RE: Designing an IX with non-PI space peers

  • To: "'Miguel A.L. Paraz'" <map at iphil dot net>, "'apops at apnic dot net'" <apops at apnic dot net>
  • Subject: RE: Designing an IX with non-PI space peers
  • From: Barry Raveendran Greene <bgreene at cisco dot com>
  • Date: Tue, 29 Apr 1997 08:26:25 +0800
  • Encoding: 115 TEXT
  • Sender:
      Good questions,
      One thing to remember is that BGP's router selection logic will choose the 
      most specific network. Here is an example at an domestic IXP:
      	- ISP A advertises a /19 to the IXP members.
      	- ISP B is a customer of ISP A, hence ISP B can point default to ISP A.
      	- ISP B get's their IPv4 addresses from ISP A. They get allocated a /22.
      	- ISP B advertises a /22 that is allocated from ISP A to the IXP.
      In this case another ISP at the IXP, say ISP C, who wishes to talk to any 
      IPv4 address within ISP B's /22 will send directly to ISP B (the most 
      specific route). When ISP C accepts routes from ISP A and ISP B via BGP, 
      then ISP C would receive both the /19 and the more specific /22. Traffic 
      bound for ISP B's /22 will go directly. All other traffic to ISP A's /19 
      will go directly there. If for some reason ISP B is disconnected from the 
      IXP, then ISP A's /19 will take over and traffic for ISP B will go through 
      ISP A's link to the IXP - hence ISP B is backed up.
      ISP B would be able to take in all the IXP routers and use them inside 
      their network to select whether the route is local. If it is not local 
      (i.e. not in the forward table), then the routers will choose 'default.' In 
      ISP B's case that is the direct connect to ISP A.
      + Yes, ISPs with non-PI space can connect to domestic IXPs.
      + ISPs with non-PI space can connect to multiple IXPs in a country, they 
      just need to design their interior routing to cope with their routing and 
      traffic engineering policies.
      + Private ASNs at an IXP should be avoided. ASN's are not scarce. In the 
      example above, ISP A can allocate an ASN received from APNIC to ISP B (ISP 
      A's customer). ISPs only need one ASN for their entire network.
      On the country IPv4 allocations ... I'll let APNIC answer that one (just to 
      keep conversation going). There as been talk in the past about national 
      NICs, continental aggregation, and other ideas.
      > From:    Miguel A.L. Paraz [SMTP:map at iphil dot net]
      > To:      apops at apnic dot net
      > Date:    97-04-28 23:05:59
      > Subject: Designing an IX with non-PI space peers
      > Hi,
      > Stirring up the quiet APOPS list a bit... :)
      > How would you design an IX where some of the participants do not have
      > provider independent space, but want to run BGP?  Would you consider
      > assigning private ASNs for these?  Looks like a waste if they procure
      > ASNs that won't be in use elsewhere.  On the other hand, static routing
      > doesn't scale, we're already having some inconvenience with the PHIX 
      > only has 5 peers at present.
      > The peers that do BGP with their upstream and the rest of the world would
      > have to take care to filter these others out.
      > What if a given ISP with non-PI space wants to peer with multiple IXs
      > within the country?  Then their private ASNs would have to be unique
      > across every IX where they're at.
      > This leads me to the idea of allocating "country" IP space that is only
      > routable/usable within a single country.  For example an organization 
      > that is interested only in Philippines connectivity would get space from
      > a registry that allocates from, say, 10/8, and makes sure these are 
      > People with true private IP needs can use 192.168/16.  Same would go
      > for the private ASN space so that people won't arbitrarily assign and
      > get dupes.
      > This is also a powerful incentive for other providers with IPLs to
      > interconnect locally since the 10/8 space is not visible from the 
      > Your thoughts?
      > Cheers,
      > --
      > miguel a.l. paraz  <map at iphil dot net> 
      > iphil communications, makati city, philippines 
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      > ------------------------------------------------------------------------
      Barry Raveendran Greene             |       ||        ||        |
      Senior Consultant                   |       ||        ||        |
      Consulting Engineering              |      ||||      ||||       |
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