BGP table size

[Maria Matejka]

Basically, we eat about 64 bytes per prefix, 64 bytes per route and
(112 + variable) deduplicated route attributes.

Therefore in the most basic case, you can have 6.4MB for 100k prefices
+ 6.4MB for 100k routes (one per prefix) + 112 bytes when all the 
prefices have the same nexthop and nothing else, in total ~13 MB.

If you get a full 4k packet of BGP attributes for each route, the latest 
value is not 112 bytes but ~4k*100k ~ 400MB in (probably) worst case.

Looking into our testbed having full IPv4 BGP feed loaded (760k 
prefices), BIRD eats 89MB for route table entries and 48MB for the 
deduplicated attributes, in total 137 MB.

After normalization to 100k routes, you get 137 MB / 7.6 ~ 18 MB.

Maria

On 8/12/19 3:56 PM, Emerson Barea wrote:
> Sorry, I think that I didn't explaim well in my first message.
> 
> I want to know if exist any information that tell me how much RAM memory 
> 100k BGP prefix uses in Bird, for example.
> 
> I know Cisco uses between 28MB and 71MB of memory by 100k prefix [1]. 
> So, I want to know if Bird has some information like this.
> 
> Thank you
> 
> Emerson
> 
> [1] 
> hhttps://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol-bgp/12512-41.html 
> <http://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol-bgp/12512-41.html>
> 
> Em seg, 12 de ago de 2019 às 09:33, Maria Matejka <jan.matejka at nic.cz 
> <mailto:jan.matejka at nic.cz>> escreveu:
> 
>     Hello!
>     BIRD has in concept no limit on number of routes and number of prefices.
>     It should scale quite well. If not, please let us know.
>     Maria
> 
>     On 8/12/19 2:15 PM, Emerson Barea wrote:
>      > Hi. Anyone knows if Bird documentation has any information about BGP
>      > table size vs. number of routes?
>      > Thanks.
>      > Emerson
>