OSPF-xTE: Experimental Extension to OSPF for Traffic Engineering
draft-srisuresh-ospf-te-07
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Paul Joseph
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Pyda Srisuresh
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Network Working Group P. Srisuresh
INTERNET-DRAFT Caymas Systems
Expires as of June 31, 2005 P. Joseph
Symbol Technologies
December 31, 2004
OSPF-xTE: An experimental extension to OSPF for Traffic Engineering
<draft-srisuresh-ospf-te-07.txt>
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Abstract
This document defines OSPF-xTE, an experimental traffic engineering
(TE) extension to the link-state routing protocol OSPF. OSPF-xTE
defines new TE LSAs to disseminate TE metrics within an autonomous
System (AS), which may consist of multiple areas. Further, When an
AS consists of TE and non-TE nodes, OSPF-xTE ensures that Non-TE
nodes in the AS are uneffected by the TE LSAs. OSPF-xTE generates
a stand-alone TE Link State Database (TE-LSDB), distinct from the
native OSPF LSDB, for computation of TE circuit paths. OSPF-xTE is
versatile and extendible to non-packet networks such as SONET/TDM
and optical networks.
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Table of Contents
1. Introduction ................................................3
2. Principles of traffic engineering ...........................3
3. Terminology .................................................4
3.1. Native OSPF terms ......................................5
3.2. OSPF-xTE terms .........................................5
4. Motivations behind the design of OSPF-xTE ...................8
4.1. Scalable design ........................................9
4.2. Operable in mixed and peer networks ....................9
4.3. Efficient in flooding reach ............................9
4.4. Ability to reserve TE-exclusive links .................10
4.5. Extendible design .....................................10
4.6. Unified for packet and non-packet networks ............10
4.7. Networks benefiting from the OSPF-xTE design ..........11
5. OSPF-xTE solution overview .................................12
5.1. OSPF-xTE Solution .....................................12
5.2. Assumptions ...........................................13
6. Opaque LSAs to OSPF-xTE transition strategy ................14
7. OSPF-xTE router adjacency - TE topology discovery ..........14
7.1. The OSPF-xTE router adjacency .........................14
7.2. The Hello Protocol ....................................15
7.3. The Designated Router .................................15
7.4. The Backup Designated Router ..........................15
7.5. Flooding and the Synchronization of Databases .........16
7.6. The graph of adjacencies ..............................16
8. TE LSAs for packet network .................................18
8.1. TE-Router LSA (0x81) ..................................19
8.2. TE-incremental-link-Update LSA (0x8d) .................27
8.3. TE-Circuit-paths LSA (0x8C) ...........................29
8.4. TE-Summary LSAs .......................................32
8.5. TE-AS-external LSAs (0x85) ............................34
9. TE LSAs for non-packet network .............................36
9.1. TE-Router LSA (0x81) ..................................36
9.2. TE-Positional-ring-network LSA (0x82) .................38
9.3. TE-Router-Proxy LSA (0x8e) ............................40
10. Abstract topology representation with TE support ...........41
11. Changes to Data structures in OSPF-xTE routers .............43
11.1. Changes to Router data structure .....................43
11.2. Two set of Neighbors .................................43
11.3. Changes to Interface data structure ..................43
12. IANA Considerations ........................................44
12.1. TE LSA type values ...................................44
12.2. TE TLV tag values ....................................45
13. Acknowledgements ...........................................45
14. Security Considerations ....................................46
15. Normative References .......................................47
16. Informative References .....................................47
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17. Authors' Addresses .........................................48
18. Full Copyright Statement ...................................48
1. Introduction
This document defines OSPF-xTE, an experimental traffic
engineering (TE) extension to the link-state routing protocol
OSPF. The objective of OSPF-xTE is to discover TE network
topology and disseminate TE metrics within an autonomous system
(AS). A stand-alone TE Link State Database (TE-LSDB), different
from the native OSPF LSDB, is created to facilitate computation
of TE circuit paths. Devising algorithms to compute TE circuit
paths is not an objective of this document.
OSPF-xTE is different from the Opaque-LSA-based approach
outlined in [OPQLSA-TE]. Section 4 describes the motivations
behind the design of OSPF-xTE. Section 6 outlines a transition
path for those currently using [OPQLSA-TE] for intra-area and
wish to extend this using OSPF-xTE across the AS.
Readers interested in TE extensions for the packet networks
alone may skip section 9.0.
2. Principles of traffic engineering
The objective of traffic engineering (TE) is to set up circuit
path(s) between a pair of nodes or links and to forward traffic
of a certain forwarding equivalency class (FEC) through the
circuit path. Only the unicast circuit paths are considered
in this section. Multicast variations are outside the scope.
A traffic engineered circuit path is uni-directional and may
be identified by the tuple of (FEC, TE circuit parameters,
Origin Node/Link, Destination node/Link).
Forwarding Equivalency Class (FEC) is a grouping of traffic
that is forwarded in the same manner by a node. A FEC may be
classified based on a number of criteria as follows.
a) Traffic arriving on a specific interface,
b) Traffic arriving at a certain time of day,
c) Traffic meeting a certain packet based classification
criteria (ex: based on a match of the fields in the IP
and transport headers within a packet),
d) Traffic in a certain priority class,
e) Traffic arriving on a specific set of TDM (STS) circuits
on an interface,
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f) Traffic arriving on a certain wavelength of an interface
Discerning traffic based on the FEC criteria is mandatory for
Label Edge Routers (LERs). The intermediate Label Switched Routers
(LSRs) are transparent to the traffic content. LSRs are merely
responsible for keeping the circuit in-tact for the circuit
lifetime. This document will not address defining FEC criteria,
or the mapping of a FEC to circuit, or the associated signaling to
set up circuits. [MPLS-TE] and [GMPLS-TE] address the FEC criteria.
