Canadian Patents Database / Patent 2299038 Summary

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(12) Patent: (11) CA 2299038
(54) English Title: MPLS APPLICATION TO OPTICAL CROSS CONNECT USING WAVELENGTH AS A LABEL
(54) French Title: APPLICATION MPLS D'INTERCONNEXION OPTIQUE UTILISANT LA LONGUEUR D'ONDE COMME ETIQUETTE
(51) International Patent Classification (IPC):
  • H04J 14/02 (2006.01)
  • H04B 10/27 (2013.01)
  • H04Q 11/00 (2006.01)
(72) Inventors :
  • ASHWOOD-SMITH, PETER J. (Canada)
(73) Owners :
  • CIENA LUXEMBOURG S.A.R.L. (Luxembourg)
(71) Applicants :
  • NORTEL NETWORKS CORPORATION (Canada)
(74) Agent: DANIELS IP SERVICES LTD.
(74) Associate agent:
(45) Issued: 2009-12-22
(22) Filed Date: 2000-02-21
(41) Open to Public Inspection: 2001-08-21
Examination requested: 2005-02-09
(30) Availability of licence: N/A
(30) Language of filing: English

English Abstract

A label switching routing protocol for establishing a datapath as a sequence of locally unique labels in an optical communications network, is provided. A wavelength on an optical cross-connect is considered as a label or one portion of a label. Timeslots may be assigned to designated wavelengths so as to form the second portion of the label. An optical time cross-connect (OTXC) capable of wavelength conversion from an input to an output interface creates the datapath based on wavelength to wavelength substitution, under the control of a multi-protocol label switching (MPLS) protocol.


French Abstract

Cette présentation porte sur un protocole de routage de commutation par étiquette pour établir un chemin de données en tant que séquence d'étiquettes localement unique dans un réseau de communication optique. Une longueur d'onde sur une interconnexion optique est considérée comme une étiquette ou une partie d'étiquette. Les intervalles de temps peuvent être assignés aux longueurs d'onde désignées de manière à former la deuxième partie de l'étiquette. Une interconnexion temporelle optique (OTXC) capable de faire la conversion d'une longueur d'onde à partir d'une entrée à une interface de sortie crée le chemin de données sur les bases de la substitution d'une longueur d'onde à une autre longueur d'onde, sous le contrôle d'un protocole de commutation multiprotocole par étiquette (MPLS).


Note: Claims are shown in the official language in which they were submitted.


We claim:


1. A label switching routing method for multi-protocol label switching (MPLS)
optical communications network, comprising:
establishing a datapath as a network of labels between a source and a sink in
said
optical communications network, wherein each label includes a wavelength field

containing a value of a wavelength frequency to be used for communication over
a
corresponding portion of the datapath associated with the label;
converting a first wavelength field of a first label to a second wavelength of
a
second label and forwarding the traffic to said sink according to said
datapath, including
updating sequence of labels to replace the first label with the second label;
and
transmitting said second wavelength label to said source.


2. A method as claimed in claim 1, wherein each label further includes a
timeslot
field storing a time value indicating one of a plurality to timeslots to be
used for
communication over the corresponding portion of the datapath associated with
the label.

3. A method as claimed in claim 2, wherein said plurality of timeslots are of
variable
size.


4. A method as claimed in claim 2, further comprising splitting said label
received at
an incoming interface into two outgoing composite labels.


5. A method as claimed in claim 2, further comprising combining two incoming
composite labels into one outgoing composite label.


6. A method as claimed in claim 1, wherein said step of establishing a
datapath is
controlled by a MPLS protocol.




7. The routing protocol of claim 6, further including a constrained routing
label
distribution protocol (CR-LDP) for hierarchically controlling time, frequency,
and
statistically multiplexed paths and forming said composite layer in a single
session.


8. An optical/time cross-connect (OTXC) for providing wavelength to wavelength

conversion in a multi-protocol label switching (MPLS) optical communications
network,
comprising:

means for providing a first label having a wavelength field for containing a
value
of a first wavelength frequency to be used for communication over a
corresponding
portion of a datapath associated with the label;

means for converting the value of the first wavelength frequency associated
with
an incoming signal of the OTXC into a value of a second wavelength frequency
associated with an outgoing signal of the OTXC;
means for updating a label associated with a communication path of the
incoming
signal to provide the value of the second wavelength frequency in the
wavelength field of
the label; and
means for forwarding the updated label to a source node.


