Integrated IP/WDM Routing in GMPLS-Based Optical Networks Jaume Comellas, Ricardo Martínez, Josep Prat, Vicente Sales, and Gabriel Junyent Politècnica de Catalunya (UPC) Abstract Future transport networks will have to cope with the continuous growth of IP traffic. Furthermore, transport networks need to evolve so as to drastically reduce both deployment costs and operating expenses. A reasonable strategy to achieve this goal consists of simplifying the network architecture by reducing the number of layers. Assuming a peer model IP over optical network, we propose an integrated routing strategy that takes into account constraints and dynamic occupancy of both the IP and optical layers. The collaboration of both layers in the routing process leads to optimization of network performance. The main emphasis is on the implementation requirements of this grooming functionality using GMPLS-TE mechanisms. Simulation results show the benefits obtained by applying this strategy.
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t is widely recognized that future transport networks will have to evolve to support the well-known growth of data traffic and new emerging network requirements such as fast and flexible provisioning, multiple levels of quality of service (QoS), optical rerouting, and fast restoration. Furthermore, the architectural complexity of the networks has to be reduced in order to save costs and ease their management. In this context, IP over optical layer networks are expected to be the right solution. Specifically, optical layer refers to a transport layer based on point-to-point dense wavelength-division multiplexing (DWDM) technology. While DWDM has been traditionally used just to increase the transport capacity, in IP over optical scenarios, some networking functionalities are implemented directly within the optical layer, which incorporates a control plane responsible for network routing and signaling functions. From an architectural viewpoint, an IP over optical layer scenario might be described in terms of three models: overlay, augmented, and peer. In an overlay network, every layer runs its own control protocol,s and no trust exists between them, so the operations in one layer can be independent from those in the other layer. The solutions developed for either the IP or optical layer for traffic engineering (TE) issues can be directly applied to each network. The overlay model can be understood as a client-server relationship, where the IP network (client) requests transport services to the optical network (server). Therefore, when considering this scenario, the principal advantage is that the TE mechanisms can be fitted to best meet the needs of each particular layer for selected objectives. The augmented model is an evolution of the overlay where the layers share some information but separated protocols are used. Although every layer has its own control plane, some routing information is shared in order to optimize network performance. For example, external IP addresses can be carried within the optical routing protocols to allow IP clients to have reachability information. Finally, in the peer scenario there is an integrated control plane that governs all the network layers. Only one set of pro-
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tocols is running, so each layer has complete knowledge about the other. Therefore, IP traffic management and optical resources control are considered together. Every node maintains an IP/WDM network state information database that allows appropriate allocation decisions to be made dynamically. While in the overlay or augmented models global resource usage optimization is not guaranteed (every layer is optimized in isolation), in the peer model both layers collaborate in order to achieve some common performance objectives. As will be shown in the next sections, a globally optimum solution does not necessarily mean that the individual layers are also optimized. When each network node has complete knowledge about the network status (traffic flows, links used, available optical resources, and available capacity in the already established routes), the entire network can self-adapt dynamically to the traffic changes. Although the overlay model is seen as the first step in IP over optical networks, it is widely agreed that in the far future the peer model will gain momentum. Under this assumption, this work deals with the possibility of doing cooperative IP/WDM routing [1–3]. Traffic engineering performance objectives include two aspects: traffic-oriented and resourceoriented. The key traffic-oriented performance objectives include minimization of the number of packets lost, maximization of network throughput, and QoS-related issues. On the other hand, resource-oriented objectives deal with the efficient use of network resources. If only traffic objectives are considered, some parts of the network may be saturated while other network elements remain underutilized. In this work both aspects are considered together in order to obtain better performance of the whole system. A single control plane, based on IP-like signaling and routing mechanisms that are being developed in the framework of generalized multiprotocol label switching (GMPLS) [4], governs both layers. When traffic is routed taking into account only the optical layer, some wavelengths can be wasted carrying very low amounts of information. On the other hand, if pure IP routing is applied, router capacity becomes the bottle-
