EP2524457A1 - Routage dans un réseau à couches optique et électrique - Google Patents

Routage dans un réseau à couches optique et électrique

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Publication number
EP2524457A1
EP2524457A1 EP10702145A EP10702145A EP2524457A1 EP 2524457 A1 EP2524457 A1 EP 2524457A1 EP 10702145 A EP10702145 A EP 10702145A EP 10702145 A EP10702145 A EP 10702145A EP 2524457 A1 EP2524457 A1 EP 2524457A1
Authority
EP
European Patent Office
Prior art keywords
optical
nodes
links
network
routing
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP10702145A
Other languages
German (de)
English (en)
Inventor
Paola Iovanna
Giulio Bottari
Gianpaolo Oriolo
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Telefonaktiebolaget LM Ericsson AB
Original Assignee
Telefonaktiebolaget LM Ericsson AB
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Telefonaktiebolaget LM Ericsson AB filed Critical Telefonaktiebolaget LM Ericsson AB
Priority to EP10702145A priority Critical patent/EP2524457A1/fr
Publication of EP2524457A1 publication Critical patent/EP2524457A1/fr
Withdrawn legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L41/00—Arrangements for maintenance, administration or management of data switching networks, e.g. of packet switching networks
    • H04L41/12—Discovery or management of network topologies
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L45/00—Routing or path finding of packets in data switching networks
    • H04L45/58—Association of routers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L45/00—Routing or path finding of packets in data switching networks
    • H04L45/62—Wavelength based
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L45/00—Routing or path finding of packets in data switching networks
    • H04L45/64—Routing or path finding of packets in data switching networks using an overlay routing layer
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L41/00—Arrangements for maintenance, administration or management of data switching networks, e.g. of packet switching networks
    • H04L41/12—Discovery or management of network topologies
    • H04L41/122—Discovery or management of network topologies of virtualised topologies, e.g. software-defined networks [SDN] or network function virtualisation [NFV]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L41/00—Arrangements for maintenance, administration or management of data switching networks, e.g. of packet switching networks
    • H04L41/40—Arrangements for maintenance, administration or management of data switching networks, e.g. of packet switching networks using virtualisation of network functions or resources, e.g. SDN or NFV entities
    • 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
    • H04Q11/0071—Provisions for the electrical-optical layer interface
    • 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
    • H04Q2011/0073—Provisions for forwarding or routing, e.g. lookup tables
    • 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
    • H04Q2011/0086—Network resource allocation, dimensioning or optimisation

Definitions

  • This invention relates to methods of routing traffic across a network, to methods of operating a node of a network, to a network management system for a network, and to corresponding computer programs for such methods and apparatus.
  • the first group involves multi-layer solutions where the optical layer is composed by nodes with full wavelength conversion capability
  • the second group provides solutions that deal with all optical networks but without integration with packet layer
  • This last group includes both off-line provisioning, and with on-line routing of new traffic in a live network.
  • Multi-layer routing is a very complex task because the different layers tend to use heterogeneous technologies which have different constraints. Moreover this task is more complex when one of the two layers is all-optical.
  • One of the critical problems to address routing (R) in case of all optical networks is due to the fact that such networks require considering a set of issues such as wavelength assignment (WA) and physical impairment validation (IV).
  • optical nodes can be contained in several matrices representing the connectivity of a node, the switching connectivity matrix, the wavelength conversion matrix, and so on.
  • the following issues arise:
  • optical nodes have peculiar features (direction, color, transponder type, available wavelengths, etc..) that are different with respect packet nodes (in general not optical nodes);
  • An object of the invention is to provide improved apparatus or methods. According to a first aspect, the invention provides:
  • a method for routing traffic across a network, the network having an optical layer and an electrical layer by determining a routing path for the traffic across the network using a common topology representing the optical and electrical layers of the network.
  • the common topology is such that an individual port of a respective optical device in the optical layer is represented as a corresponding virtual node or nodes, coupled by one or more virtual links, in the common topology together with a representation of nodes and links of the electrical layer.
  • the determined routing path through the virtual nodes and links of the common topology is mapped back into a routing path through the actual optical devices of the optical layer.
  • Another aspect of the invention can involve a corresponding method of using such a network by requesting a routing and sending the new traffic according to a path determined by the above methods for routing.
  • Another aspect provides a program on a computer readable medium and having instructions executable by a processor to cause the processor to carry out the steps of the routing method.
