Internet DRAFT - draft-wang-ccamp-oducn-fwk
draft-wang-ccamp-oducn-fwk
Internet Engineering Task Force Q. Wang, Ed.
Internet-Draft Y. Zhang
Intended status: Informational ZTE
Expires: May 4, 2017 October 31, 2016
GMPLS Routing and Signalling Framework for ODUCn
draft-wang-ccamp-oducn-fwk-00
Abstract
This document provides a framework to address the GMPLS routing and
signalling issues to support Generalized Multi-Protocol Label
Switching (GMPLS)control of Optical Transport Networks (OTNs) as
specified in ITU-T Recommendation G.709 as published in 2016.
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. G.709 Optical Transport Network . . . . . . . . . . . . . . . 3
3.1. OTN ODUCn layer network . . . . . . . . . . . . . . . . . 3
3.2. Time Slot Granularity . . . . . . . . . . . . . . . . . . 4
3.3. Structure of MSI Information . . . . . . . . . . . . . . 5
3.4. OTUCn sub rates (OTUCn-M) . . . . . . . . . . . . . . . . 6
4. Connection Management of ODUCn . . . . . . . . . . . . . . . 6
5. GMPLS Implications . . . . . . . . . . . . . . . . . . . . . 6
5.1. Implications for GMPLS Signalling . . . . . . . . . . . . 6
5.2. Implications for GMPLS Routing . . . . . . . . . . . . . 7
5.3. Implications for Control-Plane Backward Compatibility . . 7
6. Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . 7
7. Security Considerations . . . . . . . . . . . . . . . . . . . 7
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
9.1. Normative References . . . . . . . . . . . . . . . . . . 7
9.2. Informative References . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
Currently, Optical Transport Networks (OTNs) is widely used in the
transport network. Some operators already use control-plane
capabilities based on GMPLS to control optical transport network to
improve the network management efficiency.
The GMPLS signalling extensions defined in [RFC4328] provide the
mechanisms for basic GMPLS control of OTN based on the 2001 revision
of the G.709 specification. The 2012 revision of the G.709
specification, [G709-2012], introduce some new features, and the
GMPLS control of OTN based on the 2012 revision of the G.709
specification is covered in [RFC7062], [RFC7096], [RFC7138] and
[RFC7139]. The 2016 revision of the G.709 specification includes
some new features, such as OTUCn, ODUCn and OPUCn. The OTUCn
contains an optical data unit (ODUCn) and the ODUCn contains an
optical payload unit (OPUCn). OTUCn, ODUCn and OPUCn are presented
in an interface independent manner, by means of n OTUC, ODUC and OPUC
instances that are marked #1 to #n through inverse multiplexing.
This document reviews relevant aspects of OTN technology evolution
that affect the GMPLS control-plane protocols, examines why and how
to update the mechanisms described in former G.709 related documents
and describes the framework and solution for GMPLS control of ODUCn
network.
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For the purposes of the control plane, the OTN can be considered to
be comprised of ODU and wavelength (Optical Channel (OCh)/ Optical
Tributary Signal (OTSi)) layers. This document focuses on the
control of the ODU layer, with control of the wavelength layer
considered out of the scope.
1.1. 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 RFC 2119 [RFC2119].
2. Terminology
OPUCn Optical Payload Unit-Cn
ODUCn Optical Data Unit-Cn
OTUCn completely standardized Optical Transport Unit-Cn
OTUCn-M Optical Transport Unit-Cn with n OxUC overhead instances and
M 5G tributary slots
OTUCn completely standardized Optical Transport Unit-Cn
3. G.709 Optical Transport Network
This section provides an informative overview of the aspects of the
OTN impacting control-plane protocols. This overview is based on the
ITU-T Recommendations that contain the normative definition of the
OTN. Technical details regarding OTN architecture and interfaces are
provided in the relevant ITU-T Recommendations.
3.1. OTN ODUCn layer network
Figure 1 shows a simplified signal hierarchy of OTN ODUCn, which
illustrates the layers that are related to control plane.
client signal (OTN clients)
|
ODUCn
|
OTUCn
Figure 1: OTN ODUCn Signal Hierarchy
ODUCn can no be used to support non-OTN client signal. OTN client
signals (e.g. ODU0, ODU1, ODU2, ODU2e, ODU3, ODU4, ODUflex) are
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mapped into an ODUCn container, ODUCn container is then multiplexed
into OTUCn. The approximate bit rates of these signals are defined
in [G709-2016] and are reproduced in Figure 2.
