Internet DRAFT - draft-berger-ccamp-swcaps-update
draft-berger-ccamp-swcaps-update
Internet Draft Lou Berger (LabN)
Updates: 3471, 4202, 4203, 5307 Julien Meuric (France Telecom)
Category: Standards Track
Expiration Date: January 4, 2013
July 4, 2012
Revised Definition of The GMPLS Switching Capability and Type Fields
draft-berger-ccamp-swcaps-update-02.txt
Abstract
GMPLS provides control for multiple switching technologies, and
hierarchical switching within a technology. GMPLS routing and
signaling use common values to indicate switching technology type.
These values are carried in routing in the Switching Capability
field, and in signaling in the Switching Type field. While the
values using in these fields are the primary indicators of the
technology and hierarchy level being controlled, the values are
not consistently defined and used across the different
technologies supported by GMPLS. This document is intended to
resolve the inconsistent definition and use of the Switching
Capability and Type fields by narrowly scoping the meaning and use
of the fields. This document updates any document that uses the
GMPLS Switching Capability and Types fields, in particular RFC
3471, RFC 4202, RFC 4203, and RFC 5307.
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 January 4, 2013
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Copyright and License Notice
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This document is subject to BCP 78 and the IETF Trust's Legal
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described in the Simplified BSD License.
1. Introduction
Generalized Multi-Protocol Label Switching (GMPLS) provides control
for multiple switching technologies. It also supports hierarchical
switching within a technology. The original GMPLS Architecture, per
[RFC3945], included support for five types of switching capabilities.
An additional type was also been defined in [RFC6002]. The switching
types defined in these documents include:
1. Packet Switch Capable (PSC)
2. Layer-2 Switch Capable (L2SC)
3. Time-Division Multiplex Capable (TDM)
4. Lambda Switch Capable (LSC)
5. Fiber-Switch Capable (FSC)
6. Data Channel Switching Capable (DCSC)
Support for the original types was defined for routing in [RFC4202],
[RFC4203] and [RFC5307], where the types were represented in the
Switching Capability (Switching Cap) field. In general, hierarchy
within a type is addressed in a type-specific fashion and a single
Switching Capability field value is defined per type. The exception
to this is PSC which was assigned four values to indicate four levels
of hierarchy: PSC-1, PSC-2, PSC-3 and PSC-4. The same values used in
routing are defined for signaling in [RFC3471], and are carried in
the Switching Type field. Following the IANA registry, we refer to
the values used in the routing Switching Capability field and
signaling Switching Type field as Switching Types.
In general, a Switching Type does not indicate a specific data plane
technology, but rather this needs to be inferred from context. For
example L2SC was defined to cover Ethernet and ATM, and TDM was
defined to cover both SONET/SDH [RFC4606] and G.709 [RFC4328]. The
basic assumption was that different technologies of the same type
would never operate within the same control, i.e., signaling and
routing, domains.
The past approach in assignment of Switching Types has proven to be
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problematic from two perspectives. The first issue is that there are
examples of switching technologies were there are different levels of
switching that can be performed within the same technology. For
example, there are multiple types of Ethernet switching that may
occur within a provider network. The second issues is that the
Switching Capability field value is used in routing to indicate the
format of the Switching Capability-specific information (SCSI) field,
and that an implicit mapping of type to SCSI format is impractical
for implementations that support multiple switching technologies.
These issues led to the introduction of two new types for Ethernet in
[RFC6004] and [RFC6060], namely:
7. Ethernet Virtual Private Line (EVPL)
8. 802_1 PBB-TE
An additional value is also envisioned to be assigned in support of
G.709v3 by [GMPLS-G709] in order to disambiguate the format of the
SCSI field.
While a common representation of hierarchy levels within a switching
technology certainly fits the design objectives of GMPLS, the
definition of multiple PSC Switching Types has also proven to be of
little value. Notably, there are no known uses of PSC-2, PSC-3 and
PSC-4.
This document proposes to resolve such inconsistent definitions and
uses of the Switching Types by reducing the scope of the related
fields and narrowing their use. In particular this document proposes
deprecating the use of the Switching Types as an identifier of
hierarchy levels within a switching technology, and limit its use to
identification of a per-switching technology SCSI field format.