  • Another aspect provides a network management system having a processor and the program for carrying out a method of routing.
  • Another aspect provides a node for a network having an optical layer and an electrical layer, the node having a program as set out above, as part of a distributed routing system.
  • Fig. 1 shows a schematic view of a network, showing an electrical layer and an optical layer.
  • Fig. 2 shows steps according to an embodiment
  • Fig. 3 shows a schematic view of nodes of an optical layer, with corresponding views of some nodes represented as virtual nodes and links,
  • Fig. 4 to 7 show views of different nodes represented as virtual nodes and links
  • Figs 8 and 9 show a part of a network and a corresponding common topology for that part of the network
  • Fig. 10 shows a view of a another network having multi layer node and having optical layers in different domains
  • Fig 11 shows steps according to another embodiment
  • Fig 12 shows steps according to another embodiment
  • Fig 13 shows a schematic view of a hybrid node in the form of a ROADM for use in a network.
  • Elements or parts of the described nodes or networks may comprise logic encoded in media for performing any kind of information processing.
  • Logic may comprise software encoded in a disk or other computer-readable medium and/or instructions encoded in an application specific integrated circuit (ASIC), field programmable gate array (FPGA), or other processor or hardware.
  • ASIC application specific integrated circuit
  • FPGA field programmable gate array
  • references to nodes can encompass any kind of node, including for example amplifying or filtering or switching nodes, not limited to the types described, not limited to any level of integration, or size or bandwidth or bit rate and so on.
  • References to optical nodes can encompass transparent nodes (such as amplifiers and all-optical wavelength crossconnects), nodes with OEO lightpath termination capabilities (like xOADMs) and translucent nodes (optical nodes with partial regeneration/wavelength conversion capabilities).
  • transparent nodes such as amplifiers and all-optical wavelength crossconnects
  • nodes with OEO lightpath termination capabilities like xOADMs
  • translucent nodes optical nodes with partial regeneration/wavelength conversion capabilities
  • references to software can encompass any type of programs in any language executable directly or indirectly by a processor.
  • references to hardware, processor or circuitry can encompass any kind of logic or analog circuitry, integrated to any degree, and not limited to general purpose processors, digital signal processors, ASICs, FPGAs, discrete components or logic and so on.
  • WSON Wavelength Switched Optical Network
  • Path computation in WSON can be very complex because it can involve: Routing to find the lightpath connecting a pair of source and destination nodes at low cost, Wavelength Assignment to ensure the e2e (end to end) wavelength continuity, and Impairment Validation, to assess the quality of the wavelength to guarantee its correct reception despite the optical impairments which affect the analogue signal propagation. All this is different to Packet Routing.
  • Node modeling in WSON can be useful to provide sufficient node information to support the complex path computation of WSON, such information including for example:
  • a wavelength originated from a local port can reach any/one direction (directionless/bound);
  • Color constraints ability to drop or add any/one wavelength at a port (colorless/bound);
  • Node capabilities interface types, switching capabilities, wavelength conversion, signal regeneration.
  • Some embodiments address these issues by building up a common topology in the form of a virtual network topology where packet and optical layers can be represented as homogeneous links and nodes with different attributes in order to allow routing to run concurrently across the two layers in a more efficient way.
  • the basic concept can be summarized as follows:
  • the considered node constraints can be static features which are dependent on the hardware of the optical node, or dynamic features selectable or controllable by a control plane.
  • One or more of the virtual nodes and links can have attributes to represent at least possible wavelengths, capacity and optical impairment, and the routing being determined at least according to the attributes, and according to other nodes and links in the common topology. It can be easier to compute if these constraints are attributes.
  • the network can have at least one multilayer node in both the electrical layer and the optical layer, and the multilayer node is represented in the common topology by a corresponding set of virtual nodes and links. Such multilayer nodes otherwise add particular complexity to the routing process.
  • the network can be partitioned into more than one domain, the common topology being determined for one of the domains. This enables the partition to be preserved and respected whatever the reason for the partitioning, such as administrative control by different operators, or preservation of confidentiality such as for an intranet or for islands of different vendor's proprietary equipment or different network management systems.
  • the network can have an optical device having a selectable operating wavelength, and the common topology can have a corresponding representation having virtual links and nodes corresponding to each of the different operating wavelengths. This can help enable wavelength assignment to be simplified.
