Internet DRAFT - draft-ietf-ccamp-gmpls-general-constraints-ospf-te
draft-ietf-ccamp-gmpls-general-constraints-ospf-te
Network work group Fatai Zhang
Internet Draft Young Lee
Intended status: Standards Track Jianrui Han
Huawei
G. Bernstein
Grotto Networking
Yunbin Xu
CATR
Expires: September 5, 2015 March 6, 2015
OSPF-TE Extensions for General Network Element Constraints
draft-ietf-ccamp-gmpls-general-constraints-ospf-te-10.txt
Abstract
Generalized Multiprotocol Label Switching (GMPLS) can be used to
control a wide variety of technologies including packet switching
(e.g., MPLS), time-division (e.g., SONET/SDH, Optical Transport
Network (OTN)), wavelength (lambdas), and spatial switching (e.g.,
incoming port or fiber to outgoing port or fiber). In some of these
technologies, network elements and links may impose additional
routing constraints such as asymmetric switch connectivity, non-
local label assignment, and label range limitations on links. This
document describes Open Shortest Path First (OSPF) routing protocol
extensions to support these kinds of constraints under the control
of GMPLS.
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with
the provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other documents
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at any time. It is inappropriate to use Internet-Drafts as
reference material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html
This Internet-Draft will expire on September 5, 2015.
Copyright Notice
Copyright (c) 2015 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.
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 [RFC2119].
Table of Contents
1. Introduction...................................................3
2. Node Information...............................................4
2.1. Connectivity Matrix.......................................4
3. Link Information...............................................4
3.1. Port Label Restrictions...................................5
4. Routing Procedures.............................................5
5. Scalability and Timeliness.....................................6
5.1. Different Sub-TLVs into Multiple LSAs.....................6
5.2. Decomposing a Connectivity Matrix into Multiple Matrices..7
6. Security Considerations........................................7
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7. Manageability..................................................8
8. IANA Considerations............................................8
8.1. Node Information..........................................8
8.2. Link Information..........................................9
9. References.....................................................9
9.1. Normative References......................................9
9.2. Informative References...................................10
10. Authors' Addresses ..........................................10
Acknowledgment...................................................12
1. Introduction
Some data plane technologies that require the use of a GMPLS control
plane impose additional constraints on switching capability and
label assignment. In addition, some of these technologies should be
capable of performing non-local label assignment based on the nature
of the technology, e.g., wavelength continuity constraint in
Wavelength Switched Optical Network (WSON) [RFC6163]. Such
constraints can lead to the requirement for link by link label
availability in path computation and label assignment.
[GEN-Encode] provides efficient encodings of information needed by
the routing and label assignment process in technologies such as
WSON and are potentially applicable to a wider range of
technologies. The encoding provided in [GEN-Encode] is protocol-
neutral and can be used in routing, signaling and/or Path
Computation Element communication protocol extensions.
This document defines extensions to the OSPF routing protocol based
on [GEN-Encode] to enhance the Traffic Engineering (TE) properties
of GMPLS TE which are defined in [RFC3630], [RFC4202], and [RFC4203].
The enhancements to the TE properties of GMPLS TE links can be
advertised in OSPF TE LSAs. The TE LSA, which is an opaque LSA with
area flooding scope [RFC3630], has only one top-level
Type/Length/Value (TLV) triplet and has one or more nested sub-TLVs
for extensibility. The top-level TLV can take one of three values (1)
Router Address [RFC3630], (2) Link [RFC3630], (3) Node Attribute
[RFC5786]. In this document, we enhance the sub-TLVs for the Link
TLV in support of the general network element constraints under the
control of GMPLS.
The detailed encoding of OSPF extensions are not defined in this
document. [GEN-Encode] provides encoding details.
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2. Node Information
According to [GEN-Encode], the additional node information
representing node switching asymmetry constraints includes Node ID
and connectivity matrix. Except for the Node ID, which should comply
with Routing Address described in [RFC3630], the other pieces of
information are defined in this document.
Per [GEN-Encode], this document defines the Connectivity Matrix Sub-
TLV of the Node Attribute TLV defined in [RFC5786]. The new Sub-TLV
has Type TBD1 (to be assigned by IANA).
