wdiff draft-srisuresh-ospf-te-03.txt draft-srisuresh-ospf-te-04.txt

Network Working Group P. Srisuresh
INTERNET-DRAFT Kuokoa Networks
Expires as of March 16, June 8, 2003 P. Joseph
Force10 Networks
September 16,
December 8, 2002

TE LSAs

OSPF-TE: An experimental extension to extend OSPF for Traffic Engineering
<draft-srisuresh-ospf-te-03.txt>
<draft-srisuresh-ospf-te-04.txt>

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Abstract

OSPF is a link state

This document defines OSPF-TE, an experimental traffic engineering
(TE) extension to the link-state routing protocol used for IP-network
topology discovery and collection and dissemination of link
access metrics. The resulting Link State Database (LSDB) is
used to compute IP address forwarding table based on
shortest-path criteria. Traffic Engineering extensions(OSPF-TE)
outlined in this document OSPF. New TE
LSAs are built on the native OSPF
foundation, utilizing new LSAs, designed specifically for TE.
OSPF-TE sets out to discover TE network topology and perform
collection and dissemination of disseminate TE metrics within the an autonomous
System (AS) - intra-area as well as inter-area. An Autonomous
System may consist of TE network.
This results in and non-TE nodes. Non-TE nodes are
uneffected by the generation of an independent TE-LSDB, that
would permit computation distribution of TE circuit paths. Unlike LSAs. A stand-alone TE Link
State Database (TE-LSDB), separate from the native OSPF link metrics, TE metrics can be rapidly changing and
varied across different elements of LSDB, is
generated for the network. computation of TE circuit
paths are computed using varied TE criteria, often different
from the shortest-path, to route traffic around congestion paths. Principal motivations to designing the OSPF-TE over
[OPQLSA-TE] is
also extendible to non-packet networks such as SONET/TDM and
optical networks. A transition path is provided for vendors those
currently using [OPQLSA-TE] and wish to adapt the OSPF-TE are outlined in separate
sections within the document. OSPF-TE provides a single unified
mechanism for traffic engineering across packet and non-packet
networks, and may be adapted for a peer networking model. OSPF-TE.

Table of Contents

1. Introduction ................................................3
2. Traffic Engineering .........................................4 Principles of traffic engineering ...........................3
3. Terminology .................................................5
3.1. OSPF-TE TE node ...........................................5 ................................................5
3.2. Native OSPF node .......................................5 TE link ................................................5
3.3. TE nodes vs. native(non-TE) nodes ......................6 circuit path ........................................5
3.4. TE links vs. native(non-TE) links ......................6 OSPF-TE node ...........................................6
3.5. Packet-TE network vs. non-packet-TE TE control network ............6 .....................................6
3.6. TE topology vs. non-TE topology ........................6 network (TE topology) ...............................6
3.7. TLV ....................................................7 Packet-TE network ......................................6
3.8. Non-packet-TE network ..................................6
3.9. Native (non-TE) node ...................................7
3.10. Native (non-TE) link ..................................7
3.11. Non-TE network (Non-TE topology) ......................7
3.12. Peer network (combination network) ....................7
3.13. LSP ...................................................7
3.14. LSA ...................................................7
3.14. LSDB ..................................................7
3.15. CSPF ..................................................7
3.16. TLV ...................................................8
3.17. Router-TE TLVs .........................................7
3.9. ........................................8
3.18. Link-TE TLVs ...........................................7 ..........................................8
4. Motivations to designing behind the design of OSPF-TE using TE-LSAs ..........7 ....................8
4.1. Clean Scalable design - TE-LSDB, independent of the native LSDB .7 ........................................9
4.2. Extendible Coexistent design - based on the OSPF foundation .......8 ......................................9
4.3. Scalable design - TE-AS may be sub-divided into areas ..9 Efficient in flooding reach ............................9
4.4. Unified Ability to reserve TE-exclusive links .................10
4.5. Extendible design - .....................................10
4.6. Unified for packet and non-packet networks ....9
4.5. Efficient design - in LSA content and flooding reach ..10
4.6. SLA enforceable TE network can coexist with IP network 10 ............11
4.7. Right Framework for future OSPF extensibility .........11
4.8. Network scenarios Networks benefiting from the OSPF-TE design ..12
4.8.1. IP providers transitioning to TE services ......12
4.8.2. Providers offering Best-effort IP & TE services.12
4.8.3. Multi-area networks ............................12
4.8.4. Non-packet and Peer-networking models ..........12 ...........11
5. OSPF-TE solution, assumptions and limitations ..............13 solution overview ..................................12
5.1. OSPF-TE Solution ......................................14 ......................................12
5.2. Assumptions ...........................................16
5.3. Limitations ...........................................16 ...........................................13
6. Transition strategy for implementations using Opaque LSAs ..16 to OSPF-TE transition strategy .................14
7. OSPF-TE router adjacency - TE topology discovery ...........14
7.1. The OSPF Options field .....................................16
8. Bringing up TE adjacencies; TE vs. Non-TE topologies .......17
8.1. ................................15
7.2. The Hello Protocol ....................................17
8.2. ....................................15
7.3. Flooding and the Synchronization of Databases .........18
8.3. .........16
7.4. The Designated Router .................................19
8.4. .................................16
7.5. The Backup Designated Router ..........................19
8.5. ..........................16
7.6. The graph of adjacencies ..............................19
9. ..............................17
8. TE LSAs ....................................................20
9.1. - Packet network ...................................18
8.1. TE-Router LSA (0x81) ..................................22
9.1.1. Router-TE flags - TE capabilities of the router.24
9.1.2. Router-TE TLVs .................................25
9.1.3. Link-TE options - TE capabilities of a TE-link .26
9.1.4. Link-TE TLVs ...................................26
9.2. ..................................19
8.2. TE-incremental-link-Update LSA (0x8d) .................27
9.3. .................26
8.3. TE-Circuit-paths LSA (0x8C) ...........................29
9.4. ...........................27
8.4. TE-Summary LSAs .......................................31
9.4.1. TE-Summary Network LSA (0x83) ..................31
9.4.2. TE-Summary router LSA (0x84) ...................32
9.5. .......................................30
8.5. TE-AS-external LSAs (0x85) ............................34
9.6. ............................33
9. TE LSAs - Non-packet network ...............................34
9.1. TE-Router LSA (0x81) ..................................34
9.2. Changes to Network LSA ................................35
9.6.1. Positional-Ring type network LSA ...............36
9.7. ................................36
9.3. TE-Router-Proxy LSA (0x8e) ............................36
9.8. Others ................................................37
10. Abstract topology representation with TE support ...........37
11. Changes to Data structures in OSPF-TE routers ..............39 ..............40
11.1. Changes to Router data structure .....................39 .....................40
11.2. Two set of Neighbors .................................39 .................................40
11.3. Changes to Interface data structure ..................39 ..................40
12. IANA Considerations ........................................40 ........................................41
12.1. TE-compliant-SPF routers Multicast address allocation 40 TE LSA type values ...................................41
12.2. New TE-LSA Types .....................................40
12.3. New TLVs (Router-TE and Link-TE TLVs) ................40
12.3.1. TE-selection-Criteria TLV (Tag ID = 1) .......40
12.3.2. MPLS-Signaling protocol TLV (Tag ID = 3) .....40
12.3.3. Constraint-SPF algorithms-Support TE TLV (Tag ID=4)
12.3.4. SRLG-TLV (Tag ID = 0x81) .....................40
12.3.5. BW-TLV (Tag ID = 0x82) .......................41
12.3.6. CO-TLV (Tag ID = ox83) .......................41 tag values ....................................42
13. Acknowledgements ...........................................41 ...........................................42
14. Security Considerations ....................................41 ....................................42
15. Normative References .......................................44
16. Informative References .....................................................41 .....................................44

1. Introduction

There is substantial industry experience with deploying OSPF link
state routing protocol. That makes OSPF a good candidate to adapt
for

This document defines OSPF-TE, an experimental traffic engineering purposes. The dynamic discovery of network
topology, link access metrics, flooding algorithm and
(TE) extension to the
hierarchical organization of areas can all be used effectively in
creating and tearing traffic links on demand. link-state routing protocol OSPF. The intent
objective of OSPF-TE is to discover TE network topology and the
disseminate TE metrics
of the nodes and links in within an autonomous system(AS). A
stand-alone TE Link State Database (TE-LSDB), different from
the network.

The objective of traffic engineering native OSPF LSDB, is created to set up circuit path(s)
across a pair facilitate computation of nodes or links, as the case may be, so as TE
circuit paths. Algorithms to
forward traffic of a certain forwarding equivalency class. Circuit
emulation in a packet network is accomplished by each MPLS
intermediary node performing label swapping. Whereas, compute TE circuit
emulation in a TDM or Fiber cross-connect network paths is accomplished
by configuring the switch fabric in each intermediary node to do
the appropriate switching (TDM, fiber or Lamda) for the duration
of however
not the circuit.

The objective of this document is not how to set up traffic circuits,
but rather provide the necessary TE parameters for the nodes and
links that constitute the TE topology. Unlike the native OSPF, document.

OSPF-TE will be used to build circuit paths, meeting certain TE
criteria. The only requirement is that end-nodes and/or end-links of
a circuit be identifiable with an IP address.

The approach suggested in this document is different from the Opaque-LSA-based approach design outlined
in [OPQLSA-TE]. Section 4 describes the motivations behind designing the
design of OSPF-TE. Section 6 outlines a strategy to transition
Opaque-LSA based implementations to adapt OSPF-TE.

Those interested in TE extensions for the OSPF-TE outlined here. packet networks only
may skip section 9.0.

2. Traffic Principles of traffic engineering overview

The objective of traffic engineering is to set up circuit
path(s) between a pair of nodes or links and to forward traffic
of a certain forwarding equivalency class through the circuit
path. Only the unicast circuit paths are considered here.
Multicast variations are out of scope for this document.

A traffic engineered circuit path may be identified by the
tuple of (Forwarding Equivalency Class, TE parameters for the
circuit, Origin Node/Link, Destination node/Link).

The

Forwarding Equivalency Class(FEC) Class (FEC) is a grouping of traffic
that is forwarded in the same manner by a node. A FEC may be constituted of
classified based on a number of criteria such as (a) follows.
a) Traffic arriving on a specific interface,
(b)
b) Traffic arriving at a certain time of day,
c) Traffic meeting a certain classification criteria
(ex: based on a match of the fields in the IP and
transport headers), (c)
d) Traffic in a certain priority class, (d)
e) Traffic arriving on a specific set of TDM (STS) circuits
on an interface, (e)
f) Traffic arriving on a certain
wave-length wavelength of an interface, (f) Traffic arriving at a certain time
of day, and so on. A FEC may be constituted as a combination of one
or more of the above criteria. interface

Discerning traffic based on the FEC criteria is a mandatory requirement on for
Label Edge Routers (LERs).
Traffic content is transparent to the Intermediate The intermediate Label Switched Routers (LSRs), once a circuit is formed.
(LSRs) are transparent to the traffic content. LSRs are simply merely
responsible for keeping the circuit in-tact for the lifetime of the
circuit(s). As such, this circuit
lifetime. This document will not address defining FEC criteria,
or the mapping of a FEC to circuit, or the associated signaling to setup
set up circuits. [MPLS-TE] and [GMPLS-TE] address the FEC criteria. Whereas,
[RSVP-TE] and [CR-LDP] address
different types of signaling protocols. protocols to set up
circuits.

This document is concerned with the collection of TE parameters metrics for
all the TE enforceable nodes and links within an autonomous system.
TE parameters metrics for a node may include the following.
a) ability Ability to perform traffic prioritization,
b) ability Ability to provision bandwidth on interfaces,
c) support Support for zero
or more CSPF Constrained Shortest Path First (CSPF)
algorithms,
d) support Support for a specific certain TE-Circuit switch type,
e) support Support for a certain type of automatic protection
switching and so forth.

TE parameters metrics for a link may include the following.
a) available Available bandwidth,
b) reliability Reliability of the link,
c) color Color assigned to the link,
d) cost Cost of bandwidth usage on the link, and
e) membership Membership to a Shared Risk Link Group (SRLG) and so forth.

