], such
port-to-port switching is not limited to the optical switching
technology implied by the LSC type. FSC is also similar, but it is
restricted to fiber ports and also supports multiple data channels
within a fiber port.
This document defines a new switching type called Data Channel
Switching Capable (DCSC). Port switching seems a more intuitive
name, but this naming collides with PSC so is not used. DCSC
interfaces are able to support switching of the whole digital channel
presented on single channel interfaces. Interfaces that inherently
support multiple channels, e.g., Wavelength Division Multiplexing
(WDM) and channelized TDM interfaces, are specifically excluded from
this type. Any interface that can be represented as a single digital
channel are included. Examples include concatenated TDM and line-
encoded interfaces. Framed interfaces may also be included when they
support switching on an interface granularity, for example Ethernet
terminated at the physical (port) level and all traffic received on a
port is switched to a physical port at the LSP egress.
DCSC is represented in GMPLS, see [RFC 3471] and [RFC 4202], using the
value 125. The DCSC value is carried in routing protocols in the
Interface Switching Capability Descriptor defined in [RFC 4202], and
used in OSPF [RFC 4203] and IS-IS [RFC 5307]. These documents are not
otherwise modified by this document.
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RFC 6002 GMPLS DCSC Channel Extensions October 2010
The DCSC Switching Type may be used with the Generalized Label
Request object, [RFC 3473], or the Generalized Channel_Set
LABEL_REQUEST object defined below. Port labels, as defined in
[RFC 3471], SHOULD be used for LSPs signaled using the DCSC Switching
Type.
2.1. Compatibility
Transit and egress nodes that do not support the DCSC Switching Type
when receiving a Path message with a Label Request containing the
DCSC Switching Type will behave in the same way nodes generally
handle the case of an unsupported Switching Type. Specifically, per
[RFC 3473], such nodes are required to generate a PathErr message,
with a "Routing problem/Unsupported Encoding" indication.
Ingress nodes initiating a Path message containing a Label Request
containing the DCSC Switching Type, receiving such a PathErr
messages, then notify the requesting application user as appropriate.
3. Generalized Channel_Set Label Related Formats
This section defines a new type of generalized label and updates
related objects. This section updates the label-related definitions
of [RFC 3473]. The ability to communicate more than one label as part
of the same LSP was motivated by the support for the communication of
one or more VLAN IDs. Simple concatenation of labels as is done in
[RFC 4606] was deemed impractical given the large number of VLAN IDs
(up to 4096) that may need to be communicated. The formats defined
in this section are not technology specific and may be useful for
other switching technologies. The LABEL_SET object defined in
[RFC 3473] serves as the foundation for the defined formats.
3.1. Generalized Channel_Set LABEL_REQUEST Object
The Generalized Channel_Set LABEL_REQUEST object is used to indicate
that the Generalized Channel_Set LABEL object is to be used with the
associated LSP. The format of the Generalized Channel_Set
LABEL_REQUEST object is the same as the Generalized LABEL_REQUEST
object and uses a C-Type of 5.
3.2. Generalized Channel_Set LABEL Object
The Generalized Channel_Set LABEL Object communicates one or more
labels, all of which can be used equivalently in the data path
associated with a single LSP. The format of the Generalized
Channel_Set LABEL Object is based on the LABEL_SET object defined in
[RFC 3473]. It differs from the LABEL_SET object in that the full set
may be represented in a single object rather than the multiple
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RFC 6002 GMPLS DCSC Channel Extensions October 2010
objects required by the [RFC 3473] LABEL_SET object. The object MUST
be used on LSPs that use the Generalized Channel_Set LABEL_REQUEST
object. The object MUST be processed per [RFC 3473]. Make-before-
break procedures, see [RFC 3209], SHOULD be used when modifying the
Channel_Set LABEL object.
The format of the Generalized Channel_Set LABEL object is:
o Generalized Channel_Set LABEL object: Class = 16, C-Type = 4
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Channel_Set Subobject 1 |
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: : :
: : :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Channel_Set Subobject N |
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Channel_Set Subobject size is measured in bytes and MUST always
be a multiple of 4, and at least 4, and has the following format:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Action | Num Subchannels | Label Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Subchannel 1 |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... | :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ :
: : :
: : :
: : :
: : :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Subchannel N |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... | Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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RFC 6002 GMPLS DCSC Channel Extensions October 2010
Action: 8 bits
See [RFC 3471] for definition of actions. Range actions SHOULD be
used when possible to minimize the size of the Channel_Set LABEL
Object.
