Differences between Recommendation X.223 and ISO 8878
The following differences exist between Recommendation X.223 and
ISO 8878.
IV.1 In Recommendation X.223, the text in 6.2.2.1.1 specifies that given
conditions a) through d), the address is always carried in the Address Field (AF).
ISO 8878 specifies that given conditions a) through c) (ISO 8878 does not include
condition d), the address may optionally be carried in the AF.
IV.2 In Recommendation X.223, the text in 6.2.4 specifies that if "no use of
Expedited Data" is indicated or if the NL entity cannot support 32-octet INTERRUPT
packets, then the EDN facility is always omitted. For the same case, ISO 8878
specifies that the EDN facility either may be carried specifying "no use of
Expedited Data", or may be omitted.
IV.3 In 6.2.5.1 (Throughput QOS Parameters) of Recommendation X.223, two new
paragraphs have been added which are not present in ISO 8878. These paragraphs are
the last paragraph in 6.2.5.1.1, and the last paragraph in 6.2.5.1.2.
Collectively, these paragraphs specify that whenever the Lowest Quality
Acceptable sub-parameters of the Throughput QOS Parameters for both directions are
"unspecified" in the N-CONNECT request, the MTCN facility is not included in the
CALL REQUEST packet. ISO 8878 specifies that in such a case, the MTCN facility is
encoded as 75 bits per second.
IV.4 In 6.2.5.2 (Transit Delay QOS Parameter) of Recommendation X.223, four
new paragraphs have been added which are not present in ISO 8878. These paragraphs
are the last paragraph in 6.2.5.2.1, the last paragraph in 6.2.5.2.2, the last
paragraph in 6.2.5.2.3, and the last paragraph in 6.2.5.2.4.
Collectively, these paragraphs specify that whenever the Target and Lowest
Quality Acceptable sub-parameters of the Transit Delay QOS Parameter are
"unspecified" in the N-CONNECT request, the EETDN facility is not included in the
CALL REQUEST packet. ISO 8878 does not explicitly address such a case, and
actually implicitly invalidates it per the conditions in items a) -d).
Additionally, in 6.2.5.2.1 of Recommendation X.223, the last sentence in
item d) specifies that in DTE-to-DTE operational environments the usage of the
TDSAI facility is for further study. ISO 8878 does not have such a sentence.
IV.5 In 6.2.5.2.1 of Recommendation X.223, there is only one note after item
d). ISO 8878 contains two notes after item d), the first of which is identical to
the one note in X.223. ISO has initiated the necessary procedures to remove their
second note.
IV.6 The scope of Recommendation X.223 does not include for provision of the
OSI Connection-mode Network Service over 1980 X.25 sub-networks. Conversely,
ISO 8878 provides for this and defines a protocol mechanism in Annex A. Also,
material related to conformance issues, including those raised by the presence of
Annex A, is included in Annex B to ISO 8878 and is not included in this
Recommendation.