  • the determining of the routing can have the step of creating a lightpaths matrix for light paths in the common layer. This can help enable the routing process to be calculated efficiently, especially in checking physical feasibility by accumulating optical impairments and other physical factors such as optical amplification along the path.
  • the method can have the step of assigning an optical source node and an optical destination node in the common topology to a respective traffic item of the traffic being routed. This can help simplify the overall routing task.
  • the routing step can involve determining relative cost for possible paths through the common topology for a particular item of the traffic being routed, and selecting a physically feasible path according to the cost.
  • the common topology can make this step simpler or more efficient than trying to compare routes in multiple layers for example.
  • the determining of the routing can involve any of: determining a path along the nodes and virtual nodes of the common topology, determining where items of the traffic being routed can be aggregated, and determining recovery paths for the items of the traffic being routed. Any or all of these steps can become simpler or more efficient by having a common topology, rather than having to carry out calculations with multiple layers.
  • the method can have the subsequent step of configuring the optical device according to the determined routing path. This can enable the routing to be used in the real network.
  • the method can have the preliminary step of generating the common topology.
  • the method can have the step of updating the common topology with attributes indicating network occupation, retrieved from the network.
  • the routing can then be determined for a new traffic demand without using parts indicated by the attributes as being occupied.
  • the first of these sets of steps can work on the network topology and perform a network transformation in order to provide a common topology for example in the form of a graph where both packet and optical nodes/links are represented homogeneously. This allows performing routing on the two layers concurrently. Such operations are performed just on network topology and node/links constraints independently of the traffic demand features. Such set of steps can be performed off-line in which case it has no real-time constraints.
  • the output is a common topology in the form of a virtualized network composed by links and nodes with attributes where the packet nodes are described according to the real network topology while optical nodes are described as suitable lightpaths list. Moreover in this set of steps the impairments validation is performed as well, for each of the lightpaths in the list.
  • the second set of steps can run on the common topology having virtual links and nodes. This can be a single topology where both packet and all optical nodes are represented as homogeneous links and nodes with different attributes. In this set of steps the multilayer path is computed including wavelength assignment on validated links.
  • Topology transformation by network virtualization of the all-optical nodes This operation can be performed just once and it is based on static information of the nodes/links.
  • the network 20 can be composed of an electrical layer 30, in the form of a packet layer or TDM layer or any other type of electrical layer, and an optical layer 40.
  • the electrical layer is composed of nodes 60 coupled by links, which are able to process and carry items of traffic such as packets. Each link is defined in terms of administrative cost and capacity (bandwidth).
  • the traffic demands also named commodities
  • the traffic demands can be aggregated to have bigger capacities so that several signals can be routed along the same link.
  • the optical layer has optical nodes 45 comprising optical devices 50, some of these optical devices may have switching functions, some may couple the optical nodes to the electrical layer, others may be tunable to use one or more selectable wavelengths for example.
  • the nodes may be configured by a network management system NMS 10, being centralized or distributed, and there can be an off line planning tool 5 in the form of a program run on a personal computer PC 15 for example.
  • the routing methods described can either be carried out by the off line planning tool, or by the NMS. If the NMS is distributed, it can be incorporated in one or more of the nodes, so that a processor in the node carries out the routing methods described, at least for traffic entering the network at that node.
  • the virtual network is obtained and this is the input of the second part, the routing solutions, described in more detail below.
  • the third part is the opposite of the first part, mapping the virtual network back to the original one, and the commodities are now routed and the wavelengths assigned along the actual optical paths, and the optical and electrical devices can be configured accordingly by a control plane, and the traffic flow can start.
  • a common topology is generated at step 100.
  • electrical nodes and links are added to the common topology, without needing amendment or transformation.
  • the common topology can be stored in store 160 as shown.
  • each port of a first optical device is represented as a virtual node coupled by virtual links in the common topology.
  • a next port of the optical device is similarly processed, to represent it in the common topology as a virtual node coupled by virtual links.
  • a next optical device is processed.
  • one or more items of traffic have routing paths determined using the common topology.
  • the routing paths determined in terms of the common topology are mapped back to the actual devices in the optical layer.
  • Fig. 3 shows a schematic view of nodes of an optical layer, with corresponding views of some nodes represented in an expanded form with ports represented as virtual nodes and links.
  • Network transformation principally impacts all-optical nodes in order to represent specific features of such nodes in homogeneous way with respect to the packet nodes.