[RSVP-TE] and [CR-LDP] address signaling protocols to set up
circuits.
This document is concerned with the collection of TE metrics for
all the TE enforceable nodes and links within an autonomous system.
TE metrics for a node may include the following.
a) Ability to perform traffic prioritization,
b) Ability to provision bandwidth on interfaces,
c) Support for Constrained Shortest Path First (CSPF)
algorithms,
d) Support for certain TE-Circuit switch type,
e) Support for a certain type of automatic protection
switching
TE metrics for a link may include the following.
a) Available bandwidth,
b) Reliability of the link,
c) Color assigned to the link,
d) Cost of bandwidth usage on the link,
e) Membership to a Shared Risk Link Group (SRLG)
A number of CSPF algorithms may be used to dynamically set up
TE circuit paths in a TE network.
OSPF-xTE mandates the originating and the terminating entities of
a TE circuit path to be identifiable by their IP addresses.
3. Terminology
Definitions of majority of the terms used in 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 following subsections describe the native OSPF terms and
the OSPF-xTE terms used within this document.
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3.1. Native OSPF terms
3.1.1. Native node (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 OSPF-xTE extensions.
3.1.2. Native link (Non-TE link)
A native (or non-TE) link is a network attachment to a TE or
non-TE node used for IP packet traversal.
3.1.3. Native OSPF network (Non-TE network)
A native OSPF network refers to an OSPF network that does not
support TE. Non-TE network, native-OSPF network and non-TE
topology are used synonymously throughout the document.
3.1.4. LSP
LSP stands for "Label Switched Path". LSP is a TE circuit path
in a packet network. The terms LSP and TE circuit path are
used synonymously in the context of packet networks.
3.1.5. LSA
LSA stands for OSPF "Link State Advertisement".
3.1.6. LSDB
LSDB stands for "LSA Database". LSDB is a representation of the
topology of a network. A native LSDB, constituted of native OSPF
LSAs, represents the topology of a native IP network. TE-LSDB, on
the other hand, is constituted of TE LSAs and is a representation
of the TE network topology.
3.2. OSPF-xTE terms
3.2.1. TE node
TE-Node is a node in the traffic engineered (TE) network. A
TE-node has a minimum of one TE-link attached to it. Associated
with each TE node is a set of supported TE metrics. A TE node
may also participate in a native IP network.
In a SONET/TDM or photonic cross-connect network, a TE node is
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not required to be an OSPF-xTE node. An external OSPF-xTE node
may act as proxy for the TE nodes that cannot be routers
themselves.
3.2.2. TE link
TE Link is a network attachment point to a TE-node and is
intended for traffic engineering use. Associated with each
TE link is a set of supported TE metrics. A TE link 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
links.
3.2.3. TE circuit path
A TE circuit path is a uni-directional data path, defined by a
list of TE nodes connected to each other through TE links. A
TE circuit path is also often referred merely as a circuit path
or a circuit.
For the purposes of OSPF-xTE, the originating and terminating
entities of a TE circuit path must be identifiable by their
IP addresses. As a general rule, all nodes and links party to a
Traffic Engineered network should be uniquely identifiable by an
IP address.
3.2.4. OSPF-xTE node (OSPF-xTE router)
An OSPF-xTE node is a TE node that runs the OSPF routing protocol
and the OSPF-xTE extensions described in this document.
An autonomous system (AS) may be constituted of a combination of
native and OSPF-xTE nodes.
3.2.5. TE Control network
The IP network used by the OSPF-xTE nodes for OSPF-xTE
communication is referred as the TE control network or simply
the control network. The control network can be independent of
the TE data network.
3.2.6. TE network (TE topology)
A TE network is a network 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
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used synonymously throughout the document.
3.2.7. Packet-TE network (Packet network)
A packet-TE network is a TE network in which the nodes switch
MPLS packets. An MPLS packet is defined in [MPLS-TE] as a
packet with an MPLS header, followed by data octets. The
intermediary node(s) of a circuit path in a packet-TE network
perform MPLS label swapping to emulate the circuit.
Unless specified otherwise, the term packet network is used
throughout the document to refer a packet-TE network.
3.2.8. Non-packet-TE network (Non-packet network)
A non-packet-TE network is TE-network in which the nodes
switch non-packet entities such as an STS time slot, a Lambda
wavelength or simply an interface.
SONET/TDM and Fiber cross-connect networks are examples of
non-packet-TE networks. Circuit emulation in these networks
is accomplished by the switch fabric in the intermediary
nodes (based on TDM time slot, fiber interface or Lambda).
Unless specified otherwise, the term non-packet network is
used throughout the document to refer a non-packet-TE
network.
3.2.9. Mixed network
A mixed network is a network that is constituted of
packet-TE and non-TE networks combined. Traffic in the
network is strictly datagram oriented - IP datagrams or
MPLS packets. Routers in a mixed network may be TE or
native nodes.
OSPF-xTE is usable within a packet network or a mixed
network.
