Re: CIDR Aggregation Tool

[Enke Chen <enke () mci net>]

Avi, 
Did you not see the aggregation report by Tony Bates on cidrd 
posted periodically for the last couple of years?  It lists 
aggregation gains for each origin AS, rather than the BGP 
neighbor in your numbers.  IMHO, numbers based on origin AS 
is much more useful. 

If you need to invent wheels, let us at least invent better 
wheels :-)

-- Enke
 

Date:    Mon, 27 Nov 1995 01:34:55 EST
To:      cidrd () iepg org
From:    Tony Bates <Tony.Bates () mci net>
Subject: In the spirit...
 
Here's the latest top-30. Looks like UUNET-CANADA dropped a fair bit
from last time.
 
                --Tony.
 
ASnum    NetsNow NetsCIDR  NetGain  % Gain   Description
 
AS2493      1047      576      471   45.0%   i*internet
AS174       1493     1053      440   29.5%   Performance Systems International
AS544        740      524      216   29.2%   The DataNet IP Service
AS3848       425      236      189   44.5%   WORLDLINX
AS568        759      572      187   24.6%   Milnet FIXes--144(W)/145(E)
AS4628       240       54      186   77.5%   APNIC-AS-BLOCK
AS1324       465      287      178   38.3%   ANS New York City - DNSS 35
AS97         506      338      168   33.2%   JvNCnet
AS3602       285      175      110   38.6%   Intergrated Network Services Inc.
AS4230       195       93      102   52.3%   EMBRATEL-BR
AS1717       649      556       93   14.3%   RENATER
[....]

> Date:    Sun, 26 Nov 1995 23:00:49 -0500
> From:    Avi Freedman <freedman () netaxs com>
> To:      big-internet () munnari OZ AU, cidrd () iepg org, nanog () merit edu
> CC:      freedman () netaxs com

> Well, after observing the debates about What To Do About The Routing Table
> Size, I decided to work on some informal tools to examine the current
> routing table space for possible aggregations.
>
> Right now, the raw data is the routing table from the Net Access MAE-East
> router.
>
> It only searches for aggregates /15 < x < /25 right now - ignoring some
> fairly obvious aggregation-suggestions in the /8 < x < /16 range.
>
> The results are up at http://routes.netaxs.com and the some of the caveats 
> are listed on the web page, but are:
>
> 1) When the Net Access MAE-East router has multiple identical routes that 
>    point to the same next-hop (192.41.177.x), the system only uses the one 
>    first listed in the cisco 'sho ip bgp summ' output - even though that's
>    not always the 'best' route.
>
> 2) When an AS advertises both an aggregate and a specific, the specific 
>    is 'dropped' by the aggregator. If the input is:
>    {205.89.10.128/17, 205.89.10.130}, the output will be:
>    {205.89.10.128/17} (205.89.10.130 will be dropped).
>
> 3) The source of data is the Net Access MAE-East router routing table, 
>    and we don't peer with all parties at MAE-East directly - thus, it's 
>    possible that the system catches aggregations that are impossible
>    because they're announced to a 3rd party via different paths - but
>    an informal look around doesn't appear to indicate that.
>
> 4) The system goes by next-hop rather than by AS-Path.  There seems to
>    be a good correlation, but ...
>
> Also, the final disclaimer: I've examined the results and they *look* 
> reasonable.  But I haven't written tester-tools to attempt to verify
> by another algorithm that the results are correct.
>
> Here's the table at the end of the web page:
>
>                            Before   After 
>                            Run      Agg. Run
> 192.41.177.110 ibm             81     68
> 192.41.177.115 digex           98     98
> 192.41.177.120 eu.net         949    775
> 192.41.177.125 nsn.nasa       126    112
> 192.41.177.140 ans           2146   1425
> 192.41.177.145 agis           539    304
> 192.41.177.150 uscyber          2      2
> 192.41.177.160 interpath        2      2
> 192.41.177.170 net99          309    246
> 192.41.177.180 mci              2      2
> 192.41.177.181 mci           8963   6828
> 192.41.177.190 pipex          367    308
> 192.41.177.210 netcom         370    348
> 192.41.177.235 psi              1      1
> 192.41.177.240 icp           4499   3712
> 192.41.177.241 sprintlink    6429   4694
> 192.41.177.245 psi           1491   1098
> 192.41.177.249 alternet      3971   3148
> 192.41.177.251 es.net          96     88
> 192.41.177.252 es.net         122    101
> 192.41.177.6   suranet        470    445
> 192.41.177.70  internex         1      1
> 192.41.177.80  ios             10      8
> 192.41.177.85  cais           184    158
> 192.41.177.86  hlc            354    243
> 192.41.177.89  energis          2      2
> 192.41.177.95  delphi           3      3
>
> A final note:  We're open to {Additional static sources of route tables at
> MAE-East; Additional static sources of route tables at {MAE-West, Pennsauken,
> or the PacBell NAP}; and dynamic (i.e. the vty password so we can run
> a sho ip bgp summ every so often) sources at any of the MAEs or NAPs.
>
> If we get good feedback, we may automate this to run overnight and keep
> a history.
>
> Avi Freedman
> freedman () netaxs com