Latest estimate: Internet Routing table / Memory needed

I haven't really seen anything on this in a while, in terms of an up to
date figure. Here is what our internet border router reports (with full
from UUnet and Digex, and a few more (^3561$) directly from CW):

58909 network entries (116785/119858 paths) using 10448216 bytes of memory
15451 BGP path attribute entries using 1946036 bytes of memory
0 BGP route-map cache entries using 0 bytes of memory
2 BGP filter-list cache entries using 32 bytes of memory

Looks like I'm burning about 12 megs. Lets say I had the whole table (~
58/59k networks today), but only one provider. Rather than turning half
our Internet feed off to see, could someone tell me how this would affect
the above 'sh ip bgp summ' result from my router ?? I.e. how much memory
would be burnt then ??

Thanks in advance...

hi Brandon,

  i'm not sure I can a whole lot of value here, but that doesn't
  seem to stop most people posting to, so I'll add

  you are correct in your assertion that additional views (where
  view is defined as a table learned from a unique provider) will
  increase the amount of memory required to hold the bgp table.

  but this is only one component of size.

  Without thinking too much, the following is a list of variables
  which can/will influence bgp memory requirements:

    . number of routes leared from each provider
  . number of unique routes in the routers' view of the internet
  . number of as-paths in the backbone table
  . number of peering sessions, esp. as a function of
     the peer's routes
       - ie - a small peer offers less than a large peer
    - transit provider BGP feeds should be similar in
      size and distribution, though not exactly the
      same, as one's perception of the internet varies
      based upon the vantage point

  there are neat tricks that bgp programmers do, like storing
  as paths in patricia/radix trees, and referencing the
  as-path from the routes array, etc..

  additionally, on a feature/vendor basis, the following will
  also impact memory requirements:

    . soft reconfiguration in and out
  . policy instantiations
  . dampening history and policy

  from an fgc perspective, we see gross memory utilization similar
  to yours.

  from a mae-west router w/ approximately 50 peers, we see, on a
  cisco 75xx:

61341 network entries and 181983 paths using 11650851 bytes of memory
20707 BGP path attribute entries using 2587116 bytes of memory
91295 BGP route-map cache entries using 1460720 bytes of memory
5670 BGP filter-list cache entries using 90720 bytes of memory
Dampening enabled. 380 history paths, 25 dampened paths
10553 received paths for inbound soft reconfiguration
BGP activity 153132/91791 prefixes, 2990192/2808209 paths
1762451 prefixes revised.

  hope this perspective helps.


Thus spake Brandon Applegate (
on or about Fri, Mar 26, 1999 at 03:54:02PM -0500: