Why Upgrade Your Ethernet LAN?...1. Fast Ethernet Hub or Ethernet Switch?...5. Step-by-Step Upgrade Planning LANS for Small Businesses...

Transcription

1 Contents Why Upgrade Your Ethernet LAN? Fast Ethernet Hub or Ethernet Switch? Step-by-Step Upgrade Planning LANS for Small Businesses LANS for Medium-Sized Businesses Case Studies Choosing Cisco as Your Networking Partner Conclusion Planning Worksheet Glossary i

2 About This Guide The performance of your local area network (LAN) can directly affect your company s business success. In small and medium businesses alike, employees need quick, reliable access to applications and data to perform their jobs. A LAN that delivered adequate performance when installed, however, may now be straining. Factors contributing to the need for an upgrade are more users, more powerful PCs and servers, more demanding applications, and the growing role of the intranet. Sluggish performance impedes productivity and may prevent you from deploying intranet or other networked applications that can improve your competitiveness. Improving LAN Performance: A Step-by-Step Planning Guide is a reference for small and medium businesses that want to ensure they re receiving maximum benefit from their LANs. The guide explains how to determine if you need an upgrade, describes the two primary options Ethernet switch or Fast Ethernet hub and provides stepby-step planning instructions. To facilitate your upgrade planning, the guide also provides case studies and a worksheet. After you have reviewed this guide, if you have additional questions, do not hesitate to contact Cisco Systems for the answers. In the U.S. or Canada, call NETS (6387) Monday through Friday, 8:00am to 7:00pm Eastern Standard Time. For Fax-on-Demand service and product information, call or check our web site at ii iii

3 Why Upgrade Your Ethernet LAN? Upgrading your Ethernet LAN improves employee productivity in the short term, and can position your company for competitive advantage in the long term. A high-bandwidth LAN accommodates today s demanding PCs and workstations, makes existing applications run faster, enables you to deploy powerful intranet business applications, and supports company growth. You can tell when your Ethernet LAN is ready for an upgrade because users are dissatisfied with network performance, network statistics suggest that performance degradation is imminent, or you are planning to deploy powerful new intranet-based business applications for which your present network is inadequate. This section of the guide explains the benefits of upgrading your Ethernet LAN and describes signs that indicate that you need an upgrade. Benefits of Upgrading Accommodate New, More Demanding PCs and Workstations Today s personal computer interface (PCI) computers can move large files over 90 Mbps, easily overloading the actual 8- to 9-Mbps throughput capacity of a 10BaseT Ethernet network. The speed and bandwidth of these desktop computers, the size of popular Internet files, and the magnitude of attachments sent via are increasing continually. Your network bandwidth must grow in concert to keep up with these advances. Make Existing Applications Run Faster The chief reason to upgrade your LAN is to gain higher performance from existing client/server applications, such as groupware, job automation, computer aided design/computer aided modeling (CAD/CAM), desktop publishing, and multimedia. A CAD/CAM application task that takes five minutes to execute on a LAN with a 10BaseT hub might execute 400-percent faster, in only one minute, on a LAN with a Fast Ethernet 10/100 hub or 1

4 10-Mbps Ethernet 10/100 switch. The time savings translate to higher employee productivity. Adequate bandwidth also ensures that you can add new applications as needed without concern for bandwidth limitations to respond to changing business conditions. Deploy Powerful Intranet Applications Intranet business applications promise a more self-sufficient and productive workforce major advantages in today s competitive business environment. Your company may plan to take advantage of Internet technology for critical internal business applications, such as employee self-service applications for training and human resources, enterprise resource planning (ERP), imaging, videoconferencing, and electronic whiteboards for collaboration. High-bandwidth intranet applications impose radically different demands on your network infrastructure. For example, more network traffic travels over the backbone instead of remaining within workgroups, and larger file sizes and higher volumes increase network congestion. To gain the advantages of an intranet lower costs, rapid application deployment, and the ability to use any client platform you may need more bandwidth than you presently have. Switched Ethernet and Fast Ethernet offer a cost-effective solution. Accommodate Company Growth As more employees access your intranet and you extend your network to suppliers, customers, and partners LAN performance may suffer. By installing Ethernet switches, you can relieve network congestion in several ways. For example, you can logically locate shared resources, such as file servers and printers, with the workgroups that use them most, reducing traffic on other portions of the network. You can also dedicate network bandwidth to workgroups and individual users who need it most. Signs that an Ethernet LAN Upgrade Is Due Until recently, LAN congestion was rarely a problem. LANs could move more data per second than computers could output. Now, advances in computing and communications technology have shifted the bottleneck from the computer to the LAN. The output from one device can occupy the full channel capacity of a typical LAN. When several such devices share the channel, congestion often results. To determine if your LAN is congested, consider the following factors. Higher Network Utilization Measure network utilization, sometimes called channel utilization, which is the percentage of time that a communications path is busy carrying data. The higher the traffic load, the higher the network utilization. You can measure network utilization by using network monitoring equipment, such as protocol analyzers or Remote Monitoring (RMON) devices. Certain hubs and switches provide network utilization statistics on their visual displays. For many common environments, including office automation LANs with dozens of stations, the LAN is approaching an excessive load when network utilization reaches the following levels: 20 percent averaged over an eight-hour work day 30 percent averaged over the worst hour of the day 50 percent averaged over the worst 15 minutes of the day These figures are only guidelines. Some application environments may operate well under heavier loads or fail at lighter levels. Network performance will still vary based upon the number of stations on the LAN, application behavior, and traffic patterns. Note that for very short-term periods (seconds, or even tens of seconds), network utilization may be nearly 100 percent without causing any problems. Temporary high utilization might occur during a large file transfer between a pair of high-performance stations on an otherwise quiet network. Increased Collision Counts If multiple stations on a shared network begin sending Ethernet packets at the same time because they all sense a quiet network, a collision between packets results. When a collision occurs, each participant waits a random amount of time and tries to send its packet again. An increase in the number of packet collisions on an Ethernet LAN can indicate rising LAN congestion. Collisions do not always indicate a congestion problem, however. The Ethernet protocol uses collisions to quickly redistribute the traffic load over the available time, maximizing channel utilization and application throughput. In fact, collisions 2 3