Only the unicast paths

A number of CSPF algorithms may be used to dynamically set up
TE circuit paths are considered here. Multicast
variations are currently considered out of scope in a TE network.

As for this document.
The requirement is that origin node/link and destination node/link, the originating as well as
and the terminating entities of a TE circuit path are identifiable
by their IP address. addresses.

3. Terminology

Definitions for majority of the terms used in this document with
regard to the context of the OSPF protocol may be
found in [OSPF-V2]. MPLS and traffic engineering terms may be found
in [MPLS-ARCH]. RSVP-TE and CR-LDP signaling specific terms may be
found in [RSVP-TE] and [CR-LDP] respectively.

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALLNOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in
this document are to be interpreted as described in RFC 2119. [IETF-STD].

Below are definitions for the terms used within this document.

3.1. OSPF-TE TE node

This

TE-Node is a router that supports the OSPF-TE described in this
document. At least one of the attached links for the node
supports IP packet termination and runs the OSPF-TE protocol.

An OSPF-TE node supports native OSPF as well as in the OSPF-TE.

3.2. Native OSPF node traffic engineered (TE) network. A native OSPF node is an OSPF router that does not support
the TE extensions described in this document or does not have
TE-node has a TE link minimum of one TE-link attached to it. A Native OSPF node forwards IP
traffic, using the shortest-path forwarding algorithm.

A native OSPF Associated
with each TE node may be enhanced to be an OSPF-TE node. An
autonomous system (AS) could be constituted of is a combination set of native-OSPF and OSPF-TE nodes.

3.3. supported TE nodes vs. native(non-TE) nodes metrics. A TE-Node is an intermediate or edge TE node taking part
may also participate in the
traffic engineered (TE) network. A TE-circuit is constituted of a series of TE nodes connected to each other through TE links. native IP network.

In a SONET/TDM network or a photonic cross-connect network, a TE node is
not required to support OSPF-TE. be an OSPF-TE router. An external OSPF-TE node router
may represent act as proxy for the TE node nodes that cannot be routers
themselves.

3.2. TE link

TE Link is a network attachment point to a TE-node and is
intended for protocol processing.

A native (or non-TE) node traffic engineering use. Associated with each
TE link is an IP router capable a set of IP packet
forwarding, does not have supported TE metrics. A TE link attachments and does not may also
optionally carry native IP traffic.

Of the various links attached to a TE-node, only the links that
take part in a traffic engineered network are called the TE network.

3.4.
links.

3.3. TE links vs. native(non-TE) links circuit path

A TE Link circuit path is a network attachment that supports traffic
engineering. A TE-circuit is constituted of uni-directional data path, defined by a series
list of TE nodes connected to each other through TE links. A native (or non-TE) link is one that
TE circuit path is used for IP packet
traversal. A link may also often referred merely as a circuit path
or a circuit.

For the purposes of OSPF-TE, the originating and terminating
entities of a TE circuit path must be configured identifiable by their
IP addresses. As a general rule, all nodes and links party to a
Traffic Engineered network should be pure uniquely identifiable by an
IP address.

3.4. OSPF-TE node

An OSPF-TE node is a TE link or node that runs the OSPF routing protocol
and the OSPF-TE extensions described in this document.

An autonomous system (AS) may be constituted of a combination of
native link and OSPF-TE nodes.

3.5. TE Control network

The IP network used by the OSPF-TE nodes for OSPF-TE
communication is referred as the TE control network or simply
the control network. The control network can be independent of
the TE data network.

3.6. TE network (TE topology)

A TE network is a both.

3.5. Packet-TE network vs. non-packet-TE of connected TE-nodes and TE-links
for the purpose of setting up one or more TE circuit paths.
The terms TE network, TE data network and TE topology are
used synonymously throughout the document.

3.7. Packet-TE network

A packet-TE network is one a TE network in which TE-circuit emulation the nodes switch
MPLS packets. An MPLS packet is
accomplished by each defined in [MPLS-TE] as a
packet with an MPLS header, followed by data octets. The
intermediary node performing node(s) of a circuit path in a packet-TE network
perform MPLS label swapping on to emulate the circuit.

Unless specified otherwise, the term packet data. network is used
throughout the document to refer a packet-TE network.

3.8. Non-packet-TE network, network

A non-packet-TE network is TE-network in which the nodes
switch non-packet entities such as SONET/TDM an STS time slot, a Lambda
wavelength or simply an interface.

SONET/TDM and Fiber cross-connect network is one in which TE-circuit networks are examples of
non-packet-TE networks. Circuit emulation in these networks
is accomplished by configuring the switch fabric in each
intermediary node to do the appropriate switching (TDM, intermediary
nodes (based on TDM time slot, fiber interface or Lamda) for Lambda).

Unless specified otherwise, the duration term non-packet network is
used throughout the document to refer a non-packet-TE
network.

3.9. Native (non-TE) node

A native or non-TE node is an OSPF router capable of IP packet
forwarding and does not take part in a TE network. A native
OSPF node forwards IP traffic using the shortest-path
forwarding algorithm and does not run the circuit.

In either case, OSPF-TE can only be enabled on interfaces
supporting extensions.

3.10. Native (non-TE) link

A native (or non-TE) link is a network attachment to a TE or
non-TE node used for IP packet termination. Interfaces supporting traversal.

3.11. non-TE network (Non-TE topology)

A non-TE network refers to an OSPF
and/or OSPF-TE constitute network that does not
support TE. Non-TE network, native-OSPF network and non-TE
topology are used synonymously throughout the OSPF control network. The OSPF
control document.

3.12. Peer network can be independent (combination network)

A peer network is a network that is constituted of packet
and non-packet networks combined. In a peer network, a TE
node could potentially support TE links for the packet as
well as non-packet data.

OSPF-TE is usable within a packet network or a non-packet
data
network or a peer network, which is a combination of the two.

3.13. LSP

LSP stands for "Label Switched Path". LSP is a TE circuit path
in a packet network.

3.6. The terms LSP and TE circuit path are
used synonymously in the context of packet networks.

3.14. LSA

LSA stands for OSPF "Link State Advertisement".

3.15. LSDB

LSDB stands for "LSA Database". LSDB is a representation of the
topology vs. non-TE topology of a network. A TE topology is native LSDB, constituted of native OSPF
LSAs, represents the topology of a set native IP network. TE-LSDB, on
the other hand, is constituted of contiguous TE nodes LSAs and is a representation
of the TE links. Associated with each network topology.

3.16. CSPF

CSPF stands for "Constrained Shortest Path First". Given a TE node
LSDB and link is a set of TE
criteria constraints that may must be supported at any given time. A TE topology
allows circuits satisfied to be overlayed statically or dynamically based
on form a specific TE criteria.

A non-TE topology specifically refers to the network that does not
support TE. Control protocols such as OSPF
circuit path, there may be run on the non-TE
topology. IP forwarding table used several CSPF algorithms to forward IP packets on this
network is built based on obtain a
TE circuit path that meets the control protocol specific algorithm,
such as OSPF shortest-path criteria.

3.7.

3.17. TLV

A TLV stands for an object in the form of Tag-Length-Value. All
TLVs are assumed to be of the following format, unless specified
otherwise. The Tag and length are 16 bits wide each. The length
includes the 4 bytes octets required for Tag and Length specification.
All TLVs described in this document are padded to 32-bit
alignment. Any padding required for alignment will not be a part
of the length field, however. TLVs are used to describe traffic
engineering characteristics of the TE nodes, TE links and TE circuit
paths.

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tag | Length (4 or more) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value .... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| .... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

3.8.

3.18. Router-TE TLVs

TLVs used to describe the TE capabilities of a TE-node.

3.9.

3.19. Link-TE TLVs

TLVs used to describe the TE capabilities of a TE-link.

4. Motivations to designing the OSPF-TE using TE-LSAs

The motivation behind designing the design of OSPF-TE using TE-LSAs is

There are several motivations that lead to the approach design of OSPF-TE.
OSPF-TE is clean, extendible, scalable, unified,
efficient, coexistent and SLA enforceable. efficient in flooding reach.
The approach also provides
the right framework for future OSPF extensibility. Each of
these motivations is are explained in detail in the following
subsections.

The Also listed in the last subsection lists are network
scenarios that benefit from the TE-LSA OSPF-TE design.

4.1. Clean Scalable design - TE-LSDB, independent of the native LSDB
OSPF-TE using TE LSAs

Area level abstraction provides a clean separation of Link State
Data Bases (LSDB) between native (SPF-based) and TE networks.
The OSPF-TE dynamically discovers TE network topology and the
associated TE metrics of the nodes and links in the TE network.
OSPF-TE design is based on the tried and tested OSPF paradigm.
As such, it inherits all the benefits of the OSPF, present and
future.

With OSPF-TE, native OSPF nodes will keep just the native OSPF
link state database. The OSPF-TE nodes will keep the native as
well as the TE LSDB. In the case, where the network is used
only scaling necessary for Traffic engineering purposes, the native-LSDB
describes the control topology.

In the Opaque-LSA-based TE scheme([OPQLSA-TE]), the TE-LSDB built
using opaque LSAs refers the native LSDB to build the TE topology.
Further, the LSDB has no knowledge of the TE capabilities of the
routers. Point-to-point links are the only type of links that can
form a TE network. It is apparent that [OPQLSA-TE] is a new
protocol in itself within the constraints of an Opaque-LSA and is
not tailored to benefit from the tried and tested native-OSPF.

4.2. Extendible design - based on the OSPF foundation

TE LSAs are extendible, just as the native OSPF on which large
autonomous system (AS). OSPF-TE
is founded. [OPQLSA-TE], on the other hand, is not extendible
and is constrained by the Opaque LSA on which it is founded.

For example, Opaque LSAs are not suited to advertising summary
LSAs along a restricted flooding scope (as with TE-Summary
network LSA). Opaque LSAs are also not suited to advertising
incremental TLV changes. A change in any TLV of a TE-link will
mandate the entire Opaque-LSA (with all the TLVs included) to be
transmitted. TE-incremental-link-update LSA, on the other hand,
is capable of advertising just the delta TLVs. Opaque LSAs
are also not extendible to support advertisement of TLVs for
non-members of the OSPF control network. This is a necessity
for certain non-packet networks such as a SONET/TDM network. In
a SONET/TDM network, data-path topology often differs from
its OSPF control network counterpart. TE-Router-Proxy-LSA
(section 9.7) permits advertising LSAs for non-members via
a proxy node that is a member of the control network.

Lastly, the expressibility of data in an Opaque LSA is strictly
restricted to being in the form of TLVs and sub-TLVs, some
mandatorily required and some positionally dependent in the
TLV sequence allows for interpretation.

4.3. Scalable design - TE-AS may be sub-divided into areas

OSPF-TE using TE LSAs inherits the hierarchical independent area organization
used within native-OSPF. Without revealing the nodes and
characteristics of the attached links within a TE-area, the
TE-Summary network LSA (refer section 9.4) advertises
abstractions for the
reachability of TE networks within an area to the areas outside
in the same AS.

Providing area level abstraction and having the abstraction be
distinct for native topologies. The TE and native topologies is a necessity for
inter-area communication. When the topologies are separate, the
area border routers can will advertise different summary LSAs to TE
and non-TE routers. For example, a native Area Border router (ABR)
simply announces the shortest path network summary LSAs (LSA
type 3) for nodes outside the area. A TE-ABR, on the other hand,
would use TE-summary network LSA to advertise network Reachability
information - not aggregated path metric as required Readers may refer section 10 for a native
OSPF LSDB. Clearly, the data content and flooding scope should be
different for
topological view of the TE nodes. The flooding boundary for TE-summary
LSAs would be (AS - OriginatingArea - StubAreas - NSSAs).

Opaque-LSA-based TE scheme([OPQLSA-TE]) is restricted for use
within AS from an area and is not applicable for flooding across areas.
As-wide scope Opaque LSAs (Type 11 LSAs) will be unable to restrict
flooding OSPF-TE node in its own originating an area.

4.4. Unified

4.2. Coexistent design - for packet

OSPF-TE regards an AS as constituted of a TE and non-packet non-TE networks

OSPF-TE uses
coexisting within the same set of TE LSAs for disseminating bounds. OSPF-TE dynamically discovers
TE
characteristics - irrespective of whether topology and the network is a packet
network or a non-packet network or a combination associated TE metrics of both. Only the TLVs used to describe the characteristics will vary. Each TE
node will be required to advertise its own TE capabilities nodes and
that links
within, just as the native OSPF does in a non-TE network. An
independent TE-LSDB, representative of the attached TE links.