In some specific technologies, e.g., WSON networks, the Connectivity
Matrix sub-TLV may be optional, which depends on the control plane
implementations. Usually, for example, in WSON networks,
Connectivity Matrix sub-TLV may be advertised in the LSAs since WSON
switches are currently asymmetric. If no Connectivity Matrix sub-TLV
is included, it is assumed that the switches support symmetric
switching.
2.1. Connectivity Matrix
If the switching devices supporting certain data plane technology is
asymmetric, it is necessary to identify which input ports and labels
can be switched to some specific labels on a specific output port.
The Connectivity Matrix is used to identify these restrictions,
which can represent either the potential connectivity matrix for
asymmetric switches (e.g., ROADMs and such) or fixed connectivity
for an asymmetric device such as a multiplexer as defined in
[RFC7446].
The Connectivity Matrix is a sub-TLV of the Node Attribute TLV. The
length is the length of value field in octets. The meaning and
format of this sub-TLV value field are defined in Section 2.1 of
[GEN-Encode]. One sub-TLV contains one matrix. The Connectivity
Matrix sub-TLV may occur more than once to contain multiple matrices
within the Node Attribute TLV. In addition a large connectivity
matrix can be decomposed into smaller sub-matrices for transmission
in multiple LSAs as described in Section 5.
3. Link Information
The most common link sub-TLVs nested in the top-level link TLV are
already defined in [RFC3630], [RFC4203]. For example, Link ID,
Administrative Group, Interface Switching Capability Descriptor
(ISCD), Link Protection Type, Shared Risk Link Group Information
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(SRLG), and Traffic Engineering Metric are among the typical link
sub-TLVs.
Per [GEN-Encode], this document defines the Port Label Restrictions
Sub-TLV of the Link TLV defined in [RFC3630]. The new Sub-TLV has
Type TBD2 (to be assigned by IANA).
Generally all the sub-TLVs above are optional, which depends on the
control plane implementations. The Port Label Restrictions sub-TLV
will not be advertised when there are no restrictions on label
assignment.
3.1. Port Label Restrictions
Port label restrictions describe the label restrictions that the
network element (node) and link may impose on a port. These
restrictions represent what labels may or may not be used on a link
and are intended to be relatively static. For increased modeling
flexibility, port label restrictions may be specified relative to
the port in general or to a specific connectivity matrix.
For example, the Port Label Restrictions describes the wavelength
restrictions that the link and various optical devices such as OXCs,
ROADMs, and waveband multiplexers may impose on a port in WSON.
These restrictions represent what wavelength may or may not be used
on a link and are relatively static. The detailed information about
port label restrictions is described in [RFC7446].
The Port Label Restrictions sub-TLV is a sub-TLV of the Link TLV.
The length is the length of value field in octets. The meaning and
format of this sub-TLV value field are defined in Section 2.2 of
[GEN-Encode]. The Port Label Restrictions sub-TLV may occur more
than once to specify a complex port constraint within the link TLV.
4. Routing Procedures
All the sub-TLVs are nested in top-level TLV(s) and contained in
Opaque LSAs. The flooding rules of Opaque LSAs are specified in
[RFC2328], [RFC5250], [RFC3630], and [RFC4203].
Considering the routing scalability issues in some cases, the
routing protocol should be capable of supporting the separation of
dynamic information from relatively static information to avoid
unnecessary updates of static information when dynamic information
is changed. A standards-compliant approach is to separate the
dynamic information sub-TLVs from the static information sub-TLVs,
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each nested in a separate top-level TLV ([RFC3630 and RFC5876]), and
advertise them in the separate OSPF TE LSAs.
For node information, since the Connectivity Matrix information is
static, the LSA containing the Node Attribute TLV can be updated
with a lower frequency to avoid unnecessary updates.
For link information, a mechanism MAY be applied such that static
information and dynamic information of one TE link are contained in
separate Opaque LSAs. For example, the Port Label Restrictions
information sub-TLV could be nested in separate top level link TLVs
and advertised in the separate LSAs.
As with other TE information, an implementation typically takes
measures to avoid rapid and frequent updates of routing information
that could cause the routing network to become swamped. See
[RFC3630] Section 3 for related details.
5. Scalability and Timeliness
This document has defined two sub-TLVs for describing generic
routing contraints. The examples given in [GEN-Encode] show that
very large systems, in terms of label count or ports, can be very
efficiently encoded. However there has been concern expressed that
some possible systems may produce LSAs that exceed the IP Maximum
Transmission Unit (MTU) and that methods be given to allow for the
splitting of general constraint LSAs into smaller LSAs that are
under the MTU limit. This section presents a set of techniques that
can be used for this purpose.
