Network Working Group D. Katz
Internet Draft Juniper Networks
Category: Standards Track D. Yeung
Expires: February 2003 Procket Networks
K. Kompella
Juniper Networks
August 2002
Traffic Engineering Extensions to OSPF Version 2
draft-katz-yeung-ospf-traffic-07.txt
Status
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all provisions of Section 10 of RFC2026.
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Copyright Notice
Copyright (C) The Internet Society (2002). All Rights Reserved.
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Abstract
This document describes extensions to the OSPF protocol version 2 to
support intra-area Traffic Engineering, using Opaque Link State
Advertisements.
Changes
Changes from the -06 version (this section to be removed before
publication).
Comments from the ADs incorporated, as well as minor editing changes
to conform to draft-rfc-editor-rfc2223bis-02.txt.
Clean up front page headers.
(First page)
Clarify that this memo is for *intra-area* TE.
(Title, Abstract, section 1.2)
Add a "Conventions" section (rfc 2119).
(Section 1.3)
Clarify what should be done with Reserved field in section 2.2.
(Section 2.2)
Add an IANA Considerations section.
(Section 2.3.2, 2.4.2 and 8)
Clarify "IEEE Floating Point Format", and add reference.
(Section 2.4.2)
Clarify text for Resource Class/Color (match IS-IS TE text).
(Section 2.5.9)
Add text on originating TE LSAs.
(Section 3)
Broke up references into Normative and Informative (for now,
IS-IS TE is Informative, pending reply from Routing ADs).
Add IPR Notices and Full Copyright Notice, as per rfc 2026.
1. Introduction
This document specifies a method of adding traffic engineering
capabilities to OSPF Version 2 [1]. The architecture of traffic
engineering is described in [2]. The semantic content of the
extensions is essentially identical to the corresponding extensions
to IS-IS [3]. It is expected that the traffic engineering extensions
to OSPF will continue to mirror those in IS-IS.
The extensions provide a way of describing the traffic engineering
topology (including bandwidth and administrative constraints) and
distributing this information within a given OSPF area. This
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topology does not necessarily match the regular routed topology,
though this proposal depends on Network LSAs to describe multiaccess
links.
1.1. Applicability
Many of the extensions specified in this document are in response to
the requirements stated in [2], and thus are referred to as "traffic
engineering extensions", and are also commonly associated with MPLS
Traffic Engineering. A more accurate (albeit bland) designation is
"extended link attributes", as what is proposed is simply to add more
attributes to links in OSPF advertisements.
The information made available by these extensions can be used to
build an extended link state database just as router LSAs are used to
build a "regular" link state database; the difference is that the
extended link state database (referred to below as the traffic
engineering database) has additional link attributes. Uses of the
traffic engineering database include:
o monitoring the extended link attributes;
o local constraint-based source routing; and
o global traffic engineering.
For example, an OSPF-speaking device can participate in an OSPF area,
build a traffic engineering database, and thereby report on the
reservation state of links in that area.
In "local constraint-based source routing", a router R can compute a
path from a source node A to a destination node B; typically, A is R
itself, and B is specified by a "router address" (see below). This
path may be subject to various constraints on the attributes of the
links and nodes that the path traverses, e.g., use green links that
have unreserved bandwidth of at least 10Mbps. This path could then
be used to carry some subset of the traffic from A to B, forming a
simple but effective means of traffic engineering. How the subset of
traffic is determined, and how the path is instantiated is beyond the
scope of this document; suffice it to say that one means of defining
the subset of traffic is "those packets whose IP destinations were
learned from B", and one means of instantiating paths is using MPLS
tunnels. As an aside, note that constraint-based routing can be NP-
hard, or even unsolvable, depending on the nature of the attributes
and constraints and thus many implementations will use heuristics.
Consequently, we don't attempt to sketch an algorithm here.
Finally, for "global traffic engineering", a device can build a
traffic engineering database, input a traffic matrix and an
optimization function, crunch on the information, and thus compute
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optimal or near-optimal routing for the entire network. The device
can subsequently monitor the traffic engineering topology and react
to changes by recomputing the optimal routes.
1.2. Limitations
As mentioned above, this document specifies extensions and procedures
for intra-area distribution of Traffic Engineering information.
Methods for inter-area and inter-AS (Autonomous System) are not
discussed here.