5 consume a very small percentage of available channel capacity, even under a moderate to heavy traffic load. If user performance and application throughput are acceptable, you can pay little attention to collision statistics, and regard them as only a minor factor in network health. Application Performance Degradation When the LAN is congested, applications do not perform as well as they do otherwise. File transfers take longer, and terminal sessions are sluggish. In extreme circumstances, sessions may time out and disconnect and applications or operating systems may actually crash, requiring a system restart. A decrease in application performance can be an indication of LAN congestion. However, it can also result from other factors, such as CPU, memory, disk performance, and number of users. Increased Network Delay All LANs have an upper limit on the amount of data they can carry. When temporarily overloaded, the LAN takes longer to distribute the load. Therefore, when the load is heavy, the average delay, also known as service time, increases. This delay makes the network seem slower to users. To directly measure service time, you need special driver software. It is easier to assess congestion using other, more observable criteria, such as the data from network analyzers. User Dissatisfaction The ultimate sign of LAN congestion is user dissatisfaction. If users are happy, then the network is functioning at acceptable levels. Similarly, if users are dissatisfied with the LAN performance, this fact overrides all statistics indicating that performance is within acceptable ranges. Note that user dissatisfaction with network performance does not always indicate a congestion problem. The source of the problem might instead be applications, servers, protocol stacks, or WAN access devices not just the underlying LAN hardware and software. Fast Ethernet Hub or Ethernet Switch? If you presently have a 10-Mbps Ethernet hub and your network is exhibiting signs of congestion, either a Fast Ethernet hub or an Ethernet switch can immediately and dramatically improve network performance. This section explains the difference between a switch and a hub and suggests the preferred solution in different business environments. The Difference between a Hub and a Switch Advantages and Disadvantages of Hubs A hub is an inexpensive way to connect users. It is a simple device that forwards received packets out to all ports, even though the destination of the packet is connected to only one port. An Ethernet hub, also called a 10BaseT hub, provides a total of 10 Mbps of bandwidth, which all users share. If one person on the network is downloading a very large multimedia file, for example, little or no bandwidth is available for other users. These users will experience the network as being very slow. If your network connects 20 or more employees, an Ethernet hub rarely provides enough bandwidth to deploy intranet-based business applications without long waits. A Fast Ethernet hub, also called a 100BaseT hub, makes ten times more bandwidth available for users to share. A load of 50 percent utilization in a network with an Ethernet hub would correspond to a load of only 5 percent in a network with a Fast Ethernet hub. The primary advantages of Fast Ethernet hubs for improving LAN performance are their low cost and ease of installation and use. You simply disconnect your existing hub, connect your new one, and immediately experience the performance improvement. The only requirements are network interface cards (NICs) that support Fast Ethernet and Category 5 UTP cabling for all Fast Ethernet devices. No software configuration or hardware settings are needed. As listed in Table 1, the primary disadvantage of Fast Ethernet hubs is limited growth potential. Every workstation, server, or other hub connected to a main hub is 4 5

