Internet Engineering Task Force (IETF) H. Long
Request for Comments: 8330 M. Ye
Category: Standards Track Huawei Technologies Co., Ltd.
ISSN: 2070-1721 G. Mirsky
ZTE
A. D'Alessandro
Telecom Italia S.p.A.
H. Shah
Ciena
February 2018
OSPF Traffic Engineering (OSPF-TE) Link Availability Extension
for Links with Variable Discrete Bandwidth
Abstract
A network may contain links with variable discrete bandwidth, e.g.,
copper
microwave and radio. copper. The bandwidth of such links may change
discretely in response to a changing external environment. The word
"availability" is typically used to describe such links during
network planning. This document defines a new type of Generalized
Switching Capability-Specific Information (SCSI) TLV to extend the
Generalized Multiprotocol Label Switching (GMPLS) Open Shortest Path
First (OSPF) routing protocol. The extension can be used for route
computation in a network that contains links with variable discrete
bandwidth. Note that this document only covers the mechanisms by
which the availability information is distributed. The mechanisms by
which availability information of a link is determined and the use of
the distributed information for route computation are outside the
scope of this document. It is intended that technology-specific
documents will reference this document to describe specific uses.
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 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8330.
Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved.
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction ....................................................3
1.1. Conventions Used in This Document ..........................3
2. Abbreviations ...................................................4
3. Overview ........................................................4
4. TE Metric Extension to OSPF-TE ..................................5
4.1. Availability SCSI-TLV ......................................5
4.2. Processing Procedures ......................................6
5. Security Considerations .........................................6
6. IANA Considerations .............................................7
7. References ......................................................7
7.1. Normative References .......................................7
7.2. Informative References .....................................8
Acknowledgments ...................................................10
Authors' Addresses ................................................10
1. Introduction
Some data-plane technologies, e.g., microwave and copper, allow
seamless changes of maximum physical bandwidth through a set of known
discrete values. The parameter "availability", as described in
[G.827], [F.1703], and [P.530], is often used to describe the link
capacity. The availability is a time scale, representing a
proportion of the operating time that the requested bandwidth is
ensured. To set up a Label Switched Path (LSP) across these links,
availability information is required by the nodes to verify the
bandwidth before making a bandwidth reservation. Assigning different
availability classes over such links provides for more efficient
planning of link capacity to support different types of services.
The link availability information will be determined by the operator
and is statically configured. It will usually be determined from the
availability requirements of the services expected to be carried on
the LSP. For example, voice service usually needs "five nines"
availability, while non-real-time services may adequately perform at
four or three nines availability. For the route computation, both
the availability information and the bandwidth resource information
are needed. Since different service types may need different
availability guarantees, multiple <availability, bandwidth> pairs may
be required to be associated with a link.
In this document, a new type of Generalized SCSI-TLV, the
Availability SCSI-TLV, is defined. It is intended that technology-
specific documents will reference this document to describe specific
uses. The signaling extension to support links with variable
discrete bandwidth is defined in [RSVP-TE-Availability].
1.1. Conventions Used in This Document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
2. Abbreviations
The following abbreviations are used in this document:
GMPLS Generalized Multiprotocol Label Switching
ISCD Interface Switching Capability Descriptor
LSA Link State Advertisement
LSP Label Switched Path
OSPF Open Shortest Path First
SCSI Switching Capability-Specific Information
SPF Shortest Path First
TE Traffic Engineering
TLV Type-Length-Value
3. Overview
A node that has link(s) with variable discrete bandwidth attached
should include an <availability, bandwidth> information list in its
OSPF-TE LSA messages. The list provides the mapping between the link
nominal bandwidth and its availability level. This information is
used for path calculation by the node(s). The setup of an LSP
requires this information to be flooded in the network and used by
the nodes or the PCE for the path computation. In this document, a
new type of Generalized SCSI-TLV, the Availability SCSI-TLV, is
defined. The computed path can then be provisioned via the signaling
protocol [RSVP-TE-Availability].