9. The optical/time cross-connect of claim 8, wherein said means for
converting are
controlled by a MPLS protocol.


10. The optical/time cross-connect of claim 8, further including multiplexing
means
for providing statistical multiplexing, frequency division multiplexing, and
time division
multiplexing under the control of a MPLS protocol.


11. The optical/time cross-connect of claim 8, wherein said OTXC further
comprises
means for the assigning timeslots for a wavelength flowing back to the source
whenever
said wavelength arrives with an attached timeslot.


11


12. The optical/time cross-connect of claim 11, wherein said timeslots have a
variable
size in accordance with the speed of the optical carriers connected to a
signaling interface
of said OTXC, and the label requested at said signaling interface.


12

Note: Descriptions are shown in the official language in which they were submitted.


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MPLS APPLICATION TO OPTICAL CROSS-CONNECT USING
WAVELENGTH AS A LABEL

BACKGROUND OF THE INVENTION
Field of Invention

The present invention relates generally to optical communications
systems and particularly to label distribution protocols in an optical
transmission system using wavelength division multiplexing (WDM).
Related art

Optical networks include a plurality of optical transmission lines and
allow high bandwidth data communications. High speed data can be
modulated on light waves and transmitted through the optical network.
Wavelength division multiplexing (WDM) is a technique for modulating
different electrical data signals on distinct light wave carriers having
different
frequencies.

A wavelength is an end-to-end optical channel, or path of the same
frequency from source to destination across the optical network. However, in
practice, to achieve long reach and to avoid wavelength blocking, a
wavelength may change frequency through regeneration or wavelength
translation. The term "path" is understood to mean a set of links directly
connecting the port of one node to the port of another node. "End-to-end"
means from an end-router to another end-router.
The transport capacity required to accommodate the growth of
communications traffic is provided by optical links using dense wavelength
division multiplexing (DWDM) having increased capacity and longer reach. In
addition, optical cross-connect (OXC) switches are used in DWDM networks
as a platform for functional integration and network management.
In DWDM networks the main resource is the wavelength. For rapidly
setting up end-to-end connections signaling and routing protocols are used.
OXCs using wavelength routing and signaling protocols are considered fast
wavelength switches having more stringent speed, timing and control

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requirements compared to conventional OXCs, allowing fast end-to-end
connectivity.

Another requirement for DWDM networks is the ability to respond
quickly to unpredictable traffic intensities and patterns. The Optical
Internet is
developing towards the optical layer eventually being directly responsive to
the IP service layer according to changing traffic situations. To achieve a
unified packet and optical switched network architecture, standard routing
and signaling protocols may be adapted to the specific requirements of the
wavelength routed networks. Known standard signaling and routing protocols
are OSPF (open shortest path first), IS-IS (intermediate system - intermediate
system), PNNI (private network - network interface), and MPLS/LDP (multi-
protocol label switching / label distribution protocol). The signaling system
seven (SS7) used in voice networks may also be considered.
There is a need for an optical label switching (OLS) to provide a unified
routing protocol to control layer 1 and layer 2 hardware in an MPLS-enabled
IP network.

SUMMARY OF THE INVENTION
It is an object of the present invention to provide a new routing protocol
which alleviates totally or in part the drawbacks of the prior art.
It is another object of the present invention to broaden the MPLS
lambda (A) switching optical scope to additionally address the SONET
hierarchy by making the constrained routing LDP (CR-LDP) a common
connection oriented signaling protocol for time, frequency, and statistically
multiplexed paths.

Still, another object of the present invention is to apply an MPLS-Iike
approach to the optical switch to create an optical label switch where ~
represents the label , or a portion of the label to be distributed.
According to one aspect of the invention, a label substitution routing
protocol for establishing a datapath as a sequence of locally unique labels in
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an optical communications network, wherein each label is a wavelength
frequency, is provided. The wavelength may constitute a label, or one portion
of a label, while the second portion is formed by assigned timeslots.
According to another aspect of the invention, an optical cross-connect
(OXC) for creating a datapath in an optical communications network, is
provided. The OXC is capable of wavelength conversion from an input to an
output interface so as to provide wavelength to wavelength substitution along
the datapath, under the control of a MPLS protocol.
Advantageously, the invention allows one routing protocol to control
layer 1 and layer 2 hardware, and this greatly simplifies the network. It
brings
constrained based routing to the optical and time domains (where it
previously existed in the statistical domain), while performing routing at
light
speed.
The "Summary of the Invention" does not necessarily disclose all the
essential features for defining the invention which may reside in sub-
combinations of the disclosed features.

BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be now explained by way of example only and with
reference to the following drawings.
Figure 1 illustrates the principle of frequency to frequency routing
according to the invention;
Figure 2 illustrates A and time (T) labels independently managed by the
CR-LDP protocol;
Figures 3a and 3b illustrate the problem associated with cross-
connecting two optical paths having different transmission speeds;
Figure 4 illustrates wavelength mapping of a message carrying a
composite label;
Figure 5 illustrates the functions of an optical time cross-connect
(OTXC) according to the invention;

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Figure 6 illustrates wavelength mapping of a message in a optical
switch where the output and input speeds and framing are the same;
Figure 7 illustrates wavelength mapping in an optical switch where the
output speed is greater than the input speed, assuming SONET framing;
Figure 8 illustrates wavelength mapping in an optical switch similar to
the mapping of Figure 7 but for lower output and input speeds; and
Figure 9 illustrates wavelength mapping in an optical switch where the
output speed is smaller than the input speed.
Similar references are used throughout the description to denote
similar parts.

DESCRIPTION OF THE PREFERRED EMBODIMENTS
One of the many ways for routing an end-to-end routing in a
communications network is broadcasting. Broadcasting implies sending a
message from a source node to a destination node by sending the message
to all nodes in the network, without providing directions, and finally
stopping
when reaching the destination.
The routing of a message in a communications network can be
performed by the source node, or on a hop by hop basis. The source routing
provides a list of places where the packet should go which leads to the
destination. In a hop by hop routing, the packets are continuously asking for
directions at each node until reaching the destination.
Using the above techniques, one can imagine sending a messenger
ahead of the message to reserve capacity for the transmitted data, and for
distributing signs at each node indicating where the packet has to go. This is
a signaling protocol called the label substitution protocol (LSP) used with
the
asynchronous transmission mode (ATM). Examples of labels used with
various protocols are "DLCI" label that travels with the frame relay protocol,
"timeslot" for the time division multiplexing (TDM) protocol, or "LCN" for X25
protocol.

