Loop in AS macro

Hi, I am new to this list and would like to ask a (maybe stupid) question to
the dicussion:

If we want to write a script to expand the AS MACRO, how can we avoid to go
into a loop if multiple AS-MACROs reference each other ?

Ping Lu
Cable & Wireless USA
Network Tools and Analysis Group
W: 703-292-2359
E: plu at cw.net

> -----Original Message-----
> From: Cengiz Alaettinoglu [mailto:cengiz at packetdesign.com]
> Sent: Wednesday, January 10, 2001 12:14 PM
> To: Shane Kerr
> Cc: Wilfried Woeber, UniVie/ACOnet; farrache at cc.in2p3.fr;
> db-wg at ripe.net; routing-wg at ripe.net; Henk.Uijterwaal at ripe.net
> Subject: RE: Loop in AS macro
> 
> 
> 
> Shane Kerr (shane at ripe.net) on January 10:
> > Gilles, Wilfried, and all,
> > 
> > This is not a bug, or even an inconsistency.  Consider the following
> > as-macro objects:
> > 
> >   as-macro: AS-X
> >   members:  AS-Y, AS123
> > 
> >   as-macro: AS-Y
> >   members:  AS-X, AS456, AS789
> > 
> > In this case, AS-X and AS-Y both expand to the same aut-num objects:
> > AS123, AS456, and AS789.  However, they may have different 
> maintainers,
> > contacts, descriptions, and so on.  In RPSL, many more 
> kinds of loops are
> > possible as well, in as-set, route-set, and filter-set objects.
> 
> RPSL defines semantics when loops exist. However, it does not promote
> them, or prohibit additional restrictions by the registry operators
> not to have loops.
> 
> > 
> > External software that deals with the set objects needs to do loop
> > detection in order to prevent infinite loops.  For as-set 
> objects (which
> > are as-macro objects in RIPE-181), this is fairly easy:  
> keep a list or
> > hash of the AS sets expanded, and don't expand them again.  
> For route-set
> > and filter-set objects it is not quite so easy.  If you 
> need help with
> > these, you can send me and e-mail and I can explain the 
> techniques that
> > I've used for these objects.
> > 
> > Shane Kerr <shane at ripe.net>
> > Database Software Engineer
> > RIPE NCC
> > +31 20 535 4427
> > 
> > p.s.  This is actually a feature, not an bug.  :)
> > 
> > p.p.s.  It has been argued (by me) that RPSL allows objects that are
> > logically impossible, but the RFC authors don't seem to think so!
> > 
> > On Wed, 10 Jan 2001, Wilfried Woeber, UniVie/ACOnet wrote:
> > 
> > >   Hi Gilles,
> > >   
> > >   I guess we wouldn't be able to check against those 
> accidents at the time
> > >   of a DB _update_...
> > >   
> > >   But checking the RR internal _data_ consistency could 
> maybe become part
> > >   of the RIS (or similar) project?
> > >   
> > >   Henk, any comments?
> > >   
> > >   An interesting aside: I guess similar problems could occur with
> > >   RPSL-based RRs?
> > >   
> > >   -WW
> > >  
> _________________________________:____________________________
> _________
> > >   Wilfried Woeber                 : e-mail: Woeber at CC.UniVie.ac.at
> > >   UniVie Computer Center - ACOnet : Tel: +43 1 4277 - 140 33
> > >   Universitaetsstrasse 7          : Fax: +43 1 4277 - 9 140
> > >   A-1010 Vienna, Austria, Europe  : RIPE-DB: WW144, PGP 
> keyID 0xF0ACB369
> > >  
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~:~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> ~~~~~~~~~
> > > 