3.2.10. Peer network
A peer network is a network that is constituted of packet-TE
and non-packet-TE networks combined. In a peer network, a TE
node could potentially support TE links for the packet as
well as non-packet data.
OSPF-xTE is usable within a packet network or a non-packet
network or a peer network, which is a combination of the two.
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3.2.11. CSPF
CSPF stands for "Constrained Shortest Path First". Given a TE
LSDB and a set of constraints that must be satisfied to form a
circuit path, there may be several CSPF algorithms to obtain a
TE circuit path that meets the criteria.
3.2.12. 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 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 .... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| .... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3.2.13. Router-TE TLVs (Router TLVs)
TLVs used to describe the TE capabilities of a TE-node.
3.2.14. Link-TE TLVs (Link TLVs)
TLVs used to describe the TE capabilities of a TE-link.
4. Motivations behind the design of OSPF-xTE
There are several motivations that led to the design of OSPF-xTE.
OSPF-xTE is scalable, efficient and usable across a variety of
network topologies. These motivations are explained in detail in
the following subsections. The last subsection lists real-world
network scenarios that benefit from the OSPF-xTE.
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4.1. Scalable design
OSPF-xTE area level abstraction provides the scaling required
for the TE topology in a large autonomous system (AS).
An OSPF-xTE area border router will advertise summary LSAs for
TE and non-TE topologies independent of each other. Readers
may refer to section 10 for a topological view of the AS from
the perspective of a OSPF-xTE node in an area.
[OPQLSA-TE], on the other hand, is designed for intra-area and
is not scalable to AS-wide scope.
4.2. Operable in mixed and peer networks
OSPF-xTE assumes that an AS may be constituted of coexisting
TE and non-TE networks. OSPF-xTE dynamically discovers TE
topology and the associated TE metrics of the nodes and links
that form the TE network. As such, OSPF-xTE generates a
stand-alone TE-LSDB that is fully representative of the TE
network. Stand-alone TE-LSDB allows for speedy TE computations.
[OPQLSA-TE] is designed for packet networks and is not suitable
for mixes and peer networks. TE-LSDB in [OPQLSA-TE] is derived
from the combination of opaque LSAs and native LSDB. Further,
the TE-LSDB thus derived has no knowledge of the TE
capabilities of the routers in the network.
4.3. Efficient in flooding reach
OSPF-xTE is able to identify the TE topology in a mixed network
and will limit the flooding of TE LSAs to just the TE-nodes.
Non-TE nodes are not bombarded with TE LSAs.
In a TE 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 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. OSPF-xTE
defines TE-Incremental-Link-update LSA (section 8.2) to advertise
just a subset of the metrics that are prone to rapid changes.
The more frequent and wider the flooding frequency, the larger
the number of retransmissions and acknowledgements. The same
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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.
It is undesirable to flood non-TE nodes with TE information.
4.4. Ability to reserve TE-exclusive links
OSPF-xTE draws a clear distinction between TE and non-TE
links. A TE link may be configured to permit TE traffic
alone, and not permit 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-xTE allows for virtual isolation of
the two networks. Best-effort IP network and TE network often
have different service requirements. Keeping the two networks
physically isolated can be expensive. Combining the two
networks into a single physically connected network will
bring economies of scale, while service enforceability
can be maintained individually for each of the TE and non-TE
sections of the network.
[OPQLSA-TE] does not support the ability to isolate best-
effort IP traffic from TE traffic on a link. All links are
subject to best-effort IP traffic. An OSPF router could
potentially select a TE link to be its least cost link and
inundate the link with best-effort IP traffic, thereby
rendering the link unusable for TE purposes.
4.5. Extendible design
OSPF-xTE design is based on the tried and tested OSPF paradigm,
and inherits all the benefits of the OSPF, present and future.
TE-LSAs are extendible, just as the native OSPF on which
OSPF-xTE is founded.
4.6. Unified for packet and non-packet networks
OSPF-xTE is usable within a packet network or a non-packet
network or a combination peer network.
Signaling protocols such as RSVP and LDP work the same across
packet and non-packet networks. Signaling protocols merely need
the TE characteristics of nodes and links so they can signal the
nodes to formulate TE circuit paths. In a peer network, the
underlying control protocol must be capable of providing a
unified LSDB for all TE nodes (nodes with packet-TE links as well
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as non-packet-TE links) in the network. OSPF-xTE meets this
requirement.
4.7. Networks benefiting from the OSPF-xTE design
Below are examples of some real-world network scenarios that
benefit from OSPF-xTE.
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-xTE only nodes will allow the vendor to
introduce MPLS TE without destabilizing the existing network.
The native OSPF-LSDB will remain undisturbed while newer TE
links are added to the network.
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-xTE design. By maintaining
independent LSDBs for each type of service, TE links are not
cannibalized in a mixed network.
4.7.3. Large TE networks
The OSPF-xTE design is advantageous in large TE networks that
require the AS to be sub-divided into multiple areas. OSPF-xTE
permits inter-area exchange of TE information, which ensures
that all nodes in the AS have up-to-date As-wide TE
reachability knowledge. This in turn will make TE circuit
setup predictable and computationally bounded.
4.7.4. Non-packet networks and Peer networks
Vendors may also use OSPF-xTE for their non-packet TE networks.
OSPF-xTE defines the following functions in support of
non-packet TE 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).
