lee-pce-transporting-te-data-01.txt

Internet DRAFT - draft-lee-pce-transporting-te-data

draft-lee-pce-transporting-te-data

Last Version:	draft-lee-pce-transporting-te-data-01.txt	Tracker Entry
Date:	`25-Oct-2014`
Disposition:	expired
Previous Versions:	draft-lee-pce-transporting-te-data-00.txt (diff) - 03-Jul-2014

PCE Working Group Y. Lee
Internet Draft Huawei
Intended Status: Informational
H. Zheng
Huawei

October 24, 2014
Expires: January 2015

PCE in Support of Transporting Traffic Engineering Data

draft-lee-pce-transporting-te-data-01.txt

Abstract

In order to compute and provide optimal paths, Path Computation
Elements (PCEs) require an accurate and timely Traffic Engineering
Database (TED). Traditionally this TED has been obtained from a link
state routing protocol supporting traffic engineering extensions.
This document discusses possible alternatives and enhancements to
the existing approach to TED creation. This document gives
architectural alternatives for these alternatives and their
potential impacts on network nodes, routing protocols, and PCEP.

Status of this Memo

This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.

Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress.

This Internet-Draft will expire on April 24, 2015.

This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.

Lee & Zheng Expires January 24, 2015 [Page 1]

Internet-Draft PCE TED transport July 2014

Table of Contents

1. Introduction...................................................2
1.1. TED Creation and Maintenance via IGP-TEs..................5
2. Alternative TED Creation & Maintenance for a PCE...............6
2.1. Architecture Options......................................8
2.1.1. Nodes Send TE Info to all PCEs......................12
2.1.2. Nodes Send TE Info via an Intermediate System.......12
2.1.3. Nodes Send TE Info to At Least One PCE..............13
2.2. Nodes Finding PCEs.......................................13
2.3. Node TE Information Update Procedures....................14
2.4. PCE TED Maintenance Procedures...........................14
3. Standardization and Protocol Considerations...................15
3.1. Architecture Specific Standardization Aspects............16
4. Security Considerations.......................................16
5. IANA Considerations...........................................17
6. Conclusions...................................................17
7. Acknowledgments...............................................17
8. References....................................................17
8.1. Normative References.....................................17
8.2. Informative References...................................18
Author's Addresses...............................................19
Disclaimer of Validity...........................................20

1. Introduction

In Multiprotocol Label Switching (MPLS) and Generalized MPLS
(GMPLS), a Traffic Engineering Database (TED) is used in computing
paths for connection oriented packet services and for circuits. The
TED contains all relevant information that a Path Computation

Lee & Zheng Expires January 24, 2015 [Page 2]

Internet-Draft PCE TED transport July 2014

Element (PCE) needs to perform its computations. It is important
that the TED should be complete and accurate anytime so that the PCE
can perform path computations.

In MPLS and GMPLS networks, Interior Gateway routing Protocols
(IGPs) have been used to create and maintain a copy of the TED at
each node. One of the benefits of the PCE architecture [RFC4655] is
the use of computationally more sophisticated path computation
algorithms and the realization that these may need enhanced
processing power not necessarily available at each node
participating in an IGP.

Section 4.3 of [RFC4655] describes the potential load of the TED on
a network node and proposes an architecture where the TED is
maintained by the PCE rather than the network nodes. However it did
not describe how a PCE would obtain the information needed to
populate its TED. PCE may construct its TED by participating in the
IGP ([RFC3630] and [RFC5305] for MPLS-TE; [RFC4203] and [RFC5307]
for GMPLS). An alternative is offered by BGP-LS [I-D.ietf-idr-ls-
distribution].

In this document we propose approaches for creating and maintaining
the TED directly on a PCE as an alternative to IGPs and BGP
transport and investigate on the impact from the PCE, routing
protocol, and node perspective.