6 considered to be within the same network segment, commonly called a collision domain. For example, if you connect four 12-port hubs, all 48 attached devices are in the same collision domain, and all of them share the same bandwidth. If you add more hubs as your network grows, available bandwidth is shared among more devices, and performance degradation will result. If you install a Fast Ethernet hub now and later outgrow it, you can upgrade to a 10/100-Mbps Ethernet switch, and redeploy the Fast Ethernet hub elsewhere in the organization. Table 1: Advantages and Disadvantages of Fast Ethernet Hubs as Replacements for Ethernet Hubs Some switches, such as those from Cisco, provide 10/100- Mbps ports, which can operate at either speed. The switch automatically senses the speed of the attached device and configures the port for the proper speed. This feature, called autosensing, simplifies deployment in mixed Ethernet and Fast Ethernet environments. Switches also offer intelligent management options, such as allowing the network manager to create multiple segments reducing traffic on other segments by creating virtual LANs (VLANs). More information about intelligent options for switches appears in the section LANS for Small Businesses. Advantages Total bandwidth remains fixed; as network traffic grows, perfor- mance suffers Improves performance, especially for bursty traffic and large file transfers Enables optimum performance of PCI computers Offers ease of use: Fast Ethernet hubs require no hardware or software settings; just plug them in Leverages your knowledge of Ethernet and investment in management tools and applications Disadvantages The network manager cannot manage network load for example, by segmenting the network into multiple collision domains or restricting certain types of traffic to certain ports Does not reduce collisions Requires Category 5 UTP cabling for each 100BaseTX connection Advantages and Disadvantages of Ethernet Switches Table 2 summarizes the advantages and disadvantages of Ethernet switches as replacements for Ethernet hubs. Table 2: Advantages and Disadvantages of Ethernet Switches as Replacements for Ethernet Hubs Advantages Improves performance by offering each individual or workgroup 10- or 100-Mbps of bandwidth; Fast Ethernet ports provided by the switch allow high-speed server and backbone connections, eliminating bottlenecks Enables scalable bandwidth: the more ports on the switch, the more bandwidth is available; aggregate bandwidth equal the number of ports times 20-Mbps (full duplex), divided by two Disadvantages Slightly more expensive than hubs Requires Category 5 UTP cabling for each 100BaseTX connection 6 A switch is more sophisticated than a hub, giving you more options for network management, as well as greater scalability. Unlike a hub, a switch forwards packets only to one port: the one connected to the destination of the packet. It does this by keeping a table of each destination address and its port. When the switch receives a packet, it reads the destination address and then establishes a temporary connection between the source port and the destination port. After the packet is sent, the connection is terminated. A switch provides higher total throughput than a hub because it can support multiple simultaneous conversations. For example, in an eight-port Ethernet switch, four pairs might be communicating simultaneously, for 40-Mbps throughput, or four times more bandwidth than a 10-Mbps Ethernet hub. The more ports on a switch, the more aggregate bandwidth. Allows network manager to dedicate 10- or 100-Mbps connections to users who need them most Uses existing 10-Mbps Ethernet cabling, network interface cards, hubs, and software, leveraging your organization s Ethernet investment Reduces collisions: user groups on a single port will produce collisions, but considerably fewer than if all switch users were still on a single shared 10-Mbps Ethernet Improves security by forwarding unicast packets only to the port associated with the destination address of the packet; other users don t see the traffic 7

7 Is a Switch or Fast Ethernet Hub Best for Your Organization? To decide if you would benefit most from a Fast Ethernet hub, a 10/100-Mbps Ethernet switch, or a combination, consider your applications, the type of network traffic, and the cost of upgrading your cabling and PCs. Types of Applications In general, if you have one server, Fast Ethernet hubs are faster that 10-Mbps Ethernet switches. However, Ethernet switches offer certain other advantages, such as increased manageability and guaranteed bandwidth to individual desktops or resources. The following examples describe types of applications and suggest whether Ethernet switches or Fast Ethernet hubs are better. Example 1: Type of traffic: Sustained traffic with smaller files Example: Database transaction application Preferred upgrade: Ethernet switch In this environment, congestion is caused by a constant stream of small files between the clients and the server. The most cost-effective solution is to divide the single collision domain into multiple collision domains, using switched Ethernet. In this way, you deliver 10 Mbps through each port and take advantage of a 100-Mbps uplink for high-speed server access. You can continue to leverage your existing 10-Mbps NICs. Example 2: Type of traffic: Bursty, with large, multimegabyte file transfers and power users running high-bandwidth applications Example: Software compiling, or CAD/CAM Preferred upgrade: Fast Ethernet hub or 10/100-Mbps Ethernet switch Large files take a long time to arrive when moving at 10 Mbps. Therefore, for applications involving large files, Fast Ethernet hubs deliver a substantial performance boost. Even if the files are relatively small, but are transmitted in sporadic bursts, Fast Ethernet improves performance. For sustained, large-file traffic, such as network backups, Fast Ethernet hubs can increase the throughput and speed of the transactions to complete the job more quickly, reducing the impact on the backbone and minimizing network slowing. If your organization has power users running high-bandwidth applications, consider a 10/100-Mbps switch. For a small premium, all power users can have their own, dedicated 100-Mbps segments. Example 3: Type of traffic: Streamed multimedia applications Example: Emerging applications such as IP/TV Technology Preferred upgrade: Fast Ethernet if you have one server; switched Ethernet if you have multiple servers If you have one server, the high overall bandwidth of Fast Ethernet hubs improves performance the most. However, if you have multiple servers, switched Ethernet can provide additional relief through its ability to deliver aggregate bandwidth in excess of 100 Mbps, and to restrict multicast traffic to the segments that need to receive it. Types of Packets Ethernet traffic is made up of three different types of packets: unicast, multicast, and broadcast. How much of each type of traffic you have on your network can be important in determining whether you need a switch or a hub which features you might need. Unicast packets, which are sent by users, are addressed to a single destination. Most traffic on an Ethernet LAN is typically unicast packets. Multicast packets are designed to reach a select group of client destinations. Many new multimedia applications use multicast packets so that they can send only one packet or stream of packets to reach multiple users. This scenario conserves not only network bandwidth, but also CPU utilization for the multimedia server: it sends only one stream rather than one stream per user. Broadcast packets are addressed to reach all nodes within a single collision domain. These types of packets are typically sent by servers or routers to advertise their existence and to keep alive their connections with end nodes. Broadcast packets can produce a large amount of traffic. For example, a NetWare-based server sends a hello packet that is broadcast every 60 seconds. Routers, by default, also broadcast their routing tables every 60 seconds. Figure 1 illustrates the types of data transmission discussed. 8 9