In topology is
generated as a peer networking TE model, result. A stand-alone TE-LSDB allows for speedy
searches through the TE nodes are heterogeneous
and have different TE characteristics. As such, database.

In [OPQLSA-TE], the signaling
protocols will need TE-LSDB is derived from the TE characteristics combination of all nodes
opaque LSAs and
attached links so they can signal the nodes to formulate TE
circuits across heterogeneous nodes. native LSDB. The underlying control
protocol must be capable TE-LSDB derived has no
knowledge of providing a unified LSDB for all
nodes in the network. OSPF-TE clearly meets this requirement.

Opaque-LSA-based TE scheme([OPQLSA-TE]) is limited in scope for
packet networks. Extensions ([OPQLSA-GMPLS]) are underway to
support GMPLS links within opaque LSAs. However, neither

[OPQLSA-TE] nor [OPQLSA-GMPLS] is sufficient by itself or when
combined for use within a peer networking model with heterogeneous
nodes. Neither capabilities of the Opaque LSA based extensions have provision
to distinguish between routers in the various nodes and link attachments that
are different from point-to-point connections. SONET specific
ring topologies and packet network specific LAN and other mesh
topologies are not permitted.

4.5. network.

4.3. Efficient design - in LSA content and flooding reach

OSPF-TE is capable of identifying the boundaries of a TE topology
and limits the flooding of TE LSAs to only the TE-nodes. Nodes
that do not have TE link attachments Non-TE
nodes are not bombarded with TE
specific LSAs. This is a useful
characteristic for networks supporting native and TE traffic in
the same connected network.

A subset of the TE metrics may be prone to rapid change, while
others remain largely unchanged. Changes in TE metrics must be
communicated at the earliest throughout the network to ensure
that the TE-LSDB is up-to-date within the network. As a general
rule, a TE network is likely to generate significantly more
control traffic than a native OSPF network. The excess traffic
is almost directly proportional to the rate at which TE circuits
are set up and torn down within the TE network. The TE database
synchronization should occur much quicker compared to the
aggregate circuit set up and tear-down rates.
TE-Incremental-Link-update LSA (section 8.2) permits advertising
a subset of the link metrics.

The more frequent and wider the flooding scope, frequency, the larger
the number of retransmissions and acknowledgements. The same
information (needed or not) may reach a router through multiple
links. Even if the router did not forward the information past
the node, it would still have to send acknowledgements across
all the various links on which the LSAs tried to converge.
Clearly, it
It is not desirable undesirable to flood LSAs to nodes that do not
require it. This can be a considerable impediment to non-TE nodes in a network that is constituted of native and TE nodes.

Opaque-LSA-based TE scheme([OPQLSA-TE]) makes no distinction
between with TE and native OSPF nodes as far as LSA flooding is
concerned. It is possible information.

[OPQLSA-TE] uses Opaque LSAs for the native OSPF nodes to silently
ignore the unsupported advertising TE information.
Opaque LSAs or add knobs reach all nodes within
implementation to decide whether or not a certain opaque LSA
mandates dijkstra SPF recomputation. In any case, unintended
LSAs are disruptive and can be the cause of a large number of
acknowledgements and retransmissions.

TE metrics in a network could be rapidly changing. Only a subset
of the metrics may be prone to rapid change, while others remain
largely unchanged. Changes must be communicated at the earliest
throughout the network to ensure that the TE-LSDB is up-to-date.
TE-Incremental-Link-update LSA (section 9.2) permits advertising
only a subset of the link metrics - TE-nodes and not the entire router-LSA
all over.
non-TE nodes alike. [OPQLSA-TE] also does not have provision
to advertise just the TLVs that changed. A change in any TLV
of a TE-link will mandate the entire LSA to be transmitted. This is clearly a
serious shortcoming in the protocol.

4.6. SLA enforceable TE network can coexist with IP network

4.4. Ability to reserve TE-exclusive links

OSPF-TE is designed to draw distinction between links that
support TE traffic TE-links and links that support native best-effort
IP traffic. This flexibility to configure links as appropriate
for a service, permits enforceability of service level
agreements (SLAs).
non-TE links. A TE link, configured to support TE traffic
alone
alone, will not permit native best-effort IP traffic on the link.
This permits TE enforceability on the TE links.

When links of a TE-topology do not overlap the links of a
native IP network, OSPF-TE allows for virtual isolation of
the two networks. Best-effort IP transit network and
constraint based TE network often have different SLA requirements and hence different billing
models. service
requirements. Keeping the two networks physically isolated
will enable SLA enforceability, but can be expensive. Combining
the two networks into a single physically connected network
will bring economies of scale, if the SLA service enforceability
can be retained.
When the links of a TE-network LSDB do

[OPQLSA-TE] does not overlap support the links
of a native LSDB, such a virtual isolation of networks and
hence SLA enforceability becomes possible.

Opaque-LSA-based ability to isolate best-
effort IP traffic from TE scheme([OPQLSA-TE]) is inherently not capable
of having two virtual networks in traffic on a single physically connected
network. link. All point-to-point links in a packet network are
subject to best-effort IP traffic, irrespective of whether a link is
usable for TE traffic or not. In order to ensure that TE links are
not cannibalized by best-effort traffic, the network provider will
simply have to restrict best-effort traffic from entering the
network. This is a severe limitation and is a direct result of
not having LSDB isolation. When TE and native topologies
are not separated (as is the case with Opaque-LSAs), a native traffic. An OSPF
node router could be utilizing
potentially select a TE link as to be its least cost link, thereby
stressing the TE link and
inundate the link with best-effort IP traffic, thereby
rendering the TE link ineffective unusable for TE purposes.

4.7. Right Framework for future OSPF extensibility

4.5. Extendible design

OSPF-TE design provides the right framework for future OSPF
extensions is based on independent service provider needs. The
framework essentially calls for building independent service
specific LSDBs. Each such LSDB will consist of service specific
metrics of the tried and tested OSPF paradigm,
and inherits all resources within the service-specific topology.
The TE-LSDB permits TLV scalability as well benefits of the OSPF, present and future.
TE-LSAs are extendible, just as the ability
to perform fast searches through native OSPF on which OSPF-TE
is founded.

[OPQLSA-TE], on the database. Just as other hand, is constrained by the
TE-LSDB may be used for MPLS TE application, a different type
of LSDB may be used for a different type semantics
of application across the same physically connected IP network. E.g., one can derive
QOS based IP forwarding Opaque LSA on which it is founded. The content within an IP network.

Limiting
Opaque LSA is restricted to being in the form of TLVs and
sub-TLVs, some of which are mandatory and some of which are
positionally dependent in the TLV sequence for proper
interpretation. Opaque LSAs are also restrictive when the flooding
scope for the content is required to be different from the scope
of service specific LSAs within the
service specific topology eliminates opaque LSA contamination between
virtual service itself.

4.6. Unified for packet and non-packet networks of

OSPF-TE is usable within a single physically connected packet network or a non-packet
network or a combination peer network. Using service specific LSAs provides flexibility in
LSA content

Signaling protocols such as RSVP and flooding scope.

Opaque-LSA-based LDP work the same across
packet and non-packet networks. Signaling protocols merely need
the TE scheme([OPQLSA-TE]) works best when a single
type characteristics of service is assumed for a single physically connected
network. As such, multiple disparate networks nodes and links so they can function
running various flavors signal the
nodes to formulate TE circuit paths. In a peer network, the
underlying control protocol must be capable of OSPF. [OSPF-v2] providing a
unified LSDB for native best-effort
IP networks, all TE nodes (nodes with packet-TE links as well
as non-packet-TE links) in the network. OSPF-TE meets this
requirement.

[OPQLSA-TE] is limited in scope for packet networks and networks. An
independent [OPQLSA-GMPLS]
for is required to support GMPLS links in
a non-packet networks.

4.8. Network scenarios network. Neither of the Opaque LSA based extensions
have provision to distinguish between node types.

4.7. Networks benefiting from the OSPF-TE design

Many real-world scenarios networks are better served by the new-TE-LSAs
scheme. Here are a few examples.

4.8.1.

4.7.1. IP providers transitioning to provide TE services

Providers needing to support MPLS based TE in their IP network
may choose to transition gradually. Perhaps, add new TE links
or convert existing links into TE links within an area first
and progressively advance to offer in the entire AS.

Not all routers will support TE extensions at the same time
during the migration process. Use of TE specific LSAs and their
flooding to OSPF-TE only nodes will allow the vendor to
introduce MPLS TE without destabilizing the existing network.
As such, the
The native OSPF-LSDB will remain undisturbed while newer TE
links are added to the network.

4.8.2.

4.7.2. Providers offering Best-effort-IP & TE services

Providers choosing to offer both best-effort-IP and TE based
packet services simultaneously on the same physically connected
network will benefit from the OSPF-TE design. By maintaining
independent LSDBs for each type of service, TE links are not
cannibalized by the non-TE routers for SPF forwarding. Unlike
the [OPQLSA-TE] scheme, OSPF-TE provides the framework for SLA
enforcement.

4.8.3. Multi-area
cannibalized.

4.7.3. Large TE networks

The OSPF-TE design parallels is advantageous in large TE networks that
require the tried and tested native-OSPF
design. Unlike [OPQLSA-TE], OSPF-TE scales naturally AS to multi-area
networks.

4.8.4. be sub-divided into multiple areas.

4.7.4. Non-packet networks and Peer-networking models Peer networks

OSPF-TE is also the only scheme that can right choice for vendors opting for a
stable, well-founded protocol for their non-IP TE networks.
OSPF-TE is uniquely qualified to support the following network
attachments For a in non-Packet TE network. networks.
(a) "Positional-Ring" type network LSA and
(b) Router Proxying - allowing a router to advertise on behalf
of other nodes (that are not Packet/OSPF capable).

Opaque LSA based extensions ([OPQLSA-TE], [OPQLSA-GMPLS]) are not
suited to distinguish the heterogeneous nodes in a peer-connected
network. Opaque-LSA based extensions are also not suited to support
link attachments that are different from point-to-point connections.

5. OSPF-TE solution, assumptions and limitations solution overview

5.1. OSPF-TE Solution

The OSPF-TE uses

A new TE flag is introduced within the OSPF options flag as a means field to determine the
to enable discovery of TE topology. New Section 8.0 describes the
semantics of the TE flag. TE LSAs are designed to generate an independent
TE-service tailored LSDB. Sections 8.0 and for use by the
OSPF-TE nodes. Section 9.0 describe describes the TE
extensions LSAs in detail.
Changes required of the OSPF data structures in order to support
OSPF-TE are described in section 11.0. The OSPF-TE design is based on the tried and tested OSPF
paradigm. With TE-LSDB, you have the advantages of retaining the
scalability of TLV's and the ability to run fast searches through
the database.

With the new TE-LSA scheme, an OSPF-TE node will have two types
of Link state databases (LSDB). A native LSDB that describes the
native control topology and a TE-LSDB that describes the TE
topology. Shortest-Path-First algorithm will be used to forward
IP packets along the native control network. OSPF neighbors data
structure will be used for flooding along the control topology.

The TE-LSDB is constituted only of TE nodes and TE links. A variety
of CSPF algorithms may be used to dynamically setup TE circuit
paths along the TE network. A new TE-neighbors data
structure will be used to flood TE LSAs along the TE-only topology. Clearly, the
the TE nodes will need the control (non-TE) network for OSPF
communication. The control network may also be used for pinging TE-topology.

An OSPF-TE nodes and performing any debug and monitoring tasks on
the nodes. However, node will have the ability to make distinction between
TE native LSDB and non-TE topologies, allows the bandwidth on TE links to be
strictly SLA enforceable, even as a TE link is packet-capable.
The actual characteristics of the TE-link are irrelevant from TE-LSDB,
A native OSPF node will have just the
OPSF-TE perspective. As such, that allows for packet and non-packet
networks to operate in peer mode. native LSDB.
Consider the following network where some OSPF area constituted of the routers OSPF-TE and links
native OSPF routers. Nodes RT1, RT2, RT3 and RT6 are OSPF-TE
routers with TE enabled and others non-TE link attachments. Nodes RT4 and RT5
are native OSPF routers and with no TE links. All
nodes in When the network belong to LSA database
is synchronized, all nodes will share the same OSPF area. native LSDB
OSPF-TE nodes alone will have the additional TE-LSDB.

