UCL Telex number - "40" or "54" in NSAP

[Christian Huitema <[e-mail]>]

Pointing my nose out of the short names rat-hole, I just picked an ennoying
defect in the "interim NSAP encoding format" specified by Steve in RFC-1277.

It contains tables explaining the various formats, e.g.
______________________________________
|Part___|_______IDP__________|________
|Comp___|__AFI__|___IDI______|Prefix_| ...
|Octet__|_______|____________|_1-2___|_...
|Value__|_Telex_|007_28722___|__02___|_...
|Ct_Dec_|__54___|007_28722___|__02___|_...
|Ct_Bin_|__54___|00_72_87_22_|__02___|_...

In this, the Telex number of UCL is described as telex country code 7 (UK
or GB) + value 728722, padded with two non significant leading zeros. The
first two digits of the NSAP, the AFI, have the value 54, which described a
Telex based NSAP, with a decimal DSP.

In order to align our environment with the RFC, we have programmed here a
syntax parser for RFC-1278. The problem is that, if we enter an NSAP as 

	TELEX+728722

what we obtain is NOT "54000728722", but rather "40000728722", i.e. using
the AFI "40" instead of "54". This is consistent with ISO-8348 add 2, which
specifies in paragraph 8.2.1.2:

	....Two AFI values are associated with each combination that
	involves a variable length encoding..... The numerically lower 
	AFI value is used when the first significant digit in the IDI
	is nonzero. The numerically greater AFI value is used when the 
	first significant digit in the IDI is zero.

The two values assigned for Telex IDI + digital DSP in ISO-8348 add 2 are
"40" and "54". All occurences of AFI=54 in RFC-1277 are erroneous. They
should be replaced by AFI=40.

Christian Huitema