8 High-Performance LAN Solutions Shared Ethernet Figure 1: Types of Data Transmission 10 Switched Ethernet 100 Shared Fast Ethernet Hubs do not filter traffic; rather, they forward traffic received on any port to all ports. If much of your traffic is broadcast or multicast packets, consider installing a switch so that you can restrict packets to certain segments, reducing traffic on other segments. Switches can transmit traffic in three ways: Selectively forwarding packets, based on type Switches can differentiate between unicast traffic and other groupcast (multicast and broadcast) packets. Switches from some vendors, such as Cisco, can even distinguish between multicast and broadcast packets, completely eliminating unnecessary traffic. Selectively forwarding multicasts only to those users who want to view a specific multimedia session Supporting VLANs VLANs are logical, as opposed to physical, groupings of users. By setting up VLANs, you can build smaller collision domains on a single switch. 10 For example, you could create one VLAN for UNIX users and the UNIX server, and another VLAN for NetWare clients and the NetWare server. With two separate VLANs, neither user group would see the broadcast traffic from the other group s server. Consider Existing Adapters When you decide how to upgrade, consider the costs of upgrading your existing network infrastructure. Whether you install Ethernet switches or Fast Ethernet hubs, it is highly recommended that you install 10/100-Mbps adapters in any new PC or server, because the incremental cost for these adapters is marginal. You must install Fast Ethernet adapters in all PCs and servers attached to a Fast Ethernet hub. Fast Ethernet adapters also let you take advantage of the 30 to 90+ Mbps throughput and power of PCI computers. Cabling Switched Ethernet runs on the common two-pair Category 3 cabling installed in most buildings, as well as Category 4 and Category 5 unshielded twisted pair (UTP) cabling. But 100BaseTX, the most commonly used Fast Ethernet implementation, requires Category 5 cabling. The cost of installing replacement cabling for existing users may encourage you to you opt for switched Ethernet, or you may decide it is a good time to upgrade the cabling. Either way, Category 5 UTP is the standard copper cabling used for all high-speed network technologies, and all new UTP cable installations should be Category 5. See Figure 2 on next page. To summarize, both Ethernet switches and Fast Ethernet hubs dramatically increase network performance. Each is suited for different network throughput and traffic needs, user demands, and equipment cost considerations

9 Infrastructure Considerations Cabling UTP Category 3 UTP Category 5 PCs ISA PCI, EISA Adapters Existing 10 Mbps New 10/100 Mbps Switched Ethernet Switched Ethernet or Fast Ethernet Switched Ethernet Switched Ethernet or Fast Ethernet Switched Ethernet Switched Ethernet or Fast Ethernet If you have decided to upgrade to a switch, you can purchase a 10-Mbps switch or a 10/100-Mbps switch. In the former, all ports deliver 10 Mbps of bandwidth. In the latter, the switch automatically configures the port for the speed of the attached device: 10 or 100 Mbps. Typically, companies take advantage of the 100-Mbps connection for high-volume shared resources, such as file servers. In organizations that work with very large files, such as prepress service bureaus and software developers, certain employees can benefit from their own 100-Mbps connection. Fast Ethernet switches are often used to create a 100-Mbps backbone supporting a mix of high-bandwidth users and devices on Ethernet switches and Fast Ethernet hubs. Figure 2: Considerations when Choosing a High-Performance Technology Combining Ethernet Switches and Fast Ethernet Hubs Implementing Ethernet switches and Fast Ethernet hubs is not an either/or proposition. You can combine Ethernet switches and Fast Ethernet hubs to optimize overall performance with the least expense. For example, casual users working with office automation and word processing applications can remain on Ethernet hubs attached to a switch. Power users can gain the performance of a dedicated 10-Mbps port on a switch. And users with even higher throughput needs, as well as all new users, can be connected to Fast Ethernet hubs. Fast Ethernet hubs can also provide high-speed access to a group of servers and create a backbone that interconnects switches. By combining the technologies, you can leverage your existing Ethernet hubs and adapters through Ethernet switches, and deliver the speed that high-end users, servers, and backbones need through Fast Ethernet hubs. If your Fast Ethernet hub becomes inadequate for backbone traffic or server connections, you can upgrade by adding a Fast Ethernet switch, such as the Cisco Catalyst 2900 XL. A Fast Ethernet switch can connect to the 100-Mbps uplinks in Ethernet switches, to Fast Ethernet hubs, or directly to your servers

10 Step-by-Step Upgrade Planning This section provides step-by-step instructions for planning an upgrade. The first part is intended for small and growing companies with 20 to 100 employees, that currently use an Ethernet hub. The second part addresses the concerns of companies with up to 500 employees. These companies may presently have an Ethernet hub, 10-Mbps Ethernet switch, or a combination. This section will help you decide whether you need a Fast Ethernet hub, 10/100-Mbps Ethernet switch, or a combination. It will also help you select switch features that will be useful for your network environment

