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Gigabit Ethernet and ATM

A Business Perspective by Nortel Marketing

Bursty, high-bandwidth applications are driving the need for similarly high-bandwidth campus backbone infrastructures. Today, there are two choices for the high-speed campus backbone: ATM or Gigabit Ethernet. Which is a "better" technology choice is no longer in doubt — Gigabit Ethernet has clearly won hands down. This paper briefly presents, from a business perspective, why Gigabit Ethernet is the best choice for most enterprise LANs.

Great advances in processor power, memory, and data storage in servers and workstations are enabling the kinds of applications only imaginable a few years ago – multimedia, multicolor graphics, animation, real-time video, voice and data.

Some of these applications churn out massive amounts of traffic, sometimes in huge bursts, that require large amounts of bandwidth in the supporting network infrastructure when the end stations are connected by campus Local Area Networks (LANs) and backbones.


In the past, most campuses have used shared-media backbones — such as 16/32 Mbps Token-Ring and 100 Mbps FDDI — that are only slightly higher in speed than the accessing LANs and end stations they interconnect. The result has been severe congestion in the campus backbones when these backbones interconnect a number of access LANs. At a minimum, a high capacity, high performance, and highly resilient backbone is needed — one that can be scaled as end stations grow in number or demand more bandwidth. Also needed is the ability to support differentiated service levels (Quality of Service or QoS), so that high priority, time-sensitive, and mission-critical applications can share the same network infrastructure as those that require only best-effort service. Today, there are two principal technology choices for the high-speed campus backbone: ATM or Gigabit Ethernet. While both seek to solve the backbone congestion and differentiated QoS problems in the enterprise environment, each is very different in nature from the other. Which is a "better" technology is no longer a subject of industry discussion – Gigabit Ethernet has clearly won hands down in the enterprise campus backbone. The reasons for this are many and includes the following: • Gigabit Ethernet’s 1 Gbps bandwidth is sufficient to meet the needs of most enterprise network application requirements today, with work on multi-Gigabit link aggregation and 10 Gbps Ethernet under way for greater bandwidth resiliency and scalability in the future. • Gigabit Ethernet is inexpensive compared to ATM, with ATM currently costing 2 to 3 times as much per port as Gigabit Ethernet and with even greater cost reductions for Gigabit Ethernet in the future. • Derived from a well-proven and simple technology, Gigabit Ethernet as an enterprise campus backbone integrates seamlessly with the millions of connectionless and frame-based Ethernet and Fast Ethernet desktops that are installed in many campus networks. In contrast, connectionoriented and cell-based ATM needs to emulate the installed connectionless campus networks as well as provide frame-cell conversion - functions that add greatly to its complexity. • Complexity in a technology such as ATM not only costs more for the initial hardware and software acquisition but also results in much higher costs for testing, deployment, operational support, problem resolution, skills training and even lost business opportunities during network outages. There are fewer ATM skilled personnel available, which leads to increased cost in Human Resources hiring and retention programs. In contrast, ubiquitous Ethernet and Fast Ethernet provide the network administration and management skills that are leveraged by Gigabit Ethernet without additional costs. • Gigabit Ethernet provides a powerful evolution path from currently installed Ethernet and Fast Ethernet for low-cost basic connectivity and bandwidth, with higher-layer Internet Protocol (IP) capabilities added incrementally when needed. These capabilities include policy enabled networking, using protocols such Common Open Policy Services, Lightweight Directory Access Protocol, Dynamic Host Configuration Protocol, Domain Name System, and Differentiated Services for differential Quality of Service. • Enhanced by routing switch technology, such as that available in Nortel Networks Passport* 8000 Enterprise Switches and Passport 1000 Routing Switches, Gigabit Ethernet offers Layer 2/3 switching performance at wire speed, while providing rich differentiated services through Express Classification capabilities and Optivity* Policy Services management software at a much lower cost than ATM (see Figure 4 on page 13). • While functionally rich, ATM capabilities are offered with all their complexities all at once at a high price, whether these capabilities are even needed or can be exploited in full. • Considered a local area network technology, Gigabit Ethernet today holds great promise even for connectivity across the metropolitan and wide area networks, with the development of long-haul extended distance Gigabit Ethernet, Packet over SONET, Dense Wave Division Multiplexing and low-cost fiber optic cabling. Many business users have chosen Gigabit Ethernet as the backbone technology for their campus networks. An Infonetics Research survey (March 1999) records that 91 percent of respondents believe that Gigabit Ethernet is suitable for LAN backbone connection compared with 66 percent for ATM. In selecting Gigabit Ethernet, users have gone back to the business basics of determining: • What are the user requirements? • How does the selected technology meet today’s business needs? • What benefits does the technology provide? • How much does the technology cost in total ownership? • What is already installed today that needs compatibility and integration, and can be leveraged? • How will it position the business for tomorrow’s requirements? • What are the trends and developments regarding pricing, availability, functional enhancements and interoperability? This paper provides a business-level view of the ATM and Gigabit Ethernet technology choices from an enterprise campus network standpoint. While ATM may be appropriate for multiservice consolidation and transport over metropolitan and wide area networks, Gigabit Ethernet meets the needs of the majority of enterprise networking requirements today. Gigabit Ethernet seamlessly integrates with installed desktops, servers and applications, while providing the required additional bandwidth, functionality, scalability and performance. Gigabit Ethernet offers simplicity and with much lower cost of ownership while strategically positioning the enterprise for the future. A more detailed technical paper on the decision points between ATM and Gigabit Ethernet technology is also available from Nortel Networks.