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The multi-protocol label switching (MPLS) is a signaling protocol
defined to setup, maintain, and release wavelength paths in an optical
network. Similar to the label distribution protocol (LDP), the MPLS treats
wavelengths as labels. The main function of the MPLS protocol is connection
management by wavelength grouping and mapping, or label banding,
according to combinations of: destination addresses, and type of service
(ToS) information. The ToS information may be provided according to optical
equivalence classes (FECs) and distributed with the label banding. The
MPLS protocol can also create various types of connections, one being the
explicit routed (ER) path as defined in the Constraint Routed LDP (CR-LDP).
The CR-LDP protocol is an efficient solution for core network traffic
engineering as regarding the quality of service (QoS) guarantees, path
optimization, and flexibility.
Figure 1 illustrates the principle of frequency to frequency routing
according to the invention. An optical label switch 10 comprises a A routing
control entity 12 and the photonic fabric 14 for connecting the ends of two or
more cables ending with connectors 16 - 19. Suppose that A, arriving on line
15 is to be frequency switched to line 13. The frequency to frequency
switching is mainly due to the fact that the input and output speeds of switch
10 are different, as it will be discussed later in connection with Figures 2a
and
2b. For routing purposes, \, is switched to '\2 using the frequency, or,\, as
a
label for the MPLS protocol to distribute across the network. It is to be
noted
that \ may constitute the entire label or just a portion of the label. No new
protocols are needed for further routing as the LDP protocol is used to setup
OSPF routes, and the CR-LDP protocol can engineer the traffic
Figures 2a and 2b illustrate the problem for cross-connecting two
optical paths having different transmission speeds as mentioned before. In
Figure 2a the problem for cross-connecting two optical paths having different
transmission speeds is illustrated. The optical cross-connect (OXC) 20 is a
slow provisioned wavelength switch with optical interfaces at typically SONET
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OC-48 or OC0192 rates with an electrical or optical core. The conventional
OXC 20 can not cross-connect line 22 which is an OC-48 to line 24 which is
an OC-192 unless the connection is performed at the lowest supported rate.
It is to be noted that having all optical paths running at the same speed is
not
possible as physical media differences may dictate lower speeds on certain
links. As shown, in Figure 2b, optical cross-connect (OXC) 20 can connect,
two transmission lines having same transmission speed like for example
optical carriers (OC-48) 22. This wastes 3xOC-48 or 7.5Gig for the example
of Figure 2b, which is an enormous amount of bandwidth
Figure 3 illustrates A and time (T) labels independently managed by the
CR-LDP protocol. The labels are considered in a hierarchy with the lambda
(A) labels on top of the timeslot (T) labels, which in turn are hierarchically
above the statistically multiplexed (SHIM) labels. The CR-LDP protocol
sessions will manage each level of the hierarchy independently.
Figure 4 illustrates wavelength mapping of a message carrying
wavelength and time as a single composite label (An; Tk_P). The CR-LDP
protocol is mapping the messages flowing from west to est on link 40 to carry
a label that consists of a wavelength (An) and optionally a set of timeslots
(Tk_P)
finally forming a single composite label label (An; Tk_p). However, it is
possible
to have a label that arrives on one link to be logically split into two labels
as it
flows back toward the source.
Arrow 41 represents a single mapping message in all examples. It is
also assumed that an Internet protocol (IP) like point to point protocol (PPP)
or transport communications protocol (TCP)channel is available for CR-
LDPlTCP/IP.
The MPLS protocol establishes a sequence of locally unique labels
and programms generic hardware such that the label on an input interface is
switched to another label on an outgoing interface. This is the pure label
switching. As discussed before, a wavelength on optical cross-connect can be
considered a label and therefore, any optical cross-connect capable of
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wavelength conversion from an input to an output interface can be controlled
by MPLS. Thus, according to the invention, an MPLS datapath being
wavelength to wavelength substitution is created. The optical cross-connect
also includes time division multiplexing equipment for providing statistically
multiplexed, frequency division multiplexed, and time division multiplexed
paths, under the control of said MPLS protocol.
Figure 5 illustrates the functions of an optical time cross-connect
(OTXC) according to the invention. Optical time cross-connect 50 receives
four wavelengths (A,...A4) as input on OC-48 carriers. The optical switch 50
performs pure optical cross-connect by mapping A, on link 42 to '\2 on link 44
as the two links have same transmission speed. Where the speeds do not
match, the CR-LDP protocol performs electrical/time sub wavelength
switching as for example the two wavelength with composite labels (A2; T48-
95),
and (A3; T0-23) from input links 44 and 45 to output link 46. The label of the
wavelength on link 46 include 1\3 and variable size timeslots (T0-47) and (T48-
,2)
are assigned forming a second portion of the label in this case. If the
wavelength has already a timesiot attached, as for example composite label
(A4; To) shown on line 47, the connection is performed by maintaining same
wavelength and assigning timesiots (To and T190).
Figure 6 illustrates wavelength mapping of a message in a optical
switch 20 where the output 24b and input 24a speeds and framing are the
same. In this case, the switch is pure optical, performing frequency to
frequency switching.
Figure 7 illustrates wavelength mapping in an optical switch where the
output speed OC-1 92, link 24, is greater than the input speed OC-48, link 22,
assuming SONET framing. A subset of timesiots are assigned for A, on
output 52 to all timeslots on input 54. Input 54 includes in this example four
OC-48, links 22a, 22b, 22c, 22d, propagating four mappings having four
wavelength and same assigned timeslots T0-47. The example of Figure
7 may represent four requests for OC-48 as the mappings flow back from link
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24 to links 22a to 22d.
Figure 8 illustrates a three label request, two for OC-12 and one for
OC-24, as the mappings flow back from OC-48, link 22. This case is similar
to the example of Figure 7 and also shows the timeslots allocation for link 58
(A3; r0_23) which is an OC-24 compared to links 56a (A1;ro_õ) or 56b (A2;
To_õ)
which have OC-12 rates.
Figure 9 illustrates wavelength mapping in an optical switch where the
output speed OC-24, links 58a and 58b, is smaller than the input speed OC-
48, link 22. In such a situation, multiple wavelengths/ timeslots must be
allocated. Suppose two composite labels (A,, A2; r0_23) arrive on links 58a
and
58b. This could represent for example a label request for OC-48 as the
mapping flows back through a DWDM of OC-24, links 58. Two OC-24 links,
or one OC-48 is required at the input side. The two wavelength labels (A,,
'\2;
T0_23) are mapped into one composite label (,\,; r0_47) on link 22.
A routing protocol for establishing a datapath as a sequence of locally
unique labels in an optical communications network, was described. The
wavelength on an optical cross-connect is considered as a label or one
portion of a label. Timeslots may be assigned to designated wavelengths so
as to form the second portion of the label. An optical time cross-connect
(OTXC) capable of wavelength conversion from an input to an output
interface creates the datapath based on wavelength to wavelength
substitution, under the control of a multi-protocol substitution label (MPLS)
protocol. The time division multiplexing equipment providing statistical
multiplexing, or time division multiplexing, or frequency division
multiplexing,
can also be programmed and controlled by the MPLS protocol. This greatly
simplifies the network by bringing constrained based routing to the optical
and
the time domain, thus making one protocol available for many layers of the
network.
Numerous modifications, variations, and adaptations may be made to
the particular examples of the invention without departing from the scope of
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the intention which is defined in the claims.