+---+
| |--------------------------------------+
|RT6|\\ |
+---+ \\ |
|| \\ |
|| \\ |
|| \\ |
|| +---+ |
|| | |----------------+ |
|| |RT1|\\ | |
|| +---+ \\ | |
|| //| \\ | |
|| // | \\ | |
|| // | \\ | |
+---+ // | \\ +---+ |
|RT2|// | \\|RT3|------+
| |----------|----------------| |
+---+ | +---+
| |
| |
| |
+---+ +---+
|RT5|--------------|RT4|
+---+ +---+
Legend:
-- Native(non-TE) network link
| Native(non-TE) network link
\\ TE network link
|| TE network link

Figure 6: A (TE + native) OSPF network topology

5.2. Assumptions

OSPF-TE is an extension to the above network, TE and native OSPF Link State Data bases
(LSDB) would have been synchronized within the area along the
following nodes.

Native OSPF LSDB nodes TE-LSDB nodes
---------------------- -------------
RT1, RT2, RT3. RT4, RT5, RT6 RT1, RT2, RT3, RT6

Nodes such as RT1 will have two LSDBs, a native LSDB and a TE-LSDB
to reach native protocol and TE networks. The TE LSA updates will does not impact
non-TE nodes RT4 and RT5.

5.2. Assumptions
mandate changes to the existing OSPF. OSPF-TE design makes the
following assumptions.

1. An OSPF-TE node with links in an OSPF area will need to establish router adjacency with
at least one other neighboring OSPF-TE node in the area in order for the
router's database TE-database to be synchronized with other routers in within the area.
Failing this, the OSPF router will not be in the TE
calculations of other TE routers in the area. Refer [FLOOD-OPT] for flooding
optimizations.

2. Unlike

It is the native OSPF, responsibility of the network administrator(s) to
ensure connectedness of the TE network. Otherwise, there can
be disjoint TE topologies within a network.

2. OSPF-TE nodes must be capable of advertising advertise the link state of interfaces that its TE-links.
TE-links are not capable of handling obligated to support native IP
packet data. As such, the traffic.
Hence, an OSPF-TE protocol node cannot be required to synchronize
its link-state database with neighbors across on all its links. It
The only requirement is sufficient to synchronize link-state
database in an area, across a subset of the IP termination
links. Yet, have the TE LSDB (LSA database) should be synchronized
across all OSPF-TE nodes within an area.

All nodes and interfaces described by the TE LSAs will be
present in the TE topology database (a.k.a. TE LSDB). area. Refer [FLOOD-OPT] for
flooding optimizations.

3. A link in a packet network can may be designated as a TE-link or
a native-IP link or both. There may be different ways by which to use
a link for TE and non-TE traffic. For example, a link may be used for
both types of traffic and satisfy the TE SLA
requirements, and non-TE traffic, so long as the link is
under-subscribed in bandwidth for TE (say, traffic - say, 50% of
the link capacity is being used). Once the
TE capacity requirement exceeds the set mark (say, the 50%
mark), the link may be removed from the non-TE topology.

4. This document does not require any changes to the existing OSPF
LSDB implementation. Rather, it suggests the use of another
database, the TE-LSDB, comprised of the TE LSAs, aside for TE purposes.

5. As a general rule, all nodes and links that may be party
to a traffic.

4. Non-packet TE circuit should be uniquely identifiable by an IP
address. As for router ID, a separate loopback IP address
for the router, independent of the links attached, is
recommended.

6. The assumption about to be stated is principally meant for
non-packet networks such as a SONET TDM network. In non-packet
networks, each IP subnet on a TE-configurable network sub-topologies MUST have a minimum of one node with an interface
running OSPF-TE protocol. For example, a SONET/SDH TDM ring
must have a minimum of one node
(say, a Gateway Network Element) Element(GNE)
running the OSPF protocol in
order to enable TE configuration on all nodes within the ring.

An OSPF-TE node may advertise more than itself and the links
it is directly attached to. It may also advertise other TE
participants and their links, on their behalf.

5.3. Limitations

Below are the limitations of the OSPF-TE.

1. Disjoint TE topologies would have the same problem as an The OSPF-TE node not forming adjacencies with any other node.
The disjoint nodes will not be included in the TE topology
of the rest of the TE routers. It will be the
responsibility of the network administrator(s) to ensure
connectedness advertise on behalf
of all the TE network.

For example, two routers that are physically connected to
the same link (or broadcast network) need not be router
adjacent via the Hello protocol, if in the link is not IP
packet terminated. ring.

6. Transition strategy for implementations using Opaque LSAs to OSPF-TE transition strategy

Below is a strategy to transition implementations using opaque
LSAs to adapt the new TE LSA OSPF-TE scheme in a gradual fashion.

1. Restrict the use of Opaque-LSAs to within an area.

2. Fold in the TE option flag to construct the TE and non-TE topologies in an area, even if
area-wise. By doing this, the topologies cannot be used TE topology for flooding within the area. AS will
be available at area level abstraction.

3. Use TE-Summary LSAs and TE-AS-external-LSAs for inter-area
Communication. Make use of the TE-topology within an area to
summarize the TE networks in the area and advertise the same
to all TE-routers in the backbone. The TE-ABRs on the backbone
area will in-turn advertise these summaries again within their
connected areas.

7. OSPF-TE router adjacency - TE topology discovery

OSPF creates adjacencies between neighboring routers for the purpose
of exchanging routing information. In the following subsections, we
describe modifications to the OSPF options field and the use of
Hello protocol to establish TE capability compliance between
neighboring routers in an area. The capability is used as the basis
to build TE topology.

7.1. The OSPF Options field

A new TE flag is introduced within the options field by this draft
to identify TE extensions to the OSPF. This bit will be used to
distinguish
between routers that support Traffic engineering extensions and
those that do not. OSPF-TE. The OSPF options field
is present in OSPF Hello packets, Database Description packets packets,
and all link state advertisements. The TE bit, however, is a
requirement only for the Hello packets. Use of TE-bit is optional
in Database Description packets or LSAs.

Below is a description of the TE-Bit. Refer [OSPF-V2], [OSPF-NSSA]
and [OPAQUE] for a description of the remaining bits in the
options field.

--------------------------------------
|TE | O | DC | EA | N/P | MC | E | * |
--------------------------------------
The OSPF options field - TE support

TE-Bit: This bit is set to indicate support for Traffic Engineering traffic engineering
extensions to the OSPF. The Hello protocol which is used for
establishing router adjacency and bidirectionality of the
link will use the TE-bit to build adjacencies between two
nodes that are either both TE-compliant or not.
establish OSPF-TE adjacency. Two routers will not become
TE-neighbors unless they agree on the state of the TE-bit.
TE-compliant OSPF extensions are advertised only to the
TE-compliant routers. All other routers may simply ignore
the advertisements.

There is however a caveat with the above use of the last remaining
reserved bit in the options field. OSPF v2 will have no more
reserved bits left for future option extensions. If it is deemed
necessary to leave this bit as is, we could use the OPAQUE-9 LSA (Local (local scope) along
can be used on each interface to communicate the support for
OSPF-TE.

8. Bringing up TE adjacencies; TE vs. Non-TE topologies

OSPF creates adjacencies between neighboring routers for the purpose
of exchanging routing information. In the following subsections, we
describe the use of Hello protocol to establish TE capability
compliance between neighboring routers of an area. Further, the
capability is used as the basis to build a TE vs. non-TE network
topology.

8.1.

7.2. The Hello Protocol

The Hello Protocol is primarily responsible for dynamically
establishing and maintaining neighbor adjacencies. In a TE network,
it may is not be required or possible for all links and neighbors to establish
adjacency using this protocol. The Hello protocol will use the
TE-bit to establish Traffic
Engineering traffic engineering capability (or not) between two
OSPF routers.

For NBMA and broadcast networks, this protocol is responsible for
electing the designated router Designated Router and the backup designated router. Backup Designated Router.

For a TDM ring network, the designated and backup designated
routers may either be preselected (ex: GNE, backup-GNE) or
determined via the same Hello protocol. In any case, routers
supporting the TE option shall be given a higher precedence for
becoming a designated router over those that do not support TE.

8.2. Flooding and the Synchronization of Databases

In OSPF, adjacent routers within an area must synchronize their
databases. However, as observed in [FLOOD-OPT], the requirement
may be stated more concisely that all routers in an area must
converge on the same link state database. To do that, it suffices
to send single copies of LSAs

If deemed necessary to leave the neighboring routers in an
area, rather than send one copy on each of the connected
interfaces. [FLOOD-OPT] describes TE-bit unused in detail how to minimize
flooding (Initial LSDB synchronization as well as the
asynchronous LSA updates) within an area.

With options
field, the OSPF-TE described here, a TE-only network topology is
constructed based on the TE option flag in the Hello packet.
Subsequent to that, TE LSA flooding in an area is limited to
TE-only routers in the area, and do not impact non-TE routers
in the area. A network may be constituted of a combination of
a TE topology and a non-TE (control) topology. Standard IP
packet forwarding and routing protocols are possible along the
control topology.

In the case where some of the neighbors are TE compliant and
others are not, the designated router will exchange different
sets of LSAs with its neighbors. TE LSAs are exchanged only
with the TE neighbors. Native LSAs do not include description
for TE links. As such, native LSAs are exchanged with all
neighbors (TE and non-TE alike) over a shared non-TE link.

Flooding optimization in a TE network is essential
for two reasons. First, the control traffic for a TE network is
likely to be much higher than that of a non-TE network. Flooding
optimizations help to minimize the announcements and the
associated retransmissions and acknowledgements on the network.
Secondly, the TE nodes need to converge at the earliest to keep
up with TE state changes occurring throughout the TE network.

This process of flooding along a TE topology cannot be folded
into the Opaque-LSA based TE scheme ([OPQLSA-TE]), because
Opaque LSAs (say, LSA #10) have a pre-determined flooding
scope. Even as a TE topology is available from the could use of
TE option flag, the TE topology is not usable for flooding
unless a new TE OPAQUE-9 LSA is devised, whose boundaries can be set (local scope)
to
span the TE-only routers in an area.

NOTE, a new All-SPF-TE Multicast address may be used for the
exchange of communicate TE compliant database descriptors.

8.3. capability between two OSPF routers.

7.3. The Designated Router

The Designated Router is elected by the Hello Protocol on broadcast
and NBMA networks. In general, when a router's interface to a
network non-TE link first
becomes functional, it checks to see whether there is currently a
Designated Router for the network. If there is, is one, it accepts that
Designated Router, regardless of its Router Priority, so long as
the current designated router is TE compliant. Otherwise,
the router itself becomes Designated Router if it has the highest
Router Priority on the network and is TE compliant.

Clearly,

TE-compliance (I.e., OSPF-TE) must be implemented on the most robust
routers only,
routers, as they become most likely candidates to take on
additional the role as
designated router.

Alternatively, there can be two sets of designated routers, one for
the TE compliant routers and another for the native OSPF routers
(non-TE compliant).

8.4.

7.4. The Backup Designated Router

The Backup Designated Router is also elected by the Hello
Protocol. Each Hello Packet has a field that specifies the
Backup Designated Router for the network. Once again, TE-compliance
must be weighed in conjunction with router priority in determining electing
the backup designated router.

Alternatively, there can be two sets of backup designated routers,
one for the TE compliant routers and another for the native OSPF
routers (non-TE compliant).

8.5. The graph

7.5. Flooding and the Synchronization of adjacencies

An adjacency Databases

In OSPF, adjacent routers within an area must synchronize their
databases. However, as observed in [FLOOD-OPT], a more concise
requirement of OSPF is that all routers in an area must converge
on the same link state database. It is bound sufficient to send a
single copy of the network that LSAs to the two neighboring routers have in common. an area
than send one copy on each connected interface. [FLOOD-OPT]
describes in detail how to minimize flooding (Initial LSDB
synchronization as well as the asynchronous LSA updates) within
an area.