This document updates any document that uses the GMPLS Switching
Capability and Switching Type fields, in particular RFCs 3471, 4202,
4203, and 5307.
1.1. Current Switching Type Definition
The Switching Type values are carried in both routing and signaling.
Values are identified in the IANA GMPLS Signaling Parameters
Switching Type registry, which is currently located at
http://www.iana.org/assignments/gmpls-sig-parameters/gmpls-sig-
parameters.xml
For routing, a common information element is defined to carry
switching type values for both OSPF and IS-IS routing protocols in
[RFC4202]. Per [RFC4202], switching type values are carried in a
Switching Capability (Switching Cap) field in an Interface Switching
Capability Descriptor. This information shares a common formatting
in both OSPF, as defined by [RFC4203] and in IS-IS, as defined by
[RFC5307]:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Switching Cap | Encoding | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Switching Capability-specific information |
| (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
and
The content of the Switching Capability specific information field
depends on the value of the Switching Capability field.
Similarly, the Switching Type field is defined as part of a common
format for use by GMPLS signaling protocols in [RFC3471] and is used
by [RFC3473]:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LSP Enc. Type |Switching Type | G-PID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Switching Type: 8 bits
Indicates the type of switching that should be performed on a
particular link. This field is needed for links that advertise
more than one type of switching capability. This field should
map to one of the values advertised for the corresponding link
in the routing Switching Capability Descriptor ...
1.2. 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 [RFC2119].
2. Revised Switching Type Definition
This document modifies the definition of Switching Type. The
definitions are slightly different for routing and signaling and are
described in the following sections.
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2.1. Routing -- Switching Cap Field
For routing, i.e., [RFC4202], [RFC4203] and [RFC5307], the following
definition should be used for Switching Cap field:
The Switching Cap field indicates the type of switching being
advertised via GMPLS Switching Type values. A different Switching
Type value SHOULD be used for each data plane technology even when
those technologies share the same type of multiplexing or
switching. For example, Time Division Multiplexing (TDM)
technologies that have different multiplexing structures, such as
SDH [G.707] and OTN [G.709], should use two different Switching
Types.
As the format of the Switching Capability specific information
field is dependent on the value of this field, a different
Switching Type value MUST be used to differentiate between
different Switching Capability specific information field formats.
This definition does not modify the format of the Interface
Switching Capability Descriptor.
Note that from a practical standpoint, this means that any time a new
switching technology might use a different Switching Capability
specific information field format, that a new Switching Type SHOULD
be used.
2.2. Signaling -- Switching Type Field
For signaling, i.e., [RFC3471] which is used by [RFC3473], the
following definition should be used for Switching Type field:
Indicates the type of switching that should be performed on a
particular link via GMPLS Switching Type values. This field maps
to one of the values advertised for the corresponding link in the
routing Switching Capability Descriptor, see [RFC4203] and
[RFC5307].
Note that from a practical standpoint, there is no change in the
definition of this field.
2.3. Assigned Switching Types
This document deprecates the following Switching Types:
Value Name
2 Packet-Switch Capable-2 (PSC-2)
3 Packet-Switch Capable-3 (PSC-3)
4 Packet-Switch Capable-4 (PSC-4)
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These values SHOULD NOT be treated as reserved values, i.e.,
SHOULD NOT be generated and SHOULD be ignored upon receipt.
3. Compatibility
For existing implementations, the primary impact of this document is
deprecating the use of PSC-2, 3 and 4. At the time of publication,
there are no known deployments (or even implementations) that make
use of these values so there is no compatibility issues for current
routing and signaling implementations.
4. Security Considerations
This document impacts the values carried in a single field in
signaling and routing. As no new protocol formats or mechanisms are
defined, there are no particular security implications raised by this
document.
For a general discussion on MPLS and GMPLS related security issues,
see the MPLS/GMPLS security framework [RFC5920].