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neck because the information has to be processed at every node. An integrated Node 4 routing model that dynamically combines different traffic flows to efficientIntegrated IP Integrated IP ly use the network resources is router-OXC router-OXC analyzed. It is referred to as IP/WDM grooming, and combines routing and Node 3 Integrated IP trunking, taking into account the router-OXC requirements from both layers for improving network performance. The realization of the proposed IP/WDM grooming is possible thanks to routing Node 5 Integrated IP and signaling mechanisms that are router-OXC being developed in the framework of TE for GMPLS networks. To improve the scalability of GMPLS-based netActive LSP works it may be useful to aggregate Option 2 multiple TE label switched paths Integrated IP Option 1 router-OXC (LSPs) [4] inside a bigger TE LSP. Intermediate nodes see the external LSP only, they do not have to maintain ■ Figure 1. IP/WDM grooming example. forwarding states for each internal LSP, so less signaling messages need to be exchanged. The above mentioned aggregation of LSPs is accomplished intermediate node has to electronically process the different when a node that creates a TE-LSP advertises it as a forward flows. The introduction of MPLS mechanisms makes this proadjacency (FA) LSP into an enhanced version of a link state cess easier as the intermediate nodes only have to read the protocol such as Open Shortest Path First (OSPF). The other label to forward the data to the next node. When this is nodes can then use this FA-LSP during their path computaapplied to the optical layer (GMPLS), a lightpath is estabtion by nesting lower-order LSPs into the FA-LSP. OSPF lished from the source to the destination node, and flows are floods the information of FAs just as it floods information tunneled through it [5]. Problems may arise in this case when about any other LSPs. The peer model, where a single control a lightpath has to be created even if it has to transport small plane governs both the IP and optical layers, allows no distraffic flows. This will lead to inefficient use of the optical tinctions to be made between the different LSP types. In fact, resources. A new scenario where all the constraints (traffic only FA-LSPs, which are supposed here to be lambda switch pattern, network topology, resource status, and performance capable (LSC) [4], are to be taken into account when routing objectives) are considered seems to be the right choice. a new traffic flow. The use of an already established FA-LSP Let us suppose that node 1 has to create a new packet LSP can be very useful even if its route is not exactly the same as to node 5. If a typical Shortest Path First algorithm is used (at the new LSP route. Its usefulness is given by the fact that the optical layer), a new l-LSP through node 3 seems to be using the already active FA-LSP, resources can be efficiently the more efficient choice (discontinuous trace on the figure). occupied, so network capacity is increased. When performing However, there may be some situations (e.g., node 3 resources path computation, a node not only uses conventional links are highly busy), where it is better to create a new l-LSP from (free optical channels, referred as NLinks later), but also con1 to 2 (dotted line) and then group this flow with the already siders the existing FAs. Once a path is computed, the node active l-LSP from node 2 to node 5 (continuous trace), which uses the appropriate signaling mechanisms to set up the conis supposed to have enough available bandwidth. As all the nection. New RSVP extensions for TE are being proposed, network nodes maintain a complete network state information allowing to establish the label binding necessary when FAdatabase, they are able to realize which is the best route, LSPs are considered. assuming that the databases are properly updated and the The remainder of the article is structured as follows. The routing algorithm manages their information adequately. proposed feature is shown by an example. We deal with the formal implementation of the