Asynchronous Transfer Mode (ATM)

Asynchronous Transfer Mode (ATM) has been used as a campus backbone technology since its introduction in the early 1990s. ATM is specifically designed to transport multiple traffic types — data, voice and video, real-time or non-real-time — with inherent QoS for each traffic category. To enable this and other capabilities, additional functions and protocols are added to the basic ATM technology. Private Network Node Interface (PNNI) provides OSPF-like functions to signal and route QoS requests through a hierarchical ATM network. Multiprotocol over ATM (MPOA) allows the establishment of short-cut routes between communicating end systems on different subnets, bypassing the performance bottlenecks of intervening routers. Much has been done, and is still being enhanced, in the areas of physical connectivity, bandwidth scalability, signaling, routing and addressing, security, and management. While rather rich in functions, this functionality has come with a fairly heavy price tag in terms of complexity and cost. To provide backbone connectivity for today’s legacy access networks, ATM, a connection-oriented technology, has to emulate the capabilities that are inherently available in the predominantly connectionless LANs including broadcast, multicast, and unicast transmissions. ATM must also manipulate the predominantly frame-based traffic on these LANs, segmenting all frames into cells prior to transport, and then reassembling cells into frames prior to final delivery. Many of the complexity and interoperability issues are the result of this LAN Emulation, as well as the need to provide resiliency in these emulated LANs. Many components are required to make this workable. These components include the LAN Emulation Configuration Server(s), LAN Emulation Servers, Broadcast and Unknown Servers, Selective Multicast Servers, Server Cache Synchronization Protocol, LAN Emulation User Network Interface, LAN Emulation Network Network Interface, and a multitude of additional protocols, signaling controls, and connections (point-to-point, point-to-multipoint, multipoint-to-point, multipoint-tomultipoint). Until recently, ATM was the only technology able to promise the benefits of QoS from the desktop, across the LAN and campus, and right across the world. However, the deployment of ATM to the desktop, or even in the campus backbone LANs, has not been as widespread as envisaged. Nor have there been many native applications available or able to benefit from the inherent QoS capabilities provided by an end-to-end ATM solution. Thus, the benefits of end-to-end QoS has been more imagined than realized. Gigabit Ethernet as the campus backbone technology of choice is now surpassing ATM. This is due to the complexity and the much higher pricing of ATM components such as network interface cards, switches, system software, management software, troubleshooting tools, and staff skill sets. There are also interoperability issues, and a lack of suitable exploiters of ATM technology.



