One alternative to CIDR... ASAP

Tim Bass bass at
Sun Aug 13 20:32:18 UTC 1995


People keep sending me e-mail asking for my ideas on alternatives to
renumbering and CIDR.  Here is a very rough strawman idea just
posted to the CIDRD-WG.  There are similar variations on this
ASN routing paradigm that also could be considered:



PS:  I'm off to the Azores in Portugal Monday for three weeks, so
     hopefully I can find net access to see how much of a flame-fest
     my mbox is enjoying.....



Autonomous System Aggregation Protocol (ASAP)

Too simple, by a simple minded person.... :-)

1) Modify IP code in routers to route with ASN numbers between

2) Modify core routers to add ASN numbers to IP packets by; 
   i.)   Temporarily using TOS or similar field(s) in IP header;
   ii.)  Add proper hooks in next version of IP;
   iii.) Some better idea.

3) Develop details of new routing algorithm to route, filter,
   load balance, multi-home using ASN tags;

4) Modify core routers to add ASN tags to IP packets that do
   not have ASN tags assigned by originating host (for 
   backwards compatability with version of TCP/IP that cannot
   add their ASN numbers to IP headers (or a better idea);

5) Modify core routers to transfer routing from the ASAP protocol
   to the appropriate IGP if-and-only-if ASN of destination matches
   the current ASN;

6) Create simple UDP based algorithm (similar to DNS) that manages
   a distibuted database that maps IP addresses to ASN numbers.
   For example:  

   When sending a packet, the kernal checks its cache for a map between
   the IP address and ASN number.  If it existing is the cache (get a hit)
   it adds the ASN destination number to the IP header..... if not
   the router or host sends a UDP packet to a distributed database that
   maintains the mappings..  (these could be local, remote, but distributed
   and caching each other ... in a similar, but more efficient manner than 
   DNS  (after all how often do IP networks change their home ASN)
   (instead of ARP.... its ASNRP...... ;-)

7) Create another database of SUPERNETTED ASN numbers for IP service providers
   that aggregate current ASN numbers into some meaningful structure and
   provide distribued SUPER-ASN to SUPER-ASN routing.

8) More ideas to develop and refine....


1) IP address space allocation is simplifed and renumbering not necessary;
2) ASN routing reduces the size of the routing tables ;
3) SUPER-ASN routing further reduces the size of ASAP routing tables;
4) Routers can add ASN tags to IP packets until users migrate to new IP
5) More.... but I'm packing for a trip...


1) Must create new ASAP protocol and SUPER-ASAP protocol;
2) Must create distributed ASN-NETWORK database;
3) IP code must be modified and upgraded;
4) Non-cached initial packets will route slower mapping 
   destination ASN to destination IP address.
5) Also more disadvantages.....

Just a start.... needs work.... but living in a plane is a real
drain.. :-)


| Tim Bass                           | #include<campfire.h>                | 
| Principal Network Systems Engineer |       for(beer=100;beer>1;beer++){  |
| The Silk Road Group, Ltd.          |           take_one_down();          |
|                                    |           pass_it_around();         |
|           |       }                             |
|                                    |  back_to_work(); /*never reached */ | 

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