hahn@tolerant.UUCP (John Hahn) (12/06/89)
I am looking for some information on the Internet Ip-addr to X25
address mapping/conversion issue. I always assumed that in order to
have TCP-IP run on top of X25 the addresses have to be mapped since
Internet and X25 address spaces were incompatible. However when I
was investigating the BSD4.3 implementation on the VAX it looks as if
there is an address conversion based on some DDN spec.
The conversion routine goes as follows.
/* @(#)if_ddn.c 7.1 (Berkeley) 6/5/86 */
Copyright (c) 1985 by Advanced Computer Communications
* *
* NOTE: Although IF-11/X25 was designed to accept ASCII coded *
static boolean convert_ip_addr(ip_addr, x25addr)
struct in_addr ip_addr;
u_char x25addr[];
{
register int temp;
union {
struct in_addr ip;
struct { /* (assumes Class A network number) */
u_char s_net;
u_char s_host;
u_char s_lh;
u_char s_impno;
} imp;
} imp_addr;
if (imp_addr.imp.s_host < 64) /* Physical: 0000 0 IIIHH00 [SS] */
{ /* s_impno -> III, s_host -> HH */
else /* Logical: 0000 1 RRRRR00 [SS] */
{ /* s_host * 256 + s_impno -> RRRRR */
Which then brings up the question if this is useable with the
Public Data Networks (i.e. Telenet, Tymnet, Transpac ..etc)?
Is this only for some DDN private networks and one must resort to
mapping the address for use with the PDN's?
Thanks in advance for those who can enlighten me.news@haddock.ima.isc.com (overhead) (12/07/89)
In article <6539@tolerant.UUCP> hahn@tolerant.UUCP (John Hahn) writes: > >I am looking for some information on the Internet Ip-addr to X25 >address mapping/conversion issue. I always assumed that in order to >have TCP-IP run on top of X25 the addresses have to be mapped since >Internet and X25 address spaces were incompatible. However when I >was investigating the BSD4.3 implementation on the VAX it looks as if >there is an address conversion based on some DDN spec. > "Defense Data Network X.25 Host Interface Specification" Dated December, 1983, prepared by BBN Communications Corporation. Refer to Section A-5 of Appendix A. >Which then brings up the question if this is useable with the >Public Data Networks (i.e. Telenet, Tymnet, Transpac ..etc)? >Is this only for some DDN private networks and one must resort to >mapping the address for use with the PDN's? > Each Public Data Network (and DDN) assigns its own address space. There are no address conversion algorithms that I know of except for the DDN address space. I believe there was a posting a while back about about a group working on an ARP type protocol to obtain X.25 addresses, but I may be wrong about this. Jim
art@salt.acc.com (Art Berggreen) (12/07/89)
In article <6539@tolerant.UUCP> hahn@tolerant.UUCP (John Hahn) writes: > >I am looking for some information on the Internet Ip-addr to X25 >address mapping/conversion issue. I always assumed that in order to >have TCP-IP run on top of X25 the addresses have to be mapped since >Internet and X25 address spaces were incompatible. However when I >was investigating the BSD4.3 implementation on the VAX it looks as if >there is an address conversion based on some DDN spec. >The conversion routine goes as follows. > >/* @(#)if_ddn.c 7.1 (Berkeley) 6/5/86 */ > Copyright (c) 1985 by Advanced Computer Communications . . . >Which then brings up the question if this is useable with the >Public Data Networks (i.e. Telenet, Tymnet, Transpac ..etc)? >Is this only for some DDN private networks and one must resort to >mapping the address for use with the PDN's? > >Thanks in advance for those who can enlighten me. The IP over X.25 world can be split in two groups, nets that know about IP addresses and those that don't. For those nets that know about IP and maintain a correspondence between IP and X.25 addresses (DDN, Blacker I/Fs) the IP<->X.25 mappings are algorithmic. For most of the rest of the X.25 nets in the world there is no relationship between the IP and X.25 addresses and address lookup tables are generally used. The PDN working group of the IETF is looking into defining X.25 address server protocols to avoid maintaining huge tables locally. Art Berggreen ACC
ak2@nvuxr.cc.bellcore.com (Arthur Knapp) (12/07/89)
Article <6539@tolerant.UUCP> hahn@tolerant.UUCP (John Hahn) John, Good question! Address interworking is never pretty. I am not sure what real packet-switches and real (public and private) packet-switched networks are doing but there are standards which may help you now or in the future. In 1984/1988 CCITT X.25 and ISO 8208-1986/1989 include a Address Extension Facility (AEF) parameter field. This field allows a calling DTE to include additional address information. e.g., an OSI Network-layer-address or another subnet address. The AEF contents field is variable length up to 20 octets. Both called and calling address extensions are specified. In RFC 1069, Callon and Braun suggest a NSAP address structure that includes the DoD IP address. Gateways can then strip out the DoD IP address when delivering an incoming PDU. Gateways can add the appropriate X.25 fields for an outgoing PDU. You wrote > Which then brings up the question if this is useable with the > Public Data Networks (i.e. Telenet, Tymnet, Transpac ..etc)? Does anyone know if any PSPDNs or vendors are supporting the AEF field? If so, do you know how many bytes the field is? Arthur Arthur Knapp ak2@nvuxr.cc.bellcore.com Tel: 201-758-2198 Fax: 201-530-6875 331 Newman Springs Road, Rm 1F-359 Red Bank, NJ 07701-7020 USA Telex: 275318