Gigabit Ethernet

Today, Gigabit Ethernet is a very viable and attractive solution as a campus backbone LAN infrastructure. Although relatively new, Gigabit Ethernet is derived from a simple technology, and a large and well-tested Ethernet and Fast Ethernet installed base. Since its introduction, Gigabit Ethernet has been vigorously adopted as a campus backbone technology, with possible use as a high-capacity connection for high-performance servers and workstations to the backbone switches. The primary reason for this success is that Gigabit Ethernet provides the functionality that meets today’s immediate needs at an affordable price, without extraneous complexity and cost. Gigabit Ethernet is complemented by a superset of functions and capabilities that can be added as needed, with the confident promise of further functional enhancements and bandwidth scalability (for example, IEEE 802.3ad Link Aggregation and 10 Gbps Ethernet) in the near future. Thus, Gigabit Ethernet provides a simple scaling-up in bandwidth from the 10/100 Mbps Ethernet and Fast Ethernet LANs that are already massively deployed. Simply put, Gigabit Ethernet is Ethernet but 100 times faster! Since Gigabit Ethernet uses the same frame format as today’s legacy installed LANs, it does not need the segmentation and reassembly function that ATM requires to provide cell-to-frame and frame-to-cell transitions. As a connectionless technology, Gigabit Ethernet does not require the added complexity of signaling and control protocols and connections that ATM requires. Finally, because QoS-capable desktops are not readily available, Gigabit Ethernet is no less deficient in providing QoS. As we shall see, new methods have been developed to deliver QoS and other needed capabilities in a gradual and granular manner that lend themselves to much more pragmatic and cost effective adoption and deployment. To complement the high-bandwidth capacity of Gigabit Ethernet as a campus backbone technology, higher-layer functions and protocols are available, or are being defined by standards bodies such as the Institute of Electrical and Electronics Engineers (IEEE) and the Internet Engineering Task Force (IETF). Many of these capabilities recognize the desire for convergence upon the ubiquitous Internet Protocol (IP). IP applications and transport protocols are being enhanced or developed to address the needs of high speed, multimedia networking that benefit Gigabit Ethernet. Differentiated Services (DiffServ) provides differential QoS that can be deployed from the Ethernet and Fast Ethernet desktops right across the Gigabit Ethernet campus backbones. The use of IEEE 802.1Q VLAN Tagging and 802.1p User Priority settings allow different traffic types to be accorded the appropriate forwarding priority and service. When combined with policy-enabled networks, DiffServ provides powerful secure, and flexible QoS capabilities for Gigabit Ethernet campus LANs, by using protocols such as Common Open Policy Services (COPS), Lightweight Directory Access Protocol (LDAP), Dynamic Host Configuration Protocol (DHCP), and Domain Name System (DNS). Further developments with Resource Reservation Protocol, multicasting, real-time multimedia, audio and video transport, IP telephony, and others will add functionality to a Gigabit Ethernet campus with a gradual and manageable approach, when these functions are needed by users.

User Requirements

In deciding which campus technology should be employed, user requirements are paramount. While the following may be self-evident truths, it is worth stating that: • No technology is of any use unless it meets what the user wants it to accomplish, regardless of how elegant or inexpensive it may be. • Some technologies offer more than is needed to be accomplished, with unused features and functions, and with added complexity and/or cost that provide no benefit. • Some technologies need additional complementary technologies that are not available and, therefore, cannot be fully exploited. • Some technologies meet basic user requirements at a reasonable cost today, and serve as building blocks for other technologies to complement and add greater functionality tomorrow. Keeping the above in mind, we should ensure that the following key requirements are satisfied, whether the choice is ATM or Gigabit Ethernet: • Meet today’s application requirements • Minimize the total cost of ownership • Maximize the benefits of ownership today • Position for tomorrow’s application requirements.

Meet Today’s Application Requirements

While it is necessary to keep an eye on the future, the first basic requirement is that current needs must be satisfied. With such increasingly fast-paced changes in consumer tastes, wants and needs, competitive challenges, regulatory environment and technology development, what seems promising today for the long-term may turn out to be untrue, and can sometimes saddle the business with obsolete and expensive equipment that was thought to be "future-proof." In looking at user requirements for campus networking, we should consider the following: • Identify the different types of voice, video and data application traffic and service profiles that the network infrastructure will need to support. • Categorize the application traffic types that are time-critical and/or mission-critical versus those of lesser importance. Data is useless if it does not get to the intended destination at the appropriate time, and thus results in lost business or degraded customer satisfaction). • Prioritize the different traffic types and users. Intranet browsing, real customers making e-commerce purchases, important strategic customers seeking purchase information, and interactive versus batch applications all require very different priorities in servicing. Since resources are scarce and cannot satisfy all demands at the same time, the ability to provide preferential treatment to the traffic that is more important to your business is essential. • Specify a high level of resiliency and availability features in network elements and application servers. Network downtime equates to lost business and customer dissatisfaction, sometimes with long-term or disastrous consequences. • Ensure a high level of performance from the network elements and servers in the initial design and implementation. These components typically require high bandwidth, raw capacity, and processing power.