In the case where some of the neighbors are TE compliant and
others are not, the designated OSPF-TE router will exchange
different sets of LSAs with its neighbors. TE LSAs are
exchanged only with the TE neighbors. Native LSAs are
exchanged with all neighbors (TE and non-TE alike).

A new OSPFIGP-TE multicast address 224.0.0.24 may be used for
the exchange of TE compliant database descriptors. Flooding
optimization in a TE network is essential as the control
traffic for a TE network is likely to be higher than that of a
non-TE network. Flooding optimization will help minimize LSA
announcements and the associated retransmissions and
acknowledgements on the network.

7.6. The graph of adjacencies

If two routers have multiple networks in common, they may have
multiple adjacencies between them. The adjacency may be split into one of
two different types - Adjacency between
TE-compliant routers and native OSPF adjacency between non-TE compliant
routers. A router may choose to support one or and TE adjacency. OSPF-TE
routers will form both types of adjacency.

Two types of adjacency graphs are possible, possible depending on whether
a Designated Router is elected for the network. On physical
point-to-point networks, Point-to-MultiPoint Point-to-Multipoint networks and virtual
Virtual links, neighboring routers become adjacent whenever they
can communicate directly. The adjacency can only be one of
(a) TE-compliant or (b) non-TE compliant. native. In contrast, on broadcast and
NBMA networks the Designated Router designated router and the
Backup Designated Router backup designated
router may maintain two sets of adjacency.
However, the The remaining routers
will participate in form either TE-compliant adjacency or non-TE-compliant adjacency, but not
both. native adjacency. In the
Broadcast network below, you will notice that routers RT7 and RT3 are chosen as the
designated and backup routers respectively. Within the network, Routers RT3, RT4
and RT7 are TE-compliant. RT5 and RT6 are not. So, you RT4 will
notice
have TE and native adjacencies with the designated and backup
routers. RT5 and RT6 will only have native adjacency variation with RT4 vs. RT5 or RT6. the
designated and backup routers.

+---+ +---+
|RT1|------------|RT2| o---------------o
+---+ N1 +---+ RT1 RT2

RT7
o::::::::::
+---+ +---+ +---+ /|: :
|RT7| |RT3| |RT4| / | : :
+---+ +---+ +---+ / | : :
| | | / | : :
+-----------------------+ RT5o RT6o oRT4 :
| | N2 * * ; :
+---+ +---+ * * ; :
|RT5| |RT6| * * ; :
+---+ +---+ **; :
o::::::::::
RT3

Figure 6: The graph of adjacencies with TE-compliant routers.

8. TE LSAs - Packet network

The native OSPF OSPFv2 protocol, as of now, has a total of 11 LSA types.
LSA types 1 through 5 are defined in [OSPF-v2]. LSA types 6, 7
and 8 are defined in [MOSPF], [NSSA] and [BGP-OSPF] respectively.
Lastly,
LSA types 9 through 11 are defined in [OPAQUE].

Each of the LSA types have type has a unique flooding scope defined. scope. Opaque LSA types
9 through 11 are general purpose LSAs, with flooding
scope set to link-local, area-local and AS-wide (except stub
areas) respectively. As will become apparent from this
document, the general purpose content format and the coarse
flooding scope of Opaque LSAs are not suitable for disseminating
TE data.

In the following subsections, we define new LSAs for Traffic traffic
engineering (TE) use. The Values for the new TE LSA types are
assigned such that the high bit of the LS-type LSA-type octet is set
to 1. The new TE LSAs are largely modeled after the existing
LSAs for content format and have a custom suited unique flooding scope. Flooding
optimizations discussed in previous sections shall be used to
disseminate TE LSAs along the TE-restricted topology.

TE-router LSA is defined to advertise TE characteristics of the
an OSPF-TE router and all the TE-links attached to the TE-router.
TE-Link-Update
router. TE-incremental-Link-Update LSA is defined to
advertise individual link
specific incremental updates to the metrics of a TE updates. link.
Flooding scope for both these LSAs is the
TE topology within the area restricted to which the links belong. I.e.,
only those OSPF
TE nodes within in the area with TE links will receive
these TE LSAs. area.

TE-Summary network and router LSAs are defined to advertise
the reachability of area-specific TE networks and Area border
routers(along Border
Routers (along with router TE characteristics) to external
areas. Flooding Scope of the TE-Summary LSAs is the TE topology
in the entire AS less the non-backbone area for which the
the advertising router is an ABR. Just as with native OSPF
summary LSAs, the TE-summary LSAs do not reveal the topological
details of an area to external areas. But, the two summary LSAs
do differ in some respects. The flooding scope of TE summary
LSAs is different. As for content, TE summary network LSAs
simply describe reachability without summarization of network
access costs. And, unlike the native summary router LSA,
TE-summary router LSA content includes TE capabilities of the
advertising TE router.

TE-AS-external LSA and TE-Circuit-Path LSA are defined to
advertise AS external network reachability and pre-established pre-engineered
TE circuits respectively. While flooding scope for both these
LSAs can be the TE-topology in the entire AS, flooding scope for the pre-established
pre-engineered TE circuit LSA may optionally be restricted to
just the TE topology within an area.

Lastly, the new TE LSAs are defined so as to permit peer
operation of packet networks and non-packet networks alike.
As such, a new TE-Router-Proxy LSA is defined to allow
advertisement of a TE router, that is not OSPF capable, by
an OSPF-TE node as a proxy.

9.1.

8.1. TE-Router LSA (0x81)

The TE-router LSA (0x81) is modeled after the router LSA with and has the
same flooding scope as the router-LSA, except that router-LSA. However, the scope is
restricted to TE-only only the OSPF-TE nodes within the area. The TE-router
LSA describes the TE metrics of the router as well as the TE-links
attached to the router. Below is the format of the TE-router LSA.
Unless specified explicitly otherwise, the fields carry the same
meaning as they do in a router LSA. Only the differences are
explained below. Router-TE flags, Router-TE TLVs, Link-TE options,
and Link-TE TLVs are each independently described in a separate
sub-section. the following sub-sections.

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 | 0x81 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link State ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertising Router |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS sequence number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS checksum | length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0 |V|E|B| 0 | Router-TE flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Router-TE flags (contd.) | Router-TE TLVs |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| .... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| .... | # of TE links |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link Data |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | 0 | Link-TE flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link-TE flags (contd.) | Zero or more Link-TE TLVs |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link Data |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |

Option
In TE-capable router nodes, the TE-bit may be set to 1.

The following fields are used to describe each router link (i.e.,
interface). Each router link is typed (see the below Type field).
The Type field indicates the kind of link being described.

Type
A new link type "Positional-Ring Type" (value 5) is defined.
This is essentially a connection to a TDM-Ring. TDM ring network
is different from LAN/NBMA transit network in that, nodes on the
TDM ring do not necessarily have a terminating path between
themselves. Secondly, the order of links is important in
determining the circuit path. Third, the protection switching
and the number of fibers from a node going into a ring are
determined by the ring characteristics. I.e., 2-fiber vs
4-fiber ring and UPSR vs BLSR protected ring.

Type Description
__________________________________________________
1 Point-to-point connection to another router
2 Connection to a transit network
3 Connection to a stub network
4 Virtual link
5 Positional-Ring Type.

Link ID
Identifies the object that this router link connects to.
Value depends on the link's Type. For a positional-ring type,
the Link ID shall be IP Network/Subnet number, just as with a
broadcast transit network. The following table summarizes the
updated Link ID values.

Type Link ID
______________________________________
1 Neighboring router's Router ID
2 IP address of Designated Router
3 IP network/subnet number
4 Neighboring router's Router ID
5 IP network/subnet number

Link Data
This depends on the link's Type field. For type-5 links, this
specifies the router interface's IP address.

9.1.1.

8.1.1. Router-TE flags - TE capabilities of the router

Below is an initial set of definitions. More may be standardized
if necessary. The TLVs are not expanded in the current rev. Will
be done in the follow-on revs.

The field imposes a restriction
of no more than 32 following flags are used to describe the TE capabilities of a
router-TE. an
OSPF-TE router. The remaining bits of the 32-bit word are reserved
for future use.

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|L|L|P|T|L|F| |S|S|S|C|
|S|E|S|D|S|S| |T|E|I|S|
|R|R|C|M|C|C| |A|L|G|P|
|L|L|P| | | | |L|S|C|
|S|E|S| | | | |S|I|S|
|R|R|C| | | | |P|G|P|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|<---- Boolean TE flags ------->|<- TE flags pointing to TLVs ->|

Bit LSR
When set, the router is considered to have LSR capability.

Bit LER
When set, the router is considered to have LER capability.
All MPLS border routers will be required to have the LER
capability. When the E bit is also set, that indicates an
AS Boundary router with LER capability. When the B bit is
also set, that indicates an area border router with LER
capability.

Bit PSC

Indicates the node is Packet Switch Capable.

Bit TDM
Indicates the node is TDM circuit switch capable.

Bit LSC
Indicates the node is Lamda switch Capable.

Bit FSC
Indicates the node is Fiber (can also be a non-fiber link
type) switch capable.

Bit STA LSP
MPLS Label Stack Depth limit switch TLV TE-NODE-TLV-MPLS-SWITCHING follows.
This is applicable only when the PSC flag is set.

Bit SEL
TE Selection Criteria TLV, supported by the router, follows.

Bit SIG
MPLS Signaling protocol support TLV
TE-NODE-TLV-MPLS-SIG-PROTOCOLS follows.

BIT CSPF
CSPF algorithm support TLV TE-NODE-TLV-CSPF-ALG follows.

9.1.2.

8.1.2. Router-TE TLVs

The following Router-TE TLVs are defined.

TE-selection-Criteria

8.1.2.4. TE-NODE-TLV-MPLS-SWITCHING

MPLS switching TLV (Tag ID = 1) is applicable only for packet switched nodes. The values can be a series
TLV specifies the MPLS packet switching capabilities of resources that may be used
as the criteria for traffic engineering (typically with TE
node.

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tag = 0x8001 | Length = 6 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label depth | QOS | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

'Label depth' is the
aid depth of a signaling protocol such as RSVP-TE or CR-LDP or LDP).

- Bandwidth based LSPs (1)
- Priority based LSPs (2)
- Backup LSP (3)
- Link cost (4)

Bandwidth criteria label stack the node is often used in conjunction with Packet
Switch Capable nodes. The unit capable of bandwidth permitted to be
configured may however vary from vendor to vendor. Bandwidth
criteria may also be
processing on its ingress interfaces. An octet is used in conjunction with TDM nodes. Once
again, the granularity of bandwidth allocation may vary from
vendor to vendor.

Priority based traffic switching represent
label depth. A default value of 1 is relevant only to Packet
Switch Capable nodes. assumed when the TLV is not
listed.

'QOS' is a single octet field that may be assigned '1' or '0'. Nodes
supporting this criteria will
be QOS are able to interpret the EXP bits on in the MPLS header
to prioritize the multiple classes of traffic across through the same LSP.

Backup criteria refers to whether or not the node is capable
of finding automatic protection path in

8.1.2.2. TE-NODE-TLV-MPLS-SIG-PROTOCOLS

MPLS signaling protocols TLV lists all the case signaling protocol
supported by the
originally selected link fails. Such a local recovery node. An octet is
specific to the node and may not need to be notified used to the
upstream node.

MPLS-Signaling list each signaling
protocol TLV (Tag ID = 3)
The value can be supported.

0 1 2 bytes long, listing a combination of
RSVP-TE, 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tag = 0x8002 | Length = 5, 6 or 7 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Protocol-1 | ... | .... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

RSVP-TE protocol is represented as 1, CR-LDP as 2 and LDP.

Constraint-SPF algorithms-Support LDP as 3.
These are the only permitted signaling protocols at this time.

8.1.2.3. TE-NODE-TLV-CSPF-ALGORITHMS

The CSPF algorithms TLV (Tag ID = 4)
List lists all the CSPF algorithms algorithm codes
supported. Support for CSPF algorithms on a node is an indication that makes the node may be
requested for all eligible to
compute complete or partial circuit path selection during
circuit setup time. This paths. Support for CSPF
algorithms can also be beneficial in knowing whether or not the a node
is capable of expanding loose routes (in an MPLS signaling request)
into an LSP. Further,
the a detailed circuit path.