+-------------------+------------------------------------+
| ODU Type | ODU nominal bit rate |
+-------------------+------------------------------------+
| ODU0 | 1,244,160 Kbps |
| ODU1 | 239/238 x 2,488,320 Kbps |
| ODU2 | 239/237 x 9,953,280 Kbps |
| ODU3 | 239/236 x 39,813,120 Kbps |
| ODU4 | 239/227 x 99,532,800 Kbps |
| ODUCn | n x 239/226 x 99 532 800 kbit/s |
| ODU2e | 239/237 x 10,312,500 Kbps |
| | |
| ODUflex for | |
|Constant Bit Rate | 239/238 x client signal bit rate |
| Client signals | |
| | |
|ODUflex for Generic| |
| Framing Procedure | Configured bit rate |
| - Framed (GFP-F) | |
| Mapped client | |
| signal | |
| | |
| ODUflex for IMP |s x 239/238 x 5 156 250 kbit/s |
| mapped client |s = 2, 8, n x 5 with n >= 1 |
| signals | |
| | |
| ODUflex for FlexE |103 125 000 x 240/238 x n/20 kbit/s |
| aware client |(n = n1 + n2 + .. + np) |
| signals | |
+-------------------+------------------------------------+
Figure 2: ODU Types and Bit Rates
3.2. Time Slot Granularity
The initial versions of G.709 referenced by [RFC4328] only provided a
single TS granularity, nominally 2.5 Gbps. [G709-2012] added an
additional TS granularity, nominally 1.25 Gbps. [G709-2012] added
another 5 Gbps TS granularity specially for ODUCn. The number of
tributary slots (TS) defined in [G709-2016] for each ODU are
reproduced in Figure 3.
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+------------+-------------------------------------+
| | Nominal TS capacity |
| ODU Server +-------------------------------------+
| | 1.25 Gbit/s | 2.5 Gbit/s | 5 Gbit/s |
+------------+-------------+------------+----------+
| ODU0 | 1 | N/A | N/A |
+------------+-------------+------------+----------+
| ODU1 | 2 | N/A | N/A |
+------------+-------------+------------+----------+
| ODU2 | 8 | 4 | N/A |
+------------+-------------+------------+----------+
| ODU3 | 32 | 16 | N/A |
+------------+-------------+------------+----------+
| ODU4 | 80 | N/A | N/A |
+------------+-------------+------------+----------+
| ODUCn | N/A | N/A | 20*n |
+------------+-------------+------------+----------+
Figure 3: Number of tributary slots (TS)
3.3. Structure of MSI Information
When multiplexing an OTN client signal into ODUCn, [G.709-2016]
specifies the information that has to be transported in-band in order
to allow for correct demultiplexing. This information, known as MSI,
is transported in the OPUCn overhead and is local to each link.
The MSI information is organized as a set of entries, with n entries
for each OPUC TS. The MSI indicates the ODTU content of each
tributary slot of an OPU. Two bytes are used for each tributary
slot. The information carried by each entry is:
- TS availability bit 1 indicates if the tributary slot is available
or unavailable.
- The TS occupation bit 9 indicates if the tributary slot is
allocated or unallocated.
- Payload Type: the type of the transported payload.
- TPN: the port number of the OTN client signal transported by the
ODUCn. The TPN is the same for all the TSs assigned to the transport
of the same OTN client signal.
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3.4. OTUCn sub rates (OTUCn-M)
An OTUCn with a bit rate that is not an integer multiple of 100 Gbit/
s is described as an OTUCn M, it carries n instances of OTUC
overhead, ODUC overhead and OPUC overhead together with M 5Gbit/s
OPUCn TS. An ODUCn M and OPUCn M are not defined. When an OTUCn M
is used to carry an ODUCn (20n-M) TS are marked as unavailable, in
the OPUCn multiplex structure identifier (MSI), since they cannot be
used to carry a client.
4. Connection Management of ODUCn
ODUCn based connection management is concerned with controlling the
connectivity of ODUCn paths. As described in [G.872], The ODUk
subnetwork does not support an ODUCn, which means intermediate ODUCn
points do not support the switching of ODUCn time slot, intermediate
ODUCn point only functions as a forwarding point. Once an ODUCn path
is used to transport client signal, the TS occupied will not changed
across the ODUCn network.