11 LANS for Small Businesses Read this section if you presently connect up to 100 employees to your LAN via an Ethernet hub. If you are also transmitting multimedia traffic, you may also find it helpful to read the next section, LANS for Medium-sized Businesses. Step 1: Decide whether You Need a Fast Ethernet Hub or a Switch Review the discussion in the previous section to decide whether a Fast Ethernet hub or an Ethernet switch best meets your performance requirements and budget needs. In general: Either a hub or a switch improves performance if current network utilization is high. Switched Ethernet provides more total bandwidth [(Number of ports 2) x 20 Mbps] and lets you create separate collision domains. (The 20-Mbps bandwidth per port assumes full-duplex operation.) Fast Ethernet hubs are less expensive than Fast Ethernet switches. Step 2: Locate Resources Efficiently If you are upgrading to a Fast Ethernet hub, you can skip this section. When you install a switch, each segment is its own collision domain. Therefore, to minimize unnecessary traffic, you should place workstations in the same segment as the servers they access (see Figure 4). The devices in a segment do not need to be physically collocated; if the switch has a VLAN feature, you can create logical segments that span different floors or buildings. For example, you might create one segment each for finance, graphics design, and engineering. Creating logical segments not only reduces network traffic, it also increases security by restricting confidential traffic to one segment of the network. All Cisco switches support VLANs

12 If you are upgrading to an Ethernet or Fast Ethernet switch, you can optimize LAN performance by placing workstations on the same logical network as the servers they access most often. This setup reduces the amount of traffic that must travel over a network backbone, which is the network segment that connects switches. 10BaseT Hub Floor 2 Floor 1 Ethernet Switch Ethernet Switch Ethernet Switch 10/100 Switch 10/100 Switch 10BaseT Hub Servers Servers MultiMedia Server Step 4: Check Wiring and Network Interface Cards Fast Ethernet requires the use of Category 5 cabling. If you want to connect the switch to devices more than 200 meters away for example, between buildings you will need a fiber connection. Step 5: Install Your New 100BaseFX Hub or Switch After you receive your new Fast Ethernet hub or Ethernet switch, select a time for installation when a 30-minute disruption in network service will not affect the business for example, an evening or weekend. Disconnect the cables from your Ethernet hub and connect them to the Fast Ethernet hub or to the switch. If you have purchased a 10/100-Mbps Ethernet switch, connect the 100-Mbps ports to popular resources, such as file servers, or to individual power users who use more than 10 Mbps of bandwidth. The switch or hub begins operating immediately. No further installation is necessary. If you installed a switch and want to create VLANs (Step 2), follow the instructions in your switch manual. 10 Mbps 100 Mbps Figure 4: Locate Workstations on Same Segment as Server Step 3: Plan to use Existing Hubs Elsewhere in the Network If you are upgrading to a switch, you can continue to take advantage of your existing 10-Mbps hubs. Plan to connect each hub to a 10-Mbps segment on the switch, and to connect servers to 100-Mbps segments. This migration plan protects your investments in 10-Mbps hubs while improving performance

13 LANS for Medium-sized Businesses Read this section if you are upgrading from a 10-Mbps Ethernet switch or your LAN supports 100 or more employees. Step 1: Forecast Bandwidth Requirements Measure traffic on your existing network and project your bandwidth requirements for the next two years. Keep in mind that applications are consuming more and more bandwidth, and that intranet-based business applications will increase network load. When you arrive at an estimate, it s a good rule of thumb to double or triple the number; this is the amount of total bandwidth you should purchase. To calculate the bandwidth capacity that a switch can deliver (because each port is communicating with another port), multiply the number of ports by the bandwidth of the ports (10 or 100 Mbps in half-duplex operation, or 20 or 200 Mbps in full-duplex operation), and then divide by two. For example, a switch with twelve full-duplex 10-Mbps ports and two 100-Mbps ports delivers 320 Mbps of total bandwidth: [(12 x 20Mbps) 2) + (2 x 200Mbps) 2] = 320 Mbps Step 2: Segment Your Network If you are installing a Fast Ethernet hub, you can skip this step. When you install a switch, each segment is its own collision domain. Therefore, to minimize unnecessary traffic, you should place workstations in the same segment as the servers they access. The devices in a segment do not need to be physically collocated; if the switch has a VLAN feature, you can create logical segments that span different floors or buildings. For example, you might create one segment each for finance, graphics design, and engineering. Creating logical segments not only reduces network traffic, it also increases security by restricting confidential traffic to one segment of the network

14 When you decide how to segment your network, a reasonable rule of thumb is that 80 percent of the traffic on a given network should be local (destined for a target in the same workgroup), and not more than 20 percent of the network traffic should require transmission across a backbone. If your backbone is congested, this congestion may indicate that your traffic patterns do not conform to the 80/20 rule. If the congestion problem persists after you segment the network, you might consider replicating resources for example, adding servers so that users can access them locally without having to cross the backbone. Step 3: Decide Whether You Need a Backbone A backbone is a high-bandwidth connection between segments; the backbone connects the core business servers. You need a backbone if numerous users access the servers. To support the high volume on a backbone, you need a Fast Ethernet or ATM connection. Be sure your switches support a high-speed uplink. The Cisco Catalyst 2900 XL series switches, for example, provide a high-speed backbone connection. Step 4: Plan for Remote Intranet and Extranet Connections If you want to give intranet access to your remote offices, or enable suppliers, partners, or customers to access your extranet, you will need a router. Choose a switch that supports the features of your router, such as IP multicasts, security, and management interface. Step 5: Check Wiring and Network Interface Cards Fast Ethernet requires the use of Category 5 cabling. If you want to connect the switch to devices more than 200 meters away for example, between buildings you will need a fiber connection. Step 6: Install Your New 100BaseFX Switches Installing switches requires simply disconnecting the old hubs or switches and connecting the new one. You can create VLANs, specify packet filtering, and select other management options using the switch software. You can generally redeploy Ethernet and Fast Ethernet switches elsewhere in the network, where traffic loads are not too high. Case Studies Case Study A: Law Firm Situation Fewer than 50 users, all connected to Ethernet hubs Two file servers All users share a single 10-Mbps Ethernet LAN Additional users will be added over the next 12 months Traffic Type Sustained loads with small files Before Shared 10BaseT Workgroups Figure 6: Shared 10-Mbps Ethernet LAN Cause of Network Congestion Servers 10 Mbps Too many users sharing 10-Mbps of bandwidth Constant stream of small files traveling over network Increasingly large file transfers Client/server applications have all clients heavily accessing two servers 22 23

15 24 Symptoms of Congestion Slow network response times Server bottlenecks High collision rates Reduced productivity User dissatisfaction and requests for computer upgrades Solution Install a 10-Mbps Ethernet switch to aggregate the Ethernet hub workgroups and provide 100-Mbps connections to servers. Install Fast Ethernet adapter cards in servers to support 100-Mbps connections. After Figure 7: Ethernet LAN Considerations Ethernet Switch Servers 10 Mbps 100BaseT Uplinks Because the congestion is being caused by a constant stream of small files, and the firm already has standard two-pair Category 3 cabling and Ethernet adapters installed for every user, Ethernet switches are the most cost-effective improvement. Fast Ethernet is not as costeffective for existing users, because it would require replacement of cabling and existing adapters, and a substantial performance increase is not needed here. Instead, as shown in Figure 7, a single Ethernet hub with a small number of users is connected to each Ethernet switch port. Fast Ethernet adapters and short runs of Category 5 cabling are installed to provide 100-Mbps connections to the servers, eliminating bottlenecks with minimal expenditure. All new users will be equipped with 10/100-Mbps adapters at very small additional cost and connected to the available 10-Mbps ports of the switches. When additional ports are needed in the future, Fast Ethernet hubs or 10/100 switches can be added. Case Study B: Same Law Firm, One Year Later Situation Two new file servers A new Web server for CD-ROM library access 50 existing users on a 10-Mbps Ethernet hubs segmented by a 10-Mbps Ethernet switch. Exceed 50-percent utilization on an average of 15+ minutes a day 50 new users on PCI desktop computers to be added Traffic Type Sustained loads with small files growing to high-volume loads with bandwidth-intense peaks of 70 percent Cause of Network Congestion Casual user load increased through large file transfers and sophisticated applications Increasing World Wide Web and CD-ROM library access Increasing intranet application development Symptoms of network congestion: Slow response times High collision rates Network degradation Reduced productivity User dissatisfaction 25

16 Before Servers After Web Server Servers Web Server Server Server Ethernet Switch 10/100 Mbps Ethernet Switch 100BaseT Users Dedicated 10BaseT Users Ethernet Switches Shared 10BaseT Workgroups Dedicated 10BaseT Users Shared 10BaseT Workgroups 10 Mbps 100 Mbps Figure 8: 10-Mbps Switched Ethernet LAN with Fast Ethernet Uplinks to Servers Solution 10 Mbps 100 Mbps Move users from shared workgroups to their own dedicated switch ports a process called microsegmentation and add switches as necessary. Attach new users and power users to Fast Ethernet switch ports. Observe the 80/20 rule for locating resources: Place workstations on the same logical network as the servers they access most often. Figure 9: Switched Ethernet Workgroups with High-Speed Access to Localized Servers Considerations Because new users are equipped with 10/100-Mbps adapters, the firm is able to cost-effectively move smaller file users from shared Ethernet to switched Ethernet and move the power users and servers to switched Fast Ethernet hubs or 10/100 hubs. The 10/100 Fast Ethernet switch also serve as a backbone for the switches. Localizing servers results in a significant reduction of traffic on the backbone. Case Study C: New Advertising Agency Situation A newer installation of 200 nodes and Category 5 UTP cabling All users are equipped with 10/100-Mbps adapters and connected to Ethernet switches Fast Ethernet backbone connects workgroups to servers on two floors Emerging video, Internet, intranet, and animation applications 26 27

17 Traffic Type Increasing load of large bursty graphics and multimedia application file transfers with bandwidth intense peaks of 85 percent 10BaseT Hub Floor 2 Floor 1 Ethernet Switch Ethernet Switch 10/100 Switch 10/100 Switch Servers Occasional network-wide crash Some users working at night to meet missed deadlines Network backup takes too long User dissatisfaction Solution Microsegment all users on the switches and move bandwidth-intensive users to Fast Ethernet hub connections. Observe the 80/20 rule for locating resources: Place workstations on the same logical network as the servers they access most often. Contain multicast traffic with a switch solution. Introduce a Fast Ethernet switch as a high-speed backbone for 10-Mbps switches, Fast Ethernet hubs, and servers. Ethernet Switch 10BaseT Hub Servers MultiMedia Server After Ethernet Switch Servers 10 Mbps 100 Mbps Floor 2 10/100 Switch Figure 10: Fast Ethernet Backbone with Switched Ethernet to the Desktop Server Floor 1 100BaseT Hubs Cause of Network Congestion High-bandwidth multimedia and graphics processing on the same network as word processing and project management applications Server Ethernet Switch 10/100 Switch MultiMedia Server Increasing power user population Increasing network utilization 10 Mbps 100 Mbps Effects Slow response times Figure 11: Fast Ethernet and Switched Ethernet to the Desktop on a Switched Fast Ethernet Backbone Server bottlenecks Applications time out 28 29

