White PapersMetropolitan ring designs remain very popular because the configuration enables a business to handle multiple voice and data applications on a single, highly reliable network, while extending LANs across multiple infrastructures. A typical ring design consists of Nodes, Ports and Fiber. A Node provides connectivity to the ring at customer premises locations and Central Office (CO)/Point of Presence (POP) locations. The Node at the CO/POP performs network monitoring, and is where ingress and egress from the private ring takes place. Ports provide a service interface to the node (i.e. “on ramp”), and are configured to the speed and protocol of the requested service. Nodes are connected via diverse fiber pairs. Fiber is the medium used to transport data around the ring.
Ring solutions are often used for data mirroring, storage applications and network access consolidation. They also enable more rigorous continuity and disaster recovery options. Two optical standards are used today with ring architectures to transport information. They are Synchronous Optical Network (SONET) and Dense Wave Division Multiplexing (DWDM). Each delivers particular benefits, meeting the growing needs of diverse business situations.
Choosing the Right MetropolitanRing for Your BusinessIntroductionBusinesses are evolving and looking for more effective and efficientmethods of handling bandwidth, performance and end-point needs. In addition, they are trying to anticipate future needs to help makegood networking decisions. Metropolitan ring solutions are being usedto consolidate network access facilities for multiple locations, connectingthem with each other, the WAN, the Internet and with commoncarriers and carrier hotels. Instead of maintaining an array of separateaccess connections at each building, the enterprise can link offices tocarrier and WAN facilities through a high-speed ring network. Theconsolidation of traditional transport access services can also reduceoverall access costs. Metropolitan ring designs remain very popular because the configurationenables a business tohandlemultiplevoiceand data applications on asingle, highlyreliable network, while extending LANs across multipleinfrastructures. A typical ring design consists of Nodes, Ports and Fiber.ANode provides connectivity tothe ring at customer premises locationsand Central Office (CO)/Point of Presence (POP) locations. The Nodeat the CO/POP performs network monitoring, and is where ingressand egress from the privatering takes place. Ports provide a serviceinterface to the node (i.e. on ramp ), and are configured to the speedand protocol of the requested service. Nodes are connected viadiverse fiber pairs. Fiber is the medium used to transport data aroundthe ring. Ring solutions are often used for data mirroring, storage applicationsand network access consolidation. They also enable more rigorouscontinuity and disaster recovery options. Two optical standards areused today with ring architectures to transport information. They areSynchronous Optical Network (SONET) and Dense Wave DivisionMultiplexing (DWDM). Each delivers particular benefits, meeting thegrowing needs of diverse business situations.This is a diagram showing a typical Metropolitan Ring Architecture.Rings arecomposed of three basic components: nodes, ports andfiber. Rings are connected through fiber connections. Fiber is themedium used totransport dataaround the ring. SONETSONET is an optical standard that is a widely recognized across theglobe. This standard provides high-speed, fiber-based, full-duplexcapabilities for voice, video and data. SONET is an ideal choice forsupporting high bandwidth and failure resistant technologies. Manybusinesses use SONET as a dedicated privatenetwork to carry alltraffic between metro locations, voice and data providers and Internetfacilities. It uses a timing element to synchronize transmissionsbetween sender and receiver,so datacan be sent as large packets orblocks, instead of as individual characters. By dedicating individualtime slotsfor each service, the synchronization aspect of SONETallows manylower speed services tobe transported within a single,high-speed circuit. This allows data to travel the ring simultaneously at O VERVIEWC all Centerustom er LocationP rT&T/Node/PortF iberData CenterNetwork Ring TechnologyUntitled Documentveryfast speeds. Each time slot can be configured to the specificspeed and protocols of its service application, helping to ensure thequality of service and performance. SONET is a great choice when network security is a concern. Due tothe nature of fiber-based service, it is impossible to Wire-Tap fibersince the fiber itself is made up of strands of glass. Traffic ridingacross fiber travels in light pulses, eliminating eavesdropping. Unlikewith copper connections, there is no cross traffic traveling on the fibernetwork. Should the fiber get Tapped into, the glass connectionswould break. If there is a physical break in the fiber, a SONET networkwill immediately detect it, trigger a service alarm and reroute the trafficacross the network. SONET s self-healing network can detect fiberpath outages and restore alternative routing within 50 milliseconds.Diversity options are also available by provisioning dual accessconnections entering the building at different locations. This helpsensure that there is no single point of failure. Businesses that use SONET Rings may realize savings in access andmanagement costs. For example, a communications company usedSONET to connect multiple locations within a Metro. One locationincluded a data center, connected to a back-up data center, whichhosted sensitive records needing to be accessed from other locations.Another location was a call center requiring a large volume of voicetraffic, while simultaneously accessing information from the datacenter, the Internet and other locations. All locations were makingbasic data transmissions (e-mail). Frame Relay, ATM, DS3 s and T1 swere being used and managed separately. The company consolidatedthese services onto a single SONET network, reducing the number ofaccess points, providing greater security, improving reliability andrequiring fewer people to monitor and manage the network. SONET may also be designed with other popular features that may nothave been available last year, such as Ethernet over SONET andResilient Packet Ring Resilient (RPR). Resilient Packet Ring is a SONET-based feature. It was established according to IEEE 802.17, a standarddesigned for optimized transport of data traffic over fiber rings. RPR isdesigned to provide the resilience of SONET/SDH networks, but withpacket-based transmission. As a feature of SONET, RPR will carve outapiece of the SONET ring to dedicate to transport packet-basedEthernet traffic. The remaining bandwidth can be used to transporttraditional SONET (OCx, DSx) traffic. The Ethernet traffic carried on theRPR inherits all the benefits of the underlying SONET ring, such asprotection