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5. OSPF-xTE solution overview
5.1. OSPF-xTE Solution
Locally scoped opaque LSA (type 9) is used to discovery the TE
topology within a network. Section 7.1 describes in detail the
use of type 9 Opaque LSA for TE topology discovery. TE LSAs are
designed for use by the OSPF-xTE nodes. Section 8.0 describes
the TE LSAs in detail. Changes required of the OSPF data
structures to support OSPF-xTE are described in section 11.0.
A new TE-neighbors data structure will be used to advertise
TE LSAs along TE-topology.
An OSPF-xTE node will have the native LSDB and the TE-LSDB,
A native OSPF node will have just the native LSDB.
Consider the following OSPF area constituted of OSPF-xTE and
native OSPF routers. Nodes RT1, RT2, RT3 and RT6 are OSPF-xTE
routers with TE and non-TE link attachments. Nodes RT4 and RT5
are native OSPF routers with no TE links. When the LSA database
is synchronized, all nodes will share the same native LSDB.
OSPF-xTE nodes alone will have the additional TE-LSDB.
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+---+
| |--------------------------------------+
|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-xTE is an extension to the native OSPF protocol and does not
mandate changes to the existing OSPF. OSPF-xTE design makes the
following assumptions.
1. An OSPF-xTE node will need to establish router adjacency with
at least one other OSPF-xTE node in the area in order for the
router's TE-database to be synchronized within the area.
Failing this, the OSPF router will not be in the TE
calculations of other TE routers in the area.
It is the responsibility of the network administrator(s) to
ensure connectedness of the TE network. Otherwise, there can
be disjoint TE topologies within a network.
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2. OSPF-xTE nodes must advertise the link state of its TE-links.
TE-links are not obligated to support native IP traffic.
Hence, an OSPF-xTE node cannot be required to synchronize
its link-state database with neighbors on all its links.
The only requirement is to have the TE LSDB synchronized
across all OSPF-xTE nodes in the area.
3. A link in a packet network may be designated as a TE-link or
a native-IP link or both. For example, a link may be used for
both TE and non-TE traffic, so long as the link is
under-subscribed in bandwidth for TE traffic - say, 50% of
the link capacity is set aside for TE traffic.
4. Non-packet TE sub-topologies must have a minimum of one node
running OSPF-xTE protocol. For example, a SONET/SDH TDM ring
must have a minimum of one Gateway Network Element(GNE)
running OSPF-xTE. The OSPF-xTE node will advertise on behalf
of all the TE nodes in the ring.
6. Opaque LSAs to OSPF-xTE transition strategy
Below is a strategy to transition implementations currently using
opaque LSAs ([OPQLSA-TE]) within an area to adapt OSPF-xTE in
a gradual fashion across the AS.
1. Use [OPQLSA-TE] within an area. Derive TE topology within the
area from the combination of opaque LSAs and native LSDB.
2. 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-nodes in the backbone. The TE-ABRs on the backbone
area will in-turn advertise these summaries within their
connected areas.
7. OSPF-xTE router adjacency - TE topology discovery
OSPF creates adjacencies between neighboring routers for the purpose
of exchanging routing information. In the following subsections, we
describe the use of locally scoped Opaque LSA to discover OSPF-xTE
neighboring routers. The capability is used as the basis to build
TE topology.
7.1. The OSPF-xTE router adjacency
OSPF uses the options field in the hello packet to advertise optional
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router capabilities [OSPF]. However, all the bits in this field have
been allocated and there is no way to advertise OSPF-xTE capability
using the options field at this time. This document proposes using
local scope opaque lsa (OPAQUE-9 LSA) to advertise support for
OSPF-xTE and establish OSPF-xTE adjacency. In order to exchange
Opaque LSAs, the neighboring routers must have the O-bit (Opaque
option bit) set in the options field as a prerequisite.
[OSPF-CAP] proposes a format for exchanging router capabilities
via OPAQUE-9 LSA. Routers supporting OSPF-xTE will be required to
set the "OSPF Experimental TE" bit within the "router
capabilities" field. Two routers will not become TE-neighbors
unless they share a common network link on which both routers
advertise support for OSPF-xTE. Routers that donot support
OSPF-xTE may simply ignore the advertisement.
7.2. The Hello Protocol
The Hello Protocol is primarily responsible for dynamically
establishing and maintaining neighbor adjacencies. In a TE network,
it is not required for all links and neighbors to establish
adjacency using this protocol. OSPF-xTE router adjacency between
two routers is established using the method described in the
previous section.
For NBMA and broadcast networks, the HELLO protocol is responsible
for electing the Designated Router and the Backup Designated
Router. Routers supporting the TE option shall be given a higher
precedence for becoming a designated router over those that do
not support TE.
7.3. The Designated Router
When a router's non-TE link first becomes functional, it checks to
see whether there is currently a Designated Router for the network.
If there 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.
OSPF-xTE must be implemented on the most robust routers, as they
become likely candidates to take on the role as designated router.
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
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Backup Designated Router for the network. Once again, TE-compliance
must be weighed in conjunction with router priority in electing
the backup designated router.
7.5. Flooding and the Synchronization of Databases
In OSPF, adjacent routers within an area are required to
synchronize their databases. However, a more concise requirement
is that all routers in an area must converge on the same LSDB.
However, as stated in item 2 of section 5.2, a basic assertion
by OSPF-xTE is that the links used by the OSPF-xTE control
network for flooding must not be required to match the links
used by the data network for real-time data forwarding. For
instance, it should not be required to run the OSPF-xTE messages
over a TE-link that is configured not to permit non-TE traffic.