Number of Subchannels: 10 bits
Indicates the number of subchannels carried in the subobject.
When the number of subchannels required exceeds the limit of the
field, i.e., 1024, multiple Channel_Set Subobjects MUST be used.
Note that the size of the subobject may result in a Path message
being larger than a single unfragmented IP packet. See Section
4.4 of [RFC 6004] for an example of how this case may be handled.
A value of zero (0) has special meaning and MAY be used in either
the LABEL or UPSTREAM_LABEL object. A value of zero (0) is used
in a LABEL or UPSTREAM_LABEL object to indicate that the
subchannel(s) used in the corresponding (downstream or upstream)
direction MUST match the subchannel(s) carried in the reverse
directions label object. When value of zero (0) is used, no
subchannels are included in the Channel_Set Subobject and only one
Channel_Set Subobject may be present. The zero (0) value MUST NOT
be used in both the LABEL and UPSTREAM_LABEL objects of the same
LSP. Note that unacceptable label values continue to be handled
according to [RFC 3209] and [RFC 3473], i.e., they result in PathErr
or ResvErr messages with a "Routing problem/Unacceptable label
value" indication. For example, in the case where a Resv message
containing a zero (0) in both the LABEL and UPSTREAM_LABEL objects
is received, the node would generate a ResvErr message.
Label Type: 14 bits
See [RFC 3473] for a description of this field.
Subchannel: Variable
See [RFC 3471] for a description of this field. Note that this
field might not be 32-bit aligned.
Padding: Variable
Padding is used to ensure that the length of a Channel_Set
Subobject meets the multiple of 4 byte size requirement stated
above. The field is only required when the Subchannel field is
not 32-bit aligned and the number of included Subchannel fields
result in the Subobject not being 32-bit aligned.
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RFC 6002 GMPLS DCSC Channel Extensions October 2010
The Padding field MUST be included when the number of bits
represented in all the Subchannel fields included in a Generalized
Channel_Set Subobject result in the Subobject not being 32-bit
aligned. When present, the Padding field MUST have a length that
results in the Subobject being 32-bit aligned. When present, the
Padding field MUST be set to a zero (0) value on transmission and
MUST be ignored on receipt. These bits SHOULD be passed through
unmodified by transit nodes.
Note that the overall length of a Channel_Set Subobject is
determined based on the value of the Num Subchannels field
together with the size of each Subchannel field as well as any
required padding. The size of the Subchannel field is uniquely
identified by the Label Type field.
3.3. Other Label-Related Objects
The previous section introduced a new LABEL object. As such the
formats of the other label-related objects and subobjects are also
impacted. Processing of these objects and subobjects is not modified
and remains per their respective specifications. The other label
related objects and subobjects are defined in [RFC 3473] and include:
- SUGGESTED_LABEL object
- LABEL_SET object
- ACCEPTABLE_LABEL_SET object
- UPSTREAM_LABEL object
- RECOVERY_LABEL object
- Label ERO subobject
- Label RRO subobject
The label-related objects and subobjects each contain a Label field,
all of which may carry any label type. As any label type may be
carried, the introduction of a new label type means that the new
label type may be carried in the Label field of each of the label-
related objects and subobjects. No new definition needs to specified
as their original specification is label-type agnostic.
3.4. Compatibility
Transit and egress nodes that do not support the Generalized
Channel_Set Label related formats will first receive a Path message
containing Generalized Channel_Set LABEL_REQUEST object. When such a
node receives the Path message, per [RFC 3209], it will send a PathErr
with the error code "Unknown object C_Type".
Berger & Fedyk Standards Track PAGE 7
RFC 6002 GMPLS DCSC Channel Extensions October 2010
Ingress nodes initiating a Path message containing a Generalized
Channel_Set LABEL_REQUEST object on receiving such a PathErr
messages, then notify the requesting application user as appropriate.
4. IANA Considerations
IANA has assigned new values for namespaces defined in this document
and summarized in this section. The registries are available from
http://www.iana.org.
4.1. Data Channel Switching Type
IANA has made the following assignment in the "Switching Types"
section of the "GMPLS Signaling Parameters" registry.