  • the optical layer is composed of nodes 45 and links, which are able to process and carry optical signals. Each link is defined in terms of administrative cost and the number Y of wavelengths available on it, currently typical values for Y are 40 or 80. Each wavelength is characterized by a bandwidth (e.g. 1, 2.5 Gbit).
  • the optical nodes can be divided into two sets, depending on their connections in the network.
  • optical nodes 45 In the first set there are all the optical nodes 45 connected to only other optical nodes (OXC, Optical Cross Connects). The nodes of this kind are named from now on “simple nodes”. In the second set there are the “hybrid nodes” 70 (OADM, Optical Add-Drop Multiplexer); these are the nodes along the borders between the two layers, connected both to optical nodes and electric nodes 60.
  • OXC Optical Cross Connects
  • the hybrid nodes allow the passage of the commodities from an optical layer to the electrical layer, thanks to a set of transponders and muxponders.
  • the arriving signals can be eventually combined and transformed in a single optical signal but then, along all the optical domain, they cannot be combined or split any more. All the optical signals are considered unsplittable.
  • optical nodes simple and hybrid nodes
  • All the optical nodes have a number of optical ports (line ports), by which the commodities cross the node. These ports, if belonging to the same node, are fully connected and a node is composed of a number of ports equal to its optical degree (only connections between two optical nodes are considered).
  • Figure 3 shows as an example how one optical node has its port structure represented in the common topology by virtual nodes 145 and virtual links 155.
  • a simple optical node can be designed as a set of nodes, corresponding to the optical ports (the line ports). These ports are always fully connected, if belonging to the same node, and their number is equal to the node's optical degree (only the optical links are considered).
  • Each optical link represents a set of Y wavelengths (typically 80).
  • Each electric port accepts one or more electric signals (it depends if it is a transponder or a muxponder) and transforms them in a single wavelength ( ⁇ ⁇ ).
  • A/D sections In the hybrid nodes, in addition to the optical ports, there are specific A/D sections (Add/Drop section) to allow the adding and dropping of the signal between the two domains. These sections are composed by a number X of transponders and muxponders (named electric ports) by which the electric signal is transformed into an optical signal of a given wavelength.
  • an electrical port represents a coupling to a transponder, it accepts only one single electric signal which can be output as a wavelength; if an electric port represents a coupling to a muxponder it can accept and combines different electric signals and transforms them in one single wavelength.
  • Figure 3 shows as an example how one hybrid optical node has a number of transponders and a muxponder, represented in the common topology as multiple electrical ports 62 of the electrical node 60, coupled to virtual nodes 170 in a one to one manner for the transponders, and coupled to virtual node 174 representing the muxponder having two electrical paths and a single optical path.
  • Virtual links 155 represent paths having a fixed or selectable wavelength. These are then multiplexed by virtual node 175 onto a single path having many wavelengths which can be listed as occupied or free.
  • an electric node is connected to the optical domain it is linked to a hybrid node and, more specifically, to an electric port of that node by a bidirectional electric link.
  • Each A/D section is always associated to an optical port, in which it inserts the signal received in an add port or from which it removes the signal using a drop port. All the A/D ports are connected to this optical port by a bidirectional hybrid links set.
  • each optical port is associated to at most one A/D section and in this case it is connected to all the electric ports belonging to this A D section, by a bidirectional hybrid links set.
  • Each A/D section has a number X of electric ports 62 so X wavelengths are available on it.
  • the number X can be different for every A/D section, but it is always less than (or at most equal to) the total of wavelengths Y.
  • Each hybrid link, connecting an electric port to the correspondent optical port, represents a single wavelength.
  • Each couple of twin add/drop ports belonging to an A/D section, can be defined in terms of directionality and colour tunability: the couple of port can be defined as directionless/directionbound and colorless/colored as will be explained now in more detail.
  • the section can be defined as a directionless section (as a consequence, the relevant way has directionless capability). If all the ports of an A D section have not directionless capability, the section can be defined as a directionbound section (as a consequence, the relevant way is directionbound). In a realistic scenario, a node has just one directionless way while the other ways are directionbound.
  • the commodity added using this port can be tuned on each of the Y wavelengths.
  • the drop port can be tuned to receive each of the Y wavelengths (the same of the relevant add section).
  • the commodity added using this port shall use one predefined wavelength among the Y wavelengths.
  • the drop port is able to receive one predefined wavelength among the Y wavelengths (the same of the relevant add section).
  • an A/D section can have a mix of colorless and colored ports but configurations in which all the sections ports are colorless or all the section ports are colored are also possible.