There are two main applicability of this alternative proposed by
this draft:

o Where there is no IGP-TE or BGP-LS running at the PCE to learn
TED.

o Where there is IGP-TE or BGP-LS running but with a need for a
faster TED population and convergence at the PCE.

* A PCE may receive partial information (say basic TE) from IGP-
TE and other information (optical and impairment) from PCEP.

* A PCE may receive full information from both IGP-TE and PCEP.

A PCC may further choose to send only local TE information or both
local and remote learned TED information. How a PCE manages the TED

Lee & Zheng Expires January 24, 2015 [Page 3]

Internet-Draft PCE TED transport July 2014

information is implementation specific and thus out of scope of this
document. PCEP extensions to support this idea is pursued in a
separate draft [PCEP-TE].

New application areas for GMPLS and PCE in optical transport
networks include Wavelength Switched Optical Networking (WSON) and
Optical Transport Networks (OTN). WSON scenarios can be divided into
routing wavelength assignment (RWA) problems where a PCE requires
detailed information about switching node asymmetries and wavelength
constraints as well as detailed up to date information on wavelength
usage per link [WSON-Frame]. As more data is anticipated to be made
available to PCE with addition of OTN [Reference] and Flex-grid
[Reference] and possible with some optical impairment data [WSON-
IMP-Info] even with the minimum set specified in [G.680], the total
amount of data requires significantly more information to be held in
the TED than is required for other traffic engineered networks.
Related to this issue published by [HWANG] indicated that long
convergence time and large number of LSAs flooded in the network
might cause scalability problems in OSPF-TE and impose limitations
on OSPF-TE applications.

In some circumstances such additional information could "bog down"
the routing protocols on the nodes from a data processing, a
storage, or communications perspective. In environments where PCEs
are external to the nodes running the routing protocol, and where
the information in the TED is not used by the switching nodes it
makes sense to investigate alternative methods to create and
maintain the TED at its place of use, i.e., the PCE.

Recent development of a stateful PCE Model [PCE-Initiated] changes
the PCE operation from path computation alone to include the support
of PCE-initiated LSPs. With a stateful PCE model, it is also noted
that LSP-DB is maintained by the PCE. For LSP state synchronization
of stateful PCEs in GMPLS networks, the LSP attributes, such as its
bandwidth, associated route as well as protection information etc,
should be updated by PCCs to PCE LSP database (LSP-DB) [S-PCE-GMPLS].
To support all these recent changes in a stateful PCE model, a
direct PCE interface to each PCC has to be supported. Relevant TED
information can also be transported from each node to PCE using this
PCC-PCE interface. Any resource changes in the node and links can
also be quickly updated to PCE using this interface. Convergence
time of IGP in GMPLS networks may not be quick enough to support on-
line dynamic connectivity required for some applications.

Lee & Zheng Expires January 24, 2015 [Page 4]

Internet-Draft PCE TED transport July 2014

This draft does not advocate that the alternative methods specified
in this draft should completely replace the IGP-TE as the method of
creating the TED. The split between the data to be distributed via
an IGP and the information conveyed via one of the alternatives in
this document depends on the nature of the network situation. One
could potentially choose to have some traffic engineering
information distributed via an IGP while other more specialized
traffic information is only conveyed to the PCEs via an alternative
interface discussed here. In addition, the methods specified in this
draft is only relevant to a set of architecture options where
routing decisions are wholly or partially made in the PCE.

However, the networks that do not support IGP-TE/BGP-LS, the method
proposed by this draft may be very relevant.

1.1. TED Creation and Maintenance via IGP-TEs

Routing protocols, in particular, IGP-TEs such as Open Shortest Path
First (OSPF) and Intermediate system to intermediate system (IS-IS),
take on a number of roles with respect to the control and data
planes for IP, MPLS, and GMPLS. In all three technology families
the underlying control plane communications technology is IP and
hence all utilize the IGPs ability to control and run the IP data
plane.

