Xref: utzoo comp.protocols.misc:219 comp.protocols.iso:34
Path: utzoo!mnetor!uunet!munnari!mulga!ditmela!george
From: george@ditmela.oz (George michaelson)
Newsgroups: comp.protocols.misc,comp.protocols.iso
Subject: Re: AUSTPAC/TRANSPAC internetwork problems: have you seen this?
Message-ID: <286@ditmela.oz>
Date: 6 Feb 88 02:24:44 GMT
References: <947@cos.COM>
Organization: CSIRO Division of Information Technology
Lines: 60

Further to this saga, AUSTPAC were finally contacted and enabled 
a feature whereby they *DO* pass up the full called DTE in incoming 
CR packets, and also inserted them on outgoing CC and CR.

However there remained a small snag. They pass in a DTE with a 
leading 0 thus generating 15 digit DTE's... and the sun being called 
can only declare itself to be a 14 digit address. This can be 
circumvented by using 1 digit subaddress routing but I regard that 
as a big kludge. 

AUSTPAC may be legally ok in adding the 0 but surely the DNIC identifies 
external routing directly, and thus guarantees an address can be resolved 
as net-internal or X.75 routed. Why do they do this?

How many programs out there assume the first 4 digits are DNIC?

To get round this we declared the sun as having a NULL DTE (which is a
documented feature for TRANSPAC like networks), and rely on the switch to
correctly route processes into the host. To separate out X25 applications
(such as FTAM and our ISODE process) we can declare any DTE  we like from
homebrew or sourcecode available programs. Thus there is a limit of 9 
identities (subaddress 0 being dubious) per host but the machine would die 
before we reached that anyhow. 

Don't ask why PID masks or CUDF don't work, the switch and the sun 
between them cannot agree on what to do there. The switch can't even 
*specify* the  PID field of CUDF. The sun should be able to route calls
on CUDF and should NOT pass X.29 to X.25 listeners. I think it's broken.

Further the sun supplied pad program and other utilities make use 
of an ioctl (on the X.25 socket they open) to read the local DTE 
(from a config file) for assertion in outgoing calls. Thus the 
machine can have only a SINGLE declared DTE for all applications, 
and cannot be dual-ported into two different address spaces. 

The latter is a major headache for users of IPSS and JANET in the UK 
but could cause problems for sites using a local X25 switch with 
local address space as well as direct X25 connections to the outside 
world from some hosts.

The switch is certainly broken.  Enabling local DTE masking 
(where it fakes a given DTE on all outgoing calls taking only their 
subaddress where given) causes the incorrect DTE to be changed in call 
accept packets, it is unable to explicitly modify *as different objects* 
ALL addresses in ALL packets passed in either direction. it cannot route
on PID. 

I received a local followup (from within australia that is) suggesting 
others have seen this problem. That one was involving DATAPAC (canada?) 
and was solved quite quickly.

Do all networks ending in -PAC derive from common code? AUSTPAC is
TRANSPAC derived.

	it would seem we still have a wee way to go with X25.

-- 
ACSnet:	G.Michaelson@ditmela.oz.au
Postal:	55 Barry St, Carlton, Vic 3053
Phone:	(03) 347 8644 				Fax:	(03) 347 8987