  • the section must always have the same list of colours in the Add and in the Drop side of the section (biderectionality is required) and all the colours belonging to the same section (Add or Drop) must be different from each other.
  • each electric port can be directionless/directionbound and colorless/colored.
  • Each hybrid node can have both directionless and directionbound ways and each of these can have a mix of colorless and colored electric ports.
  • Figures 4 to 6 show some possible combinations.
  • figure 3 shows a directionless and colored example.
  • Figure 4 shows an example which is direction bound and colored.
  • the optical port, connected to a directionbound section is divided into two nodes 180 coupled by direction bound virtual links 165. This is useful to represent the directionbound feature, as better described with respect to Figure 7.
  • the example of figure 5 is direction bound and has both coloured and colourless paths.
  • the example of figure 6 is directionless and has a mix of coloured and colourless paths. If an electric port is colored a specific colour is pre-assigned to it, if it is colorless then any colour (different from the colours belonging to the same A/D section) can be associated to it and for this reason it is represented as a set of colored electric ports 172 and corresponding virtual links. However that representation is just to explain the colorless concept, but in the virtual model it can be represented as a single node and have a list of colours associated to it.
  • Figure 7 shows a hybrid node with two optical ports 270 and 180 respectively, and one A/D direction-bound section: when the electric signal arrives at an electric port of that section it has to go to the corresponding optical port 180 and then it is forced, by the direction-bound feature, to exit from the node to device 290 in neighbouring node 280, following the arrows shown in the figure. It cant reach the device 310 in the other neighbouring node 300.
  • a list of colours is associated to each node and link of the network to represent the different wavelength available on the same link. More specifically to each electric port and hybrid link is associated one colour or a list of colours (it depends on the colored/colorless feature) and a list of Y colours is associated to each optical node and optical link.
  • FIGs 8 and 9 show another example of a real network topology and its corresponding common topology respectively.
  • the real network has an optical layer having simple optical nodes 45, and hybrid nodes 70, coupled to electrical nodes 60.
  • each of the hybrid nodes is represented by virtual nodes 172 representing transponders, coupled by virtual links to a virtual node 175 to represent the multiplexing of optical wavelengths.
  • the optical devices of simple optical nodes are represented as in figure 3 by virtual nodes 145 and virtual links for each of the optical ports. This enables a homogeneous single layer topology which facilitates the routing process.
  • Figs 10, 11, further embodiments Fig 10 shows another view of a network according to an embodiment. This is similar to that of figure 1 , but also shows a control plane 12 distributed across some or all of the nodes and coupled to the NMS. It also shows a second optical layer 42, which may be part of a separate domain from the first optical layer 40, to enable separate management of domains for any reason, as discussed above.
  • the second optical layer may be arranged as a layer below the corresponding electrical layer, to implement some or all of the links between the nodes of the electrical layer, a so-called vertical layering.
  • An alternative is a horizontal layering where the optical layer can be seen as effectively at the same level as the electrical layer, rather than being used to implement links between the nodes of the electrical layer.
  • a multi layer node 70 effectively part of the electrical layer and part of the second optical layer. This may have electrical switching and optical add drop capabilities, and therefore be a particular type of the hybrid node discussed above.
  • Fig 1 1 shows steps according to another embodiment. In figure 1 1 , some similar steps are shown to those of figure 2.
  • network information is acquired, such as topology of the electrical and optical layers.
  • the common topology is generated as described above, by transformation of information about optical nodes and their ports, into virtual nodes and links that are homogenous with the nodes of the electrical layer. So far, these steps could be carried out off line by a planning tool, or by an NMS .
  • network occupation attributes are updated according to information retrieved from the network about the current occupancy.
  • a new traffic demand is received. A routing for this new traffic demand is determined using the free resources in the common topology, that is those resources not indicated as being occupied, as shown by step 135.
  • the routing in terms of virtual nodes and links is converted to a routing in terms of actual nodes and links. The new routing for the new traffic demand is sent out to the actual nodes using the NMS and control plane, at step 155.
  • the common topology can be created by transforming each optical node in a real topology of the optical layer, into a virtual graph representing direction, wavelength availability and interface type, together with electrical nodes and links.
  • a suitable routing algorithm can be run on the common topology to serve the traffic matrix.
  • the algorithm can include the wavelength assignment and the feasibility assessement (QoT) inside the optical layer (WSON area or domain). Routed paths are then mapped from the common topology to the real topology.
