10-08-2013, 04:40 PM
GMPLS :Generalized Multiprotocol Label Switching
[attachment=57077]
ABSTRACT
In IP routing each packet travels from one router to the next, each router makes an independent forwarding decision for that packet. That is each router analyses packet header, and each router runs a network layer routing algorithm. Each router independently chooses a next hop for the packet, based on its analysis and the results of running the routing algorithm.
In conventional IP forwarding a particular router will typically consider two packets to be in the same FEC(forward equivalence class) if there is some address prefix X in that router's routing table such that X is the largest match for each packets destination address. As the packet traverses the network each hop in turn reexamines the packet and assigns it to the FEC.
Almost all protocols deployed today are based on algorithms designed to obtain the shortest path in the network for packet traversal and do not make into account of additional metrics (such as delay and congestion), which can further decreases the network performance. To speed up the forwarding scheme, a GMPLS device uses labels rather than address matching to determine the next hop for the received packet.
GMPLS is an extended framework of MPLS protocol. Generalized MPLS provides not also the packet switching but also switching in time slot domain(TDM), wavelength domain(DWDM),and space domain(fiber). In
MPLS the assignment of a particular packet to a particular FEC is done just once, as the packet enters the network. The FEC to which the packet is assigned and is encoded as a short fixed length value known as a label. When a packet is forwarded to its next hop, the label is sent along with it that is the packets are labeled before they are forwarded. GMPLS is a significant and challenging concept for next generation data and optical networks. By eliminating the two layers, ATM and SONET/SDH, GMPLS provides interoperable, scalable and parallel development of IP over DWDM network architecture.
INTRODUCTION TO GMPLS
The emergence of optical transport systems has dramatically increased the raw capacity of optical networks and has enabled new sophisticated applications. For example, network-based storage, bandwidth leasing, data mirroring, add/drop multiplexing [ADM], dense wavelength division multiplexing [DWDM], optical cross-connect [OXC], photonic cross-connect [PXC], and multiservice switching platforms are some of the devices that may make up an optical network and are expected to be the main carriers for the growth in data traffic.
Multiple Types of Switching and Forwarding Hierarchies
Generalized MPLS (GMPLS) differs from traditional MPLS in that it supports multiple types of switching, i.e. the addition of support for TDM, lambda, and fiber (port) switching. The support for the additional types of switching has driven GMPLS to extend certain base functions of traditional MPLS and, in some cases, to add functionality. These changes and additions impact basic LSP properties, how labels are requested and communicated, the unidirectional nature of LSPs, how errors are propagated.
MPLS BACKGROUND AND OPERATION
MPLS network consists of two types of devices. One is label switch router and another is label edge router. Label switch router is a high speed router in the core of the network. Label edge router separates the MPLS network and access network. Access network may be frame relay, ATM networks. A label is a short fixed length word which has local significance only. LER checks the IP header and inserts the label stack before the header in the IP packet. Label stack is a stack of labels each LSR only looks the topmost label in the stack, and switch the packet to the appropriate router. MPLS extended the suite of IP protocols to expedite the forwarding scheme used by IP routers. Routers have used complex and time-consuming route lookups and address matching schemes to determine the next hop for a received packet, primarily by examining the destination address in the header of the packet. MPLS has greatly simplified this operation by basing the forwarding decision on a simple label. Another major feature of MPLS is its ability to place IP traffic on a defined path through the network. This capability was not previously possible with IP traffic.
MPLS ACTIONS DESCRIPTION
Label created and distributed before any traffic begins the routers make the decision to bind a label to a specific FEC and build their tables. In LDP, downstream routers initiate the distribution of labels and the label/FEC binding. A reliable and ordered transport protocol should be used for the signaling protocol. LDP uses TCP. Table creation is done on receipt of label bindings each LSR creates entries in the label information base (LIB). The contents of the table will specify the mapping between a label and an FEC. Mapping between the input port and input label table to the output port and output label table. The entries are updated whenever renegotiation of the label bindings occurs.
SIGNALLING MECHANISMS
Label request:- Using this mechanism, an LSR requests a label from its downstream neighbor so that it can bind to a specific FEC. This mechanism can be employed down the chain of LSRs up until the egress LER (i.e., the point at which the packet exits the MPLS domain).
Label mapping:- In response to a label request, a downstream LSR will send a label to the upstream initiator using the label mapping mechanism. The above concepts for label request and label mapping are explained in Figure 2.
GMPLS ISSUES AND THEIR RESOLUTIONS
Data forwarding is not limited to that packet forwarding. The general solution must be able to retain the simplicity of forwarding using a label for a variety of devices that switch in time or wavelength, or space (physical ports).
Not every type of network is capable of looking into the contents of the received data and of extracting a label. For instance, packet networks are able to check the headers of the packets, check the label, and carry out decisions for the output interface (forwarding path) that they have to use. This is not the case for TDM or optical networks. The equipments in these types of networks are not designed to have the ability to examine the content of the data that is fed into them.
CONCLUSION
GMPLS will be an integral part of deploying the next generation network. It provides necessary bridges between IP and photonic dimensions. GMPLS provides interoperable,scalable and common control plane networks. Distributed network topology and resource availability advertisement. GMPLS protocol provides neighbor discovery and link management. Link management protocol provides fault detection and restoration of the network. GMPLS protocol provides high performance networks. GMPLS mainly focus on control plane (the management of connection) rather than the data plane(actual data traffic). GMPLS protocol replace SONET,ATM layer from the architecture. It provides two tier network layer architecture.
