Cisco s Small- to Medium-Sized Business Solutions Framework

Cisco’s Small- to Medium-Sized Business Solutions Framework

Cisco has recognized the changing needs of business and has been quick to respond to those needs with technology. If you were to go back in time 10 years, the LAN was a very different entity. Today there are technologies in the corporate LAN such as Fast Ethernet, switching, TCP/IP, voice, video, ATM, Layer 3 switching, and others. Cisco has assembled many independent technologies for switched internetworks into a scalable architecture called CiscoFusion. This allows network designers to use various features of Cisco’s IOS to solve a variety of problems.

Chapters 1 through 3 defined the differences between Layer 2 and Layer 3 of the OSI model. They talked about how Ethernet works and how to segment Ethernet (Layer 2) LANs. Those chapters also discussed IP and IPX (Layer 3) and their responsibilities. We will continue to build on these concepts throughout this book. The real question that arises is that with so many tools available, how does a network designer identify which technology is right to solve a particular problem? Cisco has responded to this need by creating the Small- to Medium-Sized Business Solutions Framework. This framework categorizes most customer problems into one of three categories:

• Media problems

• Protocol problems

• Transport problems

and proposes solutions to each of these.

This framework is typically represented as a triangle, as seen in Figure 4.1.

As mentioned, Cisco has categorized most customer design problems into one of these three categories. However, they did not stop there. Cisco created specific solutions for each category as well! This makes the Small- to Medium-Sized Business Solutions Framework a real tool that you can use throughout the design process. Let’s take a quick look at the problems that would appear in each category and at Cisco’s solutions for that category.

Figure 4.1: Cisco’s Small- to Medium-Sized Business Solutions Framework

Media Problems

Media problems are defined as problems relating to contention for use of the media itself. They are identified by high rates of utilization. For example, a Token Ring network at 80 percent utilization is experiencing a media problem. With Ethernet, you can monitor collision rate in addition to utilization to determine if media problems exist. We will discuss acceptable rates of utilization later in this chapter; this information will assist you in identifying media problems. When media problems are identified, the recommended solution is to use LAN switching (separate collision domains).

Protocol Problems

Protocol problems result when protocols designed for workgroup environments are used in significantly larger environments. Consider AppleTalk, for example. AppleTalk handles many tasks such as address assignment, name resolution, and broadcast-domain assignment automatically. However, to do all of this, AppleTalk generates considerable broadcast traffic. Or consider IPX, which was discussed in Chapter 3, “Network Protocols.” How did servers advertise their services? Their routes? How did workstations locate those services and routes? That’s right, they used broadcasts! Now, this is not a bad thing until you try to hook hundreds or even thousands of IPX nodes together on a single switched LAN. Isolating protocol problems involves counting the number of broadcasts per second or the number of workstations per broadcast domain. When protocol problems are identified, the recommended solution is to use routing (separate broadcast domains).

Transport Problems

Transport problems result when extreme demands are placed on the network. For example, many IS departments are being required to implement either video-conferencing solutions or video-streaming solutions or both! These types of applications require large amounts of bandwidth and have very little tolerance for delay, retransmissions, error rates, or anything other than perfect, prompt data delivery. Issues such as delay, available bandwidth, and application errors identify these problems. Using Fast Ethernet switching and, where appropriate, ATM, solves transport problems.