For the IP layer, the IGP directly establishes data plane
connectivity. In the MPLS and GMPLS cases separate signaling
protocols are used to directly control the data plane connectivity
and in these cases the prime purpose of the routing protocol is to
furnish network topology and resource status information used by
path computation algorithms on the nodes or PCEs. Hence in the IP
case the IGP is directly service impacting, while in the MPLS/GMPLS
case it is only indirectly service impacting.

The IP layer information and the MPLS/GMPLS data plane layer
information may be kept by the IGPs in two different information
stores. These are referred to as databases but are not necessarily
relational databases. In OSPF the information directly related to
IP connectivity (and hence the control communications plane for all
three technologies) and non-IP advertisements are kept in the link
state database (LSDB), while information related to traffic
engineering used by MPLS and GMPLS is kept in a (conceptually)
separate TED which can be considered a subset of the LSDB. This TED
information is distributed in a different data structure (Opaque LSA
[RFC5250]). When we talk about adding additional technology-specific
GMPLS information used for path computation we are only talking
about adding to the TED and not the IP portion of the LSDB.

Lee & Zheng Expires January 24, 2015 [Page 5]

Internet-Draft PCE TED transport July 2014

There are three main functions performed by an IGP: (a) hello
protocol, (b) database synchronization (with neighbors), (c)
database updates.

Table 1 Main Functions of an IGP for various technologies

The procedures for maintaining LSDBs and TEDs in IGP-TEs have been
very successful and well proven over time. These consist of:

1. Ageing the individual pieces of information in the TED
(including discarding them when the information gets too old)
to remove stale information from the TED.

2. Originator of the information being required to periodically
resend TED information to prevent it from being discarded.

3. Originator of the information sending updates of information as
needed, but subject to limits on how many/often these can be
sent to keep the TED up-to-date, but to avoid swamping the
network.

4. Reliable method for getting this information to other peers
(flooding) to ensure that the information is delivered to all
participants.

5. An efficient database synchronization mechanism for sharing
info with a newly established peer.

2. Alternative TED Creation & Maintenance for a PCE

Given that nodes, by their position and role in the network, have
accurate traffic engineering information concerning their local link
ends and switching properties, it seems natural that, if other nodes
in the network cannot make use of this information or do not want

Lee & Zheng Expires January 24, 2015 [Page 6]

Internet-Draft PCE TED transport July 2014

it, the information should only be conveyed to interested PCEs. In
such case the flooding of TE information to all nodes may not be
very efficient in terms of memory, CPU, bandwidth, etc.

In addition, one could potentially choose to have some traffic
engineering information distributed via an IGP-TE protocol while
other more specialized traffic information is only conveyed to the
PCEs. For example, it makes sense to distribute "static" (rarely
modified) and sizable data (e.g., NE switching asymmetry structure)
via methods other than IGP-TE while more frequently changed data via
IGP-TE. This could significantly decrease the IGP-TE information and
its footprint on all nodes.

The benefits of such an approach include:

o Node: reduced storage demands (doesn't keep the entire TED)

o Node: reduced processing demands for TED updates and
synchronization

o Control Plane: reduced overall communication demands since the
TED is not being updated and maintained on all nodes in the
network.

o PCE: More timely TED updates are possible.

o Information distribution constraints, such as seen in [Imp-Frame]
can be met.

To quantify the previous advantages requires a bit more detail on
how such an approach could actually be accomplished. The key pieces
needed to implement such an approach include:

o Multiple PCEs must be supported for robustness and load sharing.

o Nodes must be able to find a PCE to which to send their traffic
engineering information.

o Nodes must have procedures and a mechanism (protocols) with which
to communicate their TE information to a PCE. PCEs must have
procedures and a mechanism (protocols) with which to receive this
TE information from nodes.

o Efficient mechanisms must exist in the multi-PCE case to ensure
all PCEs have the same TED.