Two octets are used to list each CSPF algorithm support on an intermediate node can code. The algorithm
codes may be
beneficial when vendor defined and unique within an Autonomous System.
If the node terminates one or more of supports 'n' CSPF algorithms, the
hierarchical LSP tunnels.

Label Stack Depth TLV (Tag ID = 5)
Applicable only for PSC-Type traffic. A default value of Length would be
(4 + 4 * ((n+1)/2)) octets.

0 1
is assumed. This indicates the depth of label stack the
node is capable of processing on an ingress interface.

9.1.3. 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tag = 0x8003 | Length = 4(1 + (n+1)/2) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| CSPF-1 | .... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| CSPF-n | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

8.1.3. Link-TE options flags - TE capabilities of a TE-link link

The following flags are used to describe the TE capabilities of a
link. The remaining bits of the 32-bit word are reserved for
future use.

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|T|N|P|T|L|F|D|
|T|N|P| | | |D| |S|L|B|C|
|E|T|K|D|S|S|B|
|E|T|K| | | |B| |R|U|W|O|
| |E|T|M|C|C|S| |L|G|A|L| |E|T| | | |S| |L|G| |L|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|<---- Boolean TE flags ------->|<- TE flags pointing to TLVs ->|

TE - Indicates whether TE is permitted on the link. A link
can be denied for TE use by setting the flag to 0.

NTE - Indicates whether non-TE traffic is permitted on the
TE link. This flag is relevant only when the TE
flag is set.

PKT - Indicates whether or not the link is capable of IP
packet termination.

TDM, LSC, FSC bits
- Same as defined for router TE options. processing.

DBS - Indicates whether or not Database synchronization
is permitted on this link.

SRLG Bit - Shared Risk Link Group TLV TE-LINK-TLV-SRLG follows.

LUG bit - Link usage cost metric TLV TE-LINK-TLV-LUG follows.

BWA

BW bit - Data Link bandwidth TLV TE-LINK-TLV-BANDWIDTH follows.

COL bit - Data link Link Color TLV TE-LINK-TLV-COLOR follows.

9.1.4.

8.1.4. Link-TE TLVs
SRLG-TLV
This

8.1.4.1. TE-LINK-TLV-SRLG

The SRLG describes the list of Shared Risk Link Groups (SRLG) the
link belongs to. Use 2 bytes Two octets are used to list each SRLG.

BWA-TLV
This indicates If the link
belongs to 'n' SRLGs, the Length would be (4 + 4 * ((n+1)/2)) octets.

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tag = 0x0001 | Length = 4(1 + (n+1)/2) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SRLG-1 | .... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SRLG-n | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

8.1.4.2. TE-LINK-TLV-BANDWIDTH

The bandwidth TLV specifies maximum bandwidth, bandwidth available bandwidth,
for TE use and reserved bandwidth 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tag = 0x0002 | Length = 16 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Maximum Bandwidth |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Bandwidth available for later TE use etc. This TLV may also
describe |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved Bandwidth |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Bandwidth is expressed in units of 32 bytes/sec (256 bits/sec).
A 32-bit field for bandwidth would permit specification not exceeding
1 tera-bits/sec.

'Maximum bandwidth' is be the Data maximum link Layer protocols supported and capacity expressed in
bandwidth units.

'Bandwidth available for TE use' is the maximum reservable bandwidth
on the
Data link MTU size.

LUG-TLV
This indicates for use by all the TE circuit paths traversing the link.
The link is oversubscribed when this field is more than the
'Maximum Bandwidth'. When the field is less than the
'Maximum Bandwidth', the remaining bandwidth on the link may likely
be used for non-TE traffic.

'Reserved Bandwidth' is the bandwidth that is currently subscribed
from of the link. 'Reserved Bandwidth' must be less than the
'Bandwidth available for TE use'. New TE circuit paths are able to
claim no more than the difference between the two bandwidths for
reservation.

8.1.4.3. TE-LINK-TLV-LUG

The link usage cost - TLV specifies Bandwidth unit, Unit unit usage cost, LSP setup
TE circuit set-up cost, minimum and maximum durations
permitted any time constraints for setting setup and
teardown of TE circuits on the link.

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tag = 0x0003 | Length = 28 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Bandwidth unit usage cost |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TE circuit set-up cost |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TE circuit set-up time constraint |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TE circuit tear-down time constraint |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Circuit Setup time constraint
This 64-bit number specifies the time at or after which a
TE-circuit path may be set up on the TLV etc., including any link. The set-up time
constraint is specified as the number of seconds from the start
of January 1, 1970 UTC. A reserved value of 0 implies no circuit
setup time constraint.

Circuit Teardown time constraint
This 64-bit number specifies the time at or before which all
TE-circuit paths using the link must be torn down. The teardown
time constraint is specified as the number of seconds from the
start of January 1 1970 UTC. A reserved value of 0 implies no
circuit teardown time constraint.

No. of day constraints.

COLOR-TLV TE Circuit paths
This specifies the number of pre-engineered TE circuit paths
between the advertising router and the router specified in the
link state ID.

8.1.4.4. TE-LINK-TLV-COLOR

The color TLV is similar to the SRLG TLV, in that an autonomous
system Autonomous
System may choose to issue colors to link based on a TE-link meeting certain
criteria. This The color TLV can be used to specify the
color one or more colors
assigned to the link within as follows. Two octets are used to list each
color. If the scope link belongs to 'n' number of colors, the AS.

9.2. Length
would be (4 + 4 * ((n+1)/2)) octets.

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tag = 0x0004 | Length = 4(1 + (n+1)/2) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Color-1 | .... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Color-n | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

8.2. TE-incremental-link-Update LSA (0x8d)

A significant difference between a non-TE OSPF network and a TE OSPF
network is that the latter is may be subject to dynamic frequent real-time
circuit pinning and is more likely to undergo state TE-state updates. Specifically, some Some
links might undergo changes more frequently than others. Advertising the
entire TE-router LSA in response to a change in any single link
could be repetitive. Flooding
the network with TE-router LSAs at the aggregated speed of all the dynamic
link metric changes is simply not desirable.
The A smaller in size,
TE-incremental-link-update LSA advertises is designed to advertise only the
incremental link updates.

The

TE-incremental-link-Update LSA will be advertised as frequently
as the link state is changed. The TE-link sequence is largely the
advertisement of a sub-portion of router LSA. The sequence number on
this will be incremented with the TE-router LSA's sequence as the
basis. When an updated TE-router LSA is advertised within 30 minutes
of the previous advertisement, the updated TE-router LSA will assume
a sequence no. that is larger than the most frequently updated of
its links.

Below is the format of the TE-incremental-link-update LSA.

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 | 0x8d |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link State ID (same as Link ID) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertising Router |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS sequence number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS checksum | length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link Data |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | 0 | Link-TE options |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link-TE options | Zero or more Link-TE TLVs |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| # TOS | metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TOS | 0 | TOS metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Link State ID
This would be exactly the same as would have been specified as
as Link ID for a link within the router-LSA.

Link Data
This specifies the router ID the link belongs to. In majority of
cases, this would be same as the advertising router. This choice
for Link Data is primarily to facilitate proxy advertisement for
incremental link updates.

Say, a router-proxy-LSa router-proxy-LSA was used to advertise the TE-router-LSA
of a SONET/TDM node. Say, the proxy router is now required to
advertise incremental-link-update for the same SONET/TDM node.
Specifying the actual router-ID the link in the
incremental-link-update-LSA belongs to helps receiving nodes in
finding the exact match for the LSA in their database.

The tuple of (LS Type, LSA ID, Advertising router) uniquely identify
the LSA and replace LSAs of the same tuple with an older sequence
number. However, there is an exception to this rule in the context
of TE-link-update LSA. TE-Link update LSA will initially assume the
sequence number of the TE-router LSA it belongs to. Further, when a
new TE-router LSA update with a larger sequence number is advertised,
the newer sequence number is assumed by al the link LSAs.

9.3. TE-Circuit-paths

8.3. TE-Circuit-path LSA (0x8C)

TE-Circuit-paths

TE-Circuit-path LSA may be used to advertise the availability of
pre-established
pre-engineered TE circuit path(s) originating from any router
in the network. The flooding scope may be Area wide or AS wide.

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 | 0x84 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link State ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertising Router |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS sequence number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS checksum | length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0 |G|E|B|D|S|T|CktType| Circuit Duration (Optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Circuit Duration cont... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Circuit Duartion Duration cont.. | Circuit Setup time (Optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Circuit Setup time cont... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Circuit Setup time cont.. |Circuit Teardown time(Optional)|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Circuit Teardown time cont... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Circuit Teardown time cont.. | No. of TE circuit paths |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Circuit-TE ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Circuit-TE Data |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | 0 | Circuit-TE flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Circuit-TE flags (contd.) | Zero or more Circuit-TE TLVs |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Circuit-TE ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Circuit-TE Data |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |

Link State ID
The ID of the far-end router or the far-end Link-ID to which the
TE circuit path(s) is being advertised.

TE-circuit-path(s) flags

Bit G - When set, the flooding scope is set to be AS wide.
Otherwise, the flooding scope is set to be area wide.

Bit E - When set, the advertised Link-State ID is an AS boundary
router (E is for external). The advertising router and
the Link State ID belong to the same area.

Bit B - When set, the advertised Link state ID is an Area border
router (B is for Border)

Bit D - When set, this indicates that the duration of circuit
path validity follows.

Bit S - When set, this indicates that Setup-time of the circuit
path follows.

Bit T - When set, this indicates that teardown-time of the
circuit path follows.

CktType
This 4-bit field specifies the Circuit type of the Forward
Equivalency Class (FC).
0x01 - Origin is Router, Destination is Router.
0x02 - Origin is Link, Destination is Link.
0x04 - Origin is Router, Destination is Link.
0x08 - Origin is Link, Destination is Router.

Circuit Duration (Optional)
This 64-bit number specifies the seconds from the time of the
LSA advertisement for which the adversited pre-established
TE pre-engineered circuit path
will be valid. This field is specified only when the D-bit is
set in the TE-circuit-path flags.

Circuit Setup time (Optional)
This 64-bit number specifies the time at which the TE-circuit
path may be setup. set up. This field is specified only when the
S-bit is set in the TE-circuit-path flags. The setup set-up time is
specified as the number of seconds from the start of January
1 1970 UTC.

Circuit Teardown time (Optional)
This 64-bit number specifies the time at which the TE-circuit
path may be torn down. This field is specified only when the
T-bit is set in the TE-circuit-path flags. The teardown time
is specified as the number of seconds from the start of
January 1 1970 UTC.

No. of TE Circuit paths
This indicates specifies the number of pre-established pre-engineered TE circuit paths
between the advertising router and the router specified in the
link state ID.

Circuit-TE ID
This is the ID of the far-end router for a given TE-circuit
path segment.

Circuit-TE Data
This is the virtual link identifier on the near-end router for
a given TE-circuit path segment. This can be a private
interface or handle the near-end router uses to identify the
virtual link.

The sequence of (circuit-TE ID, Circuit-TE Data) list the
end-point nodes and links in the LSA as a series.

Circuit-TE flags
This lists the Zero or more TE-link TLVs that all member
elements of the LSP meet.

9.4.

8.4. TE-Summary LSAs

TE-Summary-LSAs are the Type 0x83 and 0x84 LSAs. These LSAs are
originated by area border routers. TE-Summary-network-LSA (0x83)
describes the reachability of TE networks in a non-backbone
area, advertised by the Area Border Router. Type 0x84
summary-LSA describes the reachability of Area Border Routers
and AS border routers and their TE capabilities.

One of the benefits of having multiple areas within an AS is
that frequent TE advertisements within the area do not impact
outside the area. Only the TE abstractions as befitting the
external areas are advertised.

9.4.1.

8.4.1. TE-Summary Network LSA (0x83)

TE-summary network LSA may be used to advertise reachability of
TE-networks accessible to areas external to the originating
area. The content and the flooding scope of a TE-Summary LSA
is different from that of a native summary LSA.