Ensure system scalability in order to accommodate customer growth or increased business volume. Typical scalability factors include the ability to enhance performance or incrementally add more hardware, ports, or switching capacity. • Ensure ease of deployment, integration, and migration from the existing LANs. Given that the majority of LANs are Ethernet or Fast Ethernet, Gigabit Ethernet presents the smoothest path to the next order of high bandwidth capacity. • Ensure ease of manageability with integrated management elements that work seamlessly, therefore incurring lower costs. These must be comprehensive and easy to use, covering all managed elements wherever and whenever needed.

ATM versus Gigabit Ethernet:

In comparing ATM with Gigabit Ethernet, it is clear that much of today’s application and traffic requirements in the campus environment can be met by Gigabit Ethernet technology, complemented by higher layer functions such as Differentiated Services and policyenabled networking. While ATM provides an "overkill" in meeting some requirements, it does not satisfy other requirements, especially in ease of deployment, integration, migration, and management. Gigabit Ethernet provides all the basic requirements necessary for business at a reasonable cost today, while remaining flexible enough to meet future needs.



Minimize the Total Cost of Ownership

A significant factor in the Total Cost of Ownership (TCO) of any networking technology is its overall complexity. While it is true that greater functionality may result in greater complexity, greater complexity does not necessarily yield greater functionality. A further consideration is whether or not the additional functionality is a requirement, an optional feature, or simply unnecessary.




Network infrastructure should never be deployed based upon cost alone. Instead, the deployment goal should be a networking solution that provides the maximum required functionality while imposing minimum complexity and cost. Why pay for more than is necessary? Why pay for features and functions that will not be used for some time, or may never be used? Simpler technology means a less costly network. Complexity imposed by the technology is a major contributor to the Total Cost of Ownership. Figure 1 shows an example of network design complexity. The left half of the figure shows a multi-tiered network with specialized equipment types for access, distribution, core transport, server aggregation, and routing. This is an unnecessarily complex and costly solution when compared with a simpler two-tiered architecture. The right half of the figure shows an example of a two-tiered architecture provided by the Nortel Networks Passport Campus Solution, consisting of the Passport 8000 Enterprise Switch, the Passport 1000 Routing Switch family, Passport 700 Server Switch family and BayStack* 450 Ethernet Switches. Reducing the number of different component types in the network will invariably minimize the complexity and Total Cost of Ownership. Figure 2 shows an example of network technology complexity. The vectors shown in the figure represent the essential virtual connections between required logical components when using ATM to emulate a connectionless LAN environment. These logical entities are not needed at all when deploying Gigabit Ethernet technology, since the connectionless LAN environment is completely native to Ethernet.




Deploying either complex network designs or complex network technology, such as ATM, can adversely impact Total Cost of Ownership in the following ways: • More expensive initial hardware and software acquisition • More training and education, as well as time spent on the learning curve • Longer testing, implementation, and deployment schedules • More difficult problem determination and resolution procedures • Longer downtime due to extended difficult problem determination and resolution • Ongoing operational support • New hardware acquisition or hardware and software upgrades.

ATM versus Gigabit Ethernet:

In comparing ATM with Gigabit Ethernet, it is clear that ATM is a more complex and costly technology. The comparative cost of the two is a significant decision criterion. The price-per-port for ATM is almost twice that of Gigabit Ethernet, with the price gap between the two expected to widen in the future as Gigabit Ethernet pricing decreases even further.