Lee & Zheng Expires January 24, 2015 [Page 7]

Internet-Draft PCE TED transport July 2014

The advantages of using an alternative to IGP-TE comes at the cost
of:

o Additional protocols to be configured and secured. Recall that we
still must have an IP IGP for control plane communications.

o Any new protocols/implementations for alternative TED creation
still must support many IGP-TE like features such as removal of
stale information, reliable delivery of updates to all
participants, recovery after reboots/crashes/upgrades, etc. It
should also work along with IGP-TE/BGP-LS TED mechanism with some
information in the TED received from existing mechanisms.

o Mechanisms to discover PCEs that are capable and willing to
accept direct TED updates.

2.1. Architecture Options

There are three general architectural alternatives based on how
nodes get their local TED information to the PCEs: (1) Nodes send
local information to all PCEs; (2) Nodes send local information to
an intermediate server that will send to all PCEs; (3) Nodes send
local information to at least one PCE and have the PCEs share this
information with each other. An important functionality that needs
to be addressed in each of these approaches is how a new PCE gets
initialized in a reasonably timely fashion.

Figures 1-3 show examples of three options for nodes to share local
TED information with multiple PCEs. As in the IGP case we assume
that switching nodes know their local properties and state including
the state of all their local links. In these figures the data plane
links are shown with the character "o"; TE information flow from
nodes to PCE by the characters "|", "-", "/", or "\"; and PCE to PCE
TE information, if any, by the character "i".

Lee & Zheng Expires January 24, 2015 [Page 8]

Internet-Draft PCE TED transport July 2014

---- ----
// \\ // \\
/ \ / \
| PCE \ | PCE |
| |\ / |
| X \ / \ /
|\\ // \ \ / /|\ /X
| --+-\ \ \ /// | -+-- \
| | \\ \ \\ // | | \
| | \\ \ // | | \
| | \\ \ / | | \
| | \ \\ \// | | \
| | \ \\ /\/ | | \
| | \ /X\/\ | | \
| | \ / /\ \ | | \
| | X/ / \\\ | | \
| | / \ / \\ | | \
| | // \ / \\| | \
| | / X \\\ | \
| | // /\ |\\\\| \
| +----+-/-+ / \ |+-\-|----+ \
| | | / \ || | \
| | N1 ooooooooooooooooooo N2 oo \
| | ooooooooooooooooooo ooo \
| | | / \ | | |ooo \
| +---oo---+/ \ | +------\-+ ooo \
| ooo / \ | \ ooo \
| ooo / \ | \ ooo \
| oo / * \ | \ ooo \
| oo / \ | \ ooo \
| ooo / \ | \\ ooo \
| oo / * \ \ ooo \
| ooo / \ \ ooo \
| oo / |\ \ ooo\
++--oo-/-+ |\ * \+---oo-\-+
| | | \ \ |
| oooo | \ oooo Nn |
| N3 ooooooooo +-+---\--+ ooooooooo |
| | ooooooooo | | oooooooooo | |
+--------+ oooooooo N4 oooooooo +--------+
oooo oooo
| |
+--------+
Figure 1 . Nodes send local TE information directly to all PCEs

Lee & Zheng Expires January 24, 2015 [Page 9]

Internet-Draft PCE TED transport July 2014

---- ---- ----
// \\ // \\ // \\
/ \ / \ / \
| PCE | | PCE | | PCE |
| | | | | |
\ -- \ / \ /
\\ // -- \\ // --\\ //
---- --- /--- ---- ----
-- / ----
--- / ---
-- --/- ----
--/ \\ ----
/ --
| Pub/ |
-+ Sub |
--- X ---
-- / \\ // ----
+--- / -+--\ ----+
+-----+--+ / | \ +--+-----+
| | / | \\ | |
| N1 ooooooooooooooooooooooooo N2 oooo
| ooooooooooooooooooooooooo oooo
| | / | \\ | | oo
+---oo---+ / | \+--------+ oo
oo / | \ oo
oo / | \ oo
oo / | \\ oo
oo / | \ oo
oo / * | \ oo
oo / | \ oo
oo / | \\ oo
oo / *| \ oo
oo / | \ oo
oo / | \\ oo
+---oo-/-+ | * \+---oo---+
| | | \ |
| oooo | oooo Nn |
| N3 oooooooo +---+----+ ooooooooo |
| | oooooo | | ooooooooooo | |
+--------+ oooooooo N4 ooooooooo +--------+
ooooo oooo
| |
+--------+