15
9

A single figure which represents the drawing illustrating the invention.

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Admin Status

Title Date
Forecasted Issue Date 2009-12-22
(22) Filed 2000-02-21
(41) Open to Public Inspection 2001-08-21
Examination Requested 2005-02-09
(45) Issued 2009-12-22

Abandonment History

There is no abandonment history.

Payment History

Fee Type Anniversary Year Due Date Amount Paid Paid Date
Filing $300.00 2000-02-21
Registration of Documents $100.00 2000-04-20
Maintenance Fee - Application - New Act 2 2002-02-21 $100.00 2002-02-11
Maintenance Fee - Application - New Act 3 2003-02-21 $100.00 2003-02-11
Maintenance Fee - Application - New Act 4 2004-02-23 $100.00 2004-02-02
Maintenance Fee - Application - New Act 5 2005-02-21 $200.00 2005-01-27
Request for Examination $800.00 2005-02-09
Maintenance Fee - Application - New Act 6 2006-02-21 $200.00 2006-01-25
Maintenance Fee - Application - New Act 7 2007-02-21 $200.00 2007-01-19
Maintenance Fee - Application - New Act 8 2008-02-21 $200.00 2008-01-18
Maintenance Fee - Application - New Act 9 2009-02-23 $200.00 2009-01-22
Final Fee $300.00 2009-09-16
Maintenance Fee - Patent - New Act 10 2010-02-22 $250.00 2010-01-20
Registration of Documents $100.00 2010-05-18
Maintenance Fee - Patent - New Act 11 2011-02-21 $450.00 2011-04-13
Maintenance Fee - Patent - New Act 12 2012-02-21 $250.00 2012-01-16
Maintenance Fee - Patent - New Act 13 2013-02-21 $250.00 2013-01-09
Maintenance Fee - Patent - New Act 14 2014-02-21 $250.00 2014-01-08
Maintenance Fee - Patent - New Act 15 2015-02-23 $450.00 2015-01-29
Maintenance Fee - Patent - New Act 16 2016-02-22 $450.00 2016-01-27
Maintenance Fee - Patent - New Act 17 2017-02-21 $450.00 2017-02-13
Maintenance Fee - Patent - New Act 18 2018-02-21 $450.00 2018-02-13
Maintenance Fee - Patent - New Act 19 2019-02-21 $450.00 2019-02-11
Current owners on record shown in alphabetical order.
Current Owners on Record
CIENA LUXEMBOURG S.A.R.L.
Past owners on record shown in alphabetical order.
Past Owners on Record
ASHWOOD-SMITH, PETER J.
NORTEL NETWORKS CORPORATION
NORTEL NETWORKS LIMITED
Past Owners that do not appear in the "Owners on Record" listing will appear in other documentation within the application.

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Abstract 2000-02-21 1 17
Description 2000-02-21 9 395
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Representative Drawing 2009-11-26 1 18
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