However, the control network must be setup such that a minimum
of one path exists between any two OSPF or OSPF-xTE routers
within the network for flooding purposes. This revised control
network connectivity requirement does not jeopardize
convergence of LSDB within an area.
In a mixed network, where some of the neighbors are TE
compliant and others are not, the designated OSPF-xTE 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).
Restricting the scope of TE LSA flooding to just the
OSPF-xTE nodes will not effect the native nodes that coexist
with the OSPF-xTE nodes.
The control traffic for a TE network (i.e., TE LSA
advertisement) is likely to be higher than that of a native
OSPF network. This is because the TE metrics may vary with each
TE circuit setup and the corresponding state change must be
advertised at the earliest, not exceeding the MinLSInterval
of 5 seconds. To minimize advertising repetitive content,
OSPF-xTE defines a new TE-incremental-Link-update LSA
(section 8.2) that would advertise just the TLVs that changed
for a link.
A new OSPFIGP-TE multicast address 224.0.0.24 may be used for
the exchange of TE compliant database descriptors during
database synchronization.
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 one of
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two types - native OSPF adjacency and TE adjacency. OSPF-xTE
routers will form both types of adjacency.
Two types of adjacency graphs are possible depending on whether
a Designated Router is elected for the network. On physical
point-to-point networks, Point-to-Multipoint networks and
Virtual links, neighboring routers become adjacent whenever they
can communicate directly. The adjacency can be one of
(a) TE-compliant or (b) native. In contrast, on broadcast and
NBMA networks the designated router and the backup designated
router may maintain two sets of adjacency. The remaining routers
will form either TE-compliant or native adjacency. In the
Broadcast network below, routers RT7 and RT3 are chosen as the
designated and backup routers respectively. Routers RT3, RT4
and RT7 are TE-compliant. RT5 and RT6 are not. So, RT4 will
have TE-compliant adjacency with the designated and backup
routers. RT5 and RT6 will only have native adjacency with the
designated and backup routers.
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Network Adjacency
+---+ +---+
|RT1|------------|RT2| o--------------------o
+---+ N1 +---+ RT1 RT2
RT7
o:::::
+---+ +---+ +---+ /| :
|RT7| |RT3| |RT4| / | :
+---+ +---+ +---+ / | :
| | | / | :
+-----------------------+ RT5o RT6o oRT4
| | N2 * * :
+---+ +---+ * * :
|RT5| |RT6| * * :
+---+ +---+ ** :
o:::::
RT3
Adjacency Legend:
----- Native adjacency (primary)
***** Native adjacency (Backup)
::::: TE-compliant adjacency (primary)
;;;;; TE-compliant adjacency (Backup)
Figure 6: The graph of adjacencies with TE-compliant routers.
8. TE LSAs for packet network
The 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.
LSA types 9 through 11 are defined in [OPAQUE].
Each LSA type has a unique flooding 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.
In the following subsections, we define new LSAs for traffic
engineering (TE) use. The Values for the new TE LSA types are
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assigned such that the high bit of the LSA-type octet is set
to 1. The new TE LSAs are largely modeled after the existing
LSAs for content format and have a unique flooding scope.
TE-router LSA is defined to advertise TE characteristics of
an OSPF-xTE router and all the TE-links attached to the
router. TE-incremental-Link-Update LSA is defined to
advertise incremental updates to the metrics of a TE link.
Flooding scope for both these LSAs is restricted to an area.
TE-Summary network and router LSAs are defined to advertise
the reachability of area-specific TE networks and Area 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.
TE-AS-external LSA and TE-Circuit-Path LSA are defined to
advertise AS external network reachability and pre-engineered
TE circuits respectively. While flooding scope for both these
LSAs can be the entire AS, flooding scope for the
pre-engineered TE circuit LSA may optionally be restricted to
just the TE topology within an area.
8.1. TE-Router LSA (0x81)
The TE-router LSA (0x81) is modeled after the router LSA and has the
same flooding scope as the router-LSA. However, the scope is
restricted to only the OSPF-xTE 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 described in 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 |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |
8.1.1. Router-TE flags - TE capabilities of the router
The following flags are used to describe the TE capabilities of an
OSPF-xTE router. The remaining bits of the 32-bit word are reserved
for future use.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|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
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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 LSP
MPLS Label switch TLV TE-NODE-TLV-MPLS-SWITCHING follows.
This is applicable only when the PSC flag is set.
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.
8.1.2. Router-TE TLVs
The following Router-TE TLVs are defined.
8.1.2.4. TE-NODE-TLV-MPLS-SWITCHING
MPLS switching TLV is applicable only for packet switched nodes. The
TLV specifies the MPLS packet switching capabilities of the 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 depth of label stack the node is capable of
processing on its ingress interfaces. An octet is used to represent
label depth. A default value of 1 is assumed when the TLV is not
listed. Label depth is relevant when an LER has to pop off multiple
labels off the MPLS stack.
'QOS' is a single octet field that may be assigned '1' or '0'. Nodes
supporting QOS are able to interpret the EXP bits in the MPLS header
to prioritize multiple classes of traffic through the same LSP.
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8.1.2.2. TE-NODE-TLV-MPLS-SIG-PROTOCOLS
MPLS signaling protocols TLV lists all the signaling protocol
supported by the node. An octet is used to list each signaling
protocol supported.