Figure 2 . Nodes send local TE information to PCEs via an
intermediary (publish/subscribe)server

Lee & Zheng Expires January 24, 2015 [Page 10]

Internet-Draft PCE TED transport July 2014

Figure 3 . Nodes send local TE information to at least one PCE and
have the PCEs share TED information

Lee & Zheng Expires January 24, 2015 [Page 11]

Internet-Draft PCE TED transport July 2014

2.1.1. Nodes Send TE Info to all PCEs

Architectural alternative 1 shown in Figure 1, illustrates nodes
sending their local TE information to all PCEs within their domain.
As the number of PCEs grows we have scalability concerns. However,
if we are only talking about 2-3 PCEs, then we do not have this
scalability concern. In particular each node needs to keep track of
which PCE it has sent information to and update that information
periodically.

If a new PCE is added to the domain the node must send all its local
TED information to that PCE rather than just sending status updates.

2.1.2. Nodes Send TE Info via an Intermediate System

Architecture alternative 2 is shown in Figure 2. This architecture
reduces the burden on switching nodes by having the nodes send TE
information to an intermediate system. This general approach is
typically described in the software literature as a
publish/subscribe paradigm. Here the nodes send their local TED
information to an intermediate entity whose job is to insure that
all PCEs receive this information. The nodes in this case being the
publishers of the information and the PCEs the subscribers of the
information. Publish/subscribe functionality can be found in general
messaging oriented middleware such as the Java Messaging Service
[JMS] and many others. A routing specific example of this approach
is seen in BGP route reflectors [RFC4456].

Note that the publish/subscribe entity can be collocated with a PCE.
This would then looks like a master/slave type system architecture.

If a new PCE is added then the intermediate server will need to work
with this new PCE to initialize its TED. Hence the publish/subscribe
entity will need to also keep a copy of the entire TED and for
reliability purposes a redundant server would be required. The
publish/subscribe entity itself can be a PCE.

Architecture alternative 2 could be useful when there are a number
of PCEs in the network and as such there is the scaling issue with
each of the NEs talking to all the PCEs. The advantage of this
alternative would diminish when we are dealing only with only a few
PCEs.

Lee & Zheng Expires January 24, 2015 [Page 12]

Internet-Draft PCE TED transport July 2014

2.1.3. Nodes Send TE Info to At Least One PCE

In this architectural alternative, shown in Figure 3, each node
would be associated with at least one PCE. This implies that each
PCE will only have partial TED information directly from the nodes.
It would be the responsibility of a node to get its local TED
information to its associated PCE, then the PCEs within a domain
would then need to share the partial TED information they learned
from their associated nodes with each other so that they can create
and maintain the complete TED. As we have seen in section 1.1. this
is very similar to part of the functionality provided by a link
state protocol, but in this case the protocol would be used between
PCEs so that they can share the information they have obtained from
their associated switching nodes (rather than from attached links as
in a regular link state protocol). To allow for this sharing of
information PCEs would need to peer with each other. PCE discovery
extensions [RFC4674] could be used to allow PCEs to find other PCEs.
If a new PCE is added to the domain it would need to peer with at
least one other PCE and then link state protocol procedures for TED
synchronization could then be used to initialize the new PCEs TED.

