Content

| 7.1 |  | Introduction to Cisco AVVID |
| 7.1.4 |  | High availability |

High Availability optimizes design and tools to ensure end-to-end availability for services, clients, and session. Tools include reliable, fault-tolerant network devices to automatically identify and overcome failures and resilient network technologies such as Hot Standby Router Protocol (HSRP) to bring resilience to the critical junction between hosts and backbone links, and Simple Server Redundancy Protocol (SSRP) that communicates between router and ATM switch groups to detect device failures and initiate automatic reroutes within one second of failover time.

Determining how resilient a network is to change or disruption is major concern for network managers. This assessment of network availability is critical. It is essential that every network deployment emphasizes availability as the very first consideration in a baseline network design.

Availability must be viewed from the users perspective. To the user, the network is down regardless of whether an application fails, a router dies, or a piece of fiber is cut. Key availability issues to address include:

- Hardware Redundancy This is often the first level of redundancy in the network. Cisco offers, in its modular products for example, options for redundant supervisor engines and dual in-line power supplies. This often provides the first backstop against a network failure.
- Protocol Resiliency Good design practices dictate how and when to use protocol redundancy, including load-sharing, convergence speed, and path redundancy handling. Contrary to popular belief, if some redundancy is good, more redundancy is not necessarily better.
- Network Capacity Design Good design practices include capacity planning. How much traffic can a connection handle in the worst case? Ascertaining that a link can handle double the traffic when a redundant link fails must be considered. Capacity planning must be included during the network design phase to ensure the smooth integration of new technologies (such as video conferencing).
- Management Includes the LAN Management Solution for advanced management of the award-winning Catalyst multilayer switches; the Routed WAN Management Solution for monitoring, traffic management, and access control to administer the routed infrastructure of multiservice networks; the Service Management Solution for managing and monitoring service-level agreements; and the VPN/ Security Management Solution for optimizing VPN performance and security administration.
- Multicasting Provides bandwidth-conserving technology that reduces traffic by simultaneously delivering a single stream of information to thousands of corporate recipients and homes. Multicasting enables distribution of video conferencing, corporate communications, distance learning, distribution of software, and other applications. Multicast packets are replicated in the network by Cisco routers enabled with Protocol Independent Multicast (PIM) and other supporting multicast protocols resulting in the most efficient delivery of data to multiple receivers.