Fast Convergence: IS-IS performance tuning

IS-IS is the most selected protocol by service providers and large carriers all over the world; this is what makes the understanding  of this protocol important. We have been discussing fast convergence and high availability in the latest few posts and this post is not different, I am just going to give you an overview on the timers available for tuning in IS-IS. In later posts we will be dicussing the best practices in deploying this protocol and tuning for fast convergence.

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BGP performance tuning – Convergence, Stability, Scalability and NSF (Part 1)

It is a very critical matter for a network architect (the same goes for a network operator but with a different prospective) to understand the inside out of tuning the routing protocols performance, in order to be able to conduct an appealing and effective low level design for small to large scale networks. We have been discussing IGPs performance tuning in other posts, in this thread I’ll try to illustrate a simple description for all the tools/parameters affecting BGP performance (convergence, stability, scalability, and non-stop forwarding), with the defaults values and the recommended values for each.

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Fast Convergence: Partial SPF calculation

Shortest path first (SPF) is the algorithm used by IS-IS and OSPF routing protocols to calculate the topological information from the received link state updates. You can find more information about SPF calculation follow the link Dijkstra’s algorithm. Partial SPF is an efficient shortcut used by the routers to speed up the process of route calculations and hence achieve faster convergence. This feature is implemented by default mostly in all known SPF implementations.

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Fast convergence overview

For a network to converge, all routers in the network must collect and agree on all the topology information from each other. This information must be consistent, reflecting the current state of the network and free of routing loops or any other kinds of corruption. What is meant by fast convergence? when we use the word fast we are speaking about a relative thing specfied in time measuring units. The word fast here is describing the convergence time, which is the time required by all the routers in the network to flood and use the topology information. By fast convergence …

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Cisco and Nonstop Forwarding

Nonstop Forwarding is a feature of many features in the Cisco High Availability portfolio, we shall be covering most of it later. To check Cisco High Availability portfolio: http://www.cisco.com/en/US/products/ps6550/products_ios_technology_home.html Use Cisco Feature Navigator to find information about platform support and software image support: http://tools.cisco.com/ITDIT/CFN/jsp/index.jsp Cisco Nonstop Forwarding (NSF – AKA Graceful Restart) with Stateful Switchover (SSO – SSO is a prerequisite for NSF) is a Cisco innovation for platforms with dual route processors (Cisco 7304, 7500, ASR1000, 4500, 6500, 7600, 10000, 12000 and CRS), allowing a NSF Capable router which has experienced a hardware or software failure of an active …

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