grooming functionality. We have divided it in two subsections, one devoted to the routing Grooming Implementation Using GMPLS and particularities and the other focused on the signaling aspects. Traffic Engineering Protocol Extensions Simulation results that show the usefulness of the proposed strategy are summarized. Finally, the main conclusions of this The traditional IP routing protocols (IS-IS, OSPF) are being work are highlighted. extended to satisfy GMPLS requirements [4]. In order to achieve the performance described above, it is necessary that every network node has a complete view of the whole netIP/WDM Grooming Example Connection work, not only of its topology but also of the bandwidth availability on every active l-LSP. The integrated routing proposed can be understood by means of Fig. 1. It shows a network where every node is composed of The internal structure of the network nodes [3] is reprean IP router and an optical cross-connect (OXC) in a peer sented in Fig. 2. From the transport viewpoint there are two configuration. IP flows, also referred to as packet LSPs [4], main components: the OXC and the IP router. The OXC is use optical channels (l-LSPs) to reach their destination. In configured to establish the required l-LSPs. These can be classical IP routing packet LSPs would be forwarded to the locally originated (to accommodate new IP flows) or next node on a hop-by-hop basis until they reach their destipassthrough connections. In the former case, assuming that nation. It is clear that this is not a good solution as every they have enough available bandwidth, they would be used
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■ Figure 2. Network node structure. later to groom new packet LSPs if required. The main function of the IP router is the generation of new packet LSPs. Every new packet LSP is allocated in a l-LSP which can be new or already active. As stated above, l-LSPs are advertised to the network as FA-LSPs. When the node is the origin of a l-LSP and a packet LSP (arriving from a neighbor node) has to be groomed in it, the traffic flow transits from the OXC to the router, where it is allocated in the desired l-LSP. The GMPLS router manager is the control plane part of the network node. It is made up of six main blocks (Fig. 2). Link state database: It contains information about the established LSPs. Its complete structure is studied below. OSPF-TE: This generates and receives the link state advertisements (LSAs), which contain information about the status of the network LSPs. When a new connection is established an LSA is flooded to advertise to the rest of the network nodes. These can then update their link state databases. RSVP-TE: It generates the appropriate Path/Resv messages for the setup, modification, and teardown of LSPs. It is analyzed in detail in the next section where some modifications are proposed in order to achieve the right signaling for the grooming functionality. Routing Controller: This element is responsible for finding the best route when a new request is received. According to the link state information it will decide, as the result of the routing algorithm, the path for the new connection. This is a very important issue as the entire network’s performance highly depends on the correct operation of the routing algorithm. When computing a new route, the algorithm assigns a lower cost to the FA-LSPs. This will favor reuse of already working FA-LSPs. On the other hand, if the cost assigned to the FA-LSPs is excessively low, it may suppose that the chosen routes will be longer than necessary, so used resources will increase. Link resource manager (LRM): It has information about the resources available in the node. When resources are requested it decides whether it is possible to use them and informs the other elements about the node status. Connection controller: It takes appropriate actions to establish the physical connections once the routing controller has decided the route. The LRM checks whether the request-
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ed resources are available and, when possible, assigns them to the connection. The key point of this work consists of the leveraging of the FA concept to the optical layer. By definition, an FA [6] is a TE link between two GMPLS nodes whose path transits one or more other GMPLS nodes in the same instance of the GMPLS control plane. Therefore, they allow the grooming functionality explained here. In our case, l-LSPs are supposed to be FALSPs so that packet LSPs can be nested into them even if their origin is different than the l-LSP origin. At this point, it is important to note that only the source and destination nodes can access the lower-order LSPs (packet LSPs) carried on the FA-LSP (the intermediate nodes only cross-connect the optical channel).