5. IANA Considerations
IANA needs to deprecate and redefine the registry. In particular the
Switching Types portion of the Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Parameters should be revised to read:
Switching Types
Registration Procedures
Standards Action
Reference
[RFC3471][RFC4328][This.draft]
Value Name Reference
0 Unassigned
1 Packet-Switch Capable-1 (PSC-1) [RFC3471]
2 Deprecated [This.draft]
3 Deprecated [This.draft]
4 Deprecated [This.draft]
5-29 Unassigned
30 Ethernet Virtual Private Line (EVPL) [RFC6004]
31-39 Unassigned
40 802_1 PBB-TE [RFC6060]
41-50 Unassigned
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51 Layer-2 Switch Capable (L2SC) [RFC3471]
52-99 Unassigned
100 Time-Division-Multiplex Capable (TDM) [RFC3471]
101-124 Unassigned
125 Data Channel Switching Capable (DCSC) [RFC6002]
126-149 Unassigned
150 Lambda-Switch Capable (LSC) [RFC3471]
151-199 Unassigned
200 Fiber-Switch Capable (FSC) [RFC3471]
201-255 Unassigned
6. Acknowledgments
We thank John Drake for highlighting the current inconsistent
definitions associated with the Switching Capability and Type Fields.
Daniele Ceccarelli provided valuable feedback on this document.
7. References
7.1. Normative References
[RFC2119] Bradner, S., "RFC Key Words Key words for use in RFCs to
Indicate Requirement Levels", RFC 2119, March 1997.
[RFC3471] Berger, L., "Generalized Multi-Protocol Label Switching
(GMPLS) Signaling Functional Description", RFC 3471,
January 2003.
[RFC4202] Kompella, K., Rekhter, Y., "Routing Extensions in
Support of Generalized Multi-Protocol Label Switching
(GMPLS)", RFC 4202, October 2005.
[RFC4203] Kompella, K., Rekhter, Y., "OSPF Extensions in Support
of Generalized Multi-Protocol Label Switching (GMPLS)",
RFC 4203, October 2005.
[RFC5307] Kompella, K., Rekhter, Y., "IS-IS Extensions in Support
of Generalized Multi-Protocol Label Switching (GMPLS)",
RFC 5307, October 2008.
7.2. Informative References
[G.707] ITU-T Recommendation G.707/Y.1322 (2007), "Network node
interface for the synchronous digital hierarchy (SDH)".
[G.709] ITU-T Recommendation G.709/Y.1331 (2009), "Interfaces for
the Optical Transport Network (OTN)".
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[GMPLS-G709] Zhang, F., Li, D., Li, H., Belotti, S., Ceccarelli,
D., "Framework for GMPLS and PCE Control of G.709
Optical Transport Networks", work in progress,
draft-ietf-ccamp-gmpls-g709-framework.
[RFC3473] Berger, L., "Generalized Multi-Protocol Label Switching
(GMPLS) Signaling Resource ReserVation Protocol-Traffic
Engineering (RSVP-TE) Extensions", RFC 3473, January
2003.
[RFC3945] Mannie, E., "Generalized Multi-Protocol Label Switching
(GMPLS) Architecture", RFC 3945, October 2004.
[RFC4328] Papadimitriou, D., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Extensions for G.709 Optical
Transport Networks Control", RFC 4328, January 2006.
[RFC4606] Mannie, E., Papadimitriou, D., "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., "Security Framework for MPLS and GMPLS
Networks", RFC 5920, July 2010.
[RFC6002] Berger, L., Fedyk, D., "Generalized MPLS (GMPLS) Data
Channel Switching Capable (DCSC) and Channel Set Label
Extensions", RFC 6002, October 2010.
[RFC6004] Berger, L., Fedyk, D., "Generalized MPLS (GMPLS) Support
for Metro Ethernet Forum and G.8011 Ethernet Service
Switching", RFC 6004, front 2010.
[RFC6060] Fedyk, D., Shah, H., Bitar, N., Takacs, A., "Generalized
Multiprotocol Label Switching (GMPLS) Control of
Ethernet Provider Backbone Traffic Engineering
(PBB-TE)", RFC 6060, March 2011.
8. Authors' Addresses
Lou Berger
LabN Consulting, L.L.C.
Phone: +1-301-468-9228
Email: lberger@labn.net
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Julien Meuric
France Telecom
Research & Development
2, avenue Pierre Marzin
22307 Lannion Cedex - France
Phone: +33 2 96 05 28 28
Email: julien.meuric@orange-ftgroup.com
Berger, et. al. Standards Track [Page 9]
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