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 = 0x8002 | Length = 5, 6 or 7 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Protocol-1 | ... | .... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
RSVP-TE protocol is represented as 1, CR-LDP as 2 and 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 lists all the CSPF algorithm codes
supported. Support for CSPF algorithms makes the node eligible to
compute complete or partial circuit paths. Support for CSPF
algorithms can also be beneficial in knowing whether or not a node
is capable of expanding loose routes (in an MPLS signaling request)
into a detailed circuit path.
Two octets are used to list each CSPF algorithm code. The algorithm
codes may be vendor defined and unique within an Autonomous System.
If the node supports 'n' CSPF algorithms, 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 = 0x8003 | Length = 4(1 + (n+1)/2) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| CSPF-1 | .... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| CSPF-n | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
8.1.2.4. TE-NODE-TLV-NULL
When a TE-Router or a TE-link has multiple TLVs to describe the
metrics, the NULL TLV is used to terminate the TLV list.
0 1 2 3
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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 = 0x8888 | Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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8.1.3. Link-TE flags - TE capabilities of a 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| | | |D| |S|L|B|C|
|E|T|K| | | |B| |R|U|W|O|
| |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 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.
BW bit - One or more Link bandwidth TLVs follow
COL bit - Link Color TLV TE-LINK-TLV-COLOR follows.
8.1.4. Link-TE TLVs
8.1.4.1. TE-LINK-TLV-SRLG
The SRLG describes the list of Shared Risk Link Groups (SRLG) the
link belongs to. Two octets are used to list each SRLG. 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) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| SRLG-1 | .... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SRLG-n | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
8.1.4.2. TE-LINK-TLV-BANDWIDTH-MAX
The bandwidth TLV specifies maximum bandwidth of the link 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 = 8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Maximum 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 maximum link capacity expressed in
bandwidth units. Portions or all of this bandwidth may be used for
TE use.
8.1.4.3. TE-LINK-TLV-BANDWIDTH-MAX-FOR-TE
The bandwidth TLV specifies maximum bandwidth available for TE use
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 = 0x0003 | Length = 8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Maximum Bandwidth available for TE use |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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 available for TE use' is the total reservable
bandwidth on the link 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
be used for non-TE traffic in a mixed network.
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8.1.4.4. TE-LINK-TLV-BANDWIDTH-TE
The bandwidth TLV specifies the bandwidth reserved for TE 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 = 0x0004 | Length = 8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TE Bandwidth subscribed |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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.
'TE Bandwidth subscribed' is the bandwidth that is currently
subscribed from of the link. 'TE Bandwidth subscribed' must be less
than the 'Maximum bandwidth available for TE use'. New TE circuit
paths are able to claim no more than the difference between the
two bandwidths for reservation.
8.1.4.5. TE-LINK-TLV-LUG
The link usage cost TLV specifies Bandwidth unit usage cost,
TE circuit set-up cost, and any time constraints for 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 = 0x0005 | 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
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This 64-bit number specifies the time at or after which a
TE-circuit path may be set up on the 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.
8.1.4.6. TE-LINK-TLV-COLOR
The color TLV is similar to the SRLG TLV, in that an Autonomous
System may choose to issue colors to a TE-link meeting certain
criteria. The color TLV can be used to specify one or more colors
assigned to the link as follows. Two octets are used to list each
color. If the link belongs to 'n' number of colors, 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 = 0x0006 | Length = 4(1 + (n+1)/2) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Color-1 | .... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Color-n | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
8.1.4.7. TE-LINK-TLV-NULL
When a TE-link has multiple TLVs to describe its metrics, the NULL
TLV is used to terminate the TLV list. The TE-LINK-TLV-NULL is same
as the TE-NODE-TLV-NULL described in section 8.1.2.4
8.2. TE-incremental-link-Update LSA (0x8d)
A significant difference between a native OSPF network and a TE
network is that the latter may be subject to frequent real-time
circuit pinning and is likely to undergo TE-state updates. Some
links might undergo changes more frequently than others. Flooding
the network with TE-router LSAs at the aggregated speed of all
link metric changes is simply not desirable. A smaller in size,
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TE-incremental-link-update LSA is designed to advertise only the
incremental link updates.
TE-incremental-link-Update LSA will be advertised as frequently
as the link state is changed (not exceeding once every
MinLSInterval seconds). 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
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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 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.
8.3. TE-Circuit-path LSA (0x8C)
TE-Circuit-path LSA may be used to advertise the availability of
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 Duration cont.. | Circuit Setup time (Optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Circuit Setup time cont... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Circuit Setup time cont.. |Circuit Teardown time(Optional)|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| 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).
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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 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 set up. This field is specified only when the
S-bit is set in the TE-circuit-path flags. The 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 specifies the number of 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.
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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 befitting the
external areas are advertised.
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 TE parameters are not necessarily additive or
comparative. The parameters can be varied in their expression.
For example, a TE-summary network LSA will not summarize a
network whose links do not fall under an SRLG (Shared-Risk Link
Group). This way, the TE-summary LSA merely advertises the
reachability of TE networks within an area. The specific circuit
paths can be computed by the BDRs. Pre-engineered circuit paths
are advertised using TE-Circuit-path LSA (refer section 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) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| LS sequence number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS checksum | length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Network Mask |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Area-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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.
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 (ABR) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS sequence number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS checksum | length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0 |E|B| 0 | No. of Areas |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Area-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Router-TE flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Router-TE TLVs |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| .... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Link State ID
The ID of the Area border router or the AS border router whose
TE capability is being advertised.
