Re: RFC1863 to historic? [Re: [Idr] Last Call on draft-ietf-idr-rfc2796bis-00.txt (fwd)]

Note: I haven't been doing this stuff anywhere near as long as some
of the members of this forum.  This said, here is my opinion based
on some second and third hand stories.

On Tue, May 04, 2004 at 02:13:40PM -0400, Howard C. Berkowitz wrote:
> In my experience, newbies better understand all of the scalability 
> methods if one adds the idea of the "classic" or "historic" RsD-style 
> route server as an _e_BGP scalability technique. SO to come back to 
> Jeff's comment, a route server replaces/reduces full eBGP mesh at 
> exchange points.

In the beginning of the Internet, route servers served a useful role
in reducing the routing table traffic load on the hosts at an exchange
point to levels within the capacity available to the boxes at the time.

Apparently, the window of time where this was necessary was 
"reasonably small".  

When routers were deployed that could handle the number of eBGP views
at a typical exchange point, the route servers were only useful 
(for route reduction purposes) for protecting smaller boxes.  I think
it is likely today that most exchange points will typically find boxes
deployed that are capable of handling the relevant full or partial
mesh that the business model that XP operates under can use.

The route servers often caused more problems than they were worth in
environments where reachability to the route server didn't imply
reachability to the actual router advertising the routes.  

In the era when boxes are thought to be capable of handling a pretty
serious routing load, the route server model excels at one thing - 
proxying policy.  "I ask for X set of destinations, I only want to
send you Y destinations".  Configure it in a database, run RtConfig
and let it rip.

Nothing stops a bgp speaker from doing similar things with RtConfig
at their edges.  However, when you start doing it for a reasonable
number of peers, your policy tends to get huge.  Some boxes deal
with huge policy better than others.

If you wish to contemplate how route servers scale, remember that
a route server is much the same case as a 2547 PE router.

-- 
Jeff Haas 
NextHop Technologies

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