Note: The mechanisms described in this document only distribute
availability information. The methods for measuring the information
or using the information for route computation are outside the scope
of this document.
4. TE Metric Extension to OSPF-TE
4.1. Availability SCSI-TLV
The Generalized SCSI is defined in [RFC8258]. This document defines
a new type of Generalized SCSI-TLV called the Availability SCSI-TLV.
The Availability SCSI-TLV can be included one or more times. It 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Availability level |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LSP Bandwidth at Availability level n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 0x000A, 16 bits
Length: 2 octets (16 bits)
Availability level: 32 bits
This field is a binary32-format floating-point number as
defined by [IEEE754-2008]. The bytes are transmitted in
network order; that is, the byte containing the sign bit is
transmitted first. This field describes the decimal value of
the availability guarantee of the switching capability Switching Capability in the
Interface Switching Capability Descriptor object [RFC4202].
The value MUST be less than 1. The Availability level field is
usually expressed as the value 0.99/0.999/0.9999/0.99999.
LSP Bandwidth at Availability level n: 32 bits
This field is a 32-bit IEEE floating-point number as defined by
[IEEE754-2008]. The bytes are transmitted in network order;
that is, the byte containing the sign bit is transmitted first.
This field describes the LSP bandwidth for the Availability availability
level represented in the Availability level field. The units
are bytes per second.
4.2. Processing Procedures
The ISCD allows routing protocols such as OSPF to carry technology-
specific information in the "Switching Capability-specific
information" field; see [RFC4203]. A node advertising an interface
with a Switching Capability that supports variable discrete bandwidth
attached SHOULD contain one or more Availability SCSI-TLVs in its
OSPF-TE LSA messages. Each Availability SCSI-TLV provides
information about how much bandwidth a link can support for a
specified availability. This information may be used for path
calculation by the node(s).
The Availability SCSI-TLV MUST NOT be sent in ISCDs with Switching
Capability field values that have not been defined to support the
Availability SCSI-TLV. Non-supporting nodes would see such an
ISCD/LSA as malformed.
The absence of the Availability SCSI-TLV in an ISCD containing
Switching Capability field values that have been defined to support
the Availability SCSI-TLV SHALL be interpreted as representing the
fixed-bandwidth link with the highest availability value.
Only one Availability SCSI-TLV for the specific availability level
SHOULD be sent. If multiple TLVs are present, the Availability
SCSI-TLV with the lowest bandwidth value SHALL be processed. If an
Availability SCSI-TLV with an invalid value (e.g., larger than 1) is
received, the Availability SCSI-TLV will be ignored.
5. Security Considerations
This document specifies the contents of Opaque LSAs in OSPFv2.
Tampering with GMPLS-TE LSAs may have an effect on TE computations.
[RFC3630] suggests such mechanisms as the mechanism described in
[RFC2154] to protect the transmission of this information, and those
or other mechanisms should be used to secure and/or authenticate the
information carried in the Opaque LSAs. An analysis of the security
of OSPF is provided in [RFC6863] and applies to the OSPF extension
defined in this document. Any new mechanisms developed to protect
the transmission of information carried in Opaque LSAs will also
automatically protect the extension defined in this document.
Please refer to [RFC5920] for details on security threats; defensive
techniques; monitoring, detection, and reporting of security attacks;
and requirements.
6. IANA Considerations
This document introduces a new type for availability of the Generalized SCSI-TLV of the TE Link TLV
(Availability) that is carried in the TE Opaque OSPF-TE LSA for
OSPFv2. messages.
Technology-specific documents will reference this document to
describe the specific uses use of this Availability SCSI-TLV.