5.1. Different Sub-TLVs into Multiple LSAs
Two sub-TLVs are defined in this document:
1. Connectivity Matrix (Node Attribute TLV)
2. Port Label Restrictions (Link TLV)
The Connectivity Matrix can be carried in the Node Attribute TLV as
defined in [RFC5786] while the Port Label Restrictions can be
carried in an Link TLV of which there can be at most one in an LSA
as defined in [RFC3630]. Note that the Port Label Restrictions are
relatively static, i.e., only would change with hardware changes or
significant system reconfiguration.
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5.2. Decomposing a Connectivity Matrix into Multiple Matrices
In the highly unlikely event that a Connectivity Matrix sub-TLV by
itself would result in an LSA exceeding the MTU, a single large
matrix can be decomposed into sub-matrices. Per [GEN-Encode] a
connectivity matrix just consists of pairs of input and output ports
that can reach each other and hence such this decomposition would be
straightforward. Each of these sub-matrices would get a unique
matrix identifier per [GEN-Encode].
From the point of view of a path computation process, prior to
receiving an LSA with a Connectivity Matrix sub-TLV, no connectivity
restrictions are assumed, i.e., the standard GMPLS assumption of any
port to any port reachability holds. Once a Connectivity Matrix sub-
TLV is received then path computation would know that connectivity
is restricted and use the information from all Connectivity Matrix
sub-TLVs received to understand the complete connectivity potential
of the system. Prior to receiving any Connectivity Matrix sub-TLVs
path computation may compute a path through the system when in fact
no path exists. In between the reception of an additional
Connectivity Matrix sub-TLV path computation may not be able to find
a path through the system when one actually exists. Both cases are
currently encountered and handled with existing GMPLS mechanisms.
Due to the reliability mechanisms in OSPF the phenomena of late or
missing Connectivity Matrix sub-TLVs would be relatively rare.
In case where the new sub-TLVs or their attendant encodings are
malformed, the proper action would be to log the problem and ignore
just the sub-TLVs in GMPLS path computations rather than ignoring
the entire LSA.
6. Security Considerations
This document does not introduce any further security issues other
than those discussed in [RFC3630], [RFC4203], and [RFC5250].
For general security aspects relevant to Generalized Multiprotocol
Label Switching (GMPLS)-controlled networks, please refer to
[RFC5920].
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7. Manageability
No existing management tools handle the additional TE parameters as
defined in this document and distributed in OSPF-TE. The existing
MIB module contained in [RFC6825] allows the TE information
distributed by OSPF-TE to be read from a network node: this MIB
module could be augmented (possibly by a sparse augmentation) to
report this new information.
The current environment in the IETF favors NETCONF [RFC6241] and
YANG [RFC6020] over SNMP and MIB modules. Work is in progress in
the TEAS working group to develop a YANG module to represent the
generic TE information that may be present in a Traffic Engineering
Database (TED). This model may be extended to handle the additional
information described in this document to allow that information to
be read from network devices or exchanged between consumers of the
TED. Furthermore, links state export using BGP [BGP-LS] enables the
export of TE information from a network using BGP. Work could
realistically be done to extend BGP-LS to also carry the information
defined in this document.
It is not envisaged that the extensions defined in this document
will place substantial additional requirements on Operations,
Management, and Administration (OAM) mechanisms currently used to
diagnose and debug OSPF systems. However, tools that examine the
contents of opaque LSAs will need to be enhanced to handle these new
sub-TLVs.
8. IANA Considerations
IANA is requested to allocate new sub-TLVs as defined in Sections 2
and 3 as follows:
8.1. Node Information
IANA maintains the "Open Shortest Path First (OSPF) Traffic
Engineering TLVs" registry with a sub-registry called "Types for
sub-TLVs of TE Node Attribute TLV". IANA is requested to assign a
new code point as follows:
Type | Sub-TLV | Reference
-------+-------------------------------+------------
TBD1 | Connectivity Matrix | [This.I-D]
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8.2. Link Information
IANA maintains the "Open Shortest Path First (OSPF) Traffic
Engineering TLVs" registry with a sub-registry called "Types for
sub-LVs of TE Link TLV". IANA is requested to assign a new code
point as follows:
Type | Sub-TLV | Reference
-------+-----------------------------------+------------
TBD2 | Port Label Restrictions | [This.I-D]
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998.
