From: Peter van Oene (pvo@usermail.com)
Date: Sat Apr 03 2004 - 23:13:24 GMT-3
>Do we even want to bring up the not-as-widely-used-in-production these
>days, but still occasionally useful for special applications and
>definitely for such things as Internet traffic research, the route
>server? A route server does no forwarding whatsoever. Typically, it's a
>UNIX box at an exchange point, running RSD software. What can be a heavy
>processing load for a router control plane can be pretty modest for a
>decent UNIX box with lots of memory.
I've built MPLS VPN networks with dedicated Route Reflectors doing purely
BGP reflection for VPNv4. In this case, these are routers and not route
servers per se, but they tend to do pretty much the same thing.
>Just as an aside, most exchange points had two route servers, running the
>same routing code on different brands of processors and often different
>UNIX variants (e.g., NetBSD vs. LINUX). The idea was to minimize the
>impact of RSD platform hardware or software bugs.
>
>Knowing about these, even in a historical context, helps understand what
>RRs do. RRs are primarily means of scaling your iBGP by reducing the
>number of peers per box inside (most likely) a POP. Best Current Practice
>tends to be meshing inside the POP, in many but not all cases.
>
>When router processors were less powerful, they could bog down at
>multilateral exchange points due to the number of eBGP peers. It was the
>TCP and BGP processing that hurt them, not bandwidth. Route Servers were
>an eBGP scalability technique, so if you had an exchange point with 20
>ISPs, each ISP peered BGP only with the primary and backup route server.
>The route server understood where the real routers were, so would set next
>hop for forwarding not to itself, but to the real other-ISP router
>connected to the common L2 fabric.
>
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