Routing Aspects The local routing algorithm, using the concept of constraint-based routing, has three inputs. Network topology. The physical structure of the network has to be known in order to find appropriate routes for the new LSPs. This structure consists basically of fibers, number of wavelengths per fiber, and mapping of the IP traffic flows onto these optical channels. Link state database. A traffic matrix that represents an updated view of the active FA-LSPs and conventional (to the adjacent nodes) links. It has been defined in [7] and contains the following attributes (which are advertised by means of the new OSPF/GMPLS extensions) of each LSP: • Link ID: This is the LSP network identifier. For the case of point-to-point link type, this is the Router Id of the neighbor (the remote end of the TE link). • Link type: The link type sub-type length value (TLV, see [7]) defines the type of the link. It is set with the value point-to-point [7] for FA-LSPs. • Link multiplexing capability: Indicates the LSP switch capability. In our case, only l and packet are allowed, and lLSPs are considered FA. • Ingress and egress interface IP addresses. • Maximum bandwidth: This sub-TLV specifies the maximum bandwidth that can be used on this link in this direction. • Maximum reservable bandwidth: This sub-TLV specifies the maximum bandwidth that may be reserved on this link in this direction. Note that it may be greater than the maximum bandwidth (in which case the link may be oversubscribed). • Unreserved bandwidth: It informs the routing system about the possibility of being used by a new LSP. • Explicit route object (ERO). It contains the sequence of the nodes traversed by the LSP. • Ingress LSP label: The label given to the FA-LSP by its origin node. We propose to use this sub-TLV as the label identifying the FA-LSP. In this way, when a new LSP has to be groomed into an FA-LSP, the node that generates the new LSP will advertise it by adding this label to the Path message. The ingress LSP label is only used for signaling aspects when setting up a new requested connection, so the grooming functionality is performed. Although it is not strictly necessary to use this label as FA-LSPs can be advertised as unnumbered interfaces [8], it would be very useful
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to perform source explicit routing (the source node decides Label_SET: Y PATH:: GenerLabelReq whether or not to use an FAERO: node 2, LSP). Modified traffic label subobject: X Performance objective(s). Mainly parameters related to QoS parameters (throughput, traffic losses, delay, jitter, etc.) and cost restrictions. RESV:: RESV:: The main objective is usually to Label: Z maximize network throughput while Modified traffic parameters minimizing the amount of resources used. As our proposal has taken into Link Link Link Ingress/egress Maximum Maximum Unres. Explicit Ingress consideration the possibility of Id type multiplex interface IP bandwidth reserved band- route LSP grooming a new flow with an capacity address bandwidthwidth label already existing FA-LSP, the algoIP address Router Point λ-LSP 2-4-5 X rithm has to find the best route taknode 2/node 5 ID of to ing into account the issues node 5 point described above (network topology, link state database, and performance objectives). It is based on ■ Figure 3. FA-LSP grooming time diagram and link state database example. Dijkstra’s shortest path algorithm, but the cost function contemplates the possibility of reusing an already established FA-LSP to reach the destination. The route cost the new LSP setup is divided into the following steps: depends on the number of hops between origin and destina•Node 1 generates the Path message with the computed tion but, in order to improve the performance, lower cost is strict explicit route and the label of the l-LSP where the new applied to the active FA-LSPs. Therefore, dynamic grooming LSP has to be groomed (in the example, subobject node 2 IP is achieved automatically assuming that the link state database address and label subobject with the label given by node 2 to is properly updated. The proposed model has a drawback as that l-LSP). all the nodes must have real-time updated knowledge of the •When node 2 receives the Path message, it reads the subnetwork traffic status. This supposes a great amount of conobject IP address and the label subobject (which informs it trol information flooding in the network, and scalability probthat the new LSP has to be groomed or tunneled with the lems may arise. A possible strategy for alleviating this problem already existing l-LSP), and configures itself with this label could consist in some sort of flooding control [6]. This can be information. This configuration consists of finding the label achieved by means of defining a minimum threshold to flood associated with the egress node into the FA-LSP to be used. new changes. The threshold can be absolute or relative. In the It is important to remark that all the nodes within an LSP former case it consists of