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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, the
Area-ID lists all the areas the ABR belongs to. In the case
the link state ID is an ASBR, 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.
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. TE-AS-external LSAs are
originated by AS boundary routers with TE extensions, and describe
the TE networks and pre-engineered circuit paths external to the
AS. As with AS-external LSA, the flooding scope of the
TE-AS-external LSA is 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| 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. 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-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).
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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. TE LSAs for non-packet network
A non-packet network would use the TE LSAs described in the
previous section for a packet network with some variations.
These variations are described in the following subsections.
Two new LSAs, TE-Positional-ring-network LSA and TE-Router-Proxy
LSA are defined for use in non-packet TE networks.
Readers may refer to [SONET-SDH] for a detailed description of
the terms used in the context of SONET/SDH TDM networks,
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.
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 the case
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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. 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 ->|
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TDM, LSC, FSC bits
- Same as defined for router TE options.
9.2. TE-Positional-ring-network LSA (0x82)
Network LSA is adequate for packet TE networks. A new
TE-Positional-Ring-network-LSA is defined to represent type-5
link networks, found in non-packet networks such as SONET/SDH
TDM rings. A type-5 ring is a collection of network elements
(NEs) forming a closed loop. Each NE is connected to two
adjacent NEs via a duplex connection to provide redundancy
in the ring. The sequence in which the NEs are placed on the
Ring is pertinent. The NE that provides the OSPF-xTE
functionality is termed the Gateway Network Element (GNE).
The GNE selection criteria is outside the scope of this
document. The GNE is also termed the Designated Router for
the ring.
The TE-Positional-ring-network LSA (0x82) is modeled after the
network LSA and has the same flooding scope as the network-LSA
amongst the OSPF-xTE nodes within the area. Below is the format
of the TE-Positional-ring-network LSA. Unless specified
explicitly otherwise, the fields carry the same meaning as they
do in a network LSA. Only the differences are explained below.
TE-Positional-ring-network-LSA is originated for each
Positional-Ring type network in the area. The tuple of (Link
State ID, Network Mask) below uniquely represents a ring. The
TE option must be set in the Options flag while propagating
the 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 | 0x82 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link State ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertising Router |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS sequence number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS checksum | length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Network Mask |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Ring Type | Capacity Unit | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Ring capacity |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Network Element Node Id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |
Link State ID
This is the IP interface address of the network's Gateway
Network Element, which is also the designated router.
Advertising Router
Router ID of the network's Designated Router.
Ring type
There are 8 types of SONET/SDH rings defined as follows.
1 - A Unidirectional Line Switched 2-fiber ring (2-fiber ULSR)
2 - A bi-directional Line switched 2-fiber ring (2-fiber BLSR)
3 - A Unidirectional Path Switched 2-fiber ring (2-fiber UPSR)
4 - A bi-directional Path switched 2-fiber ring (2-fiber BPSR)
5 - A Unidirectional Line Switched 4-fiber ring (4-fiber ULSR)
6 - A bi-directional Line switched 4-fiber ring (4-fiber BLSR)
7 - A Unidirectional Path Switched 4-fiber ring (4-fiber UPSR)
8 - A bi-directional Path switched 4-fiber ring (4-fiber BPSR)
Capacity unit
Two units are defined at this time as follows.
1 - Synchronous Transport Signal (STS), which is the basic
signal rate for SONET signals. The rate of an STS signal
is 51.84 Mbps
2 - Synchronous Transport Multiplexer(STM), which is the
basic signal rate for SDH signals. The rate of an STM
signal is 155.52 Mbps
Ring capacity
Ring capacity expressed in number of Capacity units.
Network Element Node Id
The Router ID of each of the routers in the positional-ring
network. The list must start with the designated router as
the first element. The Network Elements (NEs) must be listed
in strict clockwise order as they appear on the ring,
starting with the Gateway Network Element (GNE). The number
of NEs in the ring can be deduced from the LSA header's
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length field.
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 |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |
10. Abstract topology representation with TE support
Below, we consider a TE network composed of three OSPF areas -
Area-1, Area-2 and Area-3, attached together through the backbone
area. Area-1 an has a single area border router, ABR-A1 and no
ASBRs. Area-2 has an area border router ABR-A2 and an AS border
router ASBR-S1. Area-3 has two area border routers ABR-A2 and
ABR-A3 and an AS border router ASBR-S2. The following network
also assumes a pre-engineered TE circuit path between ABR-A1
and ABR-A2; between ABR-A1 and ABR-A3; between ABR-A2 and
ASBR-S1; and between ABR-A3 and ASBR-S2.
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 and to the external ASes.
The abstraction also illustrates pre-engineered TE circuit
paths advertised by ABRs and ASBRs.
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+-------+
|Area-1 |
+-------+
+-------------+ |
|Reachable TE | +--------+
|networks in |-------| 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|------| ABR-A2 | | 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
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11. Changes to Data structures in OSPF-xTE nodes
11.1. Changes to Router data structure
An OSPF-xTE router must be able to include the router-TE
capabilities (as specified in section 8.1) in the router data
structure. OSPF-xTE 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 sets of Neighbors
Two sets of neighbor data structures 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 are part of the Native neighbors set.
11.3. Changes to Interface data structure
The following new fields are introduced to the interface data
structure.
TePermitted
If the value of the flag is TRUE, the interface 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 IP
packets. For FSC and LSC TE networks, this flag is set to
FALSE.
