tli at cisco.com
Wed Aug 16 01:41:20 UTC 1995
> CIDR is a bandaid.
>If you seriously believe that, then you better present some other
>mechanism for scaling routing. We know of only one: hiearachical
it does not solve the problem of "router table growth" which perhaps
could more correctly be described as path growth on the gobal Internet.
CIDR, if correctly deployed, allows aggregation to happen. This
either slows or terminates the growth of the routing table.
The more "general" peering sites, the more total paths you have to
take, in addition to the problem of total peering sessions.
Correct. So if you want to establish a peering, you must allocate
memory accordingly. CIDR helps this again by reducing the growth in
the number of prefixes.
> The problem is
> translating from from BGP to forwarding tables installed in routers.
>Sorry, no. There are a number of problems. This isn't one.
Ok, I guess I was confused, I understood that route flapping which
causes a cisco router to need to be reloaded can be caused by
a flapping session, causing all of the forwarding tables/caches
to be flushed, causing the CPU load in a Cisco 7000 to reach 115%?
Have I been lied to?
Well, let's put it this way. It is impossible to get a cisco 7000
over 100%. There _isn't_ anything there. Yes, route flap is a
problem. Yes, a flapping peering can cause forwarding tables and
caches much indigestion. Yes, things can go to hell quickly. This is
why we've implemented damping.
> The other problem is the mesh nature of BGP which makes any BGP
> peering site, with full mesh peering, an N^2 problem.
>This is fixed.
How is this fixed?
We've implemented route reflectors, which allow you to partition your
IBGP mesh. So it's no longer N^2.
With N peers at a peering location you must have
each route must have N peering sessions, which looks like N^2 to me.
You only need a full mesh if you want information directly. If you
can get information from another peer at the interconnect (and note
that it does NOT imply that packets take an extra hop), then you don't
need a direct peering. Yes, I know that many people aren't willing to
do this. That's a political problem, not a technical one.
What was supposed to happen at the NAPs was that the Route Server
performs a centralized role and it hands routes to anyone.
>No one said that you had to buy the memory for your cisco from cisco.
No, but even certified memory from my PC/workstation vendor is cheaper
than Cisco certified memory.
Granted. If your third party sources are too expensive, well, I guess
you should use a PC instead. Seems to me this should be in the noise
for any serious operation.
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