CA2299038C - Mpls application to optical cross connect using wavelength as a label - Google Patents
Mpls application to optical cross connect using wavelength as a label Download PDFInfo
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- CA2299038C CA2299038C CA 2299038 CA2299038A CA2299038C CA 2299038 C CA2299038 C CA 2299038C CA 2299038 CA2299038 CA 2299038 CA 2299038 A CA2299038 A CA 2299038A CA 2299038 C CA2299038 C CA 2299038C
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04Q—SELECTING
- H04Q11/00—Selecting arrangements for multiplex systems
- H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
- H04Q11/0062—Network aspects
- H04Q11/0066—Provisions for optical burst or packet networks
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J14/00—Optical multiplex systems
- H04J14/02—Wavelength-division multiplex systems
- H04J14/0227—Operation, administration, maintenance or provisioning [OAMP] of WDM networks, e.g. media access, routing or wavelength allocation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J14/00—Optical multiplex systems
- H04J14/02—Wavelength-division multiplex systems
- H04J14/0227—Operation, administration, maintenance or provisioning [OAMP] of WDM networks, e.g. media access, routing or wavelength allocation
- H04J14/0228—Wavelength allocation for communications one-to-all, e.g. broadcasting wavelengths
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J14/00—Optical multiplex systems
- H04J14/02—Wavelength-division multiplex systems
- H04J14/0278—WDM optical network architectures
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04Q—SELECTING
- H04Q11/00—Selecting arrangements for multiplex systems
- H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
- H04Q11/0005—Switch and router aspects
- H04Q2011/0007—Construction
- H04Q2011/0033—Construction using time division switching
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04Q—SELECTING
- H04Q11/00—Selecting arrangements for multiplex systems
- H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
- H04Q11/0062—Network aspects
- H04Q2011/0077—Labelling aspects, e.g. multiprotocol label switching [MPLS], G-MPLS, MPAS
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.
Description
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 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
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 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
2 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;
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;
3 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.
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.
4 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
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
5 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
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
6 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
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 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
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
8 the intention which is defined in the claims.
9
Claims (12)
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.
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.
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.
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.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2299038 CA2299038C (en) | 2000-02-21 | 2000-02-21 | Mpls application to optical cross connect using wavelength as a label |
| US09/536,020 US7031607B1 (en) | 2000-02-21 | 2000-03-27 | MPLS application to optical cross-connect using wavelength as a label |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2299038 CA2299038C (en) | 2000-02-21 | 2000-02-21 | Mpls application to optical cross connect using wavelength as a label |
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| Publication Number | Publication Date |
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| CA2299038A1 CA2299038A1 (en) | 2001-08-21 |
| CA2299038C true CA2299038C (en) | 2009-12-22 |
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| CA 2299038 Expired - Lifetime CA2299038C (en) | 2000-02-21 | 2000-02-21 | Mpls application to optical cross connect using wavelength as a label |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| EP1436945B1 (en) * | 2001-09-03 | 2008-07-30 | Tpack A/S | Telecommunication network comprising an sdh/sonet-subnet, where the gmpls function is incorporated in a gmpls software server |
| EP1555548A1 (en) | 2004-01-16 | 2005-07-20 | IDT Technology Limited | Weather station |
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