FloodingPermitted
If the value of the flag is TRUE, the interface may be used
for OSPF and OSPF-xTE packet exchange to synchronize the
LSDB across all adjacent neighbors. This is TRUE by default
to all NonTePermitted interfaces that are enabled for OSPF.
However, it is possible to set this to FALSE
for some of the interfaces.
TE-TLVs
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Each interface may define any number of 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 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 without
requiring the use of Hello protocol.
12. IANA Considerations
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
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
_________________________________________
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TE-Router LSA 0x81
TE-Positional-ring-network LSA 0x82
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. 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 TLVs. A TLV type
can range from 0x0001 through 0xFFFF. TLV type 0 is reserved
and unassigned. The following TLV 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-BANDWIDTH-MAX Section 8.1.4.2 0x0002
TE-LINK-TLV-BANDWIDTH-MAX-FOR-TE Section 8.1.4.3 0x0003
TE-LINK-TLV-BANDWIDTH-TE Section 8.1.4.4 0x0004
TE-LINK-TLV-LUG Section 8.1.4.5 0x0005
TE-LINK-TLV-COLOR Section 8.1.4.6 0x0006
TE-LINK-TLV-NULL Section 8.1.4.7 0x8888
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
TE-NODE-TLV-NULL Section 8.1.2.4 0x8888
13. Acknowledgements
The authors wish to specially thank Chitti Babu and his team
for implementing the protocol specified in a packet network
and verifying several portions of the specification in a
mixed packet network. The authors also wish to thank Vishwas
Manral, Riyad Hartani and Tricci So for their valuable
comments and feedback on the draft. Lastly, the authors wish
to thank Alex Zinin and Mike Shand for their draft (now
defunct) titled "Flooding optimizations in link state routing
protocols". The draft provided inspiration to the authors to
be sensitive to the high flooding rate, likely in TE networks.
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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 measures
applied to the native OSPF (refer [SEC-OSPF]) are directly
applicable to the TE LSAs described in the document. Discussed
below are the security considerations in processing TE LSAs.
Secure communication between OSPF-xTE nodes has a number of
components. Authorization, authentication, integrity and
confidentiality. Authorization refers to whether a particular
OSPF-xTE node is authorized to receive or propagate the TE LSAs
to its neighbors. Failing the authorization process might
indicate a resource theft attempt or unauthorized resource
advertisement. In either case, the OSPF-xTE nodes should take
proper measures to audit/log such attempts so as to alert the
administrator to take necessary action. OSPF-xTE 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-xTE LSAs can seriously
jeopardize the TE 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-xTE node and manipulate
the state, and the TE database including the topology and
metrics collected. This could potentially cause
denial-of-service on the TE network. Another consequence of not
authenticating is that an attacker could pose as OSPF-xTE
neighbor and respond in a manner that would divert TE data to the
attacker.
Integrity is required to ensure that an OSPF-xTE 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-xTE 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 LSAs are
accessible only to the authorized entities. When OSPF-xTE is
deployed in an untrusted environment, lack of confidentiality will
allow an intruder to perform traffic flow analysis and snoop the
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TE control network to monitor the traffic metrics and the rate at
which circuit paths are being setup and torn-down. The intruder
could cannibalize a lesser secure OSPF-xTE node and destroy or
compromise the state and TE-LDSB on the node. Needless to say, the
least secure OSPF-xTE will become the Achilles heel and make the
TE network vulnerable to security attacks.
15. Normative References
[IETF-STD] Bradner, S., "Key words for use in RFCs to indicate
Requirement Levels", BCP 14, RFC 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.
[OSPF-CAP] Lindem, A., Shen, N., Aggarwal, R., Schaffer, S., and
Vasseur, JP., "Extensions to OSPF for advertising
optional router capabilities",
draft-ietf-ospf-cap-04.txt (work in progress)
16. Informative References
[RSVP-TE] Awduche, D., L. Berger, D. Gan, T. Li, V. Srinivasan,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, IETF, December 2001
[CR-LDP] Jamoussi, B. et al, "Constraint-Based LSP Setup
using LDP", RFC 3212, January 2002.
[MOSPF] Moy, J., "Multicast Extensions to OSPF", RFC 1584,
March 1994.
[NSSA] P. Murphy, "The OSPF NSSA Option", RFC 3101, January
2003
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[OPAQUE] Coltun, R., "The OSPF Opaque LSA Option", RFC 2370,
July 1998.
[OPQLSA-TE] Katz, D., D. Yeung and K. Kompella, "Traffic
Engineering Extensions to OSPF", RFC 3630, September
2003.
[SONET-SDH] Ming-CHwan Chow, "Understanding SONET/SDH Standards
and Applications" - A paperback or bound book,
Published by Andan publisher.
[GMPLS-TE] L. Berger, "Generalized Multi Protocol Label
Switching (GMPLS) Signaling Functional Description",
RFC 3471, January 2003
17. Authors' Addresses
Pyda Srisuresh
Caymas Systems, Inc.
1179-A North McDowell Blvd.
Petaluma, CA 94954
U.S.A.
EMail: srisuresh@yahoo.com
Paul Joseph
Symbol Technologies
U.S.A.
EMail:
18. Full Copyright Statement
Copyright (C) The Internet Society (2004). This document is subject
to the rights, licenses and restrictions contained in BCP 78, and
except as set forth therein, the authors retain all their rights."
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
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