establishing a fixed threshold; know the used labels between nodes along the path. changes are only notified if the LSP unreserved bandwidth •Finally, node 2 sends the Path message directly to node 5 variation exceeds some predetermined percentage of the total with a Label_Set object value corresponding to that given by LSP bandwidth. For the relative case, the threshold is variable node 5 to the FA-LSP (the used l-LSP is already active, so and diminishes as the unreserved bandwidth does. Anyway, node 4 does not need to modify anything). Node 5 will perscalability problems in GMPLS-based networks are considform the same operations done in node 2 and then will generered one of the main potential problems as limiting the inforate the Resv message to establish the LSP. Once the mation flooding supposes that link state databases are not connection is established, the new link status will be flooded actually updated, so instabilities may appear (new connections (Fig. 3). would require resources that are not available). On the other hand, having complete knowledge of all the network resources Simulation at every node allows more efficient path computation in distributed routing networks [9]. In order to quantify the benefits obtained by applying our The routing algorithm output is the explicit route, which grooming proposal, some simulations have been carried out. will be set up using the appropriate signaling protocol. The Results show, by means of blocking probability and traffic new RSVP extensions for GMPLS support the grooming funcload supported by the routers, how the integrated routing tionality by using FA-LSP tunnels. Although this functionality strategy improves network performance compared with tradiis currently developed for nesting packet LSPs, it can be levertional IP hop-by-hop routing or static optical routing. aged, under a peer network, to the nesting of packet LSPs in Some initial assumptions have been adopted: •The network has 10 nodes in a bidirectional ring topology. l-LSPs. Every node has four optical WDM transmitters/receivers Signaling Aspects (input/output interfaces). The node is responsible for the allocation of IP flows into these optical channels (OChs). Each In order to perform the signaling of FA-LSPs, a new subobOCh is able to accommodate a capacity of 2.5 Gb/s. ject is introduced (label subobject). It allows the grouping of a •Optical and electrical resources are simultaneously considnew traffic flow on a pre-established FA-LSP [10]. It is includered when placing traffic. This strategy fits well in a peer ed in the ERO following the node IP address. Once the node model. All the established OChs are considered FA-LSPs, has received the PATH message , it checks the label subobject which means that different IP flows can be grouped into them to know the FA-LSP that has to be used. Using the example according to their path computation. shown in Fig. 1, and assuming that the routing/grooming algo•The OXCs are wavelength selective. This means that a rithm has found path 1-2-4-5, reusing the active 2-4-5 l-LSP,
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nodes. In order to have balanced connectivity nodes have direct optical links to their closest neighbors and to the nodes that are two hops farther. For example, assuming that nodes in the ring are numbered in ascending order, node 6 will have OChs to nodes 3, 5, 7, and 9. IP flows are accordingly distributed with their destination to the appropriate OCh, avoiding processing them at every intermediate node. When an IP flow is destined to a node that is not directly reachable with the OCh, an intermediate electrical hop is performed. The routing strategy employed in this case simply looks for a possible route to the destination using the predetermined OChs. In the IP/WDM grooming model, optical routing allows the IP flows to be accommodated by either new or already established OChs. The OChs are not statically placed, but set up and torn down dynamically according to the instantaneous traffic. To compute the path for each new request, the routing algorithm uses a cost function taking into account the routing aspects mentioned earlier. This cost function is represented by the expression
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where N links is the number of new optical links (between adjacent nodes) that have to be ■ Figure 4. a) Mean router load and b) blocking probability vs. number of simulset up to allocate the desired connection, taneous IP flows (P = 0.7 and Q = 1.2 for the IP/WDM grooming case). N_FA-LSP_Links corresponds to the optical links already active (belonging to any FA-LSP), and N hops is the number of O/E/O conversions the information has to suffer. P and Q are cost coeffiwavelength rests unchanged from the source to the destination node of an FA-LSP. Although every node has four cients that are adjusted to achieve the best network input/output interfaces, the OXCs have cross-connection performance. Setting P < 1 implies fostering reuse of already capability for up to 10 defined