Network Availability Protocols

Network availability protocols, which include link integrity protocols, link bundling protocols, loop detection protocols, first-hop redundancy protocols (FHRP), and routing protocols, increase the resiliency of devices connected within a network. Network resiliency relates to how the overall design implements redundant links and topologies and how the control-plane protocols are optimally configured to operate within that design. The use of physical redundancy is a critical part of ensuring the availability of the overall network. If a network device fails, having a path means the overall network can continue to operate. The control-plane capabilities of the network provide the capability to manage the way in which the physical redundancy is leveraged, the network load balances traffic, the network converges, and the network is operated.

You can apply the following basic principles to network availability technologies:

• Wherever possible, leverage the capability of the device hardware to provide the primary detection and recovery mechanism for network failures. This ensures both a faster and a more deterministic failure recovery.
• Implement a defense-in-depth approach to failure detection and recovery mechanisms. Multiple protocols, operating on different network layers, can complement each other in detecting and reacting to network failures.
• Ensure that the design is self-stabilizing. Use a combination of control-plane modularization to ensure that any failures are isolated in their impact and that the control plane prevents any flooding or thrashing conditions from arising.

These principles are intended to be a complementary part of the overall structured modular design approach to the network architecture and primarily serve to reenforce good resilient network design practices.

Note

A complete discussion of all network availability technologies and best practices could easily fill an entire volume. Therefore, this discussion introduces and provides only an overview of the network availability technologies most relevant to TelePresence enterprise network deployments.

The protocols discussed in this section can be subdivided between Layer 2 (L2) and Layer 3 (L3) network availability protocols.