[attachment=57077]
ABSTRACT
In IP routing each packet travels from one router to the next, each router makes an independent forwarding decision for that packet. That is each router analyses packet header, and each router runs a network layer routing algorithm. Each router independently chooses a next hop for the packet, based on its analysis and the results of running the routing algorithm.
In conventional IP forwarding a particular router will typically consider two packets to be in the same FEC(forward equivalence class) if there is some address prefix X in that router's routing table such that X is the largest match for each packets destination address. As the packet traverses the network each hop in turn reexamines the packet and assigns it to the FEC.
Almost all protocols deployed today are based on algorithms designed to obtain the shortest path in the network for packet traversal and do not make into account of additional metrics (such as delay and congestion), which can further decreases the network performance. To speed up the forwarding scheme, a GMPLS device uses labels rather than address matching to determine the next hop for the received packet.
GMPLS is an extended framework of MPLS protocol. Generalized MPLS provides not also the packet switching but also switching in time slot domain(TDM), wavelength domain(DWDM),and space domain(fiber). In
MPLS the assignment of a particular packet to a particular FEC is done just once, as the packet enters the network. The FEC to which the packet is assigned and is encoded as a short fixed length value known as a label. When a packet is forwarded to its next hop, the label is sent along with it that is the packets are labeled before they are forwarded. GMPLS is a significant and challenging concept for next generation data and optical networks. By eliminating the two layers, ATM and SONET/SDH, GMPLS provides interoperable, scalable and parallel development of IP over DWDM network architecture.
INTRODUCTION TO GMPLS
The emergence of optical transport systems has dramatically increased the raw capacity of optical networks and has enabled new sophisticated applications. For example, network-based storage, bandwidth leasing, data mirroring, add/drop multiplexing [ADM], dense wavelength division multiplexing [DWDM], optical cross-connect [OXC], photonic cross-connect [PXC], and multiservice switching platforms are some of the devices that may make up an optical network and are expected to be the main carriers for the growth in data traffic.
Multiple Types of Switching and Forwarding Hierarchies
Generalized MPLS (GMPLS) differs from traditional MPLS in that it supports multiple types of switching, i.e. the addition of support for TDM, lambda, and fiber (port) switching. The support for the additional types of switching has driven GMPLS to extend certain base functions of traditional MPLS and, in some cases, to add functionality. These changes and additions impact basic LSP properties, how labels are requested and communicated, the unidirectional nature of LSPs, how errors are propagated.
MPLS BACKGROUND AND OPERATION
MPLS network consists of two types of devices. One is label switch router and another is label edge router. Label switch router is a high speed router in the core of the network. Label edge router separates the MPLS network and access network. Access network may be frame relay, ATM networks. A label is a short fixed length word which has local significance only. LER checks the IP header and inserts the label stack before the header in the IP packet. Label stack is a stack of labels each LSR only looks the topmost label in the stack, and switch the packet to the appropriate router. MPLS extended the suite of IP protocols to expedite the forwarding scheme used by IP routers. Routers have used complex and time-consuming route lookups and address matching schemes to determine the next hop for a received packet, primarily by examining the destination address in the header of the packet. MPLS has greatly simplified this operation by basing the forwarding decision on a simple label. Another major feature of MPLS is its ability to place IP traffic on a defined path through the network. This capability was not previously possible with IP traffic.
MPLS ACTIONS DESCRIPTION
Label created and distributed before any traffic begins the routers make the decision to bind a label to a specific FEC and build their tables. In LDP, downstream routers initiate the distribution of labels and the label/FEC binding. A reliable and ordered transport protocol should be used for the signaling protocol. LDP uses TCP. Table creation is done on receipt of label bindings each LSR creates entries in the label information base (LIB). The contents of the table will specify the mapping between a label and an FEC. Mapping between the input port and input label table to the output port and output label table. The entries are updated whenever renegotiation of the label bindings occurs.
SIGNALLING MECHANISMS
Label request:- Using this mechanism, an LSR requests a label from its downstream neighbor so that it can bind to a specific FEC. This mechanism can be employed down the chain of LSRs up until the egress LER (i.e., the point at which the packet exits the MPLS domain).
Label mapping:- In response to a label request, a downstream LSR will send a label to the upstream initiator using the label mapping mechanism. The above concepts for label request and label mapping are explained in Figure 2.
GMPLS ISSUES AND THEIR RESOLUTIONS
Data forwarding is not limited to that packet forwarding. The general solution must be able to retain the simplicity of forwarding using a label for a variety of devices that switch in time or wavelength, or space (physical ports).
Not every type of network is capable of looking into the contents of the received data and of extracting a label. For instance, packet networks are able to check the headers of the packets, check the label, and carry out decisions for the output interface (forwarding path) that they have to use. This is not the case for TDM or optical networks. The equipments in these types of networks are not designed to have the ability to examine the content of the data that is fed into them.
CONCLUSION
GMPLS will be an integral part of deploying the next generation network. It provides necessary bridges between IP and photonic dimensions. GMPLS provides interoperable,scalable and common control plane networks. Distributed network topology and resource availability advertisement. GMPLS protocol provides neighbor discovery and link management. Link management protocol provides fault detection and restoration of the network. GMPLS protocol provides high performance networks. GMPLS mainly focus on control plane (the management of connection) rather than the data plane(actual data traffic). GMPLS protocol replace SONET,ATM layer from the architecture. It provides two tier network layer architecture.