[RFC3630] Katz, D., Kompella, K., and Yeung, D., "Traffic
Engineering (TE) Extensions to OSPF Version 2", RFC 3630,
September 2003.
[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.
[RFC5250] L. Berger, I. Bryskin, A. Zinin, R. Coltun "The OSPF
Opaque LSA Option", RFC 5250, July 2008.
[RFC5786] R. Aggarwal and K. Kompella,"Advertising a Router's Local
Addresses in OSPF Traffic Engineering (TE) Extensions",
RFC 5786, March 2010.
[GEN-Encode] G. Bernstein, Y. Lee, D. Li, W. Imajuku, " General
Network Element Constraint Encoding for GMPLS Controlled
Networks", work in progress: draft-ietf-ccamp-general-
constraint-encode.
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9.2. Informative References
[RFC6020] M. Bjorklund, Ed., "YANG - A Data Modeling Language for
the Network Configuration Protocol (NETCONF)", RFC 6020,
October 2010.
[RFC6163] Y. Lee, G. Bernstein, W. Imajuku, "Framework for GMPLS and
PCE Control of Wavelength Switched Optical Networks
(WSON)", RFC 6163, February 2011.
[RFC6241] R. Enns, Ed., M. Bjorklund, Ed., Schoenwaelder, Ed., A.
Bierman, Ed., "Network Configuration Protocol (NETCONF)",
RFC 6241, June 2011.
[RFC6825] M. Miyazawa, T. Otani, K. Kumaki, T. Nadeau, "Traffic
Engineering Database Management Information Base in
Support of MPLS-TE/GMPLS", RFC 6825, January 2013.
[RFC7446] Y. Lee, G. Bernstein, D. Li, W. Imajuku, "Routing and
Wavelength Assignment Information Model for Wavelength
Switched Optical Networks", RFC 7446, February 2015.
[RFC5920] L. Fang, Ed., "Security Framework for MPLS and GMPLS
Networks", RFC 5920, July 2010.
[BGP-LS] H. Gredler, J. Medved, S. Previdi, A. Farrel, S. Ray,
"North-Bound Distribution of Link-State and TE Information
using BGP", work in progress: draft-ietf-idr-ls-
distribution.
10. Contributors
Guoying Zhang
China Academy of Telecommunication Research of MII
11 Yue Tan Nan Jie Beijing, P.R.China
Phone: +86-10-68094272
Email: zhangguoying@mail.ritt.com.cn
Dan Li
Huawei Technologies Co., Ltd.
F3-5-B R&D Center, Huawei Base
Bantian, Longgang District
Shenzhen 518129 P.R.China
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Phone: +86-755-28973237
Email: danli@huawei.com
Ming Chen
European Research Center
Huawei Technologies
Riesstr. 25, 80992 Munchen, Germany
Phone: 0049-89158834072
Email: minc@huawei.com
Yabin Ye
European Research Center
Huawei Technologies
Riesstr. 25, 80992 Munchen, Germany
Phone: 0049-89158834074
Email: yabin.ye@huawei.com
Authors' Addresses
Fatai Zhang
Huawei Technologies
F3-5-B R&D Center, Huawei Base
Bantian, Longgang District
Shenzhen 518129 P.R.China
Phone: +86-755-28972912
Email: zhangfatai@huawei.com
Young Lee
Huawei Technologies
5360 Legacy Drive, Building 3
Plano, TX 75023
USA
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Phone: (469)277-5838
Email: leeyoung@huawei.com
Jianrui Han
Huawei Technologies Co., Ltd.
F3-5-B R&D Center, Huawei Base
Bantian, Longgang District
Shenzhen 518129 P.R.China
Phone: +86-755-28977943
Email: hanjianrui@huawei.com
Greg Bernstein
Grotto Networking
Fremont CA, USA
Phone: (510) 573-2237
Email: gregb@grotto-networking.com
Yunbin Xu
China Academy of Telecommunication Research of MII
11 Yue Tan Nan Jie Beijing, P.R.China
Phone: +86-10-68094134
Email: xuyunbin@mail.ritt.com.cn
Acknowledgment
We thank Ming Chen and Yabin Ye from DICONNET Project who provided
valuable information for this document.
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