A number of approaches can be used to ensure control plane
resilience in this architecture. (1) Each node can be configured
with a primary and a secondary PCE to send its information to; In
case of failure of communications with the primary PCE the node
would send its information to a secondary PCE (warm standby). (2)
Each node could be configured to send its information to two
different PCEs (hot standby).

2.2. Nodes Finding PCEs

In cases 1 and 3 nodes need to send TE information directly to PCEs.
Path Computation Clients (PCCs) and network nodes participating in
an IGP (with or without TE extensions) have a mechanism to discover
a PCE and its capabilities. [RFC4674] outlines the general
requirements for this mechanism and extensions have been defined to
provide information so that PCCs can obtain key details about
available PCEs in OSPF [RFC5088] and in IS-IS [RFC5089].

After finding candidate PCEs, a node would need to see which if any
of the PCEs actually want to receive TE information directly from
this node.

In architectural alternative 2 (publish/subscribe) the location of
intermediate system would either need to be configured or PCE
discovery could be extended so that a when a node asks a PCE if it

Lee & Zheng Expires January 24, 2015 [Page 13]

Internet-Draft PCE TED transport July 2014

wants to hear TE info the PCE points it to the intermediate
publish/subscribe system.

2.3. Node TE Information Update Procedures

First a node must establish an association between itself and a PCE
or intermediate system that will be maintaining a TED. It is the
responsibility of the node to share TE information concerning its
local environment, e.g., links and node properties. General and
technology specific information models would specify the content of
this information while the specific protocols would determine the
format. Note that a node would not be sending to the PCE information
it might be passed from neighbor nodes. Note that data plane
neighbor information would be passed to the PCE embedded in TE link
information.

There will be cases where the node would have to send to the PCE
only a subset of TE link information depending on the path
computation option. For instance, if the node is responsible for
routing while the PCE is responsible for wavelength assignment for
the route, the node would only need to send the PCE the WSON link
usage information. This path computation option is referred to as
separate Fouting (R) and Wavelength Assignment (WA) option in [PCE-
WSON].

2.4. PCE TED Maintenance Procedures

The PCE is responsible for creating and maintaining the TED that it
will use. Key functions include:

1. Establishing and authenticating communications between the PCE
and sources of TED information.

2. Timely updates of the TED with information received from nodes,
peers or other entities.

3. Verifying the validity of information in the TED,i.e., ensure
that the network information obtained from nodes or elsewhere
is relatively timely, or not stale. By analogy with similar
functionality provided by IGPs this can be done via a process
where discrete "chunks" of TED information are "aged" and
discard when expired. This combined with nodes periodically
resending their local TE information leads to a timely TED.

Lee & Zheng Expires January 24, 2015 [Page 14]

Internet-Draft PCE TED transport July 2014

3. Standardization and Protocol Considerations

In the previous section we examined a number of architectural
alternatives for TED creation and maintenance between PCE(s) and the
network. Here we examine aspects of these alternatives that could be
suitable for standardization. First there are a number of functions
which are independent of the particular architectural alternatives,
these include:

o An information model for the TED

o Basic PCE TED creation and maintenance procedures

o Information packaging for use in TED creation, maintenance and
exchange

o NE to PCE (or Pub/Sub) communication of TED information ---
interface and protocol (e.g. PCEP)

o NEs discovering PCE (or Pub/Sub) for TED creation and maintenance
purposes

By the "information model" for the TED we mean the raw information
that a path computation algorithm would work with somewhat
independent of how it might be packaged for TED maintenance and
creation. Initial efforts along these lines have started at CCAMP
for wavelength switched optical networks for non-impairment RWA
[WSON-Info] and impairment aware RWA [WSON-IMP-Info].