5. GMPLS Implications
The purpose of this section is to provide a set of requirements to be
evaluated for extensions of the current GMPLS protocol suite to
encompass OTN enhancements and connection management.
5.1. Implications for GMPLS Signalling
As described in Section 3, [G709-2016] introduced some new features,
such as OTUCn, ODUCn and OPUCn. The mechanisms defined in [RFC4328]
and [RFC7139] do not support such new OTN features, and protocol
extensions will be necessary to allow them to be controlled by a
GMPLS control plane. The following signaLling aspects should be
considered:
- Support for specifying new signal types and related traffic
information. The traffic parameters should be extended in a
signalling message to support the new ODUCn
- Support for LSP setup using different TS granularity
- Support for LSP setup of new ODUCn containers with related mapping
and multiplexing capabilities
- Support for TPN allocation and negotiation
- Support for LSP setup of OTUCn sub rates (OTUCn-M) path
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Note: ODU Virtual Concatenation (VCAT) and Link Capacity Adjustment
Scheme (LCAS) is not supported in ODUCn network.
5.2. Implications for GMPLS Routing
The path computation process needs to select a suitable route for an
ODUCn connection request. In order to perform the path computation,
it needs to evaluate the available bandwidth on one or more candidate
links. The routing protocol should be extended to convey sufficient
information to represent ODU Traffic Engineering (TE) topology.
Following requirements should be considered:
- Support for Tributary Slot Granularity advertisement
- Support for carrying the link multiplexing capability
The routing protocol should be able to indicate which link supports
the ODUCn forwarding.
- Support for advertisement of OTUCn sub rates support information
5.3. Implications for Control-Plane Backward Compatibility
TBD
6. Solutions
TBD
7. Security Considerations
TBD
8. IANA Considerations
TBD
9. References
9.1. Normative References
[G.709] Maarten, Vissers., "Interfaces for Optical Transport
Network", 2016.
[G.872] Malcolm, Betts., "Architecture of optical transport
networks (OTN)", 2016.
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,
<http://www.rfc-editor.org/info/rfc3209>.
[RFC3471] Berger, L., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Functional Description",
RFC 3471, DOI 10.17487/RFC3471, January 2003,
<http://www.rfc-editor.org/info/rfc3471>.
[RFC3473] Berger, L., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Resource ReserVation Protocol-
Traffic Engineering (RSVP-TE) Extensions", RFC 3473,
DOI 10.17487/RFC3473, January 2003,
<http://www.rfc-editor.org/info/rfc3473>.
[RFC3603] Marshall, W., Ed. and F. Andreasen, Ed., "Private Session
Initiation Protocol (SIP) Proxy-to-Proxy Extensions for
Supporting the PacketCable Distributed Call Signaling
Architecture", RFC 3603, DOI 10.17487/RFC3603, October
2003, <http://www.rfc-editor.org/info/rfc3603>.
[RFC4202] Kompella, K., Ed. and Y. Rekhter, Ed., "Routing Extensions
in Support of Generalized Multi-Protocol Label Switching
(GMPLS)", RFC 4202, DOI 10.17487/RFC4202, October 2005,
<http://www.rfc-editor.org/info/rfc4202>.
[RFC4203] Kompella, K., Ed. and Y. Rekhter, Ed., "OSPF Extensions in
Support of Generalized Multi-Protocol Label Switching
(GMPLS)", RFC 4203, DOI 10.17487/RFC4203, October 2005,
<http://www.rfc-editor.org/info/rfc4203>.
[RFC4204] Lang, J., Ed., "Link Management Protocol (LMP)", RFC 4204,
DOI 10.17487/RFC4204, October 2005,
<http://www.rfc-editor.org/info/rfc4204>.
9.2. Informative References
[RFC3945] Mannie, E., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Architecture", RFC 3945,
DOI 10.17487/RFC3945, October 2004,
<http://www.rfc-editor.org/info/rfc3945>.
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Authors' Addresses
Qilei Wang (editor)
ZTE
Nanjing
CN
Email: wang.qilei@zte.com.cn
Yuanbin Zhang
ZTE
Beijing
CN
Email: zhang.yuanbin@zte.com.cn
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