brescia@PARK-STREET.BBN.COM (Mike Brescia) (05/23/88)
> NETINFO:X25.DOC ... covers the DDN's class A IP address The DDN (Milnet, Arpanet) x.25 service is supplied by packet switch nodes (PSNs') which have the internal structure reflected in the address given to each host attachment point. Embedded in the 14 digit address is 3 digits of PSN and 2 digits of host port connection on that PSN. Since there is this known mapping, the number of digits can be encoded uniquely in the 24 bits of 'host' of a class A IP address. > It seems like gateways everywhere support this but where's the algorithm??? The general case of any arbitrary X.25 address for a network in any country cannot be handled by a single algorithm, so the implementations that I know of have a separate data base which is typed in to the individual gateway when it is configured, or perhaps down-loaded from a file provided with the gateway. Maybe you want to specify an address resolution protocol (ARP) service where the information is stored in a single central host, instead of the ethernet style of ARP where the information for each host is stored in the individual hosts. You then only have to configure one address in each machine, the address of the ARP server. (The address of "the ARP server" on ethernet is "broadcast".) Mike Brescia