  • attributes can be assigned to each lightpath for example indicating a colour (or list of colours), a capacity and a cost.
  • Various traffic demand items referred to as commodities, can be sorted according to the parameters and the objective function, for example:
  • the path computations can then be made on the virtual topology for each item in the order specified.
  • the proposed algorithm can include the feasibility verification based on the estimation of a cumulative parameter called Quality of Transmission (QoT). Other ways can be conceived.
  • QoT Quality of Transmission
  • Other ways can be conceived.
  • the proposed algorithm is able to check the QoT while routing a path inside an optical domain.
  • the routing problem can be formulated as being to find the set of paths along which the commodities can be routed; and the colour or the list of colors to assign to each commodity along the optical path, where there is a choice, so that desired criteria are met to suit the application, such as the total cost is minimized and the colour or the list of colors assigned to each commodity is the same along all its optical path in the same optical domain, given certain inputs to the define the problem as follows, some of which are summarized in step 510 of fig 12:
  • the couple of nodes ( i " ⁇ * can represent the generic optical/electric node or a specific (colorless/colored) electric port of the optical node.
  • An oriented graph G(N,A) representing the virtual network, where N is the nodes set and A the links set.
  • N ⁇ ⁇ ) is the set of electric and optical nodes.
  • Each optical simple node is represented as a set of optical ports ⁇ > and each optical hybrid node as a set of optical and electric ports iP ⁇ ⁇
  • optical node is simple (OXC) if it is connected only to optical nodes;
  • an optical node is hybrid (OADM) if it is connected to optical and electric nodes; each ⁇ simple and hybrid) node v has ) optical ports, where ⁇ ⁇ ) is equal to the node's optical degree. The optical ports are fully connected if belonging to the same node.
  • each hybrid node v has k e l> ' J A/D section, where K eK )— K s ⁇ 3 ⁇ 4 );
  • each A/D section j is composed by electric ports ⁇ ° " ;
  • each A/D section is associated an optical port and all its electric ports are connected to this optical port (by bidirectional hybrid links);
  • each optical port is associated at most an A/D section and in that case it is connected to all the electric ports of this section (by bidirectional hybrid links); each electric port can be directionless ⁇ dl) or directionbound ⁇ db);
  • an A/D section can be defined dl if all its electric ports have dl capability
  • an A/D section can be defined db if all its electric ports have db capability
  • each hybrid node can have both dl and db A/D sections
  • each optical port 3 ⁇ 4 is assigned a list ⁇ ⁇ 3 ») of Y colours;
  • each A/D section j has ⁇ ' ⁇ ) electric ports, where ⁇ iO— ⁇ ⁇ i; each electric port can be colorless (cl) or colored (cd);
  • the commodity added using this port can be tuned on each of the Y wavelengths.
  • the drop port can be tuned to receive each of the Y wavelengths (the same applies to the relevant add section);
  • the commodity added using this port shall use one predefined wavelength among the Y wavelengths.
  • the drop port is able to receive one predefined wavelength among the Y wavelengths (the same of the relevant add section);
  • an A/D section j can have only cl ports or only cd ports or a mix of them
  • a db electric port can be cl or cd
  • a dl electric port can be cl or cd
  • each A/D section must always have the same list of colours in the Add and in the Drop side (bidirectionality is required) and all the colours belonging to the same section (Add or Drop) must be different from each other;
  • each electric port has a capacity ( U" P ⁇ ) equal to the capacity of the wavelength connected to it.
  • A ( rf - ⁇ ) is the set of electric, hybrid and optical links.
  • the cost vector can be defined as shown at step 520.
  • the cost vector can be defined as a set of parameters that will affect the routing progress.
  • a simpler version of the cost vector contains just an administrative cost. Additional costs can considered, for example: a cost which increases with bandwidth occupation (i.e. for Traffic Engineering purposes), an extra cost to discourage the routing across critical links, the delay introduced by the link, cost related to physical considerations which the operator would like to consider outside the QoT.
  • Each electric link connects an electric node to one other electric node or to one electric port; each hybrid link connects an electric port to the correspondent optical port; each optical link connects two optical ports; to each hybrid link is associated one colour/a list L of colours (it depends on the cd/cl electric port); to each optical link 3 ⁇ 4 is associated a list L( a *) of Y colours (typically 80).
  • a cost vector is defined at step 520, to take into account what is to be optimized to suit the application.
