Network Working Group Dave Katz
Internet Draft Juniper Networks, Inc.
Expiration Date: April 2000 Derek Yeung
TBD
Traffic Engineering Extensions to OSPF
draft-katz-yeung-ospf-traffic-01.txt
Status
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Abstract
This document describes extensions to the OSPF protocol to support
Traffic Engineering, using opaque LSAs.
1. Introduction
This document specifies a method of adding traffic engineering
capabilities to OSPF [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.
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The extensions provide a way of describing the traffic engineering
topology (including bandwidth and administrative constraints). This
topology does not necessarily match the regular routed topology,
though this proposal depends on Network LSAs to describe multiaccess
links.
2. LSA Format
2.1 LSA type
This extension makes use of the Opaque LSA [4].
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.
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 must be zero) 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.
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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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TBD | 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:
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 bytes
(thus a TLV with no value portion would have a length of zero). The
TLV is padded to four-byte alignment; padding is not included in the
length field (so a three byte value would have a length of three, but
the total size of the TLV would be eight bytes). Nested TLVs are
also 32-bit aligned. Unrecognized types are ignored. All types
between 32768 and 65535 are reserved for vendor-specific extensions.
All other undefined type codes are reserved for future assignment by
IANA.
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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.
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.
Only numbered links are described, as traffic engineering is not
supported on unnumbered links.
The Link TLV is type 2, and the length is variable.
The following sub-TLVs are defined:
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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 - Resource class/color (4 octets)
32768-32772 - Reserved for Cisco-specific extensions
Each sub-TLV may occur only once. Unrecognized types are ignored.
All of the defined sub-TLVs are mandatory (though future sub-TLVs may
not necessarily be mandatory.)
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 of
the interface corresponding to this link. Note that at the moment,
only numbered point-to-point links are supported for traffic
engineering.
The Local Interface IP Address sub-TLV is TLV type 3, and is four
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octets in length.
2.5.4 Remote Interface IP Address
The Remote Interface IP Address sub-TLV specifies the IP address of
the neighbor's interface corresponding to this link. This and the
local address are used to discern multiple parallel links between
systems.
The Remote Interface IP Address sub-TLV is TLV type 4, and is four
octets in length.
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.
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).
The units are bytes per second.
The Maximum Reservable Bandwidth sub-TLV is TLV type 7, and is four
octets in length.
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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. 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.
2.5.9 Resource Class/Color
The Resource Class/Color sub-TLV specifies administrative group
membership for this link, in terms of a bit mask. A link that is a
member of multiple groups will have multiple bits set.
The Resource Class/Color 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).
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. Security Considerations
This document raises no new security issues for OSPF.
6. References
[1] Moy, J., "OSPF Version 2", RFC 2328, April 1998.
[2] Awduche, D., et al, "Requirements for Traffic Engineering Over
MPLS," draft-ietf-mpls-traffic-eng-00.txt, work in progress.
[3] Smit, H. and T. Li, "ISIS Extensions for Traffic Engineering,"
draft-ietf-isis-traffic-00.txt, work in progress.
[4] Coltun, R., "The OSPF Opaque LSA Option," RFC 2370, July 1998.
7. Authors' Addresses
Dave Katz
Juniper Networks
385 Ravendale Drive
Mountain View, CA 94043 USA
Phone: +1 650 526 8073
Email: dkatz@juniper.net
Derek M. Yeung
TBD
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