wavelengths. This allows nodes established FAs. On the other hand, fixing P with an excesto be transparent for some OChs (they are simply cross-consively low value supposes that routes would be longer than nected at the node), while other OChs have their origin/destinecessary (the number of used resources would increase). The nation at the node. As every node is able to send up to four Q value has been set during the simulations to 1.2, to avoid OChs, some links can support more than four OChs. The overloading of the routers and minimize the number of maximum link capacity was fixed to 10 OChs during simulainput/output interfaces used (paths with many optical-elections. tronic-optical, O/E/O, conversions will be avoided as their cost •The simulations use a dynamic traffic model, where the is higher). connection requests, considered to be IP flows with bit rate Figure 4 shows the obtained results. The mean router load granularity of 50 Mb/s, arrive uniformly distributed from any is normalized to the OCh capacity (maximum traffic load prosource to any destination. The interarrival time (IAT) is Poiscessed by the routers is four OChs). Simulations have been son-based, while the connection holding time (HT) has been performed generating new IP flows until the network reaches modeled with exponential statistics. The mean IAT has been a steady state (the number of simultaneous IP flows carried by set to 1 (arbitrary time unit); by changing the mean HT, difthe network is constant). Mean HT is adjusted to achieve ferent network loads are generated. Thus, when HT increases these conditions. Plotted values represent the mean router the number of simultaneous IP flows within the network also load and the percentage of blocked connections in this steadyincreases. IP flows that cannot be allocated are discarded. state regime. Every simulation has been repeated 10 times Three different models have been simulated and compared: and results averaged to achieve smoother trends. IP hop-by-hop routing, static optical routing, and dynamic Of course, the IP hop-by-hop model exhibits the worst perintegrated IP/optical routing (IP/WDM grooming). In the forformance, due to the routers saturation as they have to promer, the path from the source to the destination is performed cess all the IP information at every node. With the static by hop-by-hop routing, so all routing is done at the electrical optical routing model both the router load and blocking probIP level (OXCs are not needed). IP flows are grouped in optiability decrease (longer direct optical paths are allowed). cal links and forwarded to the next node, which processes all Finally, when using the integrated routing algorithm (IP/WDM the information again and resends the traffic until it reaches grooming) results are improved, especially in terms of necesits destination. sary router load. This is a relevant advantage since the proIn the static optical routing model, wavelengths are routed cessing capability of IP routers has a key impact on network among nodes in a fixed but optimum way for uniformly discost. The P coefficient has been fixed to a 0.7 value so that tributed traffic. Every node is optically linked with four other paths using existing OChs (FA-LSPs) have lower cost than
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new OChs. Although average results are improved, it is noteworthy that the deviation between the different simulations is higher in this case (a wrong routing decision at the beginning will influence the following decisions).
Conclusions It is recognized that future transport networks will have to evolve to cope with the growth of data traffic, fulfilling new emerging requirements and drastically reducing both costs and operating expenses. In this context, IP over optical layer is a sound scenario gaining momentum. In this article, focusing on IP over optical layer with a peer model, we have exposed an advanced grooming functionality implementable with the proposed extensions of current routing tables by means of the new OSPF-TE objects and utilization of the new RSVP-TE label subobject. Grooming decisions are made at the ingress node assuming that it has an accurate knowledge of the network status. In some cases, the delay introduced by the routing and signaling processes may impede reaching optimal network performance. Further research is needed regarding network scalability issues, which can be a potential problem in this routing scenario. Simulations show how the proposed scheme improves network performance over fixed routing strategies. Approximately 15 percent router load reduction is achieved from static optical routing. On the other hand, the number of blocked connections is 7 percent smaller for high network loads. The simulations have been performed for a very specific topology (a bidirectional ring). In more complex topologies (mesh networks), where the number of different routing paths to reach a destination increase, we reasonably believe that dynamic grooming can even better demonstrate its benefits.