  • Three main steps in the determination of routing paths can be considered: lightpath inizialization at step 530, Source and Destination Assignment at step 540, and Routing and Updating at steps 550 to 570.
  • lightpath inizialization at step 530 Source and Destination Assignment at step 540
  • Routing and Updating at steps 550 to 570 Routing and Updating at steps 550 to 570.
  • c has a value which is a function of the costs assigned to the links composing the lightpath and other parameters, as defined at step 520;
  • Step 540 of fig 12, Source and Destination Assignment:
  • step 550 For each commodity j, as shown in step 550:
  • step 570 update the capacities along the electric links belonging to ;
  • Fig 13 view of a hybrid node in the form of a ROADM
  • FIG. 13 shows an example of a ROADM which could be used as a hybrid node, or could be part of a multi layer node, if combined with some electrical switching of the added or dropped electrical signals. It shows four similar modules labelled north, south, east and west, each of which have similar components, so only south, 680, will be described further.
  • This drop path leads to an array wave guide 660 which has an optical wavelength demux or separation function, for separating different wavelengths onto separate physical paths to receivers Rx 670.
  • These receivers output electrical signals which can be fed to further electrical circuits for TDM demux or electrical switching for example, or straight to local destinations such as local networks.
  • the module also has a wavelength selective switch WSS 640, for selecting a wavelength to be sent out on the outgoing path from the south module.
  • This WSS receives wavelengths from other modules East, North, and West along internal waveguides labelled generally as 600, and one or more wavelengths for adding at that module.
  • the added wavelength is selected by AWG 620 which combines different physical paths from separate transmitters 610 for each wavelength, onto a single input of the WSS. Any one of the transmitters can be activated, which determines which wavelength is being added.
  • An electrical signal to be added can be fed to the appropriate transmitter for the desired wavelength.
  • the WSS could be made as a WDM multiplexer, or a WDM multiplexer could be provided downstream of the WSS. In this case, the AWG could feed the WDM multiplexer directly, bypassing the WSS.
  • embodiments can enable: more efficient multi-layer routing, resource optimization that allows capex reduction, a scalable solution, and a method of optical nodes modeling that allows applying several dynamic routing approaches in a multilayer scenario.
  • resource optimization that allows capex reduction
  • a scalable solution that allows applying several dynamic routing approaches in a multilayer scenario.
  • a method of optical nodes modeling that allows applying several dynamic routing approaches in a multilayer scenario.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Data Exchanges In Wide-Area Networks (AREA)
  • Optical Communication System (AREA)

Abstract

L'invention concerne le routage de trafic dans un réseau comprenant une couche optique (40) et une couche électrique (30), qui consiste à utiliser une topologie commune représentant les couches optique et électrique du réseau. La topologie commune est telle qu'un port individuel d'un dispositif otique respectif dans la couche optique (40) est représenté par des nœuds virtuels correspondants (145), couplés par des liaisons virtuelles (155), dans la topologie commune conjointement avec une représentation de nœuds et de liaisons de la couche électrique. Le chemin de routage en termes de la topologie commune est fait correspondre en retour à un chemin de routage passant par les dispositifs optiques réels (50) de la couche optique. Par déplacement de la gestion de contraintes de couleur (comprenant une attribution de longueur d'onde, une continuité de longueur d'onde et une sélection de couleur lorsqu'elle est réglable/sélectionnable) et de direction vers l'étape préliminaire de création de la topologie commune, le processus de routage peut être simplifié.
EP10702145A 2010-01-12 2010-02-03 Routage dans un réseau à couches optique et électrique Withdrawn EP2524457A1 (fr)

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WO2013091688A1 (fr) * 2011-12-21 2013-06-27 Telefonaktiebolaget L M Ericsson (Publ) Représentation topologique d'un réseau multicouche
EP2928090B1 (fr) * 2012-12-17 2018-03-14 Huawei Technologies Co., Ltd. Élément de réseau optique, élément de réseau électrique et procédé d'établissement de signalisation lorsqu'un relais électrique est dans un élément de réseau électrique
GB2536859A (en) * 2014-11-28 2016-10-05 Aria Networks Ltd Modeling a multilayer network
GB2537338A (en) 2014-11-28 2016-10-19 Aria Networks Ltd Modeling a border gateway protocol network
GB2543017A (en) 2014-11-28 2017-04-12 Aria Networks Ltd Telecommunications network planning
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