WO2006071131A1

WO2006071131A1 - Implementation method for a fixed optical communication network

Info

Publication number: WO2006071131A1
Application number: PCT/PT2004/000029
Authority: WO
Inventors: Fernando Manuel Da Velha FRAGOSO FREITAS SIMÕES
Original assignee: Fragoso Freitas Simoes Fernand
Priority date: 2004-12-27
Filing date: 2004-12-27
Publication date: 2006-07-06

Abstract

This invention relates to an implementation method for an optical, fixed communications network, with capillarity to the urban residential market. The network can be rapidly installed and is low in cost when compared to traditional urban landline fiber optic systems (FO). The aim is to obtain a high flow rate network, which is suitable for metropolitan area networks (MAN). Its main feature is the use of tree topology that connects various switches throughout the installation, (active network elements) Optical Ethernet, Layer 2 or Layer 3, thus obtaining low cost, high flow rate network segments, which have an availability of 99.999% and residential capillarity.

Description

DESCRIPTION

"IMPLEMENTATION METHOD FOR A FIXED COMMUNICATIONS NETWORK"

Scope of invention

This invention is for an alternative implementation method for a fixed, optical communication network, with residential capillarity.

Brief summary of the technique

Present methods for the implementation of fiber optics (FO) for the residential market (FTTH - Fiber To The Home) normally use FO together with different types of physical interfaces which seek to optimize, to a greater or lesser extent, the number of fibers installed and the flow rate obtained with different types of communications protocols and with greater or lesser traffic management capability. This is reflected in the type of communications services which are to be supplied to the end user and the possibility of inter operation between different networks with a view to maintaining the current models used by communication network operators in general. This type of infrastructure is normally slow to implement and is very costly. It also maintains a number of business models, which are based on the rental of already installed systems and does not allow designers to create geographically flexible networks. This has significant financial considerations.

The use of FSO equipment in communications networks which require availability of 99.999% has so far been impossible because of weather phenomena such as fog and the operating distances for which this equipment was designed do not allow this to happen. In this network, the interconnecting distances will not be greater than 165 meters, thus ensuring availability of 99.999%, under any type of weather conditions .

Recent advances in switching technology based on the new Optical Ethernet communications standard has resolved the problem of optimizing the flow rate through implemented fiber by achieving approximately 10 Gb with a single pair. Forecasts for the short-term point to flow rates of 100 Gb and even 1 TB. However, it is equipment that also depends on FO to achieve such high flow rates. If on one hand, the high flow rate contributes to the appearance of a single communications technology capable of resolving all flow rate requirements for different individual services, whether residential or commercial, the need to run slow and costly infra-structures does not allow lower service operating costs to be obtained which are compatible with the residential market. The fixed communications network for urban areas with high residential density using the PT 9886 utility model has explored alternative methods for constructing optical city networks for the first time. It employs the exclusive use of FSO instead of FO, so as to avoid the construction or use of existing city conduits, restricting the use of FO only in air installations between urban buildings and occasionally in local conduits existing between buildings . However, it did not resolve the problem of the propagation of the network in economically viable terms because the segmentation of the network for Layer 3 traffic was achieved through the unfavorable connection of FSO equipment in series, which presents disadvantages costs- wise when compared with traditional FO, although it is a more flexible solution geographically.

With the falling costs of implementing FO, the economic efficiency of the network using the PT 9886 utility model is lower and thus the need arises to make systems compatible but with the same efficiency, costs, speed of implementation, flexibility and maintenance of those with high flow rates, brought together in a new type of network. This is the subject of this patent request.

The author knows of the existence of other patents on communications networks . -A-

Documents WO 02/073845 and WO 02/075965 refer to such patents .

WO 02/073845, on a Free Space Optic Communication Network, describes a model in which the FSO are applied in a redundant manner so as to allow at least one FSO link to ensure communication. This model has a serious flaw as any localized fog can completely isolate a building and congestion of traffic in peripheral links can occur. Furthermore it is expensive - several FSO links per hub are required as well as a router to manage the different possible traffic paths - and it needs a building that is part residential and part commercial in order to be profitable. It is not exactly a residential model.

