Optical IP Switching (OIS), is a novel method of creating transparent optical connections between network nodes using a flow-based approach. An IP flow is a collection of IP packets going from the same source to the same destination: the exchange of IP packets is the mechanism that allows the transport of information over the Internet.
The Internet Protocol (IP) is the principal communications protocol in the Internet protocol suite for relaying datagrams across network boundaries. Its routing function enables internetworking, and essentially establishes the Internet.
Recent studies have shown that Internet traffic presents a heavy tail distribution, where a small number of flows carries a huge amount of data. This suggests the possibility of dynamically adapting the optical connections to carry these heavy flows.
In probability theory, heavy-tailed distributions are probability distributions whose tails are not exponentially bounded: that is, they have heavier tails than the exponential distribution. In many applications it is the right tail of the distribution that is of interest, but a distribution may have a heavy left tail, or both tails may be heavy.
Currently a packet has to traverse a certain number of routers, before reaching its destination and the network routers must analyze each packet and forward it towards the direction of the destination node. However, since a flow is defined as a sequence of packets going from the same source to the same destination, if the router recognises the flow it could create a short-cut by creating a “switched” connection allowing all the packets belonging to the same IP flow to proceed directly towards the correct direction without being analyzed one after the other. This general idea is known as IP switching.
If the shortcut however occurs at an optical level, the process becomes Optical IP Switching. The advantage of OIS comes from the fact that today packets are transmitted optically between two points but at each routing station they have to be converted into electrical signal, routed and converted back into optical to continue their travel over the optical fiber. If instead the router is able to recognise a flow, it could create a shortcut (“cut-through connection”) directly at the optical level, and all the packets belonging to the same flow could be directed to the right destination without the optical-to-electrical conversion process. This would save time, energy, memory and processing resources on the router.
An optical fiber is a flexible, transparent fiber made by drawing glass (silica) or plastic to a diameter slightly thicker than that of a human hair. Optical fibers are used most often as a means to transmit light between the two ends of the fiber and find wide usage in fiber-optic communications, where they permit transmission over longer distances and at higher bandwidths than electrical cables. Fibers are used instead of metal wires because signals travel along them with less loss; in addition, fibers are immune to electromagnetic interference, a problem from which metal wires suffer excessively. Fibers are also used for illumination and imaging, and are often wrapped in bundles so they may be used to carry light into, or images out of confined spaces, as in the case of a fiberscope. Specially designed fibers are also used for a variety of other applications, some of them being fiber optic sensors and fiber lasers.
A basic implementation of the OIS concept sees an optical router that monitors IP traffic and if a flow appears with specific characteristics the router establishes an optical cut-through path between its upstream and downstream neighbours, requesting the upstream node to place all the packets belonging to the flow into the new path. The newly generated trail bypasses the IP layer of the router, as the packets transparently flow from the upstream to the downstream neighbour. Following a similar procedure the path can then be extended to more than three nodes, but this decision is always autonomously taken by each router and depends on the traffic encountered and on the resources locally available. Since an optical link however can carry several gigabits of data per second, it may be difficult to find a flow that alone can exploit the bandwidth offered by an optical trail. For this reason, aggregating more IP flows into the same dedicated path is essential for the performance of an OIS network. The aggregation introduces a trade-off between the number of IP flows that can be aggregated together and the length of the optical trail that accommodates them. In order to achieve good performance only optical flows sharing a significant number of network hops should be aggregated into the same path. A core node implementing optical IP switching must be endowed with electrical processing and memory resources (as a standard IP router), a variable number of optical transceivers and an optical switching element (usually a MEMS based device). An edge node instead does not need an optical switching device because it could only function as source or destination of the optical flow.
Microelectromechanical systems is the technology of microscopic devices, particularly those with moving parts. It merges at the nano-scale into nanoelectromechanical systems (NEMS) and nanotechnology. MEMS are also referred to as micromachines in Japan, or micro systems technology (MST) in Europe.
The control protocol nearest to OIS is probably GMPLS, which is being standardized by the IETF. GMPLS aims at creating end-to-end connections after an explicit request from a customer or a network engineering service. This constitutes the main difference with OIS where the optical trials are automatically triggered by the encountered traffic; they are initially generated between three adjacent nodes, and then extended following a distributed decision.
The Internet Engineering Task Force (IETF) is an open standards organization, which develops and promotes voluntary Internet standards, in particular the standards that comprise the Internet protocol suite (TCP/IP). It has no formal membership or membership requirements. All participants and managers are volunteers, though their work is usually funded by their employers or sponsors.
Multiprotocol Label Switching (MPLS) is a routing technique in telecommunications networks that directs data from one node to the next based on short path labels rather than long network addresses, thus avoiding complex lookups in a routing table and speeding traffic flows. The labels identify virtual links (paths) between distant nodes rather than endpoints. MPLS can encapsulate packets of various network protocols, hence the "multiprotocol" reference on its name. MPLS supports a range of access technologies, including T1/E1, ATM, Frame Relay, and DSL.
A router is a networking device that forwards data packets between computer networks. Routers perform the traffic directing functions on the Internet. Data sent through the internet, such as a web page or email, is in the form of data packets. A packet is typically forwarded from one router to another router through the networks that constitute an internetwork until it reaches its destination node.
Routing is the process of selecting a path for traffic in a network or between or across multiple networks. Broadly, routing is performed in many types of networks, including circuit-switched networks, such as the public switched telephone network (PSTN), and computer networks, such as the Internet.