Given a TED information model if we can agree on basic PCE TED
creation and maintenance procedures we can then come up with a
standardized way to package the information for use in such
procedures. The analogy here is with an IGPs database maintenance
procedures such as aging and the packaging of link state information
information into LSA (link state advertisements). LSAs form the
basic chunks of an IGP's database. OSPF LSAs include an age field to
assist in the ageing procedure and also has an advertising router
field that aids in redistribution decisions, i.e., flooding. However
the detailed TE information is encoded in LSAs via type length value
(TLV) structures and it is this information that is used in path
computation.

From there we could standardize the interface between a NE and a PCE
for communication of TE information. This interface includes NE and
PCE behaviors as well as a communications protocol.

Lee & Zheng Expires January 24, 2015 [Page 15]

Internet-Draft PCE TED transport July 2014

Finally for the common behaviors we need a way for the NEs to find
the PCEs or an intermediate publish/subscribe system to which they
will send their TE information. As was previously pointed out this
could be based on small enhancements to existing PCE discovery
mechanisms.

3.1. Architecture Specific Standardization Aspects

Case 1: NEs send to all PCEs

This case has commonalities with both cases 2 and 3 and does not
appear to have unique standardization aspects. As pointed out in
section 2.1. We do need to consider when a new PCE comes online.

Case 2: Publish/Subscribe Server

In this case we would need to additionally standardize

1. how a new PCE coming online synchronizes with the
publish/subscribe server

1. how PCEs and publish subscribe server communicate

2. Redundancy for publish subscribe server

Case 3: PCE to PCE sharing TE information learned from NEs

Here we would need the following additional mechanisms standardized:

1. The PCE to PCE interface and protocol

2. The method for PCEs to discover PCEs for the purpose of TE
information sharing

3. PCE to PCE association for information sharing, in particular
sharing update information.

4. Security Considerations

This draft discusses an alternative technique for PCEs to build and
maintain a traffic engineering database. In this approach network
nodes would directly send traffic engineering information to a PCE.
It may be desirable to protect such information from disclosure to
unauthorized parties in addition it may be desirable to protect such
communications from interference (modification) since they can be
critical to the operation of the network. In particular, this
information is the same or similar to that which would be

Lee & Zheng Expires January 24, 2015 [Page 16]

Internet-Draft PCE TED transport July 2014

disseminated via a link state routing protocol with traffic
engineering extensions.

5. IANA Considerations

This version of this document does not introduce any items for IANA
to consider.

6. Conclusions

This document introduced several alternative architectures for PCEs
to create and maintain a traffic engineering database (TED) via
information directly or indirectly received from network elements
and identified common aspects of these approaches. The TED is a
critical piece of the overall PCE architecture since without it path
computations cannot proceed. Though not explicitly out of scope the
PCE working group does not have a work item or study item devoted to
TED creation and maintenance. Such a work item can lead to enhanced
interoperability and simplicity of PCE implementations. This
document identified several common areas within these alternatives
that could be standardized. In addition, the alternative approaches
to TED creation and maintenance discussed here offloads both the
network nodes and routing protocols from either some or all TED
creation and maintenance duties at the same time it does not add
significant new processing to a PCE that has already been
participating in IGP based TED creation and maintenance.

7. Acknowledgments

We would like to thank Adrian Farrel for his useful comments and
suggestions.

8. References

8.1. Normative References

[RFC4655] Farrel, A., Vasseur, J.-P., and J. Ash, "A Path
Computation Element (PCE)-Based Architecture", RFC 4655,
August 2006.

[RFC4674] Le Roux, J., Ed., "Requirements for Path Computation
Element (PCE) Discovery", RFC 4674, October 2006.

[RFC5088] Le Roux, JL., Ed., Vasseur, JP., Ed., Ikejiri, Y., and R.
Zhang, "OSPF Protocol Extensions for Path Computation
Element (PCE) Discovery", RFC 5088, January 2008.

Lee & Zheng Expires January 24, 2015 [Page 17]

Internet-Draft PCE TED transport July 2014

[RFC5089] Le Roux, JL., Ed., Vasseur, JP., Ed., Ikejiri, Y., and R.
Zhang, "IS-IS Protocol Extensions for Path Computation
Element (PCE) Discovery", RFC 5089, January 2008.