The extensions specified in this document capture the reservation
state of point-to-point links. The reservation state of multiaccess
links is not accurately reflected, except in the special case that
there are only two devices in the multiaccess subnetwork.
This document also does not support unnumbered links. This
deficiency is addressed in [4]; see also [5] and [6].
1.3. Conventions
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 [7].
2. LSA Format
2.1. LSA type
This extension makes use of the Opaque LSA [8].
Three types of Opaque LSAs exist, each of which has different
flooding scope. This proposal uses only Type 10 LSAs, which have
area flooding scope.
One new LSA is defined, the Traffic Engineering LSA. This LSA
describes routers, point-to-point links, and connections to
multiaccess networks (similar to a Router LSA). For traffic
engineering purposes, the existing Network LSA suffices for
describing multiaccess links, so no additional LSA is defined for
this purpose.
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2.2. LSA ID
The LSA ID of an Opaque LSA is defined as having eight bits of type
and 24 bits of type-specific data. The Traffic Engineering LSA uses
type 1. The remaining 24 bits are broken up into eight bits of
reserved space (which SHOULD be zero on transmission and ignored on
receipt) and sixteen bits of instance:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 1 | Reserved | Instance |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Instance field is an arbitrary value used to maintain multiple
Traffic Engineering LSAs. A maximum of 65536 Traffic Engineering
LSAs may be sourced by a single system. The LSA ID has no
topological significance.
2.3. LSA Format Overview
2.3.1. LSA Header
The Traffic Engineering LSA starts with the standard LSA header:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS age | Options | 10 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 1 | Reserved | Instance |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertising Router |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS sequence number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS checksum | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2.3.2. TLV Header
The LSA payload consists of one or more nested Type/Length/Value
(TLV) triplets for extensibility. The format of each TLV is:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Length field defines the length of the value portion in octets
(thus a TLV with no value portion would have a length of zero). The
TLV is padded to four-octet alignment; padding is not included in
the length field (so a three octet value would have a length of
three, but the total size of the TLV would be eight octets). Nested
TLVs are also 32-bit aligned. Unrecognized types are ignored.
This memo defines Types 1 and 2. See the IANA Considerations section
for allocation of new Types.
2.4. LSA payload details
An LSA contains one top-level TLV.
There are two top-level TLVs defined:
1 - Router Address
2 - Link
2.4.1. Router Address TLV
The Router Address TLV specifies a stable IP address of the
advertising router that is always reachable if there is any
connectivity to it. This is typically implemented as a "loopback
address"; the key attribute is that the address does not become
unusable if an interface is down. In other protocols this is known
as the "router ID," but for obvious reasons this nomenclature is
avoided here.
If IS-IS is also active in the domain, this address can also be used
to compute the mapping between the OSPF and IS-IS topologies. For
example, suppose a router R is advertising both IS-IS and OSPF
Traffic Engineering LSAs, and suppose further that some router S is
building a single Traffic Engineering Database (TED) based on both
IS-IS and OSPF TE information. R may then appear as two separate
nodes in S's TED; however, if both the IS-IS and OSPF LSAs generated
by R contain the same Router Address, then S can determine that the
IS-IS TE LSA and the OSPF TE LSA from R are indeed from a single
router.
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The router address TLV is type 1, and has a length of 4, and the
value is the four octet IP address. It must appear in exactly one
Traffic Engineering LSA originated by a router.
2.4.2. Link TLV
The Link TLV describes a single link. It is constructed of a set of
sub-TLVs. There are no ordering requirements for the sub-TLVs.
Only one Link TLV shall be carried in each LSA, allowing for fine
granularity changes in topology.
The Link TLV is type 2, and the length is variable.
The following sub-TLVs are defined:
1 - Link type (1 octet)
2 - Link ID (4 octets)
3 - Local interface IP address (4 octets)
4 - Remote interface IP address (4 octets)
5 - Traffic engineering metric (4 octets)
6 - Maximum bandwidth (4 octets)
7 - Maximum reservable bandwidth (4 octets)
8 - Unreserved bandwidth (32 octets)
9 - Administrative group (4 octets)
This memo defines sub-Types 1 through 9. See the IANA Considerations
section for allocation of new sub-Types.