IANA created a registry called the "Generalized SCSI (Switching
Capability Specific Information) TLV Types" registry [RFC8258]. The
registry has been updated to include the following Availability
SCSI-TLV:
Type Description Switching Type Reference
------ ------------ -------------- ---------
0x000A Availability 5, 52 RFC 8330
New switching types are required in order to use the Availability
SCSI-TLV. IANA has registered the following in the "Switching Types"
registry:
Value Name Reference
----- -------------------------- ---------
5 PSC with GSCSI support RFC 8330
52 L2SC with GSCSI support RFC 8330
7. References
7.1. Normative References
[IEEE754-2008]
IEEE, "IEEE Standard for Floating-Point Arithmetic",
IEEE 754-2008, DOI 10.1109/IEEESTD.2008.4610935.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[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, <https://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,
<https://www.rfc-editor.org/info/rfc4203>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in
RFC 2119 Key Words", BCP 14, RFC 8174,
DOI 10.17487/RFC8174, May 2017,
<https://www.rfc-editor.org/info/rfc8174>.
[RFC8258] Ceccarelli, D. and L. Berger, "Generalized SCSI: A Generic
Structure for Interface Switching Capability Descriptor
(ISCD) Switching Capability Specific Information (SCSI)",
RFC 8258, DOI 10.17487/RFC8258, October 2017,
<https://www.rfc-editor.org/info/rfc8258>.
7.2. Informative References
[F.1703] International Telecommunication Union, "Availability
objectives for real digital fixed wireless links used in
27 500 km hypothetical reference paths and connections",
ITU-R Recommendation F.1703-0, January 2005,
<https://www.itu.int/rec/R-REC-F.1703-0-200501-I/en>.
[G.827] International Telecommunication Union, "Availability
performance parameters and objectives for end-to-end
international constant bit-rate digital paths", ITU-T
Recommendation G.827, September 2003,
<https://www.itu.int/rec/T-REC-G.827/en>.
[P.530] International Telecommunication Union, "Propagation data
and prediction methods required for the design of
terrestrial line-of-sight systems", ITU-R
Recommendation P.530-17, December 2017,
<https://www.itu.int/rec/R-REC-P.530/en>.
[RFC2154] Murphy, S., Badger, M., and B. Wellington, "OSPF with
Digital Signatures", RFC 2154, DOI 10.17487/RFC2154,
June 1997, <https://www.rfc-editor.org/info/rfc2154>.
[RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
(TE) Extensions to OSPF Version 2", RFC 3630,
DOI 10.17487/RFC3630, September 2003,
<https://www.rfc-editor.org/info/rfc3630>.
[RFC5920] Fang, L., Ed., "Security Framework for MPLS and GMPLS
Networks", RFC 5920, DOI 10.17487/RFC5920, July 2010,
<https://www.rfc-editor.org/info/rfc5920>.
[RFC6863] Hartman, S. and D. Zhang, "Analysis of OSPF Security
According to the Keying and Authentication for Routing
Protocols (KARP) Design Guide", RFC 6863,
DOI 10.17487/RFC6863, March 2013,
<https://www.rfc-editor.org/info/rfc6863>.
[RSVP-TE-Availability]
Long, H., Ye, M., Mirsky, G., D'Alessandro, A., and H.
Shah, "Ethernet Traffic Parameters with Availability
Information", Work in Progress, draft-ietf-ccamp-rsvp-te-
bandwidth-availability-07, August 2017.
Acknowledgments
The authors would like to thank Acee Lindem, Daniele Ceccarelli, and
Lou Berger for their comments on the document.
Authors' Addresses
Hao Long
Huawei Technologies Co., Ltd.
No. 1899, Xiyuan Avenue, Hi-tech Western District
Chengdu 611731
China
Phone: +86-18615778750
Email: longhao@huawei.com
Min Ye
Huawei Technologies Co., Ltd.
No. 1899, Xiyuan Avenue, Hi-tech Western District
Chengdu 611731
China
Email: amy.yemin@huawei.com
Greg Mirsky
ZTE
Email: gregimirsky@gmail.com
Alessandro D'Alessandro
Telecom Italia S.p.A.
Email: alessandro.dalessandro@telecomitalia.it
Himanshu Shah
Ciena Corp.
3939 North First Street
San Jose, CA 95134
United States of America
Email: hshah@ciena.com