The scope of flooding for a TE-summary network is AS wide, with
the exception of the originating area and the stub areas. The
area border router for each non-backbone area is responsible
for advertising the reachability of backbone networks into the
area.

Unlike a native-summary network LSA, TE-summary network LSA does
not advertise summary costs to reach networks within an area.
This is because, because TE parameters are not necessarily additive or
comparative. The parameters can be varied in their expression.
A
For example, a TE-summary network LSA will not be know to summarize a
network whose links do not fall under an SRLG (Shared-Risk Link
Group). This is way, the TE-summary LSA merely advertises the
reachable
reachability of TE networks within an area. The specific circuit
paths can be computed by the BDRs. On the other hand, if there
are specific Pre-engineered circuit paths to advertise, that can be done
independently
are advertised using TE-Circuit-path LSA (refer: (refer section 9.3) 8.3).

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 | 0x83 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link State ID (IP Network Number) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertising Router (Area Border Router) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS sequence number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS checksum | length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Network Mask |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Area-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

9.4.2.

8.4.2. TE-Summary router LSA (0x84)

TE-summary router LSA may be used to advertise the availability of
Area Border Routers (ABRs) and AS Border Routers (ASBRs) that are
TE capable. The TE-summary router LSAs are originated by the Area
Border Routers. The scope of flooding for the TE-summary router LSA
is the non-backbone area the advertising ABR belongs to.

Link State ID
The ID of the Area border router or the AS border router whose
TE capability is being advertised.

Advertising Router
The ABR that advertises its TE capabilities (and the OSPF areas
it belongs to) or the TE capabilities of an ASBR within one of
the areas the ABR is a border router of.

No. of Areas
Specifies the number of OSPF areas the link state ID belongs to.

Area-ID
Specifies the OSPF area(s) the link state ID belongs to. When
the link state ID is same as the advertising router ID, this the
Area-ID lists all the areas the ABR belongs to. In the case
the link state ID is an ASBR, this the Area-ID simply lists the
area the ASBR belongs to. The advertising router is assumed to
be the ABR from the same area the ASBR is located in.

Summary-router-TE flags

Bit E - When set, the advertised Link-State ID is an AS boundary
router (E is for external). The advertising router and
the Link State ID belong to the same area.

Bit B - When set, the advertised Link state ID is an Area
border router (B is for Border)

Router-TE flags,
Router-TE TLVs (TE capabilities of the link-state-ID router)

TE Flags and TE TLVs are as applicable to the ABR/ASBR
specified in the link state ID. The semantics is same as
specified in the Router-TE LSA.

9.5.

8.5. TE-AS-external LSAs (0x85)

TE-AS-external-LSAs are the Type 0x85 LSAs. This is modeled after
AS-external LSA format and flooding scope. These TE-AS-external LSAs are
originated by AS boundary routers with TE extensions (say, a BGP node which can
communicate MPLS labels across to external ASes), extensions, and describe
the TE networks and pre-established TE links pre-engineered circuit paths external to the
AS. The As with AS-external LSA, the flooding scope of this the
TE-AS-external LSA is similar to that of an AS-external LSA.
I.e., AS wide, with the exception of stub areas.

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 | 0x85 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link State ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertising Router |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS sequence number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS checksum | length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Network Mask |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Forwarding address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| External Route Tag |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| # of Virtual TE links | 0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link-TE flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link-TE TLVs |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TE-Forwarding address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| External Route TE Tag |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |

Network Mask
The IP address mask for the advertised TE destination. For
example, this can be used to specify access to a specific
TE-node or TE-link with an mask of 0xffffffff. This can also
be used to specify access to an aggregated set of destinations
using a different mask, mask. ex: 0xff000000.

Link-TE flags,
Link-TE TLVs
The TE attributes of this route. These fields are optional and
are provided only when one or more pre-established pre-engineered circuits can
be specified with the advertisement. Without these fields,
the LSA will simply state TE reachability info.

Forwarding address
Data traffic for the advertised destination will be forwarded to
this address. If the Forwarding address is set to 0.0.0.0, data
traffic will be forwarded instead to the LSA's originator (i.e.,
the responsible AS boundary router).

External Route Tag
A 32-bit field attached to each external route. This is not
used by the OSPF protocol itself. It may be used to communicate
information between AS boundary routers; the precise nature of
such information is outside the scope of this specification.

9.6.

9. TE LSAs - Non-packet network

A non-packet network would use all the TE LSAs described in the
previous section for a packet network, albeit with some variations.
These variations are described in the following subsections.

TE-Router-Proxy LSA is defined to allow proxy advertisement for
non-packet TE-nodes by an OSPF-TE router.

9.1. TE-Router LSA (0x81)

The following fields are used to describe each router link (i.e.,
interface). Each router link is typed (see the below Type field).
The Type field indicates the kind of link being described.

Type
A new link type "Positional-Ring Type" (value 5) is defined.
This is essentially a connection to a TDM-Ring. TDM ring network
is different from LAN/NBMA transit network in that nodes on the
TDM ring do not necessarily have a terminating path between
themselves. Secondly, the order of links is important in
determining the circuit path. Third, the protection switching
and the number of fibers from a node going into a ring are
determined by the ring characteristics. I.e., 2-fiber vs
4-fiber ring and UPSR vs BLSR protected ring.

Link ID
Identifies the object that this router link connects to.
Value depends on the link's Type. For a positional-ring type,
the Link ID shall be IP Network/Subnet number just as the case
with a broadcast transit network. The following table
summarizes the updated Link ID values.

Link Data
This depends on the link's Type field. For type-5 links, this
specifies the router interface's IP address.

9.1.1. Router-TE flags - TE capabilities of the router

Flags specific to non-packet TE-nodes are described below.

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|L|L|P|T|L|F| |S|S|S|C|
|S|E|S|D|S|S| |T|E|I|S|
|R|R|C|M|C|C| |A|L|G|P|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|<---- Boolean TE flags ------->|<- TE flags pointing to TLVs ->|

Bit TDM
Indicates the node is TDM circuit switch capable.

Bit LSC
Indicates the node is Lambda switch Capable.

Bit FSC

Indicates the node is Fiber (can also be a non-fiber link
type) switch capable.

9.1.2. Link-TE options - TE capabilities of a TE-link

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|T|N|P|T|L|F|D| |S|L|B|C|
|E|T|K|D|S|S|B| |R|U|W|O|
| |E|T|M|C|C|S| |L|G|A|L|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|<---- Boolean TE flags ------->|<- TE flags pointing to TLVs ->|

TDM, LSC, FSC bits
- Same as defined for router TE options.

9.2. Changes to Network LSA

Network-LSA is the Type 2 LSA. With the exception of the following,
no additional changes will be required to this LSA for TE
compatibility. The LSA format and flooding scope remains unchanged.

A network-LSA is originated for each broadcast, NBMA and
Positional-Ring type network in the area which supports two or
more routers. The TE option is also required to be set while
propagating the TDM network LSA.

9.6.1.

9.2.1. Positional-Ring type network LSA - New Network type for TDM-ring.
- Ring ID: (Network Address/Mask)
- No. of elements in the ring (a.k.a. ring neighbors)
- Ring Bandwidth
- Ring Protection (UPSR/BLSR)
- ID of individual nodes (Interface IP address)
- Ring type (2-Fiber vs. 4-Fiber, SONET vs. SDH)

Network LSA will be is required for SONET RING. Unlike the broadcast
type, the sequence in which the NEs Network Elements (NEs) are
placed on a RING-network is pertinent. The nodes in the ting ring
must be described clock wise, assuming the GNE Gateway Network
Element (GNE) as the starting element.

9.7.

9.3. TE-Router-Proxy LSA (0x8e)

This is a variation to the TE-router LSA in that the TE-router LSA
is not advertised by the network element, but rather by a trusted
TE-router Proxy. This is typically the scenario in a non-packet
TE network, where some of the nodes do not have OSPF functionality
and count on a helper node to do the advertisement for them. One
such example would be the SONET/SDH ADM nodes in a TDM ring. The
nodes may principally depend upon the GNE (Gateway Network Element)
to do the advertisement for them. TE-router-Proxy LSA shall not be
used to advertise Area Border Routers and/or AS border Routers.

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 | 0x8e |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link State ID (Router ID of the TE Network Element) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertising Router |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS sequence number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS checksum | length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0 | Router-TE flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Router-TE flags (contd.) | Router-TE TLVs |
+---------------------------------------------------------------+
| .... |
+---------------------------------------------------------------+
| .... | # of TE links |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link Data |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | 0 | Link-TE options |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link-TE flags | Zero or more Link-TE TLVs |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link Data |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |

9.8. Others

We may also introduce a new TE-NSSA LSA, similar to the native-NSSA
LSA. TE-NSSA will help ensure that not all external TE routes are
flooded into the NSSA area. A TE capable router can become the NSSA
translator. All parameters and contents of TE-NSSA LSAs are
transferred as is.

10. Abstract topology representation with TE support

Below, we assume consider a TE network that is composed of three OSPF areas,
namely areas -
Area-1, Area-2 and Area-3, attached together through the backbone
area. The following figure is an inter-area topology
abstraction from the perspective of routers in Area-1. The
abstraction is similar, but not the same, as that of the non-TE
abstraction. As such, the authors claim the model is easy to
understand and emulate. The abstraction illustrates reachability
of TE networks and nodes in areas external to the local area and
ASes external to the local AS. The abstraction also illustrates
pre-established TE links that may be advertised by ABRs and ASBRs. Area-1 an has a single area border router, ABR-A1 and no
ASBRs. Area-2 has an Area area border router ABR-A2 and an AS border
router ASBR-S1. Area-3 has two Area area border routers ABR-A2 and ABR-A3;
ABR-A3 and an AS border router ASBR-S2. There may be any number of Pre-engineered
TE links amongst ABRs and ASBRs. The following example network
also assumes a
single TE-link pre-engineered TE circuit path between ABR-A1
and ABR-A2; between ABR-A1 and ABR-A3; between ABR-A2 to and
ASBR-S1; and between ABR-A3 to and ASBR-S2.
All Area border

The following figure is an inter-area topology abstraction
from the perspective of routers in Area-1. The abstraction
illustrates reachability of TE networks and nodes within area
to the external areas in the same AS border routers are assumed and to
be represented by their the external ASes.
The abstraction also illustrates pre-engineered TE capabilities. circuit
paths advertised by ABRs and ASBRs.

+-------+
|Area-1 |
+-------+
+-------------+ |
|Reachable TE | +------+ +--------+
|networks in |--------|ABR-A1| |-------| ABR-A1 |
|backbone area| +------+ +--------+
+-------------+ | | |
+-------------+
+--------------+ | +-------------------+ +-----------------+
| | |
+-----------------+ | +-----------------+
|Pre-engineered TE| +----------+ |Pre-engineered TE|
|circuit path(s) | | Backbone | |circuit path(s) |
|to ABR-A2 | | Area | |to ABR-A3 |
+-----------------+ +----------+ +-----------------+
| | | |
+----------+ | | |
| | +--------------+ |
+-----------+ | | | | +-----------+
|Reachable | +------------+ +------+ +--------+ +--------+ |Reachable |
|TE networks|---| networks|------| ABR-A2 | |ABR-A3|--|TE | ABR-A3 |--|TE networks|
|in Area A2 | +------------+ +------+ +--------+ +--------+ |in Area A3 |
+-----------+ / | | | | | | +-----------+
/
+-------------+ | | +-------------------+ +-----------------+ | +----------+
/
| +-------------+ | +-----------+ | | |
+-----------+ +--------------+ | | | +--------------+
|Reachable | |Pre-engineered| | | | |Pre-engineered|
|TE networks| |TE Ckt path(s)| +------+ +------+ |TE Ckt path(s)|
|in Area A3 | |to ASBR-S1 | |Area-2| |Area-3| |to ASBR-S2 |
+-----------+ +--------------+ +------+ +------+ +--------------+
| / | / | |
| +--------+ | +-----------+
+-------------+ | / | / | |
|AS external | +---------+ +-------------+ +---------+
|TE-network |------| |----| ASBR-S1 | | ASBR-S2 |
|reachability | +---------+ +-------------+ +---------+
|from ASBR-S1 | | | |
+-------------+ +---+ +-------+ +-----------+
| | |
+-----------------+ +-------------+ +-----------------+
|Pre-engineered TE| |AS External | |Pre-engineered TE|
|circuit path(s) | |TE-Network | |circuit path(s) |
|reachable from | |reachability | |reachable from |
|ASBR-S1 | |from ASBR-S2 | |ASBR-S2 |
+-----------------+ +-------------+ +-----------------+

Figure 9: Inter-Area Abstraction as viewed by Area-1 TE-routers

11. Changes to Data structures in OSPF-TE nodes

11.1. Changes to Router data structure

The router with TE extensions must be able to include all the
TE capabilities (as specified in section 7.1) in the router data
structure. Further, routers providing proxy service to other TE
routers must also track the router and associated interface data
structures for all the TE client nodes for which the proxy
service is being provided. Presumably, the interaction between
the Proxy server and the proxy clients is out-of-band.