Catalunya (UPC), Barcelona, Spain. Since 1991 he has been a staff member of the Optical Communications Research Group at UPC. His current research interests mainly concern optical transmission and networking topics. He has participated in different research projects funded by the Spanish Government and European Commission. He is an assistant professor in the Signal Theory and Communications Department of UPC. RICARDO MARTINEZ (Barcelona, 1977) is a graduate in telecommunications engineering from UPC (2002). He is currently pursuing his Ph.D. degree in the Signal Theory and Communications Department of UPC. He worked as an undergraduate researcher at Telecom Italia Lab (TILAB), Turin, Italy, from March to November 2001, participating in the IST LION project as part of his M.Sc. thesis. Since November 2002 he has been a research assistant in CTTC’s Optical Networking Group. JOSEP PRAT graduated in telecommunications engineering in 1987, and received a Ph.D. degree from UPC) in 1995. He has mainly investigated broadband optical communications with emphasis on WDM systems and advanced optical modulations, and has participated in several RACE, ACTS, and IST European projects on optical transport network supervision, IP over WDM, and access networks. In 1998 and 1999 he was a guest scientist in the Optical Networks Group, University College London. He is a professor in the Signal Theory and Communications Department of UPC, and currently head of the Laboratories of the School of Telecommunications Engineering of Barcelona (ETSETB). VICENTE SALES received an M.S. degree in telecommunications engineering from UPC in 1992. Since 1995, he has been a staff member of the Optical Communications Research Group at UPC, where he has mainly investigated traffic engineering and supervision in IP-over-WDM networks. He is a professor in the Signal Theory and Communications Department of UPC. GABRIEL JUNYENT received an M.S. degree (1973) in telecommunications engineering from the Universidad Politécnica de Madrid, and a Ph.D. degree (1979) from UPC. Since 1989 he has been a full professor in the Signal Theory and Communications Department of UPC. He leads the Optical Communications Research Group and Advanced Broadband Communications Center (CCABA) of UPC. His current research interests include optical network architectures and optical system design and optimization.
Acknowledgments The authors wish to thank all participants of the IST Project LION and the European Commission for partly funding this work.
References [1] B. Rajagopalan et al., “IP over Optical Networks: Architectural Aspects,” IEEE Commun. Mag., vol. 38 no. 9, Sept. 2000, pp. 94–102. [2] K. Sato et al., “GMPLS-based Photonic Multilayer Router (Hikari Router) Architecture: An Overview of Traffic Engineering and Signaling Technology,” IEEE Commun. Mag., vol. 40, no. 3, Mar. 2002, pp. 96–101. [3] C. Xin et al., “On an IP-centric Optical Control Plane,” IEEE Commun. Mag., vol. 39, no. 9, Sept. 2001, pp. 88–93. [4] L. Berger, Ed., “Generalized MPLS — Signaling Functional Description,” Internet draft, draft-ietf-mpls-generalized-signaling-09.txt, 2002, work in progress. [5] A. Banerjee et al., “Generalized Multiprotocol Label Switching: An Overview of Signaling Enhancements and Recovery Techniques,” IEEE Commun. Mag., vol. 39, no. 7, July 2001, pp. 144–51. [6] E. Mannie et al., “Generalized Multi-Protocol Label Switching (GMPLS) Architecture,” Internet draft, draft-ietf-ccamp-gmpls-architecture-03.txt, 2002, work in progress. [7] D. Katz, D. Yeung, and K. Kompella, “Traffic Engineering Extensions to OSPF Version 2,” Internet draft, draft-katz-yeung-ospf-traffic-09.txt, 2002, work in progress. [8] K. Kompella and Y. Rekhter, “Routing Extensions in Support of Generalized MPLS,” Internet draft, draft-ietf-ccamp-gmpls-routing-05.txt, 2002, work in progress. [9] S. Sengupta and R. Ramamurthy, “From Network Design to Dynamic Provisioning and Restoration in Optical Cross-Connect Mesh Networks: An Architectural and Algorithmic Overview,” IEEE Network, vol. 15, no. 4, Jul/Aug 2001, pp. 46–54. [10] P. Ashwood-Smith et al., “Generalized MPLS Signaling — RSVP-TE Extensions,” Internet draft, draft-ietf-mpls-generalized-rsvp-te-09.txt, 2002, work in progress.
Biographies JAUME COMELLAS (
[email protected]) received M.S. (1993) and Ph.D. (1999) degrees in telecommunications engineering from the Universitat Politècnica de
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