The original BGP specification and implementation dates back to the early 90s. And as we've already started to notice in some of the discussions so far, there are one or two little issues that we might need to pay attention to given the size and scale of the internet and the different network operator backbones today. Some of these issues include how do we scale the iBGP mesh beyond a few peers? If you remember from the iBGP discussion iBGP must be fully meshed. Fine for a small network of a few routers, but how do we scale this for a network with say a thousand routers? The early BGP implementations had no mechanism for implementing new policy without really shutting down the BGP session and bringing it up all over again. Again, in the early 90s when the internet was still marginally used mostly with the network operations of research and education networks and a few commercial operations, it probably didn't really matter. But today the internet is critical infrastructure, globally, so implementation of new policy by bringing down a BGP session and restoring it, is not really an option. Another thing that the earlier network operators found was how to keep the networks stable, scaleable, as well as simple to manage and operate. We're going to look at a few of the scaling techniques that had been introduced into BGP in the mid and late 90s. We'll look at some of them now, we'll look at some of them during the BGP best practices presentations also. But certainly, some of the current best practice scaling techniques would be route refresh and of course the BGP route reflector. Cisco and other vendors have introduced the concept of groups. Cisco's peer-group is well known. There's also a scaling technique called route flap damping which was introduced in the mid 90s to address a particular issue that the internal operators of the day were facing. And we'll also have a look at Cisco's version of route refresh, which again was introduced to deal with a particular issue prior to route refresh being standardized.
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