11.2. Two set sets of Neighbors

Two sets of neighbor data structures will need to be maintained. are required. TE-neighbors
set is used to advertise TE LSAs. Only the TE-nodes will be
members of the TE-neighbor set. Native neighbors set will be used
to advertise native LSAs. All neighboring nodes supporting
non-TE links can be are part of this set. As for flooding optimizations
based on neighbors set, readers may refer [FLOOD-OPT].

11.3. Changes to Interface data structure

The following new fields are introduced to the interface data
structure. These changes are in addition to the changes specified
in [FLOOD-OPT].

TePermitted
If the value of the flag is TRUE, the interface is permissible
to may be
advertised as a TE-enabled interface.

NonTePermitted
If the value of the flag is TRUE, the interface permits non-TE
traffic on the interface. Specifically, this is applicable to
packet networks, where data links may permit both TE and non-TE IP
packets. For FSC and LSC TE networks, this flag will be set to
FALSE. For Packet networks that do not permit non-TE traffic on
TE links also, this flag is set to TRUE.

PktTerminated
FALSE.

IpTerminated
If the value of the flag is TRUE, the interface terminates processes IP
Packet data and hence may be used for IP and OSPF data exchange.

AdjacencySychRequired
If the value of the flag is TRUE, the interface may be used to
synchronize the LSDB across all adjacent neighbors. This is
TRUE by default to all PktTerminated IpTerminated interfaces that are
enabled for OSPF. However, it is possible to set this to FALSE
for some of the interfaces.

TE-TLVs
Each interface may potentially have a maximum of 16 TLVS that
describe the link characteristics.

The following existing fields in Interface data structure will take
on additional values to support TE extensions.

Type
The OSPF interface type can also be of type "Positional-RING".
The Positional-ring type is different from other types (such
as broadcast and NBMA) in that the exact location of the nodes
on the ring is relevant, even as though they are all on the same
ring. SONET ADM ring is a good example of this. Complete ring
positional-ring description may be provided by the GNE on a
ring as a TE-network LSA for the ring.

List of Neighbors
The list may be statically defined for an interface, interface without
requiring the use of Hello protocol.

12. IANA Considerations

12.1. TE-compliant-SPF routers Multicast

This document proposes that TE LSA types and TE TLVs be
maintained by the IANA. The document also proposes an OSPFIGP-TE
multicast address be assigned by the IANA for the exchange of
TE database descriptors.

OSPFIGP-TE multicast address is suggested a value of 224.0.0.24
so as not to conflict with the recognized multicast address allocation
definitions, as defined in
http://www.iana.org/assignments/multicast-addresses

The following sub-section explains the criteria to be used by the
IANA to assign TE LSA types and TE TLVs.

12.1. TE LSA type values

LSA type is an 8-bit field required by each LSA. TE LSA types
will have the high bit set to 1. TE LSAs can range from 0x80
through 0xFF. The following values are defined in sections
8.0 and 9.0. The remaining values are available for assignment
by the IANA with IETF Consensus [Ref 11].

TE LSA Type Value
_________________________________________

TE-Router LSA 0x81
TE-Summary Network LSA 0x83
TE-Summary router LSA 0x84
TE-AS-external LSAs 0x85
TE-Circuit-paths LSA 0x8C
TE-incremental-link-Update LSA 0x8d
TE-Router-Proxy LSA 0x8e

12.2. New TE-LSA Types

12.3. New TLVs (Router-TE TE TLV tag values

TLV type is a 16-bit field required by each TE TLV. TLV type
shall be unique across the router and Link-TE TLVs)

12.3.1. TE-selection-Criteria link TLVs. A TLV (Tag ID = 1)
- Bandwidth based LSPs (1)
- Priority based LSPs (2)
- Backup LSP (3)
- Link cost (4)

12.3.2. MPLS-Signaling protocol type
can range from 0x0001 through 0xFFFF. TLV (Tag ID = 3)
- RSVP-TE signaling
- LDP signaling
- CR-LDP signaling

12.3.3. Constraint-SPF algorithms-Support type 0 is reserved
and unassigned. The following TLV (Tag ID = 4)
- CSPF Algorithm Codes.

12.3.4. SRLG-TLV (Tag ID = 0x81)
- SRLG group IDs
12.3.5. BW-TLV (Tag ID = 0x82)

12.3.6 CO-TLV (Tag ID = 0x83) types are defined in sections
8.0 and 9.0. The remaining values are available for assignment
by the IANA with IETF Consensus [Ref 11].

TE TLV Tag Reference Value
Section
_________________________________________________________

TE-LINK-TLV-SRLG Section 8.1.4.1 0x0001
TE-LINK-TLV-BWA Section 8.1.4.2 0x0002
TE-LINK-TLV-LUG Section 8.1.4.3 0x0003
TE-LINK-TLV-COLOR Section 8.1.4.4 0x0004
TE-NODE-TLV-MPLS-SWITCHING Section 8.1.2.1 0x8001
TE-NODE-TLV-MPLS-SIG-PROTOCOLS Section 8.1.2.2 0x8002
TE-NODE-TLV-CSPF-ALG Section 8.1.2.3 0x8003

13. Acknowledgements

The authors wish to specially thank Chitti Babu and his team
for verifying portions of the specification for a packet
network. The authors also wish to thank Vishwas Manral, Chitti Babu, Riyad
Hartani and Tricci So for their valuable comments and feedback
on the draft.

14. Security Considerations

Security considerations for the base OSPF protocol are covered
in [OSPF-v2] and [SEC-OSPF]. This memo does not create any new
security issues for the OSPF protocol. Security considerations for measures
applied to the base native OSPF protocol (refer [SEC-OSPF]) are
covered directly
applicable to the TE LSAs described in [OSPF-v2]. As the document. Discussed
below are the security considerations in processing TE LSAs.

Secure communication between OSPF-TE nodes has a general rule, number of
components. Authorization, authentication, integrity and
confidentiality. Authorization refers to whether a TE network particular
OSPF-TE node is likely authorized to generate significantly more control traffic than receive or propagate the TE LSAs
to its neighbors. Failing the authorization process might
indicate a native
OSPF network. The excess traffic is almost directly proportional resource theft attempt or unauthorized resource
advertisement. In either case, the OSPF-TE nodes should take
proper measures to audit/log such attempts so as to alert the
administrator to take necessary action. OSPF-TE nodes may refuse
to communicate with the neighboring nodes that fail to prompt
the required credentials.

Authentication refers to confirming the identity of an originator
for the datagrams received from the originator. Lack of strong
credentials for authentication of OSPF-TE LSAs can seriously
jeopardize the rate at which TE circuits are setup service rendered by the network. A consequence
of not authenticating a neighbor would be that an attacker could
spoof the identity of a "legitimate" OSPF-TE node and torn down within manipulate
the state, and the TE database including the topology and
metrics collected. This could potentially lead to
denial-of-service on the TE network. Another consequence of not
authenticating is that an autonomous system. It attacker could pose as OSPF-TE neighbor
and respond in a manner that would divert TE data to the attacker.

Integrity is important required to ensure that an OSPF-TE message has not
been accidentally or maliciously altered or destroyed. The result
of a lack of data integrity enforcement in an untrusted environment
could be that an imposter will alter the messages sent by a
legitimate adjacent neighbor and bring the OSPF-TE on a node and
the whole network to a halt or cause a denial of service for the
TE circuit paths effected by the alteration.

Confidentiality of MIDCOM messages ensure that the TE database
synchronizations happen quickly when compared LSAs are
accessible only to the aggregate authorized entities. When OSPF-TE is
deployed in an untrusted environment, lack of confidentiality will
allow an intruder to perform traffic flow analysis and snoop the
TE control network to monitor the traffic metrics and the rate at
which circuit paths are being setup an tear-down rates.

REFERENCES and torn-down. The intruder
could cannibalize a lesser secure OSPF-TE node and destroy or
compromise the state and TE-LDSB on the node. Needless to say, the
least secure OSPF-TE will become the achilles heel and make the TE
network vulnerable to security attacks.

15. Normative References

[IETF-STD] Bradner, S., " The Internet Standards Process --
Revision 3", "Key words for use in RFCs to indicate
Requirement Levels", BCP 14, RFC 1602, IETF, October 1996. 2119, March 1997.

[RFC 1700] J. Reynolds and J. Postel, "Assigned Numbers",
RFC 1700

[RFC 2434] Narten, T. and H. Alvestrand, "Guidelines for
writing an IANA Considerations Section in RFCs",
BCP 26, RFC 2434, October 1998.

[MPLS-TE] Awduche, D., et al, "Requirements for Traffic
Engineering Over MPLS," RFC 2702, September 1999.

[OSPF-v2] Moy, J., "OSPF Version 2", RFC 2328, April 1998.

[SEC-OSPF] Murphy, S., Badger, M., and B. Wellington, "OSPF with
Digital Signatures", RFC 2154, June 1997

[FLOOD-OPT] Zinin, A. and M. Shand, "Flooding Optimizations in
link-state routing protocols", work in progress,
<draft-ietf-ospf-isis-flood-opt-01.txt>

15. Informative References

[GMPLS-TE] P.A. Smith et. al, "Generalized MPLS - Signaling
Functional Description", work in progress,
draft-ietf-mpls-generalized-signaling-03.txt
draft-ietf-mpls-generalized-signaling-09.txt

[RSVP-TE] Awduche, D., L. Berger, D. Gan, T. Li, V. Srinivasan,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC3209, IETF, December 2001

[CR-LDP] Jamoussi, B. et al, "Constraint-Based LSP Setup
using LDP", draft-ietf-mpls-cr-ldp-06.txt,
Work in Progress.

[OSPF-v2] Moy, J., "OSPF Version 2", RFC 2328, April 1998.

[MOSPF] Moy, J., "Multicast Extensions to OSPF", RFC 1584,
March 1994.

[NSSA] Coltun, R., V. Fuller and P. Murphy, "The OSPF NSSA
Option", draft-ietf-ospf-nssa-update-10.txt, draft-ietf-ospf-nssa-update-11.txt, Work in
Progress.

[OPAQUE] Coltun, R., "The OSPF Opaque LSA Option," RFC 2370,
July 1998.

[FLOOD-OPT] Zinin, A. and M. Shand, "Flooding Optimizations in
link-state routing protocols", work in progress,
<draft-ietf-ospf-isis-flood-opt-01.txt>

[OPQLSA-TE] Katz, D., D. Yeung and K. Kompella, "Traffic
Engineering Extensions to OSPF", work in progress,
<draft-katz-yeung-ospf-traffic-06.txt>
<draft-katz-yeung-ospf-traffic-09.txt>

[OPQLSA-GMPLS] Kompella, K., Y. Rekhter, A. Banerjee, J. Drake,
G. Bernstein, D. Fedyk, E. Mannie, D. Saha and
V. Sharma, "OSPF Extensions in Support of Generalized
MPLS", <draft-ietf-ccamp-ospf-gmpls-extensions-01.txt>, <draft-ietf-ccamp-ospf-gmpls-extensions-09.txt>,
work in progress.

Authors' Addresses

Pyda Srisuresh
Kuokoa Networks, Inc.
475 Potrero Avenue
Sunnyvale, CA 94085
U.S.A.
EMail: srisuresh@yahoo.com

Paul Joseph
Force10 Networks
1440 McCarthy Boulevard
Milpitas, CA 95035
U.S.A.
EMail: pjoseph@Force10Networks.com