Maximize the Benefits of Ownership Today

Even if a technology holds a lot of promise for tomorrow, it is necessary to realize that businesses are held accountable by their owners, shareholders, and customers today. While this does not imply that long-term strategies and plans are unnecessary, the benefits and returns on investment on the network infrastructure must be visible and available — in some cases, almost immediately upon deployment. This is because of the extremely dynamic and non-stop nature of the global networked economy of the 21st Century. Shifting alliances, partnerships, mergers and cooperative efforts to meet ever-changing business challenges and competitive pressures require open and interoperable networking technologies that lend themselves to seamless and rapid integration. This allows the objectives and benefits of such alliances and partnerships to be realized rapidly. This integration can be made more smoothly by deploying a network technology that is adopted everywhere because of its functionality, simplicity, cost, and its history of evolutionary growth and scalability. Another important consideration in seeking to maximize the benefits of ownership is the cost of that ownership. The lower the Total Cost of Ownership, the greater the probability of maximizing benefits.

ATM versus Gigabit Ethernet:

In comparing ATM with Gigabit Ethernet, there is no doubt that Gigabit Ethernet lends itself more easily to seamless and rapid integration because of its technological affinity with the millions of Ethernet and Fast Ethernet end stations installed in today’s networks. There is also no doubt that Gigabit Ethernet is much lower in cost than ATM. Thus, benefits of ownership can be maximized and realized almost immediately upon deployment.

Position for Tomorrow’s Application Requirements

As previously mentioned, the decision for a network technology has to be based on meeting today’s needs. Over the last decade, we have seen the rise of LANs, VLANs, bridges, routers, routing switches, switching routers, Fast Ethernet, Fast Token-Ring, Gigabit Ethernet, ATM, SONET, DWDM, wireless, wireline, copper cabling, fiber optics, Layer 4-7 switches, the collapse of collapsed router backbones, the rush to embrace multiprotocol networking, and the rush back to IP. We have also seen the alphabet soup of ATM, RSVP, Integrated Services, Differentiated Services, COPS, MPLS, MPOA, NHRP, and many others still cooking in the technology pot. Which of these technologies will prevail and which will not is left to be seen.




Given the rapid pace at which network technologies and products are being introduced into the market to meet the even more rapid changes in the business environment — Internet, intranet, extranet, e-commerce, multimedia non-stop trading, global networked economy, upstarts and startups — positioning for tomorrow’s application requirements is not the first consideration in the decision. In fact, businesses usually include a degree of planned obsolescence in the technology and products selected. Still, to maximize the benefits and returns on investment in the network infrastructure, it would obviously be better if the networking technology selected has a long, useful life. In determining the longevity of the investment and positioning for tomorrow’s requirements, we should consider the following factors: • History, experience, and expertise of the vendor in providing technology, products and solutions in the critical areas of voice and data integration, and LAN, MAN and WAN integration. While product speeds and feeds are important, the vendor’s long-term strategic vision, combined with the ability to provide immediate real world business solutions, are critically important. • The vendor’s ability to provide a comprehensive end-to-end unified network solution. • The vendor’s willingness and ability to contribute to new technology standards, research, and development. • The vendor’s strategies and roadmaps provided to transition from today’s product set to future technologies. • The vendor’s ability to innovate and harness disruptive technologies for business ends. • Market realities, actual standards and function development, and adoption in the marketplace. In all the above aspects, Nortel Networks has one of the best track records in both the voice and data world, delivering "five 9s" (99.999 percent) reliability, and consistent leadership in providing innovative and comprehensive networking solutions. Nortel Networks provides the solutions that enable businesses to choose a IP-enabled voice or telephony-enabled IP networking strategy that best suits their needs. Now, with Nortel Networks Internet Communications Architecture (INCA), businesses can realize the benefits of voice and data convergence. INCA offers solutions that enable businesses to choose an IP-enabled voice network strategy or a telephony-enabled IP network strategy that best suits their needs. INCA is also evidence of Nortel Networks leadership in providing solutions that are not only timely and comprehensive but also position businesses for new application requirements, thus protecting their network investments.