The Link Type and Link ID sub-TLVs are mandatory, i.e., must appear
exactly once. All other sub-TLVs defined here may occur at most
once. These restrictions need not apply to future sub-TLVs.
Unrecognized sub-TLVs are ignored.
Various values below use the (32 bit) IEEE Floating Point format.
For quick reference, this format is as follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|S| Exponent | Fraction |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where S is the sign; Exponent is the exponent base 2 in "excess 127"
notation; and Fraction is the mantissa - 1, with an implied binary
point in front of it. Thus the above represents the value
(-1)**(S) * 2**(Exponent-127) * (1 + Fraction)
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For more details, refer to [9].
2.5. Sub-TLV Details
2.5.1. Link Type
The Link Type sub-TLV defines the type of the link:
1 - Point-to-point
2 - Multiaccess
The Link Type sub-TLV is TLV type 1, and is one octet in length.
2.5.2. Link ID
The Link ID sub-TLV identifies the other end of the link. For point-
to-point links, this is the Router ID of the neighbor. For
multiaccess links, this is the interface address of the designated
router. The Link ID is identical to the contents of the Link ID
field in the Router LSA for these link types.
The Link ID sub-TLV is TLV type 2, and is four octets in length.
2.5.3. Local Interface IP Address
The Local Interface IP Address sub-TLV specifies the IP address(es)
of the interface corresponding to this link. If there are multiple
local addresses on the link, they are all listed in this sub-TLV.
The Local Interface IP Address sub-TLV is TLV type 3, and is 4N
octets in length, where N is the number of local addresses.
2.5.4. Remote Interface IP Address
The Remote Interface IP Address sub-TLV specifies the IP address(es)
of the neighbor's interface corresponding to this link. This and the
local address are used to discern multiple parallel links between
systems. If the Link Type of the link is Multiaccess, the Remote
Interface IP Addess is set to 0.0.0.0 .
The Remote Interface IP Address sub-TLV is TLV type 4, and is 4N
octets in length, where N is the number of neighbor addresses.
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2.5.5. Traffic Engineering Metric
The Traffic Engineering Metric sub-TLV specifies the link metric for
traffic engineering purposes. This metric may be different than the
standard OSPF link metric. Typically, this metric is assigned by a
network admistrator.
The Traffic Engineering Metric sub-TLV is TLV type 5, and is four
octets in length.
2.5.6. Maximum Bandwidth
The Maximum Bandwidth sub-TLV specifies the maximum bandwidth that
can be used on this link in this direction (from the system
originating the LSA to its neighbor), in IEEE floating point format.
This is the true link capacity. The units are bytes per second.
The Maximum Bandwidth sub-TLV is TLV type 6, and is four octets in
length.
2.5.7. Maximum Reservable Bandwidth
The Maximum Reservable Bandwidth sub-TLV specifies the maximum
bandwidth that may be reserved on this link in this direction, in
IEEE floating point format. Note that this may be greater than the
maximum bandwidth (in which case the link may be oversubscribed).
This SHOULD be user-configurable; the default value should be the
Maximum Bandwidth. The units are bytes per second.
The Maximum Reservable Bandwidth sub-TLV is TLV type 7, and is four
octets in length.
2.5.8. Unreserved Bandwidth
The Unreserved Bandwidth sub-TLV specifies the amount of bandwidth
not yet reserved at each of the eight priority levels, in IEEE
floating point format. The values correspond to the bandwidth that
can be reserved with a setup priority of 0 through 7, arranged in
increasing order with priority 0 occurring at the start of the sub-
TLV, and priority 7 at the end of the sub-TLV. The initial values
(before any bandwidth is reserved) are all set to the Maximum
Reservable Bandwidth. Each value will be less than or equal to the
Maximum Reservable Bandwidth. The units are bytes per second.
The Unreserved Bandwidth sub-TLV is TLV type 8, and is 32 octets in
length.
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2.5.9. Administrative Group
The Administrative Group sub-TLV contains a 4-octet bit mask assigned
by the network administrator. Each set bit corresponds to one
administrative group assigned to the interface. A link may belong to
multiple groups.
By convention the least significant bit is referred to as 'group 0',
and the most significant bit is referred to as 'group 31'.
The Administrative Group is also called Resource Class/Color [2].
The Administrative Group sub-TLV is TLV type 9, and is four octets in
length.
