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/rfc6002.
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Copyright Notice
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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 [RFC6004] and [RFC6005], 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
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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).
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].
Current GMPLS switching types are defined in [RFC3945] and [RFC3471] 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 [RFC4202], [RFC4203], and [RFC5307].
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 [RFC4202], 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 [RFC3471] and [RFC4202], using the value 125. The DCSC value is carried in routing protocols in the Interface Switching Capability Descriptor defined in [RFC4202], and used in OSPF [RFC4203] and IS-IS [RFC5307]. These documents are not otherwise modified by this document.
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The DCSC Switching Type may be used with the Generalized Label Request object, [RFC3473], or the Generalized Channel_Set LABEL_REQUEST object defined below. Port labels, as defined in [RFC3471], SHOULD be used for LSPs signaled using the DCSC Switching Type.
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 [RFC3473], 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.
This section defines a new type of generalized label and updates related objects. This section updates the label-related definitions of [RFC3473]. 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 [RFC4606] 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 [RFC3473] serves as the foundation for the defined formats.
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.
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 [RFC3473]. 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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objects required by the [RFC3473] 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 [RFC3473]. Make-before- break procedures, see [RFC3209], 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
RFC 6002 GMPLS DCSC Channel Extensions October 2010
Action: 8 bits
See [RFC3471] 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 [RFC6004] 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 [RFC3209] and [RFC3473], 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.
See [RFC3471] 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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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.
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 [RFC3473] and include:
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.
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 [RFC3209], it will send a PathErr with the error code "Unknown object C_Type".
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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.
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.
RFC 6002 GMPLS DCSC Channel Extensions October 2010
5. Security Considerations
This document introduces new message object formats for use in GMPLS signaling [RFC3473]. 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 [RFC3473] for relevant security considerations. Additionally, the existing framework for MPLS and GMPLS security is documented in [RFC5920].
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3209] 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.
[RFC3945] Mannie, E., Ed., "Generalized Multi-Protocol Label Switching (GMPLS) Architecture", RFC 3945, October 2004.
[RFC4202] Kompella, K., Ed., and Y. Rekhter, Ed., "Routing Extensions in Support of Generalized Multi-Protocol Label Switching (GMPLS)", RFC 4202, October 2005.
[RFC4203] Kompella, K., Ed., and Y. Rekhter, Ed., "OSPF Extensions in Support of Generalized Multi-Protocol Label Switching (GMPLS)", RFC 4203, October 2005.
[RFC5307] Kompella, K., Ed., and Y. Rekhter, Ed., "IS-IS Extensions in Support of Generalized Multi-Protocol Label Switching (GMPLS)", RFC 5307, October 2008.
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[RFC4606] 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.
[RFC5920] Fang, L., Ed., "Security Framework for MPLS and GMPLS Networks", RFC 5920, July 2010.
[RFC6004] Berger, L. and D. Fedyk, "Generalized MPLS (GMPLS) Support for Metro Ethernet Forum and G.8011 Ethernet Service Switching", RFC 6004, October 2010.
[RFC6005] 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.