Market Realities

In deciding which network technology to adopt — ATM or Gigabit Ethernet — the realities of the marketplace are very significant. "Going with the flow" of the marketplace ensures that the technology and products needed are widely available at a competitive price. The demand of the marketplace ensures that the right functionality is provided, is well tested and proven in a variety of environments, and can be easily integrated into existing infrastructures. The realities of the marketplace are as follows: • Phenomenal demand for switched Fast and Gigabit Ethernet compared with LAN ATM, according to the worldwide forecast for the number of ports shipped (see Figure 3). • Decreasing price per port for switched Fast and Gigabit Ethernet compared with LAN ATM, according to the worldwide forecast for manufacturer price per port (see Figure 4). • Fast and Gigabit Ethernet are preferred campus networking technologies, as indicated by the expenditures and buying intentions of businesses (see Figure 5). These expenditures and buying intentions reflect the needs of businesses for a high bandwidth backbone that is cost-effective in meeting immediate or near-term application requirements, with sufficient functionality but without too much complexity, and that is easy to deploy and integrate with the existing network infrastructure. • No significant availability or deployment of ATM compared with the omnipresence of Ethernet to the desktops. This situation reflects the higher cost of ATM network interface cards, the lack of ATM Quality of Service (QoS) capability and QoS-exploiting applications in the end stations, and ATM’s complexity compared to Ethernet. • Greater availability of Ethernet skills compared with ATM skills in the labor market. This availability makes it much easier to hire network professionals when needed, and translates to lower labor cost. Skills availability is a rather important consideration, given the huge shortage of IT professionals, especially in networking. • Differences between WAN and LAN perspectives and design goals – In the WAN, the objective from the network service user’s perspective is to minimize the bandwidth required because recurring connection costs are based on usage. From the network service provider’s standpoint, it makes sense to transport the different types of traffic (data, voice, video, facsimile, etc.) over the same network technology. This is because new services to be provided over the same infrastructure can be rapidly deployed and optimized, and service revenues can be maximized. – In the LAN, bandwidth is practically "free" once installed, as there are no on-going usage costs. As long as sufficient bandwidth capacity is provisioned (or even over-provisioned) to meet the demand, there may not be a need for complex techniques to control bandwidth usage. If sufficient bandwidth exists to meet all










demand, then complex congestion and flow management schemes may not be needed at all. Other issues for the user assume greater importance including integration, manageability, flexibility (adds, moves, and changes), simplicity, scalability, and performance. Hence, the motivation and technology required for the LAN and WAN are quite different, depending on whether you are the user or the service provider. The result is that Gigabit Ethernet is increasingly being deployed as the LAN campus network technology of choice, whereas ATM is gaining greater acceptance in the WAN. • Slow convergence of the WAN towards a homogeneous network technology. Even as service providers are increasingly deploying ATM over the WAN, it will be several years before ATM will be available everywhere. Alternate services like Frame Relay, Packet-over-SONET/ SDH, DWDM, and leased lines will continue to be offered in the mean time because of the previous investments, geographical reach, and economic feasibility. These services will require transformation technology at the LAN-WAN edge, whether the campus is ATM or Gigabit Ethernet. ATM was intended as the single technology that will be used from the desktop, across the campus, and over the WAN. Given the slow convergence of WAN technologies, this will not be realized in many cases.










Diverse technologies continue to proliferate and compete to meet the same basic requirements for WAN connectivity; these include dark fiber, DWDM, IP Over ATM, IP Over SONET/SDH, IP Over DWDM (Optical), etc. Which of these technologies, and whether "cell or frame," or "cell and frame," or some other "packetization" technique will gain dominance, are issues still to be played out. It may be that no one single technology will be able to meet all user needs. In the meantime, users are seeking to minimize risks by preferring simpler and lower-cost Gigabit Ethernet to ATM.

Passport Campus Solution

In response to the market requirements and demand for Ethernet, Fast Ethernet and Gigabit Ethernet, Nortel Networks offers the Passport Campus Solution as the best-of-breed technology for campus access and backbone LANs.


