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| 1.2 |  | Key Characteristics of Scalable Internetworks |
| 1.2.1 |  | Five characteristics of a scalable network |

Although every large internetwork has unique features, all scalable networks have essential attributes in common. A scalable network has five key characteristics:

- Reliable and available – A responsive network should provide Quality of Service (QoS) for various applications and protocols without making responses at the desktop worse.
- Responsive – A responsive network should provide Quality of Service (QoS) for various applications and protocols without making responses at the desktop worse. The internetwork must be capable of responding to latency issues common for Systems Network Architecture (SNA) traffic. However, the internetwork must still route desktop traffic without compromising QoS.
- Efficient – Large internetworks must optimize the use of resources, especially bandwidth. It is possible to increase data throughput without adding hardware or buying more WAN services. To do this, reduce unnecessary broadcasts, service location requests, and routing updates.
- Adaptable – An adaptable network can accommodate different protocols, applications, and hardware technologies.
- Accessible but secure – An accessible network allows for connections using dedicated, dialup, and switched services while maintaining network integrity.

The Cisco IOS offers a rich set of features that support network scalability. The remainder of this module discusses IOS features that support these five characteristics of a scalable network.