WO 02/075965 describes a series cascade connection in which FSO links are connected through a gateway (router) . In the topology of this request, the FSO links are interspersed with several switches over significant distances, given the interconnection distance of the FSO links. Most of the network, which is the subject of this new request, is effectively supported on the adjoining buildings that constitute the blocks and not on the FSO. However, request WO 02/075965 describes a model in which the links are connected for distances greater than 165 meters, which requires a router between 2 FSO links. This technology made sense when it became available as the Optical Ethernet switching technology was still only a project and the Ethernet switches at the time were suitable only for local networks (and the ATM switches were very expensive, as they still are today, to allow the existence of a network of the residential type) . Without routers interconnecting the FSO links directly, there could be no MAN.

Other documents describe ring connections of several FSO for MAN in which once again the FSO/ROUTER binomial is present . None of these documents mentions signal propagation exclusively in Layer 2 or otherwise in the last mile, but only in the method of signal propagation, always in Layer 3. Nor do any mention adjoining blocks of buildings, only isolated buildings. When there is Layer 2 traffic or local LAN using more than one switch, everything takes place within the building, which is served by the FSO/Router. Another important factor is that the operating distance of the FSO is never referred to because this factor is not important for the availability of the network with such topologies (although it is a serious flaw in all of them, and possibly for this reason none of the MAN characteristics are in operation) .

Brief description of the figure

The following description is based on the attached drawing, which without any limitations represents the network topology, which is the subject of this invention. Captions on figure:

R - main router, where the VLAN parameters are defined (Service Level Agreement, each VLAN corresponds to one service. Each end user can have more than one VLAN circuit, joined at a single point) .

S3 - Layer 2/Layer 3 switches capable of interpreting Layer 3 packages, only allowing the passage of Layer 3 traffic between routers and without traffic management functions, normally connected within the same block of adjoining buildings to S2 switches.

S2 - Set of switches capable of interpreting Layer 2 packages, connected in cascade, distributed throughout a series of adjoining buildings. L2- Layer 2 traffic L3- Layer 3 traffic

RSTP - redundant link, allows the RSTP (rapid spanning tree protocol) to function, with parameters to be defined in all S2 switches linked to the circuit.

The lines represent FSO or FO connections, in Layer 3 (bold) or in Layer 2, capable of IGB or multiples of IGB.

Detailed description of the invention

The network showed in the figure uses, during the first stage of propagation of the network's physical apparatus, one or more devices in the FSO network to interconnect between blocks of adjoining buildings at distances of no more than 165 meters. It uses air installations of fiber optic cables (FO) between buildings in the same block of adjoining buildings, which connect Layer 2 Switches in series (Switch capable of managing packages of data up to level 2) or Layer 2/Layer 3 Switches

(Switch with some level 3 capability) , installed in each building and so forth, thus constituting communication segments which can connect several blocks of adjoining buildings. Layer 2 switches are used when lines are present which cannot support more than one group of end users

(typically 1500, at the most) or Layer 2/Layer 3 switches when the interconnection of a large number of users is required over long distances in an urban environment together with Layer 3 traffic between routers, thus permitting connection between several Layer 2 communication groups. These network segments are derived from routers

(conductors) capable of traffic management and Service Level Agreement (SLA) maintenance for each end user, and together constitute a MAN network with equal management capability throughout.

Layer 2/Layer 3 (S3) Switches - are switches which are capable of addressing Layer 3 packages, but which maintain Layer 2 functionalities for the last mile and can thus be used as switches for the passage of traffic between routers (R) . The routers (R) continue their task of establishing permissions for each user (and for each service, through VLAN ID) , SLA. These Layer 2/Layer 3 switches can also increase the number of VLANs available in each segment but are not used for this purpose in this network. However in the near future, and after agreement with the manufacturer, it is expected that these switches will incorporate the functionalities inherent to the correct operation of SLA, permanently replacing higher cost routers, thus obtaining a more distributed network. It will also be more flexible and cheaper and not require changes to its topology.