switching. By treating all data as packets instead of asindividual streams, RPR can increase the efficiency of Ethernet and IPservices. RPR can help companies justify the investment of a privatefiber network by using it as an Ethernet transmission medium. Theubiquity of Ethernet in many business environments can make RPR anattractive option. ASONET Ring should be considered if an enterprise:"Is carrying traffic larger than DS3 between 2 or more locations"Is implementing a strategic plan that anticipates network growth"Demands network reliability and redundancy, with overallsurvivability for critical applications"Requires private, dedicated network for sensitive applications"Needs to link multiple sites together"Requires guaranteed high performance and reliability (SONETcarries 99.999 reliability)DWDMDWDM is often called the next generation of SONET. However, it isactually not SONET protocol at all. DWDM is an optical technologyused to increase bandwidth over existing fiber optic backbones. It iscomplementary to SONET, in that SONET can be transported across aDWDM-based network. DWDM works by combining and transmittingmultiple signals simultaneously, at different wavelengths, on the samefiber. Basically, one fiber is transformed into multiple virtual fibers.Multiplexers are used at each entry and exit point to assign particularkinds of communication to particular wavelengths of light on the ring.This effectively partitions the fiber so that different kinds of traffic cantravel simultaneously without interference. This approach is protocoland bit-rate independent. DWDM networks can carry different typesof traffic at different speeds.DWDM allows for multiple protocols at the wavelength level, anddifferent protection options as well. That means DWDM networks caninclude extraprotection on certain kinds of traffic, but not on other,less-sensitive traffic. For example, a hospital might apply extraprotection to ensure that the connections that carry patient recordinformation arebeing carried to the Storage Area Network and DataCenters, while lower priority traffic such as email and Internet accesscould be delivered via a more traditional DWDM protection design. Bymanaging the network down tothe wavelength, IT managers canmake sure that they are using the DWDM ring to it s full potential. Thisenables businesses to save money in overhead, operating costs, aswell as upgrade and future build out costs.Like SONET, it can be very cost-effective by allowing users manage alltheir traffic over one flexible and secure network. However, DWDMgoes a step further by supporting most common Optical protocols. It can support SONET,video, storage and Ethernet on a single DWDM-enabled ring. SONET can only support SONET protocol traffic(including Ethernet over SONET), which is sufficient for many users.Applications such as broadcasting, which use video protocol, performbetter on DWDM because it does not need to be translated to SONET. Storage Area Networks (SANs) are one of the main drivers forcustomers toselect DWDM. Because DWDM transports native SANprotocols, it saves IT managers the extra expense of translating SANtraffic from the servers into another protocol to traverse the network.In addition, DWDM has preferred protection options that help avoidthe substantial business and financial risks and potential lossassociated with lost data, data recovery and downtime that may bepresent whileusing a less reliable network.OverView - Network Ring Technology__________________________________________________________________________________________________________2Untitled DocumentDWDM should be considered if an enterprise:"Has multiple locations that need to be connected"Needs a Storage Area Network"Requires support for bandwidth intense applications"Needs to place different protection options on each application"Needs to support multiple protocols"Is growing beyond a standard OC42 SONET in the next few yearsMaking the ChoiceChoosing a ring technology is a matter of striking a balance betweencost, security, protection, bandwidth and anticipated future growth.SONET is a good choice for companies with two or more locations in asingle metro that may be looking to consolidate transport services.Due to the inherent self-healing ability of SONET, it is a solution forbusinesses needing optimal security and reliability. SONET also offersbusinesses the ability to transport traditional Ethernet traffic via theRPR feature. DWDM addresses many of these requirements, but is abetter choice if a business needs more protocol options than SONETgives, wants to provide a storage area network, needs to supportbroadcast video, needs to provide different levels of protection forapplications, or uses multiple bandwidth-heavy applications. Security is the number one value in anyoptical network. SONET andDWDM can both be deployed within a dedicated optical network inwhich the fiber and itsassociated hardwareareprovided for theexclusive use of a single customer. No other business can use thesame fiber components. The networks may be designed with diverseentry points to further ensure no single point of failure. Ringarchitectures are known for their reliability and performance, andprovide the most value to businesses needing the combination of highsecurity and heavy bandwidth. Health care companies, financialservices firms, government agencies and broadcasters are leaders inthe deployment of private optical networks.The technology of optical networking is a very dynamic area.Interested enterprises need to review their entire network portfolio(conduct a complete inventory) to understand where they canconsolidate services to maximize efficiencies and save costs. In orderto optimize on network investments, businesses should create anetworking plan with at least three years outlook to anticipate futuregrowth, technology trends and bandwidth needs. It can be costly andtime consuming to build and deploy a new network. Designing anetwork that will work now and a few years forward is a sensible wayto make technology investments.When planning an optical ring, or when considering ring upgrades, it simportant to work with a partner that understands the benefits andlimitations of each technology. AT&T is a recognized leader in fiberoptics, experienced in the pros and cons of current standards, andengaged in the evolution of future specifications. AT&T uses ringarchitectures to carry traffic within its own network. With acomprehensive set of ring products and technologies, and a broadglobal footprint, A&T helps enterprises configure custom ring networksthat meet their individual needs, now and for the future. For more information contact your AT&TRepresentative or visit us at www.att.com/business.OverView - Network Ring Technology__________________________________________________________________________________________________________301/05/07 AB-0934 2007 AT&T Knowledge Ventures. All rights reserved. AT&T is a registered trademark of AT&TKnowledge Ventures.