Circuit switching is a method of implementing a telecommunications network in which two network nodes establish a dedicated communications channel (circuit) through the network before the nodes may communicate. The circuit guarantees the full bandwidth of the channel and remains connected for the duration of the communication session. The circuit functions as if the nodes were physically connected as with an electrical circuit.
Network topology is the arrangement of the elements of a communication network. Network topology can be used to define or describe the arrangement of various types of telecommunication networks, including command and control radio networks, industrial fieldbusses and computer networks.
A virtual circuit (VC) is a means of transporting data over a packet switched computer network in such a way that it appears as though there is a dedicated physical layer link between the source and destination end systems of this data. The term virtual circuit is synonymous with virtual connection and virtual channel. Before a connection or virtual circuit may be used, it has to be established, between two or more nodes or software applications, by configuring the relevant parts of the interconnecting network. After that, a bit stream or byte stream may be delivered between the nodes; hence, a virtual circuit protocol allows higher level protocols to avoid dealing with the division of data into segments, packets, or frames.
A digital subscriber line access multiplexer is a network device, often located in telephone exchanges, that connects multiple customer digital subscriber line (DSL) interfaces to a high-speed digital communications channel using multiplexing techniques.
Anycast is a network addressing and routing methodology in which a single destination address has multiple routing paths to two or more endpoint destinations. Routers will select the desired path on the basis of number of hops, distance, lowest cost, latency measurements or based on the least congested route. Anycast networks are widely used for content delivery network (CDN) products to bring their content closer to the end user.
The Resource Reservation Protocol (RSVP) is a transport layer protocol designed to reserve resources across a network for quality of service (QoS) using the integrated services model. RSVP operates over an IPv4 or IPv6 and provides receiver-initiated setup of resource reservations for multicast or unicast data flows. It does not transport application data but is similar to a control protocol, like Internet Control Message Protocol (ICMP) or Internet Group Management Protocol (IGMP). RSVP is described in RFC 2205.
NetFlow is a feature that was introduced on Cisco routers around 1996 that provides the ability to collect IP network traffic as it enters or exits an interface. By analyzing the data provided by NetFlow, a network administrator can determine things such as the source and destination of traffic, class of service, and the causes of congestion. A typical flow monitoring setup consists of three main components:
Connection-oriented communication is a network communication mode in telecommunications and computer networking, where a communication session or a semi-permanent connection is established before any useful data can be transferred, and where a stream of data is delivered in the same order as it was sent. The alternative to connection-oriented transmission is connectionless communication, for example the datagram mode communication used by the IP and UDP protocols, where data may be delivered out of order, since different network packets are routed independently, and may be delivered over different paths.
ASTN allows traffic paths to be set up through a switched network automatically. The term ASTN replaces the term ASON and is often used interchangeably with GMPLS. This is not completely correct as GMPLS is a family of protocols, but ASON/ASTN is an optical/transport network architecture. The requirements of the ASON/ASTN architecture can be satisfied using GMPLS protocols developed by the IETF or by GMPLS protocols that have been modified by the ITU. Furthermore, the GMPLS protocols are applicable to optical and non-optical networks, and can be used in transport or client networks. Thus, GMPLS is a wider concept than ASTN.
A computer network is a digital telecommunications network which allows nodes to share resources. In computer networks, computing devices exchange data with each other using connections between nodes. These data links are established over cable media such as wires or optic cables, or wireless media such as Wi-Fi.
A network socket is an internal endpoint for sending or receiving data within a node on a computer network. Concretely, it is a representation of this endpoint in networking software, such as an entry in a table, and is a form of system resource.
Resource Reservation Protocol - Traffic Engineering is an extension of the Resource Reservation Protocol (RSVP) for traffic engineering. It supports the reservation of resources across an IP network. Applications running on IP end systems can use RSVP to indicate to other nodes the nature of the packet streams they want to receive. RSVP runs on both IPv4 and IPv6.
In packet switching networks, traffic flow, packet flow or network flow is a sequence of packets from a source computer to a destination, which may be another host, a multicast group, or a broadcast domain. RFC 2722 defines traffic flow as "an artificial logical equivalent to a call or connection." RFC 3697 defines traffic flow as "a sequence of packets sent from a particular source to a particular unicast, anycast, or multicast destination that the source desires to label as a flow. A flow could consist of all packets in a specific transport connection or a media stream. However, a flow is not necessarily 1:1 mapped to a transport connection." Flow is also defined in RFC 3917 as "a set of IP packets passing an observation point in the network during a certain time interval."
An optical mesh network is a type of optical telecommunications network employing wired fiber-optic communication or wireless free-space optical communication in a mesh network architecture.
Link protection is designed to safeguard networks from failure. Failures in high-speed networks have always been a concern of utmost importance. A single fiber cut can lead to heavy losses of traffic and protection-switching techniques have been used as the key source to ensure survivability in such networks. Survivability can be addressed in many layers in a network and protection can be performed at the physical layer, Layer 2 and Layer 3 (IP).
Path protection in telecommunications is an end-to-end protection scheme used in connection oriented circuits in different network architectures to protect against inevitable failures on service providers’ network that might affect the services offered to end customers. Any failure occurred at any point along the path of a circuit will cause the end nodes to move/pick the traffic to/from a new route.
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