[RFC5250] Berger, L., Bryskin, I., Zinin, A., and R. Coltun, "The
OSPF Opaque LSA Option", RFC 5250, July 2008.

8.2. Informative References

[JMS] Java Message Service, Version 1.1, April 2002, Sun
Microsystems.

[PCE-Initiated] E. Crabbe, et. al., "PCEP Extensions for PCE-
initiated LSP Setup in a Stateful PCE Model", draft-ietf-
pce-pce-initiated-lsp, work in progress.

[S-PCE-GMPLS] X. Zhang, et. al, "Path Computation Element (PCE)
Protocol Extensions for Stateful PCE Usage in GMPLS-
controlled Networks", draft-ietf-pce-pcep-stateful-pce-
gmpls, work in progress.

[PCE-WSON] Y. Lee, G. Bernstein, "PCEP Requirements for the
support of Wavelength Switched Optical Networks (WSON)",
work in progress, draft-lee-pce-wson-routing-wavelength-
05.txt, February 2009.

[RFC4456] Bates, T., Chen, E., and R. Chandra, "BGP Route
Reflection: An Alternative to Full Mesh Internal BGP
(IBGP)", RFC 4456, April 2006.

[Imp-Frame] G. Bernstein, Y. Lee, D. Li, A Framework for the Control
and Measurement of Wavelength Switched Optical Networks
(WSON) with Impairments, Work in Progress, October 2008.

[WSON-Frame] Y. Lee, G. Bernstein, W. Imajuku, "Framework for
GMPLS and PCE Control of Wavelength Switched Optical
Networks", work in progress: draft-ietf-ccamp-wavelength-
switched-framework.

[PCEP-TE] D. Dhody, Y. Lee, "PCEP Extension for Transporting TE
Data", work in progress: draft-dhodylee-pce-pcep-te-data-
extn.

[WSON-IMP-Info] Y. Lee, G. Bernstein, "Information Model for
Impaired Optical Path Validation", work in progress:
draft-bernstein-wson-impairment-info-02.txt, March 2009.

Lee & Zheng Expires January 24, 2015 [Page 18]

Internet-Draft PCE TED transport July 2014

[HWANG] S. Hwang, et al, "An Experimental Analysis on OSPF-TE
Convergence Time", Proc. SPIE 7137, Network Architectures,
Management, and Applications, November 19, 2008.

Author's Addresses

Young Lee
Huawei Technologies
5340 Legacy Drive, Building 3
Plano, TX 75023, USA

Phone: (469) 277-5838
Email: leeyoung@huawei.com

Haomian Zheng
Huawei Technologies Co., Ltd.
F3-1-B R&D Center, Huawei Base,
Bantian, Longgang District
Shenzhen 518129 P.R.China

Phone: +86-755-28979835
Email: zhenghaomian@huawei.com

Lee & Zheng Expires January 24, 2015 [Page 19]

Internet-Draft PCE TED transport July 2014

Contributor's Addresses

Dhruv Dhody
Huawei Technologies
Leela Palace
Bangalore, Karnataka 560008
India

EMail: dhruv.ietf@gmail.com

Xian Zhang
Huawei Technologies Co., Ltd.
F3-1-B R&D Center, Huawei Base,
Bantian, Longgang District
Shenzhen 518129 P.R.China

Phone: +86-755-28979835
Email: zhangxian@huawei.com

Disclaimer of Validity

All IETF Documents and the information contained therein are
provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION
HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY,
THE IETF TRUST 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 THEREIN WILL NOT INFRINGE
ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS
FOR A PARTICULAR PURPOSE.

Acknowledgment

Funding for the RFC Editor function is currently provided by the
Internet Society.

Lee & Zheng Expires January 24, 2015 [Page 20]