3. Elements of Procedure
Routers shall originate Traffic Engineering LSAs whenever the LSA
contents change, and whenever otherwise required by OSPF (an LSA
refresh, for example). Note that this does not mean that every
change must be flooded immediately; an implementation MAY set
thresholds (for example, a bandwidth change threshold) that trigger
immediate flooding, and initiate flooding of other changes after a
short time interval. In any case, the origination of Traffic
Engineering LSAs SHOULD be rate-limited to at most one every
MinLSInterval [1].
Upon receipt of a changed Traffic Engineering LSA or Network LSA
(since these are used in traffic engineering calculations), the
router should update its traffic engineering database. No SPF or
other route calculations are necessary.
4. Compatibility Issues
There should be no interoperability issues with routers that do not
implement these extensions, as the Opaque LSAs will be silently
ignored.
The result of having routers that do not implement these extensions
is that the traffic engineering topology will be missing pieces;
however, if the topology is connected, TE paths can still be
calculated and ought to work.
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5. Normative References
[1] Moy, J., "OSPF Version 2", RFC 2328, April 1998.
[4] Kompella, K., Rekhter, Y., et al, "OSPF Extensions in Support of
Generalized MPLS," work in progress.
[6] Kompella, K., and Rekhter, Y., "Signalling Unnumbered Links in
RSVP-TE," work in progress.
[7] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[8] Coltun, R., "The OSPF Opaque LSA Option," RFC 2370, July 1998.
[9] IEEE, "IEEE Standard for Binary Floating-Point Arithmetic",
Standard 754-1985, 1985 (ISBN 1-5593-7653-8).
6. Informative References
[2] Awduche, D., et al, "Requirements for Traffic Engineering Over
MPLS," RFC 2702, September 1999.
[3] Smit, H. and T. Li, "ISIS Extensions for Traffic Engineering,"
work in progress.
[5] Kompella, K., Rekhter, Y., and Kullberg, A., "Signalling
Unnumbered Links in CR-LDP," work in progress.
[10] Narten, T., and Alvestrand, H., "Guidelines for Writing an IANA
Considerations Section in RFCs", RFC 2434, BCP 26, October 1998.
7. Security Considerations
This document raises no new security issues for OSPF.
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8. IANA Considerations
The top level Types in a TE LSA as well as Types for sub-TLVs in a TE
Link TLV are to be registered with IANA.
Following the guidelines set in [10], top level Types in TE LSAs from
3 through 32767 are to be assigned by Expert Review (the said Expert
to be decided by the IESG). Types from 32768 through 65535 are
reserved for Private Use. In all cases, assigned values Types MUST
be registered with IANA.
Also, sub-Types of a TE Link TLV from 10 to 32767 are to be assigned
by Expert Review; values from 32768 through 32772 are reserved for
Private Use; and values from 32773 through 65535 are to be assigned
First Come First Served. In all cases, assigned values are to be
registered with IANA.
9. Authors' Addresses
Dave Katz
Juniper Networks
1194 N. Mathilda Ave.
Sunnyvale, CA 94089 USA
Phone: +1 408 745 2000
Email: dkatz@juniper.net
Derek M. Yeung
Procket Networks, Inc.
1100 Cadillac Court
Milpitas, CA 95035 USA
Phone: +1 408 635-7900
Email: myeung@procket.com
Kireeti Kompella
Juniper Networks
1194 N. Mathilda Ave.
Sunnyvale, CA 94089 USA
Phone: +1 408 745 2000
Email: kireeti@juniper.net
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10. IPR Notices
The IETF takes no position regarding the validity or scope of any
intellectual property or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; neither does it represent that it
has made any effort to identify any such rights. Information on the
IETF's procedures with respect to rights in standards-track and
standards-related documentation can be found in BCP-11. Copies of
claims of rights made available for publication and any assurances of
licenses to be made available, or the result of an attempt made to
obtain a general license or permission for the use of such
proprietary rights by implementors or users of this specification can
be obtained from the IETF Secretariat.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights which may cover technology that may be required to practice
this standard. Please address the information to the IETF Executive
Director.
11. Full Copyright Notice
Copyright (C) The Internet Society (2002). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implmentation may be prepared, copied, published and
distributed, in whole or in part, without restriction of any kind,
provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
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HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
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