This type of implementation permits rapid access by the end user to the network services, without having to depend on dedicated lines for the transport of data between routers (R) , as used to be the case in the network described in the PT 9886 utility model. In practice, it will have several alternative paths, can be temporary and replaced by FO at a later stage when considered advantageous (cost, flow rate, etc.) . The network, which is the subject of this invention, no longer uses the parallel installation of FSO at each section of the network as the only way of building a network of unlimited flow for Layer 2 or 3. It aims to use low cost switches in the last mile thus avoiding traffic management problems. This can also be achieved with several FO pairs using the same traffic aggregation standard as the Optical Ethernet, 802. lad.

As can be seen in the attached figure, the network has tree topology. This topology allows the connection, throughout the installation, of several Optical Ethernet switches (active network elements) , Layer 2 or Layer 3, in a cascade connection (not in series, defining

"lines" of communication as referred to in the previous techniques in the PT 9886 utility model, but in tree formation) .

This network topology is less flexible when compared to the network, which uses the PT 9886 utility model, in terms of re-locatable equipment, if the number of FO installations between adjoining buildings is significant, constituting fixed points of compulsory passage. However, it is much more flexible, especially in the last mile when compared to existing FO installations. It becomes even more flexible in terms of overall coverage as it no longer depends on dedicated Layer 3 connections to interconnect routers (R) . The tree topology also resolves the pressure of having network designers planning connections between several blocks of adjoining buildings in series, following a "line", forcing them to predict the design of the network in a specific area while also making the capillarity of the network in the residential market more effective. Such tree topology makes it more attractive commercially as it is easier to avoid passage points, which are not particularly viable from an economic perspective.

This new implementation introduces the possibility of the mixed use of Free Space Optics (FSO) equipment and land based fiber optics (FO) . As the costs of implementing land based fiber optics are falling, some sections of the network described can use FO instead of FSO. One of the main differences of this new network in relation to existing networks, more specifically those using the PT 9886 utility model, resides in the use of 100 Mb FSO for the last mile, with intensive use of the capability to aggregate Optical Ethernet traffic, which disappears in this new network, replacing the 100 Mb FSO with 1 Gb FSO, using the aggregation of links to a lesser degree and always for multiples of 1 Gb. The S3 switches also support traffic at 10 Gb and in the near future, the introduction of specific equipment at 10 Gb is expected for the network, which is the subject of this request. The increase in the flow rate capability of this new network over existing networks is highly significant.

This new topology allows us to predict that if the implementation cost of FO falls much lower than the cost of FSO, the network described will become a temporary model for the implementation of an optical network, although one, which maintains the characteristics and aims of the network, described.

Claims

1. Implementation method for a fixed optical communications network of the type, which uses FSO - Free Space Optics, an abbreviation applied to data transmission/reception equipment using infra-red radiation rays, characterized by a tree topology capable of connecting throughout the installation, various (active network elements) Optical Ethernet switches, Layer 2 or Layer 3 (switch with Layer 2 or Layer 3 capability for the management of data packages) , thus obtaining high flow rate network segments, at low cost, with availability of 99.999% and residential capillarity.

2. Implementation method for a fixed communications network, in accordance with claim 1, characterized by the use of (FSO - Free Space Optics) equipment at distances of less than 165 meters to connect between different blocks of adjoining urban buildings.

3. Implementation method for a fixed optical communications network, in accordance with claim 1, characterized by the use of the front of buildings or local conduits, should they exist, for the passage of fiber optical between each building, at each block of adjoining buildings .

4. Implementation method for a fixed optical communications network, in accordance with claims 1 to 3, characterized by the possibility of being able to interconnect several FO pairs and/or several FSO devices at each section between adjoining blocks of buildings, making use of the traffic aggregation capability of the Optical Ethernet communications protocol, thus constituting a network of virtually infinite flow rate throughout and at any section, allowing the removal of traffic management at network stages supported exclusively as Layer 2.

5. Implementation method for a fixed optical communications network, in accordance with claims 1 to 4, characterized by any segment, as long as it is equipped with Layer 2/Layer 3 switches, being able to transport Layer 3 traffic between routers, thus constituting alternative paths for the transport network.