18 Considerations Leverage investment in equipment by attaching users to existing switches and Fast Ethernet hubs. The power users are equipped with Fast Ethernet hub connections, whereas the more casual users are cost-effectively supported through switched 10-Mbps connections. The graphics and multimedia application users require higher speeds to transmit large files and are best kept separate from the other users. The new Fast Ethernet switch with multicast management features will effectively contain multicasts and facilitate all the 100-Mbps traffic from installed Fast Ethernet hubs and Ethernet switches. Choosing Cisco as Your Networking Partner Cisco provides a rich combination of LAN solutions, services, and support especially geared to the needs of small and medium businesses. Plug and play operation, for example, delivers fast results with nominal management overhead, and scalability ensures your LAN can grow in step with your business. For Networks with 20 to 100 Users Ethernet hub: Cisco1500 Series Micro Hub Fast Ethernet hub: Cisco 1528 Micro Hub 10/100 For Networks with 101 to 500 Users Ethernet desktop switches: Catalyst 1900/2820 Series Fast Ethernet desktop or backbone switch: Catalyst 2900XL Fast Ethernet switch: Cisco 1548 Chassis-based switch: Catalyst 5000 Micro Switch 10/100 Fast Ethernet hub: FastHub 124, 10/100, 216, 316 Table 4: Cisco solutions designed especially for the needs of small and medium businesses. This section explains the unique benefits of Cisco hubs and switches for improving your Ethernet LAN performance

19 Benefits of Cisco Fast Ethernet Hubs Cisco Fast Ethernet hubs are a low-cost alternative to Ethernet switches. They provide the following benefits: Easy installation Installation and configuration takes minutes, and does not require technical knowledge. Cisco hubs provide automatic configuration and self-test on startup. Easy operation Cisco hubs automatically disconnect and reconnect if a problem arises. You can connect to any hub or switch without using a crossover cable. Easy expansion Two FastHubs can be interconnected, supporting up to 46 Ethernet or Fast Ethernet ports in a single collision domain. Easy management Some models support management via SNMP using the CiscoWorks Windows system, support local or remote management and monitoring via the console port. Single vendor solution and support When combined with a Cisco router, hubs offer a complete, simple LAN/WAN solution. Cost-effectiveness Some Cisco hubs supports Ethernet and Fast Ethernet users simultaneously, providing a costeffective way to migrate to Fast Ethernet. Benefits of Cisco Catalyst Ethernet Switches Cisco Catalyst Ethernet and Fast Ethernet switches provide the following benefits: Scalability Optional high-speed uplinks deliver maximum performance where it s needed most to servers, the network backbone, and other switches. Standard, inexpensive high-speed uplinks allow up to 800-Mbps bandwidth between switches, and to routers and individual servers, while enhancing fault tolerance. Optimized throughput enables all ports in a fully populated switch to operate at wire-speed. It also supports applications that require zero packet loss. Broadcast control prevents faulty end stations from degrading overall system performance with broadcaststorms. Multicast/multimedia control reduces traffic on the network by routing multimedia traffic to targeted end stations. Reliability Resilient links provide fast recovery from network failures. Power redundancy for up to four units ensures maximum network uptime. Security Console access control restricts unauthorized users from accessing the switch and altering its configuration. User access control allows network administrators to grant and restrict user access to various areas on the network. Mobility and management Dynamic adds, moves, and changes simplify network administration and support changing workgroups. Rapid and easy switch deployment reduces administrative burden. Consistent management interface across product line leverages existing skills and reduces training requirements. Wide Range of LAN Solutions for Small and Medium Businesses Cisco, the worldwide leader in networking for the Internet, provides a range of LAN solutions that deliver superior network performance as you connect your desktops to the Internet and corporate intranets. In particular, the Cisco Network Office (CNO) stack, is a flexible suite of compatible products designed for remote branch offices and small and growing businesses. CNO provides exceptional ease of installation, use, manageability, and scalability for connecting users and resources, and for supporting high-volume or high-bandwidth intranet and Internet applications

