Path: utzoo!dptcdc!jarvis.csri.toronto.edu!mailrus!csd4.milw.wisc.edu!bionet!ames!oliveb!sun!batcomfs!rja
From: rja%batcomfs@Sun.COM (Robert Allen)
Newsgroups: comp.protocols.tcp-ip
Subject: DDN X.25 question.
Keywords: 1984 X.25 incompatible?
Message-ID: <99491@sun.Eng.Sun.COM>
Date: 17 Apr 89 22:14:42 GMT
Sender: news@sun.Eng.Sun.COM
Lines: 34


    I'm working on adding some 1984 X.25 features to a 1980 X.25 implementation
    and I have a question about the facilites required by DDN X.25, as
    specified in the DDN X.25 spec. in Vol. 1 of the DDN Protocol Handbook.

    In section 2.1.2, it is noted that two facilities, type-of-service and
    call precedence, should be included *after* all CCITT X.25 facilities and
    must be preceded by a two byte facility marker, where each byte is of
    zero value.

    The type and location of the facility marker is counter to what is 
    documented in DIS 8208 "Info. Processing Systems - X.25 packet level
    protocol for data terminal equipment", which states that:
    
	(1) all CCITT specified facilities must come *after* "non-X.25
	facilities supported by the network...of the calling DTE...",
	which is what the DDN facilities are based on the facilities marker
	used to denote them.

	(2) that the facilites marker for X.25 specific facilities (which
	happens to be two zero bytes) must come BEFORE the CCITT facilites
	marker,

    If, as the DDN X.25 spec states, the DDN X.25 facilities must come after
    the CCITT facilities, *and* must use two zero bytes as the facilities
    marker of two zero bytes, then the two protocols, DDN X.25 and 1984 X.25,
    seem to not be compatible.  Is this correct?  If not, what am I mis-
    understanding here?

    Thanks in advance,

Robert Allen		"I'm the NRA" (and soon the ACLU too.)
rallen@sun.com		"Just say NO to the loss all our civil liberties."
Disclaimer: The opinions expressed are mine [so keep your hands off :-) ]