Value Type Reference
----- ------------------------------------ ---------
125 Data Channel Switching Capable (DCSC) [RFC 6002]
The assigned value is reflected in IANAGmplsSwitchingTypeTC of the
IANA-GMPLS-TC-MIB available from http://www.iana.org.
4.2. Generalized Channel_Set LABEL_REQUEST Object
IANA has made the following assignment in the "Class Names, Class
Numbers, and Class Types" section of the "RSVP PARAMETERS" registry.
A new class type for the existing LABEL_REQUEST Object class number
(19) with the following definition:
Class Types or C-Types:
5 Generalized Channel_Set [RFC 6002]
4.3. Generalized Channel_Set LABEL Object
IANA has made the following assignment in the "Class Names, Class
Numbers, and Class Types" section of the "RSVP PARAMETERS" registry.
A new class type for the existing RSVP_LABEL Object class number (16)
with the following definition:
Class Types or C-Types:
4 Generalized Channel_Set [RFC 6002]
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RFC 6002 GMPLS DCSC Channel Extensions October 2010
5. Security Considerations
This document introduces new message object formats for use in GMPLS
signaling [RFC 3473]. It does not introduce any new signaling
messages, nor change the relationship between LSRs that are adjacent
in the control plane. As such, this document introduces no
additional security considerations. See [RFC 3473] for relevant
security considerations. Additionally, the existing framework for
MPLS and GMPLS security is documented in [RFC 5920].
6. References
6.1. Normative References
[RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC 3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, December 2001.
[RFC 3471] Berger, L., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Functional Description", RFC
3471, January 2003.
[RFC 3473] Berger, L., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Resource ReserVation Protocol-
Traffic Engineering (RSVP-TE) Extensions", RFC 3473,
January 2003.
[RFC 3945] Mannie, E., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Architecture", RFC 3945, October 2004.
[RFC 4202] Kompella, K., Ed., and Y. Rekhter, Ed., "Routing
Extensions in Support of Generalized Multi-Protocol Label
Switching (GMPLS)", RFC 4202, October 2005.
[RFC 4203] Kompella, K., Ed., and Y. Rekhter, Ed., "OSPF Extensions
in Support of Generalized Multi-Protocol Label Switching
(GMPLS)", RFC 4203, October 2005.
[RFC 5307] Kompella, K., Ed., and Y. Rekhter, Ed., "IS-IS Extensions
in Support of Generalized Multi-Protocol Label Switching
(GMPLS)", RFC 5307, October 2008.
Berger & Fedyk Standards Track PAGE 9
RFC 6002 GMPLS DCSC Channel Extensions October 2010
6.2. Informative References
[RFC 4606] Mannie, E. and D. Papadimitriou, "Generalized Multi-
Protocol Label Switching (GMPLS) Extensions for
Synchronous Optical Network (SONET) and Synchronous
Digital Hierarchy (SDH) Control", RFC 4606, August 2006.
[RFC 5920] Fang, L., Ed., "Security Framework for MPLS and GMPLS
Networks", RFC 5920, July 2010.
[RFC 6004] Berger, L. and D. Fedyk, "Generalized MPLS (GMPLS) Support
for Metro Ethernet Forum and G.8011 Ethernet Service
Switching", RFC 6004, October 2010.
[RFC 6005] Berger, L. and D. Fedyk, "Generalized MPLS (GMPLS) Support
for Metro Ethernet Forum and G.8011 User Network Interface
(UNI)", RFC 6005, October 2010.
Acknowledgments
Dimitri Papadimitriou provided substantial textual contributions to
this document and coauthored earlier versions of this document.
The authors would like to thank Evelyne Roch, Stephen Shew, and
Adrian Farrel for their valuable comments.
Authors' Addresses
Lou Berger
LabN Consulting, L.L.C.
Phone: +1-301-468-9228
EMail: lberger@labn.net
Don Fedyk
Alcatel-Lucent
Groton, MA, 01450
Phone: +1-978-467-5645
EMail: donald.fedyk@alcatel-lucent.com
Berger & Fedyk Standards Track PAGE 10
Generalized MPLS (GMPLS) Data Channel Switching Capable (DCSC) and Channel Set Label Extensions
RFC TOTAL SIZE: 23090 bytes
PUBLICATION DATE: Monday, October 11th, 2010
LEGAL RIGHTS: The IETF Trust (see BCP 78)
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