> > > To: staff at ip.tele.dk, peering at tli.de, ip-oper at tli.de, 
> admin-c at tli.de
> > > CC: farrache at cc.in2p3.fr, db-wg at ripe.net, routing-wg at ripe.net
> > > Subject: Loop in AS macro
> > > Date: Wed, 10 Jan 2001 10:28:15 +0100
> > > From: Gilles Farrache <farrache at cc.in2p3.fr>
> > > 
> > > Dear database managers,
> > > 
> > > I notice a loop in the followings AS-MACRO, in fact  
> AS-TELEDANMARKINTERNATIONAL
> > > is calling AS-TLI which is calling AS-TELEDK which is 
> calling AS-TELEDANMARKINTERNATIONAL.
> > > (and all that make that our automatic filter generation 
> tool fails)
> > > 
> > > Could you correct those macro and will the Ripe database 
> management provide any 
> > > control on that kind of loop ?
> > > 
> > > Gilles 
> > > 
> > > as-macro:    AS-TELEDANMARKINTERNATIONAL
> > > descr:       Tele Danmark customers outside Denmark
> > > as-list:     AS1902 AS12461
> > > as-list:     AS8881 AS-KOMTEL
> > > as-list:     AS13194 AS-BITE
> > > as-list:     AS6709
> > > as-list:     AS8650 AS-TLI
> > > as-list:     AS8542
> > > as-list:     AS12294 AS-TSUA AS6807 AS8349 AS12788 
> AS12837 AS12872 AS13249 AS15386 AS15497 AS15929 AS16007
> > > as-list:     AS12546
> > > as-list:     AS15389
> > > tech-c:      AS5071-RIPE
> > > admin-c:     AS5071-RIPE
> > > notify:      staff at ip.tele.dk
> > > notify:      peering at tli.de
> > > mnt-by:      AS3292-MNT
> > > changed:     jesper at skriver.dk 20001103
> > > changed:     toba at tdk.dk 20001117
> > > changed:     tee at tdk.dk 20001123
> > > changed:     jesper at skriver.dk 20001228
> > > changed:     jesper at skriver.dk 20010109
> > > source:      RIPE
> > > 
> > > as-macro:    AS-TLI
> > > descr:       Talkline GmbH, Internet Division
> > > descr:       List of ASes according to Talkline Internet (AS8650)
> > > descr:       and customers
> > > as-list:     AS5605
> > > as-list:     AS6783
> > > as-list:     AS8650
> > > as-list:     AS8881
> > > as-list:     AS12461
> > > as-list:     AS12546
> > > as-list:     AS-TELEDK
> > > as-list:     AS-GLOBAL
> > > tech-c:      TLIP1-RIPE
> > > admin-c:     TLIP1-RIPE
> > > notify:      peering at tli.de
> > > mnt-by:      TALKLINE-MNT
> > > changed:     thomas at tli.de 19990923
> > > changed:     thomas at tli.de 19991020
> > > changed:     thomas at tli.de 19991025
> > > changed:     thomas at tli.de 20001023
> > > changed:     thomas at tli.de 20001025
> > > source:      RIPE
> > > 
> > > as-macro:    AS-TELEDK
> > > descr:       Tele Danmark and Tele Danmark customers
> > > as-list:     AS-TELEDANMARKDANISH
> > > as-list:     AS-TELEDANMARKINTERNATIONAL
> > > as-list:     AS-BELBONEMEMBERS
> > > as-list:     AS-GLOBAL
> > > tech-c:      AS5071-RIPE
> > > admin-c:     AS5071-RIPE
> > > notify:      staff at ip.tele.dk
> > > notify:      peering at tli.de
> > > mnt-by:      AS3292-MNT
> > > changed:     jesper at skriver.dk 19990922
> > > changed:     jesper at skriver.dk 19991019
> > > changed:     jesper at skriver.dk 19991025
> > > changed:     jesper at skriver.dk 19991210
> > > changed:     toba at tdk.dk 20000903
> > > source:      RIPE
> > > 
> --------------------------------------------------------------
> ------------------
> > > 
> > 
> > 
> 
> 
> Cengiz
> 
> -- 
> Cengiz Alaettinoglu           Packet Design Inc.
> 
>