20 Industry-Leading Support Whether you purchase a hub or a switch, Cisco provides outstanding service and support to ensure that your network remains up. Support ranges from help desk assistance to proactive, onsite consultation. All support contracts include: Cisco Connection Online Cisco s industry-leading online support information service, available 24 hours a day, 7 days a week. Eighty-five percent of Cisco customers obtain the answers to their questions on line. Cisco Technical Assistance Center Cisco fields a global network of more than 500 technical experts the largest technical assistance team in the industry. Proactive software updates With any Cisco desktop switch, you receive automatic Cisco IOS software upgrades, extending the useful life of your switch. Advance hardware replacement Rapid access to replacement equipment reduces the need to carry hardware and spare modules in inventory reducing your inventory costs. Conclusion With new, more powerful applications and PCs, adequate bandwidth has become essential to business success. Only with sufficient bandwidth can employees remain productive and exploit low-cost intranet technologies to deploy critical business applications. Cisco offers two general solutions to cost-effectively improve Ethernet LAN performance. Fast Ethernet hubs increase shared bandwidth tenfold, greatly alleviating network congestion in smaller environments. Cisco s FastHub and Micro Hubs are extremely easy to install and require nominal administration, so small businesses and workgroups can realize benefits immediately. Cisco s Ethernet and Fast Ethernet switches increase aggregate bandwidth dramatically by enabling multiple simultaneous conversations, whereas hubs allow only one. In addition, they enable companies to segment their networks into multiple, smaller collision domains, further improving performance. Cisco Catalyst switches with Fast Ethernet uplink ports enable companies to create highbandwidth backbones connecting segments to core business servers. Cisco switches offer unique competitive advantages, including unsurpassed scalability, reliability, security, and mobility and management. Current Cisco router customers receive the performance they have come to expect, at the local-area network level. If you have questions, would like to receive more information, or want a referral to a Cisco reseller, contact Cisco Systems: In the U.S. or Canada, call NETS (6387) Monday through Friday, 8:00 a.m. to 7:00 p.m. Eastern time. For fax-on-demand service and product information, call Or visit our Web site at

21 Planning Worksheet Refer to this sheet when selecting a Cisco switch or Fast Ethernet hub in order to ensure that you have everything you need to install your new switch or hub. Selecting a Model 1. Number of Ports Needed Type of Device Ethernet Fast Ethernet Workstations Peripherals Servers TOTAL 2. Switch Management Options Needed Virtual LAN (VLAN) support Ability to selectively forward packets, based on type Ability to selectively forward multicast packets (Cisco Group Management Protocol, or CGMP) Infrastructure Checklist 1. Distances Number of hops, or jumps between one segment and another If you re using Ethernet hubs, no more than four hops can be on any one collision domain. If you re installing Fast Ethernet hubs, no more than two hops can be on any one collision domain. 2. Cabling and Adapters To run Fast Ethernet, you must have Category 5 cabling. To run Fast Ethernet, you must have 100-Mbps NICs. To connect a switch to a device more than 200 meters away, you must have a fiber connection

22 Glossary 100BaseFX 100BaseT 100BaseTX Broadcast Broadcast Storm IEEE 802.3u standard for 100-Mbps Fast Ethernet using two strands of multimode fiber-optic cable. See 100BaseT, Fast Ethernet. IEEE 802.3u standard for 100-Mbps Fast Ethernet specification. 100BaseT offers a speed increase of ten times that of the 10BaseT Ethernet specification, while preserving such qualities as frame format, Media Access Control (MAC) mechanisms, and maximum transmission unit (MTU). See Fast Ethernet. IEEE 802.3u standard for 100-Mbps Fast Ethernet using two pairs of either Category 5 UTP or shielded twisted-pair (STP) wiring. The first pair of wires is used to receive data; the second is used to transmit. See 100BaseT, Fast Ethernet. Data packet that will be sent to all nodes on a network. An undesirable network event in which many broadcasts are sent simultaneously across all network segments. A broadcast storm uses substantial network bandwidth and typically causes network timeouts. Compare with unicast and multicast

23 CGMP Class II Fast Ethernet Forwarding Full Duplex Cisco Group Management Protocol. Used by Cisco switches to recognize multicast traffic reported via Internet Group Management Protocol (IGMP) by IP hosts and routers. Switches can use this information to conserve LAN bandwidth by restricting traffic in a multimedia environment. See IGMP. IEEE 802.3u repeater specification that permits two repeaters, or repeater stacks, to be cascaded (connected using 100BaseT ports), creating one collision domain. Conversely, Class I repeaters require a switch, bridge, or router to connect separately located repeaters or repeater stacks. Based on an extension to the IEEE 802.3u specification, Fast Ethernet offers a speed increase ten times that of the 10BaseT Ethernet specification, while preserving such qualities as frame format, MAC mechanisms, and MTU. Theoretical throughput is the total available 100 Mbps. See 100BaseT, 100BaseTX, 100BaseFX. Process of sending a frame toward its ultimate destination by way of an internetworking device. Capability for simultaneous data transmission between a sending station and a receiving station. Fullduplex 100BaseT provides up to 200 Mbps of throughput (100 Mbps in each direction). It also permits longer distances when used with fiber. At full duplex, a 100BaseFX link can reach 2 km. IGMP Internet Group Management Protocol. Used by IP hosts to report their multicast group memberships to an adjacent multicast router. Routers can use this information to conserve LAN bandwidth by restricting traffic in a multimedia environment. See CGMP and multicast. Multicast Repeater (hub) Router Switch Switched Ethernet Unicast VLAN Data packet copied by the network and sent to a specific subset of network addresses. Compare with broadcast and unicast. Network device that indiscriminately forwards traffic from one segment to another. Network device that uses one or more metrics to determine the optimal path along which network traffic should be forwarded. Network device that filters and forwards frames based on the destination address of each frame. Segments Ethernet into channels, allowing multiple simultaneous conversations to occur and virtually eliminating collisions. Theoretical throughput is the sum of the bandwidth of each pair of conversations that may occur simultaneously. Data packet sent to a single network destination. Compare with multicast and broadcast. Virtual LAN. Group of devices on a LAN that are configured (using management software) to communicate as if they were attached to the same wire, even though they may be located on a number of different LAN segments. VLANs are based on logical, instead of physical, connections