The Passport Campus Solution (see Figure 6) is comprised of the Passport 8000 Enterprise Edge and Routing Switch families, the Passport 1000 Routing Switch family, the Passport 700 Server Switch family, and the BayStack 450 Stackable Switch. These switch products are all complemented by Optivity Policy Services and management software as a mechanism for providing powerful differentiated QoS policies. The following list highlights key features of the Passport 8000 Enterprise Switch, the winner of the Best Network Hardware award from the 1999 Annual Solutions Integrator Impact Awards, sponsored by IDG: • High port density, scalability and performance – Switch capacity of 50 Gbps, scalable to 256 Gbps – Aggregate throughput of 3 million packets per second – Less than 9 microseconds of latency – Up to 372 Ethernet 10/100BASE-T auto-sensing, auto-negotiating ports – Up to 160 Fast Ethernet 100BASE-FX ports – Up to 64 Gigabit Ethernet 1000BASE-SX or –LX ports – Wirespeed switching for Ethernet, Fast Ethernet and Gigabit Ethernet • High resiliency through Gigabit LinkSafe and Multi-Link Trunking • High availability through fully distributed switching and management architectures, redundant and loadsharing power supplies and cooling fans, and ability to hot-swap all modules • Rich functionality through support of: – Port- and protocol-based VLANs for broadcast containment, logical workgroups, and easy moves, adds and changes – IEEE 802.1Q VLAN tagging for carrying traffic from multiple VLANs over a single trunk – IEEE 802.1p traffic prioritization for key business applications




Figure 6: Passport Campus Solution with Optivity Policy Services. Data Data Voice Video Data Data WAN Passport 8000 Enterprise Switch Centillion 100 Multi-LAN Switch Passport 1000 Routing Switch BN Router redundant gateways BayStack 450 Ethernet Switch 10/100/Gigabit Ethernet MLT resiliency OSPF EMP Common Open Policy Services Differentiated Services IP Precedence/Type of Service IEEE 802.1Q VLAN Tag IEEE 802.1p User Priority Express Classification Optivity Policy Services & Management Server Farm 10/100 Ethernet MLT resiliency Gigabit Ethernet LinkSafe resiliency Passport 700 Server Switch server redundancy & load balancing System 390 Mainframe Server System 5000BH Multi-LAN Switch Data Voice Voice –


IGMP, broadcast and multicast rate limiting for efficient broadcast containment – Spanning Tree Protocol FastStart for faster network convergence and recovery – Remote Network Monitoring (RMON), port mirroring, and Remote Traffic Monitoring (RTM) for network management and problem determination. Users with investments in Nortel Networks Centillion* 50/100 and System 5000BH LAN-ATM Switches or alternate ATM-based LAN solutions already have a variety of mechanisms available to assist in the evolution toward a Gigabit Ethernet environment. Further migration to a Gigabit Ethernet environment will be enhanced with the availability of Gigabit Ethernet switch modules in routing switches, complemented by Gigabit Ethernet interfaces in existing ATM switches.




Information on the other award-winning members of the Passport Campus Solution is available on Nortel Networks web site: Gigabit Ethernet and ATM: A Business Perspective White Paper 15



Conclusion and Recommendation

This paper provides a comparative view of ATM and Gigabit Ethernet as campus backbone technologies from a businessoriented perspective. What is important in technology is functionality that meets today’s immediate needs at a price that is realistic. There is no point in paying for functionality and complexity that may or may not be needed, and may even be obsolete in the future. The rate of technology change and competitive pressures demand that the solution be available today, not later when another paradigm shift and another set of solutions introduce another set of completely new challenges. Gigabit Ethernet provides a pragmatic, viable and relatively inexpensive (and therefore, lower risk) campus backbone solution that meets today’s needs and integrates seamlessly with the omnipresence of connectionless, frame-based Ethernet and Fast Ethernet LANs. Enhanced by routing switch technology such as Nortel’s Passport 8000 Enterprise Switches and policy-enabled networking capabilities in Nortel’s Optivity Policy Services, Gigabit Ethernet provides enterprise businesses with the bandwidth, functionality, scalability and performance they need at a much lower cost than ATM. In contrast, ATM provides a campus backbone solution that has the disadvantages of undue complexity, unused functionality, and much higher cost of ownership in the enterprise LAN. For these reasons, Nortel Networks recommends Gigabit Ethernet as the technology of choice for most campus backbone LANs. ATM was, and continues to be, a good option where its unique and complex functionality can be exploited, in deployment, for example, in the metropolitan and wide area networks.

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